Fog harvester delivers first results
Since November 2013, a large-scale test system consisting of six fog collectors has been in place on the top of Mount Boutmezguida in Morocco. The goal: to extract drinking water from fog and dew. Now, at the end of the fog season in June 2014, the first results have become available - they are impressive.
The improvement of fog net technology with the most simple means possible and at low costs: this is the goal pursued by the Ebenhausen Water Foundation in cooperation with Munich-based industrial designer Peter Trautwein. He worked for more than 18 months on the method of harvesting drinking water from fog and has developed a new collector. His fog harvester now stands at an elevation of 1,225 metres in the Anti-Atlas Mountains. It will provide critical insights into the best structural design and the most effective mesh materials. Mesh fabrics, posts, steel cables and rubber expanders will be tested under extreme weather conditions and at wind speeds of up to 120 km/h. Munich Re Foundation supported its installation with funding and organised important contacts in Morocco, especially to project partner Dar Si Hmad.
What's new about this fog harvester?
No wind, no water. It's the wind that drives the suspended water drops into the collector. To literally take the wind out of the sails and reduce its destructive powers, Peter Trautwein reduced the original surface area of the nets from 40 m² to just 9 m². Six of these small nets were installed side by side, stretched across metal frames, each attached with rubber expanders. Six different kinds of mesh material and structure have been employed, from simple so-called Raschel net textile that has been used for years in fog nets, to three-dimensional high-tech fabrics. A sturdy plastic grid supports the delicate fabric and braces the net from behind against the wind. The dynamic net holders are also new. The new net structure with rubber expanders is no longer rigid and inflexible but now pliant and at the same time abrasion- and weather-resistant The drip trays are made of flexible, food-grade poly-ethylene, they are elastic and move in the wind. All materials used are UV-resistant, as not only the force of the wind but also the solar radiation is not to be underestimated.
Prof. Annette Menzel, Department for Ecoclimatology at the TU Munich, and her team are conducting the scientific research for the fog net project. During the last fog season from December 2013 to June 2014, the water yields, wind speeds and direction, temperature and relative humidity on top of Boutmezguida were measured on a daily basis. The TU Munich was able to purchase the requisite measuring instruments with our financial support. TU employees worked together with the Water Foundation team and local volunteers to install tipping counters, anemometers and the requisite data loggers. The latter automatically transmit the readings data to Munich. This is important. Technical failures are detected immediately.
Things did not always proceed smoothly: sand in the fog water led to tipping counter failures, problems occurred while reading out the data, a technical error in the data logger was only noticed at a later stage. After overcoming the initial difficulties and six months of data collection and analysis, Prof. Menzel and her staff are justifiably proud of the results of their research work. Within the framework of the project to date, two bachelor theses have been successfully completed and have provided important insights into net types, yields and suspension methods.
Eagerly awaited by all the project partners, the first evaluations of the water volumes obtained are now available. They clearly show that three of the six nets tested consistently deliver the highest water yields. They are about one third higher than from the Raschel nets previously used. This is a very impressive and satisfying result: especially considering the fact that every additional litre of water means a valuable improvement of life quality for humans and animals.
The quality of the fog water was also analysed in detail. It is much cleaner than the water from the well which so far has served as the sole source of drinking water. A surprise for everyone was the low mineral content in the fog water. This value apparently depends strongly on the location of the nets. No problem, say the experts: they had already been planning to mix the fog water with groundwater from the region. This will balance out the low values.
The next move now for Peter Trautwein and the Water Foundation will be to continue and improve. He is already travelling back to the project area again at the end of October 2014. The TU Munich is also still involved. Structural design details are being improved, rubber expanders replaced, collecting troughs enlarged. Data loggers and net meshes are being replaced by new ones. The fog harvester should deliver even stronger yields. When it really goes into action in 2015, everything must be perfect.
JEL, 30 October 2014