Ambivalent Engineer

Geothermal is not renewable

2012-01-03T08:49:00.000-08:00

You can group geothermal plants into two types:

The kind that pump water underground and take steam or hot high pressure water out.
The kind that drill holes in the ground and use conduction to get heat out.

Admittedly, I don't know a great deal about geothermal systems, but I do understand heat flow reasonably well. And geothermal systems are all about heat flow. Here are the problems that I see:

Conduction is an impractical way to move utility-scale amounts of heat through anything but the thin walls of a heat exchanger. For instance, ground temperatures typically rise about 3 C for every 100 meters you go underground. Ground conductivity is about 1.5 watts/meter/kelvin. Multiply those two and get 45 kW/km^2. Remember that utility-scale power means you need hundreds of megawatts of heat. Bottom line: geothermal isn't renewable. It works by cooling down some chunk of rock in place, rather than by converting heat that rises from the earth's core.

You might think that a big hunk of rock can provide a lot of heat for a very long time. For instance, a cubic kilometer of granite, cooling 30 C, provides 2 gigawatt-years of heat. Figure 20% of that gets converted to electricity. Over 30 years, that cubic kilometer of granite will run a 13 megawatt power plant. We're going to need dozens of cubic kilometers.

You might think that dozens of cubic kilometers would be cheap. Ranch land out in Idaho goes for $360,000/km^2. Assuming you can suck the heat out of a vertical kilometer of rock, the 13 megawatts from that ground are going to bring you a present value of $90 million. Sounds great!

But wait... before you get started, you are going to have to shatter that cubic kilometer of rock so you can pump water through it to pick up the heat. The hydrofracking folks have learned quite a lot about getting fluid out of tight underground formations. I think the useful comparison to make is the value of the fluid extracted. Oil is worth $100/barrel right now, which is $850/m^3. Water from which we will extract 30 C of heat to make electricity at 4 cents a kilowatt-hour at 20% efficiency is worth 28 cents/m^3, ignoring the cost of capital to convert the heat to electricity. There is a factor of 3000 difference in the value of that fluid. Now hydrofracking rocks for heat doesn't have to be as thorough as hydrofracking them for oil, since you can count on ground conduction to do some work for you. But I don't think the difference is going to save a factor of 3000 in the fracking cost.

So, that means geothermal is going to be confined to places where the rock is already porous enough to pump water through. Like the Geysers in Northern California, which is a set of successful gigawatt geothermal plants. I think it's interesting that the output has been declining since 1987.

The problem is thought to be partial depletion of the local aquifer that supplies the steam, because steam temperatures have gone up as steam pressures have dropped. This sounds right to me, but I'll point out that the water in the aquifer is probably sitting in a zone of relatively cool rock which has hotter rock above it. As the aquifer has drained, the steam has to travel through more rock, causing more pressure drop, and thus less steam transport. Where water used to contact rock, steam does now, pulling less heat from the rock, so that the rock face heats up from conduction from hotter impermeable areas.

Wait... how did cool rock end up under hotter rock? The 150 or so gigawatt-years of heat that have been pulled out of the 78 km^2 area over the last 50 years have probably cooled a kilometer stack of rock by about 30 C (or maybe a thinner layer of rock by a larger temperature swing). I'm not at all convinced by the USGS claim that the heat source is the magma chamber 7km down. Assuming the magma surface is at 1250 C (the melting point of granite) and the permeable greywacke is at 230 C, a 78 km^2 area 6 km thick will conduct about 20 megawatts, an insignificant fraction of the energy being taken out.

Refilling the aquifer will help pull heat out of the shallower rock, but that's not going to last decades. To keep going longer they'll need to pull heat from deeper rock, and that's going to require hydrofracking the deeper greywacke.

And that's expensive.

Wicked

2011-07-26T11:43:00.000-07:00

Just read "Wicked: the Life and Times of the Wicked Witch of the West". This after we saw Wicked in London as part of our summer Europe trip. My cousin Christopher plays the drums and various other percussion pieces in that production.

The musical is a blast. We had great seats, the music and singing were fabulous, the staging sometimes overwhelming, the kids loved it, Chris showed us around a little bit... what fun.

When we got back, we got the music, and now the kids have mostly memorized all the songs. It's slightly disturbing seeing my 4 year old singing "No one mourns the wicked".

Martha got the book out of the library, and we both read it. Like all tragedies, it's frustrating. It's a vastly more complex and subtle story than the musical. If you're reading this but haven't read the book or seen the musical, see the musical first, as it'll be tough to enjoy after the book. And don't read the rest of this post.

SPOILERS.

Like most things that I really like, I wanted the book to be better. In particular, a good tragedy should make me feel the inertia of doom, the sense that the characters are carrying themselves towards their downfall. In the book, there was definitely some of that, but I also got the feeling that doom was coming in the form of spunky little Dorothy Gale, and that the characters were bending their wills to the needs of that other story arc. So that wasn't as impressive. And why the hell couldn't a smart girl like Elphaba convert the tactical (and unsuspected) advantage of being able to fly on a broom into a way to pick off the wizard and his chief lieutenants.

The part that I really liked was how Elphaba's desire to do good was a significant part of what drove her to her doom. I find myself strongly agreeing with the idea that the desire to do good is not good in itself, and can actually lead to evil. If you want to be good you have to actually *do* it.

But there were so many things to love about the book. The dialog, the political machinations, tictocism, Elphaba's reaction to Dorothy asking for the forgiveness that Elphaba herself had been denied... I love reading an author who has insights way past my own.

Ouch

2011-02-17T18:38:00.000-08:00

Ed Lu gave a talk at Google today on his B612 foundation.

He mentioned that the asteroid that caused the K-T extinction was probably 10 miles in diameter, um hummm.... which meant that the top had not yet entered the bulk of the atmosphere when the bottom hit the ocean. That image really got me.

The speed of sound through granite is 5950 m/s, which is substantially less than the speed of an incoming asteroid. Things in low earth orbit go at about 7800 m/s, and Ed said incoming asteroids are around 3-4 times that. So that means that when the asteroid smacks into the earth, there is a really good chance that the back of the asteroid will hit the earth before the shock wave gets to it -- it'll punch all the way into the Earth surface. Koeberl and MacLeod have a nice table here which shows a granite on ice impact needs only 6 km/s vertical velocity to punch all the way in (they neglected water as a target material, an odd oversight since the majority of the earth is covered in water, more or less a solid at these velocities). If the incoming velocity is 25 km/s, which is on the low side of what Ed suggested, then anything striking within 76 degrees of vertical is going all the way in. It seems to me that most impacts would be like that.

So after the impact, most of the energy is added to stuff below the ground surface. That's 1e25 joules for the K-T asteroid. Enough to melt 5e18 kg of rock, which is 100 times as much mass as the asteroid itself. Figure a small fraction of that will vaporize and the whole mess goes suborbital.

For the next hour you have thousands of trillions of tons of glowing molten lava raining down on everything. Everything that can burn (6e14 kg of carbon in the world's biomass) does so, promptly.

And this asteroid impact thing has actually happened, many times. As Ed says, it's like pushing Ctrl-Alt-Del on the whole world.

Side notes: There is 1e18 kg of oxygen in the atmosphere, far more than necessary to burn every scrap of biomass on earth. The story I read was that the oxygen in the atmosphere came from plants. If so, there must be a lot of carbon buried somewhere: 8.6e14 kg of known coal reserves are less than 1%.

Another interesting point, vis-a-vis ocean fertilization: there is about as much carbon in the atmosphere as in the world's biomass. We'd have to boost the productivity of 1/10 of the world's ocean by a factor of 8, from existing productivity (125 gC/m^2/year), to fix the CO2 problem in the atmosphere in 15 years. Ocean CO2 would take a century or more. That productivity boost is like converting that much ocean into a coral reef! This seems like a lot to me.

Do powerplants use too much water?

2010-10-01T11:35:00.001-07:00

Coal and nuclear powerplants make heat, convert some of that to electriciy, and reject the rest. They use water, and lots of it, to reject the heat.

The USGS says that thermoelectric powerplants (nearly all coal and nuclear) use 49% of the water withdrawn in the US. That sounds like a lot, and it is. It's also misleading.

92% of the water used by powerplants is used for once-through cooling. That means they suck water from the river, use it to cool their condensers, then pump it back the river at somewhat higher temperature. There are legal limits to the temperature they can send back out, and as the intake water temperature rises closer to those limits, they have to pump more water, and eventually shut down the powerplant. This has happened, famously, in France during a heat wave, right when everyone wanted to run their air conditioners.

The other 8% of the water used by powerplants is used in recirculating cooling. In these systems water is used to cool the condensers, but then some of that water is evaporated in those familiar hyperbolic cooling towers, which cools the rest, and the water is cycled around. These systems use a lot less water because they only need to make up the water that evaporates. Of that 8%, about 70% is evaporated and 30% returned to the lake or river it came from.

Since 1990, the US has mostly built gas-turbine powerplants. These reject heat in the form of incredibly hot jet exhaust, and don't need water. But they burn natural gas which has caused us to send our plastics industry to China. I don't think many people appreciate how dumb that was.

New nuclear plants in the US will be either on the coastline or evaporatively cooled, because there is no appetite for increasing the amount of once-through freshwater cooling. If these plants cause coal plants to shut down, and if the water rights for those coal plants can be transferred to the new nuclear plants, then there should be plenty of water for new nukes, and the amount of heat deposited in rivers can actually go down. But if there are difficulties with transferring water rights, it will be harder to build new nukes. My guess is that when the nukes are not built at the same place where the coal plant once was, water rights will be hard to secure.

Water rights are one reason why I'm so interested in molten salt reactors. MSR cores and turbines run at higher temperatures than those of pressurized water reactor cores, so they can be air cooled without killing their efficiency (and thus jacking up their costs a lot). Air cooling is a good thing because it removes an entire class of regulatory problems, and thus an entire kind of project risk.

Deep Ocean O2 Used by Gulf Oil Spill

2010-08-18T00:43:00.000-07:00

About 150 million gallons of oil have spilled into the Gulf. Estimates vary, but something like 50 to 100 million gallons of that oil are now dispersed into the water. Bacteria are supposed to "break down" that oil. What does that mean?

It means they will oxidize the oil. On average, oil has two hydrogen atoms to one carbon atom. CH2 + 1.5O2 => CO2 + H2O, so consuming 14 grams of oil requires 48 grams of oxygen. So, that means that consuming e.g. 50 million gallons of oil requires 150,000 metric tons of oxygen.

The oxygen concentration of the sea is around 7 mg/kg. So, 150,000 metric tons of oxygen is all the oxygen in 22 cubic kilometers of seawater. 22 cubic kilometers in the Gulf of Mexico is approximately one drop in a 5 gallon bucket.

Bottom line: there is plenty of oxygen, even at depth, to oxidize all the oil spilled.

Lanthanum Phosphate

2010-07-05T22:41:00.000-07:00

As you know, I've built this nice new pool. The pool is designed to stay at 85 F for most of the year, and so it has solar panels in their own insulated glass boxes so that it can collect heat even when the outside air temperature is low. Because those panels can get ridiculously hot (338 F) in the sun when water is not flowing through them, they are made of copper rather than plastic as is more commonly done. I've been learning the consequences of that difference.

A couple weeks after filling the pool I added chlorine (hypochlorous acid, HClO), which immediately caused a brown stain on my nice white plaster pool. Copper from the panels had leached into the pool water in the form of copper ions. The HClO oxidized those ions, probably to Cu2O, which promptly came out of solution and bound to the plaster. So, now I have a brown pool. It really pissed me off for a while, but I've grown used to the look and now I actually think it looks good in some places. One of the interesting side effects of having all this copper in the water is that the copper is antimicrobial. The pool has often gone for days with zero chlorine, at 92 F, and with tons of phosphate, and has essentially no algae growth. Without copper that would be a recipe for an algae bloom.

I have these little strips that claim to test the copper content of the water, and that test result drops to zero shortly after I add chlorine. After four or five days it will bounce back up to 0.5 ppm (ppm meaning mg/liter in this case). That means my 38500 gallon pool has 2.5 ounces of copper in it that used to be on the roof. Clearly I can't go on like this for too long, or I'm going to have pinhole leaks in the roof panels. Happily, I've noticed recently that the copper seems to be zero even after a few days of no chlorine, and if this is real, it means the copper has stopped leaching into the water, perhaps because I now have a protective patina on the interior of the pipes.

In my various attempts to keep my white plaster white, I added "chelating agents" to the pool. These things are basically dish soap, and load the water with lots of phosphate (HPO4 2-). The idea is that the phosphate ion will preferentially bind to the copper ions and form Cu3(PO4)2, which is insoluble in water. Presumably this copper phosphate doesn't bind to the plaster but instead can be filtered out. In combination with a low pH this was supposed to reduce the Cu2O in the plaster, then convert it to Cu3(PO4)2, but if that was happening it sure wasn't obvious. I eventually gave up. This exercise left the pool with over 2500 ppb phosphate, which is way too high. When the copper levels recently stopped going up without chlorine, an interesting thing happened: algae! So this weekend I determined that it was time to take out that phosphate.

One takes out phosphate by adding Lanthanum Chloride. This reacts with the phosphate to make LaPO4, which immediately comes out of solution and forms this white fluffy stuff on the bottom of the pool. I tried vacuuming this up -- big mistake. The stuff will plug any filter, instantly. I tried a few times adding lots of DE to the filter, and gave up. That's when I read online that you have to vacuum this stuff out of your pool entirely, just dumping the water to the street. Then I realized I hadn't really plumbed my pool with an option to vacuum to waste. D'oh!

[Update: fixed the plumbing so I can now pump to the street or sewer. Since I have very low-resistance pipes, it looks like I can pump over 80 gallons/minute to the street, which is very impressive to see.]

For a little while I was feeling pretty beaten. The phosphate levels weren't reading any lower, the pool was a mess, I had no plan to get it clean, and my fingernails were gone from cleaning the DE out of the backwash tank. This Lanthanum Phosphate is amazing -- a tiny amount turns DE into a watertight membrane, something like Bentonite clay.

Then I got back to work. I pumped the water out of the spa, then set the valves to bypass both the filter and backwash tank, suck from the pool and return to the spa. With my vacuum in place I was vacuuming the pool into the spa. Before turning on the pump I put a sump pump in the spa and pumped it out into a hose which went to the sewer. Yes, this was pumping phosphates into the city's sewer. I think I pumped out about 2.5 pounds of phosphate, or about one box of dishwashing detergent. I had no copper in the water, nor any chlorine, and my pH was 7.5. It shouldn't be a problem for anything downstream. The vacuum sucked everything off the bottom and we dumped about 800 gallons of water, or $2.40. Even better, my phosphate is now down to 300 ppb, which isn't perfect but it's nice to be out of the unmeasurable range.

In doing the research for this blog post I found out that my tap water already has around 190 ppb phosphate in it, added by Los Altos to control corrosion in copper pipes. So, I need to measure my copper levels now that I have low phosphate to see if I'm back into corroding my solar panels. Hopefully something else is protecting the panels.

Also, I've learned that the patina that can protect copper is soluble in ammonium salts. That's significant because ammonia in the pool is what you measure when you measure "combined chlorine" (really chloramines). It seems I'm going to have to stay on top of that, not just because chloramines are smelly eye irritants, but because the stuff attacks my panels.

I can keep after it with adding chlorine, but my main line of defense was supposed to be a nightly dose of ozone, intended to burn anything organic down to N2, CO2, and water. The ozone is on hold until I can re-cover my DE filter grids in stainless steel mesh, instead of the polypropylene mesh they have now. Meh. More work. Some other weekend.

[Update: stainless steel mesh won't hold diatomaceous earth. I got some mesh samples and tried pouring DE mud on them, and it fell right through. Under the microscope, it's clear that DE grains are just tens of microns across, and so a macroscoping mesh isn't going to do it.

I've read that glass is compatible with ozone, so I'm going to try fiberglass as a filter material to hold the DE, and we'll see how that goes.]

[Update2: BGF fiberglass filter fabric style 421 style 580 holds diatomaceous earth just fine. I had to hand sew it with stainless steel wire, since fiberglass strands are completely useless for sewing, as they fray and break at the slightest provocation. Next up: long term test of fiberglass grid covering to see if it breaks or does some other bad thing.]

A Great Day

2010-05-02T20:24:00.001-07:00

Today my dad and I took my daughter Anya to an event hosted by the UC Berkeley Nuclear Engineering group. I got my BA at Berkeley, and my dad was a post-doc there in what was then called the Nuclear Chemistry group. It was great fun showing Anya around a small portion of the campus where I spent nearly seven years.

We started with lunch and about half an hour of Frisbee on Memorial Glade. After that, Anya (7 years old) spent three consecutive hours in 6 classrooms listening to and participating in discussion and demonstrations about radioactivity and nuclear power.

Anya spent probably 20 minutes of that wriggling around in her seat and the rest of the time she was engaged. The presentations were perfect for someone her age. The students doing the presentations were energetic and interesting. We got to see the old reactor room in Etcheverry Hall which now houses a bunch of interesting experiments. I got to meet a bunch of other parents, and it was fabulous to talk with other people who don't freak out when they discover that every home's smoke detector has a little bit of Americium-241 which sends the Geiger counter up several orders of magnitude once you get it close enough that the air isn't shielding it. (Pop - pop - pop - bzzzzzzzeeeeeeee)

Afterwards Anya and I walked around campus some more, watched some students learning to walk on a tightrope, and then went out to dinner together at Zachary's Pizza. For most of the hour long drive home we talked about how to design an "earth-friendly" town -- things like arranging the houses around a central area for the kids to plan in, building at the edge of but not in a forest, etc.

So, basically, I had a perfect day.

Pumping pool water

2010-03-29T01:35:00.000-07:00

I've been looking into the costs of pumping water through the filters and valves and pipe work around the pool, and it's quite interesting. For context, you need to understand that we live in California, in the San Francisco Bay Area (known to our utility PG&E as area X). That means that we're going to be using the pool 9 months a year, and the marginal electricity we'll be using for the pool will cost us $0.424 to $0.497 per kilowatt-hour (Those are the charges for >24.2 kWh/day and >36.3 kWh/day). That sounds like a lot of money, and it's going to sound worse as you read below.

In 1997, marginal electricity with a basic residential rate was $0.122/kWh, so the average cost growth since then is 10.0% per year. That's substantially faster than the discount rate of 6% per year that I usually apply to future money. If the cost growth of energy exceeds the discount rate into the future, it means that the energy I spend to pump pool water 10 years from now will cost more in current dollars than the energy I spend today.

You can't extrapolate a growth curve indefinitely into the future, and the price of electricity in current dollars cannot rise without limit. That said, I'm fairly confident that over the next 40 years the price of electricity will at least keep up with a 6% discount rate. That means that I'm predicting that the electricity the pumps burn 40 years from now costs me just as much, today, as the electricity that the pumps burn today.

I want to compare the costs of running the pool with the cost of building it, so I can make decisions about what sort of equipment to install. In the face of electricity that does not discount into the future, I have to put some sort of time limit on how long the pool will be operated. I'm going to pick 40 years. At that point my grandkids are likely to have learned to swim, and there is an about even chance that I'll be dead and won't have to worry about money any more. Over 40 years (9 months a year), each kilowatt-hour burned, per day, costs a total of $4643 in 2010 dollars. The bottom line is that, had I built my new pool in a standard fashion, the electricity to run it would have cost over $150,000 in present value. That's more than the pool! Instead, I've spent a few thousand dollars improving the efficiency of the plumbing so that my projected present value cost is more like $40,000 (which can be improved further).

Those of you with astronomical electricity bills, and pools, may be wondering, how did I do that?

Let's get started with a simple result that is relatively new for the residential pool industry: slower is better. If I run a pump at 42 GPM for 16 hours, it'll turn over about 40,000 gallons. If, instead, I run the pump at 84 GPM for 8 hours, it'll move the same number of gallons. However, and this is really important, the pump has to push about twice as hard to move water twice as fast. Power is pressure times flow, so pumping twice as much water up twice the pressure head takes 4 times as much flow power. 4x the power in half the time is 2x the energy, and energy is what you pay for. Bottom line: slow the pump down.

You should also get the most efficient pump possible. If you don't have solar and so don't need variable head, and can mount the pump below the level of the water surface, then get something like a Sequence 5100. Otherwise get an Intelliflow 4x160, which is what I got.

Slower-is-better isn't the complete answer, because of variable pump efficiency and in-line spring-loaded valves. So most pools won't run their pumps 24 hours a day, as I do.

Note that I talked about flow power in the paragraph above. Flow power is pressure (e.g. psi) times gallons per minute. Try it. Most pumps turn electricity into flow power with an efficiency that varies between 15 and 50%. 15% is the efficiency at low speeds (right before the pump stalls and efficiency goes to zero), and 50% is the efficiency at something near top speed. Variable-speed pumps, like the Intelliflow 4x160, usually hit their maximum efficiency at high RPM settings and high flow rates (but I include a counterexample in my spreadsheet link below). As a result, when you run the pump more slowly, less energy is required to move the water, but the pump takes more electricity to produce each joule of flow energy. You can see the pump power and head curves for the 4x160 on page 47 of the user's manual. And I've extracted the numbers off the chart and done efficiency calculations here. Bottom line: best efficiency is at 30 GPM for a normal pool. I'll be forced up to 42 GPM (at a measured 31% efficiency) because the pool is big.

The analysis gets a little complicated because most pools have in-line spring loaded valves, which should be banned. Many solar installations suggest a check valve between the filter and the water line going up to the roof, because the panels drain at the end of the day and you don't want those panels draining backward, through your filter, taking all the scum in there back out through your skimmer. An innocuous little check valve seems like just the ticket. One wrinkle is that the check valve requires something like 1 psi to open, and since the flow is working against that spring, there is a 1 psi drop across the valve at all flow rates. Another wrinkle: yet another spring-loaded valve, in the heater this time, which drops about 5 psi. I'll get to that later.

1 psi doesn't seem like much until you consider that 40,000 gallons pushed through 1 psi at 31% efficiency is 0.935 kilowatt hours. Still not much? The present value is $4343. It's actually a bit worse than that because the constant pressure drop causes the pump to stall at very low speeds, which changes the best operation point to something faster and thus even less efficient.

My last pool (not my design) ran the pump at about 35 psi. As I said, the present value of each psi is $4343, so if this pump had to do the same thing, the present value would be $150,000. That number is so large that you are thinking that it is funny money. It's not. That is this year's electric bill for $3800, and next year's bill for $4000, and the year after's bill for $4200, and so on. It's committed money: if I turn off the pump, the pool turns into a pond and the City folks come by and suggest how to abate mosquitoes. How did I end up with this problem?

Pool equipment is generally designed for low equipment cost, not low energy cost, because the equipment cost is what most homeowners look at. But when we look at cost of energy to drive this equipment, it becomes clear that most pool equipment design is completely insane. The details will come in following blog posts, but in short:

Part	Cost	Pressure drop @ 42 GPM	Power cost	Alternative	Cost	Pressure drop @ 42 GPM	Power cost
Rooftop pressure relief to drain solar panels	$50	8.6 psi for 2-story house	$37,400	Extra 3-port valve and parallel drain to pool	$400	0.1 psi	$430
Gas heater with internal spring-loaded valves (check page 9)	$1800	5 psi	$21,700	Bypass heater with 3" 3-port valve and an actuator	$2050	0.1 psi	$400
DE filter with multiport valve (check page 8)	$700	4 psi	$17,400	DE filter with 2 3-port valves and ozonator	$2100	1 psi	$4,300
100 feet of 2" pipe	$60	1.19 psi	$5,170	100 feet of 3" pipe	$110	0.173 psi	$751
2" check valve	$45	1 psi	$4,300	3" 2-port valve with actuator	$250	0.1 psi	$430
2" 3-port valve	$45	0.5 psi	$2,200	3" 3-port valve	$90	0.1 psi	$430

I've implemented all but one of these on my pool, and it works: I can pump 14 gallons/minute (nearly twice what is required) up through solar panels on my two-story house with 9.5 psi from the pump, and I can pump 40 gallons a minute through the filter at 6 psi. With a fix to bypass the heater (I didn't see that one ahead of time), the pressure drop from circulating water through the solar panels should come down to 5 psi or so.

If you work at Hayward or Pentair and you are wondering how you might fix up your product line to make it more attractive, let me make the following suggestions:

A $1500 variable-frequency pump with a proper volute, achieving 80% efficiency when operating at 30 gallons/minute and a 5 psi would be a game changer, as it would cut most pool owners' electric bills in half. It would require 3" ports. Please make the main shaft seal ozone compatible.
Rewrite your manuals to show pool installers how to use 3-port valves to bypass the heater and drain solar panels without spring-loaded pressure relief or check valves. I'll have diagrams for this on my blog shortly.
A DE filter to go with that snazzy pump, with 3" ports and a valve system with less than 1 psi total drop when clean at 40 gpm. Make the grids ozone-compatible (stainless steel?), and figure out a way to either send the separated air back to the ozone generator or through a catalyst to break down the ozone and nitrogen oxides.
Introduce or work with Del to produce an ozone generator which has the ozone passively sucked into the intake of the main pump. Alternatively, figure out how to make a low power air pump that forces the ozone into the high pressure water stream after the filter. The current Del air pump is far too power hungry.
3" sweep 90 degree and 45 degree elbows, with interiors matched to PVC schedule 40 IDs. There is a trick where you twist the flow as it goes through the corner which might improve losses a bit.
3" valves with smooth interior bores. This could be the breakthrough that gets people to take you as seriously as Jandy. The gussets on the valve door interiors now save tens of cents of plastic and cost homeowners hundreds of dollars.
Since all the big pipework and valves will take up a lot of space, pay careful attention to how all the bits fit together into the space allowed for existing pool equipment pads. Maybe a replacement for the multi-port valve which is made of 3-inch Jandy-type valves would work.
Fix the pool control systems so that a basic control box:

can handle 10 valves,
connects to (and comes with) a flow meter that works down to 10 gpm,
and has thermistor inputs for solar return as well as intake water, so you can calculate how many BTUs are coming off the roof.

I think that's enough for now. I've been tweaking this post for 10 months, it's time to post!

Pool is filled

2010-03-13T15:45:00.001-08:00

Thursday was a big day for all of us. Any passers-by seeing the girls running around in bathing suits for a few days now may have guessed the reason: we plastered and then filled the swimming pool.

Good, Bad, and Ugly

2010-03-01T15:53:00.000-08:00

The Good:
I just made myself a goat cheese and apple omelette. Yum! Could have use just a little red onion, and the apple chunks were too large. I will definitely get that right next time.

The Bad:
SolidWorks is crashing on me about every 30 minutes right now. This is not helping me get ready for my presentation tomorrow.

The Ugly:
My eyes. I have red eye, which has all kinds of consequences. Like, getting to stay at home and make myself omelettes. Like, not being able to read small text anymore (should be temporary -- being even slightly blind would truly suck). Like, not being able to make my presentation tomorrow. I sure hope my boss does a decent job.

Bill Gates nails it

2010-02-21T19:50:00.000-08:00

http://www.huffingtonpost.com/bill-gates/why-we-need-innovation-no_b_430699.html

His essential argument is:

We have some agreement on two goals: 30% reduction of CO2 output by 2025, 80% reduction by 2050.
Some countries will not make much reduction, and some countries, like China and India, will expand their CO2 output quite a bit as their huge populations pass through their own industrial revolution.
Some portions of our western economies will not reduce their CO2 output easily. (I think this is a minor point.)
The former goal might be achieved through conservation and improved efficiency.
The latter goal requires that CO2 output from two sectors, transportation and electricity generation, be reduced to zero. Still more will be required, but this is a baseline.
Once transport and electricity have been reduced to zero CO2 output, conservation in these areas will not improve our CO2 outputs. This is, for instance, why France doesn't bother subsidizing more efficient electric appliances, as many other countries do -- France's electricity is close to zero CO2, so improved electric efficiency doesn't reduce CO2 emissions.
Therefore, reworking the economy to reduce transportation and electric consumption does not help towards the 2050 goal. To the extent that it costs money that could otherwise be spent on zero-CO2 electricity and transport, it frustrates progress towards the 2050 goal.

