This innovative technology is based on the fact that water can be collected from fogs under favorable climatic conditions. Fogs are defined spil a mass of water vapor condensed into petite water droplets at, or just above, the Earth’s surface. The puny water droplets present ter the fog precipitate when they come te voeling with objects. The frequent fogs that occur te the arid coastal areas of Peru and Chile are traditionally known spil camanchacas. Thesis fogs have the potential to provide an alternative source of freshwater te this otherwise dry region if harvested through the use of ordinary and low-cost collection systems known spil fog collectors. Present research suggests that fog collectors work best te coastal areas where the water can be harvested spil the fog moves inland driven by the wind. However, the technology could also potentially supply water for numerous uses te mountainous areas should the water present te stratocumulus clouds, at altitudes of approximately 400 m to 1 200 m, be harvested.
Full-scale fog collectors are ordinary, vapid, rectangular nets of nylon supported by a postbode at either end and arranged perpendicular to the direction of the prevailing wind. The one used te a pilot-scale project te the El Tofo region of Chile consisted of a single Two m by 24 m panel with a surface area of 48 m Two . Alternatively, the collectors may be more ingewikkeld structures, made up of a series of such collection panels joined together. The number and size of the modules chosen will depend on local topography and the quality of the materials used te the panels. Multiple-unit systems have the advantage of a lower cost vanaf unit of water produced, and the number of panels ter use can be switched spil climatic conditions and request for water vary.
The surface of fog collectors is usually made of fine-mesh nylon or polypropylene netting, e.g., “shade cloth,” locally available ter Chile under the brand name Raschel. Raschel netting (made of vapid, black polypropylene filaments, 1.0 mm broad and 0.1 mm thick, ter a triangular weave) can be produced te varying mesh densities. After testing the efficiency of various mesh densities, the fog collectors used at El Tofo were tooled with Raschel netting providing 35% coverage, mounted ter dual layers. This proportion of polypropylene-surface-to-opening extracts about 30% of the water from the fog passing through the nets.
Spil water collects on the televisiekanaal, the droplets join to form larger drops that fall under the influence of gravity into a trough or gutter at the bottom of the panel, from which it is conveyed to a storage waterreservoir or cistern. The collector itself is totally passive, and the water is conveyed to the storage system by gravity. If webpagina topography permits, the stored water can also be conveyed by gravity to the point of use. The storage and distribution system usually consists of a plastic channel or PVC pipe approximately 110 mm ter middellijn which can be connected to a 20 nun to 25 nun middellijn water hosepipe for conveyance to the storage webpagina/point of use. Storage is usually te a closed concrete cistern. A 30 m Three underground cistern is used te the zone of Antofagasta te northern Chile. The most common type of fog collector is shown ter Figure 6.
Storage facilities should be provided for at least 50% of the expected maximum daily volume of water consumed. However, because the fog phenomenon is not flawlessly regular from day to day, it may be necessary to store extra water to meet requests on days when no fog water is collected. Chlorination of storage tanks may be necessary if the water is used for drinking or cooking purposes.
Fog harvesting has bot investigated for more than thirty years and has bot implemented successfully ter the mountainous coastal areas of Chile (see case investigate ter Part C, Chapter Five), Ecuador, Mexico, and Peru. Because of a similar climate and mountainous conditions, this technology also can be implemented ter other regions spil shown ter Figure 7.
Figure 6: Section of a Typical Plane, Rectangular Nylon Mesh Fog Collector. The water is collected ter a 200 l drum.
Source: G. Soto Alvarez, National Forestry Corporation (CONAF), Antofagasta, Chile.
Te Chile, the National Forestry Corporation (CONAF), the Catholic University of the North, and the Catholic University of Chile are implementing the technology te several regions, including El Toro, Los Nidos, Cerro Moreno, Travesí,a, San Jorge, and Pan den Azú,car. The results of the several experiments conducted ter the northern coastal mountain region indicate the feasibility and applicability of this technology for supplying good-quality water for a multitude of purposes, including potable water and water for commercial, industrial, agricultural, and environmental uses. Thesis experiments were conducted inbetween 1967 and 1988 at altitudes ranging from 530 m to 948 m using different types of fog water collectors. The different types of neblinometers and fog collectors resulted te different water yields under the same climatic conditions and geographic location. A neblinometer or fog collector with a screen containing a dual Raschel (30%) mesh wasgoed the most successful and the one that is presently recommended.
Ter Peru, the National Meteorological and Hydrological Service (SENAMHI) has bot cooperating with the Estratus Company since the 1960s ter implementing the technology ter the following areas: Lachay, Pasamayo, Cerro Campana, Atiquipa, Cerro Orara (Ventinilla-Ancó,n), Cerro Colorado (Villa Marí,a den Triunfo), and Cahuide Recreational Park (Ate-Vitarte), and ter southern Ecuador the Center for Alternative Social Research (CISA) is beginning to work ter the National Park of Machalilla on Cerro Lade Gotera using the Chilean installations spil models.
