BPA files changes to curtailment plan

UNITED STATES: Bonneville Power Administration (BPA), grid operator for the majority of the Pacific Northwest region of the US, yesterday filed a plan to change the way it curtails wind farms' output at times of over-generation by the region's hydroelectric dams.

The Dalles dam on the Columbia River was among the hydropower sources affected

The plan, submitted to the Federal Energy Regulatory Commission (FERC), proposes that BPA covers revenue losses suffered by wind farm owners as a result of curtailments. It also states that wind curtailment will become an action of last resort, taking place only after all possible reductions have been made to the output of both hydroelectric and thermal power plants.

The move follows a legal row between BPA and wind farm owners - including Iberdrola, NextEra Energy Resources, and EDP Renovaveis subsidiary Horizon Wind Energy – over BPA’s so-called "environmental dispatch" policy.

Under this policy BPA curtails wind turbines during the snowmelt season, when hydroelectric dams often produce power that far exceeds demand. BPA insists it can dump only a limited amount of water over the dams because excess spillage creates dangerous levels of nitrogen that are harmful to salmon and other fish species.

The plan, dubbed the Oversupply Management Protocol, means that at times of oversupply the BPA would first work with the US Army Corps of Engineers and Bureau of Reclamation to manage federal hydroelectric generation and spill water up to dissolved gas limits.
BPA would then offer low-cost or free hydropower to replace the output of thermal and other power plants, with the expectation that many would voluntarily reduce their generation to save fuel costs.

If electricity supply still exceeds demand, BPA would then reduce the output of remaining generation within its system, including wind energy, in order of least cost. BPA would compensate the affected generation for lost revenues, including renewable energy credits and production tax credits.
The protocol would be part of  BPA’s transmission tariff and BPA intends to file the broader tariff with FERC later this month.