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Green-Energy Storage: 'The Next Big Thing'

For California to reach its ambitious climate-change goals, it must figure out how to deliver electricity when the sun isn't shining and the wind isn't blowing.



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"The number-one benefit of energy storage that is urgent enough to already be investing in it is to smooth solar energy," Krevat said, referring to weather-induced dips and surges in solar energy output, a persistent issue in coastal San Diego. "We have data that we've measured on specific circuits where there's a high concentration of solar energy, and it causes voltage swings, especially when we have the marine layer burning off. It changes from second to second. Our old equipment is electromechanical, so it just can't react fast enough. By the time it reacts, the clouds have moved to a different area."

Most new battery technologies, however, can respond in a fraction of a second, smoothing the power supply in real time and avoiding solar's potentially harmful hiccups — including the backwards flow of energy on local circuits that can result when sunshine is high and demand is low. "We think storage is a very important piece of California's energy future, and really the world's energy future," Krevat said.

However, not all of California's major utilities are so enthusiastic — especially about the possibility of the CPUC handing down another mandate. But storage, whether paired with large-scale solar and wind plants, installed in local circuits, or even set behind the meter at private homes and businesses, can be a boon to utilities by increasing the reliability and quality of the energy supply and reducing the likelihood of outages. It also allows utilities to profit by storing energy when it's cheap (like overnight) and selling it at peak times: a classic case of buying low and selling high.

This is something that San Diego Gas & Electric, and, to a lesser extent, Pacific Gas & Electric, have begun to embrace. PG&E announced in May the completion of a four-megawatt, six-hour battery pilot project in San Jose designed to help study how sodium-sulfur batteries in particular can benefit the grid. And the utility has received $25 million from the Department of Energy and $1 million from the California Energy Commission to demonstrate a compressed-air storage plant, where excess wind energy will be used to compress air in a depleted natural gas reservoir. The air can later be drawn upon during high-demand periods to produce electricity by releasing it through a turbine. PG&E is still searching for a suitable site. When completed, the facility will be the third of its kind in the world, and the first in the Western US.

One goal of the project is to assess the cost-effectiveness of compressed-air storage on today's grid. It's a critical point, as both Skinner and Peterman designed their proposals to that ensure that storage is only required to the extent that it is, over time, no more costly (and ideally less so) than using other options, including natural gas plants, to stabilize the grid. "What we're trying to achieve here is encourage storage that has a cost, but not a cost that would exceed" the cost of generating electricity, Skinner said.

California can technically meet its ambitious 2020 RPS goals without adding much more storage than currently exists on the grid, said Cal's Dan Kammen. But if we look beyond 2020 into 2030, he said, when the renewable-energy target could be elevated to 50 percent or more, and eventually 2050, when he projects that natural gas could be phased out entirely, storage becomes much more critical.

"If we don't begin by getting storage deployed now, then in that 2020 to 2030 timeframe, we won't be ready," he said. "It's clear from the models that if we can begin to deploy these advanced technologies sooner, we can gain more information about them and bring down the price."

Yet California isn't the only state with big plans for energy storage. Kansas and Texas, both of which have high concentrations of wind energy, are actively considering storage at both policy and technology demonstration levels, said Brad Roberts, executive director of the Electricity Storage Association.

In addition, a ruling from the Federal Energy Regulatory Commission in October 2011 has spurred large storage projects in the Eastern United States by offering financial incentives to grid operators for using storage — instead of coal and gas plants — to regulate voltage frequencies.

Imre Gyuk, who heads the DOE's energy storage program — and who will be another keynote speaker at the San Jose conference this week — believes 2013 represents a turning point in the energy storage field worldwide. California, and the nation at large, are out front — for now.

"Storage is a reality," Gyuk said. "It's growing in the United States. It's growing in China like crazy. The entire Pacific Rim is just bursting to get into this. Europe is taking it up.

"But they're all behind us. We need to take some leadership in this," he cautioned, citing California's proposed mandate as a model. "We don't want to let happen what happened with photovoltaic panels."

Correction: The original version of this story misstated Brad Roberts' first name and the name of the organization in which he is the executive director. It is the Electricity Storage Association, not the Energy Storage Association.

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