Improvement of direct absorption solar collectors (DASCs) performance by using nanofluids

Abstract

This Thesis explores the use of solar nanofluids and hybrid emulsions with phase change materials for direct absorption solar collectors. It aims to create new heat transfer fluids that can enhance the light absorption with low amounts of gold or carbon nanoparticles, transfer and store the absorbed heat effectively with the posibility to include phase change materials, which increase the total thermal energy storage density. Nanofluids and emulsions with improved sunlight absorption and good thermal cycling stability, maintaining good thermophysical properties, were developed. Finally, new experimental facilities with simulated or natural sunlight were developed to study the photothermal conversion efficiency. For this purpose, these new facilities with or without sunlight concentration were developed and the photothermal conversion evaluation was performed under different scenearios, considering heat losses and phase changes. Improvements in photothermal conversion efficiency of up to 121% were achieved in the case of gold solar nanofluids under simulated sunlight conditions, and up to 170% for hybrid emulsions with carbon nanoparticles under natural sunlight conditions.