Saturated with too much energy from wind and water, the Bonneville Power Administration, a federal agency based in the Pacific Northwest, has been forced to look for outside help. For the moment its problems represent an extreme, but experts predict that other systems will find themselves in the same pickle as utilities build more wind machines in an effort to reach state-mandated quotas for renewable energy.
Bonneville, which issued a report this month on its rough patch, went through a period in June where it literally had to give energy away and induce neighboring utilities to shut down their fossil-fuel powered plants. The problem was that its own territory was struck by unexpected storms that filled its dams with water.
Other systems might have released the water and bypassed the wind turbines, but for Bonneville that causes environmental damage. Water that goes over a spillway as opposed to through a turbine picks up bubbles of nitrogen gas from the atmosphere. When baby salmon absorb the bubbles, they experience something resembling the bends in a human diver.
The same storms also brought wind. Bonneville has added 5,000 megawatts of wind power in the last few years, and it is mostly concentrated in the Columbia River Gorge in what is known as the “wind ghetto.” As a result, at any given moment, almost all of the wind machines in Bonneville’s territory are either running or not running. In June, they were running.
Normally hydro and wind are a good pairing because hydro plants can adjust their output almost instantly to compensate for a variation in winds. But if all the water has to go through the turbines, as was the case in June, the hydro operator loses the ability to cut back when there is a sudden surge in wind.
The system got so crowded that Bonneville took the highly unusual step of telling a nuclear power plant in its territory to cut output to 18 percent. Nuclear power plants are designed to run at 100 percent.
The next step, which it did not quite reach, would have been to tell the wind producers to “spill” wind, adjusting their blades so they produced no power. That would have denied the system electricity that has no operating cost and made it harder to meet renewable energy quotas.
To avoid being squeezed again, Bonneville has begun a pilot project with Iberdrola Renewables and Constellation Energy. About 1,100 megawatts of wind in Bonneville’s territory owned by Iberdrola will be balanced by a coal-fired plant in Centralia, Wash.; gas-fired power plants in Oregon; and hydro resources owned by other operators.
“We’re going to get to a point where we’re starting to choke on too much wind,’’ said James J. Thompson, vice president of Constellation. The solution for now, he said, is to dilute the variability of wind by spreading it over a bigger system.
The division of Constellation that does the work, formerly owned by Duke Energy North America, installs controls on remote generators that can receive information from a central control room in Houston every four seconds and increase or decrease generation. But usually what it is doing is balancing conventional generators against varying demand.
Mr. Thompson said that his company would use about 600 megawatts of generators to balance the 1,100 megawatts of wind, although on any given day, some of that 600 megawatts would not be available. Still, the amount on hand will be more than adequate to make up for cases in which the wind blows harder or more gently than predicted, requiring a coal- or gas-fired plant to gear up or trim its output.
In the longer term, the ability to compensate for varying wind output will require more power lines, experts say. And government studies show that with more wind installed in diverse locations, wind generation can offset itself, with machines in some locations running hard while others are becalmed, making for a steadier average.
For now, though, Bonneville Power Administration is outsourcing its problem to an operator with access to a broader portfolio of generators.
“Bonneville Power Administration hydro resources are stretching to their limits,’’ said Doug Johnson, a spokesman for the agency. “In the interest of getting as much wind on the system as we can, it’s important to find other resources.”
One issue is the proper size of a “balancing area,” a geographic subdivision of the power grid in which demand and supply are supposed to balance out, taking into account planned imports and exports.
Donald N. Furman, a senior vice president for external affairs for Iberdrola, said that bigger balancing areas would be part of a longer-term solution. For now, the deal with Constellation and Bonneville amounts to a virtual balancing area, he said.
The cost of integrating wind into an electric system was modest until new generating capacity was needed to react quickly to the variability of wind. The pilot project, he said, puts off the need for such construction.
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