Columbia Generating Station ENW

Columbia Generating Station.

When the Bonneville Power Administration asked Energy Northwest on May 19 to reduce the output of its 1,207 MW Columbia Generating Station in southeastern Washington to 65 percent, and to return the nuclear plant to full output on May 25, it was the first time this had happened under a new flexibility agreement signed in July 2019.

BPA markets all the power from CGS, the region's third-largest energy producer behind Grand Coulee and Chief Joseph dams.

The two parties have worked together for years to reduce nuclear generation during times of oversupply in Bonneville's balancing authority area, when heavy streamflows increase hydro generation and weather swells wind generation, typically starting in spring.

When supply exceeds demand in the BAA, and hydropower-reducing spill over dams is at the safe limit for migrating fish, Bonneville turns to its Oversupply Management Protocol (OMP) for further reductions, because too much power is bad for grid reliability. Under the protocol, BPA directs other generators to shut down, and compensates them for associated costs.

Under the old agreement, up to several days' notice was required to decrease CGS power generation, and then even more time was needed to return it to full output. Now, CGS in some cases can decrease generation within two hours' notice, Bonneville said.

With the CGS agreement, there are more options for adjusting the plant's power generation. The deal improves communications between Bonneville and ENW and "outlines faster load-shaping capability, plant power levels, recovery times and risks," BPA said in a news release.

"Increased flexibility of CGS's output during times of high spring runoff is an asset to the region," Cherie Sonoda, a BPA supervisory nuclear engineer who works at the plant, said in the release. "With lots of research, planning and safety in mind, we worked together to make this happen, and I think it will be a good thing economically for BPA and the region we serve."

"Since BPA receives all of the energy CGS produces, this new agreement and flexibility in CGS operations is a real benefit for the agency," Pam Van Calcar, manager of BPA power generation scheduling, said in the release.

She added that there are now more options available for coordinating the timing and duration of powering down, "making it a little less likely we'll have to compensate other generators to shut down."

In 2019, the OMP wasn't used at all because BPA was able to match generation with demand. It was used 24 times in 2018 at a cost of $4.9 million and 39 times in 2017 at a cost of $2.2 million.

In the recent CGS down-power, which took place over the Memorial Day weekend, the oversupply protocol wasn't invoked.