A Sustainable model for the integration of solar and geothermal energy boosted with thermoelectric generators (TEGs) for electricity, cooling and desalination purpose

Abstract

In this research paper, an integrated energy system for the production of cooling, hot water, and electricity along with desalinated water is proposed, simulated, assessed, and optimized. This integrated energy system is composed of a geothermal well, a single-effect Li/Br and water absorption chiller, parabolic trough collectors (PTCs), a steam Rankine cycle (SRC) and, a reverse osmosis desalination unit. Instead of the condenser, thermoelectric generators (TEGs) are used to increase the generated electricity by the SRC. The system's performance is evaluated in terms of energy, exergy, and exergoeconomic, and the cases with the TEG is compared to the system with the condenser, and results are discussed and investigated. Using the TEG instead of a condenser, results in reducing the total cost rate and enhancing the system's exergy efficiency. Also, the performance of the system was evaluated for four different days in Shiraz city. For the selected days in spring, summer, fall, and winter, the highest generated electricity of the system with the thermoelectric generator is 1087 kW, 1158 kW, 1133 kW, and 766.5 kW, respectively. Thus, the system with thermoelectric is selected for optimization. To optimize the system, seven decision variables are selected namel, the geothermal fluid temperature, the total solar aperture area, the collector outlet temperature, the inlet pressure of the turbines, the TEG figure of merit, the turbine outlet pressure, and the evaporator pinch point temperature difference. Total cost rate and system exergy efficiency are considered as two objective functions. To determine optimum values of the objective functions, a multi-objective genetic algorithm is applied, and also the Pareto frontier figure is obtained. In this figure, the best point is chosen from the technique for order of preference by similarity to ideal solution (TOPSIS) decision-making criterion, where the cost rate is 10.41 ($ / GJ), and the exergy efficiency is 20.52%.