For the third consecutive day, the Bonneville Power Administration (BPA) curtailed wind generators because abundant hydro generation left too little room on the agency’s transmission system.
Following curtailments in the early morning hours of April 29 and 30, BPA again curtailed wind generation after 10 p.m. PDT on the evening of April 30. That curtailment extended into the early morning hours of May 1.
The actions have left area wind operators upset.
“BPA is using these very same practices that federal regulators declared to be in violation of the law just six months ago,” a spokesperson for Iberdrola Renewables, a major wind-power developer, told TransmissionHub on May 1.
“Bonneville has not provided a clear explanation of why the curtailments were ordered,” the spokesperson continued. “We are concerned that BPA has again abrogated transmission contracts in order to serve its economic self-interest.”
However, BPA officials confirm the agency does not receive revenue when replacing renewable energy with federal hydropower.
BPA officials say the curtailments were based on the capacity of the transmission system, limits on the amount of water it can send over the spillways of dams on the Columbia River, and the generation limits of other resources.
Prior to ordering Northwest wind generators to curtail production, the agency issued “min-gen” alerts and ordered the area’s thermal generators to reduce their output to minimum generation levels.
“We did go to thermal generators first,” a BPA spokesperson told TransmissionHub, but on May 1, thermal generators “were already at their minimum operating levels, and for their reliability and production purposes [could not be reduced farther]. That’s when we moved on to [shut down] wind generation.”
When a thermal generation unit is shut down completely, a specified period of time must elapse before that unit can be restarted, and that could have an adverse effect on reliability, the spokesperson confirmed.
The agency has taken steps to increase the amount of available transfer capacity on its transmission system. The Columbia nuclear generating station at Hanford, Wash., reduced its output to 85% of rated capacity on the afternoon of April 30 at BPA’s request, and will maintain that level until Monday, May 7, a spokesperson for plant operator Energy Northwest told TransmissionHub on May 1.
With a rated capacity of 1,150 MW, a 15% reduction cut the plant’s output by approximately 170 MW, but that reduction was apparently not enough to forestall further curtailments.
The May 1 curtailment totaled 8,500 MWh. The curtailments during the early morning hours of April 29 and 30 were 5,118 MWh and 4,704 MWh, respectively.
BPA filed a protocol with FERC on March 6 that is intended to help reimburse wind generators for those lost credits, but that protocol has been widely criticized by area wind producers as not going far enough.
“If this were a [reliability or] an environmental issue, if this were a fish issue, we would have a different take” on curtailing production, the Iberdola spokesperson said, “but this is purely for their economic interest.”
The agency spokesperson said, “We’re estimating it will cost us about $12m to reimburse wind producers for the production curtailed during the 2012 season, but our total exposure could be as high as $50m.”