Battery charging considerations in small scale electricity generation from a thermoelectric module

This project involves the development of a prototype electrical generator 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 electricity produced is used to charge a single rechargeable 3.3 V 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 explores 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 °C across the TEG. At a temperature gradient of 150 °C, the effective resistance 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.