Environmental Science/solar energy


Hi David,
I am a chemical engineer in Iran and want to work on solar stills. I have two books in this field but each of them has few pages on this issue. I am looking for more sources. I am at the beginning of the way and have to raise my knowledge. Would you help me and recommend me what to do?Do you a person or company or something else that has worked on this title? I need others experience to avoid wasting time.
Best regards

The fundamental problem with solar stills is the source of energy-- the sun.  In a batch process spread out over a day or two, it resolves itself into a mirror reflectivity problem with some concentration. As a continuous process you have an uncontrollable challenge called clouds. As you know, they can block the sunlight and reduce the performance of your solar still.
Here is one link to solar still information: http://www.solaqua.com/solstilbas.html
Here is another: http://solar.smps.us/solar-energy.html
I'm sure it's pretty basic and beneath what you need.
I would look into the following idea. Consider a large parabolic frame made of light gauge wood or fiberglass.  Coat the inside of the frame with silver foil (high reflectivity).  Then take a 15 cm ID pipe of black iron or stainless steel (stainless is preferred if you coat it black), and run it along the focus of your new solar collector.
Depending upon the size and the construction of your mirror, you won't need to be all that precise in the alignment of the pipe, and the focal point will be an area rather than a point.  That should suffice.
At noon, about 1000 W/M2 reaches the earth. If you had a collecting mirror made from a standard sheet of plywood, approximately 1.3 long and about 2 m wide across the top of the mirror, you would have about 2600 Watts of energy, and allowing for inefficiencies of 50%, that's still about 1300 watts per 1.3 meters, or about 1000 watts per meter of piping.  The specific heat of water is 2264 KJ/Kg.  or 2264 J/gm
If we assume the ambient temperature rise and the heat of vaporization would require about 3000 j, that means that you could run about 1/3 of a gram per second through the solar still we just discussed, and while that's not much, it amounts to about 20 grams/minute, or 1200 gm/Hr. It's not much, but the water is totally vaporized into steam and you would have to cool it down to ambient, and periodically clean out the salts. The advantage is that you have invested very little in cost except for the aluminized foil lining which is available from a number of sources such as: http://www.dunmore.com/products/metallized-films.html
And there is your inexpensive solar still. 1.3 meters wide, 2m across the top, with a production of 1.2Kg of steam per hour which you can condense and have drinking water.
Hope that helps.

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David L. Russell, PE


I`m a Chemical,Civil and Environmental Engineer and have a number of projects in all phases of the environment. I have worked in the chemical industry and am active in professional societies, and am currently on an industrial wastes committee for the Water Environment Federation, and have taught courses in remediation in the US and abroad. I have written one book on Remediation of petroleum Contaminated Sites, and have a second book on PRACTICAL WASTEWATER TREATMENT to be published by John Wiley in September, 2006. I've also written over 30 articles on various elements of environmental problems and cleanup. Most Recently, I have addressed a NATO Scientific and Techical Conference on Ecoterrorism, and have worked with the same group on remediation of sites contaminated with Chemical Warfare Agent materials and othe materials as well. . I can answer q`s about Chemical and Environmental Engineering, land development, air pollution, water pollution, soil and water cleanup, combustion, international environmental problems, industrial processes chemical processes. Civil and Environmental and Chemical Engineering. Overall, I have over 35 years of experience in this area. Note: I do not answer homework questions


I love work in the third world and developing areas because it is challenging and one can get a sense of accomplishment.

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