Design and optimization of solar parabolic trough collector with evacuated absorber by grey relational analysis

Solar energy that contains bright heat and light from the sun is often controlled using modern technology such as photovoltaic, solar heating, artificial photosynthesis, solar architecture and solar thermal electricity. This study concerned with an experimental analysis of solar parabolic trough collector. The sunlight is reflected from the parabolic trough surface and focused on the evacuated absorber tube. The trough is usually aligned to the N–S axis and can be rotated normally according to the sun position from east to west. We have studied the potential of a solar thermal system for hot-water generation. The parabolic trough concentrator was made of galvanized sheet metal on which solar reflective films were pasted. The heat transfer fluid, viz. water runs through the absorber tube and absorbs concentrated heat energy. It has been designed with principal focus 0.1 m from the vertex so that the receiver heat loss is minimized. Data were collected on water inlet temperature, outlet temperature of the heat transfer fluid, solar radiation and water flow rate (days) during March to May 2019 at Coimbatore, Tamil Nadu, India. Also, the processing parameters were optimized because they are the key factors affecting the performance of the solar collector. Grey relational analysis was used to solve the optimization. Through confirmatory experiments, the input variables such as time, angle of tracking and solar radiation, as well as output variables such as inlet temperature, outlet temperature and efficiency were obtained, and the optimal conditions were verified. A suitable choice of input parameters such as tracking angle of 120° provides a high efficiency rate at 2 pm for March, April and May