Power Transmission for Rotary Airborne Wind Energy Systems

Rotary systems are a branch of Airborne Wind Energy (AWE) that utilise multiple wings networked together. In several designs these networked wings form rotors. To maintain the advantage of housing the generator on the ground several rotary AWE designs transmit rotational power using a tensile rotary power transmission. This consists of a series of tensioned tethers held apart by rigid rings or rods. One AWE system that utilises this method is the Daisy Kite developed by Windswept and Interesting Ltd. To analyse the ability of tensile rotary power transmission system for power transfer, a basic steady state analysis of the Daisy Kite has been completed. Three key factors impact on the system’s ability to transmit power these are: the tether tension, diameter of the transmission system and the spacing between the rigid components. In the steady state analysis the efficiency of the transmission has also been found. The average transmissions efficiency was calculated to be 93.2% for one of the field tests conducted on 27th June 2017. It is noted that this transmission efficiency can vary greatly depending on the operating conditions. The steady state analysis can be used to design the geometry with the aim of minimising the weight of the transmission system while maximising its efficiency. This analysis could be adapted to look at other rotary AWE systems that use tensile rotary power transmission