Comparison of concepts for high-altitude wind energy generation with ground based generator

While the wind energy of the atmosphere increases significantly with increasing altitude, no electrical power is currently generated from wind at high altitudes. This paper presents and compares several concepts for wind energy exploitation from high altitudes winds. The comparison in this paper is limited to concepts that have the generator located on the ground. The concepts make use of lifting bodies, called wings. The wings are attached to a tether that drives the generator while the wings are pulled up by the wind. Such systems enable large single-unit outputs because the size of the wings connected to the tether can be much larger than the blades of conventional windmills. From several concepts, the most promising concepts were simulated using real historical high altitude wind data from the Royal Netherlands Meteorological Institute. Because of the more constant wind speeds at high altitudes, around 70% of the installed power can be actually generated on average, which is higher than the results for conventional windmills. Because of the high altitude at which the concepts operate, even sites that are not cost effective for conventional windmills may still be used for high altitude wind energy production. Finally, it is shown that the moving mass (the wings and the tether) of a 5MW version of the most promising concept can be significantly lower than the mass of the blades of a 5 MW conventional windmill.