Study and realization of a selective surface for thermal conversion of solar energy: application to medium range temperature

Abstract

This study is concerned with the design of a selective surface, in view of its possible utilization in the range of medium temperature solar energy thermal conversion (between 80 and 200 °C). The study of significant parameters (absorption and emission factors, cut-off wavelenth,...) allows the determination of optical properties for such a surface. It is so demonstrated that a hot selective surface shows a good interest for helio-thermal conversion at medium range temperature. A two thin layers selective structure on a metallic substrate is then determined: Lead sulfide and zinc sulfide deposition on to aluminium substrate leads to convenient theoretical results, that are experimentally confirmed. Moreover, replacement of aluminium by zinc or nickel seems to be encouraging. Generally an absorption factor of 80% is obtained, together with a 6% global hemispherical emissivity value at 200 °C. Durability tests as a function of temperature showned significant results.