So, what does it take to get to zero CO2 from electricity and transport by 2050? These two subgoals are tied together: transport must be electrified.

Our transport sector currently burns 146 billion gallons of gasoline and diesel every year. In 2050, assuming an increase of 2%/year in transport miles and a fleet efficiency increase from 17 to 23 MPG, it will consume the equivalent of 248 billion gallons of petroleum. If we replace those vehicles with electric vehicles getting 3 km/kWh, those vehicles will consume 3 billion megawatt hours per year. The Nissan Leaf gets 5 km/kWh, so I think an estimate of 3 km/kWh average may be reasonable.

So, the big question raised by Gates' insight is, what can deliver energy like that? To my mind, there are two contenders, wind and nuclear.

The first problem is generation. And the second problem is storage, to cover variations in production as well as consumption.

Here is the generation problem:

The US consumed an average of 470 gigawatts in 2008. The EIA predicts annual increases of 2%/year, so that the average might be 1038 gigawatts in 2050, for the same uses we have today.

The additional 3 billion kWh per year needed to run the electric car fleet, if spread evenly through the year, amounts to 350 GW, which isn't really so bad when thought of in the context of total electric generation. So the grid in 2050 will have to deliver an average of 1400 GW.

1400 average gigawatts could come from 1 million 5 megawatt wind turbines spread over 1.2 million km^2 (at 1.2 watts/m^2). Right now, the US has 1.75 million km^2 of cultivated cropland, so switching US electricity and transport to wind would require a wind farming sector nearly as physically large as our crop farming sector. This is conceivable. After all, 150 years ago most farms had a wind turbine for pumping water. However, 150 years ago that turbine was not the majority of the capital on the farm. These new turbines will cost about $5000/acre, compared with the $2100/acre that farm real estate is currently worth. From an economic standpoint, wind farming would be a much larger activity than crop farming.

The turbines have a 30-year lifespan, so the cost is more than just the initial capital expense. By 2050 all of the turbines installed in the next decade will have worn out, and we'd be into a continuous replacement mode. Cost? $5 trillion in capital outlay for the turbines, another $5 trillion for the infrastructure, and around $160 billion a year (present dollars) for worn turbine replacement.

Here's the storage problem:

The morning commute in any major US city lasts for about 3 hours, with most of the activity in that last hour. The evening commute is longer and more centrally distributed. If we have east-west transmission lines capable of moving most of the commute peak power, we can smooth the U.S. commute peaks into two with four-hour wide centers. Even assuming this transmission capacity, electric consumption during commute hours would be about 500 GW above average.

The current thrust of electric-car research is to improve the batteries so significantly that the cars can be charged overnight and the batteries can provide all necessary power for daytime use. Per vehicle, that's about 18 kilowatt-hours per car, which sounds possible. There is a problem, however: there simply isn't enough material to make these batteries for all our cars.

Lead-acid batteries store 15 watt-hours per pound, but can only use about 30% of that if they are to have a five-year life. 18 kWh would require two tons of battery per car, which is impractical. Among other things, it would require nearly a billion tons of lead for the U.S. car fleet. World production of lead is around 4 million tons/year, and total reserves are around 170 million tons.
Lithium-ion batteries store 75 watt-hours per pound, and can use about 60% of that (although a five-year life is a goal rather than a deliverable). 18 kWh would require 400 pounds of battery per car, which is physically possible. The U.S. fleet would require 93 million tons of lithium-ion batteries. Total recoverable worldwide lithium is 35 million tons.

The most economical way to store electricity is pumped hydro. Cars could pick up their electricity from metal strips in the freeway. Pumped hydro is at least plausible: the commute surge could be stored by pumping water from Lake Ontario back up to Lake Erie, raising Lake Erie by 60 cm twice a day.

Another way to achieve this goal is with nuclear reactors. Thousands of them. A nuclear electric infrastructure would have five big advantages over a wind infrastructure:

It would cost far less to build.
It would last 60 years or more.
It would not be weather dependent.
It would not require secondary storage (still more cost).
It would have far less environmental impact (no lakes with tides, no dead birds).

And the biggest advantage of all: it could keep getting bigger.

However, if we are to scale up the existing fleet of 104 reactors by over an order of magnitude, some things are going to have to change.

Nobody really knows how much it will cost to build the next American reactor. We know that it costs the Koreans and Chinese $1.70/watt, and we know that it used to cost about that much in the U.S. If we build thousands of reactors, the cost will drop back into this range or below.
Most of the new powerplants will have to be cooled by seawater or air, but not fresh water as is most commonly done today. We do not have enough fresh water to cool thousands of plants. Quite the contrary, by 2050 electric power and waste heat from reactors will be used to desalinate seawater for residential use, as is already the case in Florida and some California municipalities.
Typical reactor sites will have a dozen or more gigawatt-class reactors, rather than the two or three as is common today. Far from being "extra large", gigawatt reactors are right-sized.
Either very large new deposits of uranium will be discovered, or most reactors will be breeder reactors.

Bill Gates knows that the nuclear option is going to be the one we eventually choose, and he has a company, TerraPower, developing a new reactor which he hopes will cash in on the $100 billion/year domestic market for nuclear plants. I wish him the best.

Prediction, reviewed

2010-02-05T00:26:00.000-08:00

In December 2008 Obama fingered Stephen Chu to be the new Secretary of Energy. This got me in such a good mood that I made a bunch of "predictions", things that might be done right. Maybe these were more along the lines of wishful thinking.

Somehow, all this wishful thinking no longer seems wishful.

Yucca Mountain shutdown. They did it! The idea of Yucca Mountain was to build a geological repository for spent nuclear fuel. Sounds good, except:

Nevada didn't want everyone else dumping their waste in Nevada.
The stuff they wanted to bury was spent nuclear fuel from our light water reactors. This stuff is physically hot! These reactors fission hardly any of their fuel and breed almost as much non-weapons plutonium as they burn uranium. As a result, the stuff that comes out pumps out prodigious amounts of heat for decades, making it very difficult to cool via conduction through solid rock. Storing it aboveground in air cooled containers next to the reactor is a much better idea.

As an addendum to the Yucca Mountain thing getting shut down, they've appointed a commission to come up with a new nuclear policy for the US. Per Petersen is on that commission. He is a professor at UC Berkeley who understands the advantages of a fluid-fuelled reactor, and is also doing really good research in how to get there in a practical manner.
NASA just canned Ares-I, Ares-V, and Orion in favor of spending that development money on multiple private-sector launch systems that will ferry people to the ISS. What a great idea! This is an astounding choice, one that I talked about four years ago in one of my most popular blog posts ever: Why Merlin 2?
Mandating short-term demand management for air conditioners and other heat pumps. This hasn't happened, but at this rate, I guess I won't be shocked if it does.
Standardizing recharable batteries. In particular, I had in mind cellphones. While this itself hasn't happened, Europe has standardized the cellphone charger, and that's a good step in the right direction.

I suppose I should have some new wishes. Let's see:

I'd like to see at least four of those umpteen nuclear plant license applications actually turn into plants being built. I'd like to see hard hats and concrete.
I'd like to see the Sierra Club or Greenpeace change to a pro-nuclear stance.
I'd like to see the Federal government "make jobs" on projects that make long-term wealth, not just jobs.

Fountain Advice

2010-01-11T08:00:00.000-08:00

So, if I were to design another fountain, how would I do it differently? (This is for you, Diane.)

8 inch flow straighteners. There is no sense in messing around with Reynold's numbers. You want it to be around 2000, and that means you need huge internal cross section. 8 inch PVC is actually reasonably easy to get. SCP in Santa Clara has it and all the fittings you need.
Design gimballed nozzles from the beginning. Trying to get this right with careful assembly just did not work, the tolerances are far too tight. I think it can be done with screws between the gimballing nozzle and the glued-in support, so that you could adjust the angle after building it.
Rebar connecting the inside and outside rebar curtains. We have a crack all the way around our hot tub which I'm sure is going to make it's way through the tile some day.
I would build all the fountain jets to a fixture, rather than just half of them. The fixture worked really well and would have worked even better if I'd designed it to be independent of swelling due to moisture. This can be done -- all the surfaces that locate plumbing have to be on radial lines to the center.
Make the fixture locate a center #4 rebar spike, and drive the center spike at least 18" into the ground, and leave it in place while shooting the gunite. This will give the gunite crews something to locate off when they are drawing their circles. One problem that we had was that we kept re-finding the center of the hot tub, and as a result the circles for the plumbing and the circles for the tile and gunite are not concentric.
I would have the guys doing the gunite get the gunite surface level and ready for tiling. We spent a lot of time levelling that gunite out.

There were also a couple of things we've learned about the tiling, which would have saved us a bunch of time had we known it a year ago.

The glass tile is 1/4" thick, and can be set with just 1/8" of thinset, but this isn't the stackup you want. There are two problems: the thinset shrinks, a lot, as it cures, and this tends to bend and eventually break the tile. Also, the plaster guys want to be 5/8" thick, not 3/8" thick. They can feather down to 3/8", but they don't like it, as explained below.

So, you want to put down on the gunite 1/4" of some kind of low-shrinkage mortar, and screed it so that it is flat. This is the stuff that is going to take out all the uneveness in the wall. However, you can't be sure it's going to stick really well to the gunite. So, the stackup we used under the last mosaics ended up being:

2 coats of Hydroban, sticking out at least 1" past any of the rest of the stack. This forms a structural watertight barrier. The principle issue being protected against is water leaking through the cold joint between the plaster and the tile, and then leaking into the gunite from there. Hydroban is expensive, but only comes in 5 gallon buckets, which is enough to cover a ridiculously large area. I think they are trying to make sure you use a lot.
Some thinset, as thin as it can be, to adhere the mason mix to the hydroban.
1/4" mason mix (either "deck mud" for the tile on the pool bottom, or "fat mud" for the tile on the walls), screed to be dead flat.
After that all sets up (ideally about 4 hours so it gets a chance to shrink, but isn't fully hard, think about covering it with plastic to keep the water in), a super-thin layer of thinset on both the mason mix and the back of the tile.
Blue tape out the wazoo for anything on a wall.
Then cut the stiff but not yet really hard mason mix away from the edge of the tile. We never let the mason mix set up so hard that it was sticking to the hydroban tightly, so this was pretty easy to do without nicking the hydroban.

On our dam wall, we had to build up the wall top with an angle to hold our teflon strip. The easy way to do this would have been to just do it with wall mud, screed with one of those adjustable angle things running along a strip screwed to the side of the wall.

Now back to the reason the plaster guys want to put down 5/8" material. For any kind of exposed aggregate surface, they shoot the mix, then trowel it. The troweling is usually done (on a smooth plaster finish) to bring the "cream" to the surface, but for an exposed aggregate surface they are using the side effect, which is to compact the aggregate below the surface. Then, when they wash away the surface, they expose more tightly-packed aggregate. Since cement but not aggregate will erode from chlorine attack and mechanical erosion, it's better to have a surface which has more aggregate.

The reason they don't simply mix more aggregate into the mix before they shoot it on the wall is that, when the aggregate and sand grains are randomly oriented, they simply can't pack densely enough. If you subtract sand/cement/water, you don't end up with more aggregate in the as-shot mix, you end up with more air. And air is no good because the plaster has to be watertight (and dense and strong). Once the mix is on the wall, they work it with the trowels, which helps settle the aggregate and sand grains together more tightly. This is why the quality of an exposed aggregate surface has a lot to do with the skill of the guys doing it.

In looking at the samples provided, it's clear to me that most folks aren't actually attempting to get a maximum packing of aggregate, and I don't understand why. Why don't they mix larger and smaller aggregate together, so that the small aggregate packs in the spaces between the larger aggregate?

Pocohontas Retold

2009-12-28T08:30:00.000-08:00

Spoiler alert: I discuss the movie Avatar below.

When I read the Pocohontas story to my kids (we have the Disney version), we usually have a little discussion when we get to the page where Pocohontas attempts to dissuade her father (the local Indian chief) from starting a war with the settlers. The kids are interested in the idea that both people are trying to do the right thing, but they have completely different ideas about what the right thing is.

For those of you not familiar with the story, Pocohontas has fallen in love with a mercenary on the voyage (John Smith), and the two of them want to establish peace between the settlers and the natives. The book suggests that peace involves the settlers staying in North America. Powhatan, her father, is assembling a war party to drive the settlers away.

We can look back in history to better understand who was "right".

As the book makes clear, a war between the settlers and the Indians is going to lead to many Indian casualties, since the settlers have guns and the Indians do not. Furthermore, most of the settlers are not intending to do harm to the Indians, as they've been told they are settling land that has no ownership yet. Pocohontas' efforts end up saving many well-intentioned people's lives.
These same settlers would probably understand that, had they landed anywhere in England and built a village where they landed, they would be summarily evicted by whomever owned the land they were on. The racism here is lightly touched on in the book, but it's helpful because it's pretty easy for the kids to see how convenient it is for the settlers to suppose that nobody in North America owns anything yet.
I usually tell the kids what little I know of the Mauri, the indigenous people of New Zealand. As I understand it, they immediately made war with white folks who arrived. I suspect that the Mauri were territorial in a way that worked better with the White conception of property, and because of that Mauri today have a significant representation in the New Zealand constitution and legislature, and own very large amounts of New Zealand's real estate. I expect many Native Americans would prefer the Mauri outcome to their own.

I recently went to see Avatar. It's basically the Pocohontas story, but the ending has changed and the natives switch from the Pocohontas to the Mauri approach. The change comes from two differences:

The Na'vi are territorial. They have a few specific high-value trees. My understanding is that most of the North American natives had a much less specific sense of property.
The movie has the natives resisting under human leadership, which is interesting to think about. It seems a bit condescending (especially the bit where the human, after 3 months of training, is outperforming the best of the natives), but historically North American natives really did not grasp the nature of the European threat fast enough to organize a massive resistance in time, and it seems at least possible that a charismatic European might have communicated the continent-level consequences of the European idea of property to enough of them to organize a resistance.

Although the movie doesn't make it clear enough, guns are a big advantage, but a multi-year supply line is an even bigger disadvantage. Although some of the dialog is a bit trite, I think the story is probably going to be a useful place to start interesting discussions. Hopefully they'll have some story books out at some point, because the PG-13 movie is far too violent for my kids to watch.

I once asked a friend who is a lawyer if all property rights, at least in North America, trace back to peace treaties of some kind, or if some (particular the French claim to the center of the continent that was then sold as the Louisiana Purchase) are based on bald assertions of authority without even a war. I never did get a decent answer.

If, in reading this post, anyone is wondering if I'm willing to cede my house to a Native American, the answer is no.

Powered Roadways

2009-12-14T12:08:00.000-08:00

If it weren't for the battery problem, an electric vehicle could be a fairly reasonable vehicle today: electric motors are powerful, small, and cheap enough, etc. There are two parts to the battery problem, getting enough power and storing enough energy. Both can be solved by delivering power to the EV from the road. This has been considered many times before, and there are electric street cars that do it in Bordeaux.

The usual idea, however, is very expensive because

most sections of roadway or railway see little traffic and so the benefit of the high-cost infrastructure is spread over few vehicles.
the third rail power delivery system is made safe by expensive grade separations, fences, or electronic switching
the vehicles are very specialized and aren't built in large numbers.

So, to the extent that I'm advocating a new idea, it is... electrify urban highways. By which I mean, install a pair of metal strips flush against the paving in one of the lanes, such that ordinary cars aren't affected, but electric cars can lower a suitable pickup onto the strips and receive a few dozen kilowatts. Both the power and the energy storage demands on an electric vehicle's battery are dominated by the demands of highway operation.

Urban freeways are quite unusual as roads go.

They see quite a lot of traffic: The San Francisco Bay Bridge moves 270,000 vehicles a day across 10 lanes = 1 vehicle every 3.2 seconds over a 24-hour average.
They see quite a lot of the traffic: 24% of all traffic is on interstate highways, and I'll guess that most of that is on urban interstate highways.
They are short: in the entire US, there are just 15,300 miles of interstate highway in urban areas (same link)
They already have limited access. The safety hazards of a high-voltage electrical system out on the road are relatively minor compared to the existing vehicles using the roadway.

I don't have sources to verify the following claim, but I'm fairly sure that in many urban markets, most trips over 10 miles include some freeway. So, if the freeways in your urban area (e.g. Los Angeles or the Bay Area, or both) were electrified, you could make trips anywhere in that area in an electric car with a battery range of just 10 miles.

And, if all we want is 10 miles of range, with no need to deliver dozens of horsepower for minutes on end, existing battery technology is good enough.

The usual counterargument to big infrastructure is that it costs too much. However, electrifying freeways does not because the freeways are just not that big. Consider the Bay Area:

300 miles of freeway
7 million cars

If, over 10 years, we got to 10% of the cars being EVs with electric pickups, that would be 700,000 EVs, or, one for every 26 inches of freeway. Can 26 inches of roadway be upgraded for less than the cost of equipping an EV with a huge battery? Definitely.

There are many schemes for electrifying roadways, and some are quite complex. Although a simple pair of flush steel rails at 1000V is probably a reasonable implementation, it might be easier to sell to the public if the rails were safe enough to be touched by hand. This too is possible.

Imagine each rail is a hollow box, insulated on three sides, but with a nonmagnetic and top surface. Inside the box is a lightweight, magnetic, conductive cable (probably aluminum and steel), with a small gap between it and the underside of the top surface. The conductive top surface is broken at short regular intervals by an insulator. The bottom of the rail is probably a large conductor for moving electricity thousands of feet.

Without a magnet, the top surface is not electrified, and you can place your hand on it safely. The car's pickup would have a magnet which would ride on the strip, picking up the lightweight inner cable slightly, so that it contacts the top surface and conducts to the car.

Other variations would have a magnetic top surface with a flux gap, such that flux going from one side to the other shorts through the cable and picks it up that way.

System Design for Martha

2009-11-23T01:04:00.000-08:00

I need to buy a new computer for Martha.

Must drive a flat panel display
Must accept data from a FireWire miniDV camera
Must have a DVD burner
We have an ancient parallel-port printer.... which would be nice to use.

I could buy a Mac Mini. The Mac Mini has the FireWire interface and DVD burner. However, it will never work with that printer (a replacement will cost $150). The graphics would be much better than any mini-ITX integrated graphics I'd get. We'd get the 2.53 GHz, 4 GB memory, 350 GB version, $830. A VMware executive will cost another $70. The whole thing will come in a nice little case and make very little noise, and I will have even less idea how the software works than I do with the PC.

Or, I could build a PC. I'd get a 3.16 GHz Intel E8500, 8GB memory, 500 GB hard drive. I can get a FireWire card and a DVD burner, and a motherboard that sports a parallel port. Martha will be happy that I didn't make her figure out a Mac (more to the point, how to run PC-only software under VMware on the Mac). Vista will almost certainly never work with the printer, and so I'll still have to get a replacement anyway (a wash at $150). Even crammed into a mini-ITX case (with some risk it will not all fit in the case), it'll cost $875. The Mini idles at 14 watts, and any PC I build will idle at 35 watts. The 20 watt difference, over 5 years of 24/7, costs an extra $350.

Update: Since Martha figures she's going to be stuck with the sysadmin, she opted for the PC, to avoid learning about VMware, Boot Camp, or any other virtualization. If we could order the Mac Mini with Windows preinstalled under a supervisor, such that I could have told Martha that she could simply install any Windows programs or drivers, then she probably would have gone for that. Oh well.

Engineering is Plumbing

2009-11-19T13:44:00.001-08:00

http://credentiality2.blogspot.com/2009/01/engineering-is-plumbing-not-math.html

99% of what I do is plumbing.

-Iain

Quick pool status

2009-11-16T11:19:00.000-08:00

Patio around the pool is mostly in. Hopefully today they will finish off the corner around the pump vault.

Saturday I had hoped to install the last of the tile mosaics, but instead I found the remaining big Orca cracked in the center, and the north side dolphins had cracked as well. We cut them all off the wall and will reinstall the lot next weekend.

The tilework around the hot tub was fairly tricky. Here's an example of a three-way miter. The tile guys kept looking at me like I was cuckoo. As I explained, you cut it by cutting each of the three two-way miters. It's actually pretty straightforward if you just do it.

The hot tub as a whole. In the background, you can see the breaching Humpback mosaic, along with a portion of the Orca mosaic. The Orcas are the ones that have been giving me so much trouble.

Chuck DeVore nails it

2009-11-06T09:01:00.000-08:00

Relative Risk: Global Warming and Imported Fossil Fuels vs Nuclear Power

It's from last year, but Representative DeVore perfectly summarizes the environmental aspirations and political logjam in California, and points out that a voter initiative is possibly the only way to cut through the logjam.

Anniversary of Lezak's Wild Ride

2009-10-06T08:00:00.000-07:00

For the first anniversary of Jason Lezak's incredible come-from-behind finish in the Men's 4x100m freestyle relay, NBC has full-race underwater coverage of the race: http://www.nbcolympics.com/video/player.html?assetid=0812_hd_mul_au_ce493&channelcode=sportsw (Watch the link in Firefox, because it doesn't work in Chrome.)

I've written about this incredible race before, but this footage shows in more detail some of what was going on during the race. Although the Australians were doing well at the beginning, by the last lap it boils down to the French and the Americans. America's Lezak takes 29 strokes on the way out, versus France's Bernard Alain, who takes 32. Not much difference, although it is already interesting that the taller Frenchman is taking more strokes.

On the way back, things change. Lezak takes 34 strokes, and Alain takes 42. Something happened to Bernard's stroke on the way back, something that didn't happen to Lezak.

Looking at this video again, it's clear that Jason has a very different stroke than Bernard. Maybe it's because he breathes only to his right, and does so on every stroke. But I think there is more going on than that. From the top camera, watch Jason's head. It's going up and down a lot more than Bernard's. Watch his back. His back is pumping up and down more than Bernard's as well. From the underwater camera you can see that Jason is pumping the left side of his body up and down. Bernard goes straight through the water, which looks more efficient, but I don't think efficiency is what is going on here. I think Jason is pumping water backward with his whole torso, like in the butterfly.

One other note: Jason is blowing so much air under his body that his left hand is travelling through that air. Grabbing air cannot be helping propulsion, but it's possible that by getting that air under his body he is reducing his drag.

I'm pretty sure Jason Lezak has found a better way to swim the freestyle.

The Toy I Always Wanted

2009-09-12T09:50:00.000-07:00

When I was a kid, I used to dream that I could make stuff pop into existence if I could just imagine all of the details.

Now I have SolidWorks.

I draw stuff. It takes a really long time to draw anything, compared to doing it by hand, just like I imagined it would. But once you get the hang of it, you can push a lot farther than you can with hand drawings.

Once drawn, I crank out dimensioned drawings, and then call people who build things for me. And they look just like the drawing.

This is what I wanted when I was 8.

Last weekend I made a model of one of our new gates.

Then I made a drawing of that:

While I was at work this week, Jesus came by and built it for me, and now I have the first of three new gates:

Obviously, this isn't quite the same as what I drew. The back gates are much shorter than the front gates. Jesus doesn't need a seperate drawing for each gate, just the idea of what I want.

I started out with hand drawings of the gate, and for this project, I probably could have just left it like that. But it turns out that hand drawing curves, and trying out lots of different curves and ratios to see what you like, is not so easy. With a parametric CAD system, you draw it once and then fiddle with a few numbers until you like the way it looks. Much better.

Coping being cut

2009-08-27T22:16:00.000-07:00

Our in-ground pool is actually raised out of the ground slightly (18 inches near the house). This makes the side a nice bench to sit on, keeps cut grass from blowing into the pool, and should interfere with running and jumping into the shallow end at a steep angle.

One consequence, though, is that our coping stones are a nonstandard width. We've decided to have bullnosed coping (so these are bullnosed both sides, also nonstandard), and that requires that the coping overlap the waterline tile by over two inches. This kind of thing adds up:

Waterline overhang: 2.5 inches
Tile thickness: 0.25 inches
Thinset: 0.375 inches (that's a lot, to give the mason plenty of freedom to flatten the wall for the enormous glass tile mosaics that are going in)
Bond beam: 12 inches
Thinset: 1 inches (the outside of the bond beam is quite uneven)
Facing stone: 1.25 inches
Exterior overhang: 2.5 inches

All up, we've gone for coping that is 20 inches wide.

We actually had a order placed for some very nice pearl white travertine (from Olympic Stone). When it came time for them to come by and pick up the check... they didn't. We called back and found there was some sort of problem... they didn't actually have the stone. it would be a 3 month delay to get it from Turkey.

Well, that's never a good thing to tell a customer. Martha started looking around, and found another very nice stone, this one a three color granite, from American Soil. This one is more expensive, but it really is pretty, and it's available right now. We ended up buying it. (We may use OSM's pearl travertine for the face of the pool rather than the coping, since they apparently have the 1" stuff available.)

[Update 16-Nov-2009: The pearl against the walnut travertine ended up not looking as good as we'd hoped, so we ended up using the walnut travertine on the sides of the pool. You can see this in the mid-November post.]

By "it", I mean a 12 ton boulder imported from Columbia, California. You can get a sense of scale from the pickup truck at the back right. This rock is a little shorter than I am.

It came from over here:

View Larger Map

They're chopping this thing up into 20 inch wide by 36 inch long by 2 inch thick coping stones for us.

This is a cable saw. The cable has some kind of abrasive on it (I've never actually seen the thing stopped, it appears to be running all the time). The huge wheels drive the cable through the stone. Above and below, they're whacking the top off the boulder.

Below, they're cutting the ends off. In this pass, the rock stays put and the machine basically drops through it at a half inch per minute (I'm not really sure, as I never saw the saw make any noticeable progress through the rock).

Here's one of the slabs coming off the cable saw, going into their indoor facility for shaping. You can't really see all the color here, but there is white, black, and some pink to it.

Here's the rock all chopped up:

There's a lot of white in some of these. Hopefully they'll be able to cut around that to some extent.

Not so much in others.

This equipment is usually used to make countertops.

American Soil just got a brand new Italian machine for cutting and bullnosing. This isn't it, since apparently that machine can't cut a straight line just yet.

Each stone should weigh about 140 pounds. I'm sure the mason will be very happy to hear that.

I'm really happy with how this looks. We still have some risk, in that the coping could have huge blobs of white in it, or the grain could get mismatched, but the folks at American Soil seem to be on top of that.

We've also picked up all our glass tile. It gets installed after the coping, but I'll try to post some pictures of the pieces assembled in our garage so you can get a feel for it.

The Limits to Growth

2009-08-16T12:22:00.000-07:00

Folks in an apocalyptic frame of mind will sometimes consider what would happen if everyone in the entire world were to adopt a lifestyle which consumed resources at the rate of those of us in western countries. To keep this blog post short, I'll not address the entire problem, but I would like to point out that carbon emissions need not be a problem.

I'll take as my example the French. French people live a pretty good life on about 6.1 tonnes CO2/person/year, which is the lowest of the countries in the G8. The French low consumption is possible because their electric sector doesn't emit significant CO2 or burn significant fuel and has stable prices (it's 85% nuclear and 10% hydro). So as gasoline prices have gone up (mostly taxes, but large increases in crude costs too), folks have switched to electrified mass transit. Their electric-powered TGV trains carry almost as much traffic as their domestic airlines.

Is French low consumption really a result of nuclear electric production? Yes. Consider Germany at 9.8 tonnes CO2/person/year. That would be 5.9 tonnes CO2/person/year if their electricity sector was nuclear, which is about the same as France.

[Update: for comparison, the United States would be at 11.3 tonnes CO2/person/year if we replaced all our coal and gas fired powerplants with nukes. If we replaced half our air transport with electric trains, it would help a bit more, but I think less than 1 tonne CO2/person/year.]

