Thermodynamic Modeling of a Hybrid Desalination System Using Solar Energy and Solid Wastewater Technology

Abstract

Solar energy has been used for various purposes in human societies for a long. Over the last few decades, the intensification of global warming has led to an increase in demand for new technologies to produce renewable energy without toxic by-products for the environment and climate dynamics of the planet. In this field, concentrating solar collectors play an outstanding role because they can absorb solar energy and convert it into thermal, mechanical, or electrical power, without producing excess waste. In this study, a concentrating solar collector with a parabolic-trough geometry was designed using a collector tube consisting of two concentric glass tubes with a vacuum in the annular space using water as the absorber fluid. To improve thermal utilization, a copper probe was embedded inside the tube to separate the flow of cold and hot water. The inlet fluid temperature and mass flow rate were assumed equal to 25°C and 0.08 kg/s, respectively. The wind speed in the first part of the analysis was considered 5 m/s. The support bracket connected to the solar absorber is the main source of heat loss inside the system due to exposure to the ambient air. Such heat losses negatively affect the absorber outlet temperature, which in turn reduces the efficiency of the system. The heating of the absorber leads to an increase in the amount of heat transferred to the fluid. The resulting heat is lost due to radiation through the glass cover and conveying it to the support bracket. The temperature gradient is affected by different wind speeds. This is because more than 98% of the surface of the support bracket is exposed to the ambient air, which is the main source of heat loss. Increasing the number of support brackets connected to the absorber tube causes an increase in heat loss. In addition, the thermophysical properties of the support bracket material, such as thermal conductivity and its capacity to store heat affect the heat exchange.