Fog as a Fresh-Water Resource: Overview and Perspectives

Abstract

The collection of fog water is a simple and sustainable technology to obtain fresh water for afforestation, gardening, and as a drinking water source for human and animal consumption. In regions where fresh water is sparse and fog frequently occurs, it is feasible to set up a passive mesh system for fog water collection. The mesh is directly exposed to the atmosphere, and the foggy air is pushed through the mesh by the wind. Fog droplets are deposited on the mesh, combine to form larger droplets, and run down passing into a storage tank. Fog water collection rates vary dramatically from site to site but yearly averages from 3 to 10 l m -2 of mesh per day are typical of operational projects. The scope of this article is to review fog collection projects worldwide, to analyze factors of success, and to evaluate the prospects of this technology.

Optimal Design of Permeable Fiber Network Structures for Fog Harvesting

“…We compare the magnitude of the gravitational body force F grav  ρ water gr drop 3 with the pinning force arising from [3] where the coefficient B = 1− cosθ ( ) sinθ (see Supporting Information for additional details). For an ideal fog-collecting surface, liquid droplets convected towards the mesh and deposited on the surface will be drained quickly by gravity into the collecting gutter without loss by reentrainment to the airflow, thus refreshing the base mesh surface for capture of new fog droplets.…”

“…3,[5][6][7] A Standard Fog Collector consisting of 1m 2 of double-layered Raschel mesh is typically deployed. 6 Water collection rates ranging from 10 -1  /m 2 /day to 10 1  /m 2 /day have been reported for various locations and fog conditions.…”

“…6 Water collection rates ranging from 10 -1  /m 2 /day to 10 1  /m 2 /day have been reported for various locations and fog conditions. 3 Researchers have also investigated the influence of the width of the mesh fibers ( 2R ), the shade coefficient ( SC , i.e. the fractional area coverage), and the composition of the mesh material on the fog harvesting efficiency.…”

Fog Water Collection: Challenges beyond Technology

“…Volunteer labor; production and distribution costs [24] It is important to note as well that even when water has been collected from nearby wells or cisterns without direct financial barrier, the cost has often been paid in the form of women's time, labor, and poor health. Besides satisfying water demand in water scarce areas, the value of fog collection projects is also reflected in the form of social and human capital, and by the marked reduction in the time that is spent on water collection and transportation from long distances [30]. Other indirect economic benefits are associated with relief from paying private water providers, avoiding exposure to waterborne diseases that are related to conventional storage and distribution systems, and the potential to use the increased water and time availability on other income-generating activities.…”

“…For example, the transfer of project control to the community without required management capacity could cause system malfunctions and lead to disappointment and a lack of motivation to continue with the project. Instead, local institutions can extend the time that it takes to implement and transfer a project to the local community only once the required level of skills and motivation are reached, and the adequate sustainability training and capacity are in place [30].…”