A gentleman by the name of David Fisher has been getting some attention (examples: WSJ, New Yorker, Inhabitat) by describing his design for a new building in Dubai. It would be best for the world if bad ideas like these were ignored and forgotten, but without some knowledge of engineering, it’s not obvious that his ideas are bad.

Fisher’s tower is like a shish-kebab on a vertical skewer, where the skewer is an elevator shaft and the food are the apartments. Each apartment can rotate around the elevator shaft. This alone is perhaps impractical, or ugly, or dumb, but not impossible. If you could find a wealthy fool who wanted to build this, you could probably pull it off.

Where Fisher crosses the line into territory that I defend is with his claims about renewable energy. He says that there will be a wind turbine between each apartment, and solar panels on the roof of each apartment. According to his website, the building will “generate electricity for itself as well as other nearby buildings, making it the first skyscraper designed to be self powered.” As Walter says in The Big Lebowski, “OVER THE LINE!”

Before we even look at the available energy closely, we can be certain that it won’t work. One of the central problems of renewable energy is its low power density. According to the ever trusty Vaclav Smil, wind and solar typically yield 1-10 W/m^2; skyscrapers require in excess of 1000 W/m^2, (Energy in Nature and Society, pp. 311, 317). But perhaps Mr. Smil is wrong. Let’s take a closer look.

Judging by the drawings of Fisher’s tower (since removed), it would be about 300 x 50 m. Ignoring the narrowing of the tower as it rises, roughly 20% of the area is devoted to wind turbines. That’s around 15000 x 0.2 = 3000 m^2. (Fisher has described two versions of the tower, one at ~300 m with 60 floors, another at 420 m with 80 floors. Here, I analyze the shorter of the two.)

Fisher claims that the average wind speed in Dubai is 16 km/h, or 4.4 m/s.

Assuming a Rayleigh distribution for the wind speed, the average power available as kinetic energy in the wind is (6/pi) * 0.5 * (density of air) * area * (average velocity)^3.

The density of air is 1.2 kg/m^3.

That’s (6/3.14) * 0.5 * 1.2 * 3000 * (4.4^3) = 290 kW. If the wind turbines were 30% efficient, which would be pretty good for a vertical axis turbine stuck in a building, the yield would be 100 kW.

This ignores the narrowing of the building, the lack of wind near the ground, and obstruction from other buildings.

The building has around 50 m * 50 m * 60 floors = 150000 m^2 of floor space, so the areal power density is about 0.67 W/m^2. Say a room is 5 m in a side, so it has area of 25 m^2. That gives you 17 W per room.

But let’s not leave out the solar power! Fisher claims that 20% of each roof will be exposed to sunlight. On average, then, if photovoltaics yield around 1 W/m^2, we should expect a power density based on floor area of 0.2 W/m^2, which is another 5 W per room, 22 W total. That might be enough to light a single compact fluorescent light bulb in each room.

Oh, and the average temperature in Dubai is 27 C. I guess they can run the air conditioning when all the lights are off.

I should end by saying that I share Mr. Fisher’s enthusiasm for renewable energy. My concern is that his tower of epic fail gives the work that I spend all day on a bad name. We should be building wind turbines and installing solar panels as fast as we can, but we should do it in ways that optimize their performance. Put the solar panels where they will never be shaded by the floor above them, and put the wind turbines on ridgelines where the wind is strongest. Integrating turbines and panels into buildings with the expectation that they will produce energy to spare is moronic.

(And all you energy reporters should be ashamed of yourselves for repeating Fisher’s void claims without any skepticism. That means you, Paul Goldberger and Evelyn Lee!)

Here are a couple little code excerpts that took me some time to figure out. I’m hoping that Google might help the rest of the world’s MSP430F2012 programmers save 5 minutes. (If they all find it, a total savings of 55 minutes!)

The MSP430F2012 defaults to a clock speed of 1 MHz, sourced from an onboard DCO. In order to get the DCO to be accurate, you have to load calibration constants from flash.

BCSCTL1 = CALBC1_1MHZ; // DCO calibration: set range
DCOCTL = CALDCO_1MHZ; // DCO calibration: set DCO step and modulation

Then you can initialize the timer to count in increments of 100 ms.

