A study of the impact of very large wind farms on regional weather using the WRF model in high resolution
<p>The Weather Research and Forecasting (WRF) model&#160;fitted&#160;with the Fitch et al. (2012) scheme&#160;for parameterization of the effect of wind energy extraction&#160;is used to&#160;study the effects of&#160;very large wind farms&#160;on regional weather. Two&#160;real data&#160;cases have been run in a high spatial resolution&#160;(grid size 500 m).&#160;Both&#160;cases&#160;are characterized by&#160;a convective&#160;westerly flow. The&#160;inner&#160;model&#160;domain covers the North Sea and Denmark. The largest windfarm&#160;consists of&#160;200.000 wind turbines&#160;each&#160;with a capacity of&#160;8MW. The model is run for up to 12 hours with&#160;and without&#160;the&#160;wind farm. The impact on the regional weather&#160;of&#160;these very large wind farms are studied and presented. Furthermore, the&#160;effect&#160;of horizontal spacing between wind turbines is investigated. Significant impact on the regional weather from the very large wind farms was found. Horizontal wind speed changes occur up to 3500m above the surface. The precipitation pattern is greatly affected by the very large wind farms due to the enhanced mixing in the boundary layer. Increased precipitation occurs&#160;at the front?&#160;within the wind farm, thus leaving the airmass relatively dry&#160;downstream&#160;when it reaches the&#160;Danish coast, resulting in a decrease in precipitation here compared to the control run. The formation of a small low level jet is found above the very large wind farm. Furthermore, wake effects from individual wind turbines decrease the total power production. The wind speed in the real data cases are well above the speed of maximum power production of the wind turbines. Yet most of the 200.000 wind turbines are producing only 1MW due the wake effects. A simulation run with a wind farm of 50.000 8MW wind turbines was also run. This windfarm covers the same area as the previous one, but horizontal distance between wind turbines are 1000m instead of 500m. This configuration was found to produce a similar amount of power as the 200.000 configuration. However, the atmospheric impact on regional weather is smaller but&#160;still large with 50.000 wind turbines.</p>