Dr. S S Verma
For human beings, nothing can replace water and drinking water has always been in demand with the increasing population. Though, water covers around two-thirds of the earth’s surface but water is still a scarce resource as only 1% of world’s water is available as drinking water. With due availability of land and air all around, civilizations before have always moved/expanded in search of required drinking water. Drinking water based on water cycle of earth (ocean-heat evaporation-cloud-rain-ocean) and then available from natural resources on earth is dwindling with time due to many reasons along with increasing population. People have already shifted to the use of smart technologies to transport, clean, uplift drinking water from other different sources but all these water resource technologies have their own geographic region specific limitations in general and for hilly and desert regions in particular. Earth’s atmosphere holds six times more fresh water than all of its rivers combined, so, if it is possible technologically to harvest that water, in areas where people have no other fresh water source, can prove to be a wonder. Atmospheric water extracting devices extract potable water from the air, either through condensation, exposing the air to desiccants (water-absorbing substances), or by pressurizing the air. With the development of science and technology, scientists and engineers are proposing different technologies to extract water from thin air (from fog) which will help people in getting enough drinking water at location specific with low cost. There are four main methods for extracting water from the atmosphere:
Fog nets: setting up physical nets in humid environments to collect the water in the air
Dew plates: using temperature differences to encourage water to condense on metal plates
Sorbents: using chemicals to absorb water from the air, and then heating the material to extract the water
Membranes: using vapor-selective membranes that extract water as air passes over them
This article will briefly present some of the emerging technologies proposed and being used also in many places to extract water from thin air.
Fog collector/Fog net:
A fog collector looks similar to the boundary nets used to stop errant balls on the edges of sports fields. The fog net is a multilayered mesh designed to attract and accumulate the water particles in places where ocean-born fog is common. These are made of food-safe materials (metals/fabricks) nets, are quick and easy to install while requiring no maintenance, are carbon-neutral as they are operated without energy producing high-quality drinking water and can provide water for agriculture and forestry. Fog is simply a cloud that touches the ground when
warm, damp air cools (called condensation). Fog is very common both in coastal regions and mountainous areas. Wind drives the fog into the vertically suspended nets. The droplets are caught in the 3D mesh and merge into larger drops, which then fall into the collecting trough below. From there the fog water is piped into a reservoir. The amounts yielded per fog-day differ according to region and season. A fog collector can also be a very good rain collector, because, wind-blown rain always falls at an angle on the nets. Each project begins with a study to determine whether conditions on site are suitable for fog harvesting. Fog collectors have been erected in Africa, South America and Germany. The goal is to continuously improve, develop and use fog net technology even further.
Fog harp
Scientists are developing an entirely different fog collection strategy modeled after the Stenocara beetle of the Namib Desert. When the fog sweeps in, the dime-sized Stenocara beetle clambers up the dunes, sticks his rear end into the air and faces his back to the fog. The configuration of hydrophilic (water-loving)
bumps and hydrophobic (water-repellent) troughs between the bumps. Scientists are developing an entirely different fog collection strategy modeled after the Stenocara beetle of the Namib Desert. When the fog sweeps in, the dime-sized Stenocara beetle clambers up the dunes, sticks his rear end into the air and faces his back to the fog. The configuration of hydrophilic (water-loving) bumps and hydrophobic (water-repellent) troughs between the bumps on his shell collect the moisture and channel water droplets right into the beetle’s mouth. Inspired by nature’s design, scientists have invented a synthetic surface using a combination of chemistry and structure. The surface is composed of two polymer layers: the top is hydrophilic, while the bottom is hydrophobic, which makes water droplets detach as soon as they get large enough. Prototypes have shown that this technology is several times more productive than mesh harvesting methods and could be scaled up to work in urban environments.
Atmospheric water generator (AWG)
An example of a forced condenser-type system, this device works similarly to an air conditioner. To date, these devices have been installed in homes, offices, ranches, and other buildings to dehumidify the air, extract water vapour, and then filter it ready for drinking. According to the manufacturer, the device works by drawing air “through a series of condensing coils, where water vapor is cooled down sufficiently to reach the dew point.
This converts water vapor into droplets.” Each unit then passes the air, and water, through a series of specially patented extraction chambers that have a range of features to further force water condensation. Any and all liquid water is then filtered for potential contaminants (like pathogens, pollen, etc) and then collected in a special storage tank ready for tapping. The device works best in areas with high humidity, like foggy areas or coastlines, and, depending on the size of the unit, it is capable of producing between 200 and 1,900 gallons (900 and 8,600 liters) of water a day. Sadly, these devices are not cheap and the unit also consumes a lot of power. However, different AWGs based on useful technologies are on development process, which will be more economical and energy-efficient.
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