Thermophotovoltaic system configurations and spectral control

Thermophotovoltaic (TPV) systems can be characterized by several different parameters including system electrical conversion efficiency, photovoltaic cell electric power density, infrared (IR) emitter temperature and system costs. One way of dividing TPV systems into three categories is via high (T > 1400 degreesC), medium (T between 1400 degreesC and 1100 degreesC) and low (T < 1100 degreesC) IR emitter temperature. In the high T category, silicon cells can be used with porous rare earth oxide selective emitters operating at over 1400 degreesC. For low T emitters, cells with band gaps below 0.6 eV are being studied. These cells are typically made with ternary and quaternary compounds using MOCVD. They are being developed for space and military applications where these cells operate at temperatures of 30 degreesC and below. These systems can potentially have efficiencies over 15%. Diffused junction GaSb cells can be used with IR emitters in the mid-temperature range. These cells can potentially be made at low cost in high-volume production. With emitter temperatures of 1250 degreesC, these cells operate with power densities of 1 W cm(-2). These cells can be operated at 60 degreesC for combined heat and power applications. Systems using these cells can have electrical conversion efficiencies well over 10%. Spectral control is another important parameter characterizing TPV system configurations. While various means of high efficiency spectral control for low- and mid-temperature systems have now been demonstrated with single-cell experiments, the frontier now lies in integrating cell arrays, heat sources and IR emitters with spectral control into complete systems.