The Energy Storage Report 2024

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California solar-plus-storage project with world’s largest BESS fully online


The Edwards & Sanborn solar-plus-storage project in California is now fully online, with 875MWdc of solar PV and 3,287MWh of battery energy storage system (BESS) capacity, the world’s largest.

The 4,600-acre project in Kern County is made up of 1.9 million PV modules from First Solar and BESS units from LG Chem, Samsung and BYD totaling 3,287MWh of energy storage capacity.

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That makes it bigger than the current largest BESS in the world, Vistra’s 750MW/3,000MWh facility at Moss Landing, also in California, which also came online in two phases.

It has now reached ‘substantial completion’ and is ‘fully online’, Mortenson said this week. has asked Mortenson and project owner Terra-Gen what ‘substantial completion’ means and will update this article if and when a response is received.

Engineering, procurement and construction (EPC) contractor Mortenson started construction around three years ago and the first phase, comprising about half of the total capacity, came online in late 2021.

The project has an interconnection capacity of 1,300MW. Its offtakers include the city of San Jose, utilities Southern California Edison (SCE) and Pacific Gas & Electric (PG&E), community choice aggregator (CCA) Clean Power Alliance, and coffee chain shop Starbucks.

Although the MW power of the BESS has not been revealed, most BESS projects in California are 4-hour duration (to qualify for grid operator CAISO’s Resource Adequacy framework) which would make this BESS 821MW.

Part of the project is located on the Edwards Air Force Base and Mortenson said the project was the largest public-private collaboration in US Department of Defense history.

“Now fully operational, this facility is a transformational project in the industry and is providing resiliency to the grid,” said Brian Gorda, VP of engineering at Terra-Gen. 

Terra-Gen’s other notable energy storage project is the 140MW/560MWh Valley Center BESS, also in California, though that project was in the headlines in 2023 for the wrong reasons (including a battery fire and a theft of decommissioned batteries).’ publisher Solar Media will host the 5th Energy Storage Summit USA, 19-20 March 2024 in Austin, Texas. Featuring a packed programme of panels, presentations and fireside chats from industry leaders focusing on accelerating the market for energy storage across the country. For more information, go to the website.

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