The Challenge for Green Energy: How To Store Excess Electricity

“Why are we ignoring things we know? We know that the sun doesn’t always shine and that the wind doesn’t always blow.” So wrote former U.S. Energy Secretary James Schlesinger and Robert L. Hirsch last spring in the Washington Post, suggesting that because these key renewables produce power only intermittently, “solar and wind will probably only provide a modest percentage of future U.S. power.”

Never mind that Schlesinger failed to disclose that he sits on the board of directors of Peabody Energy, the world’s largest private-sector coal company — a business with much to lose if a solar- and wind-powered future arrives. But at least he and his co-author got it partly right. The benefits from wind and solar are mostly intermittent — so far. But the pair somehow missed the fact that a furious search for practical, affordable electricity storage to beat that intermittence problem is well underway.

For decades, “grid parity” has been the Holy Grail for alternative energy. The rap from critics was that technologies like wind and solar could not compete, dollar-for-dollar, with conventional electricity sources, such as coal and nuclear, without large government tax breaks or direct subsidies. But suddenly, with rapid technological advances and growing economies of manufacturing scale, wind power is now nearly at grid parity — meaning it costs roughly the same to generate electricity from wind as it does from coal. And the days when solar power attains grid parity may be only a half-decade away.

So with grid parity now looming, finding ways to store millions of watts of excess electricity for times when the wind doesn’t blow and the sun doesn’t shine is the new Holy Grail. And there are signs that this goal — the day when large-scale energy storage becomes practical and cost-effective — might be within reach, as well. Some technologies that can store sizeable amounts of intermittent power are already deployed. Others, including at least a few with great promise, lie somewhere over the technological horizon.

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