Modeling and performance evaluation for solar thermoelectric generator with variable-temperature heat sink

To explore the spatial variation pattern of temperature field in solar thermoelectric generator device with continuous fluid heat sink and the effect of thermoelectric element arrangement on device performance, this study develops a three-dimensional model for solar thermoelectric generator with variable-temperature heat sink that can be solved numerically. Considering external thermal resistances, radiation and convection losses of collector, Fourier heat leakage, air gap leakage and Thomson effect, the energy conservation equations, power and efficiency expressions are derived by combining heat transfer theory and non-equilibrium thermodynamics. The operating temperature and cooling water temperature distributions along flow direction are obtained by using differential element method. Impacts of meteorological conditions, operating parameters and geometric parameters on system performance are analyzed in detail. The variation of optimal performance in a day is simulated based on the solar irradiation observed in summer, and the economy of device is also discussed. Results indicate that the primary thermal resistance of device is concentrated at the convection heat transfer process of cooler, and cooling water temperature and operating temperatures increase linearly along the flow direction. As flow channel length increases, the corresponding power increases, while efficiency decreases. An optimal combination of fill factor and electrical current exists to maximize power and efficiency, which can reach 596.22 W and 4.98 % at noon, respectively. The payback period of device is approximately 3.55 years.