An already groundbreaking year for battery storage in the United States gained further momentum with Vistra Corp.'s recently granted permit to expand an energy storage system under construction at its natural gas-fired Moss Landing CC on the shores of California's Monterey Bay to 1,500 MW/6,000 MWh.

Underpinned by two resource adequacy contracts with Pacific Gas and Electric Co. for a combined 400 MW, the Vistra battery complex at Moss Landing could nearly quadruple in size after the Monterey County Planning Commission in late July approved the developer's application to build four 300-MW battery blocks next to a previously approved 300-MW section.

At 1,500 MW of four-hour lithium-ion battery capacity, Vistra's Moss Landing storage station would be easily the largest battery system in the U.S. and the world, according to data tracked by S&P Global Market Intelligence. The first 300-MW phase is planned for completion by the end of 2020, followed by a second 100-MW phase in 2021.

While several U.S. developers are advancing projects in the 100- to 400-MW range, Vistra's project is positioned to emerge as the power sector's first gigawatt-sized battery storage facility. And next door to Moss Landing, Pacific Gas and Electric is building its own project, the Tesla Moss Landing Battery Energy Storage Project (Elkhorn), scheduled for completion in 2021.

The Texas-based company is preparing to expand the project "should market and economic conditions support it," Vistra President and CEO Curtis Morgan said in an email. "With this new permit in place, Vistra is working on the related infrastructure upgrades so that we will be able to move quickly when opportunities to add additional storage capacity arise."

Given California's mandate to supply 60% of its retail electric sales with renewable energy resources by 2030, compared to an estimated 36% in 2019, and its target of 100% carbon-free power by 2045, additional demand seems inevitable.

Away from fossil fuels

One of the largest carbon emitters in the U.S. power sector, Texas-based Vistra is emerging as a key partner for California as it helps the state balance rising volumes of variable renewable energy generation with energy storage and diversifies its own fossil fuel-heavy power mix with investments into renewables and batteries.

"California is certainly the most attractive location for us to pursue further battery investment at economic terms given the resource adequacy contracts," Morgan said.

Vistra's moves in California are part of its plan to slash its emissions by 50% by 2030 and eventually exit fossil fuels. The company is eyeing additional battery storage and solar power projects in Illinois and in Texas, where it supplies retail electricity.

"We believe the power sector will ultimately evolve entirely away from coal and, in the longer term, away from natural gas," Morgan said. "This is why we expect to dedicate roughly 25% of our free cash flow to investing in renewables and batteries."

Putting a price on carbon emissions is the "most effective and equitable" approach to achieving decarbonization across all sectors of the economy, according to Morgan.

But the power sector still requires conventional resources to ensure grid reliability as batteries and other alternatives emerge on a large scale, the executive added. Vistra views gas-fueled power plants as "the most effective transition resource" because of their efficiency, flexibility, affordability and lower carbon emissions compared to coal.