The future of our world depends on the education of our youth, who will be tomorrow's leaders. It is the hope of Solar Solutions that this website will be a catalyst for educators to begin a dialog with students about water pollution, the worldwide water crisis, and ways to solve this global problem.
Please visit this section of our website soon, as we will be adding information of value to schools and teachers.
It is the hope of Solar Solutions to partner with schools and universities to provide educational assistance programs for students who wish to pursue studies in passive solar technologies and water purification applications.
Please visit us again soon as we develop more information about this program. For immediate information please contact Solar Solutions.
Do-It-Yourself Free Designs
These design concepts and references will be of help to do-it-yourselfers, students and those wanting to know about solar water purification. This material will be updated periodically, so be sure and check back soon!
Distillation is only necessary when the water source available to you contains salts, minerals, heavy metals, chemicals, and other non-biological contaminants. Distillation also produces more aesthetically pleasing water, eliminating all algae, mud, and other sources of turbidity. However, solar pasteurization yields a lot more portable water than distillation, since it requires less energy.
Unlike our inflatable unit, most solar water distillation devices are mounted on land and are made of metal, glass, hard plastics, and other rigid materials. They consist of a basin to hold raw water, a plate glass cover that is inclined at a shallow angle (about 30 degrees), and a collection tray and tube to gather distilled water. The basin is generally painted black on the inside and the whole unit well sealed and insulated, to ensure that the solar energy coming in is used as efficiently as possible to heat the water. Silicone sealant is generally used as a flexible, airtight caulking material. A shallow basin is preferable to a deep one.
A good do-it-yourself booklet on the subject, with step-by-step instructions, is titled "Solar Still", by W.R. Breslin. It is a available from Volunteers In Technical Assistance (VITA), 1815 N. Lynn St., Suite 200, P.O. Box 12438, Arlington, VA 22209-8438 USA. We have no affiliation with VITA. Please see the reference for other books and information papers on this subject.
A good overview of stills, pasteurizers, and other solar water purification technologies is given in “A Survey of Solar Based Water Treatment", by Adrienne T. Cooper and D. Yogi Goswami of the University of Florida. (Solar Engineering, 1998, The American Society of Mechanical Engineers). Another excellent resource is "An Overview of Water Disinfection in Developing Countries and the Potential for Solar Thermal Water Pasteurization", by Jay Burch and Karen E. Thomas at the National Renewable Energy Laboratory (1998).
This is a great project for teachers who would like to show their students how the process of evaporation and condensation (also known as nature's water cycle) can be used to purify water.
One gallon clear plastic bag, two coat hangers, salt, measuring spoons, a measuring cup, wire cutters, water, an aluminum pie tin, a large jar lid (about three inches in diameter), modeling clay, a twist tie, a plate, a dropper, food coloring, tape, sunny weather.
1. Bend the hangers into shape shown. Using wire cutters, shorten the hanger ends so the framework stands in the pie tin no higher than seven inches. Bind the hangers together at the top with the twist-tie and use clay to hold the ends of the hangers in place at the bottom.
2. Place the lid inside the wire frame cage. Add a teaspoon of salt and three ounces of water. Stir until the salt is dissolved, then add two drops of food coloring.
3. If the plastic bag has a zip closure, cut off that part. Place the bag over the wire frame and secure it to the bottom with tape so no moisture escapes. Set in direct sunlight.
4. Let the model AquaCone sit until all the liquid in the jar is gone. (This may take a few days depending on the weather.) Where is the water now? Does it have salt in it?
5. Place a few drops of water from the pie tin onto a plate and allow them to evaporate? What did you find?
The water evaporated from the lid inside the bag, then ran down onto the pie tin. The salt was left behind. The water on the plate evaporated too, but since the salt and food coloring were left behind in the jar lid, there was nothing left behind when the drops evaporated. Due to the process of evaporation and condensation, pie tin contains only drinkable water.
Our AquaCone uses the same process.
Pasteurization - Solar water pasteurization is the technique of choice when the water that requires purification contains only biological pathogens.
The key to solar water pasteurization is to ensure that the water gets hot enough for long enough time. However, it is difficult to know if the water was actually pasteurized. A device known as the Water Pasteurization Indicator (WAPI) solves this problem. A prototype was developed by Dr. Fred Barrett (USDA, retired) in 1988 and improved in 1992 by Dale Andreatta, an engineering graduate student at the University of California, Berkeley. It is essentially a tube which contains a soybean fat which melts at 69 C. When the fat melts, it flows from the top to the bottom of the tube, which indicates that the water has been pasteurized.
The two low-cost methods of solar water pasteurization that follow are described in detail in a paper by Dale Andreatta and Robert Metcalf. One very easy method of solar water pasteurization is to use a solar box cooker to heat black-painted jars of water with WAPIs inside.
Solar Puddle Cross Section
A large-scale, inexpensive pasteurizer is what is known as a solar puddle (see illustration on the right). To make one, a shallow trench (2m-6m, 6ft.-21ft.) is dug and lined with insulating materials, 50-100mm (2-4") deep. Hay, crumpled paper, grass, etc. all make acceptable insulators. This is lined with black plastic film which is anchored by soil piled on its edges. Raw water is poured into this lined trench to a depth of 25-50mm (1-2"). Two layers of clear plastic film, spaced at least 100mm (4") apart, are then layered atop the water and similarly anchored. The trench is built with a slight slope towards a 25mm (1") depression on one side, from which the water can be siphoned. A WAPI is also placed in this depression. This solar puddle can produce about 480 liters (125 gallons) per day.
Andreatta, Dale and Metcalf, Robert et. al., 1994, "Recent Advances In Devices For The Heat Pasteurization Of Drinking Water In The Developing World", American Institute of Aeronautics and Astronautics (AIAA-94-4027-CP)
(Harp, 1996 Effect of Pasteurization, Environmental Biology)