Nocturnal jets over wind farms in complex terrain

Abstract

Recent wind-energy field experiments have enhanced our understanding of stratified flows over topography by observing the flow of nocturnal jets over complex terrains in the natural environment. There is a research gap on how the intricacies of such flows could impact wind-energy production. In this study, we investigated how nocturnal jets influence the performance of two operational wind farms built over complex terrain, by combining operational data and numerical mesoscale simulations. The wind farms are similarly designed as two rows of turbines roughly aligned in the crosswind direction and separated by microscale distances. Front and back rows are located, respectively, near the leading edge and the lee of a microscale plateau with a downstream valley. Nocturnal jets occur close to midnight as the cold fast-moving air of a gravity current rushes inland after the evening transition. They produce a deeper stably-stratified layer and strong downslope winds and in some cases can cause turbines in the back row to produce twice as much power as those in the front row.