Vibration energy harvesting with uni-polar electret film

Abstract

Electronic devices are highly demanded commodities and will continue increasing in popularity in the near future, all of which require powers in one way or another. A challenge that arises in remote or inconvenient locations is access to reliable power sources. Energy harvesting technology is critical in the development of self-powered electronic devices. In this paper we present a novel approach to vibration energy harvesting, which is based on uni-polar electret film. Uni-polar electret film is of a flexible polymeric material which can exhibit permanent polarization and induce durable electric filed. In this study, real charge electret films are prepared by using the negative corona charging one-side metalized irradiation cross-linked polypropylene (IXPP) films. Vibration energy harvesters based on such electret films are designed and fabricated. The charge stability in IXPP electret film is investigated by measuring the surface potential of sample. The electromechanical properties of the energy harvester sample are tested by measuring quasi-static and dynamic sensitivities. The energy harvesting from vibrations by using the energy harvester sample, at various vibration frequencies, load resistances, and seismic mass values, is also studied. The results show that as the IXPP film is charged with a corona voltage of -13 kV, grid voltage of -2.0 kV and charging time of 60 s, the stable surface potential of -680 V is obtained after 15-day storage in the laboratory environment. The quasi-static sensitivity of energy harvester sample is 1800 pC/N at a pressure of 1.3 kPa. At an optimum load resistance of 80 M and a resonance frequency of 70 Hz, a maximum output power of 5 W is obtained for an energy harvester sample with an effective area of 13 cm2 and a seismic mass value of 42.2 g.