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Why do people continue to think boiling their water will remove nasty farm chemicals and radioactive contamination and make it perfectly safe to drink. Getting chemicals, organisims, and all kinds of pollutants out of your drinking water requires the water be evaporated off and re collected. This is a design and discussion of a high capacity, enhanced vaporation solar still that can be folded or broken down flat for storage and put together in short order in case of emergency.
The top diagram is how to cut a 4x8 foot sheet of plywood or aluminum to make this solar still with no waste material.
The center diagram is how to lay out all the pieces so that all of the 4 foot edges touch and so that the 5.6 foot edges of the top and bottom are pointing out. The dotted line down the "right" side piece is where the two right side pieces are joined together to form the right side. Use the brace along this joing and screw firmly together.
If you simply bevel the edges and hinge them together as shown in the second figure, and also bring the top and right sides together and hinging them as well, the entire structure will fold flat with one large and one small triangle on top and the other large and small triangle on bottom.
I changed the labels of what I was calling the sides and the top/bottom after I put together one of these, originally I envisioned it standing tall and narrow, but with it laying horizontally it is more stable and also offers a 45 degree slope for the glass, where in the vertical orientation it was more shallow. The water will run better at the 45 degree angle.
You can also fit this together tounge-and-grove. Just grove the top and bottom pieces to accept the sides and then either permenantly screw the whole thing together or use a dowel-and-hole design to pin it together in a collapsable (although not foldable) frame.
Next you must treat the entire structure throughly with water sealer if you are using wood. The wood must not take on water.
Most designs have reflective surfaces for the top and sides (or transparent sides), but I've come up with a better approach. You can glue aluminum foil to the top in order to reflect more light into the water, but the sides and bottom should have dark burlap stapled to them with good overlaping contact between the sides and bottom. Water will be drawn up the burlap sides, drasticall inreasing the surface area of the water and greatly increasing the performance of this still. The burlap surface area isn't just more surface, it's increased evaporation surface. Next time the dog pees on the kitchen floor, drop a paper towel on it and leave it for half an hour, it will evaporate very quickly, and water in this still will evaporate much more quickly than just leaving it sitting in the bottom. For increased performance put some crushed styrofoam under the sheet of burlap on the bottom pane and allow the burlap to float on top of the water when you fill the still. Wet burlap on the surface will cause much more evaporation than plain water.
If you turn the design sideways and shrink it to 2 feet on the short side you can cut four small solar stills out of a single sheet of plywood as shown in the bottom picture. This way you only have to cut one of the right side triangles in half. Note the side triangles are equalateral, each side is 2 feet in the small version or 4 feet in the large version, exactly the same as the smaller sides of the top and bottom pieces. The large version will have a 4 x 5.6 feet sheet of glass or plexiglass in the front, for a total of over 22 square feet of glass. The smaller versions with 2 foot triangles will have a sheet of glass 2 x 2.8 feet for a surface area of 5.6 square feet. Multiply by 4 and it's the same square footage of glass as one large still. Interesting, I had expected the math to work out in favor of one larger still vs. four smaller ones but it's actually the same either way. Go figure.
The best way to hold the glass is to route back the corner all the way around such that the glass can be placed in the opening and then calk in front of it to hold it in place just like a house window. You could also run a narrow groove a quarter inch from the edge all the way around the inside front just thick enough to fit the sheet of glass or plexiglass and then fit the glass into the grove as it's assembled.
I haven't diagrammed it but you need to run a piece of wood (a 1x2 or something) edge to edge along the front about a half inch back from the glass and waterproof around it. This piece is called the Dam. Don't let the burlap get under this piece, keep the burlap to the back of the still. In front of this piece of wood is where the fresh water will collect, you want to keep the fresh water pure, don't let the gray water from any of the burlap drip or draw into the fresh water. Tap a small water line into the fresh water well to draw off the fresh water as it collects. Drill a hole in the top of the still about a third of the way from the back to allow gray water to be poured in, put a screw top or a cork plug in this hole. Waterproof here and anywhere else where you cut the wood after previously waterproofing.
Obviousy it won't fold flat any more after you add the dam. You'll have to pull that back out to fold it up and store it. You can just bolt it down if you want to make it removeable. Silicone selant or calk will due to waterproof it when it's in use. Same with the glass, you can pull these out of storage folded flat, bolt the 1x2 water well board in place, calk the glass into the front, and put it into the sun. When I claimed this design folded flat I didn't mean like for camping trips, it all folds or breaks down into almost nothing for long term storage but it takes some lite assempbly to put it together when needed. You can make these part of your emergency water supply and leave them folded flat against a corner of the garage taking up almost no space, then when you need them you can snap them together in short order and have fresh clean water. Probably the folding design isn't worth the extra effort, I'm going to stick with the tounge and grove assembly with screws to hold it together. I'll take the screws back out if I want to put it back in storage. If you really wanted a folding version you could work out a way to make the dam fold flat, maybe make it out of sheet metal, maybe put a rubber gasket along the bottom so it's removeable but waterproof. If you do make it fold flat it's about as long and wide as the original sheet of plywood or aluminum that it's cut from.
Remember, shiny aluminum foil on the top, dark burlap stapled firmly to the sides but just loose across the bottom with a handful of crushed styrofoam or packing peanuts under the bottom piece to make it float on the water. If you use hinges then you better get everything snug to keep the water vapor in.
If you use this design or a variation on it, please give me a link back to Dave's Planet from your web site. Thanks!
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