On the energy requirements of UAVs used for blade inspection in offshore wind farms

Abstract

Offshore wind energy is being seen as a major energy player as the quest for clean renewable energy solutions intensifies. Wind turbines operating at sea are subjected to a harsh and unforgiving marine environment that calls for timely inspections and maintenance in order to maintain high levels of availability. Inspections at height and especially at sea are inherently time-consuming, expensive and fraught with risks, so the automation of such procedures will benefit the industry at all levels. Unmanned Aerial Vehicles (UAVs) are finding niche applications as a remote sensing tool in various sectors, one of which is wind turbine inspection. This paper investigates the onboard energy requirements and operational flight duration of a drone used for offshore wind turbine inspections subject to aspects such as wind turbine size and site wind conditions. The energy requirements of the UAV are numerically modelled using a single-wind turbine blade inspection routine as a basis. Flight path distance is inherently linked to wind turbine blade length and, based on the need for four passes per blade during an inspection, this property featured prominently on the UAV's performance. The research then moved on to investigate UAV energy requirements for multiple-wind turbine arrays with factors such as wind speed and direction, inter-turbine spacing and array layout and rotor wakes being considered. This part of the study utilised the numerical model mentioned earlier and the WindPRO software package. The undisturbed wind speed was declared as that characteristic having the highest influence on energy consumption and flight duration. Wind direction, wind turbine rotor wake and inter-turbine downwind spacing were the other forcing factors considered, with the significance of their impacts in the same order respectively. The results of this study identify the effects of the various parameters on UAV energy requirements and inspection flight duration as a means of enabling better planning and optimisation of offshore wind turbine blade inspection using drones.