Comparative thermal performance enhancement study of a reverse - irradiated and direct - irradiated direct absorption solar collector using silver nanofluid

Abstract

ABSTRACT Plasmonic nanofluids have emerged as strong candidates for future working fluids in direct absorption solar collectors (DASC). However, in novel DASC systems, a significant temperature gradient exists over working fluid depth increasing emissive losses and hence, results in low thermal conversion efficiency. Considering these issues, a laboratory scale prototype of reverse-irradiated DASC system (RR–DASC) has been tested under controlled laboratory conditions and compared with a direct irradiated DASC system (DR–DASC) using silver nanofluids at three different mass concentrations i.e., 0.1 mg/L, 0.2 mg/L, and 0.4 mg/L. Ag nanoparticles were having monodisperse spherical shape with surface plasmon resonance (SPR) peak occurring around 395–400 nm. The experimental results showed that RR–DASC maintains uniform temperature over the fluid depth, while about 3–4°C temperature gradient was noticed in direct irradiated DASC system under similar operating conditions. A maximum photo-thermal conversion efficiency of about 80% was observed using 0.4 mg/L Ag nanofluids in RR–DASC system. The presented work can pave the ways for future development of highly efficient DASC systems for low to high temperature solar applications.