Long-winded benefits.

The best wind-energy facilities can generate electricity at costs comparable to those of large coal- and nuclear-powered plants. However, compared with these old workhorse plants, wind-powered generators are less reliable because they depend on, well, the wind.

According to a team of energy analysts led by Patti Denholm of the National Renewable Energy Laboratory in Golden, Colo., wind systems' reliability could be boosted if they saved up excess energy during strong breezes. Such energy-storage systems could deliver full electric power about 80 percent of the time, which is comparable to the performance of conventional power plants, the researchers say. The challenge is how to store the energy economically.

One solution that's just about good to go: Save surplus wind energy as compressed air in an underground cave, then use it later to run an electric generator. Such a system would need an occasional boost of fossil fuel, but not enough to seriously undermine wind energy's environmental benefits, the scientists argue in an upcoming Environmental Science & Technology.

The researchers calculate that energy-storing wind systems could be far more efficient at generating electricity and would produce, per kilowatt of electricity generated, only a third of the nitrogen-oxide emissions and less than a fifth of the greenhouse-gas pollution emitted by even the cleanest coal plant.--J.R.