The Impacts of Wind Speed Trends and Long-term Variability in Relation to Hydroelectric Reservoir Inflows on Wind Power in the Pacific Northwest

The use of wind power is growing rapidly in the Pacific Northwest (PNW) due to environmental concerns, decreasing costs, strong wind speeds, and the desire to minimize the impacts of streamflow variability on electricity prices and system flexibility through diversification. In hydroelectric dominated systems, like the PNW, the benefits of wind power can be maximized by accounting for the relationship between long term variability in wind speeds and reservoir inflows. Clean energy policies in British Columbia (BC) make the benefits of increased wind power generation during low streamflow periods particularly large by preventing the overbuilding of marginal hydroelectric projects to fulfill its legislated self-sufficiency requirements. The goal of this work was to help maximize the value of wind power by quantifying the long-term relationships between wind speed and streamflow behavior in BC. Wind speed data from the North American Regional Reanalysis (NARR) and cumulative usable inflows (CUI) from BC Hydro were used to analyze 10m wind speed and wind density (WD) trends, WD-CUI correlations, and WD anomalies during low and high inflow periods in the PNW (40°N to 65°N, 110°W to 135°W) from 1979-2010. Statistically significant positive wind speed and density trends were found for most of the PNW, with the largest increases along the Pacific Coast. WD-CUI correlations were weakly positive for most regions, with the highest values along the US coast (r ~0.55), generally weaker correlations to the north, and negative correlations (r ~ -0.25) along BC’s North Coast. When considering seasonal relationships, the spring freshet was coincident with lower WD anomalies west of the Rocky Mountains and higher WDs to the east. A similar but opposite pattern was observed for low inflow winter months. When considering interannual variability, the lowest inflow years experienced positive WD anomalies (up to 40% increases) for the North Coast. In the highest inflow years, positive WD anomalies were widespread in the US and in smaller patches of central BC. By accounting for regional and temporal differences in the relationship between wind (WD) and streamflow (CUI) behaviour during wind farm site selection, the benefits of energy diversification can be maximized.