Water Harvesting Strategies through Solar Steam Generator Systems

Abstract

Solar steam generator (SSG) systems have attracted increasing attention, owing to its simple manufacturing, material abundance, cost‐effectiveness, and environmentally friendly freshwater production. This system relies on photothermic materials and water absorbing substrates for a clean continuous distillation process. To optimize this process, there are factors that are needed to be considered such as selection of solar absorber and water absorbent materials, followed by micro/macro‐structural system design for efficient water evaporation, floating, and filtration capability. In this contribution, we highlight the general interfacial SSG concept, review and compare recent progresses of different SSG systems, as well as discuss important factors on performance optimization. Furthermore, unaddressed challenges such as SSG's cost to performance ratio, filtration of untreatable micropollutants/microorganisms, and the need of standardization testing will be discussed to further advance future SSG studies.

Updated perspective on solar steam generation application

“…For typical 2D evaporators, a common issue faced in developing SSG is the huge thermal loss towards the bulk water. 10,21,23 In order to minimize this energy loss, heat isolation is one of the important factors in designing interfacial SSG systems. Besides using a low thermal conductive material as a water absorbing substrate (Fig.…”

“…15,16 Many previous SSG systems have pursued heat generation performance through introducing different types of PTM with potentially a short bandgap for a broader light absorption. 10 Besides this, a recent study has highlighted another important aspect of developing a PTM with high joint density of states (JDOS). The existence of high JDOS allows for high population of hot electrons and holes, promoting higher photoexcitation, broadening the wavelength range for light absorption, as well as a faster relaxation process of the photoexcited carriers.…”

“…However, there are limited number of studies that discussed the importance of microbial filtration. [10][11][12][13] In addition to water evaporation performance, another aspect that are rarely discussed in previous studies is efficient water collection. This is important in calculating freshwater yield for average water consumption to potentially replace current water production systems.…”

“…However, there are limited number of studies that discussed the importance of microbial filtration. 10–13…”

Investigation of structure–property–application relationships of a hydrogel-based solar vapor generator

“…For instance, polyvinyl alcohol (PVA) hydrogels containing numerous -OH groups initially proposed by Yu's group 28,29 are most oen employed as SVGs due to their excellent chemical stability and low cost. [30][31][32][33][34][35] Meanwhile, a considerable number of studies have reported SVGs based on other hydrophilic polymer networks, such as -SO 3 H groups in polystyrene sulfonates, 36 -NH 2 groups in polyacrylamides, 37,38 and -C-O-Cgroups in polyethylene glycols. 39,40 Unfortunately, these studies have overlooked the structure-property-application relationship of hydrogel-based SVG systems.…”