My point is that the French example can be applied to many countries. Now here's an interesting thought. What if the entire world were to adopt the French lifestyle, including the carbon-free electric system? How catastropic would the emissions be?

The world population is now 6.7 billion, so at 5 tonnes/person/year, that'd be 33.5 billion tonnes/year. Compare that to our current emissions of 28.4 billion tonnes/year. It's larger by 18%. Something to work on, not a catastrophe.

Obviously, it's not quite so easy. Right now, a fair bit of the carbon going into the air comes out of the ground in solid form. If the entire world were to use nuclear electricity, coal production would nearly stop (it's still needed for steelmaking), and all that carbon would be coming from petroleum and natural gas. That would take a fairly drastic increase in production capacity for both, leading to a rapid depletion of existing stocks.

The summary: anti-growth doom and gloom is unnecessary in the electricity sector, so long as folks are willing to follow the French example.

Side note: French reactors are almost all inland and cooled by river water. This is perhaps an example best not followed. The French have laws which prohibit those plants from releasing back into the river water which is too warm. So, during a heat wave two years ago, some power plants reduced generation in order to reduce their output temperature, right as electricity demand was spiking.

Seawater cooling is much more reliable, and doesn't use up fresh water either. Some day, when we have high-temperature molten salt reactors, we will be able to air cool our nuclear plants, and then this will not be an issue. Until then, we should probably build the majority of nuclear power plants near the coast.

Almost time for a new car

2009-08-08T08:00:00.000-07:00

Our minivan has hauled our dogs, kids, and gear for almost 9 years, and it's starting to show. In another couple of years, we'll need a new car. So, if you're building cars and wondering what to build next, let me tell you what we want.

The last time I knew I was going to buy a new car, I wrote a letter to Chrysler two years ahead of time. Fat lot of good that did. This time, I'm asking for essentially the same thing. I'll post it on my blog instead.

We want a plug-in hybrid minivan. Plug-in hybrids face a couple of big problems: the batteries are too heavy and the engine runs intermittently, which prevents the catalyst from firing up and leads to nasty emissions. I think both these problems are completely solvable for a practical vehicle that we would buy in a heartbeat.

First, I'll point out that 1100 pounds of lead-acid batteries can store 16 kilowatt-hours, which is the government's definition of an electric vehicle. Those batteries can survive five years of cycles through 30% of their capacity. 4.8 kilowatt-hours is enough to push a minivan 13 miles. That's less than the average daily drive of 33 miles, but for a minivan used for multiple short trips a day, it's easily good enough.

Next, I'll point out that the emissions problems can be solved by delaying the first ignition of the engine. If the minivan can get to 50 MPH on batteries alone, then it can avoid the engine everywhere but on the freeway. For most trips our miniman makes, that means no engine at all for most trips, and that basically eliminates the emissions problem.

Finally, I'll point out that regenerative braking extends the EV range just a bit, and comes with a lot of complexity (control interaction with the friction brakes) and cost (fancy controllers). I'd certainly be willing to live without it if it cost $1000 and only got me an extra mile of range.

Here's what the minivan would look like:

Packaging
- It should have seating for 7: 2+2+3.
- It should carry many 4' x 8' sheets of plywood in the back.
- It should have two sliding side doors, etc, just like real minivans.
- Seats do not have to stow. They can come out like my current minivan's seats do.
- Including battery pack, it should weigh 5200 pounds. That sounds like a main battle tank, but it's pretty reasonable once you think about the 1100 pound battery pack.
- Weight distribution should be close to 50:50 front:rear, and the center of mass should be very low, so the thing should handle reasonably well.
- The thing should be quiet when driving in EV mode.
- It should plug into a normal 3 prong 120V AC outlet.
Performance
- 0 to 60 in 10 seconds. (Requires an average of 115 wheel HP.)
- 0 to 60 in 20 seconds on batteries. (Requires an average of 57 wheel HP.)
- 75 MPH up a 6% grade with 1000 pound load. (Requires 77 wheel HP, plus whatever is needed to go in a straight line at 75 MPH. 115 HP ought to do.)
- Maximum cargo load of 1400 pounds.
- It should go 13 miles on a 30% cycle of the batteries.
- It should go 350 miles on a full tank.
- EV mode should work: the car should be able to cool a hot interior and get to 50 MPH without starting the gasoline motor.
- 20 MPG from the gas engine alone. That's about 4000 joules/meter of gasoline energy, or 15 cents/mile for gasoline at $3.00/gallon.
- It should use about 800 joules/meter of battery energy. That's about 4 cents per mile for the electricity, at the average US residential rate (10.5 cents/kWh).
- The batteries should charge from 70% to 90% in 90 minutes from a standard plug.
- The batteries should charge through a 30% cycle in 5 hours.
Drivetrain
- It should have front-wheel drive from the gas engine.
- The gas engine should be a 2 liter 4 cylinder engine with around 130 horsepower. That sounds anemic, but add 60 electric horsepower and it's a whomping 180 HP.
- It should have rear-wheel drive from the electric motors.
- The motors should deliver 60 horsepower at 30 MPH (torque limited below). This will give excellent performance in deep snow over pavement.
- The electric motors can have their torque die to nothing at 70 MPH. Any faster and the gas engine is required anyway.
- It should have about 1100 pounds of lead-acid batteries, which deliver 17.5 megajoules with a 30% cycle. This just hits the 58 megajoule full-cycle battery that the US government is willing to subsidize as an electric vehicle -- $7500!
- It should have a 330 watt solar panel covering most of the roof. This sounds silly but it's actually a good idea. The panel adds about 4 miles of electric range on an average day in California, at almost the same cost per mile of range as the battery, with very little weight.
Cost
- The thing will go 17.5 miles a day in EV mode if charged only at night and parked in the sun, and 27 miles a day if charged at work as well. If used as a daily driver, it'll cover 6,000 to 9,000 miles a year in EV mode.
- It will save around 5 or 6 cents per mile. Obviously, that's not why people would buy it, but it does make for $300 to $500 saved each year.
- The roof panel will cost about $1200.
- Battery swap costs $1800 (half of the new cost). Batteries should last 5 years, or 1800 30% cycles, so that they cost 6 cents/mile. Existing lead-acid batteries already achieve this cost.
- The added cost will take 10 to 15 years to pay back (if you ignore the subsidy).

I think the drivetrain can be a lot simpler than a Prius drivetrain. In particular:

The electric motor/generator on the gas engine doesn't need to be big. It needs to be big enough to start the engine quickly (maybe 10 horsepower), and that's about it. I don't want to recharge the batteries from the engine any faster than 10 HP anyway. Gasoline costs 3 times as much as electricity from the plug, so the only reason to charge the batteries with the engine is if I can avoid starting the engine later in the same trip.
Make sure the heater and air conditioner can run off the batteries. It's important that these be able to run right at the beginning of a trip without having to turn on the gas motor.
Lead-acid batteries. Forget the fancy batteries. Even lead-acid batteries cost more than the electricity from the plug costs, other batteries are worse. Lead-acid can deliver the necessary range and power without the availability headaches of NiMH or Li-ions.

I think that roof-mounted solar panel deserves some explanation. It has a lot of interesting benefits:

On a sedan, there wouldn't be enough roof area to make a significant solar panel. A minivan, on the other hand, has a pretty big roof, so the idea works better.
The car can run its fans continuously when unattended. When you get to your car sitting in the parking lot in Phoenix, it doesn't hurt to sit down or touch the steering wheel. The interior won't disintegrate in the extreme heat either.
When the ignition is turned off, it should be possible to turn on the A/C and get 70 cfm of air cooled by 40 F. That's enough to turn over the car's air every 2.5 minutes. It won't cool a car that's already gotten to baking temperature in the sun, but it will keep a car cool after you turn it off.
Batteries don't like to be run down for long periods. With a solar charger, the car will get some juice every day, which can keep the battery topped up if you leave the car unattended for a while. This will improve the battery life, and it's just nice to come back to a car and have it fully juiced.

In our family, Martha would drive this thing, using it primarily to move the kids around. She makes multiple short trips each day, usually not on the freeway, so it would get plugged in regularly and probably only use gas for the trips to my parent's house, which is 55 miles each way. Since we'd get plugged in while at their house, the minivan would end up driving 80 miles on gas, on the freeway, where it gets 26 MPG. If we do twenty trips like that a year, we'd burn just four tanks of gas and our overall gas mileage would be 195 miles per gallon of gasoline.

"When did you last fill up?"

"Spring."

Seems like a winner to me.

World Wildlife Foundation donations suspended

2009-07-30T14:07:00.000-07:00

At the July 8-10, 2009 G8 summit in L'Aquila, Italy, Allianz (a global insurance company) partnered with the World Wildlife Foundation to deliver and publicize a report on how the 8 richest countries in the world are doing at reducing their greenhouse gases. Sounds good.

WWF/Allianz "does not consider electricity generated by nuclear power a sustainable option", an opinion shared by many. Their trouble was that any simple ranking of countries will show that nuclear power has made France the world leader in reducing greenhouse gases. Since WWF/Allianz doesn't want to promote nuclear power, they cooked the numbers.

They didn't lie. There have been a number of outraged comments about this report, but these folks did not lie. Their footnotes say specifically that numbers for France were "adjusted as if electricity from nuclear power was generated from natural gas." The report also includes, in footnotes, the numbers correctly calculated.

One of those same footnotes says that "without the adjustment, France would rank first with Germany." Unfortunately, this comment is not supported by either facts, or by the WWF/Allianz numbers. By any numeric measure, France is way ahead of the rest of the industrialized world.

Because I feel that this report is intentionally misleading, my wife and I are suspending our donations to the WWF until they amend their report to rank countries based on facts. We're also going to have a talk with a few friends who also donate to the WWF. We don't do business with Allianz, so there's not much leverage there.

Those of you who don't actually care that much about CO2 emissions or global warming can stop here.

The report ranks the 8 richest countries in terms of their "past, present, and future climate performance". Here I've listed their overall ranking, along with WWF/Allianz' calculation of their emissions per capita and per million dollars of GDP.

Germany (12 tons/capita/year, 384 tons/M$ GDP)
United Kingdom (11 tons/capita/year, 334 tons/M$ GDP)
France (9 tons/capita/year, 276 tons/M$ GDP)
Italy (9 tons/capita/year, 328 tons/M$ GDP)
Japan (12 tons/capita/year, 367 tons/M$ GDP)
Russia (16 tons/capita/year, 1140 tons/M$ GDP)
United States (25 tons/capita/year, 567 tons/M$ GDP)
Canada (24 tons/capita/year, 668 tons/M$ GDP)

France got dinged because they have not improved emissions much since 1990 (they'd already built most of their nuclear fleet by then). I notice they also got dinged for not having strong mandatory targets imposed on utilities to promote energy efficiency. The report fails to note that in France, saving electricity doesn't significantly reduce CO2 emissions, so there is no need for such mandatory targets.

The report completely failed to note that France is building new nuclear power plants on its borders to export more CO2-free power. Not only is this action going to cause more improvement in Germany's CO2 output than Germany's own utility policies, but it is also going to be profitable, which means that France is going to be able to do it AGAIN in a few years. Germany, on the other hand, is busy bankrupting itself with huge feed-in tariffs, and is already switching from expensive, imported aranthracite coal to cheaper domestic brown coal which emits more CO2 and other pollutants.

The United States clearly needs to clean up its act. Which country should we model our environmental policies after?

Germany: 51% of German electricity comes from coal-fired powerplants. They are building or planning another 26. These will add 23 gigawatts of production. Germany will be forced close its coal mines in 34 years when it runs out of coal, at which point their coal imports will peak until they will switch to imported Russian methane. Germany also produces 4.4 gigawatts from wind turbines. There is a lot of talk about wind turbines but the power comes and will come from coal.

France: France closed its last coal mine in 2004. 4% of its electricity comes from coal. 78% of France's electricity comes from nuclear, and produces no CO2. Most of the rest (11%) comes from hydro, and produces no CO2. France exports 18% of it's electric production, and most of that (5.9 gigawatts, more than $2 billion a year) is sold to Italy, which is one reason why Italy's CO2 outputs are low.

Bottom line: WWF/Allianz fudged the numbers to support a policy goal. That's wrong, and we're stopping our contributions until they fix it.

It's a shame, by the way. I liked some of the other stuff they were doing.

Why New Nuclear

2009-07-25T00:28:00.000-07:00

Senator Alexander Lamar has a white paper which well summarizes how I feel about our desperate energy situation, and lays out a plan for how to fix it:

Blueprint for 100 New Nuclear Reactors in 20 Years

It does have a thought which was new to me, however: Russia, China and India, as well as a host of other countries, have already built out a fair bit of coal, and are beginning a large build of nuclear. If their nuclear build fails, they will fall back on coal, and nothing the US does will change the course of global warming. If their nuclear build succeeds and surpasses us, they will cement their existing lead in the next major source of energy, and they will end up owning the base of our entire economy.

And this base is enormous. The US GDP was almost $14 trillion in 2007. Generation of electricity, at about $40/MWh, was $170 billion that year. But that electricity sold for $90/MWh, for a total of $373 billion. Electricity sales are 2.7% of our entire economy.

And consider industries that are part of that industrial base. In 2007, the United States used 4.1% of our electricity (170 million of the 4156 million MWh) to smelt 23 billion pounds of aluminum. That aluminum sold for $26 billion. The aluminum smelters probably spent around $40/MWh for that electricity, so the juice was 26% of their cost of goods sold. Since aluminum is an easily transported global commodity, their profit margins are thin and small changes in their costs can lead to large changes in who makes the aluminum.

We need to own our energy supplies. We need our own large forge to build the reactor pressure vessels (right now we depend on Japan). We need American companies to build, own, and operate these reactors. And we need it now.

What we really need is to stop the Waxman-Markey cap&trade bill, and adopt Alexander Lamar's plan instead. Write your congressman.

My Response to the New York Times

2009-07-08T18:00:00.000-07:00

Here's a link to the New York Times article "Combative Start to Senate Climate Hearings".

And, here's my response:

I’m a Californian, I vote, and I want more nukes in my state. I’m fed up with the high cost of electricity. I’m pissed off that we switched from making plastics with our natural gas to making electricity — and shipped our plastics industry to China. That’s not environmentalism, it’s offshoring, as a direct result of public policy that my representatives voted in.

My power company is not incented to make good decisions about the power mix: when natural gas prices rise, they pass along the cost. When they look at natural gas they see a lower capital cost, and so they get the same return on less capital. Fine for them, but we get stuck with power prices that whipsaw our producers out of business. Ever noticed how inflation is quoted without the volatile food and energy component? We chose to make our energy prices volatile!

What we need right now are projects like the Hoover and Grand Coulee Dams: big, expensive government-funded projects that get lots of people working in well-paying jobs and deliver locked-in low priced power for a century or more. Nuclear plants are way better than hydro plants since they don’t kill fish (or anything else, for that matter).

I want to vote for a future in which energy prices are not volatile, and where the aluminum smelters and plastic plants come back to where we can regulate them and work in them. But I seem to be stuck between a choice between Green folks, who want to build temporary windmills which will kill our economy, and Conservatives who want to stick with imported fuels, which will kill our economy. Give me a third choice!

Fastest Freestyle Ever

2009-07-06T20:00:00.000-07:00

The men's 400 meter freestyle relay at the Beijing olympics was amazing. The French team absolutely crushed the world record time, and the Americans squeaked past them. Right up until the last 50 meters, the French were in front.

Don't talk to me about Michael Phelps, the second-slowest guy on our team. Let's talk about Jason Lezak. Jason gets in the water at 2:38. (Watch the video here.) Look at his stroke compared to France's Bernard Alain. He looks pretty similar (to my untrained eye). And he turns in a time on that first 50m that is pretty similar: 21.50 versus Bernard's 21.27.

And then, after that last flip turn, Jason Lezak swims the next 50 meters in 24.52 seconds. Which sounds slow compared to those first 50 meters, but it's so fast compared to everyone else that he was one of only 3 guys in that race to swim in less than 47 seconds... and he beat the other two guys (both French) by 0.57 and 0.67 seconds. That's HUGE. He nearly did it in less than 46 seconds.

Watching back in August, it was immediately apparent to me that Jason changed his stroke after his flip turn. This morning I looked up the video on the internet, and it raises more questions than it answers.

First, Jason takes 34 strokes to Bernard's 42. It's not like Bernard is some short French dude -- at 6'5", the guy is actually an inch taller than Jason. Discounting the 7 meters that both guys got off their kick at the end, Jason managed to go 49.8 inches on each stroke, vs the paltry 40.3 that Bernard manages. And, since Jason is going faster, he's got more drag and so his hands should be slipping back more. Where did he come up with an extra nine inches?

For those last 34 strokes, Jason's form appears to go to hell. His timing is no longer even -- the delay after throwing his left arm forward is less than the delay after his right. Worse still, the change in timing has his left hand grabbing the air that he's blowing out, which has to be terrible for maximizing the purchase on the water the whole way back. Compare to Bernard, who efficiently vents smaller bursts of air under the left portion of his body while his left arm is airborne.

Notice something else that Jason is doing. He's ducking his head down after he takes a breath. And watch his right shoulder roll. When Jason pulls back with his right hand, he launches a portion of his torso up, over the water, and then when he pulls back with his left hand he is porpoising the right half of his body over that water.

Has Jason incorporated some of the body motion of the butterfly into his freestyle?

Another insulated pool

2009-06-18T08:05:00.000-07:00

Back when I posted about the insulated in-ground pool that I'm building, I asked if anyone else is building such a pool. I've received a few answers:

One reader in Melbourne is building such a pool.
Several have been built in the United States, but only one of the ones I've heard of is residential. The rest are all commercial facilities.
Insulated pools are standard when the pool sits on top of a parking structure. Apparently installations like these are simply impossible to heat if the pool is not insulated, and there are structural isolation benefits as well.

Up until now, though, no pictures! Thankfully, the reader from Melbourne has recently written in to share a few pictures of his insulated pool. Here's the standard picture of the dig:

The pool is 46 feet long, which is exactly the same length as mine. His is skinnier (10 feet wide) and more shallow (max 6 feet), which is appropriate for a lap pool. Below, it looks like they are installing an in-floor cleaning system. Very nice.

Below is a pic of the insulation going in. He is using Dow Highload 100, sold there as Dow HD300, in the same thickness that I used (2 inch). He says:

The insulation I'm using is Dow HD300 in 50mm boards. This product is made for insulating under coolroom floors with trucks driving on top, and is overkill given its compressive strength specs of 2% compression (1mm) after 20 years of 250 kPa or around 25 tons per sq meter. However, the pool contractor and engineers had never seen pool insulation done before and through an abundance of caution over-specified for the highest compressive strength product they could find to be sure it wasn't going to settle. With the loads from this pool of only around 2 tons per square meter, we have more than an order of magnitude margin of safety. In the end, the cost differential between this and lesser rated products was so small that in the interests of getting the pool contractor comfortable with signing off we went with the HD300.

The contractors didn't glue the boards to the soil with foam, instead they used the rather unsubtle method of nailing it through with steel rod. I had two concerns about this:
This will mean there's some heat conduction losses through the steel rod from the soil to the concrete, though the total surface area of steel in contract with the cement shell would still be minimal so this probably isn't a big deal.
A risk of the rod eventually rusting and applying pressure to the concrete shell, but the foam will (I hope) compress enough to accommodate any rust expansion and prevent concrete spalling off the shell were this ever an issue.
The upside is at least I don't have to worry about the compression issues for the expanded foam glue you'd used and hence avoids the risk you mention in your blog that this may place extra strain on the shell as it settled, and from the photos it seems the contractors have got a good solid base without the rocking problems you'd mentioned.

The steel rod seems like a good idea. I tried to find an equivalent product here and failed, which is why I ended up with the polyurethane foam. One other contractor I've talked with in the U.S. also used foam, but I neglected to ask him if he chose not to use steel nails for some reason.

Here in California we use Dobies to seperate the rebar from the ground/insulation. Dobies are simple 3" x 3" x 3" concrete cubes with a wire in them. Check out the much snazzier looking rebar spacers they use in Australia. The wall does not appear to have a bond beam at the top, but instead is pretty thick the whole way up.

Insulating the piping has been a major effort on my project. It's not clear in these pictures if this pool's piping is insulated.

Gunite going in:

His pool is in basically the same condition as mine right now. Note the clever combination of bench seat and stairs at the right hand side of the pool. Very nice. The pool looks deeper than it is because the lot slopes up to the left, and the left hand side of the pool is a retaining wall (raised bond beam).

It's a nice looking project, and I'm very curious to see how it turns out. Thanks a lot, Melbourne!

A professional look at The Day After

2009-06-14T08:00:00.000-07:00

Here is a set of essays on the calculus of nuclear war, written by someone who used to plan nuclear war. They are short, funny in places, reassuring in places, and generally scary.

http://homepage.mac.com/msb/163x/faqs/nuclear_warfare_101.html

http://homepage.mac.com/msb/163x/faqs/nuclear_warfare_102.html

http://homepage.mac.com/msb/163x/faqs/nuclear_warfare_103.html

Of course, no mention of nuclear weapons is complete without directing readers to the Nuclear Weapons Archive, by Carey Sublette. I remember first reading the FAQ in 1996 or so, and being astounded. It changed the way I thought about The Bomb.

http://nuclearweaponarchive.org/

It's the physics bit that got me. I had previously though of fusion bombs as being somewhat like the Sun, only, here. But it turns out that fusion in the Sun proceeds along quite slowly, at comparatively low temperatures and pressures. Fusion bombs operate at much higher pressures and temperatures than stars do, and (obviously) on much shorter timescales. It turns out to be almost completely different physics.

For some reason that really bothers me. The notion that we use physics that can't even be observed anywhere in the natural world seems odd. Perhaps I'm succumbing to nuclear hocus pocus, since I can't think of anywhere in the natural world that we can observe hydrocarbon-oxygen combustion at dozens of atmospheres of pressure, and yet our cars and airplanes do that all the time.

You are so beautiful, Kathleen

2009-06-10T23:17:00.000-07:00

Reynolds number

2009-06-07T13:00:00.000-07:00

It looks like one of the problems with the fountain is that I'm pushing slightly too much water through the flow straightener.

At very low velocities, flow through a pipe is laminar. I wanted laminar flow in the flow straightener because laminar flow has no turbulence which can then break up the output jet. It turns out that the flow velocity in the pipe has to be incredibly slow, and it turns out that I managed to design my fountain to be right in the transition region between turbulent and laminar flow.

Here is the Engineering Toolbox link on Reynold's numbers.

At full flow, I'm pushing about 180 gallons/minute through 16 of those flow straighteners. Each has an internal diameter of 15.3 cm, so that the flow rate is 3.85 cm/sec. Plug that into the handy calculator (the one using kinematic viscosity) and you get a Reynold's number of 5213. That's turbulent flow.

At the flow tested in January (which worked properly), I was going up about 33 inches instead of 65 inches, so my jet velocity was 71% of full flow now. Also, the cross section of the jets was .41 inches instead of 0.5 inches as it is now, so that the velocity inside the flow straightener was 48% of what it is now. Plug 1.84 cm/s into that Reynold's number calculator and I get... 2491. That's transient flow, but quite close to the 2300 needed for laminar flow.

If this is really the only problem with the fountain, then I ought to be able to slow down the flow enough to get the Reynold's number down to something around 2300, and see laminar flow at the output. How slow? To get half as much flow, the jet velocity is halved, and the arc height goes to 1/4 of what it is now, or 16.5 inches. In fact, at that velocity, I do indeed get laminar flow:

Note that the impact here is on the first step into the hot tub, which is a little lower than the nominal water surface, and the arc is about 20 inches above the nozzle rather than 16.

The jet is well behaved until it gets to the top of the arc, where the bottom of the jet interferes with the top of the jet, and the result is that is spreads out laterally. That lateral spread then turns into an oscillation in the flow until it hits the step.

Anya demonstrates that the jet is 18 inches above the bond beam, or about 20 inches above the nozzle.

At this point the default setting for the fountain is to throttle back to 40 inches throw height, which clears the occupants of the hot tub and isn't too noisy.

If we wanted to get the tall jets to behave properly, it appears we'd need to cut the flow rate approximately in half, which means we'd have to reduce the jet diameter to 0.350 inches instead of 0.500 as it is now (so the finished hole diameter would be 0.440 inches). That means I'd have to pull the stainless steel nozzles (recall they are epoxied into the PVC heads right now), get new nozzle made (probably $300), and epoxy them back in. That all sounds possible, and certainly cheap enough, and probably can be done fast enough given that it's going to take 5 weeks to get the tile delivered.

However, there's a good chance I'd just destroy the PVC heads in the process, and there is also a good chance I'd get the nozzles glued back in crooked. I don't think we're going to try.

We're getting more comfortable with how it looks.

Camera Guy at work

2009-06-04T14:09:00.001-07:00

One of the nice things about working here is that when we need stuff, we get it.

Fountain test

2009-05-31T13:58:00.000-07:00

Belle, non? (1/80 sec exposure)

Non. (1/4000 sec exposure)

Here it is with Martha for a sense of scale:

First, what went right?

The geometry is right. In this spreadsheet, I calculated the height of the fountain (69.4 inches, was actually 65.5 inches), and how far it would throw the water, and where the jets would come down into the hot tub. Although some of the jets land about 5 inches off where I expected, and two jets collide in midair just before they hit the water, the geometry is about as good as can be expected, and fulfills my goals, which were:
- It should be possible to walk between the rising jets without being hit by them.
- It should be possible to sit in the hot tub without being hit by the jets.
- It should be possible for a child to stand in the middle of the hot tub and have the jets come down all around, without actually hitting the child.
All the jets rise to the same altitude, within about half an inch or less, which means the balanced binary tree distribution system with the shorted end terminals worked.
The pump-side pressure stack does not overflow.
The pumps don't cavitate. They are incredibly quiet. You cannot hear them unless you walk over to the pump vault and stand on top of it. Once the lid is installed on the pump vault, I doubt you will hear the pumps even when you are on top of it.

However, the jets are not laminar. Gloppy blobs of water fall into the water and make a dull roar instead of the quiet sizzle that I had wanted. There is enough splashing from the jets entering the water that you wouldn't want that a few inches from your face. The kids love it, of course, because it's loud, fast, and wet, but it's not so great for the adults.

I'm pretty bummed. What happened?

The individual jets were flow tested in January, and this is what they looked like then:

As you can see, the jets were smooth, and landed smoothly and quietly, back in January. Now Martha jokes that if we move the back yard table to the farthest corner of the yard, we can still have a nice conversation.

I'm not entirely sure why there is a difference. Here are possibilities, ranked by my guess of most to least likely.

In January, the heads had no lateral ports in them. In this latest trial, there are two ports in each head, connecting each to the heads on either side. These ports keep the pressure even across all the jets, which makes them shoot to the same altitude. But these ports may also be causing the water to tumble slightly as it passes the edges, and that turbulence may be causing the breakup that I'm seeing.
In January, the heads were surrounded by nothing, and so small amounts of water on top of the heads ran down the sides, away from the jets. Now, the heads sit inside recesses in the gunite. Each head has a small pool of water in it that terminates at the jet. The water in this pool greatly disturbs the jet during startup, but it gets cleared in two or three seconds and then I don't think there is any more water recirculating through that pool and into the jet.
In the January trial, I had an open-topped pressure stack between the pump and the jets. In the production version, I have a stack after the pump, but it's not quite the same. In this one, the water from the pumps goes to a Tee. In one direction, the water heads for the jets, and in the other direction, the water heads for the stack. It's possible this alternate arrangement works less well.
This test has a closed air volume right before the jet, which was intended to be an additional flow smoothing device. The January arrangement used open-topped pressure stacks either right before each flow straightener, or right after the pump, and both worked well. The closed air volume is known not to work as well (since the pressure changes more with a small surge in water). Also, since the current arrangement has two capacitors with an inductor between, it's possible that there is oscillating pressure being stored between the two capacitors.
The nozzle holes are 0.590 inches, rather than the 0.500 inch holes that I tested in January. This makes the jet diameters about 0.500 inches, which is necessary for all 200 gallons/minute to flow. As a result of the larger jet and the larger jet velocity, the flow through the flow straightener is perhaps twice as fast as it was in January. It would be great if this were the problem, since I can reduce the flow later when I have that plumbing finished.
In January, the pump had air in the lint basket bowl, and the pump could be heard continually injesting air. Now the pumps have no air in their lint basket bowls. I would expect this to make things better now, but I thought I'd list it because it is a difference.

