Double-Sided Suspending Evaporator with Top Water Supply for Concurrent Solar Evaporation and Salt Harvesting

Abstract

Solar evaporation of seawater is promising to mitigate the fresh water scarcity problem in a green and sustainable way. However, salt accumulation on the photothermal material prevents the system continuous operation, and the water supply driven by capillary force severely limits the scale-up of the evaporators. Here, we demonstrate a double-sided suspending evaporator with top water supply and a surface water distributor for high-efficient concurrent solar evaporation and salt harvesting for large area applications. Both sides of the evaporator can evaporate water with automatic salt harvesting from the edge concurrently. Top water supply gets away from the limitation of capillary force for a larger area application and completely cuts off the heat leak to the bulk water below for higher efficiency. The energy conversion efficiency reaches 95.7% at 1.40 kg·m –2 ·h –1 with deionized water under 1 sun with a remarkable low surface average temperature (28.2 °C). Based on the simulation and experiment, a novel radial arterial water distribution system is developed to efficiently distribute water on a larger evaporation surface. The water distribution system alters the water transport path in the evaporation surface, leading to salt accumulation on the surface body, where salt is unable to be harvested by gravity automatically. This problem is further resolved by cutting out the salt accumulation area (16.4%) on the surface to create a floriform evaporator, which forcedly exposes the salt at the edge for harvesting. Up to70 h continuous solar evaporation from salt water at a rate of 1.04 kg·m –2 ·h –1 with concurrent salt collection on this floriform evaporator is achieved. This work resolves water supply and salt accumulation problems in scaling up the solar evaporators and advances the structural design of evaporators for high-efficient large area applications.

Ferric Tannate-Decorated Polyester Fiber Pillar with Vertical Channels for Zero Liquid Discharge Solar Desalination

“…By restricting heat within the sunlight-absorbing layer, the ISSG evaporator achieves an excellent evaporation rate. Based on the sunlight absorber, the sunlight-absorbing layer can be classified into four types: plasmas like Au, carbon-like carbon nanotubes, semiconductors like CuS, and polymers like polypyrrole . Ferric tannate (FeTa) as a complex is widely used in the ISSG field due to its advantages of low cost and high solar absorptivity in preparing sunlight-absorbing layers .…”

“…Based on the sunlight absorber, the sunlight-absorbing layer can be classified into four types: plasmas like Au, 7 carbon-like carbon nanotubes, 8 semiconductors like CuS, 9 and polymers like polypyrrole. 10 Ferric tannate (FeTa) as a complex is widely used in the ISSG field due to its advantages of low cost and high solar absorptivity in preparing sunlight-absorbing layers. 11 Notwithstanding the notable sunlight absorption capacity in the ISSG system, attaining satisfactory evaporation rates remains a substantial challenge.…”

Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

“…The reported salt producing photothermal materials mainly adopt the following strategies: zero liquid discharge (ZLD) 410 and water flow control for local salt accumulation. 399,411,412 ZLD is an effective method for achieving salt production during the evaporation process of light and hot water. A typical ZLD process consists of a concentration system and a crystallization system.…”

“…The reported salt producing photothermal materials mainly adopt the following strategies: zero liquid discharge (ZLD) 410 and water flow control for local salt accumulation. 399,411,412…”

“…Owing to the radial arterial water distribution system and the floriform evaporator, the salts gather on the edge of the floriform evaporator and fall down due to gravity for collection. 412 Moreover, the 3D evaporator with a 1D or 2D water path not only enhanced the water evaporation rate, but also provided more salt crystal accumulation spots for automatic salt harvesting. For example, Xia et al combined a water evaporation tray and a vertical solution absorption line (1D) to form a new type of solar evaporator (Fig.…”