Review of Peaking Power Needs in the Pacific Northwest

The study of the Libby Reregulating Project addressed the effect reduced river fluctuations would have on power generation and the sustained peaking adjustment used for the first time in the West Group utilities forecast for 1979 to 1999. The Federal Columbia River Power System consists of a series of 30 dams, each of which has one or more installed hydroelectric generators. Each year the Pacific Northwest Utilities Conference Committee (PNUCC) estimates the region's need for additional power resources. The West Group Forecast summarizes regional loads and resources for 11 future years, while the Long-Range Projection covers a 20-year planning period and presents a more detailed analysis of loads and resources for each major utility in the region.

The maximum instantaneous electric output from the Columbia System is dependent on the height of the water behind each dam at a particular time. The system cannot be counted on to continuously operate at this instantaneous output level. In its 1979 forecast the Bonneville Power Administration (BPA) substituted a sustained peaking adjustment for the realization factor on the federal hydrosystem. The sustained peaking adjustment reduces the federal hydrosystem's projected capacity to the highest average level which it can maintain for 10 hours a day, 5 days per week. BPA determined this adjustment through computer simulation, assuming critical water conditions, no significant spillage, and compliance with all nonpower constraints. BPA sustained peaking adjustment is a valid refinement for measuring the federal hydrosystem's capabilities. Several nortwest utilities have recognized the need to apply such adjustments to their hydrosystems. However, uncertainty exists as to what time period best represents a sustained regional peaking need. Regional power planners should not hurry their judgments on constructing new peaking facilities because present forecasting methodologies are questionable and adequate time should be taken to thoroughly compare the costs and benefits of alternative means of meeting peak power needs.