I also have two unexpected observations which may be a clue to a solution if I can figure it out:

The ports in the sides of the fountain heads are connected via riser pipes to a plenum that is fed from a pipe that will ordinarily lead to a blocked valve. This valve is used when the fountain is off to backflush the flow straighteners. However, that plumbing is not yet finished, and so the pipe currently leads to many other pipes that are currently filled with air. There is also a hose bib and a pressure gauge connected to those pipes (this is how we did the pressure test). I have calculated that the static pressure at the top of those fountain heads is about 3 psi above ambient, and so I expected the plenum to be pressurized at 3 psi.

But that's not what the gauge says. The gauge shows zero pressure (I don't have any gauges that show negative pressures). If I open the hose bib while the fountain is running, then cover the opening with my finger, I feel a little pull. It's very feeble, but it's there. WTF?

The flow in the head is moving at 1.6 inches/second, and I calculate a dynamic pressure of 0.85 Pascals, or 0.00012 psi. That isn't diddly compared to 3 psi pushing out.

[Update: Mystery retired: it turns out that the pipe connected to the top manifold is capped off right now, and those other pipes are just not connected to the fountain. I can't explain why I was thinking that there was a small pull of air, but it certainly wasn't measureable.]

The second unexpected thing happened the first time I started up two of the three fountain pumps. All three pumps are in parallel. I had difficulty taking the lid off the third pump's lint basket bowl, so I had left that bowl filled with air, and just started the other two (which were properly filled with water). I expected the first two pumps to push water backwards through the third pump, flushing the air into the intakes of the first two, where it would be blown into the fountain or otherwise ejected from the system.

Nope. There was no noticeable flow through that third pump. Later, I pulled that lid off and removed the air. When I ran just two pumps again, the third pump did have flow going backwards, and in fact the impeller was turning backwards at perhaps half the RPM of the two powered pumps.

It's not clear to me how the air can block a >3 psi pressure drop. The total drop from the top of the pump to the bottom of any associated piping is perhaps two feet, which would account for a 1 psi drop block, but not 3.

I suspect that the solution to these mysteries, especially the first, will tell me something about the fountain behavior.

Relative safety of stairs and swimming pools

2009-05-29T08:22:00.000-07:00

[Post updated: A friend called BS on my previous estimate of the number of houses falling into the CPSC's "Stairs, Ramps, Landings, Floors" category, so I've fixed that. The change affects the magnitude but not the polarity of the bottom line.]

As we're finishing up our swimming pool, my wife and mother-in-law and I were naturally led in a recent dinner conversation to consider whether the pool is dangerous. This is, of course, an ill-posed question.

So I changed the discussion to which of the stairs or pool was more dangerous. The stairs typify a common threat which which everyone is familiar. The pool typifies a threat for which there is plenty of hype.

I was able to remember the gist but not the exact numbers in my previous blog post on this subject. Now see, there's the value of my blog (I knew it was going to pay off someday!) -- I have a nicely written set of notes available online to which to refer. Sadly, I had not completely anticipated my mother-in-law's argument, so here's an update:

There are 8.6 million swimming pools in the United States, and 116 million homes. If we make an approximation that all those swimming pools are residential, 5322 deaths/year for 8.6 million residential pools is 62 deaths/year per 100,000 houses with swimming pools.

I'll assume that essentially all houses have stairs, ramps, landings, or [more than one] floor. That means the 202,104 deaths/year for 116 million homes equates to 174 deaths/year per 100,000 houses.

Since we have both a pool and staircases, my best estimate is that our stairs are 2.8 times more likely to kill someone than our pool.

The difference may be substantially larger. Our pool will have modern safety features like an automatic safety cover, parallel separated drains, and a properly engineered diving envelope for the diving board, along with a raised-periphery design that makes snapping your neck on the bottom at least very awkward.

Our stairs, on the other hand, are very much like stairs everywhere, and thus should be about as risky. I suspect that a disproportionate number of "Stairs, Ramps, Landings, Floors" fatalities are concentrated in the portion of houses with actual staircases, and so my estimate above understates our staircase risk. The two most used of our three staircases have turns part-way down, which I think makes them marginally safer since you are less likely to fall all the way down the flight, but I doubt that affects the polarity of my argument.

Bottom line: no, I'm not worried about the safety of my kids around the pool, but I have gotten noticeably more nervous about the stairs since running these numbers.

Laminar Fun Group

2009-05-22T08:05:00.000-07:00

If anyone reading this is looking for help building a laminar flow fountain, let me know. I now have a business: Laminar Fun Group. Reach me at laminarfun@mcclatchie.com.

Too Big Has Failed

2009-05-21T08:03:00.000-07:00

I've been wrestling with writing a blog post on how I think we should fix the financial mess. Happily, it turns out that Thomas Hoenig has written it for me. Whew!

Mr. Hoenig points out a basic problem we have now:

If an institution's management has failed the test of the marketplace, these managers should be replaced. They should not be given public funds and then micro-managed, as we are now doing under TARP, with a set of political strings attached.

He reviews past financial crises and the mechanisms used to successfully deal with them:

financial crises continue to occur for the same reasons as always -- over-optimism, excessive debt and leverage ratios, and misguided incentives and perspectives -- and our solutions must continue to address these basic problems.

Then he points out flaws in the existing TARP mechanisms, that can be fixed by using the procedures that were used before. That is, establish a simple metric for declaring a financial institution insolvent, fire the management of insolvent institutions, bring in new management, allocate losses to shareholders first, and then to unsecured lienholders, and take out all or a portion of the bad assets for seperate disposal. This isn't new thinking; Mr. Hoenig is just saying we should do it now even though the failing institutions include the largest US banks (you know who you are, Citibank!)

Finally, he looks forward to avoiding our current problems in the future:

One other point in resolving "too big to fail" institutions is that public authorities should take care not to worsten our exposure to such institutions going forward. In fact, for failed institutions that have proved too big or too complex to manage well, steps must be taken to break up their operations and sell them off in more manageable pieces. We must also look for other ways to limit the creation and growth of firms that might be considered "too big to fail".

The underlying problem is that when a single entity or network grows to become vital to taxpayer interests, that entity achieves a claim on taxpayer resources. Firms should have to pay for such a claim. Many will find it cheaper to break themselves up. Identification of networks vital to taxpayer interests is an extension of existing antitrust laws.

Mr. Hoenig is the president of the Federal Reserve Bank of Kansas City.

Financial Times opinion piece:

http://www.ft.com/cms/s/0/46e2f784-380b-11de-9211-00144feabdc0.html?nclick_check=1

Fed White Paper

http://www.kc.frb.org/speechbio/hoenigpdf/omaha.03.06.09.pdf

Let me add one thing:

One problem any kind of government takeover and cleanup of a failing bank incurs is that the new entity is unnaturally "clean" compared to the non-failing banks with which it competes. Folks like Warren Buffet complain that they are penalized for having played well.

First, the complaint isn't entirely true. As long as the shareholders of the failed institutions get wiped out, the shareholders of non-failing institutions do better in comparison, and so to the extent that shareholders guide bank operations in the future, they will tend to guide away from failure.

The complaint is true, however, for the individuals at the failing banks. Folks working at Citibank and AIG have made more money than folks working at less spectacular non-failing banks, and they've kept their undeserved gains. I think we need a better system for aligning the interests of bank shareholders and those who work at banks. It's not enough to give the folks working at the banks options or shares, because shareholders do not have enough power right now.

Gunite is in

2009-05-02T14:37:00.000-07:00

Kathleen is spraying water on the gunite, Anya is directing, while Ava looks on. We're supposed to keep the gunite wet for the next two weeks.

I stayed home for the day to watch the crew shoot the gunite. We used Aqua Gunite (here is their web site), on the recommendation of our consulting engineer Charlie Adams. I found a listing for them here. It's listed as a two-person company, which I suppose would be Jose Aguayo and Sergio Garcia. For a two-person company this place has a lot of assets: at one point I saw three and my neighbor reports five trucks lined up to deliver the sand/cement mix. Those trucks had Aqua Gunite logos and Charlie tells me they cost $260k each. They also had what my friend Wes Grass reports to be the largest air compressor he's even seen (it was all of a large truck). Maybe the company is owned by those two guys.

They got here at 7:30AM and had the gunite going by maybe 8:00AM. That gun was shooting almost continuously until something like 5:45PM, and it took them another 30 minutes after that to finish up. We used almost five truckloads of gunite (our pool is 46 feet by 18 feet, and has a big cover vault at one end). Sergio, the foreman, told me that was 78 to 80 cubic yards of gunite, but I can't see how that's possible:

The shell surface area is 2015 square feet that average around 8.5 inches thick (53 yards^3).
We have about 38 feet of internal dam walls that are about a foot thick and average 4 feet tall (5.6 yards^3).
There is maybe 3 cubic yards of gunite in the steps and two pedestals.
We have a gusset which holds up the diving board that is 2 feet by 2 feet by 6 feet, so that's another yard.
10% rebound would be another 6 yards, which is consistent with what I observed getting dumped and hauled away.
Total: 68 cubic yards.

Those trucks were claimed to hold 15 cubic yards, but they just did not look big enough. Maybe that's the volume of the containers, which they perhaps don't usually fill completely. For comparison, a 10-wheeler holds 10 cubic yards.

The cement and sand is mixed in the truck right before delivery, and the water is only added in the nozzle at the end. As a result, they don't have the usual concrete problem of having to order exactly the right amount of mix. Instead, they have the problem of disposing of "rebound", which is the portion of the stream that does not stick when it hits the wall. Sergio says they usually have 7 to 10% rebound. Aqua Gunite carefully arranges not to have the capability to offhaul the rebound -- they want to dispose of it somewhere on site. We had a nice big hole in which to dump 2 or 3 cubic yards, but after that we piled it up on what used to be our lawn and had some other folks cart it off for recycling the next day. In retrospect it probably would have been a good idea to negotiate this ahead of time with Jose.

It doesn't much matter, we had a fixed-price contract: $13145, $733 of which was for using thicker masonite so that we wouldn't have to strip the forms to make the form edge straight. This last bit is an artifact of our having a bond beam raised 15 inches out of the ground -- the sides have to be straight so that the masons can lay the siding stone properly.

One of the first things Sergio decided when he got here is that we didn't have enough rebar in the cover vault dam wall. The wall is 12 inches thick, and had just a single curtain of #3 rebar on 12 inch centers on the water side, plus four #4 rebar at the top. Sergio added another curtain of #3 rebar on 12 inch centers on the vault side. One nice side effect is that this will make the vault floor even more resistant to cracking from the applied torque should the gravel under the pool settle and leave the pool hanging on the soil under the cover vault.

Here's the top of the gusset that holds up the diving board. You can see the four two-foot bolts that actually go up to the diving board base. In retrospect, I should have had the gusset rebar tied into the vault wall rebar better, as that would help transmit loads between the two.

So now we wait four weeks for the gunite to harden, and shrink, and maybe crack, while we race to get the plumbing, electrical, and solar installations finished, and get the trenches closed up and filled in preparation for the new landscaping. In the meantime, the maintenance crew is keeping the shell wet.

Ready for gunite

2009-04-26T23:14:00.000-07:00

We passed our plumbing inspection, so we're ready for gunite. This has been the eighth weekend in a row that I've worked both days on the pool plumbing. Virtually all of that work has been on the hot tub. (Earlier I was working on plumbing too, but I was machining bits and it didn't feel as much like plumbing.)

Picture right is David Kanter, by the way, who was generous enough to come down last weekend and sweat in the 100 degree noontime sun to lay gravel in the trenches around the pool. This is us right before cutting those 3" pipes to make the main drains. Thanks, Dave!

I like this picture because it gives a sense of the scale of this thing. Granted, it will be a smaller hole once 6 to 15 inches of gunite have gone into the sides, and 10 inches has gone into the bottom. But it will still be big enough that, standing on the bottom with no water to buoy you, you will not be able to jump up and touch a string suspended across the waterline. It's significantly deeper than most rooms are tall.

After looking at this thing, the inspector asked me to double the rebar in the hot tub because of all the plumbing. Done in two hours. I'll post an updated pic of the hot tub shortly. [Update: the spa dam wall has a small circumferential crack. Not a big problem, but in retrospect I should have inserted rebar that stitched the inside curtain to the outside curtain.]

We tested a fair bit of the hot tub plumbing to 30 psi, and I was amazed that it held. Most of my flexPVC is tested now, and not a single leak.

Unfortunately, the Valterra 4 inch gate valve on the suction side of the fountain pumps leaks. This is an expensive part, and after talking with the manufacturer it seems that it was never going to work right. Finding an alternative is going to be very expensive. If any reader happens to know of a 4 inch valve made of something compatible with ozone (stainless steel, especially 316, and PVC are the big ones) which won't rust and leave stains on my plaster, and which doesn't have a huge flange... please pass along the info. Oh, and it should take 30 psi of internal pressure without leaking. It doesn't have to take 30 psi across the ports when closed, but 3 would be good.

[Update: I've ordered a 4 inch Spears PVC ball valve. It's a very nice valve, very, very easy to turn, but it was crazy expensive: $670, probably $750 after installation. Including the built-to-fail Valterra gate valve and installation and rip-out of that, this one item has cost $1000. This could have been done more cost-effectively.]

It is now conceivable that we could have the pool open by June 5 (Anya's birthday), but I don't think it's going to happen. Every other aspect of this pool has taken much longer than expected, so I assume that it will be hard to just finish the plumbing over the next four weekends, let alone get the tile, plaster, cover, coping, electrical, solar panels, diving board, rock facing, patio, drainage, lighting, planting, and sprinklers done.

Chickens

2009-04-16T08:00:00.000-07:00

I'm amazed by our hens' abilities to eat.

I weigh 215 pounds, and eat something like 2700 calories a day, including about 150 grams of protein. So, about 22% of my calories are protein. Those are rough guesses, not measurements.

Our hens each lay one egg a day, with around 6 grams of protein. I'm going to guess that they must eat 24 grams of protein to deliver those 6 grams, and also run around the yard and make lots of feathers. 24 grams is about 1/6 of what I eat.

The hens eat grass, cornmeal, random bugs that they find, and snails. (Martha has found no snails at all in the last year in the back yard, but clears 10-20 every week from the front.) I don't think their diet is particularly higher in protein than mine. In particular, their cornmeal is almost identical. So, each hen must each 1/6 of the calories I eat.

These animals weigh 5 pounds! (Anya just weighed them.) Per pound, they eat seven times as much as I do. Since I spend at least an hour a day eating, it's no wonder that those hens spend every waking minute pecking at something.

National Organization for Marriage

2009-04-10T00:02:00.000-07:00

I left a note on the National Organization for Marriage blog that I wrote carefully, in response to their ad. Here it is:

One of the big problems I see is that when kids are taught that it’s okay for other people to marry anyone they want, they naturally apply that same logic to themselves. So teaching tolerance can end up advocating homosexuality. The big message of this ad is that gays aren’t just asking for tolerance any more, but instead want to evangelize their lifestyle in a (manditory) public venue.

I think the really scary thing happening in school is that we don’t have full control over the values that our kids develop. Some of them, exposed to a message of tolerance, are going to go past that tolerance and experiment with a homosexual lifestyle, against the wishes of their parents. It’s plenty hard just teaching kids the basics, like a sense of justice and fair play. State mandated messages in school open a can of worms that would probably be easier to deal with a few years later when the kids are adults and have their value systems more fully formed.

If we’re going to be teaching tolerance to the children of people of some faiths, who believe that homosexuality is an abomination, then we need to get the message in school clear that, while homosexuality should be tolerated and is part of the “normal” spectrum of human behavior in the larger world, it is NOT acceptable and NOT normal if you are going to be a member of these faiths. Then at least the kids can wrestle directly with the issue that their parent’s faith requires a stricter set of behavior than society at large does. That leads to questions of faith which can then be directed to a priest, elder, etc.

Theodore,

About the marriage license thing: you are part of many groups. Some large, like your state, which grants marriage licenses. Some less inclusive, like your faith. The norms of the more inclusive groups have to be broader. That’s why your faith can say no to homosexuality while your state may say okay. Since lots of people get married in a church, they tend to think of marriage as being something granted by the church. But that hasn’t been true for a long time. As my pastor pointed out, I was legally married to my wife BEFORE we got to church, just by the process of getting a marriage license.

Lighten up about the imprimatur of your approval. If people want to know how you feel about homosexuality they’ll look to your faith before they look to your state, and that’ll be clear enough.

Fountain update: flexPVC limitations

2009-03-29T23:14:00.001-07:00

My dad came down today, and we got a lot done.

2.5 of the 3 lower manifolds are now complete, and the fountain plumbing is now good enough for the pool rebar to be installed. This is great news because it means I am nearly released from the critical path and we can go from having one amateur working two days a week to maybe three or four professionals working 5 days a week. I expect a speedup of at least 7 times!

The bottom manifolds are made of flexible PVC pipe. This stuff is made with two different plastic formulations coextruded. The first is rigid white PVC, just like regular pipes are made of, which is formed into a spiral. The seconds is flexible PVC (with Phthalate mixed in for flexibility), which fills the gaps between the coils. This stuff is a little tricky to work with.

The first problem is that the pipe arrives in coils. By the time you get it, the stuff has achieved something of a permanent bend. I was able to take most of this out by unwinding the stuff down the middle of the pool, where it got hot in the sun for a week.

I have not determined a good way to cut the flexPVC. I'm using my miter saw to cut my pipe, because it makes such nice clear burr-free cuts on the regular PVC pipe. On the flexible stuff it leaves a hot, smoking cut with lots of burrs that I clean up with a knife. The Phthalate is particularly annoying, because our chickens love to eat the PVC chips from the saw, and we eat the chicken eggs, and phthalate is bad stuff. So, the chickens are cooped up on days when I'm cutting flexPVC, and I vacuum up everything afterwards.

We're also having difficulty just measuring the stuff. Somehow we're making lot of mistakes where we measure, cut, and then find that it's not the right length. I think the basic issue is that we're trying to measure curved paths with a tape measure.

Joints are a little scary with the flexPVC pipe. I had a professional plumber recommend that we encase every flexible PVC pipe joint in concrete. Now that I've done a bunch, I agree. If there is any bending load on the joint when it's made, the pipe sits in the socket at an angle, and in a few of those joints I can feel that the PVC glue has not completely filled the space between pipe and socket. I made most of the joints with no load while it was curing, and let them sit for at least a day before putting load on them. Those joints I'm quite comfortable with.

Dad points out that if I have a few leakers, the leak rate will be very low due to the concrete barrier and very low pressure in the system (3-6 psi). The plan is to pressure test before gunite, but that is going to be hard to pull off. I'm concerned I'm going to have leaks in the plastic membrane which collects the water, and this will hide any leaks in the piping.

Quick post: Credit Crisis Explained

2009-03-25T15:01:00.000-07:00

Great 10 minute animation explaining the credit crisis:

http://vimeo.com/3261363

Zubrin's Plan

2009-03-22T23:00:00.000-07:00

Energy plans are like ..., well, everybody's got one. Today I'll be looking at Zubrin's plan, as presented by Anne Korin. Check out her youtube presentation.

Anne likes Robert Zubrin's plan of making lots of ethanol from corn or sugar, and using that instead of oil to run our cars. Digging below the surface, the bottom line is that in 2008 we used 42% of our corn crop to reduce oil imports by 3.7%. So, we aren't going to replace a substantial amount of oil imports this way. But Anne didn't get into that aspect.

Anne's politics are certainly different than mine. She likes to talk about having little or no government, and letting the free market work. At the same time, the present crisis is so very bad, and OPEC is removing freedom from the oil market, so she says we need the government to fix it. Okay, so she's libertarian except when things are bad. A governing system that only works in good cases doesn't sound very robust to me, but that's not really the point of this blog post.

Another issue I have with her otherwise excellent presentation is that I don't follow how OPEC, which controls about half of the oil supply, can remove freedom from the market. You can read a detailed analysis at WTRG Economics which suggests that OPEC does not have even rough pricing control.

But I think this is just her ideology, and I don't care about that so much. What is more interesting is her presentation of Zubrin's plan (unattributed) for fixing our balance of trade / economic insecurity problem.

The basic idea in the Zubrin plan is to mandate that all cars sold in the US accept both alcohol and gasoline fuels. This change can be applied to all cars sold within a couple of years because it does not require large changes by auto manufacturers (contrast with hybrids, or plug-in hybrids, which have a much longer and more expensive adoption curve). Having made that change, within a few years a substantial number of consumers will be able to use high-alcohol-content fuels.. When alcohol is cheaper than gas, gas stations will offer alcohol, and so consumers will have an economic alternative to gasoline.

We can make alcohol from corn or coal, or we can import alcohol fuel. There are a lot of hazy details: corn-ethanol may be soaking up so much corn that we're starving people to death worldwide, corn may be crowding out the use of land for food, and it may be impossible to grow enough corn to matter.

The flex-fuel vehicle part sounds really good. There are a few other details which sound really good to me as well:

Eliminate the tax on imported ethanol, so that it competes with imported oil (which has no tax).
Eliminate the tax on imported sugar. Sugar cane is supposed to be a better feedstock for ethanol production than corn.

In the presentation above, one of the audience members asks if ethanol from corn replaces more oil than it consumes. Anne says yes, and it appears she is right. Here's a study of corn-ethanol production efficiency:

Each BTU of corn-ethanol produced in the U.S. requires an average of 0.14 BTU of gasoline, diesel and fuel oil.
This factor does not support the conclusion at the top of the study, that each gallon of ethanol displaces 7 gallons of imported oil.
Correcting for the energy density of ethanol and gasoline, each gallon of ethanol produced domestically displaces 0.57 gallons of imported gasoline.
The U.S. produced 13 billion gallons of ethanol in 2008, which displaced 7.36 billion gallons of gasoline, and reduced oil imports by 167 million barrels. We imported 4.39 billion barrels over the same period, so the oil imports reduction was 3.7%.
The U.S. used 5.1 billion bushels of corn in 2008 to make that ethanol, which was 42% of the total of 12.3 billion bushels grown that year.

Bottom line: we aren't going to displace more than, say, 10% of our oil imports in the future by using corn ethanol. There just isn't enough corn.

The reason the question gets asked is that there is a different issue: does making corn ethanol yield more fuel energy than fossil fuel energy used? The answer here is: it's close. When you make ethanol, you make electricity along with it. When you add in the energy value of the coproducts, a little more energy comes out than fossil fuel energy went in (this energy was supplied by the sun).

So, the right way to think of ethanol production is as a coal-to-liquids system. It has the consequence of increasing the total amount of carbon dioxide emitted for a given amount of energy delivered to the automobile.

Fountain Progress

2009-03-19T02:43:00.001-07:00

Here is the current state of the fountain. I have it installed in the pool, with the central fixture glued in place. The flow straighteners and the first level of distribution to them is in place. In this picture, I'm holding the original prototype for the fountain. It was going to be a piece of cake, I promised. One other note: the inside diameter of the dam wall will be 6 feet 11 inches. The tub looks a little small in this picture. It doesn't seem small in real life, I think the distortion is because I'm slightly in front of the tub and Martha is shooting with a 35mm (wide angle) lens.
Here is my SolidWorks model of the same thing. It's not quite right, in that the rotation of the wooden fixture in the middle is off, and the risers which feed the upper cross pipes are not all in place in the physical object. Ryan and Wes from work stopped by on Saturday to help with the lift. I had built half the fountain in the garage, which was around 250 pounds of stiff, delicate stuff that had to be hauled out to the back yard and levelled. Having an extra pair of critical eyes was very helpful.
Here's the next step (next weekend). I'm going to add the risers for the usual jets that a hot tub has. In this case, there are two kinds: one that comes from the main pool pump, which has enough pressure to pick up bubbles through a venturi, and the other that comes from the fountain pumps, which I don't think will have enough pressure for the venturis (so, no bubbles).
After that, the risers all get tied together at the bottom with a set of three manifolds. The main pool pump drives into the outer one when I want to backflush the flow straighteners. The same pump drives into the center one when I want bubble jets in the spa. The fountain pumps drive into the inner one to whatever extent is necessary to trim the fountains to the right amount of flow.
Finally, before I can do any of the plumbing for the spa drains and major hookups, the fixture has to be sawed out. Here is what it will look like then.

The guys at work are calling it my nuclear reactor.

Thanks, Ryan and Wes!

Sanctity of Contracts

2009-03-16T17:41:00.000-07:00

Over the last few years, AIG sold insurance against defaults on mortgage back securities. They sold huge amounts of this insurance, at low prices. Those insurance contracts call for AIG to post bonds which show the ability for AIG to pay, should it's credit rating drop.

Now, because it is supposedly in the U.S. taxpayer's interest that the folks who bought this insurance not suffer any loss, our bailout money is being used to post those bonds. Furthermore, the people at AIG who misestimated the likelihood of defaults on mortgages, and thus mispriced the insurance, are being paid huge bonuses, again with my money.

AIG's position is that both the bonds and the bonuses are required to be paid by contracts that AIG signed. Those contracts cannot be abrogated.

Complete crap. Those contracts can't be abrogated by AIG. There is no such contractual obligation on the U.S. government. AIG is failing. If we let it fail, part of the bankruptcy proceedings will be that some entity, possibly the government, will purchase some portion of the assets. They make take on some of the liabilities if they so choose, as well. So, during the bankruptcy proceeding, the government can negotiate with the folks who have claims on AIG's assets to determine what percentage, if any, of those liabilities the government chooses to fulfill.

Since every serious person involved understands this already, the government can renegotiate those credit default swaps even without AIG going bankrupt. This is called a workout, and it happens between creditors and debtors all the time. If the debtors don't like the proposed workout, they can force the company into bankruptcy.

As part of this workout, we can reduce the bonuses to the folks that sold the credit default swaps to zero. If this causes them to be unable to afford their current homes, that is karmic justice. My guess is that if outraged AIG salespeople attempt to recover a portion of their bonuses by forcing AIG into bankruptcy, they'll be either shot down by a reasonable judge, or just lynched.

Fountain Basics

2009-02-25T23:14:00.001-08:00

This post is a response to Jim. Jim has several 0.125" diameter hoses that he cut with a clean edge, and supplied with pressure from a garden hose. His fountains shoot up to their apex, then break up into a gloppy mess, just like mine used to, but for a different reason.

