ISO reports 5,000MW battery storage capacity on Californian grid

California’s Independent System Operator (ISO) has reported more than 5,000MW of battery storage capacity is now online and fully integrated into the electrical grid.

According to the non-profit ISO, which oversees operation of California’s bulk electric power system, transmission lines and electricity market generated and transmitted by its member utilities, the 5GW of lithium-ion battery capacity on the electric grid can provide enough power for approximately 3.8 million homes for up to four hours before needing to be recharged.

The benchmark was reached in early June. As of July 1, it reached 5,600MW. This is a tenfold increase from the 500MW installed capacity in 2020, states the ISO.

Dispatch to meet intermittency

The batteries being added to the grid are charged during the day, when solar power is abundant, and dispatched primarily in the evening hours when demand is still high and the sun is setting and solar capacity diminishing.

The ISO has also, they add, worked closely over the past several years with industry representatives and stakeholders to design market and pricing protocols that enable grid operators to fully utilise the batteries’ unique capabilities.

Batteries’ state-of-charge, for instance, must be constantly monitored and verified to ensure power is available when needed. That requires market rules specifically designed to accommodate the behaviour of a resources that was not part of the state’s energy portfolio a few years ago.

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Elliot Mainzer, the ISO’s president and chief executive officer, commented on the benchmark, which was reached in early June:

“With our state experiencing more frequent climate extremes such as record heat waves and droughts, it is essential to invest in innovative technologies like energy storage to make sure we can continue to reliably power the world’s 4th largest economy.

“Just three years ago, we had about 500MW on the grid and this rapid growth of energy storage in California has significantly improved our ability to manage through challenging grid conditions.”

Summer heat incentives

The major driver behind the influx in storage on the grid, they state, has been a series of storage procurement orders authorised by the California Public Utilities Commission (CPUC), which requires regulated utilities to add storage to their portfolios.

These orders also call for significantly more storage in the coming years.

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“The CPUC’s plans call for a buildout of more than 10,000 MW in aggregate storage capacity on the grid by 2026,” explained Gabe Murtaugh, storage sector manager in the ISO’s market design group.

“This pace of adoption enhances reliability during the most challenging times of the day and helps ensure that new and existing solar resources are more effective on the grid.”

Last summer, when record heat and demand put California’s electric grid under new levels of strain, states the ISO, batteries played an important role in maintaining reliability during the critical evening hours, when solar is not available.

In coming years, the ISO is expecting to see the emergence of new storage technologies, not only battery solutions, as well as longer-duration storage resources that will be able to provide additional value to the grid.

“The storage fleet has been performing largely as planned,” Murtaugh added. “It has allowed us to dispatch additional power when it is most needed to help keep the grid balanced and the power flowing. We look forward to the further growth and technological diversification of this valuable new resource.”