On a paved expanse next to an electrical substation in Escondido, 30 miles north of downtown San Diego, sits a row of huge silver boxes. The site resembles a barracks, but instead of soldiers, the 24 containers house racks of battery packs.

This is the largest lithium-ion battery in the world, according to its developers. When the local grid needs more power, these batteries deliver, almost instantaneously. They can discharge up to 30 megawatts – roughly equivalent to powering 20,000 homes – and can sustain that level for up to four hours.

AES Energy Storage built the system in less than six months for utility San Diego Gas & Electric (SDG&E) in response to a four-month blowout at southern California’s Aliso Canyon natural gas storage facility. The rupture in October 2015 leaked more gas into the atmosphere than any other spill in US history.

After the leak was finally plugged in February 2016, utilities needed a fast-response energy source to deploy quickly in the densely populated areas around Los Angeles and San Diego. They wanted to prevent blackouts during periods of high demand, especially when customers crank up the air-conditioning on hot summer days.



Traditional grid solutions didn’t make sense. Gas peaker plants – which can be turned on quickly to meet demand – can take years to gain permission and be built, and they burn fossil fuels. You can’t drop a hydroelectric dam in the middle of a city. Solar power doesn’t help much in the evening, when summer demand is highest.



Instead, utilities Southern California Edison and SDG&E chose something relatively new: grid-scale batteries. What followed was the Escondido battery plus several others totalling about 100MW. The project became a major test case for the grid storage industry’s ability to make the grid more efficient and clean.



“To go from something that we thought of as kind of the future technology to, all of a sudden, it coming to the rescue so quickly – yeah, I think that’s a huge success story,” said John Zahurancik, president of AES Energy Storage.

Cleaner energy

A battery can absorb whatever power is available, whether it’s from coal, solar or nuclear. The ability to store and discharge power, though, has particular value for regions pursuing high levels of renewable energy.

“As more of our electricity starts to come from wind and solar, grid storage can collect extra electricity when the sun is shining and the wind is blowing, and then give it back during still nights when we need it to power homes and businesses,” says Sonia Aggarwal, vice president of San Francisco-based consultancy Energy Innovation.

Owners of old power plants should be shaking in their boots Sonia Aggarwal

California already gets about 8% of its power from solar and 9% from wind. This month, the legislature is voting on a 100% renewable target; if passed, the opportunity for storage to move that power around will grow.

Grid batteries offer a tantalising longer term application, displacing the gas plants needed to quickly meet peak electricity demand.



Batteries like those in Escondido deliver power instantaneously, but unlike a gas plant they emit no greenhouse gases or air pollution on-site. That makes them easy to slip into populated urban areas, where electricity users are clustered.



That ease of gaining permission and of construction made it possible for California to deal with the Aliso Canyon shortfall in months rather than the years needed for traditional gas plant construction.

“This is unprecedented speed for power infrastructure – it’s unheard of,” Aggarwal said. “If future projects can match this timeline – or even beat it – as grid storage prices continue to plummet, owners of old power plants should be shaking in their boots.”

An industry comes of age

Storage has taken time to catch on. The falling prices of batteries helped, but companies had to build up a track record to earn customers’ trust.

In September 2016, Tesla won a competitive bid for a 20MW project near LA for Southern California Edison (SCE); it delivered by the end of the year. Developer Greensmith launched one of the same capacity in Pomona, part of the Aliso project, also in less than four months.

Commercialising new battery technology is difficult and capital intensive. But companies that install battery projects have gained enough success to attract attention from corporations with deep pockets.

Just months after finishing its Aliso Canyon project, Greensmith was purchased by Wartsila, a global power equipment company. AES announced in July that it would spin off its storage unit into a joint venture with Siemens.

Tesla’s involvement in stationary storage followed its innovation in electric vehicles. Several automaker competitors are following suit, including Mercedes-Benz and BMW.



An ecosystem of home-storage providers has sprung up as well, although that market is hampered by the lack of economic return for homeowners. At the grid scale, utilities can measure the benefits of storage and pay for it.

As for the Aliso project, the first summer since installation is drawing to a close and the potential blackouts haven’t been an issue, says Dede Subakti, who directs operations-engineering services at the California Independent System Operator, a non-profit that oversees the flow of electricity through California’s grid.

“Energy storage allows us the flexibility to be able to manage what we need,” says Subakti. “[Batteries] became such a part of normal life for us that it’s just like any other resource.”