Water harvesting from Soils by Solar-to-Heat Induced Evaporation and Capillary Water Migration

TL;DR

This paper introduces a solar-driven method to harvest water from shallow soils by heating and capillary migration, offering a sustainable solution for fresh water supply in arid regions.

Contribution

It presents a novel, passive soil water harvesting technique using solar energy, combining evaporation and capillary flow, with experimental validation of its effectiveness.

Findings

Maximum water harvesting rate of 99.8 g/h in laboratory

Approximately 900 ml of water harvested in 12 hours

Estimated 360 g/h water yield per square meter under one sun

Abstract

Fresh water scarcity is one of the critical challenges for global sustainable development. Several novel water resources such as passive seawater solar desalination and atmospheric water harvesting have made some progress in recent years. However, no investigation has referred to harvesting water from shallow subsurface soils, which are potential huge water reservoirs. Here, we introduce a method of solar-driven water harvesting from soils, which can provide cheap fresh water in impoverished, arid and decentralized areas. The concentrated solar energy is used to heat the soils to evaporate the soil moisture. Then vapors flow to the condenser through tubes and condense as freshwater. Sustainable water harvesting is realized by water migration due to capillary pumping effect within soils. In the laboratory condition, an experimental setup is designed and its water-harvesting ability from soils is investigated. The maximum water mass harvesting rate was 99.8 g h-1. In about 12 h, the total harvesting water could be as high as about 900 ml. The whole process is solar-driven and spontaneous without other mechanical or electrical ancillaries. The water harvesting rate under one sun energy flux (1 kW m-2) is estimated to be about 360 g h-1 with a 1 m2 solar concentrator. Our proposal provides a potential onsite and sustainable fresh water supply solution to deal with the water scarcity problem.