Multi-criteria optimization of a renewable hydrogen and freshwater production system using HDH desalination unit and thermoelectric generator

This article presents the exergoeconomic evaluation of a new geothermal-based integrated system, which produces hydrogen and freshwater. The proton exchange membrane electrolyzer (PEME) and humidifier-dehumidifier (HDH) units are responsible for hydrogen and freshwater production, respectively. Kalina cycle and thermoelectric generator (TEG) provide the needed electricity to run the PEME. As both TEG and HDH work with low-temperature waste heat of the Kalina cycle and geothermal water, two different configurations for the suggested system are proposed, and evaluated by the exergoeconomic analysis. Levelized cost of evaluation (LCoE) also compares the suggested configurations with fossil fuel power plants, while the effects of various critical parameters of the system are evaluated in the parametric study. Since there are uncertainties about decision parameters, single- and multi-objective optimizations with properly defined objectives are performed to achieve the best performance in each operating mode. Optimization studies revealed that the optimal mode is superior in terms of exergy efficiency, freshwater cost, and hydrogen cost with the values of 22.49%, 2.94 $/m(3) and 7.37$/kg, respectively.