How extreme heat is affecting California’s electrical grid

How extreme heat is affecting California’s electrical grid
After last year’s outages, steps have been taken to prevent a repeat

Less than a year after a severe 热浪 triggered rolling blackouts in 加利福尼亚州, soaring temperatures are once again straining the state’s electrical system.

加利福尼亚州’s grid operator on Thursday called on residents to reduce their energy use as triple-digit heat seared the central and southwestern parts of the state and its neighbors, breaking temperature records in some places. The “flex alert” is the first issued by the California Independent System Operator so far in 2021, coming days before the official start of 夏天.

Officials and experts said the grid is better equipped to handle a hot-weather surge in electricity demand than it was last August, 什么时候, for the first time since 2001, residents had to endure rotating outages because of the heat (wildfires have separately prompted power companies to cut electricity to prevent new blazes). But California’s system could still face electricity shortfalls if the region gets scorched again this summer.

问: Why is California asking people to cut back on electricity?

一种: The California ISO’s “flex alert” asks residents to voluntarily cut back on their electricity use between 5pm and 10pm, when demand peaks.

During those hours, people come home from work or school, fire up their air conditioners and switch on appliances, all of which increases the load on the grid. As the sun sets, electricity from solar energy sources diminishes, meaning there’s less power to go around. 同时, temperatures outside remain high well into the evening and structures retain the heat they’ve absorbed during the day, pushing air conditioning loads higher.

Conserving energy at those key times helps reduce stress on the grid that can lead to blackouts.

“It’s the first stage of saying, ‘We might have a problem so please don’t use electricity without considering what you’re doing,’ “ said Jim Williams, an expert in energy systems at the University of San Francisco. “You’re relying on the good will of the people to chip in.”

Thursday’s “flex alert” calls on Californians to keep their thermostats to 78F (26C) and higher during the evening and use a fan instead of air conditioning when possible. It also asks residents to draw their drapes, turn off second refrigerators and put off tasks such as vacuuming, laundry and dishwashing until later in the night.

“Tens of thousands of households modestly adjusting their consumption can have a big aggregate impact,” Mr Williams said.

问: How likely are rolling blackouts?

一种: Last summer, the California ISO ordered rolling blackouts after electricity reserves dropped below a critical threshold during the August heat wave that baked the Western United States. Hundreds of thousands of customers were affected by the outages, which lasted about an hour at a time.

Elliot Mainzer, the California ISO president, said this week that another round of outages was unlikely in this case but urged residents to rein in their electricity use.

“Californians have stepped up many times before when asked to pitch in,” Mr Mainzer said in a call with reporters, “and I’m confident they will do so.”

States in the West share power with each other, with California in particular importing a significant amount of its electricity from Arizona, Nevada and the Pacific Northwest. Last summer’s heat wave fell hard across several states simultaneously, driving up demand throughout the region and leaving less power for California to import. One of the few mercies of the current wave is that it isn’t quite as widespread, 专家说.

“This has been a vast heat wave but the intensity has varied across the West,” Mr Williams said. “When everybody goes through a heat wave, nobody has anything to share. Last August was a wake-up call that you can’t always rely on the West having excess energy flowing around.”

问: Is the grid better prepared than it was last year?

一种: After last summer’s outages, officials took a number of steps to avoid a repeat. They delayed the decommissioning of some gas-fired power plants to squeeze out more generation. Utilities started installing more batteries for backup during peak load in the evenings when solar generation wanes. Officials have also proposed changes to market rules to prevent electricity from being exported when demand is high.

“More blackouts are not an inevitability,” said Steven Weissman, an energy law expert and lecturer at Berkeley’s Goldman School of Public Policy. “There were improvements made. The question is: Were those improvements enough? It’s very difficult to predict the answer to that question.”

In a May report, California ISO officials said they expected energy supply conditions to be better in 2021 than last year, but cautioned that they continued “to see potential challenges in meeting demand during extreme heat waves.” The report said the operator remained “guardedly optimistic regarding its operations this summer given the measures already taken.”

问: How could this year’s 干旱 affect power availability?

一种: California’s deepening drought leaves the state vulnerable to grid disruptions.

The state relies heavily on hydroelectric power both produced in the state and imported from the Northwest. But reservoirs are drying up, with water levels falling so low in Lake Oroville that officials are weighing whether to idle the area’s hydropower plant for the first time ever.

“A second year of significantly lower than normal hydro conditions, virtually unchanged forecasted load levels under normal conditions, and increased possibility of extreme weather events indicate the ISO may still face challenges in meeting load this summer,” the California ISO noted in its report last month.

In wet years, hydroelectric power is a highly flexible resource, available to supplement other power sources when demand is high. A prolonged reduction in hydroelectric power makes it harder to deal with those surges.

“You can pick when you use ityou can save the water behind the dam and use that potential energy during the very worst times,” said Mr Williams. “But you don’t know quite when the worst time is going to be.”

“A dry year means less water behind the dam,” Mr Williams added, “and you have fewer bad days when you get to use that water.”