FROM READERS.

Is Our Outlook For Solar Energy Too Sanguine?

Although this letter is several months late, I would like to raise important questions about Chris Flavin's short essay, "Energy for a New Century," in the Earth Day 2000 issue. The essay (and, in fact, the whole issue) seems to be naively sanguine about the prospects that renewable energy can be generated, concentrated, transported, and used in sufficient quantities to drive the modern industrial economy. By contrast, I hold the prospects to be dim that renewable energy sources can support the present profligate, urban-suburban way of life of the wealthy, industrial nations. I also doubt that sufficient quantities of renewable energy can be made available to lift the 3 or 4 billion people of the developing world out of poverty even before their number doubles during the 21st century.

Few question the fact that the Earth's supply of petroleum is limited. Pessimists predict the shortages will begin to steadily reduce the amount of petroleum available on the world markets sometime between 2003 and 2010. The most sanguine optimists only postpone the shortage until 2050. In any historic time frame, the end of the petroleum age is drawing near. And unless there is some unexpected breakthrough in the discovery of new sources of energy, human beings will have to learn to live with the energy that the sun provides.

Flavin states, "During the 1990s, wind power has grown at a rate of 26 percent per year, while solar energy has grown at 17 percent per year. During the same period, the world's dominant energy source-oil--has grown at just 1.4 percent per year." In view of the fact that the present economic system runs on cheap energy from fossil fuels, however, his statement ignores the question of the efficiency of solar technology. That is, he just assumes that renewable sources can supply a net surplus of concentrated and transportable energy for human use.

The case for switching the present economy from running on fossil fuels to running on renewable electricity cannot be made on the ground of the vastness of solar energy resources. It may well be that the overall efficiency of transforming, storing, transporting, and using the world's "vast supply of wind, biomass and other forms of solar energy" is less than 1. That is, the renewable energy gained may be less than the energy used to produce it. If so, renewable energy cannot replace fossil fuels regardless of the fact that solar energy is "6000 times as abundant on an annual basis as the fuels we now use."

To be specific, in a world that runs on renewable resources, energy costs cannot be subsidized by burning coal, petroleum, or natural gas. In such a world, renewable energy must be net energy--the total energy gained minus all energy costs. Here are some of the energy costs that will have to be covered by those vast wind farms and arrays of photovoltaic panels: the energy...