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.