Pilot-Scale Solar Powered Two-Stage Humidification–Dehumidification Desalination With Freshwater Absorption and Fine-Grained Heat Recovery
Shen Liang , Cancan Zhang , Yuting Wu , Yanjie Zheng , Yasong Sun , Yifan Wang , Xinglong Ma
Engineering ›› : 202608013
Humidification–dehumidification (HDH) desalination is attractive for decentralized small- and medium-scale freshwater production because it operates at atmospheric pressure and can be driven by solar thermal energy and other low-temperature heat sources. However, conventional HDH systems are still limited by coarse and temperature-mismatched internal heat recovery, which underutilizes recoverable latent heat and brine sensible heat from condensation for subsequent evaporation demand. This leads to low gained output ratios (GORs), bulky heat and mass transfer components, and high thermal consumption. To address these limitations, this paper proposes a fine-grained heat recovery strategy by routing feed seawater through multiple heat recovery stages and using dual condensation to recover latent heat from high-temperature humid air. A pilot-scale two-stage HDH desalination system powered by a 120 m2 solar vacuum tube collector array was designed and tested, with vertically stacked high- and low-temperature stages for compactness. Experiments across spray temperatures of 62–80 ℃, followed by a full-day test under fluctuating solar irradiance, were conducted to evaluate freshwater production and GOR. At a spray temperature of 80 ℃, the system achieved a freshwater production rate of 97.2 kg·h−1 and a GOR of 1.78. The reheating process increased freshwater production from 88.2 to 97.2 kg·h−1 and improved the GOR from 1.71 to 1.78. Under fluctuating solar conditions, the daily freshwater production reached 860 kg, corresponding to 7.17 kg·m−2·day−1 on the basis of the collector aperture area. These findings demonstrate the effectiveness of the fine-grained heat recovery strategy and support the advancement of HDH desalination toward higher efficiency and lower thermal consumption.
Humidification and dehumidification (HDH) / Fine-grained heat recovery / Solar thermal desalination / Stacked structure / Freshwater absorption
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