TACCTL0 = CCIE; // CCR0 interrupt enabled, compare mode
TACCR0 = 50000;
TACTL = TASSEL_2 + ID_1 + MC_1; // SMCLK as source; divide by 2; up mode

Anyway, I hope this is useful to someone out there.

Philip Taubman had an interesting article on the front page of the New York Times yesterday: “Top Engineers Shun Military; Concern Grows.” The article profiles an engineer by the name of Paul Kaminski who worked for the Air Force designing planes for several decades. Kaminski now heads a task force that is attempting to deal with the difficulties the military is having recruiting engineers. According to Taubman, the number of engineers working for the Air Force has decreased 35-40% over the last 14 years. The reasons cited for the decline include:

• better pay in high tech firms
• more cachet at Google or the like
• more engineering students from foreign countries who can’t get security clearances
• lack of exposure to new technology in the military

Strangely, Taubman omits what I suspect, perhaps foolishly, is the central cause– top engineers are driven to solve problems. As I consider the central problems facing the world today, I do not notice an alarming lack of weapon systems. The US military is already extremely good at killing. If you’re really a top engineer, you can choose where to work. I can’t imagine why someone would be drawn to weaponry when there are so many obvious unsolved problems elsewhere.

As an interesting footnote, the article gave no hints of what Mr. Kaminski’s task force will do about the lack of people willing to carry out the jobs they have in exchange for the salaries they offer. One solution might be to stop trying to build so many damn weapon systems.

I have told my sons that they are not under any circumstances to take part in massacres, and that the news of massacres of enemies is not to fill them with satisfaction or glee. I have also told them not to work for companies which make massacre machinery, and to express contempt for people who think we need machinery like that.

–Kurt Vonnegut, Slaughterhouse Five

I am periodically accosted at parties when someone mentions to a friend that I work on renewable energy.

“You there, always talking about renewable energy and solar cells and all that! Why haven’t you solved this greenhouse problem yet?”

The problem is one of scale. To explain what I mean, I have to talk about a sculpture.

Arthur Ganson has a sculpture at the MIT museum consisting of a 12-stage geartrain, where each stage reduces the speed of rotation by a factor of 50. The left end is spinning furiously at around 200 rpm; the right end is embedded in a concrete block. The end in the concrete makes one revolution every 2 trillion years or so.

(You can see a video of the sculpture at the 8:30 mark in this video from the 2004 TED conference, but finish reading this first.)

I can see that the gear at the left end of the sculpture is spinning. After three or four 50:1 reductions, I can only see the gears moving if I watch for a while. When I think about gear reductions in the abstract, I think, “Sure, if you reduced the speed enough, it wouldn’t break the concrete,” but when I look at the real thing, it’s baffling. I stand there looking at the sculpture, knowing that I should expect to see what I’m seeing, but my weak human mind can’t adjust its expectations.

In the same way that when I look at Ganson’s sculpture, I can’t understand what I’m seeing, it’s hard for us to grasp on a visceral level the difference between the 1000 watts Americans use in their homes, the 1,000,000,000 watts we generate in a large power plant, and the 15,000,000,000,000 watts that we use globally.

We hear news of advances in renewable energy. The amount of installed wind power has been growing at around 30% for the last two years. Investment in renewable energy startups is through the roof in the last 2 or 3 years. The news we hear of huge investments, the technological breakthroughs, and Prius drivers loading up with compact fluorescent bulbs at Costco are the first gear spinning wildly (well, maybe not the people loading up the bulbs– they’re just excitable).

Yet on the global scale, the vast majority of our energy comes from fossil fuels. Even after 30 years of work on photovoltaics, the global installed capacity is around 8 GW, or roughly 1/2000th of the energy we use globally. Windpower is about ten times larger, but still only approaching 1% of global energy usage. (I’m ignoring the differences between installed capacity and actual production here, but that correction just makes the fraction of renewables even more slight.)

What’s more, the concrete block end of the spectrum is not reported in the news (rightly so, as it’s not interesting). The massive juggernaut of fossil fuel infrastructure continues to expand. Installation of large natural gas turbines is proceeding in China at more than 1 GW per week, which is enough to match the entire history of photovoltaics installed worldwide in 2 months.

What’s the result? We think we see progress–the gear spinning wildly–but if a global switch to renewables actually happens, it will take a lot longer than our scale-limited minds expect.

