Thermoeconomic analysis and optimization of a geothermal-driven multi-generation system producing power, freshwater, and hydrogen

Abstract

Global warming and the insufficiency of fossil fuels have elicited in human beings envisaging the optimal employment of energy resources and attention to heat recovery systems. Grounded on this context, in this study, a geothermal-driven multi-generation system cogenerating power, freshwater, and hydrogen is proposed, comprised of multi-effect distillation (MED), organic Rankine cycle (ORC), and proton exchange membrane (PEM) electrolyzer. A comprehensive numerical model, hinged on energy, exergy, and exergoeconomic analyses, is developed as means of assessing the proposed system. Key parameters, namely, ORC inlet and MED first effect temperature, and geothermal water mass flow rate are investigated. Thereafter, using the multi-objective TOPSIS method, these parameters are optimized, based on freshwater production, exergy efficiency, and sum unit cost of the product (SUCP) for five different geothermal mass water flow rates (20 kg/s to 100 kg/s). The study finds that the generation of 2419–4274 tons of CO2 is prevented by using the system instead of fossil fuels, and thereof $ 150,000 to $ 256,000 would be saved in taxes. The system produces freshwater (0.28 kg/s to 1.5 kg/s) and hydrogen (0.0009 kg/s to 0.0045 kg/s), at a cost rate of 175 $/h to 587.5 $/h in the optimal state with various mass flow rate of geothermal.