There are three, well, no, six things you need to make a laminar stream work:

Accelerate the water to high speed without producing a lower-speed boundary layer. After the water exits the nozzle, internal shear will accelerate the boundary layer back up to the speed of the jet, and the shear will then be redistributed through the jet as turbulence, which will then lead to breakup. I know of two ways to minimize the boundary layer:
- Large diameter tube ending in a flat plate with a small diameter hole. This design minimizes the distance over which the water is both at high speed and in contact with the wall. There will be a boundary layer, but it'll be really thin. The downside is that you end up with plumbing behind the jet which is really bulky compared to the jet.
- Form the jet first, then use a circular knife to cut the boundary layer off the main flow before the boundary re-accelerates. This is how firehose nozzles work. They take the water stripped off and reintroduce it to the stream with a venturi. This nozzle is less bulky but needs a bigger pressure drop and is more difficult to make.
- I found that water beads up on my 316 stainless nozzle more than on my PVC pipe. It's possible that the 316 doesn't drag on the water quite as much as PVC would have, although I can't confirm that.
Remove all vorticity from the water.
- The problem is that angular momentum is conserved, and angular momentum is (mass)*(tangential velocity)*(radius). When you constrict a flow from 6" diameter to 0.5" diameter, the velocity increases by a factor of 12x, which means the centripetal force increases by 12^3 = 1728x (that's right, v^2/r). If my 6 inch flow starts out at 3 RPM (20 seconds to turn once, barely turning), then the half-inch jet will be rotating at an average of 432 RPM, and the centripetal force at the surface will be 13 m/s^2, which is more than 1 G. Since 1 G will rip drops of water off the underside of a wet object when the water is much less than a half inch thick, it's no surprise that this rotation will rip apart a half-inch diameter stream.
- A long, narrow nozzle should take out vorticity through friction with the nozzle walls. The same friction will lead to lots of turbulence. I have no idea why this turbulence is not a problem for the firehose nozzle. I did some experiments with a watering can that we have which features a nozzle about 12" long and 1/3" diameter, and found that the stream would travel about 3 feet before it broke up.
- If you do the large-diameter, hole-with-flat-plate nozzle, then you have to remove the vorticity some other way. I did it with layers of twin-wall polycarbonate, cut on a table saw, epoxied into place. In this YouTube video, they do it with soda straws. I've read that the minimum length needs to be 12x diameter. My flow straighteners are 1 foot long, and have channels 7mm across, so the ratio is 43:1. Probably overkill.
Eliminate even minute variations in your water flow.
- You'd think a hose bib would give you smooth water flow, but it doesn't. I know because my fountains shot blobs of water with direct pressure from a hose bib, but worked fine once I put an LC filter between the hose and the fountain. The YouTube video mentions the same problem in passing, but doesn't say how to fix it. Directly connecting my pump led to blobs, the LC fixed them too. (My hose bib has 200 feet of 1/2" copper pipe leading to it, so I'm astonished that any flow variations were getting through. My best explanation is that the copper pipe is elastic, and the resulting distributed capacitance combined with the pipe inductance is forming a transmission line.)
- The filter is simple: you have a run of smallish diameter pipe (that's your inductor, 20 feet of 4x your jet diameter should do), and a Tee fitting going to a vertical pipe into which the water can expand momentarily (your capacitor). My expansion pipe rises higher than my fountain jets, and is open to the air, so that it acts as a pressure regulator as well. I found that the water from my pump in my 2" PVC pipe would flutter irregularly perhaps 1/4" up and down. You can also do it with a closed pipe that traps air above it, if you can figure out how to ensure there is air up there. So long as you don't introduce bubbles into the stream, the closed pipe should work better because it has a smaller column of water between the pressure source (air) and the flow. That column acts like an inductor which would tend to isolate the capacitor and limit its high-frequency response.
- If the source of variation is turbulence in the fountain, then you'd want the capacitor close to the fountain, and the inductor between that and the supply (hose). If the source of variation is the supply, then you'd want the capacitor at the supply, followed by the inductor going to the fountain. When filtering power into sensitive analog electronics, we use "pi" networks, which are just a capacitor at both ends of an inductor, basically because the noise could be coming from both places and we are hedging our bets.
Get rid of all air bubbles. Even tiny bubbles cause major flow disruptions. I have my pumps below grade, so that the water pressure at their intakes should be either above air pressure or very close to it. This should eliminate air leaks past the O ring on the strainer basket cover, which I think was a source of bubbles in my last pool. The strainer baskets always seem to have a little air pocket at the top.
Don't go straight up. I may have screwed this one up. My jet angle is just 12 degrees off vertical (here are my calculations), so that the jets slow from 19.7 feet/second at the nozzle to 4.1 feet/second at the apex. The extra flight time and variation in velocity give the flow more opportunity to glob up.
Filter the water. I may have screwed this one up as well. I wanted to have low power pumps (700 watts total) push a lot of water (200 gallons/minute), which means very low pressure head (10 feet or 4.3 psi). No filter that I know how to buy has ports larger than 2 inches, so any standard filter would have a very high pressure drop. So instead I have 7mm holes in my flow straightener, and .590" holes for my nozzles, and I'm hoping to catch anything even nearly that size in the strainer baskets of the pumps. I also have the ability to backwash my flow straighteners using filtered water from the main pool pump, which can crank up to 3.5 horsepower if needed.

Okay, so Jim, here's your problem: those presumably short hose segments are making a big boundary layer in your jet, so when it slows down near the apex there is plenty of time and turbulence to glob up. The problem is worse because the jets are just 1/8" diameter, so the boundary layer may be the entire diameter of the jet. You need to pick a different, bigger nozzle. I can recommend the flat plate nozzle, and the YouTube video above shows you how to do it cheaply. You are also going to need to smooth out the water supply from the hose, and the LC filter described above should do that at low cost.

Good luck, and please let me know how it goes! If you can, post pictures of the flow at 1/1000 second exposure or faster (full sunlight with any camera will work great).

Wider blog posts

2009-02-09T10:56:00.001-08:00

I have no idea why the standard blogger entries are so skinny. Maybe they want to be compatible with cell phone users.

I got fed up with the skinniness, and expanded the format using the instructions provided here. Thanks, IDS.

-Iain

Fountain update

2009-02-09T09:12:00.000-08:00

In the previous update I flow tested a pair of fountain units. Those units were just about in final form, except that they were simply dry-fit together (not glued), and they did not have their side ports yet.

The top of each unit has a 2" pipe going to the units on either side. During fountain operation, these ports carry very little flow, but they ensure that there is equal pressure behind every nozzle, so that all the fountains will throw the same distance. If I did not short them in this way, I would either need some sort of adjustable trim system to vary the flow from each of the nozzles, or I would need to ensure that the distribution system has exactly the same resistance to flow to each fountain unit. I've done my best at the latter, but this is a one-of-a-kind design, so lots of margin is good.

Indeed, if there is any substantial flow through the side ports during normal operation, the lateral momentum of the flow will probably lead to some spin to the water leaving the nozzle, which will destroy the laminar flow.

The flow straighteners in each unit act as a strainer which will tend to accumulate crud. Most laminar flow fountains avoid this problem by running filtered water through the fountain. The trouble with that idea is that it requires a large amount of energy (or a very bulky filter system) to supply all that filtered water. Instead, I'm going to let the debris accumulate on the flow straighteners, and then backwash those every night. That backwash water enters the fountain through these side ports.

The side ports are cut right into the 6" PVC end caps. I bought a 2-3/8" hole saw, which cuts a hole that fits a 2" PVC pipe perfectly. The folks who wrote Schedule 40 clearly anticipated the kind of custom plumbing that I'm doing. I fit the hole saw onto a mill, which I was essentially using as a drill press, albeit one with a 3-axis bed and a tilting head. There were three tricks to this operation:

The hole saw shank is hexagonal, intended for a drill chuck rather than a mill collet. Abe at the Tech Shop put the hole saw on a lathe and turned down the shank to fit a 7/16" collet. This turned out to be tricky because it was hard to get the lathe chuck to grab the hole saw properly. Thanks, Abe.
The PVC end cap has to be held rigidly in the mill while the hole saw is plunged in. I used a vice on the mill bed, which engaged a shoulder which I had previously milled into the head while cutting the holes for the nozzle inserts.
I tilted the head on the mill. Everybody thought this was strange, apparently nobody ever uses this feature of the mill. One of the helpful machinists at the shop suggested it might be easier to machine four sets of custom angle blocks than to re-tram the head. Re-tramming took me 20 minutes, resulting in 0.0005" tilt across 6 inches (about 100 microradians). I have no idea how make or use custom angle blocks.

Final note. Some folks say PVC is hard to machine. Here is my experience:

Cutting white schedule 40 PVC smoothly is really easy. The grey PVC does not cut smoothly. It melts and forms tiny hard balls that stick on the cut surface.
Cutting generates a lot of heat, and you have to take little cuts and then frequently back off to the let the bit cool.
Water soluble oil lubricant works okay, not great.
Simple Green is a terrible lubricant, and ends up increasing heat generation and turning the workpiece into taffy.
Fly cutting is easy, since the chips have an easy exit. Hole sawing is hard, since the chips grind around in there until they melt. I think a compressed air blast would really help here.
The PVC end caps had been solvent welded on the week before. The plugs that I cut out seemed to be welded pretty well, but I did notice that the glue was the first thing that turned to taffy and came pouring out of the cut when things got too hot.
Clamping PVC rigidly enough that it doesn't get popped out of the vice when you use things like boring bars is hard.

After that, I glued up the units. There are 48 6" PVC slip joints in these units. So far I've used about 24 ounces of primer and 30 ounces of PVC cement in doing 40 joints. Big PVC takes a lot of glue.

If this was in focus, you'd be able to see the polycarbonate flow straightener inside the big tube.

Below, the hole saw taking the plunge.

There are two shoulders on the head, parallel to the direction of the tilt of the nozzle. Above, see how the vice clamps on the shoulder on the bottom. Below, a close-up of the shoulder on top.

Fountains, fixed

2009-01-19T13:00:00.000-08:00

Much happier. I now have two unit fountains, operating in parallel, driven from a pump, with a filter that takes out most pressure variations. There is some unsteady flow remaining, which I think is due to bubbles. I have good reason to believe there will not be bubbles in the production pump system for my fountain, so I think the design is now validated.

As a side effect, everyone involved with the testing is now soaking wet. Much of the piping is not actually solvent-welded together right now, so there were the occasional blowouts. Fortunately, we have a blue sky and 75 degree air outside right now, so wet is just fine. If we had a pool, we'd be swimming (ahem).

Here are two unit fountains running at about 60% of design flow. Note the smooth flow. It's splashing a bit when it hits the tub, but that'll go away when it's got more than a half-inch of water to fall into.

Details:

The streams do not quite reach the same height. I'm pretty sure this has to do with a small difference in their pointing angle, so I'm pretty sure they'll all line up when properly installed dead vertical.
When supplying the fountains with water from the hose, pressure variations from the street supply were making their way to the fountain. These were probably low-frequency variations, maybe 1 to 3 hertz.
I considered a surge tank, but the volume required was too large (over 20 gallons). Instead, I have a simple open-topped vertical pipe teed into the line from the pump to the fountain. The pipe only needs to be a few inches taller than the height of the fountain jets. The production system will have perhaps an extra foot or two. You can see the pipe in the foreground.
I tried placing the tee close to the unit fountain, and that worked well, and then I tried placing it next to the pump, and that worked about as well. This result indicates the flow instability comes from the pump and street supply, and not from turbulence within the fountain itself. (Whew!)
The nozzle is a nonlinear resistor, so it was moving the energy from low frequency variations to higher frequency harmonics.
The nozzle is nonlinear because it converts pressure into velocity head with almost perfect efficiency. If you double the pressure, you double the velocity head -- the height to which the water will jump. I confirmed this by varying the flow through the system and noting that the water always jumped to a few inches lower than the water level in the vertical pipe capacitor. A doubling of velocity head means an increase by sqrt(2) of velocity, and flow is (sort-of) proportional to velocity. As a result, flow increases with the square root of pressure.
The nozzle diameter is 0.500 inches, but the flow diameter appears to be 0.410 inches. I didn't expect this. The reason is that the flow at the knife edge is horizontal, and it turns through a radius of 0.045 inches. I suspect that at the higher flow velocity in the production system, the stream diameter will actually decrease.
As a result of the small stream diameter, I'm going to have to throttle back the pumps. The fountain was designed to throw 193 gallons per minute 59 inches horizontally with 16 0.500" diameter streams. Now that the streams are smaller, I'll have to throttle back to 130 gallons per minute, or lower. I'm not too happy about that.
The stream is even more wickedly nonlinear than the nozzle. The principle problem is that slightly faster flow has over a second to catch up to slightly slower flow. The stream goes at about 140 inches/second at the nozzle. So a 1% variation in flow yields a longitudinal variation of over 2 inches by the time impact happens. If that happens in less than 10 inches (more than 14 hertz), you get blobs large enough to cause the stream to turn into drops.

Fountain Ballistics

2009-01-11T11:37:00.000-08:00

There is a common thread among the questions I get at parties:

"How's the fountain coming?"

"Any news on the fountain?"

"Any progress on the fountain?"

or, from Martha, "Are we ready to can this turkey?" Sometimes at parties!

As a public service, I thought I'd post how things are going.

First, you should understand that the pool will have an 8' diameter round hot tub stuck into the otherwise straight side. 16 streams of water will issue from jets embedded in the wall of that hot tub, and land in a small circle in the center. There is a lot of plumbing to make this work, and here is a partial CAD model of it all:

Each of those fat vertical things is a unit fountain, and each contains a diffuser and a flow straightener, and is topped with a head with a nozzle embedded in it.

I've machined the diffusers, cut some flow straighteners, machined the nozzles and heads, and assembled a single unit fountain. I didn't glue it together. I supplied it with water from a hose.

Here's how I machined the head. I started with a 6" PVC end cap, and milled a flat on the end and two shoulders on either side. These are for aligning the side ports to the nozzle later. You'll see.

Then I put it on a Bridgeport mill. Below, you can see that the quill of the machine has been canted 12 degrees over from vertical. This makes the angle that the water jet will come out on, so that it launches from the wall of the hot tub and lands in the hot tub. You can also see the parallel on the two studs in front, which fits against the shoulder I cut earlier. This edge is parallel to the X axis of the mill. So the mill is canted 12 degrees in the plane of this shoulder, which means I can drill holes in the end cap aligned to this nozzle later.

Here's me working the thing. It turns out that lubricant makes everything a lot easier. The Forstner bit was not the best thing to cut this hole with, as I got a lot of heating and chatter. Occasionally the mill would throw chunks of plastic across the room, so the safety glasses were a must.

I cut the diffuser on a ShopBot at the Sawdust Shop, out of 1/4" PVC sheet. The ShopBot is a CNC router. You program the computer to move the router (they call it a spindle because it goes up to 25000 RPM) in 3 axes. Programming isn't too hard -- you use a ShopBot program to convert line drawings (AutoCAD type, I made them in SolidWorks) into tool paths. We wrote some text programs to step and repeat the pattern once we had it properly tweaked.

The table is covered in chips because we didn't run the vacuum. The owner didn't want to mix PVC chips into his sawdust since he uses the sawdust for something.

Result: just after the hose is turned on, it works great. Flow is smooth almost all the way to the end, certainly good enough to be acceptable. Here it is just after startup. Understand that the unit you are looking at will be one of 16 buried in the wall of the hot tub, and the streams will issue from holes cut into the sides of the tiles that cover the top of that wall. So you won't be looking at ugly PVC.

Up to something close to working pressure, and it's holding together pretty well:

However, within a matter of seconds, the flow becomes less smooth, breaks up, and soon I have a gloppy mess at the impact point.

Here's a closeup of the top:

I'm not happy.

Another (minor) problem: I've got a small leak between the nozzle and the endcap, right where the shoulder is thinnest because I've got the flat spot. This is eventually going to be buried in concrete, which will greatly slow the already trivial leakage, but I'm not thrilled about this either. This problem I probably won't fix.

My guess is that I'm getting variations in the flow rate. The fountain is extremely sensitive to these variations -- a 1% change in flow (from 193 to 194.98 gallons/minute) makes a 2.1% change in vertical height and a 2.0% change in horizontal throw. 2% doesn't seem like so much but it's over an inch, for a stream which is around a half-inch in diameter. I think the variations I was seeing were at least an inch of throw, at frequencies from 3 to 10 hertz.

There are two possible reasons I wasn't seeing the variations at first:

Because the hose wasn't fully up to pressure. The hose is not linearly elastic. When I first turn the water on, the hose fills with water, but it doesn't develop any pressure until it sees back pressure from the nozzle. At partial flow through the nozzle, the back pressure is low enough that the hose is quite stretchy, and so it acts as a surge tank and filters flow variations. At full back-pressure (probably just 2-3 psi), the hose has developed it's fully round shape and is considerably stiffer, losing the filter function.
If there is air in the fountain, it will act as a surge filter. If I could figure out a way to insert a tennis-ball-sized flaccid bladder filled with air into the fountain, I'd probably have this problem licked, but I'd need something guaranteed not to leak in 30 years immersion. I don't know what that is.

Obviously I need to figure out exactly what is going on, and how to fix it. I'll post some analysis later.

Tooth Fairy Traffic

2009-01-07T12:56:00.000-08:00

Anya just had a tooth pulled by the dentist. She put it under her pillow but the Tooth Fairy seems to have not made it last night. A few notes:

The Tooth Fairy came on the fourth night after she lost her last tooth. Anya's theory is that the day before she lost that tooth, a little boy lost one of his, but he was sick, and the Tooth Fairy caught a bug when she touched the tooth.
I believe Anya is lying, eyes closed, in tense anticipation of the Tooth Fairy. She was watching Martha and I as we climbed the stairs last night at 1:30AM, and she was wide awake and ready to go at 7:00AM when I got her up this morning.
Little girls, of which I have 3, have 20 baby teeth each. Even discounting the molars, which might come out much later, I can forsee a time when the Tooth Fairy will be making more than one visit per month. With multiple little girls engaging in outright deceit in their attempts to catch the poor fairy, I forsee delays and uncertainty.

I'm not sure if the full-body tension I'm feeling right now is because I'm worried that my contractor won't be able to lay out my circuit board properly, or because the damn house creaks even though it's only six years old. Yeesh!

Santos?

2009-01-01T03:40:00.001-08:00

If you're out there, send me a better email address.

5 Ways to Die During Reentry

2009-01-01T03:34:00.000-08:00

If you haven't already seen it, the Columbia Crew Survival Investigation Report.

During reentry, there is a 10 minute long window of maximum heating. They almost made it through all 10 minutes. Right at the end they lost their hydraulics. Makes me wonder if they could have flown the orbiter at a funny incoming angle to spare the load on the left wing. Maybe they wouldn't have gotten Columbia onto the ground, but if it had broken up five minutes later things might have gone a bit better.

There were 40 seconds after loss of control during which the Columbia pitched up into something like a flat spin, and the folks inside tried to get their hydraulic systems back.

After that, they had a depressurization that took less than 17 seconds and probably, hopefully knocked everyone unconscious. Nobody dropped their visors (which would let their suits handle pressurization). Apparently they were all in "fix the vehicle" mode and not in "survival as long as possible" mode.

After that the cabin seperated from the rest of the vehicle, the crew's shoulder and other restraints mostly didn't work, and they got thrashed to death: fatal trauma to their heads from the insides of their helmets. Owww.

From my reading, had they dropped their visors, gone to suit oxygen, and braced, several of the crew could have made it through both depressurization and cabin separation.

But then the cabin blew apart and they were in their suits in a mach 15 airstream. I didn't actually read this anywhere, but it sounds like most of the suits came off before they hit the ground.

Side note for camera geeks: notice how crappy the home video shots of the breakup look. Then look at the Apache Helicopter shots of the same thing, especially when it zooms in. That chopper has some nice telescopes!

"we want these detainees broken"

2008-12-29T01:03:00.000-08:00

From "SENATE ARMED SERVICES COMMITTEE INQUIRY INTO THE TREATMENT OF DETAINEES IN U.S. CUSTODY":

Former Navy General Counsel Alberto Mora: “there are serving U.S. flag-rank officers who maintain that the first and second identifiable causes of U.S. combat deaths in Iraq – as judged by their effectiveness in recruiting insurgent fighters into combat – are, respectively the symbols of Abu Ghraib and Guantanamo."
Jonathan Fredman, chief counsel to the CIA’s CounterTerrorist Center: "If the detainee dies you’re doing it wrong."
In mid-August 2003, an email from staff at Combined Joint Task Force 7 headquarters in Iraq requested that subordinate units provide input for a “wish list” of interrogation techniques, stated that “the gloves are coming off,” and said “we want these detainees broken.”
JPRA Commander Colonel Randy Moulton’s authorization of SERE instructors, who had no experience in detainee interrogations, to actively participate in Task Force interrogations using SERE resistance training techniques was a serious failure in judgment.
Secretary of Defense Donald Rumsfeld’s authorization of aggressive interrogation techniques for use at Guantanamo Bay was a direct cause of detainee abuse there.

I think at this point I'm just sick of all the damage that has been done to my country by Bush and his team. I doubt that throwing many of them in jail will do much to improve the behavior of similarly-minded people, but I'm all for prosecutions so long as they don't shift attention from the job at hand, which is to fix the economy.

Insulating the pool

2008-12-18T07:35:00.000-08:00

Since this is my first posting about the pool, let me show you around a bit. South is to the left. You can see all along the south side of the pool there is a two-foot-wide shelf. The water over that shelf will be 12 inches deep in the shallow end and 18 inches deep in the deep end. In the middle of the south side you can see where the hot tub will go. At the far end (west), you can see the shelf that will eventually support the automatic cover vault. To the left of the pool, at the far end, you can see the pump vault that will hold the pumps below ground, behind baffles, which should make them completely silent. The top of the wooden form will be about three inches below the coping around the pool, so you can see that the coping is about 18 inches above grade on the near side. That coping will be about 16 inches wide, and will form a sort of bench seat most of the way around the pool. At the far end, the grade level will be raised to match the coping height, which because of the slope of the back yard will only be about six inches.

The blue stuff you are looking at is the 2 inch thick Dow Styrofoam Highload 40 insulation, most of which is glued (yes glued, with polyurethane foam) to the soil behind it. On the bottom of the pool, the insulation sits on 4 inches of crushed drain rock, which sits on a geotextile fabric membrane. The next thing to go into the pit is the plumbing and rebar grid, and after that we shoot gunite.

Heat losses for most pools are dominated by evaporation. We're going to be getting a safety cover, and one of the side effects of these covers is that they are close to vapor-tight. In the summer months, we'll have the cover off most days, but in the spring and late fall we'll keep it closed for most of the day and only open it to go swimming. As a result, I'm expecting evaporative losses to be quite small -- perhaps a half inch a month or so. On our 18x48 foot pool, that's 270 gallons/month. Multiply by 2270 kJ/kg (water's heat of vaporization), and that's 72,000 BTU/day.

Direct heat loss through the cover will be the largest remaining heat loss. The 24-hour average outside temperature in spring is around 60 degrees, and the safety cover will be something like R-1, so loss from a 85 degree pool would be 520,000 BTU/day. During the early spring and late fall, we'll probably lower this loss by putting a bubble-type cover over the safety cover. (I wasn't able to find an automatic safety cover which insulates.) The combination of the two covers will be around R-3, so losses will be around 180,000 BTU/day.

Most contractors tell me that the dirt under the pool is a fine insulator, but I think they really don't know what they're talking about. Houses use under-slab insulation to insulate their 70 degree interiors from the 55 degree earth heat sink. The pool will be at 85 degrees, which is twice that temperature gradient, so I think insulation will matter even more for the pool. In particular, I'm most concerned about the water table contacting the bottom of the pool in the spring and sucking all the pool's heat into an underground plume of warm water headed towards the San Francisco Bay.

Let's suppose that concrete conducts 1.7 W/m-K. To convert that to more familiar units, 8 inches of concrete would be R-0.68 (which is terrible -- single-paned windows are better). I'll guess that the dirt, even when wet, insulates a bit as well, so that the bottom of the pool is about R-2. My pool will have an average depth of 7 feet (it has a 10.5 foot deep diving area), so it'll have an exposed area of about 1790 feet. If the pool temp is 85 degrees, and the ground temp is 60 degrees, that's 537,000 BTU/day, about three times my expected loss through the top in the spring. That's why I'm insulating the pool.

In particular, that blue stuff you see in the picture is 2 inch thick Styrofoam Highload 40, which has an R value of R-10. It is designed to deflect 5% at 40 psi, and is rated for continuous (dead) load of 13.3 psi. 10.5 feet of water plus 8 inches of concrete will be 5.25 psi, well within the dead load rating of the Styrofoam. The stuff should compress 0.33 mm when the pool is filled, which I don't think will cause cracking anywhere (thermal expansion is probably more than that).

The insulation changes the bottom of the pool from R-2 to R-12, so now I expect to lose 90,000 BTU/day, which is a savings of 447,000 BTU/day. To put that in perspective, on an average day my solar panels will deliver around 40,000 BTU each. I think I can squeeze 12 of them up onto the roof. The insulation is saving about as much heat flow as the panels put in!

To attach the insulation to bare dirt on the walls and shelves, I glued them on with Tap Plastics X-30 two-part expanding polyurethane foam, which I sprayed on with a pair of Wagner power sprayers. The trick here was to hold the panels firmly (with a few hundred pounds of force) against the dirt while the polyurethane expanded, which takes about 30 minutes. Once we did that the panels really stuck on well.

Note: I wore complete face covering, goggles, and breathed through an activated charcoal filter to take out the volatile organics. It was impossible to get the crew to wear the same protective gear. In the end, everything that was exposed got coated in a fine mist of polyurethane. The warning label says skin will develop an allergy to the stuff with repeated exposure. If you try this yourself, be careful, and be careful with your crew!

The soil at the bottom of the pool is firm clay, covered with filter fabric, covered with drain rock. Initially I tried gluing the insulation to the drain rock, but this doesn't work well. The insulation does not sit flat against the drain rock, and it rocks around a bit. Worse still, the polyurethane is quite springy, and was deflecting about a quarter inch under my body weight. This made me realize that the combinations of shelves, drain rock, and insulation is very bad, because the insulation on drain rock might settle, which would cause the pool to hang from the shelves, which would cause the gunite shell to crack. If I had it to do over again, I would eliminate the soil shelves, which are only there to reduce the cost of the gunite by $1500 or so.

Instead, I ripped up all the bottom insulation that the crews had installed and reinstalled it myself. I had already compacted the soil, first with the Bobcat, then with my feet (the crew were actually laughing at me), then with a heavy roller. Then I compacted the drain rock with the heavy roller. Then I cut the insulation into 15" x 24" squares and hand placed each one, tweaking the rock placement and vibrating the panel so that the rocks settled into a configuration which was flat for each panel. That took about four partial days, and only got finished because Martha got into the pit with me. I read later that a skilled laborer with one assistant is expected to place 100 square feet of under-slab insulation per hour, so I was about two times slower than that.

I'm still paranoid about settling, so I'm going to have the south and west walls of the pool done with #5 40 ksi vertical rebar on 6 inch centers. #5 is strong enough to actually support the entire pool weight (450,000 pounds filled) on the soil shelves, should the shelves not creep under that load. I also put a 1 foot chamfer on the edge of the shelf under the cover vault. The fillet of gunite that fills that chamfer, along with the rebar, will spread the torque from the pool wall hanging on that shelf.

[Update: I ended up with a mix of #3 40 ksi and #4 60 ksi rebar, with about half the strength necessary to hold up the whole pool. I figured I only had to hold up one end, and the rebar guy objected strongly to #5 -- he bent most of the rebar with his right knee!]

Another issue is the bond strength between the XPS insulation and the gunite. I've since built the pump vault, which is insulated as well, and the XPS/concrete bond there is perhaps only 1 to 3 pounds per square inch shear strength. If I assume 1 psi for the pool shell, then it will take about 140,000 pounds of shear, which is substantially less than the 450,000 pound filled weight of the pool. This shear strength is comparable to the shear strength of the polyurethane bond to the soil. This pool shell will be sitting on its bottom. The polyurethane is substantially more springy than the polystyrene, and I think it will deflect the 0.3mm in shear that will happen when we fill the pool.

I did not predict the cost well. I used 130 2 foot by 8 foot panels, with a small amount left over that I am using to insulate the pool piping. These cost $2800. I used 30 gallons of the X-30, which cost me about $1500. It took me and a crew of three guys four days to glue on the side panels, and I think that labor cost me $2500. The bottom I did myself, but the labor for that would probably have been another $1000 or so.

You can try to compare that cost to the cost of the panel array. The problem with the comparison is that the panels deliver the most heat when its warm, when you don't need it. The second problem is that the panel array is limited by the size of my roof, so I can't just spend an arbitrarily large sum on panels.

