Photo-Thermal Conversion Efficiency of Spectrally Selective Cr <sub>2</sub>O <sub>3</sub>/Cr/Cr <sub>2</sub>O <sub>3</sub> Multilayered Solar Absorber

Abstract

Renewable energy is the alternative resource to deal with environmental problems and to satisfy the ever-increasing energy demand. Concentrating Solar Power (CSP) systems are valuable candidates to harness solar energy. CSP systems first convert solar radiation into thermal energy which is much easier and economical than storing electricity. The solar absorbing surface is the critical part of CSP systems, as it directly affects the efficiency of the solar thermal energy conversion into electricity. To achieve high conversion efficiency of incident light into heat, the solar absorber should be spectrally selective. To obtain this spectral selectivity, various designs such as absorbing semiconductor-metal tandems, composite films and multilayer interference stacks with multiple dielectric and metallic thin films have been used such as Cr2O3, Al2O3, HfO2, Ni, Cr, and Zr. However, their optical properties determine the efficiency of the energy conversion from the concentrated solar irradiation to the thermal energy recovered by the heat transfer fluid or nanofluid. This paper experimentally investigates on the photo-thermal conversion efficiency of Cr2O3/Cr/Cr2O3 multilayered selective solar absorber (SSA) deposited onto stainless steel substrates by using an electron beam physical vapor deposition technique. Interestingly, the fabricated Cr2O3/Cr/Cr2O3 SSA showed good photo-thermal conversion efficiency with a peak temperature exceeding 180 °C after an irradiation time of 2500 s; this obtained value is comparable to the performance of state-of-the-art SSA surfaces.