Battery Charging Considerations in Small Scale Electricity Generation from a Thermoelectric Module

Abstract

This project involves the development of a prototype electrical gen erator for delivering and storing small amounts of electricity. Power is generated using the thermoelectric effect. A single thermoelectric generator (TEG) is utilised to convert a small portion of the heat flowing through it to electricity. The electricit y produced is used to charge a single rechargeable 3.3 Volt lithium - iron phosphate battery. This study investigates methods of delivering maximum power to the battery for a range of temperature gradients across the thermoelectric module. The paper explore s load matching and maximum power point tracking techniques. It was found that, for the TEG tested, a SEPIC DC - DC converter was only beneficial for temperature gradients less than 100 ⁰ C across the TEG. At a temperature gradient of 150 ⁰ C, the effective re sistance of the battery was close to the internal resistance of the TEG. For temperature gradients in excess of 100 ° C a DC - DC converter is not suggested and a simple charge protection circuit is sufficient.