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Sudden Surplus Calls for Quick Thinking by Matthew L. Wald New York Times, July 7, 2010

Hopes to increase use of green technology and create jobs

Engineers say that if the power grid becomes more reliant on renewable energy, a lot of new transmission lines will have to be built at some point or there will be unhappy consequences. Mostly this problem has been predicted rather than experienced. But the future may have arrived last month, when the Bonneville Power Administration, a federal agency that oversees power transmission in the Pacific Northwest, had more energy than it could comfortably use.

The BPA is accustomed to a surplus of hydroelectric power in the spring, as the winter snow pack melts. Last winter there was only about 60 percent as much snow as usual, according to energy experts. But in the late spring heavy rain arrived. Unlike snow melt, which can be predicted by temperature, rainwater gives little warning. And suddenly there was a surplus.

"This year was a little more severe and a little more unexpected," said Michael C. Milstein, a spokesman for the power administration.

In a normal spring, the BPA first shuts down its fossil-powered plants, then exports as much as it can so its neighbors can do the same. This year, he said, "we were essentially asking other utilities to shut down their thermal plants, and most of the coal and gas plants in the region were shut down. They were taking low or no-cost power from us."

When it runs out of neighbors that can take the power, the BPA can also let the extra water run down the dams' spillways, bypassing the power-producing turbines. But that turns out to pose an environmental problem. Water that goes down the spillway gets frothy, and the excess air bubbles can kill salmon and steelheads, an endangered species in the upper Columbia River. So the BPA solved the problem by running all the water through the turbines, making power it didn't need, Mr. Milstein said.

But beginning around June 8, the rainwater arrived along with an excess of wind power coming from the same storms that brought the rain. Pushing all the power it could to its neighbors, BPA had to turn to the only nuclear plant in the neighborhood, the Columbia Generating Station, and ask the operators to scale back.

This is unusual: nuclear plants are designed to run at 100 percent power and have trouble changing their power settings. "It turns out 100 percent till you shut it down to refuel," said Rochelle Olson, a spokeswoman for the plant.

Columbia is accustomed to reducing power to 85 percent and sometimes 60 percent. In the following days, however, BPA asked the plant operators to go down to just 22 percent. "This year was extraordinary because it all came so heavy and so fast," Mr. Milstein said.

Nuclear operators dislike running at partial power for several reasons. In some cases it makes for less efficient use of the uranium fuel. And one way that they justify their high construction cost is by running as many hours of the year as possible. Some new plant designs are intended to run at partial power at times, but existing plants are not made that way.

The problem seems poised to get worse. BPA is rapidly adding wind power, mostly to meet the renewable portfolio standard in California. But when more spring wind combines with spring runoff, there will be surpluses that cannot be exported over existing power lines, industry officials say.

The BPA is preparing a major report on the event, which lasted until June 13, and will look for solutions. "Maybe transmission lines are where to go next, or the smart grid," Ms. Olson said.

In fact, Mr. Milstein said discussions were under way about beefing up connections to California. Another possibility is asking thousands of homeowners to let their electric companies take control of their electric water heaters, he added. When surplus power exists, the water heaters could heat the water hotter than normal, in effect turning them into storage batteries.

But for now, he said, "we happen to have all these renewable resources, and sometimes they don't work exactly like we'd want them to."