CAISO forced to curtail 15% of California utility-scale solar in March, 5% last year

Last year California’s solar power generation produced more electricity than customers needed.

A new report by U.S. Energy Information Administration (EIA) indicated that the California Independent System Operator (CAISO) curtailed about 1.5 million MWh of utility-scale solar power in 2020. That net generation represents about 5 percent of the utility-scale solar produced in the state.

Grid operators curtail electricity production from solar and wind farms when supply exceeds demand, particular in spring months when electricity demand is lower and generation still high. In March of this year, for example, CAISO curtailed an average 15 percent of its utility-scale solar output system-wide, the EIA report reads.

California is, by far, the biggest solar power generator in the U.S. To reach its 2025 goal of 50-percent renewable generation, CAISO plans to add another 1.6-GW of utility-scale solar and 400 MW of onshore wind turbine capacity this year, according to reports.

Small-scale solar, such as rooftop and community projects, continues to grow dramatically in the state. Customer-sited solar generation also decreases the need for CASIO-operated generation, leading to more curtailments, according to EIA.

A buildup of future energy storage capacity can help avoid future higher levels of solar curtailment. California is commissioning several major utility-scale battery projects this year and plans to add 2.5 GW for 2021 within CAISO, the report shows.

The system operators’ Energy Imbalance Market also offers a real-time market for participants outside of CAISO to buy and sell energy balance demand and supply. Last year, EIM trades helped avoid 16 percent of total possible curtailments, according to the EIA.

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