  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.