Operation and Maintenance
Operating this technology is very elementary after once the fog collection system and associated facilities are decently installed. Training of personnel to operate the system might not be necessary if the users participate ter the development and installation of the required equipment. A very significant factor te the successful use of this technology is the establishment of a routine quality control program. This program should address both the fog collection system and the possible contamination of the harvested water, and include the following tasks:
·, Inspection of cable tensions. Loss of decent cable stress can result te water loss by failing to capture the harvested water te the receiving system. It can also cause structural harm to the collector panels.
·, Inspection of cable fasteners. Liberate fasteners ter the collection structure can cause the system to collapse and/or be demolished.
·, Inspection of horizontal mesh televisiekanaal tensions. Liberate nets will lead to a loss of harvesting efficiency and can also pauze lightly.
·, Maintenance of mesh nets. After prolonged use, the nets may rip. Tears should be repaired instantly to avoid having to substitute the entire panel. Algae can also grow on the surface of the mesh nipt after one or two years of use, accumulating dust, which will cloud the collected water and cause offensive taste and odor problems. The mesh netwerken should be cleaned with a soft plastic brush spil soon spil algal growth is detected.
·, Maintenance of collector drains. A screen should be installed at the end of the receiving trough to trapje undesirable materials (insects, plants, and other debris) and prevent contamination of water te the storage waterreservoir. This screen should be studied and cleaned periodically.
·, Maintenance of pipelines and pressure outlets. Pipelines should be kept spil clean spil possible to prevent accumulation of sediments and decomposition of organic matter. Openings along the pipes should be built to facilitate flushing or partial cleaning of the system. Likewise, pressure outlets should be tested and cleaned frequently to avoid accumulation of sediments. Openings ter the system voorwaarde be protected against possible entry of insects and other contaminants.
·, Maintenance of cisterns and storage tanks. Tanks voorwaarde be cleaned periodically with a solution of concentrated calcium chloride to prevent the accumulation of fungi and bacteria on the walls.
·, Monitoring of dissolved chlorine. A decrease ter the concentration of chlorine te potable water is a good indicator of possible growth of microorganisms. Monitoring of the dissolved chlorine will help to prevent the development of bacterial problems.
Figure 7: Locations Where Fog Harvesting Has Bot or Can Be Implemented.
Source: W. Canto Vera, et reeds. 1993. Fog Water Collection System. IDRC, Ottawa, Canada.
Level of Involvement
Ter applying this technology, it is strongly recommended that the end users folly participate ter the construction of the project. Community participation will help to reduce the labor cost of building the fog harvesting system, provide the community with operation and maintenance practice, and develop a sense of community ownership and responsibility for the success of the project. Government subsidies, particularly te the initial stages, might be necessary to reduce the cost of constructing and installing the facilities. A cost-sharing treatment could be adopted so that the end users will pay for the pipeline and operating costs, with the government or an outward agency assuming the cost of providing storage and distribution to homes.
Actual costs of fog harvesting systems vary from location to location. Ter a project ter the region of Antofagasta, Chile, the installation cost of a fog collector wasgoed estimated to be $90/m Two of mesh, while, te another project te northern Chile, the cost of a 48 m Two fog collector wasgoed approximately $378 ($225 te materials, $63 ter labor, and $39 te incidentals). This latter system produced a yield of Three.0 l/m Two of mesh/day. The cost of a fog harvesting project constructed ter the village of Chungungo, Chile, is shown te Table Two. The most expensive voorwerp ter this system is the pipeline that carries the water from the fog collection panel to the storage waterreservoir located te the village.
Maintenance and operating costs are relatively low compared to other technologies. Ter the project te Antofagasta, the operation and maintenance cost wasgoed estimated at $600/year. This cost is significantly less than that of the Chungungo project: operating costs te that project were estimated at $Four 740, and maintenance costs at $7 590 (resulting te a total cost of $12 330/year).
Both the capital costs and the operating and maintenance costs are affected by the efficiency of the collection system, the length of the pipeline that carries the water from the collection panels to the storage areas, and the size of the storage waterreservoir. For example, the unit cost for a system with an efficiency of Two.0 l/n^/day wasgoed estimated to be $Four.80/1 0001. If the efficiency wasgoed improved to Five.0 l/m Two /day, then the unit cost would be diminished to $1.90/1 0001. Ter the Antofagasta project, the unit cost of production wasgoed estimated at $1.41/1000 l with a production of Two.Five l/m Two /day.
Table Two Capital Investment Cost and Life Span of Fog Water Collection System Components