The federal agency operates 75% of the region's transmission grid. In February it proposed to curtail wind power output by forcing the shutdown of some wind turbines. The move, it claimed, would ensure there is no repeat of last June's system-wide balancing problems, which were caused by an over-generation of power due to the excessive snowmelt and strong seasonal winds traditionally experienced in the spring. Snowmelt produces heavy water flow into BPA's hydropower system. When combined with output from wind farms in the Columbia River Gorge area, over-generation occurs.
BPA's system currently accommodates output from over 3.5GW of wind power, up 700MW on last year. Within the next few years, that wind total is set to double, so the problem of over-generation is set to increase significantly. BPA says curtailing wind is the best way to avoid problems. Critics note that it can also opt to spill excess water over its dams, bypassing the hydro-generators instead.
Curtailment impacts wind operators more than traditional power generators because a significant part of the income generated from a wind farm comes from tax and renewable-energy credits. These credits represent actual generation, so the less output from a wind farm, the fewer credits it accrues.
Although it has now backed down on the curtailment plan, BPA contends that spilling excess water over its dams to bypass hydro-generators is bad for the river environment. Excessive spillage raises nitrogen levels in water, putting salmon and other fish in danger, it argues. Rachel Shimshak, director of regional advocacy Renewable Northwest Project, refutes this.
"There is no evidence," she says, adding that some research shows excess water over dams is actually good for fish. "This is merely an economic thing for Bonneville," she says. "It wants to preserve the market for itself."
BPA spokesman Doug Johnson says the agency is now devising new contingency plans. "We need to figure out the best way to work through the situation. We are going to work on this from a multitude of angles." He adds: "We're hoping we'll have a few warm fronts that don't melt off too much snow until we get through the fish-passage season and that the water comes down in July and August when you don't necessarily have as much wind."