Photo-thermal conversion analysis of a medium-flux direct absorption solar system using gold nanoparticles with natural extract of Azadirachta Indica

Abstract

Abstract Recently direct absorption solar collector (DASC) system had emerged a new class of solar collectors with much improved solar thermal conversion potential over conventional surface-based absorption solar collectors. Further, introducing noble metallic particles like Ag, Au, Al, TiN or Cu in the working fluids enhanced the optical properties of working fluid and hence the overall thermal performance of such DASC systems. But these novel thermal systems are prone to high emissive and radiative losses at high-temperature ranges. Additionally, the nanoparticles used in the working fluid are expensive, complex to synthesise and mostly non-biodegradable. In the present study, a medium-flux asymmetric compound parabolic concentrator (ACPC) based concentrating DASC system has been tested over clear sky days in the months of September and October 2022 at the composite climate of Jalandhar, India. A hybrid heat transfer fluid is prepared using Azadirachta Indica leaves extract and blended with gold plasmonic nanoparticles to improve the overall thermal performance of DASC system. Stored Energy Fraction (SEF) of hybrid heat transfer fluid at a depth of 2cm reached about 74.9%, which is about 67% higher than water. The outdoor experiments showed that hybrid heat transfer fluid had 10.4°C higher temperature gains in concentrating DASC system, and the photo-thermal efficiency was enhanced up to 40% as compared to water. The study demonstrates the advantage of an eco-friendly, low cost and highly stable hybrid heat transfer fluid as a potential candidate for a medium-flux DASC system.