That said, standard FAFCO-type panels are something like $300 each, and produce 25,000 BTU/day. To generate the same amount of heat saved, you'd need 18 panels, which would cost $5400. However, the panels don't really work at all in November and April, when you need the heat most. The panels I'm using are SunEarth EP40s, which are glazed and insulated copper panels, and cost around $1100 each. These will deliver around 35,000 BTU/day, and will work in November and April. But I'd need 13 to match the insulation's savings. And that would cost $14,000! So I'm pretty confident the insulation will be a win.

I'm not quite done with the insulation. You can see a pile of pink insulation at the southeast corner of the pool. This is standard XPS, and it will be going around all the pool piping. I tried to find XPS pipe insulation, but the stuff is hideously expensive because it is all custom cut from large billets, usually for municipalities who are insulating their sewer pipes against frost. So instead I'm gluing together a little box of 2" XPS around all my pipe runs. Because the pool pump will be running 24 hours a day, the heat losses from the pipes can actually be comparable to the pool shell itself if not insulated. If you are building a pool, you might want to consider insulating your pipe runs even if you don't insulate the shell, because insulated pipe runs don't suffer any of the structural and installation issues that come with the shell.

Side note: I had a hell of a time finding a Highload 40 distributor. I ended up calling Dow directly, who referred me to White Cap Insulation in San Francisco, who sold me the stuff for $21.58 per 2" x 2' x 8' sheet. Note that standard 20 psi extruded polystyrene has a dead load rating of over 6 psi, so it would have been technically okay for my 5.25 psi of dead load. If I wanted to save around $600, I would probably have gone for the thinner stuff. It would also be easier to buy. I'm hoping that the extra-sturdy foam is buying me a little margin, which is nice to have because I don't have examples of other pools that have been built this way. [Update: somehow I miscalculated the amount of gunite in the pool, and it's a bit larger than my estimate here. So, I'm glad I have lots of extra margin on the load carrying capacity of the insulation.]

Side note two: the space down at the bottom of the deep end experiences really wild temperature swings right now. Because it is down low, it is radiatively coupled to the sky and not much else. When the sun is shining down there, it can get well over 100 degrees. As soon as the sun goes down, the temperature plummets, and because the pool is a depression, chilled air tends to stay down there.

Side note three: If you read this post and insulate your pool, or know of a pool that's been insulated, you might leave a comment so that there is some repository of success stories on the internet for this idea. And please please post if there has been a problem with an insulated pool.

The World's Underwriter

2008-12-14T23:22:00.001-08:00

This graph, from the New York Times, shows the extent of U.S. financial commitments made over the last year to deal with the credit crisis.

From December 2007 through September 2008, we committed $537 billion. That is not money spent, but it is money put at risk by guaranteeing various financial instruments, and by loaning to banks that could not otherwise get loans.

But in September 2008 the Fed went nuts, nearly doubling the commitment to $1097 billion, or around $5500 per taxpayer. (There are around 200M taxpayers, right?)

And then in October, the FDIC joined the Fed, and, according to the NYT, together they upped the commitment to $5069 billion. I am not following the NYT very well here, however, since it appears that $1600 billion of this refers to the size of the commercial paper pool, and not the size of the projected government purchases within that pool. So it's not like the government is actually selling $5 trillion of T bills.

It appears the Fed has become the world's underwriter. The commercial paper thing appears pretty transparent, for instance. The Fed sells T bills at 1% interest, and buys commercial paper at 5 to 10% interest. So long as the default rate is lower than the spread, the Fed makes money. Given the size of the money flow here, it is possible that the Fed could either make or lose amounts similar to the size of the national debt over the next couple of years.

Of course the problem is that someone at the Fed has to decide what rate they want for paper from which companies. Since the decisions required are vast -- they have to price the entire commercial paper market -- one presumes the same people are doing this that just presided over the credit default swap implosion. So, it seems like we might be more likely to headed for the "likely to double the national debt" outcome and less likely to end up at the "paid back the national debt" outcome.

This is Macroeconomics, for real. Wow. It really makes you wish there were a way to get off this train.

Prediction

2008-12-12T23:14:00.000-08:00

That white paper got me thinking: what if the government made a bunch of other sensible decisions?

They might shut down Yucca Mountain, and require that all nuclear waste be stored on the site of the reactor for 300 years. Nah, won't happen. [Update: They did it!]
They might just have NASA cancel Ares-I and Ares-V, and leave it to SpaceX to provide a launcher. This might actually happen. All those folks in Florida and Utah that used to work for NASA contractors? Learn to build windmills. Some of you can learn to build Dragons and Falcons. [Update: Holy crap! They did it!]
They might require all air conditioners and heat pumps to have short-term demand management controls. As the newer air conditioners got deployed, we'd have a lot less need for online throttled-down combustion gas turbines to back up all these new wind farms. I've not seen any rumblings of this yet.
They might even standardize form factors for rechargable batteries... [Update: Um, they sort of did it! (Europe hsa standardized cellphone recharging plugs)]

Going Nuclear

2008-12-12T23:05:00.000-08:00

Stephen Chu, the current director of the Lawrence Berkeley National Lab, and the guy that Obama just fingered to be the new Secretary of Energy, signed this paper in August of this year. The paper is a short, very high level, but clear and broad statement of why and how we should invest heavily in nuclear power. Usually, statements like this come from people with no clout.

Holy crap. This Barack Obama guy seems to be making at least some decisions I agree with. I'm confused and unused to this feeling, but I think I like it.

-Iain

Spend, spend, spending our way out of recession

2008-12-01T19:01:00.000-08:00

We have a consensus among politicians in this country that we must spend our way out of this recession. Of course, there are many things to spend money on:

For the last six years, the neocons within the Bush Administration have spent around 700 billion dollars of our money on wars, and committed another trillion or so to the aftermath of those wars (caring for the permanently maimed American soldiers).
This March, the idea that everyone jumped at was spending money on consumer goods, so every American got a check for $400 from the government, and was exhorted to spend it on consumables. Pfft! Just like that, $80 billion gone.
In just the last month, the Federal Reserve has spent hundreds of billions by buying stock in badly run banks whose value is justly plummeting as people realize how stupid their management was.

All of these have been colossal failures from an economic point of view. And I do mean colossal. The U.S. economy is about $13 trillion a year, and has a historic growth rate of about 3% per year. It is the most awesome generator of wealth ever. The economy usually generates about $400 billion a year in growth. And our government is now throwing away money at a rate which entirely negates the economy's ability to grow at all. The current trends guarantee that our children will be worse off than we are. We are within a single order of magnitude of blowing away the entire output of the U.S. economy, which would reduce us to hunter-gatherers amid fancy energy-starved infrastructure within a year or two. Lest you think that an order of magnitude increase in government spending is preposterous, consider that one department, the Fed, is now spending more than 1% of the U.S. GDP per month propping up just one industry. The auto industry is lining up at the trough, and others aren't far behind.

Although the things the government spends money on now are crippling the economy, this is actually a good time for government spending to grow, so long as we spend money on the right things. Private sector returns on investment are low, so the cost of borrowing has dropped, which means investments have longer to make a return. This is a great time for the government to spend money on things that will cause the economy to grow in the long term:

Domestic power infrastructure, like wind farms and nuclear powerplants. These will make the cost of future energy more predictable. Predictability means less risk, so that the cost of capital for energy-intensive manufacturing, like fertilizers and aluminum and steel and plastic, will be lower in the U.S. than in other countries without the same infrastructure. That will give our descendants decades of competitive advantage, which is enough time for not just businesses but industries to grow.
Health care efficiency. I'm not suggesting we spend more on health care itself -- we're spending too much on health care. I suspect that a huge amount of operational expense can be slashed from health care through radical restructuring without large amounts of investment. The restructuring will be radical though. Imagine the number of people put out of work if drug advertising stopped.
Electrified transportation. Hydrocarbon-based transport will always rely on imported fuels subject to ever-more volatile price swings. The value of real estate depends in part on the cost of transportation (if you drive 40 miles to work at 20 mpg and $4/gallon and 3% discount, that's $100k present value), and so volatility in energy prices causes volatility in housing prices which caps the house value that people can afford. Worse still, we get situations like the current housing bubble, caused by just 2 million people simulaneously finding out they bought way too much house. (That's just 1.7% of the 116 million homes in the U.S.!)

At least the president-elect seems to have the right idea. I heard him refer to investment spending as a "two-fer". I was disappointed at his notion that half the good idea of a "two-fer" is just spending the money at all. But at least he's looking for the right kind of thing to spend on.

Save GM's workers, but not GM

2008-10-31T11:22:00.000-07:00

I've just listened to a discussion on KQED about whether the US government should bail out the auto industry. The reason the solution here is not obvious is that everybody assumes that to save the job of someone who works for GM, you have to save GM. I suspect that's not true.

Toyota makes lots of cars in the United States. I suspect the majority of Toyota's domestic sales are domestically built. It saves them shipping, and avoids exposure to foreign exchange risk. The overall point is that there is no problem with American workers making cars that sell. The problem is that some American workers are making the wrong cars, and that is the fault of their engineering and management.

The usual way for these things to work out is that GM would go bankrupt and it's assets would be sold. Toyota would hire some of those workers, and buy some of those assets on the cheap, because they'd know that with GM gone there would be a reduction in the supply of cars and so they could make more money by increasing their own production.

Crucially, the assets (e.g. assembly plants) would be sold for a fraction of their original cost because Toyota would have to adapt them to Toyota's production style. This is very important -- GM's production style isn't profitable, so those assets have to be changed to become profitable.

Also, crucially, the former GM workers hired by Toyota would have to be retrained. This takes a lot of time for Toyota. The rehiring process also tends to weed out at least some of the poorly producing workers.

All this adaptation of physical capital and retraining of workers is all good stuff. So what's so bad about bankrupcy?

GM's shareholders lose a lot of money. Actually, GM's shareholders lost a lot of money a long time ago. GM's total market cap isn't very large, and hasn't been for a long time, because GM has had bad management for a long time. I claim that this problem is not terrible and does not warrant intervention from the government.

GM's workers and suppliers have no business for a long time. This is the real problem, and this is something that the government can help with.

So, here is what I suggest. I suggest that because GM, Ford, and Chrysler are "too big to fail", the government should intervene before they shut their doors, and negotiate an orderly transfer of their assets to companies that can make those assets perform. I suggest that Toyota and Honda and Mercedes and so forth would be willing to purchase much of the assets of the big three for a fraction of their orginal price, and would be willing to take government inducements to keep the factories open and the workers employed while they are restructured and retrained.

The result will be that some assembly people will be put out of work, because not all the Big Three's plants will be purchased. The corporate management of the big three will go unemployed, which is fine, as they are responsible for the current distress in those companies. There will be differences between the financial commitments that GM has made to its workers, and those that Toyota makes its own, and the differences between those commitments will have to be worked into the sale price from GM to Toyota.

We need to clarify the idea of "too big to fail". Our commitment is to our people, not to our companies.

The Biggest Haul Ever

2008-10-29T00:09:00.000-07:00

The $700 billion bailout is about the same size as the dollar cash money supply in North America (that is, excluding dollars held as reserve currency in foreign sovereign banks).

The robbers in the Securitas Depot Robbery of 2006 made off with $92 million. This is the largest robbery in the western world, surpassed only but hugely by the $1 billion heist of cash from the Central Bank of Iraq in 2003, which was curiously similar to current events in that it appears to have been made possible by the actions of the Republicans in the U.S. government. In that case, it was the initiation of bombing of Bagdad. The current mess traces back to the Gramm-Leach act of 1999 which repealed the Glass-Steagall Act of 1933, which was intended to prevent banks from engaging in risky investment practices such as those that had caused the banking collapse in early 1933.

But neither of those robberies is anything like the size of the bailout. Imagine that some group managed to knock over every single bank, not just in one city, but in all of them. Not just the banks, but the convenience stores, groceries, businesses. Not just those but swiped the cash from every house and every wallet of every person in the United States. What a haul! It's positively Grinchian in scope.

Now imagine that those responsible are being paid a salary by the federal government. And that the folks they are turning the money over to are being paid extra to figure out what to do with it!

I've been mugged!

Bail out Main Street, not Wall Street

2008-10-01T03:15:00.000-07:00

The $700 billion Paulson plan is too expensive and fixes the wrong end of the problem. A better solution is obvious: bail out the mortgages that are going into default, rather than bailing out the banks that are capitalized by derivatives of those mortgages.

Bailing out the mortgages themselves is much cheaper (around $200 billion), directly eases the problems of millions of homeowners, and should fix the bank's capitalization problems.

Now, if it doesn't fix the capitalization problems, that means there is a lot more bad debt floating around than just these subprime mortgages. And if this other debt is the problem, let's get that problem front and center so we can deal with it.

Some background: The subprime crisis is essentially this:

Millions of people in the U.S. bought houses more expensive than they could afford, on the assumption that the rise in the price of the house would help them pay for the house.
Those people accepted mortgages with initally low rates, that then increase after a period of time. They figured that before the rates increased, they would either get a job that paid better, or refinance the house based on a higher assessed value which would give them a larger equity stake and therefore make it possible to get a loan with a lower interest rate.
Housing prices are not rising, and those people are unable to refinance and don't have a better job. When the interest rate rises, they can't pay the increased bill and fall behind on their mortgage payments.

After 10 years of excessive spending on houses, and excessive building of expensive houses, the US has too many expensive houses. The house price collapse will not be resolved until the US economy has grown enough folks with enough income to afford those houses. My guess is this will take about a decade.

In the interim, we cannot allow those extra expensive houses to go unoccupied. Unoccupied houses fall apart, and so they lose value quickly. This loss will be borne by the large institutions in our economy and will be a net drag on our net asset growth. Under the Paulson plan, the government will buy derivatives of these mortgages and these losses will pass to the taxpayer.

So, the houses must remain occupied, and we do not have enough people who can afford them to occupy them. Until we grow those folks, the best people to occupy those houses is the people who are living in them now. I have a plan to keep them there, detailed below.

The financial crisis is an extension of the subprime crisis:

Banks have been converting bundles of mortgages into mortgage-backed equities, and selling those. Many institutions now own these assets.
The value of those equities depends on the number of mortgages within them that default.
The value was initially determined by making assumptions about the usual number of mortgage defaults. Side note: some mortgage-backed equities are guaranteed, so that the risk of many defaults is seperated out into another security. That does not change the problem, only who owns it.
Because the subprime crisis is surprising, nobody is comfortable estimating the number of mortgage defaults any more, and so the value of these equities is not well known. Their value is plummeting for two reasons:

More risk means less value.
Banks are trying to sell these MBEs, but nobody is buying.

Banks are required to have a dollar of capital for every 12 dollars they loan out. When the value of their assets drops, they have to sell some of their loans (packaged as mortgage-backed equities) to generate more capital.
So, selling MBEs causes the value of the MBEs still held to drop, which forces the bank to sell more MBEs. The feedback loop is driving the capitalization of the banks below the legal requirements, which causes the banks to fail.

Paulson's plan is to have a U.S. government agency buy $700 billion of mortgage backed assets at some "fair" price. This price will set a floor on the valuations of the assets owned by banks, so that they don't have to sell so many MBEs, and it will give them the cash they need to improve their asset positions to the point where they can loan money again.

The Paulson plan will fix the Wall Street problem, but it does not address the Main Street problem, that is, the mortgage defaults, except that in avoiding a recession it will reduce the number of mortgage defaults from people losing their jobs.

The alternative is to fix the Main Street problem directly. If the government guarantees that only the expected number of mortgage defaults happen, then the MBE will have known values, which should also put a floor on the valuation of the bank's held assets and similarly ward off the credit crunch.

Here is how the government makes that guarantee. Let's say that Harry has an adjustable-rate mortgage which just increased its rate, and he can't afford it. His original 10% equity in the house is down to 5%. Ordinarily he would go into default, and at some point the bank would reposess the house and evict him, and then sell the house. We don't want that to happen because either the house will go vacant for a long period of time, during which it will deteriorate and lose value, or the bank will sell it for a song and lose a great deal of money, causing the bank to go bankrupt.

Instead, the government steps in and offers Harry the following deal:

The government buys 25% of the house from Harry.
Harry now refinances his 75% of the house.

He now has 6.66% equity in his smaller share of the house.
His loan amount is 74% of what it was, so his payments are proportionally smaller.

At some point in the next 10 years, presumably after the housing market has worked through its excess inventory, Harry gets a one-year notice from the government that he needs to either buy back the government's 25% or sell the house. He can sell at any earlier time if he likes.

So, how much cash would the government have to invest with this plan? Suppose the number of subprime mortgages is 9 million, and 25% of those are in serious delinquincy. Suppose the average value of those houses was $320,000. For the government to purchase a 25% stake in all of those would cost $180 billion. And note that this is an investment. After ten years or so, we should expect to see most of that money back, perhaps with some gain.

Why is my plan cheaper than Paulson's plan? The primary difference is that my plan keeps people in their houses by purchasing a portion of the house's value. Paulson's plan requires the government to buy the full value of the mortgage. What Paulson's plan does not detail out is that the government will be stuck with the loss when the owners default on the mortgage and then the house is repossessed and sold for a loss.

Deer (plural) in the headlights

2008-09-27T06:34:00.001-07:00

I watched the first presidential debate last night, as I expect many of you did.

My basic takeaways:

I was surprised to find myself liking Obama's foreign policy points more than McCain's.
McCain seems really worried about the effect of a defeat in Iraq on the U.S. military.
Neither candidate has a clue about the financial meltdown, either what to do about it or how it would affect his administration.

The conventional wisdom was that McCain understands foreign policy better than Obama.

Certainly he's travelled to hot spots far more than Obama has. This is partially a function of the amount of time that McCain has been in the Senate. But McCain has also been more interested in going places than Obama, and I'm disappointed that Obama hasn't taken better advantage of his ability, as a Senator, to go places and see first-hand the situation on the ground. As a leader I think you always have to spot check the information you are getting, otherwise you end up with travesties like Colin Powell presenting bad evidence to the U.N.

But I like Obama's take on South Ossetia better than McCain's. McCain espouses a simple response: The Russians went in, we want them out. He made the more interesting point that six months ago he had called for replacing the Russian "peacekeepers" in South Ossetia with troops from other areas, since the Russians were hardly neutral. Obama called for both sides to cool down, which is significant because he's acknowledging that Georgia's president was being provocative. He didn't mention any details during the debate, but I think his position may be more realistic here.

Obama tiresomely pointed out that going into Iraq was a bad idea in the first place, which I agree with, but as McCain points out, the next president decides when and how we get out, not whether we go in. But McCain seems to think that withdrawal is driven by avoiding the stigma of defeat, both for its effect on our military and on also for the effect on our adversaries. I thought it would have been useful for McCain to point out that there is a real link between our defeat in Somalia and the 9/11 attacks: bin Laden took specific inspiration from our debacle in Mogadishu, as reported by one of his lieutenants in the 9/11 commission report.

Obama is right when he points out that the current administration has been completely occupied by Iraq. As he says, we took our eyes off the ball, which was nailing bin Laden and al Queda. I think there is real value in killing this man and his organization, because it sends the right message to other asymmetrical adversaries: any single person will become exhausted before the U.S. military does. I think the rest of the world expects us to tear up a lot of ground while uprooting al Queda, and we should.

McCain made a good point that Obama has made tactical mistakes: Obama should never have explicitly said that we would attack from Afghanistan into Pakistan, and he should have been more careful about suggesting that he himself, as President, would meet with and thus legitimize Ahmadinejad. These are screwups, I think reflective of Obama's inexperience, but I think we can live with these kinds of screwups.

What I am impressed by is Obama's view that our Iraq engagement has prevented us from using our military power elsewhere to apply pressure to al Queda. To some extent we've managed to attract foreign adversaries to a field where we are clear to fire, but I think the larger effect has been to grow new adversaries. Although there is an aspect of bean-counting to it, I think Obama has the more useful perspective of Iraq in the context of the world. I would like to see him frame our withdrawal as a balance between the risk of emboldening adversaries, as in Mogadishu in 1993, and allowing adversaries to flourish unopposed, as in Afghanistan during the rise of the Taliban.

Obama mentioned taking four divisions out of Iraq and putting two into Afghanistan. I wish people would use numbers of troops instead of words like "division", because folks like me don't know how many people are in a division.

Given significant prompting, neither candidate offered a clue about how to react to the financial meltdown, nor how the meltdown might affect their administration. They were like deer in the headlights of an oncoming car. Obama made the distinction of "Main Street" vs "Wall Street", but that's just a sound bite. I think the more interesting distinction is whether the government should buy partial interest in houses whose present owners face foreclosure, or if the government should buy credit default swaps whose values are unknown because of the prospect of widespread foreclosures. More disappointingly, neither candidate had any suggestions for how we might stick the bill to the people who profited so hugely from this debacle ($62 billion in bonuses in 2006!).

Both candidates came out in favor of nuclear power, and the distinction was over their approach to waste storage and reprocessing. Fabulous! Their differences are over waste: Obama wants to see a better solution, which has been used in the past as a passive aggressive stall tactic on nuclear. McCain seems convinced that there is some solution to the waste problem, although I suspect he thinks Yucca Mountain is it. McCain twice pointed out that Obama's position is passively antinuclear, as you can't have powerplants unless you store the waste.

On the whole, I was impressed with the dignity of the debate. Last year some friends predicted a McCain-Obama contest, and I said then that I'd be happy with either result. I still think that's true.

Dichroics 101

2008-08-28T22:40:00.000-07:00

A friend asked for a rundown on dichroics, which are the coatings we put on optical glass (and sunglasses) to optimize the transmission properties of our lenses. So, here is Dichroics 101. You could also check out Wikipedia.

Visible light is made of photons. Each one has a wavelength. Your eyes are receiving a bazillion photons every second in the daytime. At night, your dark-adapted eyes are capable of noticing the flicker of individual photons, but only sometimes. Visible light varies from 420 nm (blue) to 700 nm (red). A nm is a nanometer. 1000 nm is a micron (micrometer, but nobody but Europeans says that), 1000 microns is a mm (millimeter), 1000 mm is a meter.

So, a 420 nm photon is really small. However, atoms are 0.1 to 10 nm across, and we can lay down layers just a few dozen atoms thick, so we can actually build things that are smaller than the wavelength of light. Get back to that in a sec...

Any given transparent material has an index of refraction, which tells you (among other things) the speed of light in the stuff. Air has an index of refraction of about 1, so that the speed of light in air is the same as it is in a vacuum: 186,000 miles per second. Glass has an index of refraction of 1.5 to 1.8 (depending on which kind of glass). Plastics (like polycarbonate, what is most likely used in sunglasses) have an index of refraction around 1.5. So, in plastic, the speed of light is 186,000 miles/second / 1.5 = 124,000 miles/second.

Whenever photons go through a surface, like changing from air to glass or back, some will reflect. The number of photons reflected has to do with the change in index of refraction. The equation is: reflected fraction = (Na - Nb)^2 / (Na + Nb)^2, where Na and Nb are the indices of refraction for the two materials. For example, from air (Na = 1.0) to plastic (Nb = 1.5), the fraction is 0.04, or 4%. When you see yourself in a window (or in someone else's sunglasses), this is what you are looking at. Actually, you see two of these, one off the front surface, and one off the back surface of glass.

Suppose we put a 100 nm thick coating of Magnesium Fluoride (a.k.a. MgF2, index of refraction is 1.38) on a piece of glass (index of refraction 1.5). There will be two reflections: one from the air/MgF2 surface (2.5%), and one from the MgF2/glass surface (1.7%). Because there is a smaller change of index of refraction across each surface, each surface reflects less. If the index of refraction of MgF2 was closer to 1.25, halfway between air and glass, then we'd find that the power of the two reflections, when added, would be less than the power of a single reflection of an air/glass surface. But MgF2 doesn't have that nice property, so why do we bother?

Those photons act like waves: they have peaks and troughs. That 100 nm thickness wasn't just any old number, it is 1/4 of the wavelength of green light in MgF2. Green is ordinarily 550 nm, but going through MgF2 it's about 550/1.38=398.5 nm. The light reflected from the MgF2/glass surface will have travelled two times 100 nm more than the light reflected from the air/MgF2 surface, or one-half a wavelength more. So, the crests of the wave off the MgF2/glass surface will line up with the troughs of the wave off the air/MgF2 surface. When you add those two together, you get... cancellation.

Or... nearly cancellation. The air/MgF2 reflection is a little stronger than the MgF2/glass reflection, so there will be a little wave left over. A 550 nm photon will reflect (2.5-1.7=0.8%). There you have it, the first antireflection coating, as developed for German submarine periscopes in World War II.

Now notice that 420 nm (blue) light will not cancel as well, because the two reflections are 65% of a wavelength offset from one another. The peaks and troughs don't quite line up, so it doesn't cancel as well. The same is true of 650 nm (red) light. So, the reflected light will be purplish: it will have some blue and red, but not so much green.

This is the basis of dichroic filters. You can put several layers of stuff onto a glass or plastic surface, and each additional surface will have a reflection. At each wavelength, you can add up those reflections with their wave offsets to get an overall reflectivity. You end up with a graph which shows how much the thing reflects at each wavelength. By varying the materials deposited and the thicknesses, you can get something which has interesting and useful properties, such as reflecting all the IR (> 670 nm) and UV (< 390 nm).

You can buy such a thing at a good camera store. It's called a B+W 486 filter.

Grove's plan

2008-08-19T00:31:00.000-07:00

Now I've read Andy Grove's plan (at The American, or via Wired) to fix our energy dependence national security mess. Mr. Grove thinks, as I do, that national security is the most immediate problem we face.

There are flaws in both Grove's and Pickens' plans, but we can take good ideas from both and act on them immediately.

There are two steps to either plan:

Switch our vehicles to a non-petroleum energy form
Make that energy domestically

With Pickens' plan, we switch to natural gas to power cars (step 1), and simultaneously free up domestic methane production by building wind turbines (step 2). If we do step 1 without step 2, we end up switching from imported petroleum to imported natural gas, which suits Pickens quite well because he has lots of gas to sell us.

With Grove's plan, if we do step 1 without step 2, we've got a bunch of electric cars which will plug in at night. The extra demand at night will drive utilities to produce more baseload power -- coal, wind, or nuclear, in that order, all of which is domestic. The advantage of Grove's plan is that step 2 is handled by the market.

The problem with Grove's plan is that converting cars and trucks to electricity instead of natural gas is more costly. The added cost will cripple the plan in two ways:

It is so much more costly that the conversion will happen more slowly. Per year, less petroleum imports will be displaced.
Fewer vehicles, in the end, will be converted.

I think there are good ideas in both these plans that we should isolate and exploit immediately.

There are no forseeable battery technologies that will work on long distance trucks. The obvious substitution here is to move long distance freight by electrified train. We already have most of the rail infrastructure (rights of way are the big issue here), and the nation is already switching some cargoes back to rail. But railroads have been sick for a long time, and we have to fix them before they can help America.

Rail's crushing disadvantage compared to trucking is it's capital structure -- the fact that the same companies own the road and the trucks. Long distance trucking works because multiple companies run trucks over the same routes, which are owned and paid for by the U.S. government via tolls on the trucks and taxes on the diesel they burn. We should change rail to use this structure. The rail infrastructure should be electrified in the process, so that the independent trains can choose to run on cheaper domestically produced electricity where it is available. All the technology necessary is already developed and in production.

The good idea in Pickens' plan is to build lots (many tens of thousands) of wind turbines. Wind turbines displace imported natural gas with domestic labor, and that is the most useful part of his plan. If you then convert cars to run on natural gas rather than petroleum, you in turn displace some imported petroleum with some imported natural gas. This second step is a fine thing too, as petroleum costs more than natural gas per unit energy, but the first step is what is most important.

The United States made a terrible mistake during the 1990s by building nearly a terawatt of natural gas-fired turbines. The choice was driven by utilities who know that fuel costs can always be passed to the consumer, so that cheap gas turbines minimized investment and so maximized return on investment. The problem here is that utilities were allowed to make investments with large externalized costs. Market forces do not work to the advantage of most citizens unless the market is set up to internalize the costs that matter to the citizens. Because utilities have no sons and daughters to send to war, they cannot be allowed to make investment decisions that force us to send our sons and daughters to war.

