Exploratory modeling and experimental investigation of a vibrating-stripe wind energy converter

The future of portable devices is ultimately a challenge on energy conversion and storage, fought on two fronts: battery life and distributed availability of power sources. Nano-scale energy conversion devices are highly attractive for the market, but the non-PV systems still lack in efficiency and portability. Few years ago the Windbelt® system was presented with a new ingenious rotor-free approach for nanoscale wind energy harvesting through aeroelastic fluttering. Aim of this work is to provide a mathematical model with experimental validation to the scientific framework related to the Windbelt technology. An experimental device with variable length was built and tested under different belt tension conditions. The basis of the windbelt technology consists in the movement of a magnet linked to the belt that oscillates between two coils. In the tested device the movement of the magnet was recorded with a high speed camera and the images processed in order to evaluate instantaneously its rotation and vertical deviation from the resting position. Results of the experimental campaign were compared with the output of an aero-elastic model of the belt. The model is based on the assumption of a belt composed of two interconnected sections: the free belt section, whose aeroelastic behaviour is represented by a nonlinear lift coefficient, and the magnet section, where the motion is governed by the inertial and elastic forces. The results of the testing campaign and the model outputs showed a remarkable agreement for what concerns the frequency response of the system.