Passive solar high-yield seawater desalination by modular and low-cost distillation

Although seawater is abundant, desalination is energy intensive and expensive. Using the Sun as an energy source is attractive for desalinating seawater. Although interesting, current passive devices with no moving parts have unsatisfactory performance when operated with an energy flux lower than 1 kW m−2 (one sun). We present a passive multi-stage and low-cost solar distiller, where efficient energy management leads to significant enhancement in freshwater yield. Each unit stage for complete distillation is made of two hydrophilic layers separated by a hydrophobic microporous membrane, with no other mechanical ancillaries. Under realistic conditions, we demonstrate a distillate flow rate of almost 3 l m−2 h−1 from seawater at less than one sun—twice the yield of recent passive complete distillation systems. Theoretical models also suggest that the concept has the potential to further double the observed distillate rate. In perspective, this system may help satisfy the freshwater needs in isolated and impoverished communities in a sustainable way.