The SwissKitePower project is a multidisciplinary research and development effort aimed at creating a totally new device which can harness wind energy at high altitudes. The winds at altitude are stronger and more consistent than those at the ground and represent an enormous potential source of renewable energy.
During the course of the project innovative new kites will be developed at Empa which can efficiently convert the kinetic energy of the wind into mechanical power and eventually wholesale electricity.
In order to test these new kite designs in the real world, the researchers at the FHNW have developed a mobile testing platform. This kite test bench will also allow for the development and testing of new estimator and controller designs.
The control algorithms are developed at the Automatic Control Laboratories at both ETH and EPFL, aimed at keeping the kite flying autonomously in the most challenging wind conditions. Industrial partner Alstom will analyse what role kite power could play in shaping the future of the energy industry.
"In our technology only the wing and the tether are in the air, while the generator and other heavy and vulnerable components such as the power electronics are placed on the ground. This allows to have the lightest possible wing in the air, maximizing safety while allowing for easy access to electrical and mechanical systems during operation and maintenance. Electrical energy is produced by transforming the aerodynamic lift force of the wing into tension in the tether and eventually rotational motion of the winch. A closed-loop process is achieved by flying so called pumping cycles as shown above. In the power phase, the kite flies crosswind generating high loads. The tether pulls on the drum which starts to rotate. The kite rises and the generator connected to the drum produces electrical power. Having reached a threshold altitude, the kite is flown out of the wind and the retraction phase starts. The kite is reeled in to a lower threshold altitude from where the power phase starts again".
IDTechEx notes that this is portrayed as a rather dated approach with relatively low altitudes, double tether and no way of rising into position through still air, though it does follow the weak trends to fixed wings and the corkscrew rather than yoyo figure of eight trajectory (only a minority so far). Twingtec also of Switzerland seems to have the more modern approach. See the IDTechEx report, Airborne Wind Energy AWE 2017-2027.
Top image: SwissKitePower