Wednesday, April 5, 2005
The role of climate forecasts in western U.S. power planning
co-authors: Nathalie Voisin, L. Phil Graham, David W. Pierce, Tim P. Barnett, and Dennis P. Lettenmaier
Climate variability affects electrical power supply and consumption in the Western U.S. in ways that are increasingly predictable. Seasonal and interannual climate along the U.S. west coast often varies in such a way that California (CA) and the Pacific Northwest (PNW) are often out of phase. For instance, warm and dry winters in the PNW (and hence reduced hydropower production) frequently occur at the same time as cool and wet conditions in southern CA. These conditions can now be forecast with some skill as much as a year in advance. Using a series of models that simulate river flows, regional electrical demands, and reservoir operations in the Columbia River and the Sacramento-San Joaquin basins for the period 1917-2002 we examine the potential for alternative operation of the existing power intertie between the PNW and CA (capacity ~7900 MW) that might exploit out of phase climate behavior between the PNW and CA. Our results show that hydropower production and electricity demands are typically out of phase seasonally, but tend to covary on an annual basis, in response to ENSO climate signals. While demand variations in the two regions play a minor role, potential hydropower transfers between the two regions are shown to be primarily driven by surplus energy in the PNW in spring, which is well correlated to ENSO and PDO. The probability distributions of these transfers are therefore predictable with long lead times. Such electricity transfers are estimated to have potential average annual benefits to CA and the PNW of $159 million and $95 million respectively. By exploiting the long-range predictability of spring surplus hydropower production in the PNW, increased electricity transfers in late summer could be facilitated in some years where surplus electricity is likely with increased economic benefits to the PNW and reduced risks of capacity related failures in CA. A simple market-based approach could be used to facilitate these transfers when spring surplus energy resources are likely in the PNW.
Alan Hamlet is a research scientist with the CIG and the UW Department of Civil & Environmental Engineering, where he is also a doctoral candidate.