State looks for ways to store electricity

10/22/2013 8:23 PM

10/22/2013 8:24 PM

The state has set a goal for storing electricity, which could mean better use of wind, solar and other intermittent sources of power.

The California Public Utilities Commission voted 5-0 last week to set the target for Pacific Gas and Electric Co., Southern California Edison and San Diego Gas & Electric.

They could use various technologies – such as rechargeable batteries, compressed air or flywheels – to store electricity in times of surplus and use it during high demand.

The decision does not affect the Modesto or Turlock irrigation districts, but they, too, have looked at ways to store power, such as a battery technology that a Bay Area company is testing for MID.

The districts also have looked into pumped storage, which would use cheap nighttime power to pump water from Don Pedro Reservoir into a new, much smaller reservoir at a higher elevation. The water would be released each day through a powerhouse, then the cycle would repeat.

The system would have a high cost, estimated at $1.7 billion in 2010.

“Up to this point, the project has not been feasible,” TID spokesman Herb Smart said this week. “Should the timing be right to push forward with the project in the future, the district remains ready to do so.”

Last week’s commission vote directed the three large utilities to have 1,325 megawatts of storage capacity by 2024, a sixfold increase from the current level.

“Storage is a game-changer that can help people manage their energy use and expand the capacity of renewable resources to provide power to homes and businesses,” Commissioner Catherine J.K. Sandoval said in a news release.

Most electricity will continue to be used as it is generated at nuclear, hydro, fossil fuel and other plants. The storage systems could reduce the need for new plants and transmission lines and could be especially useful for energy from wind, which often does not blow at times of high demand.

Primus Power Corp. of Alameda is testing a possible battery system that would store some of MID’s substantial wind power, mainly from Oregon and Washington.

PG&E is looking at a possible system near Lodi that would use wind or other intermittent power to compress air into underground natural gas reservoirs that are depleted. The air would be released to generate power during high demand.

Other projects around the state would use off-peak power to make ice, which then would be used to cool commercial buildings, reducing their demand for costlier electricity during the day.

And then there are large flywheels, which spin with the help of surplus power, then generate their own electricity as a brake is applied.

San Luis Reservoir, which holds water in the hills west of Los Banos for state and federal systems, is a pumped storage system. Electricity from elsewhere is used to the lift water into the lake, and the water then flows through a powerhouse before heading to farms and other users. The energy gained from the dropping water falls short of the energy needed to pump it into San Luis.

The U.S. Department of Energy has a directory of energy storage projects at www.energystorageexchange.org.

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