Aspiring amateur agrarian, Ben speculates that his engineering friends who dream of becoming farmers may be engaging in “subconscious rebellion against the rampant specialization of modern life.”

I think he’s right, but for me, it’s not subconscious.

An old friend of mine, who worked as a farmer in Maine, once quoted Emerson to me to explain his motivation. He wrote, “When people ask me why I work on a farm, the best answer I can give is that once I read Ralph Waldo Emerson’s essay entitled, “Man The Reformer” and I found it to be so compelling, so resonant, that I could not ignore it.”

He then quoted from the passage below:

“But the doctrine of the Farm is merely this, that every man ought to stand in primary relations with the work of the world, ought to do it himself, and not to suffer the accident of his having a purse in his pocket, or his having been bred to some dishonorable and injurious craft, to sever him from those duties; and for this reason, that labor is God’s education; that he only is a sincere learner, he only can become a master, who learns the secrets of labor, and who by real cunning extorts from nature its sceptre.”

While I don’t find Emerson’s claim compelling enough to move to the sticks and plant an apple orchard, I do feel compelled to resist the specialization of labor, to the extent that I know how. As my friend Alex once pointed out, none of us are pure– “What are you going to do, smelt your own metal?” All the same, I try to reduce the distance between me and the work done on my behalf in the world.

It’s a curious bind. As an engineer, I’m at the extreme end of specialization, but I’d much rather spend the afternoon repairing a friend’s bureau than working for higher wages that I might pay to a carpenter to repair the bureau.

I had a friend’s mill in my garage for a while a few years ago. I didn’t use it very much, but I spent a fair bit of time doing maintenance on it– rewiring the switchbox to make it a bit neater, replacing some of the crappier fasteners with stainless socket head cap screws, and so forth. I’ll be the first to admit that that sort of behavior is pathological.

Still, taking care of the mill gave me a satisfaction that I’ve found hard to duplicate, despite my work as an engineer. Typically, the manufacture of stuff I design, and hence the care of tools, is performed by machinists, who will work for a lower wage than I do.

I suspect that a good deal of my desire to inject myself into the workings of machines is genetic. My dad, for example, mentioned to me a while back that in the 70’s he wrote a FFT subroutine in machine code (not assembly– he was typing raw hex). It makes me polishing the old mill look rational.

When I was a kid, I remember my grandfather finding a toy van in the garbage on the way to the beach. He replaced the floor in the van and repainted it, and my brother and I got to play with it whenever we came to visit. At the time, I was delighted. Looking back now, doing automotive maintenance on a vehicle too small to drive seems odd.

Regarding specialization, Wendell Berry wrote in 1977 in The Unsettling of America:

The disease of the modern character is specialization. Looked at from the standpoint of the social system, the aim of specialization may seem desirable enough. The aim is to see that the responsibilities of government, law, medicine, engineering, agriculture, education, etc., are given into the hands of the most skilled, best prepared people. . . . The first, and best known, hazard of the specialist system is that it produces specialists - people who are elaborately and expensively trained to do one thing. We get into absurdity very quickly here. There are, for instance, educators who have nothing to teach, communicators who have nothing to say, medical doctors skilled at expensive cures for diseases that they have no skill, and no interest, in preventing. More common, and more damaging, are the inventors, manufacturers, and salesmen of devices who have no concern for the possible effects of those devices. Specialization is thus seen to be a way of institutionalizing, justifying, and paying highly for a calamitous disintegration and scattering-out of the various functions of character: workmanship, care, conscience, responsibility.

The disintegration of workmanship, care, conscience, and responsibility is what drives me to resist the deepening of specialization. I want to avoid the conclusion that stuff should be left to “the experts.” No need to fix your toilet, a plumber will do that. No need to drag your trash to the curb, the condo manager’s henchman will do that. No need roust your corpulent form from its slumber, your mechanized exoskeleton will do that.

This next paragraph is a bit of tangent, but it’s a good story and a metaphor as well. My experience has been that you can achieve more than you might expect through severe effort. Around 1998, Oliver, Alex, and I were trying to move a very heavy, slate-topped lab bench from a quonset hut across some dirt and weeds into a workshop. We tried moving the table, and only managed to move it a few inches on the first attempt. Oliver and I started talking about going to get a furniture cart, or a dolly, or maybe a sled of some sort. Alex broke in and said, something like, “We’re not getting a cart. Just push harder. Come on. Push.” This effort was successful and taught me a good lesson about the use of force.

