Electricity Markets

CMUA details how public power utilities helped CAISO respond to heat wave, stress on grid

In a recent letter to a California state lawmaker, the California Municipal Utilities Association (CMUA) details how public power utilities in the state took a number of actions on the supply and demand side to help the California Independent System Operator (CAISO) manage stress placed on the California power grid last month due to soaring temperatures.

The Aug. 27 letter was sent to California Assemblyman Chris Holden by Barry Moline, Executive Director of CMUA, and Patrick Welch, Legislative Director for Energy at CMUA. Holden is Chair of the California Assembly Committee on Utilities and Energy.

California last month experienced a record setting heat wave that caused CAISO to initiate at least two Stage 3 emergencies that led to load shedding events, commonly referred to as rolling blackouts.

In response, Holden recently wrote a letter to his Assembly colleagues outlining the issues and calling for an oversight hearing in early September.

Supply side actions

In their letter, Moline and Welch detailed the supply side actions taken by public power utilities in the state that helped the California grid operator during the recent heat wave and resulting load shedding events.

On the supply side, CMUA noted that publicly owned utilities (POUs) in non-CAISO balancing authority areas provided power to the CAISO grid during peak periods when it was needed most, and POUs with owned generation ramped up output.

While closely monitoring their own supply and demand trends, utilities in at least two of the POU balancing authority areas – the Los Angeles Department of Water and Power and SMUD – were able to provide power to the CAISO grid when demand was high and supply limited, helping to stave off even worse rolling blackouts, the letter noted.

For example, SMUD – which is in the Balancing Authority of Northern California (BANC) footprint – provided 1,100 megawatt-hours of emergency assistance to CAISO, and through the Energy Imbalance Market (EIM) provided CAISO another 5,700 megawatt-hours during critical peak-load hours.

While the capacity varied by hour, at its peak, SMUD’s emergency sales plus EIM transfers provided up to 530 MW of support for the CAISO grid.

Another POU, Roseville Electric, which is also in the BANC footprint, provided 20-40 MW of its CAISO-located capacity amounting to 1,600 megawatt-hours, and delivered an additional 500 megawatt-hours to CAISO from BANC.

In total, Roseville provided 2,100 megawatt-hours during the critical peak-load hours, or 10% of Roseville Electric’s total energy supply.

LADWP provided significant assistance to the CAISO grid, CMUA noted. Among the many actions it took, LADWP was able to use available transmission to import up to 882 MW of power and deliver it to CAISO during peak demand periods.

In addition, POUs within the CAISO footprint ramped up their power output as much as possible. As an example, using their own generating units, Pasadena Water and Power provided 150 MW of electricity for the CAISO grid during peak periods.

Public water agencies and POUs were also able to ramp up hydroelectric generation to assist the CAISO grid.

Hydroelectric dams are an important resource for meeting baseload power needs and also provide flexible capacity due to the ability to quickly ramp up production based on water conditions.

CMUA’s water agency and POU members that own hydroelectric dams ramped up generation, often to maximum nameplate capacity, to provide more power to the CAISO grid.

The Yuba Water Agency, which was already providing 338 MW of peak time period power during the heat wave, saw the need and increased output from its facilities by 20 MW. In total, Yuba provided enough clean power for 350,000 homes.

And the San Francisco Public Utilities Commission also increased power output at Hetch Hetchy by over 150 MW during peak periods throughout the heat wave. This power was provided to the CAISO grid.

Similarly, the East Bay Municipal Utility District increased power output by 10.2 MW and the Placer County Water Agency ramped up its hydroelectric generation by 12 MW.

Demand side actions

POUs and public water agencies also took specific actions to reduce strain on CAISO grid, while encouraging customer conservation.

When feasible, water agencies used the authority under a gubernatorial executive order to switch some water pumping and water treatment operations to backup generators, or to change the level of water pumping, thereby reducing strain on the CAISO grid, Moline and Welch noted.

When these actions were implemented it resulted in meaningful demand reductions, the letter said.

For example, the Metropolitan Water District of Southern California changed pumping operations on the California River Aqueduct to reduce electric demand by 145 MW.

As another example, the Rancho California Water District was able to reconfigure its operational strategy during peak electric demand hours and save 5.5 MW of demand. The Orange County Water District was also able to shift 12 MW of energy use to off-peak times.

Moreover, throughout the heat wave all POUs encouraged customers to conserve energy by setting their air conditioner thermostats at a higher temperature, closing window blinds, and shifting major appliance use to before or after peak hours.

“As local electric providers, POUs also have close relationships with their customers and were able to conduct direct outreach to larger customers to encourage demand reductions,” the letter said.  Silicon Valley Power, for example, was able to work with its large customers in its service territory to reduce grid demand by 85 MW.

In some cases, POUs took specific actions to reduce their electric imports from the CAISO grid. As an example, the Modesto Irrigation District reduced its imports from the CAISO by 230 MW, instead relying on local generation and imports from the Pacific Northwest.

“I think the CAISO was caught off-guard and didn’t fully communicate the emergency we were in on August 14, the first day of the heat wave,” Moline said. “But once they put out the word, CMUA members responded immediately, providing reserve power to the CAISO and strongly messaging to customers to cut demand during the daily peak period. You can even see our efforts in the daily statewide demand graphs – the peak just flattens. I pretty sure our combined efforts are the reason the state experienced no more significant outages.”