4.2 Mountain Waves Impact Wind Power Generation

Monday, 13 January 2020: 3:15 PM
256 (Boston Convention and Exhibition Center)
Caroline Draxl, National Renewable Energy Laboratory, Golden, CO; and L. K. Berg, D. Chand, J. Lundquist, Y. Pichugina, J. Sharp, G. Wedam, J. Wilczak, and R. Worsnop

Large mountains can modify the weather downstream of the terrain. In particular, when stably stratified air ascends a mountain barrier, buoyance perturbations develop. These perturbations can trigger mountain waves downstream of the mountains, which can reach deep into the atmospheric boundary layer where wind turbines operate. Several such cases of mountain waves occurred during the Second Wind Forecast Improvement Project (WFIP2) in the Columbia River Gorge in western North America. Signals from the mountain waves appear in boundary-layer sodar and lidar observations, as well as in nacelle wind speeds and power observations from wind farms. Our WRF model simulations also produce mountain waves. Even small oscillations in wind speed due to mountain waves can induce oscillations between full rated power of a wind farm and half of the power output, depending on the position of the mountain wave’s crests and troughs. This talk will address how mountain waves form in the complex terrain of the Columbia River Gorge, subsequently affect wind energy production, and impact aspects of operational forecasting, wind farm layout, and integration of power into the electrical grid.
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