Electric freight trains and wind turbines will not fix America's imported energy problem. Both, however, can be pursued immediately, are solid steps in the right direction that will not have to be reversed, and will make market-affecting changes in our consumption of imported energy. Both options will buy us some time during which we must develop better options.

In the medium term, we can build more nuclear power plants. These take longer than wind turbines to come on line, but the eventual impact can be much larger. The public discussion of our nuclear options is becoming more sensible, and I am beginning to hope that we may be able to begin building this infrastructure again after a two decade hiatus that has cost us terribly.

Nuclear power generation, if pursued in a sensible way, can drive the cost of electricity in the U.S. down below the cost of coal power in China, in a predictable, long-term way, which I think should be an explicit goal of our national energy policy. This will have the effect of "onshoring" basic industries that we have been moving overseas for decades. The onshoring effect is actually more powerful than displacing imported petroleum, because the imports that are replaced for a given amount of investment have higher added value.

Unreliable Wind Power

2008-08-18T08:12:00.000-07:00

The electricity that arrives at your home or business is extremely reliable (if you live in the U.S.). The electricity that comes from a windmill is unreliable -- it only comes 1/3 of the time, and you never know exactly when it's going to come or how much you are going to get. If you want to sell wind energy, you have to convert unreliable wind energy into reliable power. How is it done?

This paper explains how, but it's a tough slog. What follows is my summary.

The utility companies already solve a similar problem. Electricity is not easily stored, and in modern grids it is generally not stored at all. So, when you flick on a light switch, the immediate effect is that the power dissipated by all the lights in your neighborhood drops a little to compensate. Within seconds, some power turbine perhaps hundreds of miles away must twist a little harder on its generator shaft to get everyone's line voltage back up, and the extra thermal or hydroelectric power fed into the turbine to get this extra twist will be just about what your light bulb burns, plus the inefficiencies of getting the power from the turbine input to your bulb.

Turbines can only throttle up to 100% of their rated capacity, and they get inefficient when they throttle down too far, so utilities will shut down or spin up units to make larger changes. Changes like these take a long time, so utilities predict what the expected load at any given time will be, hours or days in advance, and schedule units to be on or off line to match the predicted load. Utilities keep some fraction of their turbines at partial output so that they can immediately crank up to match unexpected increases in the load.

The biggest increase in the load that they plan for is usually an unexpected dropout of one of the generators. If a 1 gigawatt generator suddenly goes off line, the grid controllers might respond by taking four other generators from 700 to 950 MW output. It would be impossible for this to happen instantly, but luckily, when most generators go offline, they do so gradually, and if they coast down over the course of seconds, other generators can crank up to match. If a circuit breaker pops or a line parts, or something else happens very quickly, then there is usually a temporary brownout as the line voltage drops down to the point where the loads match the generation. The backup generators usually ramp up within seconds, and many devices (like your computer or TV) can ride through a partial loss of power for a second or so.

So, the bottom line is that utilities predict the change in demand on their generators, and there is some variation from their prediction, and being ready for this variation costs money because some turbines (the spinning reserve) must be run at partial throttle which is less efficient than flat-out.

Just as an aside: consider how valuable it would be for the utility company to be able to instantly shut down your air conditioner for just a few minutes. This ability would act as part of their spinning reserve. During the summer, air conditioners are a substantial fraction of the total power burned. I'm pretty sure that for most of the U.S., the ability to shut down even a fraction of the air conditioners for 10 minutes would cover the entire spinning reserve requirement. That could save a lot of money, and PG&E (my local utility in California) is experimenting with just that through their Underfrequency Relay Option on the Base Interruptible Program. Anyway, back to the summary.

Wind farms produce electricity whenever the wind blows. Wind speeds can be predicted, and there is always variation from the prediction. When a wind farm is connected to the grid, the total variation in load on the load-following turbines is larger than without the wind farm, and so more turbines must be run in load-following mode, and these incur a cost associated with wind power that is real but not easy to predict before the wind farm is built.

For instance, part of Denmark's grid is connected to Norway's grid. Norway gets most of its power from hydroelectric plants. Hydroelectric plants are very good at load following and so they are usually the first choice of plant to handle variation from plan. Because Norway has lots of hydroelectric plants, and because it has high-throughput connections to Denmark, Denmark can hook up fairly high powered wind farms to its grid and incur relatively low costs for standby power.

Now that utilities are connecting large amounts of wind power to their grids, they are getting more precise numbers on the costs of doing so.

Wind works well where you have year-round high winds near hydroelectric dams.
The short-term variation from wind farms is usually quite small, since turbines are small (a few megawatts) and don't all shut off at the same time.
Big storms give the worst case variation, since when a wind turbine goes too fast it feathers its blades and shuts down, going from full output to nothing, often in synchrony with other wind turbines around it.
Wind farms spread over large geographic areas have less total variation (the wind doesn't die everywhere at the same time). Ideally the spinning reserve would thus scale up slower than the total windpower connected, making marginal wind power less expensive. Unfortunately Denmark is too small to see this effect, and it would require very high throughput long distance power distribution.

Wind turbine manufacturers are working on making their turbines play better with the grid. Variable-frequency turbines go offline more slowly by generating power from their blades as they spin down after losing wind. Many manufacturers are shipping wind turbines with extra-large blades, so that the turbine produces a larger fraction of its output more of the time. This reduces the cost of variability in exchange for an increase in the capital cost of the turbine, which is a tradeoff made possible by an understanding of the cost of that variability.

Wind turbines appear to work economically (when the utilities are prodded by a production tax credit, which I support). As more turbines are installed, the best windy areas are used up and the least expensive spinning reserve is committed. On the other hand, wind turbine costs might be coming down some day (maybe -- materials costs are going up), and the need for spinning reserve is decreasing. It's a fairly tense balance.

Personally, I'm happy to see more wind turbines getting installed, since it's domestically produced, mostly-carbon-free, low marginal cost power, and let's have more of that. There is going to be a limit to how much wind power can be installed, but we're nowhere near that limit yet.

At the same time, it's sobering to consider that the United States once built almost 100 nuclear plants in about two decades, bringing new power online at the average rate of 5 gigawatts a year, at a time when our economy was one-third to one-half the size it is now, in real terms. At it's peak, we were building much faster than that. This economic explosion was driven by the business fundamentals as much as it was by overexcited businessmen jumping on the latest bandwagon. And the fundamentals were and are that if we decide on a reactor design (like Palo Verde), we can build and operate them cheaper than coal plants.

To match this performance, and get to 20% of the U.S. grid in 20 years, the wind industry would need to install about 300 gigawatts of nameplate capacity. That would require getting to a peak of 30 gigawatts a year, up from 4 gigawatts in 2007, which is 11 years of sustained 20% growth. The fundamentals for wind are not as good as they were for nuclear in the 1960s. It won't happen without a major breakthrough.

SpaceX launch 3 failure

2008-08-04T13:54:00.000-07:00

I watched the YouTube video, which shows launch through 6:16 indicated (T+2:11). Two comments:

Can we please get a heater on the on-rocket camera lens cover? It's hard to see much through the condensation.
It looks like the rocket has a 5 second roll oscillation that starts as soon as they go supersonic. I don't know if this is fuel slosh, like on the second stage of the last launch, but it doesn't look like other rocket launches to me. Any kind of wobble before seperation could cause the first stage to ding the second stage, as happened on the last launch.

I really hope their next attempt goes better. This launch wasn't obviously progress.

Constraints to wind power

2008-08-04T08:50:00.000-07:00

Jesse Ausubel has a pretty good essay which describes what he thinks the future of power production will look like. It's a somewhat rosy picture, and although I'm also optimistic (but not for the next few years), I disagree on a couple of points.

He, like I, thinks that we've got to get away from coal. I don't follow his reasoning for why he thinks we have to get away from coal. It seems he has identified a long term trend towards fuels with less carbon and more hydrogen, and he thinks we should make choices to perpetuate that trend. As near as I can tell, he's skipped the part about why the trend is a good thing. Perhaps he thinks consumers like lower carbon fuels because they tend to burn with fewer combustion byproducts, but he doesn't back this claim up with any market analysis.

I think we as a country need to stop burning coal because

we import a lot of oil to burn coal (we spend almost as much on oil to move the coal as on the coal itself), so that the price of coal-fired power is quite sensitive to the cost of oil,
it is politically possible to install lots more windpower, but coal is seeing opposition, and it is vital to our economic health to get a lot more electric supply,
wind power is inelastic supply, whereas coal power is elastic. That is, a coal plant will shut down if the price of electricity falls below it's operating costs, but a wind turbine costs almost nothing to run and will keep generating through a larger swing in electricity prices, which will make our electricity supply more predictable,
and finally and perhaps most importantly, because climate change matters.

My biggest point of disagreement is with Jesse's assertion that windpower is impractical due to land use constraints. Other, perhaps clearer-thinking people have made this same point. Jesse makes a very sobering calculation: he figures a wind farm produces 1.2 watts per square meter, average. To produce all of the U.S. grid's 450 gigawatts (average), you'd need a lot of land. Jesse calculates 780,000 square kilometers. The area of the U.S., for reference, is 9.16 million square kilometers, with 1.75 million square kilometers of cultivated cropland. I don't get quite as large a number as Jesse, but we'll take his 780k km^2 for now.

He figures that's just too much land. But this argument is trite. I'll skip over the point that farmland with wind turbines is still farmed land, and instead focus on a more basic question: How much is too much? I think too much is when the next wind turbine to be installed is projected to make no money. That could be all the farmland plus a lot of offshore turbines, or it could be just a few places in North Dakota. It won't be decided by people getting scared of erecting some more infrastructure on 44% of our existing cropland. Farms in the Netherlands in the 1800s were dotted with windmills, because that's what drove the pumps to keep the water out. Farms in the U.S. in the late 1800s were dotted with windmills, with parts shipped at enormous expense across the continent, because that's what pumped the irrigation water wells. Modern farms aren't currently dotted with wind turbines because they've been using oil instead.

Jesse's argument is also trite because it ignores the huge variation in windiness around the U.S. In North Dakota, the entire state is class 4 or above. That means the power available at 50 meters above the ground is 400-500 watts/meter^2. Even during the summer doldrums, the average power available is 300-400 watts/meter^2.

Jesse's 1.2 watts/meter^2 number comes from a wind farm in Lamar, Colorado. That wind farm has 108 1.5 MW turbines spread over a 11840 acre area. Multiply by a 30% capacity factor, and you get 1.01 watts/meter^2. (I'm not sure how he got the extra 20%.) Why is this number so low?

It's economics. The company that owns the wind turbines pays the company that owns the land on which the turbine is sited approximately $3000 to $6000 per year per turbine. The net present value of that payment stream is $60,000 to $120,000. The turbine costs $1,500,000, which is a lot more. Spacing the turbines farther apart slightly increases the power from each turbine, at small increases in royalty payments and road and cable construction costs. If land scarcity ever becomes an issue for wind farmers, I would expect $ per watt and watts per km^2 to go up. Note that $/watt may go up slightly, while watts per km^2 may go up a lot.

Consider that the first big wind farm, on the Altamont Pass, has a power density of 0.86 watts/m^2, which is lower than Lamar's density. If you follow that link, you'll note that wind farms vary from 0.24 watts/m^2 (Pierce County, N.D.) to 5.3 watts/m^2 (Braes of Doune, Scotland). I think land prices, more than turbine capability, is driving the energy density of these farms.

Note that the wind power map above quotes wind at 10 and 50 meters above the ground. Back when the Department of Energy began collecting data for these maps, those were considered the likely bounds of practically sized wind turbines. However, the Lamar turbine towers are 70 m tall. It turns out that the tower costs are mostly just steel, and the higher up you go, the faster the wind blows. After the industry got experience with the costs of siting, permitting, building, bird strikes, aesthetics, and so forth, it turned out worthwhile to spend more on steel in the tower and concrete in the foundation. As a result, watts per km^2 has gone up.

Is there a limit? Placing turbines closer together can collect more wind energy, but fundamentally most wind power is still being dissipated as turbulence and then heat higher up in the atmosphere. Bigger wind turbines reach farther up to capture more energy. It is hard for me to imagine that ground-based wind turbines are going to get substantially taller than they are now, and so I do not expect the average power yield to increase much beyond, say, 2 or 3 watts/m^2 average. 2 watts/m^2 across all of North and South Dakota would yield 750 gigawatts, which is why you hear wind advocates claiming that the Dakotas can power the rest of the U.S. They could, if you could transport the electricity to market.

Finally, I doubt very much that, even if windpower is wildly successful, it will ever account for anything like 100% of the U.S. grid's production. If many coal plants are forced out of production by lower cost wind plants, I would expect that some very efficient mine-mouth plants will remain. I will be astonished (and pleased) if wind ever produces half the U.S. capacity. If that ever happens, wind turbines will be a familiar sight, but not an overwhelming use of land.

Jesse also complains that wind turbines take significantly more steel and concrete than nuclear powerplants. Obviously the steel and concrete are factored into the current prices of turbines, so it's already part of the price comparisons being made. There are two future risks to large use of concrete and steel, however:

Wind turbine prices in the future could be more closely tied to raw material prices (which in turn depend on the cost of energy) than on the price of labor (which depends on the state of the economy). This question resolves to whether future wind turbine prices are more sensitive to the cost of imported energy than electricity from coal is. Coal fired electricity is fairly sensitive to oil prices, so I doubt this is a problem.
A large bump in wind turbine construction could use so much concrete and steel that it would distort the markets and cause large price increases.

The second issue got me to pull out the calculator again. Here are Jesse's numbers, actually Per Peterson's numbers, in context of the production necessary to build a 250 GWe average windpower grid (about half U.S. electric consumption):

Steel: 460 metric tons per MWe. The U.S. produces about 90 million metric tons of steel every year. Over the 30 years it would take to build a new US grid, wind turbines would require 1.3 years' worth of production.
Concrete: 870 cubic meters of concrete. The U.S. ready-mix industry produces about 350 million cubic meters a year, so we'd need 0.6 years' worth of concrete production.

These constitute a nice bump to domestic production, but are significantly less that ordinary year-to-year variation.

The bottom line: if the price is right (or even close), let's have all the wind turbines we can build, because it really could help with our foreign trade deficit, economic sensitivity to energy prices, and global warming.

Dumping Quicklime into the Oceans

2008-07-22T08:40:00.000-07:00

Tim Kruger at Cquestrate has an idea for sequestering large amounts of CO2: dump quicklime (CaO) in the ocean.

The basic idea is to convert limestone (CaCO3) and CO2 into calcium bicarbonate (Ca(HCO3)2).

CaCO3 + energy -> CaO + CO2 Burn limestone into quicklime
CaO + H2O -> Ca(OH)2 Dissolve quicklime in ocean to make calcium hydroxide
Ca(OH)2 + 2CO2 -> Ca(HCO3)2 Calcium hydroxide absorbs CO2 to make calcium bicarbonate

Net:
CaCO3 + H2O + CO2 + 178 kJ/mol -> Ca(HCO3)2

The problem is the amount of energy required. Let's say it comes from coal. Typically, you can get 30 MJ/kg out of coal. To get your 178 kJ above, you'll produce a half mol of CO2 just burning coal, assuming perfect efficiency. That's half your benefit gone right there.

But, it's a high temperature reaction (840 C). That means you have to get the reactants (calcium carbonate, coal and coal oxidizer, e.g. air) up to that temperature, react them, then drop the reaction products back down to normal temperature. To get perfect efficiency, all of the heat from the cooling products has to be transferred to the reactants. There is going to be some loss.

Let's say you lose 25% of the coal heat, and 75% goes to making quicklime. Then, for every 2 kg of coal burned, you will eventually absorb the CO2 that was produced by burning another kg of coal somewhere else.

Bottom line: we'd have to triple the rate at which we burn coal to get carbon neutral with this scheme. That's not practical. It'll get better if we use natural gas or oil, but it won't change the basic calculation that we'd have to multiply our existing consumption of fossil fuels to get carbon neutral.

Now, if someone wants to tell me about a scheme in which limestone is burned in a solar furnace to make cement, I'm all ears. CO2 sequestration from such cement manufacture makes more sense than it does from coal-fired powerplants, because limestone burning (no air) releases pure CO2, whereas coal burning releases CO2 mixed with lots of nitrogen from the air. However, there are lots of other problems.

Sigh. We're not getting out of this mess easily.

The Pickens Plan

2008-07-15T00:11:00.000-07:00

Check out the guy's website, if you haven't already. There is not a lot of meat there. Basically, the idea is that if we build enough wind turbines to provide 20% of our electricity, we can reduce the amount of natural gas that we burn to make electricity. This natural gas can be used to power special new cars, which will reduce our imports of petroleum.

Mr. Pickens' chief aim is to reduce U.S. petroleum imports. That's great, because that's the energy policy issue I care about most, too. However, I see two problems with his plan:

As things stand now, large fast changes in wind turbine output will have to be accomodated by throttling natural gas turbines. Gas turbines cannot throttle down to zero power efficiently. So, even when the wind is blowing a large amount of power will have to come from gas turbines running at partial throttle ready to take over if the wind cuts out. If wind is supplying 20% of our domestic power, these partial-load gas turbines will have to supply some similarly large amount, and as a result there may not be a large amount of gas actually saved.
I don't forsee a switch to compressed natural gas burning cars. I suspect it would be cheaper and have a larger, more immediate impact to convert the natural gas (and some coal) into gasoline in a refinery, and then feed that into the existing transportation system.

I have two humble suggestions for Mr. Pickens, or energy policymakers.

1. Switch home heating to electric heat pumps.

In 2006, 5 billion gallons of distillate fuel oil was sold to residential users, almost all of it used to heat their homes. Ignoring refinery gain, this is 160.8 million barrels, or about 3.6% of the 4.5 billion barrels of oil imported that year.

Nearly all the houses heated by distillate fuel oil have grid electricity. These houses can be upgraded to air-source heat pumps for a few thousand dollars each. Electricity can come from coal or natural gas, either one of which is better than petroleum. The economics are probably already there for the switch, so some public education and low-cost financing should push homeowners to embrace heat pumps en masse. This can happen a lot sooner than moving the U.S. car fleet to compressed natural gas.

This switch can reduce our oil import bill without requiring the first step of lots of wind turbines. Maybe I'm just nitpicking, but $21.4 billion dollars per year (for the 160.8 million barrels imported) seems like an interesting amount of money.

2. Make air conditioners work on intermittent electricity

This is also known as "Direct Load Control" or "Demand-side Management".

One of the problems with wind energy is that it's intermittent. Increasing the amount of wind generation in the national grid will increase the variation in load that the other generators must accomodate. This will cost money. It will cost less money if the other generators have 10 or 15 minutes to accomodate variation.

Air conditioners and heat pumps naturally store energy. It takes time to cool or heat a building. Usually, the pump cycles on or off every few minutes. If the utility has a fast way to shut down large numbers of compressors for a few minutes, it can filter out much of the short-term variation in load and supply. Instead of throttling gas turbines from 50% to 100%, a few minutes' notice gives the utility time to turn on gas turbines -- from 0% to 100%. That means that the 50% rated capacity that was otherwise being produced by a gas turbine can be produced by a coal-fired turbine instead, which is much cheaper.

This change is a good idea regardless of whether a massive wind turbine build happens, because it will allow utilities to use less natural gas and more coal. That may alarm some folks. Some may see a hidden agenda here. I think if the same bill in Congress mandates Direct Load Control on HVAC devices, and guarantees a production tax credit for all non-carbon domestic sources for a decade, that should assure doubters and put some real fire in the market.

Right now, hydroelectric turbines are the cheapest load-following generation around. They produce just 7.1% of the electricity in the United States (2006). Unfortunately, all of this load following capacity is already used.

For comparison, HVAC uses more than 29% (page 44 here, plus this, both from the EIA) of our generated electricity. Instantaneous control over this much load would be sufficient to accomodate any amount of wind power that we care to build. Of course, the utilities (really the system operators) can't control HVAC, yet. I don't think this is a problem, because we don't have 450 gigawatts of wind turbines yet either.

I suspect the average lifetime of HVAC equipment is around 20 years. If the government mandated that all HVAC equipment sold after, say, 2009 had Direct Load Control features, then we'd see about 15 new gigawatts of Direct Load Control every year. There is little danger of us building wind turbines faster than that in the near future.

Burning coal is burning oil

2008-07-09T00:55:00.001-07:00

I found some numbers for the oil cost of burning coal.

Freight trains in the United States burn 1 gallon of diesel to move a ton of frieght 436 miles.

Average distance coal travels in US: 628 miles from mine mouth to powerplant. At $4.03/gallon, that's $5.80 for the diesel to move a ton of coal from the mine mouth to the powerplant, on average. Wyoming coal costs $9 at the mine mouth. So, electric producers pay almost as much for the diesel to move the coal as for the coal itself. Since marginal petroleum is imported, it's fair to say that coal is not entirely a domestic fuel.

The average powerplant cost for coal in the U.S. in 2006 was $34.26/ton. That's because coal mined outside of the Powder River basin in Wyoming costs a lot more to dig out -- the average mine-mouth price across the U.S. in 2006 was $25.16/ton. The difference is $9.10/ton, which is the cost of transport. The cost of diesel was a bit lower in 2006, but it looks like around half the transport cost is the diesel.

If the coal is 22 MJ/kg, and the plant is 35% efficient, then for each kWh at the powerplant you spend on average 1.8 cents for the coal. Just the fuel cost of the coal plant is more than the total operating cost of the Palo Verde nuclear powerplant, per kWh. This result is entirely independent of subsidies or clean coal. The black stuff is apparently just really expensive.

A while back, I snarkily suggested that mine mouth coal powerplants were a way to keep the pollution away from rich people. Looks like I was wrong:

Transporting a kWh of electricity 1000 miles increases the cost by 19%.
Transporting the coal necessary to make that electricity 1000 miles costs $14.49/ton, assuming cost is linear with distance. That's a 58% increase in the cost of the fuel. Assuming the fuel cost is 70% of the cost of producing electricity, that's a 40% increase in the cost of the electricity.
4000 miles (across the continent) by electricity: increase cost by 107%.
4000 miles by coal train: 160% increase.

What about the extra carbon? Transporting 1000 miles as electricity means you must make an extra 8.7% more electricity which gets lost in the wires, which produces 8.7% more CO2. Transporting 1000 miles by coal train burns 6.3 kg of carbon in the diesel to deliver perhaps 800 kg of carbon, which increases the total carbon released by 0.8%. Clearly the diesel locomotive is the lower carbon, if much more expensive, alternative.

Average distance coal travels in China: 230 miles. They're burning a lot less diesel to take advantage of their domestic coal.

Keep women away from stairs!

2008-06-29T13:45:00.000-07:00

I have summarized for your convenience the top 7 consumer killers in the United States in the year 2001, and swimming pools, for comparison. I think the conclusion here is inescapable: women must be kept away from stairs. This is a significant issue for me because I live in a house with two stories and a basement, with my wife and three daughters. Although the statistics presented are not specific, it does appear that the problem is largely with older women, so we'll definitely have my mother in law stay in the downstairs bedroom.

As I write this my two older girls are directly behind me, messing around in the crib that we generally use for our youngest. A quick check shows that I should escort them outside where they can safely fool around in traffic on some ATVs!

total deaths	male accidents	female accidents	category
202104	767142	1274004	Stairs, Ramps, Landings, Floors
45964	248445	291530	Beds, Mattresses, Pillows
30271	203930	252960	Chairs, Sofas, Sofa beds
25023	125312	168238	Bathroom structures and fixtures
24750	414008	151660	Bicycles
21239	169834	38022	ATVs, Mopeds, Minibikes
19085	150667	72498	Ladders, Stools
5322	88864	72894	Swimming Pools, Equipment

CO2 sequestration -- size of the kill zone

2008-06-25T21:33:00.000-07:00

Sometimes, the underground reservoirs that store natural gas explode. Drilling wells into them makes this more likely. When wells explode, the gas generally ignites, making a spectacular flame that can be seen for miles. Aside from the loss of valuable fuel and equipment damage, well explosions generally aren't too big a problem for people living nearby.

One less noteworthy effect of a well explosion is that the CO2 generated from the combustion of the methane is carried high up into the atmosphere by the heat of combustion, where it is mixed by high-altitude winds (routinely 100 MPH).

One plan for CO2 sequestration from coal-fired powerplants is to inject the CO2 into old, empty gas wells. Like the methane, the CO2 is in a supercritical state in the well -- not so much a liquid as a very dense high pressure gas.

The difference between CO2 and CH4 comes when the well explodes. CO2 does not start a fire. Instead, it expands, and cools, and the cold CO2 will flow with the wind, against the ground, eventually dissipating.

A 1 GW (electrical) coal-fired powerplant will burn 2.2 GW (thermal) of coal (because it's about 45% efficient). That's about 7000 metric tons every day. It will produce 4.7 cubic kilometers of carbon dioxide per year, at standard temperature and pressure. That CO2 is fatal to mammals at concentrations greater than 4%.

So, if a sequestration field explodes after 10 years of sequestering the output from a 1 GW coal plant, it will create an invisible blob of CO2 that will be at least 7 km across before it dissipates to the point of being nonlethal.

Think about this thing for a bit. CO2 inhalation is fatal within a couple of minutes, and I suspect it is disabling well before that. Who is going to detect this blob of gas before being overcome? You cannot see it. You cannot run from it. You cannot stay indoors to escape. You cannot start your car to drive away from it. As the wind wafts it across the scenery, it kills every animal in its path. It could go for 50 kilometers or more before wind shear mixes it with enough air to become safe.

Not in my back yard, if you please.

Anya's Gift

2008-06-09T15:59:00.001-07:00

For Anya's 6th birthday, we had a huge party. Over 50 people came. It was a blast.

We've been trying to reduce the accumulation of toys in our house, and presents from that number of people was going to be a problem. So, we told people not to bring presents, or if they did, bring something suitable for the Ronald McDonald house, which is a temporary home for the families of kids undergoing serious treatments at Stanford Hospital.

If anything, the haul got better (oy! consumerism). Here is Anya delivering her presents to the charity.

Discovery Launch

2008-06-02T08:20:00.001-07:00

I just got back from watching the Discovery launch. My boss, Ed Lu (former 3-time astronaut, second from left), hosted us, which really made the experience for me because he was able to introduce us to lots of folks. Every time we walked into a restaurant, and every 5 minutes while we were at Kennedy Space Center, someone would smile and come over to talk with Ed. NASA doesn't pay well and most folks don't get to try wacky things like we do at Google, but they seem to have great interpersonal relationships. It's heartwarming to see.

On launch day, we were 3 miles from the pad at the media site. This is as close as you can get. We had a lot of waiting around to do. Here is a cherry spitting contest.

I know there is a great deal of speculation out there about whether hacking on camera hardware at Google makes one a babe magnet. While such question are only academic for me personally, I can tell you that getting out in the midst of a bunch of media types with some very customized photographic hardware attracts all sorts of attention. I don't actually know who this person is but I think we can all agree she's gorgeous, and she was very interested in the camera hardware and what Google was doing with it.

From our vantage point 3 miles away, the shuttle stack was just a little bigger than the full moon, which meant that the flame coming out the back was about that size too. There have been some comparisons to the shuttle exhaust being as bright as day....

