Shroud design criteria for a lighter than air wind energy system

Airborne Wind Energy (AWE) is a novel form of wind energy research looking to utilize the greater wind resource at higher altitudes. This paper focuses on a lighter than air system developed by Altaeros Energies. Using two force ratios the relationship between the buoyancy and aerodynamic force is related to the geometric parameters of the shroud. A dependence on a so-called area ratio is also shown relating the shrouds area to the shrouds throat area used as a reference for aerodynamic calculations. This ratio was varied in simulation and was found to have a marked effect on the driving forces over the shroud. Finally, an investigation into whether helium or hydrogen should be used for this application is shown. It is found that the design of the shroud has to be aerodynamically optimized for successful operation and that the choice of which gas to employ becomes one of safety rather than enhanced performance.