Humidification–Dehumidification Desalination and Hybrid Configurations: Productivity, Cost, and Sustainability

Freshwater scarcity continues to intensify the need for energy-efficient and environmentally sustainable desalination technologies. This review provides a unified, cross-technology comparison of membrane-based reverse osmosis, thermal multi-effect distillation and multi-stage flash, and humidification–dehumidification desalination, with emphasis on renewable-driven and hybrid humidification–dehumidification configurations. Novelty is established through a standardized comparison framework that harmonizes gained output ratio, coefficient of performance, specific energy consumption, and levelized water cost across stand-alone and hybrid systems to support technology selection and deployment decisions. Large-scale reverse osmosis achieves specific energy consumption near 2 kWh/m3 and water costs below $0.50/m3, while multi-effect distillation reaches gained output ratio values of 8–16 under favorable thermal conditions. Optimized solar-driven humidification–dehumidification demonstrates freshwater productivity up to 516 L/day, and humidification–dehumidification coupled with a heat pump achieves gained output ratio up to 8.88 with production rates exceeding 80 L/h. Solar-assisted humidification–dehumidification reaches productivity up to 15.7 L/kWh with stabilized output when integrated with thermal storage, while reported costs remain variable, ranging from $0.93–$12/m3 for solar humidification–dehumidification and up to about $20/m3 for heat pump driven configurations. Emerging advancements including ultrasonic atomization, nanofluid-enhanced solar collection, multi-stage designs, and integrated heat recovery are synthesized to identify pathways for improved productivity, scalability, and brine management.