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California grids face RE 'oversupply'

An oversupply of renewable power is the biggest challenge facing California’s future grids, claims the head of the state’s independent system operator.

“Over generation is probably the biggest issue that we’re going to have,” says Stephen Berberich, chief executive of California ISO (CAISO), which operates the state’s grids.

“One of the things I don’t want to do is be in the position where we have to throw away all this renewable power we’re going to have. That just doesn’t make any sense, for lots of reasons.”

Unlike other renewables-friendly places like Germany, where capacity markets are being considered to compensate for surges in variable wind and solar power, California has long had a “resource adequacy requirement” in place – mandating that utilities have always procured at least 115% of their peak load.

California’s array of power plants “is turning over right now in such a way that it will be fairly compatible with the renewables fleet” in the future, Berberich claims. But he notes that the state still has power stations that take two days to ramp up.

“A base load fleet does not marry well with renewables,” he says. “You just exacerbate oversupply.”

Under its Renewable Portfolio Standard, which mandates that 33% of the state’s electricity come from renewables in 2020, California added 6.24GW of renewables capacity between 2003-2013.

By the end of 2013, California had 5.8GW of wind capacity in place, second in the nation after Texas, and 2.7GW of solar, making it the national solar leader by magnitudes of scale.

Yet significantly more renewables capacity is due to come on stream over the next few years.

Last year, the state’s three large investor-owned utilities – Pacific Gas & Edison, San Diego Gas & Electric, and Southern California Edison – collectively served 22.7% of their retail electricity sales from renewables.

The solution for California, according to Berberich, is a new generation of rapid-start gas plants alongside vastly more storage to accommodate renewables.

CAISO is among the world’s largest ISOs, delivering some 300 million MWh of electricity each year.

“What do you do with [extra renewable power]? You can curtail it or you can use it,” Berberich said, speaking recently in San Francisco.

“To get people to consume electricity in the middle of the day is heresy in the energy industry – it just wasn’t the paradigm for 100 years.

“Now it is. You want people to consume power when you have a peak of solar and wind … whether it’s charging vehicles or [other forms of] storage, so you can use it later.”

In many ways solar is easier to integrate than wind, he says, because it is much more predictable.

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