In embodiments of the present invention, an energy extractor includes a capacitor which experiences capacitance and voltage changes in response to movement of a capacitor plate or of a dielectric material. In one embodiment, a third plate is positioned between first and second plates to create two capacitors...http://www.google.es/patents/US6127812?utm_source=gb-gplus-sharePatente US6127812 - Integrated environmental energy extractor
