Renewable energy has manyadvantages, as environmentalists won't hesitate to tell you. There's no need topay for fuel since the wind and the sun are free, and that saves utilities fromthe price spikes seen in coal, natural gas, oil and nuclear. But wind and solarface one major problem: intermittency. When the wind doesn't blow and the sundoesn't shine, turbines and silicon panels aren't producing electricity, andthere's no way to store the electricity they do produce during peak times ifit's not being used. That's a serious obstacles since utilities, often by law,need to provide enough electricity to meet demand at all times.
But utility-scale solarcompanies are working on ways to store the energy they produce during thebrightest days. One option: molten salt. It can be used in solar thermal, whichemploys powerful mirrors to focus the sun's heat to create steam, driving anelectric turbine. The surplus heat produced during the day can be used to warmup massive amounts of salt, which can absorb significant amounts of heat. Whenthe sun goes down — or when it's simply cloudy — that heat can be used togenerate steam and run an electric turbine. It's not perfect, but it's the bestbattery that's been developed yet for utility-scale solar.