Houston — The California Independent System Operator set an all-time renewables peak Saturday, a day after setting a new wind peak record, according to ISO data.
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Wind generation reached 4,787 MW at 5:34 pm PDT Friday (0034 GMT Saturday), a new all-time wind peak record. Less than 24 hours later, the ISO hit an all-time peak of 67.2% of demand served by renewables at 2:55 pm Saturday. That was the third such record in as many months.
"It was a sunny and windy day, thus more generation," Cal-ISO spokesman Steven Greenlee said Tuesday.
As renewable generation rose above 14,000 MW around 3 pm Saturday, Cal-ISO total actual hourly integrated load fell to 21,371 MW at the same hour, according to ISO data. For comparison, total actual hourly integrated load was above 22,000 MW at 10 am and rose above 25,500 MW by 10 pm, but dipped in between as renewable generation served load.
On Saturday, solar generation made up 17.1% of the generation share, wind accounted for 16.3% and hydro was 19.2%, according to ISO data.
Thermal generation, which includes nuclear, natural gas and coal, dropped to 11% of the generation mix on Saturday, according to ISO data. That was the lowest percentage level seen in the past seven years for which data is available.
The sudden spike in renewables depressed real-time prices.
SP15 on-peak real-time fell day on day to $20.28/MWh Friday with off-peak at a premium at $25.56/MWh, before prices dipped further Saturday with on-peak at negative 94 cents/MWh Saturday and off-peak at $14.08/MWh, according to ISO data. It was the fifth time this month that off-peak real-time has been at a premium to on-peak.
Renewable generation has been soaring in California compared with last year. Hydro generation has averaged 115,474 MWh/d so far this month, up 31% from May 2016, according to ISO data. Month-to-date solar generation has averaged 43,590 MWh/d, up 27% from last May. Meanwhile, thermal generation is down 16% year on year to average 121,350 MWh/d.
The previous renewables record was 65.2% of load set April 23 at 2:53 pm with solar and wind making up 57.6%, Greenlee said. Before that, the record was 56.7% set on March 23.
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