A Novel Electric Power Generation Mechanism from Waste Heat without Temperature Gradient
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A Novel Electric Power Generation Mechanism from Waste Heat without Temperature Gradient Keita Yamasoto1, Yuki Osakabe1, Sota Adachi1, Shinji Munetoh1 and Osamu Furukimi1 1
Kyushu University, 744 Motooka, Fukuoka, 819-0395, JAPAN.
ABSTRACT Seebeck effect is widely used for the energy harvesting from wasted heat. In the Seebeck effect, the electric power can be generated by the temperature difference between both ends of the thermoelectric materials. However, low conversion efficiency is caused by heat flux from hot side to cold side of sample. In this paper, we have proposed a new thermal power generation mechanism with no temperature difference. We investigated the band structure of Ba8AuxSi46-x clathrate single crystal synthesized by Czochralski method. The single crystal has a gradient of the gold contents along the growth direction. According to the results of Seebeck coefficient, the electrical properties of the Ba8AuxSi46-x clathrate dramatically changed depending on the gold contents. In the case of gold content of lower than 5.33, the Ba8AuxSi46-x clathrate showed a ntype semiconductor. In the case of gold content of higher than 5.33, the Ba8AuxSi46-x clathrate showed a p-type semiconductor. The band gap of the n-type and p-type Ba8AuxSi46-x clathrate were wider than the intrinsic semiconductor. We can successfully synthesize a n-p junction single crystal, which obtaining energy band curve generated from the difference of Fermi level between p- and n- type semiconductors. The single crystal was heated under the uniform temperature and able to obtain generated electric voltage of around 0.6 mV at 400°C. These results suggested that the obtained electric voltage can be generated from the separation of holeelectron pair excited by heating at the intrinsic part with a narrow band gap along to the energy band curve formed by p-n junction. INTRODUCTION Various internal-combustion engines release waste heat, which equals to around 70 % of the total energy. Thermoelectric materials can recover the waste heat and contribute to an environmental issue [1-3]. Generally, Thermoelectric materials need a temperature difference for producing an electric power by Seebeck effect. The heat flux generated by the temperature difference causes a loss of energy from cold side. Therefore, the idea to decrease the energy loss from the heat flux is required. In this paper, we have proposed a new thermal power generation mechanism with no temperature difference [4]. Ba8AuxSi46-x clathrate is a promising material for this novel mechanism because this material dramatically changes the band structure depending on gold contents. In the case of gold content of lower than 5.33, the Ba8AuxSi46-x clathrate showed a n-type semiconductor. In the case of gold content of higher than 5.33, the Ba8AuxSi46-x clathrate showed a p-type semiconductor [5]. According to the results of temperature dependence of Seebeck coefficient and ab initio calculation, the band gap of the n-type and p-type Ba8AuxSi46-x clathrate were wider than the intrinsic semico
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