FAQ - Frequently Asked Questions
What is fog?
In our context, fog describes the phenomenon of small water droplets (1 to 40 micrometres in diameter) dispersed in the air. Fog is a kind of cloud that touches the ground or mountain terrain. Fog can be dense and reduce visibility to far less than one kilometre.
What does fog collection mean in general?
Fog collection describes the process of water harvesting or production from fog. For this purpose, large arrays of mesh, so-called fog nets, are arranged vertically in places where wind drives fog through them. The water sticks and accumulates in the mesh fibres and drips down into a collection and pipeline system.
We essentially distinguish here between two types of fog collectors - the simple 1st generation fog collector developed by Canadian NGO FogQuest (founder and director Bob Schemenauer), and the technology 2.0 fog collector (CloudFisher) developed by German company aqualonis GmbH (CEO Peter Trautwein).
What are the necessary conditions for fog collection?
The prerequisites for fog collection are fog and wind. Dew and humid air are alone not sufficient to collect water. Whether local conditions are suitable for harvesting fog must be identified by means of scientific assessment and by performing pilot studies using a small test collector. Validated methods exist.
For what purpose is fog water collected?
The main purpose of fog harvesting nowadays is drinking water supply. Beyond that, the water can also be used for irrigation, plants, livestock and crop farming. A number of current projects include farming aspects, but plugging the gaps in drinking water supply is the dominant application. Another positive effect is an overall reduction in the use of contaminated water resources.
How does a simple (FogQuest) fog collector work? What are the pros and cons?
This fog collector uses very simple and affordable meshing that is put up between two poles. The collector is easy to construct and comparatively cheap. It collects a moderate amount of fog water. Unfortunately, this technology is very prone to being destroyed in windy conditions - occurring quite often in mountainous regions where fog harvesting works best. Furthermore, aspects such as food grades and damage by strong solar radiation are often underestimated in very simple and cheap constructions.
What are the main differences between the two types of fog collectors?
The main differences between the two types are the mesh composition and quality, the collector construction (frames, grids, water gutters, etc.) and the price. The CloudFisher is more efficient and has the more sustainable construction, while simple collectors are easier to construct and cheaper. Wind conditions are a key element when deciding which technology should be used or is more successful.
How big are fog nets and how are they typically arranged?
A typical large (FogQuest) fog collector has a 40 m² net surface, the net surface of a CloudFisher measures 54 m² and has a height of 6 metres. Since wind and fog are the conditions necessary for fog collection, fog nets are typically arranged on the windward slopes of mountains where they are directly oriented towards persistent winds. Orientation is a key factor because diverging by only 30° from the wind direction results in a 25% lower yield. To reduce obstructions to the wind, it is useful to spread a number of collectors over a certain area instead of placing big ones close to each other.
How much water can be collected?
Water collection yields vary a lot depending on local conditions and year. The annual average yield of simple collectors is around 5 litres per square metre, whilst the CloudFisher average, in Morocco for example, is more than 20 litres per square metre and fog day. The daily yield per installation depends on the technology used, the weather conditions and the size of the fog collectors. Since the quality of water droplet density, etc. varies a great deal, pilot studies (see above) are necessary.
Is electricity required for fog collection?
No electricity is required to collect fog. Fog collection is a passive technology that combines weather conditions (wind) and physics (gravity).
What are the initial steps in starting a fog collection project?
After securing an enabling environment (people in need, administration, regulation, commitment of beneficiaries; even better: involvement of the community, etc.), feasibility of fog collection in the desired area must be assessed. To do this, climate conditions must be measured and small test collectors installed (see above).
Is water collected clean and declared potable?
Yes, since atmospheric water is normally free of bacteria and contamination. It is safe. In all existing projects, fog water has met WHO drinking water standards. As with all other water sources and systems, pipes and storage facilities must be cleaned regularly. Also, contamination by bird droppings for example must be prevented.
Is it possible to collect rain?
Yes, fog collectors can also collect rain - when the rain arrives with wind and so falls at an appropriate angle.
What are the average costs for a fog collection project?
The costs for a project vary greatly and depend on the technology selected, and the size and yield required. According to FogQuest, a simple 40 m² fog collector costs about USD 1,500 producing an average of about 200 litres of water per day. A 54 m² CloudFisher that, in Morocco, produces an average yield of about 1,200 litres of water per fog day costs about €11,000.
Where can I buy the materials required for a fog collector?
The main suppliers of fog nets are FogQuest (simple nets) and aqualonis GmbH (CloudFisher). For further information, refer to their websites (www.fogquest.org and www.aqualonis.com).
Is fog collection sustainable?
As long as the fog collectors are maintained properly and the systems are kept clean, fog collection can be a very sustainable solution. The CloudFisher nets in particular can operate for many years. Moreover, fog collection does not have any harmful environmental impact and can foster socioeconomic factors such as female labour force participation and education through saved time.
Is it possible to provide enough water for a city?
No, since water demand in cities is much too high for a fog collection system. The design is very well suited for remote mountain communities and smaller villages. In Morocco, the world’s biggest fog net plant with 31 CloudFishers provides water for 16 small villages.
What are the key benefits?
The water is clean.
The water is accessible.
Environmental impact is minimal.
Construction of fog collectors requires only basic technical skills.
The systems are passive and so do not need further energy.
Fog collection reaches remote mountain communities and villages.
Cost-benefit analyses indicate that the price for water compared to methods usually used (such as selling water from tanker trucks) is cheap.
The social impact is high – girls do not have to fetch water every day from sources far away for example.
Maintenance can be performed by the community itself.
What are the key downsides?
Suitable conditions are restricted to selected regions in the world.
Water output is limited and not feasible for larger conurbations or cities.
The identification process for good locations can be protracted (long evaluation phase with test collectors).
If there is no fog, there is no water.
What represent obstacles to implementation?
Where fog is a seasonal source, water has to be stored in large quantities for dry season use (tanks, cisterns).
If not properly maintained, water quality becomes an issue during low-flow periods.
Fog water collection requires specific environmental and topographical conditions, limiting its application to specific regions.
Procurement and transportation of materials might be difficult in remote locations and e.g. steep terrain in mountainous areas.
Water yield is not easy to predict, necessitating feasibility studies prior to large-scale implementations.