CAISO issues flex alert, grid restricted maintenance notice on tight power supply

The California Independent System Operator issued a flex alert as well as a grid restricted maintenance operation notice for Sept. 8 because of expected tight power supplies and gas supply concerns.

Real-time five-minute interval prices around 8 am PT were above $100/MWh, according to CAISO data. Day-ahead prices were reaching the highest levels since the February winter storm.

SP15 on-peak day-ahead for Sept. 9 delivery was in the low $220s/MWh on the Intercontinental Exchange, 69% higher than the locational marginal price for Sept. 8. SP15 on-peak balance of the week is in the mid-$140s/MWh on ICE.

A spike in spot gas prices helped drive up power prices, with SoCal city-gate trading around $20.040/MMBtu on ICE for Sept. 9 flow, nearly double day on day, according to S&P Global Platts pricing data.

Driven by air conditioning

"With above-normal temperatures in the forecast for much of California and the West, the power grid operator is predicting an increase in electricity demand, primarily from air conditioning use," according to a Sept. 7 CAISO statement. "The increased demand can make electricity supplies tight and strain the power grid, making conservation essential."

Temperatures as high as 104 degrees Fahrenheit were expected Sept. 8 in Sacramento, 15 degrees above normal, according to CustomWeather. Excessive heat warnings remain in effect across the Mojave Desert, with heat advisories over most of the interior valleys of California, according to the US National Weather Service. Record temperatures can be expected each afternoon at many locations, shifting into the central High Plains by Friday.

CAISO forecast peakload around 42.04 GW Sept. 8, 42.275 GW Sept. 9 and 40.379 GW Sept. 10. So far this month, peakload has averaged 36.195 GW, down 9.7% from the same time last year and down 3.6% from August, according to CAISO data

"To take full advantage of all available supply, the ISO has also issued a restricted maintenance operation ... from noon to 9 pm, notifying ISO participants to avoid taking grid assets offline for routine maintenance until the restricted maintenance operation is lifted," according to a Sept. 7 CAISO statement.

The flex alert is in effect 4-9 pm Sept. 8, according to CAISO. A flex alert is a call to voluntarily conserve electricity.

"Conserving electricity during the late afternoon and early evening is crucial because that is when the grid is most stressed due to higher demand and declining solar energy production," according to the CAISO statement.

Battery outage

There has been a push to add capacity to the grid after rotating outages in August 2020, the first since 2001. CAISO added 1 GW storage since last summer and currently has 1.5 GW of storage on the system, with expectations to reach 2.5 GW by the end of the year.

California has the most installed battery storage in the US at 1,390.6 MW, according to the American Clean Power Association's Q2 report. The state has a goal of 100% carbon-free electricity by 2045.

Vistra's 300-MW Moss Landing Energy Storage Facility Phase I, which connected to the grid in January, is offline after a number of battery modules overheated Sept. 4. The system, in Monterey County, is made up of more than 4,500 stacked battery racks or cabinets, each containing 22 individual battery modules, which capture excess electricity from the grid, largely during high solar-output hours, and can release the power when energy demand is at its highest and solar electricity is declining, usually early morning and late afternoon, Vistra said Jan. 6.

The 100-MW Moss Landing Phase II, which was announced complete in August, remains in operation.