Thermoelectric module construction for low temperature gradient power generation

Energy related carbon dioxide emissions are the largest contributors to greenhouse gasses [1]. Thermoelectric power generation that exploits natural temperature differences between the air and earth can be a zero-emission replacement to small stand-alone power sources. Maximizing the temperature drop across the module is crucial to achieving optimal output power. An equation relating output power to thermoelectric module parameters is derived. In addition, several configurations are investigated experimentally. Output power shows a significant dependence on module surface area. In the setups tested, one side of the thermoelectric module was thermally coupled to the earth, while the other side was left exposed to air. This paper evaluates three 110hour experiments. The surface area of the exposed side was varied by a factor of about 15 without changing the area covered by thermoelectric elements. The output power shows a direct dependence on exposed surface area and changes by about a factor of 25. Nomenclature S surface area of module A cross sectional area covered by elements KA thermal conductivity of air Ke thermal conductivity of elements ρ resistivity of elements q heat transfer through module q’ heat transfer from module to air U heat transfer coefficient TA air temperature TC cold side temperature TH hot side temperature L element length α Seebeck coefficient Rtot. total thermal resistance of module N number of elements