Resonant energy transfer for membrane-free, off-grid solar thermal humidification–dehumidification desalination

Abstract

Fresh water scarcity is a pressing global issue exacerbated by climate change and growing populations. Current desalination technologies face limitations: reverse osmosis requires grid electrical power and specialized membranes, thermal desalination is inefficient and membrane systems are prone to fouling. Here we introduce Solar Thermal Resonant Energy Exchange Desalination (STREED)—a robust, membrane-free and efficient solar thermal desalination approach. STREED couples the basic mechanisms of humidification–dehumidification distillation to Resonant Energy Transfer, a dynamic energy recovery scheme described in the language of oscillators. Resonant Energy Transfer achieves optimized and controllable thermal gradients for passive evaporation and condensation. Dynamic tuning of system flow rates in response to varying solar intensities substantially increases efficiency, extending fresh water production over 24 hours per day. We predict week-long fresh water productivity increases of 77% with an average gained output ratio near ~1.9 at seawater salinity, depending on available solar irradiation. STREED adapts to fluctuating solar inputs, offering a scalable solution for decentralized, off-grid water treatment crucial for remote communities facing water scarcity. Although promising as a way to produce fresh water, all desalination technologies have limitations due to costs and inefficiencies. The realization of a membrane-free and solar thermal desalination approach combining humidification–dehumidification distillation and resonant energy transfer shows potential for a more efficient and robust off-grid desalination technology.