Thermo-economic assessment and optimization of a multigeneration system powered by geothermal and solar energy

Abstract

A novel multigeneration system using dual renewable energy sources (i.e., geothermal and solar) is introduced, analyzed, and optimized. The integration of a geothermal line, a solar tower, a steam Rankine cycle, two organic Rankine cycles, an ejector refrigeration cycle, a thermoelectric generator unit, and a reverse osmosis subsystem forms the entire system. The outputs of this energy-conversion system are heating load, cooling load, electricity, and freshwater. Regarding methodology, the energy, exergy, and exergoeconomic approaches are implemented to assess the system from thermodynamic and economic viewpoints. Moreover, an optimization process based on exergy efficiency and the total unit cost of products is executed to determine the system’s optimal decision variables. The results obtained from the optimization process show that the proposed system is able to achieve 25.4% exergy efficiency and 34.1 $/GJ total unit cost of products, exhibiting 48% and 43% improvement compared to a base case study. Furthermore, the methodology is demonstrated on a case study where the system operates at its optimum condition in a specific location. Having monthly average values of direct normal irradiation for this spot, the average hourly performance of the system is evaluated for each month. Based on the obtained results, the minimum and maximum freshwater production rates are 3.06 kg/s and 3.84 kg/s, respectively. It can be estimated that a range of 1224 to 1536 individuals, varying from month to month, can receive the produced freshwater.