As winds picked up May 12, the Bonneville Power Administration warned wind farms at 6:29 p.m. to prepare to shut down the wind turbines in four minutes. The turbines were generating about 600 megawatts more power than expected. The power system could not absorb any more.
For the first time, though, wind farms used a new mechanism BPA designed with wind operators and utilities to escape such a shutdown. They sold 330 megawatts of the unexpected energy for the following half hour. That simple step delivered more wind power to regional customers, earned them more revenue and quickly eased pressure on the power system.
BPA canceled its warning. The turbines kept spinning.
Northwest wind producers have sold rapidly increasing amounts of power on such a short-term basis since BPA introduced the option in December. Half hour transactions in April hit their high point so far of 4,424 megawatt half-hours or the equivalent of about four nuclear power plants worth of energy for a half-hour.
The May example was the first time the new program prevented the shutdown of wind turbines when the hydroelectric system ran out of capacity to offset changes in wind energy. The program has proved so successful BPA is now extending it indefinitely and looking for ways to apply it in other situations, such as when wind turbines produce considerably less energy than scheduled.
Its success illustrates how the region’s power system is swiftly evolving to handle the ups and downs in wind and the energy it produces.
"Wind generates power in a different way than the system was used to, so we’re making sure the power system changes with the times,” said Cathy Ehli, vice president of Transmission Marketing and Sales.
Traditional power plants pro- vided such steady output that utilities long bought and sold electricity on an hourly basis. But wind is changing that, because the energy it produces can vary sharply within mere minutes. So BPA in December expanded staff and adjusted operations to support power sales as frequently as every half-hour. The change lets the 27 wind energy projects connected to BPA’s grid adjust their power sales more often to better match shifts in wind. They can sell extra wind power generated by unexpected gusts while also relieving demands on hydroelectric dams to make up for sudden changes in wind generation.
What happened May 12:
6:20 PM Wind gusts push wind energy generation 600 MW beyond what wind plants had scheduled to flow through BPA lines. BPA dials back generation from hydroelectric dams to accommodate the power.
6:25 PM BPA begins adjustments after wind farms sell 330 MW of the unexpected wind energy for the upcoming half-hour in four short-term transactions.
6:26 PM BPA nears limit of how far it can dial back hydroelectric generation without jeopardizing the stability of the power gird or protections for salmon. BPA warns that 85 percent of such reserve capacity is exhausted.
6:29 PM BPA warns that 90 percent of reserve capacity is exhausted. Notifies wind plants to shut down turbines in four minutes.
6:30 PM Half-hour power sales take effect, reducing pressure on reserves.
6:31 PM BPA cancels warning.