I’ve found repeatedly that my overly-specialized contemporaries generally assume that anything more difficult than lifting a coffee pot should be left to professionals. A few weeks ago, I was helping my parents clean some junk out their basement when we came across the trestle built from 1×3’s from an old worktable that would make good fodder for our woodstove. My mom made a comment about needing some tools to disassemble the trestle. I was able to wrench it apart in less than 30 seconds.

Sometimes I feel like I’ve discovered a lost secret. “No, really, you can sharpen knives by hand with a stone.” “No, really, you can make your own Ethernet cable that’s as long as you want. You just crimp the wires like this.”

The feeling of doing good work yourself is surprisingly liberating, and a little sample breeds a taste for more. After a little while, you’re in danger of attempting to reject industrial society entirely. As Wendell Berry writes at the conclusion of his 1993 essay, The Joy of Sales Resistance, “When the inevitable saleswoman comes to tell me that I cannot be up-to-date, or intelligent, or creative, or handsome, or young, or eligible for the sexual favors of so fair a creature as herself unless I buy these products, dear reader, I am not going to do it.”

Oh, also: I paid $4.20 for a gallon of diesel this week.

“Ultimately, my goal is to work at a small engineering company developing alternative transportation technology– projects like the solar car, but more practical.”

That was the first sentence of the second paragraph my graduate school application essay, submitted July 27, 1999.

7 years and 1 month later (August 27, 2006), I started working at GreenMountain Engineering. It took another 5 months before I was actually working on an alternative transportation project (a battery pack for a hybrid bus). I developed the goal a year or two before applying to graduate school. In total, it was a few months less than 10 years ago that I decided I wanted to do more or less what I’m doing now.

Maybe engineering is easier than programming.

Ten years from now? I hope that some of my efforts will have been successful. I hope it won’t be normal for my fellow Americans to drive cars with an average fuel economy of less than 30 miles per gallon, and I hope that some of our 140 servants will have been replaced with renewable sources of energy.

A more modest hope, given the hullabaloo on Wall Street this week, is that I’m not compelled to load up on handtools and firearms and head to the tropics before the Hard Times arrive.

Gotta focus on “losing the apocalyptic mindset,” in the words of a friend . . .

Hard times evangelist Ben Polito asked an interesting question on his blog a week ago: “Why is it that even people who care about [global warming and oil supply issues] don’t actually make relatively simple choices that could significantly reduce their impact?”

I’ve wondered about this myself. Our behavior is complex, but I think the answer is that we are accustomed to the idea that environmental problems can be solved by marginal changes. There are two ideas here– that our behavior is guided by our expectations of what sorts of behavior are customary, and that marginal changes can solve big problems.

Our yard is an example of the first idea. We live near the corner of two streets with a decent amount of pedestrian traffic and near a convenience store. The result is that trash is thrown in our yard at a rate of a few liters per month. There are two trashcans near the convenience store (and I don’t really know that the trash comes from the patrons of the convenience store), but people definitely throw trash over the fence into the bushes in our yard on a daily basis.

Mysteriously, of the thousands of hours I have spent walking around neighborhoods with other people, I have never– seriously, never– seen one of my friends throw trash in anyone’s yard, and I have never done so myself. I suspect that I live in a culture where littering is unacceptable, but I live in a city where a decent fraction of the population lives in a culture where littering is normal. It’s not that I think about throwing trash on the street every day but decide not to– I don’t even think of it.

To bring it back to climate change: I suspect that most people, even those who care about climate change, don’t think carefully about their levels of energy consumption. They feel worried about sea levels rising and hot summers, but knowing no solar hermits or people who grow most of their own food, they don’t place those among the options. To the question, “Want to see a movie tonight?” they do not answer, “Yes, let’s build a gigantic zoopraxiscope in the backyard.” Instead, it’s “Hmm, we already saw An Inconvenient Truth. How about the new Rambo movie? I know Sylvester Stallone is 61, but I hear he does all the killing with his shirt on.” Options that don’t involve living in a house regulated to 20 °C year-round and driving a car on a daily basis are not on the menu.

