California's Power Storage Mandate is Vaguely Written, But That Might be a Good Thing

As of last week, California utilities have an official target for how much power storage they must add to the grid -- sort of. While the October 17 ruling by the California Public Utilities Commission requires the state's largest utilities to develop more than 1,300 megawatts of electrical power storage by 2020, the commission didn't specify an actual capacity for that storage, which has led some tech-savvy members of the public to raise an eyebrow.

An environmental attorney and renewable energy wonk who was deeply involved in years of negotiations leading to last week's ruling has assured ReWire that that's not a huge problem.

ReWire reported last week that California's new 1.3 gigawatt power storage target, formalized on October 17 by a unanimous vote of the commissioners, seemed not to specify a target for how much electrical power that storage will actually store. Earthjustice attorney Will Rostov, who represented the Sierra Club in the CPUC storage proceedings, confirmed to ReWire that the ruling is silent on how many megawatt-hours' worth of storage utilities must develop.

"And I think that's okay," said Rostov.

The issue, as we mentioned last week, is that watts, kilowatts, and megawatts are instantaneous measures of power, but we don't use power instantaneously: we use it for a period of time. It may take 40 watts constantly flowing through a light bulb to keep it lit, but if you need that bulb lit for an hour from stored electrical power, you need to know the storage system can deliver 40 watt-hours of electrical power.

In simpler terms, mandating that the state's utilities develop 1,325 megawatts of power storage without specifying a number of megawatt-hours is a little bit like ordering a water storage tank without specifying how many gallons it can hold.

But Rostov doesn't see that lack of specificity as a major issue. "You're right: the CPUC doesn't say whether the storage should cover eight hours or eight minutes. And I think that's okay. The point of the CPUC ruling is to help develop storage technology. It's a new industry. As utilities invest in storage to comply with the ruling and the technology develops, we'll learn more about what kind of capacity is possible with different technologies. This ruling will push things along."

As evidence that the ruling is more about developing new technologies, it's worth noting that pumped storage -- a tried and true technology capable of significant power storage -- doesn't count toward the CPUC's targets. [Update: I read this section of the ruling wrong, as pointed out by a commenter below. Pumped storage projects of up to 50 megawatts do qualify. I regret the error. - CC ]

And even short-term storage capacity has its benefits, Rostov points out, for things like load balancing, regulating grid voltage, and avoiding outages.

Rostov has worked on quite a few energy-oriented issues as an Earthjustice attorney, including working to protect Californians from emissions from natural gas-fired power plants, and taking part in a landmark suit to prevent the Chevron refinery in Richmond, California from expanding so that it could refine dirtier oil. (In the interest of full disclosure, I worked with Rostov on the Chevron lawsuit as a press consultant.)

Rostov's client, the Sierra Club, had been pushing the CPUC to adopt meaningful storage targets as required by a state law passed in 2010, Assembly Bill 2514, the first state law that solely focuses on incorporating energy storage into the electrical grid. The ruling, shepherded through the CPUC by Commissioner Carla Peterman, passed unanimously. The ruling won acclaim from renewable energy advocates, who see storage as a way around building new gas-fired power plants to take up the slack when wind and solar power slacken.

"Clean, renewable energy sources will shape our future, whether the dirty antiquated fossil fuels industry likes it or not," said Rostov, "so it's excellent to see California getting there first. It took years of work by environmental advocates and state regulators to reach this point."