Compressed Air Energy Storage (CAES)

NPPD takes pride in using a variety of fuels to generate electricity, including coal, uranium, water, wind, natural gas, and solar. But what about compressed air? Could that be an energy source of the future? NPPD believes it could.

NPPD has an agreement with KEBRH Operating, LLC, owner and operator of the Big Springs Gas Storage Unit in Deuel County, Neb. west of Ogallala, to test what could be a future, compressed air energy storage facility, if the location proves suitable for such an operation.

NPPD is in the process of developing an air injection, test plan to determine the viability of using the Dakota sandstone formation as a compressed air energy storage facility and energy resource. The plan will determine testing costs, what type of equipment should be used to conduct the test and inject the air, how long will it stay compressed and the rate at which it can be compressed and withdrawn. Information obtained from the air injection test would be used to design a future compressed air energy storage facility, if the project is determined to be beneficial for NPPD and its customers.

The natural gas storage reservoir was identified by NPPD as a geological formation that could handle sufficient pressure, support the injection of air, and produce good air withdrawal rates. The air would then be used to generate electricity when needed at a later time. The process works as follows: electricity from off- peak periods would operate compressors that pump compressed air into the geological formation through injection wells and store it until needed. The air is then withdrawn to serve as the fuel source for powering an air turbine to generate electricity.

NPPD wants to conduct the air test to determine the maximum quantity and pressure of stored air the unit can hold. Neither the size of the compressed air energy storage facility nor the amount of electric production can be determined until this test is complete, but NPPD is hopeful the facility could represent more than 100 megawatts of capacity.

There are currently two, primary, grid-scale technologies used to store energy a) pumped hydro storage and b) compressed air energy storage. NPPD has studied pumped hydro storage, but it is far more expensive compared to the estimated $1,200 – $1,300 per kilowatt in capital costs to construct a compressed air energy facility. In addition, the scale and flexibility of such a resource fits better with NPPD’s system.

Why we are involved

“Pursuing this project reflects NPPD’s commitment to studying new energy technologies,” said NPPD President and CEO Pat Pope. “If commercially viable, the facility could benefit NPPD’s in-state ratepayers as an additional generation resource and be one of three, commercial-scale CAES facilities in operation worldwide, joining one in Germany and a second in Macintosh, Ala.”

NPPD is also participating in the Electric Power Research Institute Compressed Air Energy Storage Pilot Project. The project is currently being funded by NPPD’s Domestic Energy Research and Application Initiative.