Wind Yield Assessment of Airborne Wind Energy

Airborne Wind Energy (AWE) is a novel way of harnessing the wind. The potential benefits include higher yield due to the increased wind and its more persistent nature at higher altitudes (100m-1000m). Also, the overall cost of the system is reduced since large, steel devices are not required. This results in a potential step down in the cost of energy for offshore wind systems. AWE converters work in one of two methods. The drag devices have generators on board, and the tether transmits the power; lift devices reel the tether in and out of a ground based generator. One problem the AWE sector faces is its understanding and evaluation of the available resource at such high altitudes. There is evidence of low level coastal jetting and reverse shear at heights as low as 100m. Since met masts normally operate at heights up to 80m, non-typical wind data sets are required for an accurate assessment of the wind speeds. Standard shear profiles and models are only valid to a height of around 100m, but above this level the atmosphere is in a transitional zone between the upper and lower surface boundary layers. The wind speed isn’t only affected by frictional shear but also by the bulk properties of the atmosphere. This can result in errors in both the energy yield assessment and loading calculations for the offshore wind sector. Current yield assessment methodologies are inadequate for large offshore and airborne wind. The industry accepted method of extrapolating wind speed data to hub height by using standard shear laws and roughness lengths will result in large inaccuracies in yield estimations. For this reason, a novel method for yield analysis has been developed for unconventional wind. This project aims to evaluate the viability of this method of yield analysis.