Stealthy grid infrastructure developer LS Power now operates the largest grid battery in the world.

The Gateway Energy Storage project launched earlier this summer, with an initial tranche of 62.5 megawatts/62.5 megawatt-hours. That was enough to make it the most powerful battery in the U.S. But LS Power had more up its sleeve, and now Gateway can charge or discharge 230 megawatts for one hour, expected to rise to 250 megawatts by the end of the month.

That would be big news for the storage sector in any event, because it exceeds the previous largest battery, the Tesla-supplied Hornsdale plant (150 megawatts/193.5 megawatt-hours). But its arrival coincides with an energy crisis as California struggles to produce enough power to keep the grid running amid a historic heat wave.

California shut down enough power plant capacity in recent years that it now has trouble supplying air-conditioning demand on hot days in the hours when the sun sets and solar generation drops off. Meanwhile, imports from neighboring states have been constrained because those states are facing the same heat wave.

A wave of massive battery projects is under construction in California, many of which are designed to step in for the retiring gas and nuclear plants by shifting solar generation into the hours after sunset. Gateway is the first of this cohort to come online. It alone wields more power than all the other batteries connected to the grid managed by the California Independent System Operator. 

"By charging during solar production on off-peak hours and delivering energy to the grid during times of peak demand for power, our battery storage projects improve electric reliability, reduce costs and help our state meet its climate objectives,” LS Power Head of Renewables John King said in a statement.

Batteries played a clear role in meeting the peak demand between 6 p.m. and 8 p.m. on Friday, according to CAISO data. But the available batteries only got up to around 140 megawatts, not nearly enough to avoid rotating outages that evening. Still, record-high power prices offered a bounty for those batteries that were able to participate.

Gateway reached 200 megawatts commissioned on August 1 and added 30 megawatts more by Monday afternoon to deliver extra peak power for the heat wave, King said in an interview with GTM. The facility will expand to three hours of duration next summer and four-hour duration later on. 

The developer didn't plan on the construction wrapping up in the midst of a historic power supply crunch, King said. LS Power began work on it five years ago, in response to California's surging solar generation and decision to shut down gas plants that used ocean water for cooling. Back then, nobody had built batteries anywhere near this kind of scale.

"Battery storage, when we started, was very expensive," King said. "It wasn’t clear, exactly, that it would work, but when you’re in development you’ve got to look forward a little."

The company's 40-megawatt Vista Project came online in 2018, in time for that year's heat wave and price spikes, which provided more data for the business case. LS Power shored up Gateway's business plan by selling energy products to power retailers and community choice aggregators, King said. One type of product involves the customer providing surplus midday power, with Gateway promising to store and return that power in the evening, insulating the customer from price spikes. 

When California regulators ordered the utilities last fall to obtain more capacity, Gateway won Resource Adequacy contracts with Pacific Gas & Electric and Southern California Edison. Those obligations kick in late next year.

"We built Gateway as a shorter duration project, but we built it so we had room in the buildings... to expand that capacity when we had customers for that capacity," King said.

LS Power hired NEC Energy Solutions to integrate the Gateway project, which uses battery cells manufactured by LG Chem. A time-lapse video shows the warehouse-like structure popping up at East Otay Mesa between September 2019 and July 2020.

Gateway currently is participating in all the CAISO markets, King said, and has "done really well" responding to the CAISO signals amid the heatwave.

Updated with comments from John King.