Mistcatcher

The fog catchers or fog catchers are a system to trap the microscopic water droplets contained in the fog. They are used in desert regions with the presence of fog, such as the Atacama Desert in Chile, Ecuador, Guatemala, Peru, Nepal, Israel, and some African countries.

Scientific foundations

Fog catcher is the name of a process known as condensation, atmospheric water vapor in the air naturally condenses on cold surfaces into droplets of liquid water known as dew.

The phenomenon is most observable on thin, flat, exposed objects including plant leaves and blades of grass.

As the exposed surface cools by radiating its heat toward the sky, atmospheric moisture condenses at a faster rate than it can evaporate, resulting in the formation of water droplets.

Historical origins

The organized collection of water droplets from dew or mist through natural or assisted processes is an ancient practice, from small-scale dew drops to condensation puddles collected on the stems of a plant (still practiced today by survivalists), to large-scale natural irrigation in areas without rain, such as in the Atacama Desert and the Namib.

Various artificial devices such as ancient stone cairns in Ukraine, "dew ponds" Medieval stones in the south of England or the volcanic stone that covers the crops in the fields of Lanzarote have all been taken into account to make dew or fog collection devices possible.

In Chile

The Atacama Desert is the driest in the world; however, on its coasts, humid air masses from the Pacific Ocean form morning fogs or advection fogs, locally called camanchacas.

Since the 1960s, various researchers had conceived the use of water in the Camanchacas. Above all, the work done by Carlos Espinosa Arancibia, a physicist from the University of Chile who obtained an invention patent (No. 18,424) for a device intended to “capture water contained in fogs or camanchacas” stands out. He then donated his invention to the Universidad Católica del Norte and encouraged its free dissemination through UNESCO.

The equipment was a 0.7 m diameter cylinder in which 1,300 Perlon monofilaments of 0.5 mm diameter and 2 m long were arranged. At the bottom of this system was a metal funnel and a water accumulation pond. Then came a series of improvements and Carlos Espinosa Arancibia is recognized worldwide as one of the fathers of this invention.

The fog catchers used in the towns of northern Chile were developed in conjunction with Israeli scientists. They are made up of a metal pedestal on which there is a large frame, about 6 m long by 4 m high. This frame contains a plastic mesh that facilitates fog condensation. In its lower part there is a channel and a collecting pond.

These devices are installed in high places that are exposed to camanchaca and are connected by pipes to water storage tanks.

In Chile, the first habitable place where fog catchers were installed was the town of Chungungo, 73 km north of the city of La Serena.

In fog catchers, the expected water capture yields range from 2 to 10 [L/m²day].

In recent studies carried out in Mexico it has been determined that the distribution of fog drops is not homogeneous, that the most abundant are 30 to 40 (one micron is equivalent to one millionth of a meter), and that each cloud is made up of hundreds of thousands of them.

In the case of fog, which is a cloud with a low concentration of water, there are between 50 and one hundred droplets in a cubic centimeter

In the Canary Islands

Since the 80s of the XX century there have been numerous experiences carried out in the Canary Islands that, due to their conditions geo-climatic, present the ideal conditions for the collection of fogs, with the influence of the "sea of clouds" for much of the year, especially on the higher altitude islands. Most of these investigations were carried out with flat or Chilean-type collectors by researchers such as Luis Santana Pérez and Mª Victoria Marzol Jaén (University of La Laguna).

In 2008 and on the island of Tenerife, the agricultural engineer Theo Hernando Olmo, devised and patented the three-dimensional fog, dew and precipitation collectors, NRP 3.0 ((M.U. 200801154).). These fog catchers are prism-shaped and have several superimposed layers of collector meshes, which allow greater structural stability and expose a large amount of collector surface while taking up minimal space. To reduce possible damage caused by strong winds, these collectors were initially designed with a hinge system at their base so that they could be knocked down. Currently, these protection systems have evolved into a pulley system that allows the meshes to be collected to protect the entire fog catcher.

These collectors allowed the creation of the first bottled water in the world from fog, Alisos, obtained from the peaks of the island of Gran Canaria (Agua de Niebla de Canarias S.L., 2011-2015). Currently, the water is produced in Tenerife under the name Garoé, referring to the sacred tree of the island of El Hierro and the company that produces it is Agualternativa Ingeniería S.L. (agualternativa.com), directed by Theo Hernando.

The best conditions to capture fog water occur above 1000 meters of altitude and with wind speeds of between 25 and 35 kilometers per hour, since "the greater the number of cubic meters of air than passes through the collector, more liters of water are collected. A single collector can collect more than 500 liters of water in a day, although the average ranges between 180 and 230 liters per day.

Other uses of these fog catchers in the Canary Islands have been the supply of forest deposits for preventive work against fires, reforestation, etc.

In Peru

The desert around the city of Lima in Peru is one of the driest in the world, but during the Peruvian winter, dense fogs form in the Pacific Ocean that cross it almost daily. Giving the sky in the Lima area a perennial gray color, cloudy that does not provide rain, known as "donkey's belly."

Starting in February 2015 in the hills south of Lima, an initiative proposes installing 1,000 "mist catchers" to collect up to 400,000 liters of water a day and supply families in extreme poverty with water for drinking and irrigation of orchards for their own supply.

The fog catchers are located in the Villa Lourdes Ecológica Human Settlement, a neighborhood of extreme poverty in the Villa María del Triunfo district, in the south of Lima, the second largest city in the world, after Cairo, located in middle of a desert