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As Calif. solar records fall, curtailments of renewables rise


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As Calif. solar records fall, curtailments of renewables rise

Following a winter of intense storms that officially ended California's yearslong drought, the state's sunshine has returned to full strength. California's still-growing fleet of solar power plants took advantage of that in recent days, setting new state records for harnessing sunlight.

Large-scale solar power plants connected to the state's primary wholesale electric system hit a peak of 10,780 MW the afternoon of March 16, according to California ISO data, topping a prior record of 10,739 MW set in June 2018. In the late-morning sun of March 17, the grid operator also registered a new record share of state demand met by solar power of 58.6%.

As summer approaches, these records are likely to fall given the total 11,799 MW of installed solar capacity the California ISO reported on its grid as of March 4, mostly in the form of facilities relying on solar photovoltaic, or PV, technology. In addition, California had more than 7,900 MW of behind-the-meter PV installed at homes and businesses.

Accompanying California's solar records, however, are also rising levels of renewable energy curtailments, when solar-fueled midday generation exceeds the state's demand for electricity. Through March 17, the grid operator reported 144,833 MWh of available wind and solar cut in 2019, compared with roughly 83,000 MWh through the same date a year earlier.

Seeking to address this renewable energy waste and other market inefficiencies, the California ISO is proposing greater integration of grids throughout the western U.S., which could enable neighboring states to take more of California's renewable energy oversupplies. The Western Energy Imbalance Market, a real-time regional energy market that includes the California ISO and a growing number of other utilities in the West, has had some success in limiting renewable energy cuts.

In the fourth quarter of 2018, for instance, real-time market energy transfers helped to avoid curtailment of 23,425 MWh of renewables on the California ISO's grid, according to its latest report on market performance. Since 2015, the ISO has avoided 757,862 MWh in curtailed renewable generation through regional energy transfers.

The grid operator views battery storage as a way of saving excess solar for later use, when the solar production fades and demand for power peaks. As of March 4, however, the ISO reported only 136 MW of batteries connected to its system.

That pales in comparison to the power supply California needs to ramp up as the sun sets. On March 16, after California reached its latest solar output record, grid operator data shows a surge in natural gas-fired and hydropower production as well as imports. Within a three-hour period between 5 p.m. and 8 p.m., in-state gas generation jumped nearly 5,600 MW, in-state hydropower added more than 1,000 MW, and imports surged more than 7,000 MW.