Multi-objective technoeconomic optimization of an off-grid solar-ground-source driven cycle with hydrogen storage for power and fresh water production

Abstract

Utilizing renewable sources integrated with thermodynamic cycles has been gaining attention in recent years due to being economical and environment-friendly, among which, renewable-energy driven water and power generation systems have shown promising outcomes. In the field of renewable-energy based multi-generation systems (MGS), many recent works have focused on energy analysis or simple optimization. Therefore, in this study, an off-grid solar-geothermal cogeneration system which is able to produce power by Kalina cycle, hydrogen by proton exchange membrane electrolyzer (PEMEC), and freshwater by a multi-effect desalination (MED) unit, was investigated and optimized in terms of economic and energy viewpoints. Unlike previous studies, in this work, a comprehensive multi-objective optimization (MOO) was employed on the system in order to find the optimal working condition. The decision variables of the optimization include flat plate collector area, water mass flow, and ammonia concentration of the Kalina cycle, and the objective functions were levelized cost of electricity (LCOE), payback period (PBP), the overall energy efficiency of the system, and freshwater production of MED unit. Final results show that the system, in its optimum condition, is able to produce 182.09 m3.day−1 fresh water, with energy efficiency, PBP, and LCOE equal to 6.23%, 5.19 years and 0.238 $.kWh−1, respectively.