Airborne Wind Energy: It’s All Platypuses Instead Of Cheetahs

Kite-based wind generation was first proposed in the 1940s, the seminal power potential paper was published in 1980 and it was first demonstrated in 1986. So why isn’t there a single production system or even an a quarter-scale production prototype in existence today? University of Delft kite generation device in front of wind turbines Each of the combinations of design choices inherent in trying to capture wind energy with a tethered vehicle involves a different set of compromises and a different set of technical challenges. Each of these paths has been explored one or more times, and the results are not encouraging. Technical, safety, siting and regulatory challenges abound, and it’s unclear if they can all be solved. This material has been garnered from publicly available documentation of the products, from the 600-page Springer airborne wind energy book published recently, the seminal Lloyd white paper from 1980, extensive interactions with airborne wind energy experts around earlier iterations of this material and material from organizations like the NREL. Very intelligent people have made these choices and are facing these challenges today. So what are the choices?

1. Soft kite, hard wing or lighter-than-air
2. Generation on the ground or generation in the air
3. Crosswind flying or (relatively) static flying
4. Single tether vs multiple tethers
5. High-altitude or low-altitude

Rotorcraft approaches are included in the hard wing option above. The purely blue-sky, free-flying, untethered generation concepts are excluded entirely from this structure;  they have radically different weaknesses and few apparent strengths. Finally, some of these choices are on a continuum, not either-or choices, so a subset of compromises have larger impacts. As one example TwingTec uses an inflatable rigid beam to give structure to a rigid wing comprised of very soft materials. As another, many of the pure soft wings have inflatable spars adapted from kitesurfing, or directly use kitesurfing kites. (Note that these semi-rigid, inflatable technologies have their own compromises as they will require pressure sensors, pumps and in-airpower to maintain the correct pressures.) Ten representative technologies and their choices are included, giving a reasonable cross-section of the space. None of these technologies are viable today when compared to conventional modern ground-based wind turbines or other forms of utility-scale generation, and many of these combinations may never be viable.

http://cleantechnica.com/2014/03/03/airborne-wind-energy-platypuses-instead-cheetahs/