Fickle winds, clouded sun pose problems for renewable energy

Robert S. Boyd | McClatchy Newspapers

last updated: July 11, 2007 08:24:37 AM

WASHINGTON — Scientists and engineers are struggling to find ways around a major obstacle to the growth of renewable energy: the fact that inexhaustible sources of energy, such as the sun and the wind, are undependable.

Solar power doesn't work at night or on cloudy days. Wind is notoriously fickle, often dying down in the late afternoon just as electricity demand is peaking.

This on-and-off variability is a serious problem, since many people who worry about global warming hope that clean, nonpolluting renewables will reduce the demand for fossil fuels such as coal and oil. More than 20 states have passed laws requiring utilities to generate 15 to 20 percent or more of their electricity from nonfossil fuel sources in the next decade or two. Congress is considering similar proposals.