CAL-ISO offers sobering wind assessment: It's growing but can't be relied on as capacity

California legislators need to remember wind generation is not the answer to California's growing energy capacity needs, said Yakout Mansour, president and CEO of the state's Independent System Operator.

On August 9, while giving a summary of the ISO's performance during last month's heat wave and energy crunch, Mansour told California's Senate Committee on Governmental Organizations that while conservation, demand response, interruptible programs, and voluntary load reductions played a "significant role in making it through the tough days," wind resources were on average only supplying about 5% of their installed nameplate power capacity during peak hours.

It was a good time to educate the legislatures, Mansour told Platts in an interview on August 17. "It is very important for them to know what [wind power] does and what it doesn't do," Mansour said. "This was a good time to be honest with them."

The California Public Utilities Commission is requiring investor-owned utilities in California to have 20% of their energy portfolios include renewable resources such as wind, solar, geothermal, and biomass, by 2010. This energy does not have to be part of the utilities' capacity. Instead, a utility has to demonstrate through ownership of renewable energy credits that it has supported an amount of renewable generation equal to 20% of their annual kWh sales.

"You really don't count on wind energy as capacity. It is different from other technologies because it can't be dispatched," said Christine Real de Azua, assistant director of communications for the American Wind Energy Association.

The ISO believes wind is a great resource for replacing power purchased from gas and coal power plants, "but it is not a panacea," and ISO spokesman said. "We advocate a balanced portfolio." Generators will still need to supplement the intermittent nature of wind by shaping hydroelectric output or with new coal- and gas-fired generators.

There is about 2500 MW of installed nameplate wind generation currently operational in California, according to ISO documents. Wind turbines typically can produce at 25% to 30% of capacity according to the American Wind Energy Association. This would mean that on average during a blustery day in California wind farms could produce about 625 MW to 750 MW.

Daily snapshots of available wind energy when the ISO reached its peak from July 22 through July 25 was on average about 6% of capacity or about 150 MW, according to Cal-ISO data.

California's rapidly expanding energy needs became quite clear when demand in July went about 6% above the worst-case summer scenario accessed by the ISO earlier this year. ISO control area loads hit a record high of 50,270 MW at about 2:45pm July 24. At that time, wind in California was contributing about 255 MW, or about 10% of wind nameplate capacity.

Ironically, the very heat storm that caused loads to spike also caused decreased wind flows.

Sam McCown, a meteorologist for the National Oceanic and Atmospheric Administration, said that there is sometimes significantly less wind in the center of a high-pressure heat wave. The high pressure leads to sinking air and tends to repress the movements of air masses. "It is on a scale large enough to show up on your daily weather maps," he said. Conversely, areas on the outskirts of a heat wave could get more wind, he said.

Meteorologists and wind power analysts said abnormally hot weather in California may not always have such a depressing effect on wind generation. "It's not a clear-cut thing with a simple answer like that," said Mark Ahlstrom, CEO of WindLogics, a wind resource analysis and weather forecasting company based in St. Paul, Minn.

Wind in California is thermally driven, said Bruce Lee, senior atmospheric scientist at WindLogics.

Under normal summer conditions in Southern California, winds blow through passes in the Tehachapi Mountains of California that connect the San Joaquin Valley with the Mojave Desert. Often the heat from the desert sucks the air from the coastline through the passes.

In the meantime, load-serving entities know not to count on the full nameplate capacity of a plant, said a market participant who trades primarily in California markets, "Wind doesn't help from a keep-the-lights-on-perspective," the source said.