Experimental performance analysis of low concentration ratio solar parabolic trough collectors with nanofluids in winter conditions

Applications of solar thermal systems especially for heating are quiet reliable. At present the domestic use of such technologies especially for hot water and space heating applications is limited to flat plate collectors and evacuated tubes. Moreover, commercial use of nano-fluids is also scarce in these applications. The present study is designed to evaluate the experimental performance analysis of a locally developed Parabolic Trough Collector (PTC) system having concentration ratio of 11 for domestic heating applications primarily. Two metallic oxides water based nanofluids i.e. Al2O3/H2O and Fe2O3/H2O are used at three particles concentrations of 0.20%, 0.25% and 0.30% by weight at 1.0, 1.5 and 2.0 L/min flow rates. The experimentation is performed under wide range of operating conditions in terms of solar radiation and ambient conditions at Taxila, Pakistan. The maximum efficiencies achieved with Al2O3 and Fe2O3 nanofluids at 2 L/min are 13% and 11% higher respectively compared to water under same operating conditions. Al2O3 nanofluids seemed more favorable in the enhancement of efficiency of PTC compared to Fe2O3 for domestic applications using PTC. The results offer significant insight from the commercialization aspect for the working of locally developed linear PTC and influence of nano-fluids for space heating application.