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When it became clear that Solar One had its limitations, DOE funded a second facility, called the Solar Electric Generating System (SEGS), built by the Luz Corporation. U.S. News offers a nice description: “[S]ince the 1980s, a dazzling ‘parabolic trough’ display has provided reliable power to California, the only operating concentrating solar power project in the country.” The facility consists of 100 acres of 40-foot-high parabolic mirrors that focus the sun’s rays on a small black tube running along their focal point. The tube once again contains therminol, which again heats to 1500o C, again producing steam. The system is more efficient than the power tower, generating 354 MW.
The big problem is maintenance. The 10 million square feet of mirrors have to be washed every five days and scoured by high-pressure hoses once a month. The job is very labor-intensive. Luz went bankrupt in 1991 but the project was soon revived under the Public Utilities Regulatory Policies Act of 1978 (PURPA), which allowed states to require that utilities buy electricity from “alternate providers” no matter what the cost. California was an enthusiastic participant.
SEGS was soon plagued by fires. On January 10, 1990, a series of explosions rocked one of its cooling towers and ignited large quantities of therminol. Thirteen engine companies needed 1500 gallons of foam to quench the flames. (UPI, “Explosions Rock Solar Energy Plant,” January 10, 1990.) Then on February 27, 1999, almost a million gallons of therminol caught fire, destroying considerable portion of the facility. The flames released toxic fumes and a half-square-mile area had to be evacuated. The Federal Aviation Administration also set up a no-fly zone around the facility. (“Authorities Evacuate Area After Blast at Solar Plant,” The Associated Press, February 27, 1999.)
The good news is the system recovered and SEGS still operates under California’s new “renewable portfolio” law, which requires utilities to buy 10 percent of their electricity from renewable sources. The bad news is this one facility represents 90 percent of the world’s solar thermal electric capacity. At present there are no plans for its expansion.
Thus, we’ve already been around the block once with thermally generated solar electricity. The irony is that in the 1990s solar enthusiasts pretty much abandoned steam-generating solar power stations as too old-fashioned. Instead, they embraced photovoltaics, which offered “distributed power” that could be put on every rooftop.
Photovoltaics utilize Einstein’s “photoelectric effect” — the ability of a ray of light to knock loose an electron and start an electric current. Each wavelength of light interacts with different elements, however, and only a small portion of the sun’s energy — about 20 percent — can be converted. Silicon has been chosen as the material for photovoltaic “cells,” not because it is any better than other elements — it is worse than some — but because it is the cheapest as a raw material. Unfortunately, this has created the impression that solar cells will go through a miniaturization process, as computer chips have done. It can’t happen. Photovoltaic cells can only be made bigger and more ubiquitous to capture more solar energy.
Because there is no Moore’s Law for solar power, the price of photovoltaic cells has not experienced the drops that are supposed to come with mass production. As U.S. News puts it, “PV cost estimates span from an uncompetitive 23 to 43 cents per kilowatt-hour, while residential electricity prices in this country range from 5.8 to 16.7 cents.” PV cells may eventually find a niche in providing “peaking power” — the extra electricity needed by utilities on hot summer days when everybody turns on the air conditioning. But for base-load electricity, they will probably never work — particularly since the electricity disappears when the sun doesn’t shine.
It is because of the failure of photovoltaics to provide conventional electricity that enthusiasts have now turned back to the Power Tower.
SO WHAT ELSE IS PART of this “New Age of Energy?” U.S. News also offers up “deep geothermal,” heat energy drawn from deep within the earth.
Although not commonly recognized, the earth is a very hot place. Temperatures at the molten core of the earth reach 7,000 degrees C, hotter than the surface of the sun. In some regions, this molten magma comes close enough to the earth’s surface to heat groundwater. This produces geysers, geothermal vents (called “fumeroles”), and other forms of steam and superheated water jetting or leaking from the earth.
Since the 1980s, California, Hawaii and Iceland — all areas of frequent volcanic activity — have attached steam turbines to some of these vents to produce modest amounts of electricity. The largest geothermal plants produce 75 megawatts (about one-twelfth the size of a conventional plant). California now produces 2 percent of its electricity from geothermal and this represents 90 percent of America’s capacity and 25 percent of the world’s. There are only so many potential sites and often they are tourist attractions. So far no one has suggested attaching a power plant to Old Faithful.
Recently the idea has developed, however, that if we pump water deep into the earth — about three miles — it will heat to 300 degrees and can then be pumped to the surface again to produce steam. A recent MIT study suggested that the nation could provide all its electrical needs from this source.
The problem, once again, is cost. Even on paper, the MIT report already has the price at running as high as $1.00 per kwh — about ten times the price of conventional electricity. And that’s before anybody has even tried it. Once again, deep geothermal will be one of those far-fetched ideas that is always dangled as an alternative to doing something in the here and now.
So here’s a suggestion. Instead of pumping water three miles into the earth to heat it, why don’t we take the source of that heat and bring it to the surface?
That’s what we do when we build a nuclear plant. The main source of the earth’s heat is the radioactive breakdown of uranium and thorium atoms. A nuclear reactor simply brings this process to the surface and accelerates it under carefully controlled conditions. Drawing on this terrestrial heat isn’t that much different from burning the stored solar energy in coal — except that nuclear reactions produce 2 million times as much energy per ounce without any exhaust gases.
“Terrestrial energy” — it’s a “green” idea that didn’t make U.S. News’s “New Age of Energy.” Somehow it hasn’t yet made it into the environmentalists’ playbook, either. But if we’re going to solve any of our energy problems — supply, pollution, global warming — we’re going to have to give it a more serious look.
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