The second idea is the strangely common conviction that we can solve large environmental problems with marginal changes to our current behavior. I don’t know why this idea so popular. Suppose Ben invited me over for dinner party, and heavy rains meant that his basement was flooded. If I suggested to the dozen other guests, “Hey guys, I’ve got a great idea. We’ll each take one of these drinking glasses down to the basement and fill it up. We’ll bring them back up and pour the water on Ben’s vegetable garden. If we each do our part, we all win!” I would be correctly regarded as a moron. The problem requires a high capacity pump running for several hours, or hundreds of trips with a bucket, or thousands of trips with drinking glasses.

Our bizarre love affair with hybrid cars is similar. Let’s optimistically assume that hybrid cars can reduce fuel usage per mile by 50%. The real number is probably below 25%, but say the technology works better than we expect, and then assume that every vehicle in the US is instantaneously converted to use a hybrid drivetrain. In the US, at present, our fuel consumption for transportation usage has been growing roughly linearly for the last 60 years [58 kB PDF]. The best we can expect for this massively optimistic, nationwide hybrid conversion is to return ourselves to 1970, but with 40 years of oil gone.

Ben asks what we can do. As he notes, “There’s also a sense in which it is irrational for any one person to make any significant sacrifice in order to change his behavior, on a planet with 6 billion people, the vast majority of them striving to achieve a lifestyle that allows them to consume as much energy and resources as possible.”

In the film metaphor, we need to popularize the backyard zoopraxiscope. Our cultural norms have a time constant around a decade; ideas come and go, and we need to make sure that “Let’s all commute 30 miles in SUVs” is not the only movie to watch.

To his credit, Ben, with his wind turbine and cidermaking, has already begun.

I’ve been commuting by bike exclusively for the last 6 months, even in the snow and ice, and once I adjusted my expectations, it’s fine. We’ve reduced our heating bill by about 30% by using a programmable thermostat; we’ll see what else I can come up with. Our current house is about as well insulated as a milk crate, so there is hope.

We finally released our first product at GreenMountain Engineering. I’ve been working for various different consulting firms (MindTribe, Ideo, and now GreenMountain) over the past few years, and this is the first time I’ve been involved in shipping a product that wasn’t owned by someone else. I feel proud, and I didn’t even do the hard part– most of the development and testing took place in our San Francisco office.

The product is the called the Trac-stat SL1. It’s a ridiculously accurate sensor for measuring how closely your solar tracker is aimed at the sun. I think the spec is 0.02 degrees for the more accurate of the two sensors it contains.

Max and two of his west coast disciples have been testing it at our secret rooftop testing facility in San Francisco for the last few months. (Pretend you don’t recognize the lights of the Giants’ baseball stadium in the background.) The graph below shows the output of the sensor. This was on a tracker of relatively low precision that we have used for a couple of different concentrating solar projects.

Of the many markets that exist for the SL1, the largest is the group of companies that are trying to build concentrating photovoltaic systems. The key point of leverage behind concentrating solar is that if you can gather the same amount of sun with a drastically reduced amount of solar cell, you can win on cost. An unfortunate side effect is that as your target gets smaller, you need to aim ever more precisely at the sun. This means that to be able to evaluate the performance of your concentrating system, you have to know how well you are pointed at the sun. This alone is a serious research project; there is substantial empirical evidence that building a sensor to track the sun takes lots of work, and that doesn’t even get you any actuation. You can buy a pretty good tracker, but you won’t know how good unless you have some sort of diagnostic instrument that can measure your error very precisely.

When I worked in the Stanford Robotics Lab after grad school, a shrewd man told me on one occasion, “Don’t make everything a research project.” (I think I was proposing writing my own TCP/IP stack or something similarly idiotic that would have taken long enough to preclude completion.) My hope is that the concentrating solar companies will not spend the engineering time it would take them to each build an SL1 equivalent.

And finally, did I mention that it also has a sweet command line interface?

(Perhaps I should note that the opinions listed above do not represent those of my employer. Especially not the unreasoning zeal for command line interfaces.)

Historically, I have spent a fair amount of time deriding Nanosolar for claiming that they would build a 430 MW/year solar cell factory by the end of 2007.

