Spectrally selective solar absorber stable up to 900 °C for 120 h under ambient conditions

Concentrated solar power (CSP) technology, which converts sunlight into heat and then electricity, is an attractive alternative to photovoltaics because of its high capacity for thermal-energy storage, which can be converted to electricity after sunset. As the efficiency of this technology is limited by the Carnot efficiency, higher absorber temperatures are desirable. At high temperatures the conversion efficiency is limited by the heat loss from solar absorbers via radiation in infrared wavelengths. Hence, it is desirable to develop selective solar absorbers, which can absorb solar radiation while reflecting infrared radiation. It is also important to develop high temperature selective solar absorbers, which can work in ambient conditions to reduce cost as compared to those that work under vacuum. Here, we report a selective solar absorber made of black chrome/ITO/SiO2, deposited on stainless steel, which showed stable performance at 900 °C under ambient conditions for 120 h. The proposed selective solar absorber exhibits an absorptance of 0.9 in the solar spectrum with an infrared emittance of 0.4 beyond wavelengths of 6 μm.