Benoît Python Mechanical Engineer Kitepower B.V. Kluyverweg 1 2629 HS Delft Netherlands b.python@kitepower.nl www.kitepower.nl
Methodology Improvement for the Performance Assessment of a
Pumping Kite Power Wing
Benoit Python
Delft University of Technology, École Polytechnique Fédérale de Lausanne Pumping kite power systems are a promising way of
har-nessing clean energy from high-altitude winds in a cost-effective way. The power output of such innovative sys-tems is directly related to the wing aerodynamic proper-ties that therefore play a key role. Moreover, the latter, often assumed with best guess, are also required for com-putational simulations at development stage.
Recently, the research group of TU Berlin [1] designed a towing test bench and procedure for evaluating flexi-ble airfoil performances in an automated and repeataflexi-ble manner. By towing the kite at a prescribed speed, rele-vant information, such as tether force and elevation an-gle, are extracted and can be translated into wing aero-dynamic properties thanks to a simple analytical model (point massless kite, straight massless-dragless tether). With the purpose of improving the assessment of wing aerodynamic properties and their exactitude, the present work takes advantage of the TU Berlin test bench by in-vestigating the prototype wing from Kitepower. An alter-native testing methodology is suggested and compared against the current procedure from TU Berlin, indicat-ing a dynamic behaviour of the kite. An improved 2D quasi-steady point mass model is implemented to com-pute the kite aerodynamic properties by taking both wing and tether mass as well as tether aerodynamic effects into consideration. It shows noticeable discrepancies in CL(+16%) and CD(-10%) with respect to the simple ana-lytical model. Eventually, a detailed tether model from differential equations is developed to assess its sag and
effects on the intrinsic kite performance. This leads to even more difference in CD(-25%). Eventually, this work provides CLand CDof the kite itself and shows that such aspects as tether drag and sag should not be neglected when assessing the intrinsic aerodynamic properties of the wing.
Kite
Driving path
Test bench Driving vehicle
For the case of vanishing wind, the ground vehicle tows the kite back and forth the runway while measuring forces, angles, speed for different line configurations.
References:
[1] Hummel, J.: Automatic measurement and characterization of the dynamic properties of tethered flexible wings, Ph.D. thesis, Berlin University of Technology (2017)
