Performance optimization analysis of solar thermophotovoltaic energy conversion systems

By applying metamaterial absorber and emitter, the STPV system with unity emitter-absorber area ratio exhibits conversion efficiency between 8% and 10% with concentration factor varying between 20 and 200. However, the performance of the STPV system with unity emitter-absorber area ratio becomes unacceptably bad with higher concentration factor mainly because of the greatly enhanced radiation energy loss due to the thermal emission from the absorber. In this case, in order to reduce the radiation energy loss, the emitter-absorber area ratio needs to be enlarged. This work systematically analyze the influence of the emitter-absorber area ratio on the performance of STPV system with concentration factor varying between 200 and 500. Non-ideal conditions such as metamaterial emitter/absorber, non-ideal adiabatic layer and copper plate heat exchanger are also taken into consideration. It turns out that, when the concentration factor ranges from 200 to 500, the conversion efficiency of the STPV system with optimized emitter-absorber area ratio increases from 13% to 14.8% while that with unity emitter-absorber area ratio decreases from 8.6% to 3%, which indicates a maximal difference of around 12% under 500 suns. Furthermore, the output power density for the STPV system with optimized emitter-absorber area ratio is also analyzed. The result shows that the output power density increases from 1650 W/m2 to 2300 W/m2, which is much larger than the output power density of a conventional Si-substrate single-junction solar cell. In summary, this work demonstrates the advantages of STPV system with optimized emitter-absorber area ratio, which can be applied in the field of designing solar thermophotovoltaic devices.