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C1: Waste heat recovery
The concept of a tubular π-type device proposed over a decade ago in the viewpoint of its high availability, for examples, the power generator and Peltier cooling device mediated by the fluid.1) Its systematic study has not been reported so far because of difficulty to construct the tubular device with complicated arrangement of the p-, n-type thermoelectric (TE) materials and electrodes connecting TE materials.
In this presentation, we report the development and its TE properties of the tubular π-type device made of the Bi2Te3-based p- and n-type TE materials. The obtained one is composed by 50 pairs of alternate stacks of ring-shaped p- and n-type TE materials separated by the insulators along the tubular axial direction. The electrical connections between adjacent TE materials were realized by the cylindrical internal and external electrodes embedded on the inner and outer wall of the tube. The typical dimension of the tubular device is 110 mm in length, 10 mm in inner diameter, and 14 mm in outer diameter. In the synthesis of the tubular device, we carried out the powder compaction of the TE materials into the ring shape followed by the sintering powders and joining with electrodes using the spark plasma sintering method. In the TE properties, we measured the thermal and electric properties including exchange thermal power, tube resistance, generated voltage and output power under the temperature difference (ΔT) between hot water inside and cold water outside of the tube. We observed the open-circuit voltage of Voc ~ 1.5 V and output power P ~ 4.5 W with ΔT = 85 K below T = 100 oC.
1) A. Yamamoto et. al., The proceedings of 18th ICT (1999) 312-315, G. Min et. al., Semicond. Sci. Technol. 22 (2007) 880–883, A. Schmiz et. al., J. Electron. Mater. 42, (2013) 1702-1706