Design and Experimental Characterization of a Pumping Kite Power System

The pumping kite concept provides a simple yet effective solution for wind energy conversion at potentially low cost. This chapter describes a technology demonstrator which uses an inflatable membrane wing with 20 kW nominal traction power on a single-line tether. The focus is on the innovative and scientifically challenging development aspects, especially also the supervisory control and data acquisition system designed for automatic operation. The airborne hardware includes a Kite Control Unit, which essentially is a remote-controlled cable manipulator, and the inflatable wing with its bridle system allowing for maximum de-powering during the retraction phase. On the ground, the drum/generator module is responsible for traction power conversion while constantly monitoring and adapting the force in the tether. The control software includes two alternating autopilots, one for the lying figure eight maneuvers during tether reel-out and one for the reel-in phase. As a result of monthly test-operation since January 2010, large quantities of measurement data have been harvested. The data acquisition and post-processing is presented and discussed for representative conditions. The power curve of the system and other characteristic operational parameters are determined by a statistical analysis of available data and compared to the results of a theoretical performance analysis.