California urges power conservation for second day amid severe heat

California's power grid operator has called for a second day of voluntary energy conservation as the state swelters under a heat wave. The California Independent System Operator has issued a Flex Alert for 6 to 9 p.m. Friday. 

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An alert was already in place for 5 to 10 p.m. Thursday. People are urged to set thermostats to 78 degrees or higher and avoid using major appliances. However, the system's CEO says California is unlikely to see a repeat of last summer's rolling blackouts. By Thursday evening, Cal ISO said they were encouraged by people's conservation efforts. 

The National Weather Service is warning of triple-digit highs in deserts and inland areas.

With winds not a serious threat in this heat wave, the heat itself is plenty capable of causing power outages and fires; sometimes in places where they rarely occur. That's why flex alerts and heat alerts exist, to encourage all of us to conserve and avoid the worst.

Since the rolling power outages of last August, numerous improvements have been made to the grid. But there are still vulnerabilities. 

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We are fortunate that the peak of this heat wave will be short lived. Despite improvements to the California electrical grid, California still imports a lot of power from other western states during peak demands. 

Severin Borenstein is an energy economist at Berkeley's Haas School of business and a member of the grid's board of governors. "If we run into another west wide, record setting heat wave, we could once again be in trouble," said Borenstein.

One often renewable resource, hydroelectricity, critical to California, is in very short supply this summer. 

"Although we've done a lot, we also have a dryer year because there's less hydro available," said Borenstein.

But right now, the biggest threat to the grid is cranking up the air-conditioning. A/C can quickly put excessive demand on the system, leading to stress on local electricity distribution equipment.

In prolonged heat waves, some older power equipment simply cannot cool down and fails from a technical kind of heat stroke. 

"Especially on lines where they're not used to having all the air conditioners and fans running and everything, especially in lower, cooler climates." said PG&E spokeswoman Deanna Contreras.

That's ominous because, sometimes when power equipment fails, there can be sparks and/or fires. 

"The dryness of our vegetation is dryer one month earlier than we usually see it, we usually don't see these levels until July. But, it's June and we're seeing these dry levels sooner," said Contreras.

Plan on a long, hot and frighteningly dry summer.

Associated Press contributed to this report.