A small heat capacity solar distiller with extra effective discharge for brine by the siphoning of a hydrophilic membranous wick

As an efficient method of seawater desalination, multi-stage solar distillation based on interfacial heat localization is facing to the problems of salt ions accumulation and crystallization that hard to discharge, which makes it difficult to obtain scalable and sustainable water production. Here we proposed and explored a fully passive and extra efficient discharge mechanism of concentrated brine based on open siphoning flow. Nano fiber is used as the super-hydrophilic membranous wick to analyze open siphoning flow. It is found the siphoning flowrate tends to the same value when each of suction height and short transverse flow length is large enough, which makes it possible to match the siphoning flowrate and heat capacity among multiple evaporation-condensation interfaces. A three-stage solar distiller was constructed and studied theoretically and experimentally. Under one sun (1000 W/m²), the water productivity is 238 g/h, which is nearly 82% of the total seawater flowing in, and the remaining 18% flows out as strong brine with a salinity of 19.6%. In addition, a water production of 940 g is obtained with an average gained-output ratio of 1.5 in a whole-day test, namely, 11.99 kg/(d·m²). This study may improve large-scale interfacial evaporation with efficient salt rejection.