Development and modeling of thermal energy harvesting setup

A setup for a thermal energy harvesting based on a conversion of a thermal energy into a mechanical energy followed by a conversion of the mechanical energy into an electric field energy has been developed. The key elements of such a setup are a bimetal spring and electrodes covered by electret layers with a permanent charge. The electrodes are kept at different temperatures. The bimetal spring exchanges the thermal energy with the "hot" and "cold" electrodes. The heating and cooling stimulates the spring vibrations. During the vibrations the spring acts as a common plate of two variable capacitors. The electrodes with the electret layers are the fixed plates of these capacitors. The charge induced continuously at the plates of the capacitors is transferred via a rectifying circuit to the external capacitor. Several aspects of the setup development have been considered, including different electret materials, different methods of the electret charging, and different load capacitors. A compact model of the charging effect has been also developed. It has been implemented in Qucs program, where it is represented as a so-called equation defined device component.