Performance Evaluation And Parameter Analysis Of AMTEC/TAR System For Power And Cooling Cogeneration

In this study,energy and exergy analysis were performed on AMTEC(Alkali Metal Thermal to Electric Converter).And then,the AMTEC/TAR hybrid system was proposed to utilize the waste heat of AMTEC for a triple-effect absorption refrigeration(TAR).A theoretical analysis has been undertaken to evaluate the performance of the hybrid system.For the energy and exergy analysis of vapor anode AMTEC with multiple tubes,the AMTEC model was established to study the effects of heat source temperature,external load,evaporation and condensation temperatures on the irreversibility in the components of AMTEC,thermoelectric conversion efficiency and exergetic efficiency.The results show that the maximum exergy loss comes from different components under different parameters.When the evaporation temperature increases to a relatively large value,the maximum exergy loss is caused by the heat loss.The maximum exergy loss is from the condenser when the condensation temperature is large.When the electrode current density is large,the maximum exergy loss is from BASE.As the evaporation temperature increases,the thermoelectric conversion efficiency and exergetic efficiency of AMTEC increase,the exergy loss percentage in the BASE,evaporator and condenser gradually decreases,and the exergy loss percentage from cathode/BASE to the inlet of condenser gradually increase.There exists an optimum value of the temperature of BASE for the maximum thermoelectric conversion and exergetic efficiency.When the condensing temperature increases,the exergy loss from BASE,evaporator and the cathode/BASE to the condenser inlet are reduced,but the exergy loss in condenser gradually increases.With the increase of electrode current density,the thermoelectric conversion and exergetic efficiency rise first and then decrease,the exergy losses in remaining components are reduced in addition to heat loss.The exergetic efficiency decreases with the increase of the heat source temperature.Except for the evaporator,heat source temperature has little effect on the exergy loss percentage in remaining components.Based on the above analysis,the AMTEC/TAR hybrid system was proposed in order to improve the heat utilization efficiency of AMTEC.Thermodynamics and economic analysis have been undertaken to evaluate the performance of the hybrid system.The effects of the condenser temperature in AMTEC,the external load of AMTEC,absorption temperature,medium pressure generator pressure and the temperature of medium and low pressure generators on the performance of the combined system were investigated and discussed.The results show that the thermal efficiency of the AMTEC/TAR hybrid system is significantly higher than that of AMTEC.When the evaporation temperature of AMTEC is 1200K and the effectiveness of solution heat exchanger is 0.75,the optimal value of exergetic efficiency of hybrid system is 42.7%,and the electric power and the cooling capacity are 48.8 kW and 110.2 kW,respectively.When the BASE temperature is 1274K and the total area of AMTEC electrodes is 28.6m~2,the hybrid system investment recovery period is 3 years.There also exists an optimum value of condenser temperature in AMTEC for maximum exergetic efficiency of hybrid system,and this optimum value decreases linearly with the increase of AMTEC evaporation temperature.As the condenser temperature in AMTEC increases,the annual net income of the hybrid system gradually decreases.With the increase of electrode current density,the exergetic efficiency and annual net income increase first and then decrease.The coefficient of performance(COP)in TAR subsystem,exergetic efficiency and the annual net income of hybrid system decrease with the increase of absorption temperature.Increasing the effectiveness of solution heat exchangers leads to an increase in the exergetic efficiency of combined system,but the investment costs and the annual net income decrease.When the temperature difference between the medium-pressure generator and the medium-pressure generator heat source is very small,the exergetic efficiency of hybrid system and COP decrease with the increase of the pressure in the medium-pressure generator.As the temperature difference between the low-pressure generator and the low-pressure generator heat source gradually increases,the exergetic efficiency of hybrid system and COP both increase first and then decrease.But this effect is small when the temperature difference is relatively low.The exergy loss in combined system mainly comes from BASE,heat loss in AMTEC,the BASE/cathode to the condenser inlet,absorber,and high-pressure generators.Under normal operating conditions,the maximum exergy loss is from heat loss in AMTEC.