35 Kazuo Arakawa Kyushu University Research Institute for Applied Mechanics 6-1 Kasuga-koen, Kasuga Fukuoka, 816-8580 Japan k.arakaw@riam.kyushu-u.ac.jp www.riam.kyushu-u.ac.jp/fracture/ ARAKAWA_group/indexA-j.htm
Performance Characterisation of Airborne Wind Rotor
Kazuo Arakawa
Research Institute for Applied Mechanics, Kyushu University
To harvest wind energy at high altitude, we constructed an airborne wind rotor using a rocket shape balloon. As a trans-port method of wind energy from high altitude to the ground, we employed the elastic deformation of tether rope made of polymeric fibers. Different from traditional wind turbines that convert wind energy into electric power using a generator lo-cated near a turbine and send electric current to a ground by metal wires, the present method can permit a large weight saving of the wind rotor. This study examined the air stability of the wind rotor and measured the torque and tension of the tether rope induced as a function of time. Analytical model was also used to examine the performance of the construct-ed wind rotor.
We constructed an airborne wind rotor as follows: A rock-et shape balloon was fabricated using vinylchloride of thick-ness 0.13 mm. The balloon size was 1.3 m in diameter, 8.2 m in length, and 18 m3 in gas capacity, and the mass was about 8 kg. Three blades made of corrugated plastic plates were attached to the rear part of the balloon. The blade size was about 0.65 x 0.8 m and the blade angle was 14 deg along the circumference of the balloon. Tether rope was connected
through support lines hooked to the nose-section of the bal-loon to avoid stress concentration.
The elastic deformation of a tether rope is an important pa-rameter to investigate energy transportation from the wind rotor to the ground. A torque and tension measuring device was then constructed to evaluate the elastic deformation. This device is consisted of a torque and tension gauge con-nected linearly to determine two forces simultaneously. We used a torque gauge, a tension gauge, and a data logger to record two forces. Two nylon ropes with 30 m in length and 6 mm in diameter were used as the tether ropes.
We measured the torque and tension of the tether ropes at the ground as a function of time. An analytical model was in-troduced to determine force and torque of an airborne wind rotor and to compare with tension and torque of the tether ropes. Although data fluctuation existed, the experimental re-sults positively suggest that the constructed wind rotor has a promising structure for harvesting wind energy at high alti-tude. We are now measuring electric power due to the torque of tether ropes at the ground using an electric generator.
