Experimental investigation of an asymmetric compound parabolic concentrator-based direct absorption solar collector using plasmonic nanofluids.

Plasmonic nanofluid-based direct absorption solar collector (DASC) systems have shown a better perspective over surface-based solar thermal collectors. These nanofluids demonstrated high thermal performance in photo-thermal conversion efficiency even at minute concentration compared to other tested nanofluids. However, very few studies have been reported so far with real-time outdoor experiments to show the opportunities and challenges in the practical applications of concentrating DASC systems. For the work presented here, an asymmetric compound parabolic concentrator (ACPC)-based DASC system has been designed, fabricated, and tested using mono-spherical gold and silver nanoparticle-based plasmonic nanofluids over several clear sky days at Jalandhar city (31.32° N, 75.57° E), India. The optical and morphological properties of synthesized nanoparticles were studied using UV-Vis spectrophotometry and High-resolution transmission electron microscopy (HR-TEM). Photo-thermal conversion tests were conducted using different working fluids and compared with a flat DASC system under similar operating conditions. The experimental results revealed that ACPC-based DASC system reached a maximum thermal efficiency of around 70% using plasmonic nanofluids which was approximately 28% higher than a flat DASC system with water as the working fluid. The stability analysis showed that plasmonic nanofluids are capable of retaining their optical properties even after several hours of sun exposure. The present study highlights the use of plasmonic nanostructures for achieving high photo-thermal conversion efficiency in concentrating DASC systems.