Infrared spectral emittance profiles of spectrally selective solar absorbing layers at elevated temperatures

A study was made to characterize parametrically the spectrally selective absorptance profiles of typical interference, bulk absorption, and mixed-type absorbing layers for solar-thermal conversion at temperatures to 500 degrees C. A five parameter empirical Fermi function was used to model the spectral absorptance converted from the measured spectral reflectance. An alternative method using the Fermi model is presented for defining the ir spectral emittance profile, as scaled to the measured hemispherical total emittahce.