Spectrally and angularly selective photothermal and photovoltaic converters under one-sun illumination

The efficiency of both photothermal and photovoltaic (PV) converters may be increased if their emittance is strongly forward-peaked. This technology was recently proposed for photothermal converters by Blanco et al (2004 Solar Energy 76 683). Ideal angularly and spectrally selective surfaces were defined in this paper. Optimization procedures for appropriately defined spectral and angular quantities were developed to maximize solar energy conversion efficiency. The optimization procedure for photothermal conversion is similar but formally simpler than that used by Blanco et al. The optimization procedure and the results shown here for PV conversion are new. The potential of the proposed technology to increase conversion efficiency is more important in the case of photothermal conversion (maximum possible increase of efficiency is about 0.3) than in the case of PV conversion (possible increase is about 0.1). This potential is weakly dependent on the irreversibilities inside both types of solar converters.