One problem perhaps more than any other has proven a drag on the long-term prospects for wind power: How do you turn on the lights when the wind isn't blowing?

A New Jersey company said last week that it has joined with Michael Nakhamkin, one of the top thinkers in energy storage, to develop ways to trap wind-generated power in underground reservoirs.

Nakhamkin has helped develop technology to pull excess energy off the power grid - usually at night when usage has waned - to run compressors that pump air into sealed, underground caverns that once held oil, salt or natural gas.

During periods of higher demand, the air is released and heated to run air expansion turbines. The heating process uses about 100 megawatts of power from natural gas and 200 megawatts of power from the compressed air.

The announcement comes just as a drilling boom for natural gas heats up nationwide. Natural gas has supporters in both the private sector and in Washington because it releases fewer of the greenhouse gases that can lead to global warming and because it has been found domestically in massive quantities.

While the still involves fossil fuels, Nakhamkin said emissions, compared with traditional turbine systems, are far lower.

"This technology significantly reduces fuel oil and natural gas consumption," he said.

In urban areas where underground storage isn't feasible, or where bedrock makes drilling expensive, ground-level pipes can be used to store the air, though capacity is diminished.

"We really think this is a game-changer for the renewables industry," said Roy Daniel, chief executive of Energy Storage and Power LLC, a joint venture between PSEG Energy Holdings and Nakhamkin.

PSEG Energy Holdings is investing about $20 million in the project plans to market and license the technology.

"We're pretty bullish on the market right now," Daniel said.

Compressed air in a cave about one-third the size of the New York Giants' football stadium - roughly 21.5 million cubic feet - would be enough to power a 300-megawatt turbine for eight hours, Daniel said.

That load could power about 200,000 homes - a small city - for about eight hours, said John Stratton, an electrical power systems professor at the Rochester Institute of Technology.

"That's a healthy load," he said. "It's going to get us through the peak of the day by using excess energy at night."

While the process isn't totally efficient - energy is lost while being transferred - it "makes wind a very different kind of energy than it is today," Stratton said.