The fog net represents a low-tech response to the challenge of water scarcity in arid regions that experience frequent ground fog. These vertical mesh structures are strategically placed to intercept airborne moisture, providing a sustainable source of potable water without requiring external energy. The technology is particularly relevant in coastal deserts and mountainous areas where cool, moist air masses frequently blanket the landscape. This localized solution transforms the atmospheric phenomenon of fog into a reliable, harvested resource.
The Science Behind Fog Harvesting
Fog is a cloud at ground level, consisting of microscopic water droplets. For a net to be effective, it must capture these tiny droplets without impeding the wind flow that carries them. The process relies on impaction and coalescence, where wind pushes the fog through a fine-mesh material, causing droplets to physically collide with the net’s fibers.
Once a droplet collides, it adheres to the surface due to surface tension. As more droplets impact the fiber, they merge into larger, heavier drops. Some modern nets are bio-inspired, mimicking the Namib Desert beetle’s alternating hydrophilic and hydrophobic bumps to encourage rapid runoff. When the accumulated water mass overcomes surface tension, gravity pulls the drops down the mesh and into a collection gutter below.
Global Deployment and Application
Ideal environments for fog harvesting are arid locations situated near cold ocean currents or high-altitude areas where ground-level clouds are regular. This combination of dry land and atmospheric moisture makes specific coastal deserts prime candidates. For example, the camanchacas fog in the Atacama Desert of Chile and Peru has been a long-standing target for collection projects.
A significant application is found in the Anti-Atlas Mountains of Morocco, near Sidi Ifni, where a large project provides water to remote Berber villages. These projects deliver a tangible community impact, raising the daily water supply per person from 8 liters to 18 liters. The installations provide water for drinking, sanitation, and modest irrigation, supporting small-scale agriculture and reforestation efforts in barren areas.
Structural Design and Maintenance
Fog nets are constructed as large, vertical panels supported by a framework of posts and guy wires. They are oriented perpendicular to the prevailing wind direction to maximize capture. The netting is commonly made from durable, weather-resistant materials such as polypropylene or nylon mesh. A specific type known as Raschel mesh is often used due to its optimal fiber density and aperture size.
A major engineering consideration is ensuring the structures withstand high winds, which can easily damage standard netting. Resilient designs, such as the German-developed CloudFisher system, incorporate flexible elements like rubber expanders to distribute wind energy across the net. This allows the structure to withstand gusts up to 120 km/h.
Maintenance involves routine cleaning to prevent the buildup of dust or organic matter, and replacement of mesh panels, which have a limited lifespan. Periodic inspection of the collection troughs and simple filtration systems is also required.
Scaling Up Water Collection
Fog collection technology is a sustainable, long-term water solution that can be scaled beyond single community projects. Compared to high-energy alternatives like desalination, fog nets offer a cost-effective and energy-efficient method of water production. The water collected is generally clean, requiring only basic filtration or treatment to meet potable standards.
The future involves integrating large-scale fog farms into existing regional water infrastructure, such as channeling the harvested water into municipal cisterns and pipeline networks. Innovations are also leading to the development of massive networks, such as those in the Taklamakan Desert, where extensive systems are capable of gathering thousands of liters of water daily. This approach ensures a stable, decentralized water source that helps secure livelihoods and combat desertification.