Thermodynamic analysis of thermophotovoltaic efficiency and power density tradeoffs

This report presents an assessment of the efficiency and power density limi tations of thermophotovoltaic (TPV) energy conversion systems for both idea l (radiative limited) and practical (defect-limited) systems. Thermodynamic s is integrated into the unique physics of TPV conversion, and used to defi ne the intrinsic tradeoff between power density and efficiency. The results of the analysis reveal that the selection of diode band gap sets a limit o n achievable efficiency well below the traditional Carnot level. In additio n it is shown that filter performance dominates diode performance in any pr actical TPV system and determines the optimum band gap for a given radiator temperature. It is demonstrated that for a given radiator temperature, low er band-gap diodes enable both higher efficiency and power density when spe ctral control limitations are included. The goal of this work is to provide a better understanding of the basic system limitations that will enable su ccessful long-term development of TPV energy conversion technology. (C) 200 1 American Institute of Physics.