Closing the Gap

(1)

Testing the TwingTec wing in the Alps (23 November 2012). 26

(2)

TwingTec’s Twing with integrated launching and landing (12 May 2015). 27

(3)

Rolf Luchsinger TwingTec AG & Empa Empa – Center for Synergetic Structures

Überlandstrasse 129 8600 Dübendorf

Switzerland rolf.luchsinger@empa.ch

www.empa.ch/css

Closing the Gap: Pumping Cycle Kite Power with Twings

Rolf H. Luchsinger1,2_{, Damian Aregger}3_{, Florian Bezard}2_{, Dino Costa}1,2_{, Cédric Galliot}1,2_{, Flavio Gohl}1,2_{, Jannis}

Heilmann3_{, Henrik Hesse}4_{,Corey Houle}1,3_{, Tony A. Wood}4_{, Roy S. Smith}4 1_{TwingTec AG}

2_{Center for Synergetic Structures, Empa} 3_{Institute of Aerosol and Sensortechnology, FHNW}

4_{Automatic Control Laboratory, ETH Zurich}

Pumping cycle kite power has attracted considerable in-terest over the last years. Several startups and research teams investigate this technology, particularly in Europe. The basic concept of pumping cycle kite power is well understood and theoretical and experimental investi-gations have revealed the potential of this technology. However, there are still some key elements of the technol-ogy where there is so far no consent among the different teams on how to solve them. In particular, the design of the kite and the launching and landing concept are top-ics, where very different solutions are followed up. For the kite, several teams operate with flexible tube and foil kites which stem from the surf kite industry. These kites are controlled either by the ground station through a mul-tiline configuration or by means of a control pod below the kite. On the other end of the spectrum, a rigid glider with all the control surfaces of an airplane is used, mov-ing the control authority from the ground station into the wing. As usual all these different approaches have ad-vantages and disadad-vantages. TwingTec is convinced that the ideal wing for pumping cycle kite power is a syner-getic combination of the light weight property of the surf kite with the aerodynamic and structural property of the glider. To this end we have developed over the last three years the twings, an acronym for tethered wing. Recently, we have demonstrated autonomous controlled pumping

cycles with our twing technology.

With respect to launching and landing, passive concepts which rely on the wind over ground as well as active con-cepts such as a tow launch or a rotating arm concept are studied. We are convinced that only active systems can fulfil the requirements of a commercial kite power sys-tem. By investigating a number of different approaches, we came to the conclusion that a system where rotors are integrated into the twing is the best option to fulfil all the necessary requirements. With such a tricopter de-sign, the twing hovers during launching and landing lead-ing to good control possibilities of these critical phases. The transitions into and out of the pumping cycles are done at high elevations enabling ample time and space for these processes. Finally, motor trust during hover can be augmented with the aerodynamic forces of the am-bient wind resulting in increased stability of the launch-ing and landlaunch-ing manoeuvre. The talk gives an overview over our TwingPower technology which has been pushed ahead over the last years in the frame work of a joint re-search project with Empa, FHNW and ETH. We consider TwingPower as the first system where all key elements of pumping cycle kite power including launching, land-ing and re-launchland-ing under various wind conditions in a closed loop process without human interaction can be achieved.

WIND ENERGY 2.0