Energy and Exergy Analysis of a Two-Stage Thermoelectric Used for Heating and Cooling

In the present study a two-stage thermoelectric heater and a two-stage thermoelectric cooler are analyzed and compared from the perspectives of the first and second laws of thermodynamics. Based on the first law analysis results, for both two-stage thermoelectric heater and cooler, the coefficient of performance optimizes by current variation. The optimal value of coefficient of performance decreases with the hot and cold junctions temperature difference increasing. Based on the exergy analysis results, the exergy efficiency optimizes by the current variation same as the coefficient of performance. Moreover, for the case of heating, increasing the hot and cold side’s temperature difference increases the exergy efficiency but for the thermoelectric cooler leads to exergy efficiency reduction. Generally, the amount of exergy efficiency for two-stage thermoelectric cooler is lower than that of two-stage thermoelectric heater. Results show that optimum exergy efficiency of two stage thermoelectric heater is 0.181, 0.193 and 0.208 for hot and cold side temperature differences of 15, 30 and 45 K, respectively. Also, the optimum exergy efficiency of two stage thermoelectric cooler is 0.096, 0.073 and 0.04 for the same temperature differences between hot and cold side temperature differences.