LAUSR

Abstract In the present work, a nanofluid based volumetrically absorbing solar receiver having reflecting inner surfaces has been tested under outdoor conditions. Carbon soot nanoparticles from used motor oil dispersed in paraffin oil forms the working fluid. Results show that steady-state thermal efficiency peaks at an optimum nanoparticles volume fraction (ηth = 59 ± 4% at fv = 1%). Furthermore, the as-prepared nanofluid shows excellent stability i.e. it retains its optical characteristics and particle size distribution even after undergoing pumping and thermal cycles and moving in flow loops (circulation through pipes/valves) during on-sun testing. Moreover, the as-prepared nanofluid has negligible impact on the surface and optical properties of solar receiver constituent materials. Overall, the proposed receiver design and the as-prepared nanofluid stability represent significant steps towards realization of practical nanofluid based volumetric absorption solar thermal systems.