Integration of low-temperature desalination with geothermal heating for heat-water cogeneration

Geothermal energy offers a stable and renewable heat source for desalination and space heating applications. However, existing studies focus on standalone geothermal-driven desalination or heating, while comprehensive thermodynamic and economic assessments of water-heating cogeneration systems remain limited. This study introduces a novel heat–water cogeneration system that retrofits spray-assisted low-temperature desalination with existing domestic geothermal heating infrastructure. The system achieves cascading energy utilization: high-temperature geothermal heat drives desalination, while low-grade condensation heat supplies space heating. Thermodynamic and economic analyses are conducted for the integrated system, with comparative assessments against the standalone geothermal heating and desalination systems. Results reveal that the proposed cogeneration system achieves a maximum freshwater productivity of 48.23 m3/d, with peak First law efficiency and Second law efficiency reaching 86.23 % and 21.86 %, respectively, outperforming the standalone heating and desalination systems. Furthermore, life-cycle cost of water is reduced to 0.45 $/m3, lower than any reported geothermal-driven desalination systems. By leveraging existing infrastructure, the proposed heat–water cogeneration system unlocks scalable deployment potential for remote regions with dual demands for heating and freshwater.