Switched on in December 2017, a 100-megawatt (MW) Tesla battery in Australia is the world's largest utility-scale battery installation. But maybe not for long. Last week, Pacific Gas & Electric (PG&E) requested approval from the California Public Utilities Commission (CPUC) for four energy storage projects totaling approximately 567 MW.

The idea formulated in January when the CPUC authorized PG&E to launch an accelerated solicitation for energy storage projects capable of meeting reliability needs in the northern central valley region of PG&E's service territory.

PG&E issued its request for offers in February and selected one offer for a utility-owned project and three offers for third-party-owned projects, all to be located within the South Bay-Moss Landing local sub-area.

The proposed utility-owned project is a 182.5 MW lithium-ion battery energy storage system (BESS) located within PG&E's Moss Landing substation. The BESS would have an expansion capacity to 1.1 GW. This transmission-connected BESS will address local capacity requirements and will participate in the California Independent System Operator markets, providing energy and ancillary services.

The three contracts awarded for third-party-owned projects are also lithium-ion battery projects. These are a 10-MW aggregation of behind-the-meter batteries located at customer sites and interconnected to local substations within the South Bay-Moss Landing local sub-area; a stand-alone, transmission-connected 75-MW BESS located near the city of Morgan Hill; and a stand-alone, transmission-connected 300-MW BESS located in Moss Landing.

All four would be designed to feed power to the grid when consumption exceeds normal levels during blackouts and other service interruptions, and each would be capable of providing power to its region's electric grid for up to four hours.

"Energy storage plays an increasingly important role in California's clean energy future, and while it has been a part of PG&E's power mix for decades, ... recent decreases in battery prices are enabling energy storage to become a competitive alternative to traditional solutions," said Roy Kuga, vice president, grid integration and innovation, for PG&E. "As a result, we believe that battery energy storage will be even more significant in enhancing overall grid reliability, integrating renewables, and helping customers save energy and money."

PG&E has come under fire recently for its alleged responsibility for up to 12 of 2017's devastating California wildfires, and the utility has said it may face bankruptcy as it sorts out its culpability with regard to California laws. It is unclear how this development could affect these BESS projects.

If approved by the CPUC, the first of the four BESS projects is scheduled to come online by the end of 2019, and the others are scheduled to come online by the end of 2020.