Comparative analysis of thermoelectric elements optimum geometry between photovoltaic-thermoelectric and solar thermoelectric

The optimization of the thermoelectric (TE) device geometry is one of the significant ways to improve its efficiency and power output. However, the complex relationship between the Photovoltaic and the thermoelectric device necessitates the need for the study of the optimum geometry of the thermoelectric device in a hybrid Photovoltaic-thermoelectric device. Therefore, this study investigates the optimum thermoelectric geometry for optimum performance of a Photovoltaic-thermoelectric (PV-TE) device and a solar thermoelectric generator (STEG). A three-dimensional finite element method is used to model the PV-TE and the STEG with different thermoelectric leg geometries. The performance of the PV-TE with two different PV cells and different TE leg geometries is investigated and compared with that of the STEG, and the optimum leg geometry for each device is identified. In addition, the effects of solar radiation and concentration ratio on the optimized device geometry performance are presented. Results obtained showed that the optimum thermoelectric geometry in a hybrid PV-TE device is dependent on the PV cell type and this is different from that of the STEG under the same conditions. The PV-TE device with cell 1 has an improved overall efficiency when a symmetrical (rectangular) thermoelectric leg is used however, this is different when the PV cell type is changed. In fact, the PV-TE device with cell 2 has an improved overall efficiency when a trapezoidal thermoelectric leg is used instead of a rectangular leg and this is the same as is the same trend observed in the case of the STEG. Therefore, the optimum geometry for a stand-alone solar thermoelectric generator cannot be directly used as a reference for the PV-TE device as the characteristics of the PV cell affects the PV-TE optimum geometry. Results from this study will indicate the different optimum geometries of STEG and PV-TE, and also provide a solid basis for optimization efforts in hybrid PV-TE devices. (C) 2019 Elsevier Ltd. All rights reserved.