Power-Generation Performance of a π-Structured Thermoelectric Module Containing Mg₂Si and MnSi_1.73

Abstract

In recent years, environmental problems, for example global warming and depletion of energy resources, have become serious. Thermoelectric power generation has attracted attention as a means of reducing the effects of such problems. Thermoelectric conversion technology can convert thermal energy directly into electrical energy. Therefore, exhaust heat can be converted into electrical energy. Moreover, it is a clean method of power generation that does not discharge CO₂ gas when the electricity is generated. The purpose of this study was to fabricate a thermoelectric (TE) module that can be used at mid-range temperatures of 573–873 K. The component materials selected were Mg₂Si as n-type semiconductor and MnSi_1.73 as p-type semiconductor. These compounds are non-toxic, environmentally benign, lightweight, and relatively abundant compared with other TE compounds. Ag paste was used to join the components. To prevent diffusion of Ag at the interface of the components and the electrodes, the top and bottom of the components were coated with Ni. The TE module was composed of 12 pairs of elements and Ag seats were used for the electrodes. The dimensions of both p and n-type components were 5.0 mm × 5.0 mm × 6.3 mm. Module size was 36.5 mm × 36.0 mm × 7.0 mm, and alumina was used as substrate. The module was inserted between hot and cold plates, in air, and output power was measured. The open circuit voltage and the maximum output power were 1.6 V and 5.6 W, respectively, at ΔT = 548°C (hot side 587°C; cold side 39°C), and the output power density estimated from these results was 4.4 kW/m².