The biggest solar-plus-storage project in the US just came online

The largest combined solar and energy-storage project in the U.S. is now online and operating in California’s Mojave Desert.

The sprawling megaproject stretches across 4,600 acres in Kern County and is located on private land as well as the Edwards Air Force Base. It’s the biggest public-private partnership the U.S. Air Force has ever been involved in.

Known as the Edwards & Sanborn project, it was developed by Terra-Gen and built by Mortenson, an engineering, procurement and construction (EPC) contractor. Construction started in the first quarter of 2021 and completion was announced last week. The project includes an astonishing 1.9 million modules from panel-maker First Solar, and 120,720 batteries from LG Chem, Samsung and BYD — which makes it the largest such project in the U.S., according to Mortenson. The equipment is connected with more than 400 miles of wire, according to Brent Bergland, Mortenson’s VP of project development.

As solar makes up a bigger and bigger share of grid power, battery storage is needed to soak up surplus daytime energy and make it available for use later in the day. That’s why solar facilities are increasingly co-located with battery plants: Photovoltaics plus storage is the leading hybrid renewables combination. 

This particular project has a generating capacity of 875 megawatts from solar along with 3,287 megawatt-hours of energy storage. 

The project provides power to more than 10 customers or ​“offtakers” including Pacific Gas & Electric, Southern California Edison, the city of San Jose, the Clean Power Alliance and Starbucks. The offtake contracts with Terra-Gen, which will retain ownership of the project and operate it, are a combination of solar-only agreements, storage-only agreements and solar-plus-storage agreements, according to Bergland.

The batteries will be used for a variety of applications, including bulk storage to provide firm power through the evening, as well as other grid services.

“A project like this is a critical energy resource to help grid operators and generators manage an ever-changing system,” Bergland said. ​“These projects can be used to balance and support the grid in the middle of the day or provide an instantaneous support to the market.”

It was financed by the usual infrastructure money suspects, including J.P. Morgan, Deutsche Bank, BNP Paribas, CoBank, U.S. Bank, ING and Nomura, across two financing rounds totalling more than $1.7 billion in the form of construction and term financing, revolving credit, tax equity and tax-equity bridge facilities.

Bergland emphasized that Mortenson had a positive experience with the project’s 100 percent unionized workforce, which ​“approached a peak of 1,000.”

Bergland, a veteran developer, said that this is ​“probably the most complex project” he’s worked on — given its size, the large workforce, three separate interconnects to the grid, the combination of solar and storage technologies and vendors, and the variety of offtake agreements. 

The rise of utility-scale solar and grid storage are bright spots in the U.S. renewable energy landscape. The power of the learning curve, driven by automation and software improvements as well as panel efficiency improvements, continues to drive down the cost of big solar, already the lowest-cost generation source. Batteries are moving down the cost curve as well, and storage capacity is set to nearly double in the U.S. this year.

Expect these forces to lead to many more combined storage and solar megaprojects in the years to come.