If you follow the news of the world, whether it be politics, health, science, or business, you’ve likely heard of the dwindling supply of safe, clean drinking water.  Throughout the world, growing populations and contamination of watersheds, the air and general stupidity, by the human race, puts millions of people, possibly billions, in jeopardy of losing access to potable water.  And if you’ve gotten to know anything about me, you know i have a solution and you know it’s the SUN!

Solar stills, that is a “water distillation system” that uses the heat and light(arguably the UV light helps kill biohazards) from the sun to evaporate water from sea water or other non-potable sources and condense the pure H₂O into liquid that is collected to drink. The concept of a solar still is well known as a survival tool.  A most basic solar still can be built with a large (1 sq meter ) piece of black plastic, and a can/cup to collect the water.  Dig a hole in a sunny area, 18-36″ deep and place the cup at bottom center of the hole and cover the hole with the black plastic.  With a small stone weighting the plastic down into a cone shape, with the point of the cone directly over the water collector (the can or cup).  Secure the outside edge around the outside of the whole with rocks or wood.  During the day, the heat of the sun will evaporate water out of the ground, it will condense on the inside of the black plastic and drip inside the cup.  A square meter(about a sqare yard) of area can generate a litre of water a day.

Emeril might say “Let’s kick that up a few notches” and that would be a permanent, large scale solar still. Think of a short, glass, greenhouse covering a concrete storm drain with gutters on the side.  So build a concrete “drainage canal”, in the shape of a V, so that we maximize the surface area exposed to the sun, we make this canal 8 feet wide, with 1 foot gutters on each side, cover the today 10 foot width, with a glass, vapor capturing roof.  Then run this canal a few miles thru a desert/hot area and run seawater thru the center canal.  The sun heats the water, the water evaporates, the water vapor, condenses on the glass sealing which peaks in the middle, causing the condensed water to drop to run down the glass sealing to the edges, with then lead to the gutters.  The water captured in the gutters is salt free. 

here is a little drawing:

So, how does solar distilation cut greenhouse gas?  Well, the main cost of producing and distributing drinking water is energy.  It may take as much as 7% of world energy to produce and deliver fresh water to the world.  It takes from 5kWh to 25kWh to desalinate 1000 litre of water.  In theory a system like this could be driven by gravity and use no energy, except that needed to build the facilities.  Anywhere there is unusable desert or semi desert land, there is both space for solar distillation and likely a need for the resulting fresh water.

This entry was posted on Tuesday, April 3rd, 2007 at 10:38 am and is filed under Conservation, Global Warming. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.