Tuesday, November 18, 2008
Cheap Low-Tech Desalination Using a Greenhouse
Water, Water, everywhere, but just .5% to drink!
The world is facing a serious clean water shortage and scientists everywhere are hard at work on solutions, but too often the solutions are so expensive that they are out of reach for the people who need them. One simple solution is to change a problem into a solution.
I have had many greenhouses over the years, and I can tell you a major problem is condensation. High humidity can cause fungus in many crops, and it is no fun to work in a greenhouse when you are being rained on! But if the goal is to harvest water then that problem can be turned into a solution.
In this example, a very simple hoop house can provide the heat needed to extract water from wet soil, brackish ponds or even the ocean. The sun warms the air inside the hoop and causes the water to be evaporated. The condensation collects on the ceiling and runs down the walls into a channel where it can be pumped into a reservoir. On land, as the moisture inside is depleted, more nasty water can be added. This step is not needed for a floating system.
Advantages of this system.
1) Very low tech and low cost.
2) Suitable for use in tropical climates. The more sun it gets the faster it makes clean water.
3) Moisture additions can be salty, water laden plant materials or even animal or human waste buried under a layer of soil.
4) Floating system would not damage sealife since only a small percentage of surface area is covered.
5) This system can be erected in 1-2 days by 2 people for about $24.00. It would last up to 3 years and produce up to 100 gallons a day(at 80 F. outside temperature)
6) Inside temperature would be 140 F.-150 F. effectively pasteurizing the water and preventing most fungus, & bacteria including tuberculosis, diphtheria, polio, salmonella, strep throat, scarlet fever, and typhoid fever.