Energy Harvesting from Knee Motion Using Dielectric Elastomer Generator

Abstract

The complement of standalone auxiliary sources with energy harvesters is essential in connection to mobile electronic devices and low power medical appliances due to some shortcomings like recharging of auxiliary cells and operation at low power. This paper deals with a motion based energy harvester which can harvest electrical energy in synchronous to human knee motion using dielectric elastomer (DE). Dielectric elastomer generator (DEG) adopts electrostatic energy conversion principle, by virtue of which the ambient mechanical motion converts into an analog electrical signal. It employs a biaxial stretched soft elastomer with compliant electrodes. At first, an electromechanical prototype is developed to be attached at the knee joints. The prototype constitutes of a DEG, a standalone power supply so as to prime the DEG and an electrical load. The periodical displacement of the knee leads to a synchronous change in capacitance associated with the DEG transducer. In consequence, a relatively high voltage generates across the load. With respect to different knee joint rotation angles, the harvested electrical voltage and current values are measured. Corresponding output electrical signals are measured and presented with respect to time with relevant variations with pre-stretch, coating, and deflection on DE. Parameters like peak power, specific energy and energy conversion efficiency are calculated at different conditions to determine the best condition for optimum electrical energy harvesting from the human knee motion.