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By: Matthew L. Wald | The New York Times: Energy & Environment | July 27, 2010

The rapid growth of wind farms, whose output is hard to schedule reliably or even predict, has the nation’s electricity providers scrambling to develop energy storage to ensure stability and improve profits.

As the wind installations multiply, companies have found themselves dumping energy late at night, adjusting the blades so they do not catch the wind, because there is no demand for the power. And grid operators, accustomed to meeting demand by adjusting supplies, are now struggling to maintain stability as supplies fluctuate.

On the cutting edge of a potential solution is Hawaii, where state officials want 70 percent of energy needs to be met by renewable sources like the wind, sun or biomass by 2030. A major problem is that it is impossible for generators on the islands to export surpluses to neighboring companies or to import power when the wind towers are becalmed.

On Maui, for example, wind generating capacity over all will soon be equal to one-fourth of the island’s peak demand. But peak wind and peak demand times do not coincide, raising questions about how Hawaii can reach its 70 percent goal. For now, the best option seems to be storage batteries.

In New York and California, companies are exploring electrical storage that is big enough to allow for “arbitrage,” or buying power at a low price, such as in the middle of the night, and selling it hours later at a higher price. In the Midwest, a utility is demonstrating storage technology that can go from charge to discharge and back several times a minute, or even within a second, bracing the grid against the vicissitudes of wind and sun and transmission failure. And in Texas, companies are looking at ways of stabilizing voltage through battery storage in places served by just one transmission line.

Renewable goals can be met, many in the industry insist. But if the energy source is intermittent, “you can’t do that without batteries of some sort,” said Peter Rosegg, a spokesman for the Hawaiian Electric Company.

His company has agreed to buy electricity from a wind farm on the northern shore of Oahu, where the Boston-based power company First Wind has just broken ground.

The spot is one of Hawaii’s best wind sites, Mr. Rosegg said, but the supply is gusty and erratic. What is more, it is at the farthest point on the island from the company’s main load center, Honolulu, and does not even lie on its high-voltage transmission backbone… (article continues on