Thermodynamic Analysis And Structure Optimization For Solar Thermoelectric And Photovoltaic Hybrid Generator System

A finite analysis model for thermoelectric module of bismuth telluride is established. Results of both finite analysis and experiment are compared. The Results show that the performance of thermoelectric module in simulation is almost the same as that in experiment, verifying that the analysis model developed in the dissertation is correct.A finite element model for single P-N conjunction of two-stage thermoelectric module of solar thermoelectric-photovoltaic hybrid generator system which concerning contact resistant and material property is developed. The performances of P-N conjunctions of both bismuth telluride and skutterudite under maximum efficiency are analyzed. The result shows that the efficiency of two-stage thermoelectric module consisting of P-type bismuth telluride sizing 1.8 mm×1 mm×1 mm, N-type bismuth telluride sizing 1.8 mm×1 mm×0.98 mm, N-type skutterudite sizing 4.08 mm×1 mm×1 mm and P-type skutterudite sizing 4.08 mm×1mm×1.32 mm reaches the peak, at 11.922%.A model for solar thermoelectric device is developed based on above study. Performances of solar thermoelectric device under different operation conditions are analyzed. The results show that heat losses due to conduction, natural convection and radiation decrease the performance of solar thermoelectric device greatly. Materials with low heat conductivity are preferred in fillet in P-N junction to minimize heat loss. Materials with high absorbtivity and low emissivity are also preferred to maximize the usage of solar energy. Under a reasonable condition (thermal conductivity of insulate is 0.05 W/mK, emissivity is 0.1, contact resistant is 50μOcm2), the efficiency of solar thermoelectric device based on two-stage thermoelectric module can reach 6.902%.The exergy analysis model is developed based on exergy theory and thermal analysis. The exergy loss of each component of the thermoelectric device is considered. The result shows that heat loss of heat conduct, natural convection and heat radiation decrease the exergy efficiency of the thermoelectric device greatly. It is important to minimize the above mentioned heat loss. Under a reasonable condition, the exergy efficiency of solar thermoelectric device with two-stage thermoelectric module can reach 11.04%.The thermal analysis model for the solar thermoelectric-photovoltaic hybrid generator system is developed based on the thermal analysis of thermoelectric and photovoltaic sub-system. The prismatic wavelength, thermal efficiency and exergy efficiency are analyzed. The result shows that both the thermal and the exergy efficiency of solar thermoelectric-photovoltaic hybrid generator system peak when the prismatic wavelength equals to the cut-off wavelength of the photovoltaic material. It is important for the usage of both the quantity and the quality of the energy. Under above optimized condition, the thermal and exergy efficiency of the solar thermoelectric- photovoltaic hybrid generator system reaches 20.42% and 29.81% respectively.