Three-Dimensional Mirror-Assisted and Concave Pyramid-Shaped Solar–Thermal Steam Generator for Highly Efficient and Stable Water Evaporation and Brine Desalination

Abstract

Although significant advances have been achieved in developing solar-driven water evaporators for seawater desalination, there is still room for simultaneously enhancing water evaporation efficiency, salt resistance, and utilization of solar energy. Herein, for the first time, we demonstrate a highly efficient three-dimensional (3D) mirror-assisted and concave pyramid-shaped solar–thermal water evaporation system for high-yield and long-term desalination of seawater and brine water, which consists of a 3D concave pyramid-shaped solar–thermal architecture on the basis of polypyrrole-coated nonwoven fabrics (PCNFs), a 3D mirror array, a self-floating polystyrene foam layer, and a tail-like PCNF for upward transport of water. The 3D concave pyramid-shaped solar–thermal architecture enables multiple solar light reflections to absorb more solar energy, while the 3D mirror-assisted solar light enhancement design can activate the solar–thermal energy conversion of the back side of the concave pyramid-shaped PCNF architecture to improve the solar–thermal energy conversion efficiency. Crucially, selective accumulation of the precipitated salts on the back side of the concave pyramid-shaped architecture is realized, ensuring a favorable salt-resistant feature. The 3D mirror-assisted and concave pyramid-shaped solar-driven water evaporation system achieves a record high water evaporation rate of 4.75 kg m–2 h–1 under 1-sun irradiation only and exhibits long-term desalination stability even when evaporating high-salinity brine waters, demonstrating its great applicability and reliability for high-yield solar-driven desalination of seawater and high-salinity brine water.

A natural gain strategy of passive cycling water vapour escape toward efficient freshwater purification

“…The effectiveness of this work is demonstrated by the fact that the performance of the TIE with natural convection support is ∼32% greater than that of 3D evaporators with side evaporation and no forced convection. 32–37…”

Three-Dimensional Spiral Evaporator with Side Channels for Efficient Solar-Driven Water Purification

“…In general, the performance of a solar evaporator is related to two factors: the properties of the photothermal material used and the structural design of the evaporator. Photothermal materials play an essential role in interfacial solar evaporation, which can convert the absorbed sunlight into heat for vapor generation at the air–water interface. , Common photothermal materials include carbon materials, − metal plasma, , semiconductors, − and organic polymers. − As a conjugated polymer, polypyrrole (PPy) has unique advantages such as outstanding photothermal properties, high stability, and low cost and is a promising photothermal material for solar evaporation applications. − For example, Fan et al demonstrated that the light absorption of cellulose papers can be significantly increased from 48% to 95.5% when they are coated with PPy . Yu et al also showed that a hierarchically nanostructured poly­(vinyl alcohol) gel containing PPy as the photothermal additive can achieve an impressive solar energy harvesting efficiency of over 95% .…”