"This no-free-lunch rule applies to all energy alternatives. For example, while ethanol brewed from cost-effective crops can replace gasoline in the short-term, it still releases CO2. Solar and wind power are emission-free, but face their own downsides. One is power density. While a chunk of coal packs lots of energy into a small volume, wind and solar are rather dispersed. Thus, where a coal-fired power plant capable of powering a small city takes up only a few hundred acres, a wind-farm of the same capacity would require hundreds of square miles. Ditto for solar."
So says Paul Roberts towards the end of a clear-headed article about energy in today's Boston Globe (click the title of this post, which is the last heading of his piece).
A couple of points concerning the excerpt above. Corn or hemp or other plant-derived gasoline substitutes do indeed release CO2 when burned, but while the crops are growing they absorb CO2 and are therefore considered emission-neutral. And a wind-powered facility of the same capacity as the coal-fired plant in his example would in fact have to be almost 4 times as large as he says, to make up for the intermittency of its energy source, the wind. You would still need the coal-fired plant as well, operating very inefficiently, to compensate for the highly variable wind-plant output and respond to actual customer need (to which wind facilities are happily oblivious).