Let me put that myth to rest. After two years of designing outdoor cameras, I can tell you that just about nothing is as bright as the sun. From our vantage point it had more angular size than the sun -- maybe 400 feet long by 100 feet wide, viewed from 3 miles, is 1.5 by 0.5 degrees. The sun is 0.5 degrees across. But the Shuttle plume is not as hot as the sun -- 2500 K at most, compared to 6000 K for the sun. Brightness increases as the 4th power of the temperature, so the Sun's delivered power per square meter is something like 11x larger. Furthermore, most of the light coming from the Shuttle is in the deep infrared where you can't see it, compared to the Sun's peak right at yellow. So my guess is that the shuttle was lighting us up to 9,000 lux illumination. That's twice as bright as an operating room, and way brighter than standard office bright (400 lux). But it's just nothing like the 100,000 lux that you get outside in bright sunlight. Nobody's going to get a suntan exposing themselves to the shuttle. (Yes, the shuttle flame reflects off the exhaust plume, but the sun reflects off clouds, which are much bigger, so there is no relative gain there.)

Anyway, back to the people we got to meet. Here we are at lunch in the KSC cafeteria, the day before the launch. That guy two to my right is... named at the bottom of the blog. Have a guess. He had a really neat retro electronic watch and talked about how much he likes his Segway. Picture was shot by Jim Dutton, one of the F-22 test pilots who is now an unflown astronaut.

Here's a terrible picture of Scott Horowitz (former #2 at NASA, the guy who set the direction for the Ares rockets and Orion capsule) talking with Ed. The two were talking about their airplanes, a subject that gets both of them fairly animated ("I love my airplane. It's trying to kill me.") Sadly, Ed's plane was subsequently destroyed by Hurricane Gustav (while in a supposedly hurricane-proof hanger) later this year.

Sorry about the quality, it was incredibly crowded and Ed and Scott weren't posing. This was on the day of the launch. Scott came out and looked at our Street View vehicle, then narrated the launch for us. Scott is a former 4-time astronaut and has a great deadpan delivery ("okay we just burned off a million pounds of propellant"); he's probably done it a hundred times.

Here's Mike Foale, who Ed has closed the hatch on twice (that means Mike was in the crew after Ed at the ISS twice).

I enjoyed meeting the people and looking at the hardware quite a bit more than the spectacle of the actual launch itself. Basically, the Shuttle makes a big white cloud, climbs out, loud noises ensue, and within two minutes you can just make out the SRB seperation with your unaided eyes, and it's gone. The Indy 500, for instance, is louder, and more interesting because there are always going to be crashes and various anomalies, which are not usually injurious and therefore lots of fun for the crowd. After meeting all those competent people who are working so hard to thread this finicky beast through a loophole in Murphy's law, I was just praying the thing wouldn't break on the way up.

P.S. That's Steve Wozniak, cofounder of Apple Computer.

How GPUs are better than CPUs

2008-04-29T08:12:00.000-07:00

Intel has a great CPU core right now, AMD does not, and in combination with Intel having higher-performance silicon, Intel is currently beating AMD handily. Meanwhile, Intel and AMD are both integrating graphics into the CPU and NVidia probably feels sidelined. So NVidia says that the CPU is dead. I agree, a little.

Many things people want to do these days are memory bandwidth limited. Editing/recoding video, or even tweaking still pictures and playing games are all memory bandwidth limited. GPUs have far better memory bandwidth than CPUs, because they are sold differently.

The extra bandwidth comes from three advantages that GPUs enjoy:

GPU and memory come together on one board (faster, more pins)
point-to-point memory interface (faster)
cheap GPU silicon real estate means more pins
occasional bit errors in GPU memory are considered acceptable
GPUs typically have less memory than CPUs

When people buy CPUs, they buy the memory seperately from the CPU. There are 2 chip carriers, one socket, a PC board, and one DIMM connector between the two. In comparison, when people buy GPUs, they buy the memory and the GPU chip together. There are 2 chip carriers and a PC board between the two.

CPU memory interfaces are expected to be expandible. Expandibility has dropped somewhat, so that currently you get two slots, one of which starts out populated and the other of which is sometimes populated and sometimes not. The consequence is that the CPU to DRAM connection has multiple drops on each pin.

GPUs always have one DRAM pin to each GPU pin. If they use more DRAM chips, those chips have more narrow interfaces. Because they are guaranteed point-to-point interfaces, the interfaces can run at higher speed, generally about twice the rate of CPU interfaces.

CPU silicon is optimized for single-thread performance -- both Intel and AMD have very high performance silicon. As a result, the silicon costs more per unit area than the commodity silicon the GPUs are built with. The "programs" that run on GPUs are much more amenable to parallelization, which is why GPUs can be competitive with lower-performance silicon.

It turns out that I/O pins require drivers and ESD protection structures that have not scaled down with logic transistors over time. As a result, pins on CPUs cost more than pins on GPUs, and so GPUs have more pins. That means they can talk to more DRAM pins and get more bandwidth.

All of the above advantages would apply to a CPU if you sold it the same way a GPU is sold. The final two advantages that GPUs enjoy would not apply, but are easy to work around.

The first is the acceptability of bit errors. GPUs do not have ECC. It would be easy to make a CPU/GPU that had a big wide interface with ECC.

The second is the memory size. GPUs typically connect to 8 or 16 DRAM chips with 32b interfaces each. It would be straightforward to connect with 64 DRAM chips with 8b interfaces each. If fanout to the control pins of the DRAMs becomes a problem, off-chip dedicated drivers would be cheap to implement.

So, I think integrated CPU/GPU combinations will be interesting for the market, but I think they will be more interesting once they are sold the way GPUs are sold today. Essentially, you will buy a motherboard from Iwill with an AMD CPU/GPU and 2 to 8 GB of memory, and the memory and processor will not be upgradable.

For servers, I think AMD is going in the right direction: very low power (very cheap) mux chips which connect perhaps 4 or even 8 DRAM pins to each GPU/CPU pin. This solution can maintain point-to-point electrical connections to DIMM-mounted DRAMs, and get connectivity to 512 DRAM chips for 64 GB per GPU/CPU chip.

Fountain Prototype

2008-04-20T22:26:00.000-07:00

Martha and I are building a pool in the back yard. In that pool will be hot tub, and pouring into that hot tub will be a fountain. I want lots of water flow, and curves, especially since the overall pool will be rectangular (due to the automatic cover). To give you an idea, here's the pool:

The hot tub is circular, and has a 1 foot thick wall that seperates it from the pool. Out of the center of that wall, water will leap up, arch over, and fall into the tub. This will pour nicely over your shoulders if you are an adult, and it will make a fancy tube to explore if you are a child.

The trouble is that nobody sells a curved fountain like this. No problem, I'll just assemble it from a number of straight sections. Also, I do not want to use high-pressure pool pumps for this thing. Instead, I want to use low-power, low-pressure pond pumps. The manufacturer of the fountain has specs for the amount of water flow you need, but not the pressure. I smell project risk. Time for a prototype. Here's the overall arrangement: two fountain units, 1 foot wide each, one Sequence 4200seq12 pump, and some pipes to move the water.

I've got a flow gauge, two pressure gauges, and a ball valve so I can figure out how many gallons per minute throws the water how far.

I've also got a peanut gallery. They're interested because they're going to get to dance around in the water in a bit.

The fountains throw water about as far as the manufacturer claims. Note that my flow rates are for two 1 foot units.

Flow rate	Throw	Notes
48 GPM	26.0 inches	7 inch rise
45 GPM	23.5 inches
41 GPM	18.7 inches
37 GPM	14.7 inches
35 GPM	11.5 inches	3+ psi pressure drop

I learned a bunch of things from this prototype:

The flow through the two units was not identical. One moved about 8% more water than the other, and threw the water a little further.
The flow through each units was not uniform. The unit throwing farther was throwing farther on one end.
With no fine filtration, and just a skimmer before the pump, the fountain units quickly accumulated debris that interfered with the flow.
The water sheet from each unit contracts from surface tension as it gets farther from the fountain. A 14 degree included angle between the two units turned out to roughly match the contraction, but this still left a constant gap from one to the next. I may try to fix that by mitering the two fountains together.
Martha and I agreed that 15 or 20 GPM per linear foot is not enough. We really like 25 GPM/foot better.
The fountain water entering the water surface was the cause of all the noise. The pump was really quiet, and you could only hear it when you walked right over to it.
The pump really doesn't prime itself. I had to stuff a hose up the intake and fill it full of water before the pump would move anything.
This pump can just move 48 GPM with this setup (which implies it is seeing about 5 feet of head). With more angles and losses in the system, I am going to need more pressure at that flow.

I also noted that the water sheet was rough. Water entry was noisy. I took a high-speed shot of the water, and sure enough, it's breaking up in flight. Note also how much shorter the rear fountain is than the front.

I noticed that the flow gauge was bouncing around a fair bit, so I presume I'm getting a bunch of turbulence, which probably does not help the fountains at all. These units are the "short lip" version of these fountains, which means they have just 1" of flow straightener before they launch the water. The standard version has a 6 inch lip, which I think might damp the turbulence more and lead to a cleaner sheet of water.

Inside the unit there are apparently 3 supports of some sort. These have visible wakes, but I wasn't able to see that the wakes caused more breaking up when they hit the edges.

So, my plan is not yet validated.

I need bigger pumps. 3 of the 5100SEQ22 will produce 200 gpm total at 10' head. That should give me enough extra force to push through the extra twists and turns.
Each fountain unit is going to need it's own throttle. The best way to implement this is probably a bank of eight $20 ball valves, and a seperate run to each fountain unit.
As long as I'm doing a seperate run to each fountain unit, I might arrange for the final connection to be long and straight to reduce turbulence. There will be a lot of turbulence in the fountain unit itself, so maybe this is hopeless.
I should order a fountain unit with a 6" lip, and see if I like that flow better.

Conservation versus outsourcing

2008-04-08T08:31:00.000-07:00

Read "The Wonderful Curse of Natural Gas Price Volatility". It's short, just 12 pages long.

Check out the graph at the top of page 9: "U.S. Industrial Gas Demand Destruction". That's a 22% drop in industrial natural gas utilization between 1997 and 2006. That's not efficiency, that's offshoring! What's going on here?

Natural gas is a feedstock for the fertilizer, chemical, and plastics industries, and a fuel for the electric generation industry.
Electric power generators are less sensitive to the price of their fuel than fertilizer, ethanol, and plastics, since the latter three can all be shipped to us oversea, and electricity cannot.
The electric generation industry is sensitive to the capital necessary to build capacity, because the rent on the capital to build their plants has to be priced into the electricity sold, and different plants do compete to produce and sell electricity. Thus, more capital-intensive plants are more likely to have lower return on investment if electricity prices dip.
Gas turbine power plants have exceptionally low capital costs, making them very desirable to the power producers, and gas prices were low during the 1980s and 90s.
So, electric generators built 200 gigawatts of gas turbine powerplants during the 1990s and early 00s, so that gas turbine plants now constitude 41% of our nameplate capacity (EIA figures). These gas turbine plants are now running at a capacity factor of 21%, and produce 20% of our domestic power (once again, EIA).
Figure 7 of page 8 of the Ventyx report shows that between 1997 and 2006, gas consumption by the power generators rose from 11 to 17 billion cubic feet a day. That's all those gas turbines coming on line.
It turns out there is a limited supply of domestic natural gas. Demand rose, supply stayed constant, and thus prices rose.
Over the same time, industrial consumption dropped from 23 to 18 billion cubic feet a day. That's domestic fertilizer, chemical, and plastics production being moved overseas in response to higher feedstock costs.
U.S. consumption of fertilizer, chemicals, and plastics has not dropped, and conversion from the feedstock to the final product increases value, so offshoring has driven the jobs overseas and also increased our trade deficit by much more than the cost of the natural gas consumed by the electric generation industry.

What we have here is another example of a strong negative correlation between the performance of the U.S. power generation industry and the U.S. economy as a whole. This is a tragedy, partially responsible for our $708 billion dollar/year trade deficit. That's an unpaid $2360 bill, per man, woman, and child, per year, for everyone in the United States.

This post and the last one may lead some of you to think I'm all for a command economy. No. I'm pretty sure that if we nationalized the electric power generation industry, we'd end up running it less efficiently, which would also lead to higher domestic power costs. I do think we need to bring the measure of performance of the electric power generation industry into better alignment with the domestic economy.

The domestic economy does well with cheap energy. In this context, gas turbines are a disaster, since they redirect a feedstock away from high-value-added uses (plastics) into low-value-added uses (electric generation). We have readily available substitutes for electric generation (coal and nuclear), but not natural gas. In some sense, all a gas turbine does is convert one kind of energy into another without increasing the domestic supply.

I don't know how to make domestic power producers profit more when the US economy has cheaper energy. The benefit of marginally cheaper power is probably nonlinear, and possibly unmeasureable in any way that would allow accountants to calculate a credit to power producers. I do not want to see more coal powerplants, because of the currently externalized cost of CO2 production, even though they are a cheap source of power. Perhaps the simplest way forward is what we have now: tax credits or subsidies for the obvious answers, like wind and nuclear, and just feel our way through, year by year, guessing which subsidies will distort the electricity market to best serve the interests of our citizens.

I'm sorry to keep harping on this energy and trade stuff, but to be honest, I'm scared. I don't understand how to predict what this trade deficit will do, nor do I understand how big is too big, but $700 billion feels too big. Our trade deficit, national budget deficit, credit crisis, housing market meltdown, and war in Iraq give me the feeling that this nation has derailed and is about to make a very expensive and possibly bloody mess.

The last time we got into a World War, we had just splurged on national infrastructure. Think about this: 90% of the Allied aluminum flying over Germany was made with power from the Grand Coulee Dam, built from 1933 to 1942, i.e. just in time. I'm not saying I expect another World War, but I am saying that when times get tough it's good to have serious infrastructure in your back pocket.

Let's drive electricity prices into the ground

2008-03-26T06:10:00.000-07:00

Read this report. It's basically a big apology for why electricity prices have been going up.

On page 31, it shows the EIA estimate that a 10% increase in the price of electricity in 2006 would cause a 4% (175 billion kWh/year) drop in electricity demand in 2014, down from 4.2 trillion kWh/year. This is basic supply and demand, with the EIA doing the error-prone work of predicting the demand curve in the future. The first thing I'll note here is that a 10% price increase, coupled to a 4% sales drop, leaves a 6% revenue increase (at least $12 billion/year) coupled with decreased costs for the folks selling electricity. It's an inelastic demand curve. So, if the folks making electricity can do anything to reduce the overall supply, it's well worth their effort.

When the price of electricity goes up, some of that reduction in demand is accomplished by economic activity (buying a more efficient air conditioner), and some is accomplished by reducing economic activity (shutting down the night shift of a marginal plant). Overall, how much of each? My guess is that the reduction in economic activity is the main reducer of demand. Let's suppose I'm right, and that a 4% drop in electric demand is accompanied by a 1% drop in GDP. That's a $130 billion dollar drop.

You can see that price fixing among electricity producers would be seriously damaging to me and you. It is in the national interest that electricity prices not rise 10%. Note that this is true regardless of whether the utilities make or lose money, because as a nation we are making or losing quite a bit more money than the utilities are.

So let's consider a different investor, the U.S. government. Suppose that the electric demand curve slope is locally smooth. A 10% decrease in the cost of electricity, then, should lead to a 4% increase in sales, and a corresponding 1% increase in GDP. This is what Rod Adams is talking about when he calls electricity an economic lubricant.

How much is that 1% increase worth to the federal government? They tax the GDP at about 18.4%, so it's worth around $24 billion per year. To review:

A 10% decrease in the cost of electricity, from $0.07/kWh to $0.063/kWh, would lead, 10 years later, to
...a 4% (175 billion kWh) increase in electricity sales, for a net revenue loss to the industry of
...$12 billion/year. The federal government, however, would be raking in an extra
...$24 billion/year, and the rest of us would be enjoying an additional
...$130 billion/year in GDP.

Sounds good. Let's mandate a drop in prices! Who says we can't have a centrally controlled command economy?

Well, it's not that simple. First, we need to know much investment is required to drive electric prices down 10%. Presuming that the government has to somehow compensate utilities for taking a $12B/year hit for the team, that leaves $12B/year to pay for the capital required. The federal government currently borrows money for 30 years at 4.5% (they are a better credit risk than you), so the capital required for this investment had better be significantly less than $266B.

The Palo Verde nuclear power plant supplies power for $0.027/kWh, including operations (fuel), maintenance, and interest and depreciation costs. In 2002, the marginal cost (not including capital) was 42% less than that for coal in the area, and since then the difference has increased as coal costs have risen. This is the best lever we can use to drive down electricity prices.

To drive down wholesale prices by 10%, we'd need to bring the cost of production down approximately 10%. Using the Palo Verde area numbers from this report, and assuming we keep the same coal and hydro production (as they are both low cost), but reduce gas and increase nuclear, we'd need 49 gigawatts of new nuclear production nationwide. That's not going to happen by 2014, but we would probably see some fraction of the benefit for some fraction of the cost. Just incidentally, 49 gigawatts of new nuclear production scaled up from Palo Verde's employment base is 89,000 extra jobs here in the U.S., paying an average of 13% more than the average American salary.

Palo Verde cost $5.9 billion, was finished in 1988, and has a peak capacity of 3.72 GW and sustains a capacity factor in excess of 90%. We would need 13 more Palo Verdes to produce enough electricity to make that 10% cost reduction happen, at a present-day cost of around $120 billion [edited; thanks]. The generating utilities are not going to take this on, given that the "benefit" is a $12 billion/year loss to them. But for the U.S. government, looking at $24 billion/year in increased tax revenue, the cost of the plants is easily worth it. What remains is determining a way to have the government provide the capital and offset the revenue losses associated with a huge expansion of the nuclear reactor fleet, without getting ourselves further into the management disaster of a command economy.

I'll note that we're going into a recession, and interest rates are falling. This is a good (cheap) time for the government to borrow a bunch of money to invest in long term economic infrastructure. The reactor buildout I'm proposing would cost about the same as the $300/person economic stimulus package our leaders just conjured up. To my mind, the difference is very much teaching a man to fish versus giving him fish.

Clinton's choice

2008-03-11T01:19:00.000-07:00

I'm watching replays of the CNN Obama/Clinton debate. This is painful.

The argument that Clinton needs, and is failing to make, is that there is a difference between how Senators and Presidents collect the information they need to make their decisions. The Congress does not have an NSA. The President does. Clinton made her decision, one she regrets, on the basis of information provided by George Bush's team. Had she been in President Bush's position, things would be entirely different because she would have had a completely different set of options, including better discovery of what the facts actually were.

She's not making that argument. I'm not sure why, and it suggests to me that she still doesn't think about how to be a President. She's thinking about how to argue about stuff, not how to find the right answer.

There is another angle that Clinton is missing. To win, the Democratic presidential candidate will have to appeal to some Republicans. What is going to go over better? "I was right, you shouldn't have gone to war, now I'm going to fix your mistake and pin the cost on you?" or "We got into this tragedy together, and I will help get us out of it together?" Obama's Iraq message is actually more divisive.

Finally, for what it's worth, the idea of scheduling a withdrawal scares me a lot. I think our withdrawal from Mogadishu contributed directly to the planning of 9/11. I worry about what we're going to be dealing with in 10 years, and where we're going to be dealing with it.

Dessert Recommendation

2008-02-11T12:38:00.001-08:00

On Sunday night my wife and three kids had the "Lemon Meringue Ice Cream Pie" at the Half Moon Bay Inn. It was one of the best desserts I have ever had. For dinner I had the cheeseburger, also one of the best burgers I've ever had.

I'd like to put in a Google Maps link, but Maps doesn't have it! Half Moon Bay Inn is at 401 Main Street, Half Moon Bay, CA 650-560-9758.

Subsidizing wheat in Afghanistan

2008-02-11T08:21:00.000-08:00

Afghanistan grows most of the world's opium. Opium is technically an illegal crop there, and it is one of the few crops that makes enough money to support a farmer in Afghanistan. If you grow opium, the central government is officially supposed to stop you, and the local official will probably look the other way if you pay him off. It may seem cheaper and easier for the folks growing opium in the Taliban-controlled areas, since the Taliban actively helps farmers sell their crop, in exchange for some of the profit. I'm sure many farmers prefer the Taliban for purely economic reasons.

If wheat sold for more money, perhaps 3 times the world price (which is around $350-$400/metric ton), some folks think the value of the wheat crop would be large enough to encourage many farmers to switch to wheat production. Wheat is legal to grow, so their is no disadvantage for a wheat farmer to having a functional Afghani government. Foreign aid organizations could run grain mills which bought wheat at $1100/ton and sold the flour for $350/ton. Bread prices would presumably stay low as flour flooded the market, and Afghanistan would presumably become an exporter of flour.

Folks in Pakistan and Iran would be encouraged to sell grain to Afghanistan for milling. I'm not entirely sure this is an entirely bad thing. Presumably economic conditions do not vary dramatically as you cross the border, so that areas outside Afghanistan are probably also growing opium. And, as long as we stop bulk cargo deliveries of grain to Afghanistan, one would think it would be expensive to move large quantities of grain by, say, mule across the border. There is some subsidy at which it is not worth moving grain by mule. Hopefully it's cheaper for small Afghani farmers to get their product to the mills than it is for Pakistani importers.

So, how much would this cost? Afghanistan produced 4.4 million metric tons of wheat in 2007/2008, so someone would have to cough up $3.3 billion/year to carry this subsidy. That's real money, and apparently we'd have to keep it up for a decade or so. If there are not large agribusinesses in Afghanistan now, there will be within a year or two. These businesses will get efficient at growing grain in Afghanistan, and start to produce the majority of the grain there. The subsidy on grain will decrease over time, large efficient businesses will capture nearly all of it (as they capture farm subsidies in the U.S.), and the marginal farmers will move back to poppies. I don't have a great deal of hope for this effort.

By the way: anyone have a clue what this is?

Cost of oil, revisited

2008-02-05T02:00:00.000-08:00

Last time I looked, oil was priced at $22/barrel and we were importing 9.14 million barrels a day, which made up 20% of our trade deficit of $374 billion. We were actually importing more, but I hadn't counted the refined stuff. So it was actually 12.6 million barrels/day, so $101 billion or 27% of the trade deficit.

Now, as you know, the oil spot price is around $95/barrel, but $72/barrel is closer to the average price, and we are importing 12.2 million barrels a day (crude plus some refined products). The census bureau has nicely summarized the data here, which doesn't quite match the simple math I would do. For Dec 2006-Nov 2007, they see petroleum imports as $283 billion (35%) of a $813 billion deficit.

Grim.

How much does a plug-in hybrid help?

Over a 20-year lifetime, the car is driven 250k miles.
It gets 75 mpg rather than 25 mpg.
It burns 80 barrels of oil rather than 320 (and burns a bunch of domestic coal instead).
It saves the importation of $15,500 of crude.
It saves the user $23,000 in gas.
It costs the user $5800 in electricity. (250k miles) / (3 miles/kw-hr) * (0.07 $/kw-hr)

My guess is that a practical plug-in hybrid chews up more electricity and gasoline than this, but it still seems pretty good. Unfortunately,

It's made by Toyota in Japan, and costs $25,000, so the net trade debt increases. At least the money is going to a responsible nation like Japan. I will cede that eventually Toyota will make most of these plug-in hybrids here, and so only the profits will go to Japan.
If 10 million cars in the U.S. were plug-in hybrids, it would reduce our oil imports by 282,000 barrels/day, or 2.3%.

That last point is a killer. It is just incredibly hard to replace oil.

Correcting a Newtonian

2008-01-27T22:48:00.000-08:00

Part of the reason that contrast is so bad on my Newtonian is that it has flare. The other reason is that it is uncorrected. Let's see what it takes to correct the thing.

The mirror is a 300 mm diameter diffraction-limited 1/4 wave parabolic mirror. Sounds awesome, especially the diffraction limited part. When viewing 550 nm (green) light, a 300 mm aperture scope should resolve 1.22*wavelength/diameter = 2.2 microradians. With a 1500 mm focal length, those details are 3.4 microns across on the image plane. My Canon 40D has 5.7 micron pixels, which isn't quite going to catch the details.

Sadly, it turns out that even a perfect parabola produces just a single perfectly focussed dot in the center of the image, and resolution goes downhill out from there. One way to measure resolution is to measure the amount of contrast transmitted by the lens at a particular spatial frequency. We could measure transmission at the diffraction-limited spatial frequency (227 line pairs/mm), but we don't need it to be that good. A more useful frequency is the maximum spatial frequency that the camera supports. The pixels themselves sample 87.7 lp/mm. Because the camera has a Bayer filter to sample colors, it has an antialiasing filter, and the maximum frequency it can sample correctly is a factor of 1.8 smaller, about 48.7 lp/mm.

Here's a graph of the contrast you'd expect to transfer, at both 227 lp/mm (diffraction limit) and 48.7 lp/mm (Canon 40D limit). You can see that resolution from a simple parabolic mirror is only good within a small image circle around the center, and there is almost no contrast available at the diffraction limit.

Once contrast drops to zero, there is no detail left at that frequency. Lower spatial frequencies, corresponding to less detailed imagery, will have contrast at larger and larger radii, and so the picture will look more blurry as you get farther from the center. For photographic lenses, I like to see MTF at the maximum camera frequency of something like 30-40% across the whole field, although I'm willing to accept some dropoff at the corners.

Compare the parabolic mirror graph to a similar graph for the Canon 50mm/1.4 lens, in particular, looking at the 40 lp/mm line (the bottom pair). 60-70% MTF. That's a good lens. (I got this graph from photodo.com, which has great data on hundreds of lenses.)

The graphs aren't perfectly comparable, but they're close. The Canon here is stopped down to f/8, which vignettes away the least corrected portion of the aperture. But it performs nearly as well at f/5. Also, this graph is at 40 lp/mm, which is a little easier than the 48.7 lp/mm I'm using to judge the Newtonian. One other detail: in both graphs, there are two lines, one dashed (tangential) and one solid (saggital). Saggital means "in the direction towards and away from the image center", and tangential means"along a curve centered at the image center".

So the reflector looks terrible, but there is hope. Al Nagler at Tele Vue has designed a corrector lens (the Paracorr) that, when combined with a parabolic mirror, gives a well corrected image. I don't have the Paracorr's prescription (I checked the U.S. Patent Office, and found Al's eyepiece patents but no patent for the Paracorr), but I know the basic idea, so I was able to slap something together with Zemax to demonstrate.

Here is the overall scheme: light comes in from infinity from the left, bounces off a parabolic mirror at the far right, and then comes back through a negative doublet, followed by a positive doublet, finally arriving at the image sensor at the far left. I've left out the planar secondary miror that reflects the light out the side, but I've left in the obstruction that it causes. The corrector assembly, as shown, sits just outside the main optical tube. The eyepiece would sit on the other side of the image plane.

When comparing this to a photographic lens, it's best to think of the mirror combined with the two doublets as being the "lens". It actually extends the focal length of the telescope a bit. This picture shows rays bouncing off the primary mirror, going through the two doublets, and arriving at the image plane. Because the doublets are so small relative to the mirror and focal length, it's hard to see the detail.

So, here's the detail. I'm quite pleased with how this turned out: the elements are not ridiculously thick, and there is 50 mm of clearance between the last element and the focus plane, good enough to mount a DSLR (44 mm clearance required) if not a T thread mount (55 mm required). The negative doublet is a bit too close to the mirror, in the sense that it would probably sit right at the edge of the main optical tube, when we'd prefer it to be back a bit so that we can baffle the focus tube so that stray light from the front opening of the tube can't speckle off the doublet.

Designing this wasn't too hard. I left Zemax running overnight doing a global search for an optimum, with no constraints on the glass choice. A real optical designer has more constraints to deal with.

And here's the resulting MTF, polychromatic, no less! This is pretty incredible, I doubt the real Paracorr is this good. It's slightly better, all the way across the field, than the Canon 50mm/1.4. That's astonishing, given that this thing has 7 surfaces (one aspheric -- the mirror) with which to bend the light, compared to 13 in the Canon refractor. Or, compare this to the plot at the top of the post for the performance of the parabolic mirror alone. Night and day.

I think the bottom line is that a Paracorr is a necessary part of a Newtonian telescope, unless it's only used at very high magnifications. Unsurprisingly, the Paracorr is the best-selling product made by Al Nagler's company.