Humidity Variation in the Shadow of a Large Wind Farm: an LES Investigation

Numerous studies have shown that wind turbine wakes within a large wind farm bring about changes to both the dynamic and thermal properties of the atmospheric boundary layer (ABL). Previously, we compared humidity field measurements in the near-wake region of a large wind turbine with LES results of a single turbine in a stable ABL and found good agreement. The effect of the compounding wakes within a large wind farm on the relative humidity was also investigated using LES. The relative humidity was found to decrease below and increase above the turbine hub height, with the downstream turbines magnifying the effect within the wind farm. This study will investigate how the areas of relative humidity variation, that were observed in the near-wake, develop downstream of a large wind farm. To this end, an LES study of a 7x4 turbine array operating in a stable ABL is carried out. Two wind farm layouts are considered: aligned and staggered. Vertical, streamwise and lateral profiles of the change in relative humidity between upstream and downstream of the turbine array will be presented and discussed.