California duck curve 'alive and well' as renewable, minimum net load records set

High wind and solar production combined with low demand led the California Independent System Operator to reach a new record of 92.5% of load served by renewables and 98.1% of load served by carbon-free resources, the ISO has reported.

The records were set at about 12:30 pm March 13, CEO and President Elliot Mainzer said at a board meeting March 24. That same day, the ISO established a new minimum net load, which is load minus wind and solar generation, of 3.614 GW.

"The duck curve is alive and well in California," Mainzer said.

In certain times of the year, the difference between net load and electricity from variable generation resources over a 24-hour period produces a "belly" appearance in the mid-afternoon that quickly ramps up to produce an "arch" similar to the neck of a duck — hence the industry moniker of "The Duck Chart," according to the ISO.

Wind generation averaged 22% of the total fuel mix March 13, the highest daily average on record, according to ISO data. That jump in wind generation drove wind and solar generation to a combined daily average of 39.2% of the mix, more than double the three-year average.

SP15 on-peak day-ahead locational marginal prices were $19.52/MWh for March 13, 34% lower than the month-to-date average for March 2021, according to ISO data. Although, March 13 was a Saturday when prices tend to be lower from less power demand on the system.

In addition, the ISO observed its maximum three-hour net load ramp of 17.259 GW Feb. 28, Mainzer said about records since the last monthly board meeting.

California clean energy future

California's Senate Bill 100 established the state's policy for 100% clean energy by 2045 and expanded the renewable portfolio standard to 60% renewables by 2030. The number of US states with 100% renewable , carbon-free or net-zero emission goals or proposals in the works has nearly doubled in the last year, according to an S&P Global Platts analysis.

"We need to figure out how we work with out battery partners and others across the West," Mainzer said about continuing to work to decarbonize the grid.

The ISO has made significant progress in working with the battery storage community to support system reliability during stressed operating conditions through the establishment of a minimum state of charge requirement that will be applied when the day-ahead market indicates the potential for insufficiency, Mainzer said.

"We are now beginning to initiate longer-term market design work with storage providers and other stakeholders to develop longer-term market design enhancements that will support system reliability while more effectively addressing the commercial and asset optimization needs of what will ultimately be a more diverse fleet of storage resources," according to the CEO's report.