Wind energy currently suffers from a lack of competitiveness compared with non-renewable energy production techniques. From an engineering point of view, the power output of a wind turbine increases linearly with the swept area of the rotor and cubically with the wind speed. As the typical size of wind turbines is increasing, a large amount of structural materials is needed to withstand the high mechanical stresses induced by heavy rotors that are placed on tower-based foundations. The idea behind airborne wind energy (AWE) is to reduce the material use (and hence the cost) of today's wind energy by either freely flying the wind energy system in the air or tethering it to the ground. Because AWE systems do not use a fixed tower, they can further operate at different altitudes depending on the wind conditions. It also becomes feasible to harness winds at moderate- or high- altitudes (e.g. from 150 metres above the ground), where winds are stronger and steadier than at low altitudes. For these reasons, airborne wind energy could massively enlarge the contribution of wind power to the global energy market.
A promising approach for generating airborne wind energy is to fly an inflatable wing, which is tethered to a ground station. Delft University of Technology is developing a prototype of such kite power system, in which the traction force of the kite drives a ground-based electricity generator.