Performance assessment of the photon enhanced thermionic emitter and heat engine system

The aim of this research is to show the potential application of a photon enhanced thermionic emitter (PETE)–irreversible heat engine (HE) hybrid system. Solar energy has the greatest potential for clean energy, and thermionic emission is the alternative way to convert heat and light into electricity. PETE is an efficient solar to electricity converter comparing to other solar converters, which its efficiency can reach above 50%. Briefly, PETE–heat engine system is analyzed, where the PETE is the main cycle and HE is the bottom cycle. Receiving temperature to PETE above 1000 K and this heat can be utilized by a bottom cycle, heat rejected by the PETE is used by the heat engine, and additional power output is obtained. In addition to basic performance evaluation consisting of power output and electricity efficiency, some exergetic parameters are considered. These exergetic parameters can be listed as: exergy efficiency, depletion ratio, waste exergy ratio, exergetic sustainability index, exergetic ecological index, and modified exergetic ecological index. According to the results, power output, energy efficiency, exergy efficiency, sustainability index, ecological exergetic index, and modified ecological index are 63.698 W cm−2, 0.637, 0.721, 2.603, 0.652, and 0.477, for the optimum cathode temperature and for the optimum anode work function are 67.295 W cm−2, 0.673, 0.764, 3.312, 0.735, and 0.616 are possible to be achieved.