Design for thermoelectric power generation using subsurface coal fires

Coal fires are worldwide environmental and economic hazards, which consume a large amount of valuable natural energy resources and cause environmental pollution. Given the enormous amount of waste heat produced, coal fires exhibit tremendous potential as recoverable energy sources, and can prove beneficial. This work proposes using the commercially available thermoelectric power generators to convert the waste heat generated from coal fires into useful power. In order to optimise the generators, experiments of thermoelectric power generation models were conducted to analyse the main thermoelectric characteristics such as the thermoelectromotive force of a thermoelectric couple, generator electrical resistance, maximum power output per unit cross-sectional area of thermoelements, maximum power output per unit contact area, and maximum thermoelectric conversion efficiency, as well as the cost-effectiveness of different types of generators. The TEG1-241-1.4-1.2 generator was identified as an optimal generator, after comprehensive analysis. Furthermore, it was found that the thermoelectric conversion efficiency could be improved by lowering the cold side temperature of the thermoelectric module. Finally, a distributed thermoelectric setup was designed with an installed maximum power output of 700 W for a temperature difference of ∼80 °C.