On the one hand, they have only 10 days to prove me wrong. I don’t think they will have ramped production up to 430 MW/year. On the other hand, they are shipping a thin film module created through a printing process. That alone is an impressive feat. They win the prize, soaring above the Aonian Mount, while pursuing things unattempted yet in prose or rhyme (well, maybe attempted in rhyme).

Nanosolar is claiming module costs of 1 $/W; the US solar industry is now selling around 5 $/W.

It looks like they have beaten:

• Ascent Solar (thin film, CIGS, probaby through vacuum deposition)
• Konarka (thin film, printed, organic cells)
• Heliovolt (thin film, printed, CIGS cells)
• SoloPower (thin film, CIGS, but electroplated, not printed)
• Miasole (thin film, CIGS, but not printed)
• Solyndra (thin-film CIGS, unknown process, but they’re hiring people with semiconductor process experience)

But have they hit grid parity? Maybe.

First off, $/W is a dumb metric. The W refers to the peak power, so if you buy a panel that peaks at 200 W for $800, you’re paying $4/W. It’s stupid, but it’s easy to measure, and it’s easy for journalists to quote.

A better metric is $/kWh, where kWh is a unit of energy. That’s harder to talk about, because you have to talk about average production over the course of a year, which changes with location, weather, age of the panel, and so on.

The sun that hits the ground peaks around 1000 W/m^2; you might get 20% of that on average, once you factor in night, clouds, and the like.

There are about 10,000 hours in a year, so I’d expect 200 W * 10,000 hours * 10% efficiency = 200 kWh/year for a square meter. In Massachusetts, where I live, that’s worth about $40 ($0.20 per kWh). (Did I get those calculations right?)

Conventional panels of around 10% efficiency are about $1500/m^2 (say, 2 Evergreen 200 W panels for $750 each?). Given panel life of about 20 years and the added expense of installation, an inverter, and maintenance, I think solar is still off from grid parity by a factor of 2-4 in Massachusetts (not counting Nanosolar).

If Nanosolar is telling the truth, they may have just hit grid parity.

Like a lot of semi-urban computer enthusiasts who plan on living for a few decades after the onset of global warming, I have a few computers that are always on, and I wish that I could find an economically viable way of reducing the emissions generated as a side effect of the power they require. Also, when the hard times come and grid power gets flaky or drops out entirely, it would make the local warlord happy if I could use a computer to calculate optimal irrigation ditch depths, or the like. (Note to self: learn to use abacus while leisure time still exists.)

Typically, solar arrays in urban or suburban areas are tied by an inverter to the local power grid. Such inverters cost a few thousand dollars; they both allow excess power to be released to other consumers and enable the use of AC appliances without any modifications. I live in a rented property, so installing a large solar array on the roof with an inverter in the basement is not an option. But, maybe I could run a smaller array without an inverter for DC loads only.

DC vs. AC
Computers, generally designed to connect to AC power, have as their first component a switching power supply that turns AC from the wall into DC. If I had a solar array, it would output DC, which would be converted to AC by the inverter, and then back to DC by each computer’s power supply, losing energy at each step. I call this “dumb”– why not just run the computers off of the DC directly?

The problem is that if you run the computers just off DC from the solar panel, the computers die when the sun is occluded by a cloud or a planet (at night, for example).

An alternative architecture
The system I’m building has a 24 V DC power supply fed from the grid at its core. This will run in parallel with whatever solar panel I eventually set up. For starters, I have replaced the ATX power supply that came with my desktop with a DC/DC converter from Ituner.com. I then power that from a beautiful DIN-mount Sola SDN 10-24-100P supply that I got off Ebay for $33.00 ($45.82 with shipping).

For the DC/DC converter, I looked at the pico-PSU, but rejected it in favor of the slightly larger M2-ATX-HV.

The M2-ATX-HV had a few advantages:

The M2-ATX-HV is a bit bigger, but my PC case is pretty large, so that wasn’t a concern. Including all the cables and shipping, I paid $96.40 for the M2-ATX-HV– about $30 for the advantages listed above.

Stage 1 complete
The DC system has been working reasonably well for a few weeks now. Next, I have to find a cheap way to test current sharing with a solar panel, as I don’t want to commit the full $700 or whatever for a 180 W panel until I have more evidence that it will work. I’m off to the beach to start collecting sand for a little homebrewed Czochralski action.