How it works
Fog collectors are large mesh panels — typically 1 to 40 square metres — positioned perpendicular to prevailing winds in locations where fog or low cloud regularly occurs. As wind-driven fog droplets contact the mesh, they coalesce into larger droplets that run down into collection troughs and storage tanks below.
The principle requires no energy input, no mechanical components, and minimal maintenance. The key variables are mesh material (polypropylene shade cloth is standard; newer 3D-structured meshes like CloudFisher's significantly improve collection efficiency), panel size, wind speed, and fog frequency. FogQuest and CloudFisher (developed by the German Water Foundation) are the most field-tested products globally.
"In the right geography — coastal escarpments, highland ridgelines where clouds form — fog collectors can supply a community with water at a cost per litre that no other technology can match."
Key specifications
Pros & cons
- Zero energy cost — fully passive operation
- Extremely low cost per litre when conditions are met
- Simple enough for community installation and maintenance
- Long operational lifespan with minimal upkeep
- Proven at scale — operational projects in 17+ countries
- No consumables — mesh replacement every 10–15 years
- Highly location-specific — useless without regular fog or low cloud
- Output is intermittent and weather-dependent
- Requires site assessment before any investment commitment
- Wind-exposed sites can damage panels in storms
- Water quality needs monitoring — open collection attracts dust and debris
- Not scalable beyond what local fog patterns can deliver
Field reality
The benchmark case is Morocco's Dar Si Hmad project in the Anti-Atlas mountains — the world's largest operational fog collection system, supplying five villages with potable water from an array of CloudFisher collectors on a ridge at 1,225 metres. The system collects an average of 15–22 litres per square metre of mesh per day during the fog season, providing reliable supply where ground and rainwater are both scarce.
Chile's Atacama coast, Peru's Lomas, and highland sites in Eritrea and South Africa have all produced similar results. The common denominator: a reliable, wind-driven fog regime occurring at a ridge or escarpment where panels can be positioned to intercept it.
The challenge is that fog collection is among the most geography-dependent of all water harvesting approaches. The same technology installed 10 kilometres from a proven site — on the wrong side of a ridge, or at the wrong elevation — can produce almost nothing. A rigorous site assessment including fog frequency data, wind direction analysis, and seasonal variation mapping is non-negotiable before any installation.
Where we recommend it
Fog collection is Aquacapt's recommendation where three conditions are met: a confirmed fog regime (minimum 60–80 foggy days per year), suitable topography (ridge, escarpment, or coastal hillside exposed to prevailing winds), and community capacity to maintain simple infrastructure. In those conditions, no other technology delivers water at lower cost.
We do not recommend fog collection without a prior site assessment. The investment in assessment is trivial compared to deploying a system in a location that will underperform.
Aquacapt verdict
The lowest-cost water harvesting technology available — but only where the geography cooperates. Non-negotiable: conduct a proper fog regime assessment before committing any capital. The upside when conditions are right is exceptional.
Do you have a potential fog collection site?
We can assess fog regime data, topography, and seasonal variation to tell you honestly whether it is worth pursuing.
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