Salt-rejecting continuous passive solar thermal desalination via convective flow and thin-film condensation
Patrick I. Babb, S. Farzad Ahmadi, Forrest Brent, Ruby Gans, Mabel Aceves Lopez, Jiuxu Song, Qixian Wang, Brandon Zou, Xiangying Zuo, Amanda Strom, Jaya M. Nolt, Tyler Susko, Kirk Fields, Yangying Zhu
Abstract
Passive solar desalination is an emerging low-cost technology for freshwater production. State-of-the-art desalinators typically evaporate water using wicking structures to achieve high solar-to-vapor efficiency. However, wicking structures have limited salt rejection capability, which typically limits the operating duration to several hours. In addition, few studies have demonstrated efficient condensation to achieve a high solar-to-water efficiency. Here, we report a passive inverted single-stage solar desalinator that achieves continuous desalination and efficient condensation by convection-mediated salt diffusion and a novel mode of thin-film condensation. We experimentally demonstrate a record-high continuous passive desalination and salt rejection test duration of 168 h (7 days) under one-sun illumination. Our desalinator achieves a water collection rate of 0.5 kg m−2 h−1, which corresponds to a 32.9% solar-to-water efficiency. Furthermore, we develop a theoretical transport model and perform a parametric study to guide further optimization. This work signifies an improvement in the robustness of current state-of-the-art desalinators.