Optical EngineeringLow-cost solar selective absorbers from Indian galena
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The main thrust of our research is to prepare a low-cost solar-selective absorber from an indigenous semiconducting mineral, galena (galena aggregate and galena concentrate), for a solar thermoelectric generator. We report the results of preparation and characterization of solar-selective coatings made from galena aggregate and galena concentrate collected from the Zawar mines in Rajasthan, India. The coatings of galena are prepared by a thermal evaporation technique and exhibit high absorptivity (α~0.95 and 0.97) in the solar spectral range and low emissivity (ε 375~0.21 and 0.27) in the thermal range. Finally, these coatings were compared with synthesized PbS coating prepared in our laboratory and found to be quite comparable. The structure and composition of the coatings were studied by x-ray diffraction and electron spectroscopy for chemical analysis. Reflectance and absorption studies were made in the 0.3- to 3.1-μm spectral range.