Multigeneration energy systems integrating geothermal-driven power and a novel combined cycle for simultaneously producing electricity, cooling, green hydrogen, and oxygen: A sustainability and thermo-economic assessment

The present contribution proposes a novel geothermal-driven quad-generation system based on a new combined cycle and capable of simultaneously producing electricity, cooling, green hydrogen, and oxygen as value-added products. The system includes a primary Combined Power and Absorption Refrigeration Cycle (KC-ARC) driven by an ammonia-water mixture and coupled to a proton exchange membrane (PEM) electrolyzer for hydrogen and oxygen co-production and a second Kalina cycle for additional waste heat recovery. Next, for such multi-generation systems, impacts of major operating conditions on the system performance have not yet been comprehensively investigated. Indeed, in addition to an exergy efficiency, thermo-economic performance analysis and optimization method commonly reported, an evaluation in terms of sustainability assessment and total costs of green hydrogen and oxygen production along with electricity and cooling generation is carried out at the first time. Key parameters are the temperature of the geothermal source, the high pressure, and the ammonia basic mass fraction of the ammonia-water mixture. The results show that the proposed system can achieve a net power output of 242.7 kW, a hydrogen production rate of 103.59 kg/day, an oxygen production rate of 821.92 kg/day, and a cooling capacity of 1989 kW. At a geothermal temperature of 140°C, the energy and exergy efficiencies reach 0.4352 and 0.4355, respectively. Furthermore, optimization results obtained at an optimal temperature of 179.2°C reveal significant performance improvements, including increases of 38.34% and 6.75% in net powers 1 and 2, respectively, 38.03% in hydrogen production rate, 38% in oxygen production rate, and 3.45% improvements in both energy and exergy efficiencies. Finally, the average production costs of hydrogen and oxygen are estimated at 4.95 $/kg and 0.6237 $, respectively, with an exergetic sustainability index of 0.8653, confirming the sustainable and efficient nature of the proposed system.