Solar still
The pure water vapour condenses on the cool inside surface and drips into a tank.
In 1952, the United States military developed a portable solar still for pilots stranded in the ocean.
[1] Similar stills are included in some life raft survival kits, though manual reverse osmosis desalinators have mostly replaced them.
[2] Today, a method for gathering water in moisture traps is taught within the Argentinian Army for use by specialist units expected to conduct extended patrols of more than a week's duration in the Andes' arid border areas.
The branches are long enough to extend over the edge of the pit and form a funnel to direct the water into the collector.
A solar still can be constructed with two–four stones, plastic film or transparent glass, a central weight to make the funnel and a container for the condensate.
Unless relieved the vapour pressure around the branch can rise so high that the leaves can no longer transpire, requiring the water to be removed frequently.
When distilling brine or other polluted water, adding a dye can increase the amount of solar radiation absorbed.
It features an inverted cone on top to deflect ambient heat in the air, and to keep sunlight off the upper surface of the box.
Residual heat that is not reflected is reemitted in a specific (infrared) wavelength so that it passes through the atmosphere into space.
[9] In desert environments water needs can exceed 3.8 litres (1 US gal) per day for a person at rest, while still production may average only 240 millilitres (8 US fl oz).
[10] Solar stills are used in cases where rain, piped, or well water is impractical, such as in remote homes or during power outages.
[11] In subtropical hurricane target areas that can lose power for days, solar distillation can provide an alternative source of clean water.
Solar is still affordable, eco-friendly, and considered an effective method amongst other conventional distillation techniques.
This makes them ideal for use in rural areas or developing countries where access to clean water is limited.
[1] Using a condensation trap to distill urine will remove the urea and salt, recycling the body's water.
