PG&E Eyes 2nd Pumped Storage Plant

By Published On: August 27, 2010

Pacific Gas & Electric is requesting $33.47 million to research developing a new pumped storage facility. The utility estimates that the project would cost $2.5 billion to build. Based on the state’s requirement for renewable power--which is largely predicated on intermittent bursts of electricity flowing into the transmission grid--PG&E applied to the California Public Utilities Commission August 20 for permission to spend ratepayer funds on the feasibility study. “Bringing renewable resources’ unpredictable generation output on-line in any substantial way will require a corresponding expansion of the energy storage capability of the California transmission system,” noted PG&E. The utility estimates that the capacity benefits could reach $2.1 billion. Other benefits, like reserve services for the grid, could be as much as $7 billion, PG&E concluded. A pumped storage plant could use intermittent renewable energy to push water from a lower reservoir to a higher reservoir whenever that energy is available. The water in the upper reservoir then would be released to make hydroelectricity whenever required for customer use. Historically, pumped storage uses more energy to pump water to a higher plane than is captured out of the released hydropower. While it still takes more energy to move the water uphill than it produces running down, renewables proponents note that using wind and solar electricity doesn’t waste fossil fuel to run pumped storage facilities. Instead, it uses excess renewable energy produced that could not otherwise be consumed. The facility is aimed to reside on the Mokelumne River and could be scaled to provide 1,200 MW of capacity, according to PG&E. The utility added it could use the existing Bear Creek Reservoir or build a new one on Cole Creek. Water from the Mokelumne River is sent to the East Bay Municipal Utility District for urban consumers of potable water. The river flow is fragile enough that the muni called on consumers to cut back water use 15 percent in 2008 due to low flows. This year, so far, flows are up. The California Independent System Operator recognizes that pumped storage may be helpful in the near term for parlaying solar and wind energy into the grid upon demand. The grid operator only looks at what storage may do to support the transmission system, not at the potential economic or environmental effects, according to a spokesperson. The Federal Energy Regulatory Commission, which oversees hydroelectric facilities, is likely also to influence any pumped storage plan. While embracing the concept, the grid operator was less-than-enthusiastic about a similar project proposed by Nevada Hydro at Lake Elsinore. That 500 MW project died on the vine last year. Developers wanted it to be considered a transmission facility so it could get a part of charges collected for the transmission system. The grid operator maintained it was a generation facility and, as such, would have to be the developer’s investment risk. PG&E has one other pumped storage facility. The utility’s Helms Pumped Storage facility became operational in 1984, at a cost of $967 million. Due to cost overruns, the commission disallowed $22 million of that total. Ten workers died building the facility--seven fell to their deaths when a scaffold collapsed in 1981. The pumps in that plant use about 25 percent of the power to move water between reservoirs, resulting in a loss of about one-fourth of total energy. While Helms was not designed to be used for storing renewable energy, the facility is used to fill supply voids. While research on a new pumped storage facility is pending, PG&E was granted $25 million in November 2009 by the Department of Energy for other storage project research. Those developments include advanced batteries, flywheels, and compressed air. The utility has plans for a $356 million compressed air storage facility in Kern County. This project would pump air using night wind power into porous underground rock, according to PG&E. With the potential of 300 MW of capacity, the compressed air project awaits CPUC approval.

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