Enhanced kinetic energy entrainment in wind farm wakes

Abstract

Wake effects in wind farms are a major source of power production losses and fatigue loads on the rotors. It has been demonstrated that in large wind farms the only source of kinetic energy to balance the energy extracted by the turbines is the vertical transport of the free-stream flow kinetic energy from above the wind turbine canopy. This chapter explores the possibility to enhance this transport process by introducing kites in steady flight within a small wind turbine array. In a first step, an array of four wind turbines, aligned with the streamwise velocity component, is simulated within a large eddy simulation framework. The turbines are placed in a pre-generated turbulent atmospheric boundary layer and modeled as actuator disks with both axial and tangential inductions, to account for the wake rotation. In a second step an identical turbine configuration with interspersed kites is investigated. The kites are modeled as body forces on the flow, equal in magnitude and opposite in direction to the vector sum of the lift and drag forces acting on the kite surfaces. A qualitative comparison of the mean flow statistics, before and after the introduction of the kites is presented.