There's something about solar energy that turns otherwise intelligent brains to mush. Paul Krugman, the celebrated Nobel Prize-winning economist, has now joined the crowd.
In an op-ed last week entitled "Here Comes the Sun," Krugman invoked Moore's Law, of Silicon Valley fame, to marshal the case that solar energy will soon be taking the place of coal, oil, gas nuclear and all those other nasty things. Here's the way he went about it:
For decades the story of technology has been dominated, in the popular mind and to a large extent in reality, by computing and the things you can do with it. Moore's Law -- in which the price of computing power falls roughly 50 percent every 18 months -- has powered an ever-expanding range of applications, from faxes to Facebook.
Our mastery of the material world… has advanced much more slowly.… But that may be about to change. We are, or at least we should be, on the cusp of an energy transformation, driven by the rapidly falling cost of solar power.… [A]s a blog post at Scientific American put it, "there's now frequent talk of a 'Moore's law' in solar energy," with prices adjusted for inflation falling around 7 percent a year.
Well, serves you right for relying on Scientific American. As anyone who has read that once venerable magazine of late can tell you, it's much more about politics than science.
In the first place, Moore's Law has nothing to do with price. It's about information. Literally, it describes the number of components that can be placed in an integrated circuit. Moore noted in a 1965 paper that the figure had doubled every two years from 1958 to 1965 and thought it would probably continue at that pace "for at least ten years." In fact it's continued that way ever since and has now accelerated to once every 18 months.
Moore's Law is not a Law of Nature, like the Laws of Gravity. It is only an empirical observation about our rate of innovation. We may eventually run out of room at the bottom. Moore himself predicted in 2005 that in twenty years we would reach the dimensions of individual atoms and progress might end -- unless we started working at the subatomic level. Other commentators have pushed the limits even much further out.
So what does all this have to do with solar energy? Well, nothing. "It is a common (but mistaken) belief," says the Wikipedia page, "that Moore's Law makes predictions regarding all forms of technology, when it has only actually been demonstrated clearly for semiconductor circuits."
Not that people haven't tried. Al Gore started the whole thing in The Earth in Balance when he referred to solar collectors as "small flat panels of silicon or similar materials that are designed to produce currents of electricity [emphasis added]." Somehow he got the idea that because computer chips and solar panels were both made from silicon, they would follow a similar trajectory. Even Silicon Valley entrepreneurs and venture capitalists seem to have gotten the bug around 2004 when they jumped into "alternate" technologies, proclaiming they would do for energy what they had done for computing.
Moore's Law is about information, not energy. The reason computer chips have gotten smaller and smaller is that we keep using less and less energy to store the same amount of information. Think of each logic gate as a light bulb that can be turned on and off to represent a "1" or a "0." The original computers used vacuum tubes that consumed lots of electricity. Now we use transistors printed on microscopic circuit boards that require only the faintest electrical current. We may eventually get down to the level of individual electrons, but the point is that all this is accomplished by using smaller and smaller energy differentials to represent the ones and zeroes.
When you go looking for energy, however, you can't do that. You can't go down, down, down into the microcosm using less and less energy to produce more and more energy or even the same amount of energy. Energy is energy. You're stuck with what's available.
With solar energy this is all very easy to calculate. The average amount of solar energy falling on a square meter of earth is 400 watts. It will never be any different. With present technology, we can convert 25 percent of this to electricity. This means powering a 100-watt light bulb on a space the size a card table. If we could raise this conversion to 35 percent -- a 40 percent increase -- it would be a technological marvel. That's a lot different than doubling every two years.
What that means is that the only practical way to produce more solar energy is to build bigger and bigger projects. It now takes a facility of about 20 square miles to produce 1000 megawatts -- the same output as a large coal or nuclear plant. The Department of Interior is talking about covering 400 square miles of Western desert with solar collectors to produce the output of about ten reactors. We'll see what the environmentalists have to say about that. All this works in America because we have lots of empty space, but it is not likely to work in densely populated areas.
There is always the possibility of rooftops. This has potential, particularly since solar peaks at the right time, on hot summer days when air conditioning strains the grid. Solar could be very useful in helping utilities meet the perennial problem of supplying peak demand. But all this is not going to be cheap. However prices may be dropping, they are not going to follow any exponential path. Solar electricity is now three times as expensive as nuclear and five times the price of gas. Even if it becomes competitive, it is only available one-quarter of the time. It won't be replacing nuclear, gas, or coal any time soon.
After I wrote my book, Terrestrial Energy, in 2008, I started giving a Power Point speech in which I pointed out the staggering land requirements of so-called "renewable" energy. I used a 2005 quote from Oliver Morton, news editor of Nature, who had proclaimed, "If scientists can discover a Moore's Law of solar energy, it could change the world." Lately, however, I have been leaving it out because it seemed too outmoded. It wasn't fair to be holding Morton responsible for this early naïveté.
Thank goodness for Paul Krugman. Now I don't have to rely on Oliver Morton anymore.
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