California to expand battery storage, wind and solar to meet renewable goals

by Michael Green
'Curtailments of solar-powered electricity generation have increased in the CAISO region'. Graphic: EIA based on CAISO data
California plans a major expansion of renewable power generation and battery storage capacity by the end of this year, to help meet the state's target of 50% renewable generation by 2025, the U.S. Energy Information Administration (EIA) has said.

The California Independent System Operator (CAISO) plans to add another 1.6 GW of utility-scale solar capacity and 0.4 GW of onshore wind turbine capacity in 2021, the EIA said yesterday.

And CAISO is expecting to add 2.5 GW of battery storage capacity in 2021, according to an EIA survey of recent and planned capacity changes.
"Renewable generators can charge these batteries with electricity that would otherwise have been curtailed,” the EIA said. "Combined, these two technologies represent 44% of CAISO’s total capacity additions in 2021.”

Increased curtailments

Hydrogen production and hydrogen-based energy storage could also help reduce solar curtailments, according to the EIA. The hydrogen would be produced by electrolysis using surplus renewable electricity that would otherwise be curtailed, then stored for later use.
Curtailments of solar-powered electricity generation have increased in the CAISO region – the part of the electric grid that covers most of the state. In 2020, CAISO curtailed 1.5 million megawatt-hours of utility-scale solar, or 5% of its utility-scale solar production.

Grid operators curtail electricity production from solar and wind generators when supply exceeds demand. In 2020, solar curtailments accounted for 94% of the total energy curtailed in CAISO, according to EIA data.

Solar curtailments tend to be greater in the spring months when electricity demand is relatively low – because of moderate temperatures lowering demand for heating and cooling – and solar output is relatively high. In the early afternoon hours of March 2021, CAISO curtailed an average of 15% of its utility-scale solar output.

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