General Compression aims to double wind farm profits

"Customers don't want power when the wind blows. They want it when they want it."

So noted the CEO of a new startup that thinks it's found a way to make wind power "dispatchable"—utility jargon for being available on-demand—using turbines to compress air and store it underground.

Boston-based General Compression today announced an initial round of funding of $5m to help accelerate development of its wind energy capture technology, meant to address the major criticism of wind power: that it's rarely available when it's really needed.

The company's system is to have three components: special proprietary compressed air wind turbines, a pipeline network that collects and stores compressed air and a power plant of expanders and generators.

General Compression intends to put its compressors in conventional-type wind turbines, high in the air.

"If you're going to compress air, you've got two choices: either make electricity in the turbine and put the compressors in the ground, or put compressors in the turbine and pump the air into the ground," said General Compression CEO David Marcus today to the Cleantech Group.

"We've found it's much cheaper and efficient to put compressors in the turbine."

When the wind blows, General Compression compressors inside turbines are to pump air to over 100 atmospheres of pressure and send the air down the towers into an underground network of high-pressure pipes.

The pipeline network is to collect and store 6-12 hours of energy. If the project is sited near a geologic feature such as a salt dome, aquifer, limestone cavern, or depleted gas field, the company projects energy storage times of weeks, or even months.

"There have been some small experimental turbines putting compressors or hydraulic motors or direct drive shafts that powered water pumps underground. But those have been small scale irrigation pumps, old fashioned windmills. There's been very little work on utility-scale wind turbines that have been non-electric," said Marcus.

If it works as planned, the project could shift the time when power is sold, allowing wind projects to sell power on peak at a higher price, be more compatible with the needs of the grid and become eligible for capacity payments.

"The industry has done a good job of lowering the cost of extracting energy from wind, but it gets a terrible price for the power it sells," noted Marcus.

General Compression is a year-old startup. It's currently working on a 50 KW compressor prototype, which it now intends to scale up into a 500 KW compressor. The company plans to put four of them in each turbine, for 1.5-to-2 MW utility-grade output.

"By enabling wind farms to store and sell power at peak hours, General Compression will dramatically improve the profitability and market potential of wind power," said Don Hodel, Chairman of wind developer Summit Power.

Hodel, who was former U.S. Secretary of Energy under Ronald Regan, is a founding shareholder of General Compression. His company has committed to participating in development projects with the company.

CEO Marcus told the Cleantech Group the company was 18 months away from erecting a prototype, and was considering four different sites.

The company's first round was "half institutional investors and half angel investors," he said, choosing not to identify them.

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