Impacts of a cluster of wind farms on wind resource availability and wind power production over complex terrain

This study targets the evaluation of the impacts that a cluster of wind farms, already in operation, produces on wind resource availability by using the Weather Research and Forecasting (WRF) mesoscale model. The wind turbines are represented as an elevated momentum sink on the mean flow and a source of turbulent kinetic energy. The default wind turbine parameterization in WRF is corrected to avoid some instability effects found when using the parameterization on onshore area. The experiment set-up consists of two WRF simulations of the wind field with and without representing the effects of the wind turbines. Both simulations span a period of one year using a spatial resolution of 1 km over the target region in order to accurately represent the complexity of the terrain. Results indicate that the presence of the wind farms leads to wind speed deficit values up to 0.7 m/s at the average hub height. The largest impacts are experienced under stable atmospheric conditions, when wakes are more intense and also propagate at larger distances. The relative wind power deficits associated with nearby wind farms can be as large as 23 %. Wind farm wakes therefore have a non-negligible impact on the production of electricity and should be taken into account in the design of a new wind farm in areas with high density of wind turbines.