Coal, Gas

Compressed Air Energy Storage Development Gets Funding

Issue 6 and Volume 106.

Compressed air energy storage (CAES) offers bulk power storage to the electric industry by charging large underground formations with compressed air. During peak electricity demand or price periods, the compressed air is discharged through the gas turbine, along with some fuel, such as natural gas, to drive an electric generator. Compared to peaking gas turbines, CAES can provide 80 percent efficiency in power production mode, 60 percent lower emissions, two to three times faster ramp rates, better part-load heat rates, and ability to maintain capacity and heat rate during high ambient temperatures.

Ridge Energy Storage and Grid Services, L.P. has announced an agreement with El Paso Corporation subsidiary EP Energy Finance for $15 million of capital to develop compressed air energy storage projects.

Illustration courtesy of Ridge Energy Storage.
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Ridge Energy Storage and Grid Services, L.P. was formed to bring the CAES option to the commercial electricity marketplace.

A traditional simple-cycle combustion turbine requires 10-12 MMBtu to produce 1 MW, while a combined-cycle combustion turbine requires 6.5-8.5 MMBtu. CAES requires only 4-5 MMBtu. The primary difference in the respective thermal efficiencies, or heat rates, results from the functional separation of the compression process from the turbine operation in the CAES configuration. In a conventional simple-cycle configuration, the compressor is physically connected to the turbine shaft.

Because the compression process consumes approximately two-thirds of the turbine’s output, only one-third of the output is available to generate electricity. A CAES turbine does not run a compressor simultaneously, allowing all of the energy produced by the turbine to generate electricity. Therefore, a CAES plant can generate about three times as much electricity as the same size turbine in a simple-cycle configuration.