Parametric Optimum Design of a Graphene-Based Thermionic Energy Converter

A new model of the thermionic energy converter (TEC) configured with the graphene-based cathode is proposed, which includes the thermal radiation between the cathode and the anode electrodes and the heat losses from the anode to the environment. Analytic expressions for the power output density and efficiency of the TEC are derived. The performance characteristics of the TEC are analyzed by numerical calculations. It is found that the maximum efficiency and power density can, respectively, reach 30% and 0.575 Wcm
^-2
when the TEC is operated between the two heat reservoirs at temperatures 1500 and 300 K. In addition, the optimum regions of the efficiency, power density, voltage output, electric current, and anode temperature are determined. The maximum efficiency and power density of the graphene-based TEC operated at different temperatures are calculated and compared with those of the metal-based TEC. It shows that the graphene-based TEC operated at 1200-1800K displays the better performance than the metal-based TEC. The results obtained here may provide guidance for the appropriate selection of electrode materials and optimum design of practical TEC devices.