Designing a bioinspired synthetic tree by unidirectional freezing for simultaneous solar steam generation and salt collection

Abstract

Solar steam generation with thermal localization was recently proposed for highly efficient solar‐thermal desalination. However, to achieve high steam productivity with long term stability remains a critical challenge due to salt accumulation at the evaporation surface. Here, we designed a T‐shaped synthetic tree that could simultaneously achieve high steam productivity and salt collection with the structure characteristics of interfacial thermal evaporation, ambient energy harvesting and edge‐preferential crystallizing. Under 1 sun, the synthetic tree exhibited a steady water evaporation rate of 2.03 kg m−2 hours−1 over 60 hours, achieving solar thermal efficiency of 75%. Salt was continuously rejected at the edge of the evaporator with a steady collection rate of 59.879 g m−2 hours−1, which did not affect water evaporation. This new design principle to simultaneously harvest water and salt provides a new avenue for solar energy utilization.

Salt Mitigation Strategies of Solar‐Driven Interfacial Desalination

“…Another PVA synthetic tree device, similar to the “plate” structures, can control salt only accumulate at the edge of the structure. [ 114 ] As shown in Figure 9b, PPy is polymerized on the surface of the t‐shaped synthetic tree to enhance its light absorption, and internal nanochannels ensure efficient water delivery and low thermal conductivity. Under 1 simulated sun (1 kW m −2 ), the evaporation rate of the synthetic tree was 2.03 kg m −2 h −1 , the salt mitigation rate was 59.879 g m −2 h −1 , and the light‐to‐heat conversion efficiency was 75%.…”

Artificial Trees Inspired by Monstera for Highly Efficient Solar Steam Generation in Both Normal and Weak Light Environments

“…This phenomenon is caused by the gradient concentration of salt solution and had been demonstrated in other works. [6,27,28] After daytime desalination, salt crystals on the edges of the leaves can be collected and thereby expose a fresh surface for continuous desalination on the next daytime.…”

“…[ 12–15 ] The directional freezing method, porous foams, and plant materials are used to produce or provide large channels for water and steam transport. [ 16–21 ] Special structures, including the Janus structure, [ 22,23 ] interconnected structure, [ 24–26 ] and salt collection structure, [ 6,27,28 ] are designed to prevent salt from crystallizing, thus ensuring long‐term evaporation. Multilayer and hierarchical structures are designed to enhance the thermal and light management abilities of the evaporators.…”

Highly Salt‐Resistant 3D Hydrogel Evaporator for Continuous Solar Desalination via Localized Crystallization

“…[ 22–26 ] Recently, the localized crystallization concept has been proposed to overcome the salt deposition challenge by tuning the transport and distribution of brine in the photothermal layer. [ 27,28 ] Unlike conventional salt‐resistant methods, such design leads to salt crystallization only on the edge of the evaporation disc by enhancing the radial brine transport, spatially isolating salt from the major part of the evaporation surface. However, a remained challenge for the localized crystallization evaporators is that the excessive radial transport and insufficient vertical absorption from bulk brine by 1D thread water channels and porous capillary structure, as the only water supply unit for solar evaporation, reducing the overall evaporation performance and hindering such evaporators for high‐salinity desalination.…”