Investigations on nanofluids and thin film for performance improvement of direct absorption solar parabolic trough collector

Abstract

Global climatic change has significantly affected various sectors around the newlineglobe. Experts attribute it to the excess emission of carbon to the environment, the newlinemajor contributor being fossil fuels. It has been widely acknowledged that newlineharvesting renewable energy could replace fossil fuels to a certain extent. Among newlinethe various renewable energy sources, solar energy is the most promising due to its newlineavailability and accessibility. Solar energy is harvested mainly to produce electrical newlineand thermal energy. The conversion of solar energy to thermal energy is found to be newlinemore efficient than electricity. Conventionally, solar-thermal conversion is achieved newlinethrough the surface absorption technique. Later studies have reported that direct newlineabsorption of solar energy by the working fluid can enhance the performance by newlineminimising the intermediate losses. In direct absorption solar collectors, solar newlineabsorptivity of the heat transfer fluid is of great importance. Though various type of newlinenanofluids is investigated in solar parabolic collectors, hybrid nanofluids and newlineQuantum dot nanofluids are least explored. The heat losses from the solar collectors newlinecould also be reduced by incorporating a solar selective internal coating in the newlineabsorber tube. The present thesis focuses on enhancing solar-thermal conversion of newlineparabolic collectors by augmenting the thermal and optical properties of working newlinefluids and/or employing solar selective coatings. newlineA hybrid nanofluid consisting of SiO2/Ag-CuO nanoparticles were newlinesynthesised by the two-step method. The influence of particle concentration and newlinesurfactant concentration on thermo-optical properties were investigated using the newlinedesign of experiment concept. Analysis of variance (ANOVA) was employed to newlinestudy the significance of the process parameters on thermal conductivity and solar newlineweighted absorption fraction of nanofluid. The statistical optimisation of the newlineprocess parameters was done using the desirability function.