* I enjoyed Matt Bivens's April 15 "Fighting for America's Energy Independence," which is important in getting the vision and possibilities of renewable energy sources to the public. I have one small correction. Bivens says, "The Union of Concerned Scientists says 100 square miles in Nevada could produce enough solar electricity to power the nation." The actual land area is more like 10,000 square miles (a square 100 miles on a side) and the photovoltaic panels cover only half that land. My explanation of the calculation of that number is in the July 30, 1999, Science. Since then our energy use has grown, and the area is now almost 12,000 square miles (110 miles on a side)--still not a large area, when compared with the 45,000 square miles of land we've covered with paved roads.
It is interesting to note, given the Freedom car announcement, that if you wanted to supply hydrogen for 200 million fuel-cell vehicles (current US fleet), you would need an area of only 3,600 square miles. This is not necessarily the way we should do it, but it is important to note that we have the technologies in hand to utilize the solar resource, should we wish to exploit it.
John A. Turner
National Renewable Energy Laboratory
* Matt Bivens's implicit assumption that so-called renewable energies have negligible external costs in relation to nuclear power is an often repeated canard. According to an exhaustive study by the European Union, the externalities of nuclear power are comparable to those of wind- or solar-generated electricity. The study calculates external costs on a euros-per-megawatt-hour basis for several means of generating electricity and finds that the basic premise of Bivens's article cannot be supported in Europe. Naturally, nuclear power also has the tremendous advantage of not being beholden to the weather and being able to provide a reliable base load, night and day, 24/7, 365 days a year. Many US nuclear power plants routinely operate continuously for more than a year without a glitch (see www.externe.info).
Simply put, to produce relatively small, unreliable amounts of electricity, renewable energies must consume large amounts of materials (some toxic, like selenium or cadmium for solar panels), land, natural resources and person-power. Nuclear power produces abundant power from small amounts of material, at small external costs, even when one accounts for the vanishingly small probability of accidents and the cost of waste disposal.
* Matt Bivens does not mention battery-powered vehicles, which have zero pollution and are now available as fleet vehicles (e.g., buses, trucks, rental cars). One company, Electric Fuel Corp. (www.electric-fuel.com), has demonstrated an electric bus using zinc/air batteries, which will power a loaded, air-conditioned bus over a full day's bus route.
While the battery-powered (electric) bus is now available, a vehicle will not be powered by a hydrogen fuel cell in the near future. The current hydrogen fuel cell is many times the cost of an internal-combustion engine, and it is likely that the hydrogen fuel will be generated on board the vehicle from an oil derivative (e.g., methane), which will emit the greenhouse gas carbon dioxide. It is high time that someone recognized the high cost and limited usefulness of the hydrogen fuel cell and the availability (today) of a zero-emission (all-electric) fleet vehicle (see the MIT January/February Technology Review). Bill King
* Matt Bivens leaves out the single most effective method of reducing dependence on fossil fuels: increased taxes on all types of fossil fuels (with tax rebates/credits for low-income households). History shows that the only truly effective way to reduce consumption of any good is to raise its price. …