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Home Made Solar Water Distiller

A few years ago a storm flooded the local water treatment facility leaving me and all my neighborswithout water for several weeks. Partially motivated by this I designed a portable solar poweredwater distiller. The idea is that a person adds water from any source (assumed to be dirty, salty orotherwise unfit for drinking) in one side and over the course of the day gets clean safe drinkingwater out the other side.

At the heart of this design is an innovative method for forming a medium size parabolic mirrorusing a flexible aluminized mylar sheet (the shiny metallic foil commonly used to make potato chipbags/decorative balloons). I built an aluminum frame, using 1 inch wide by 1/8 inch thick strips,

that runs around the edge of the mirror and use a pair of wires at either end to draw the frame upinto a parabola. The mirror is actually sandwiched between an upper frame and a lower frame. Thismylar sheet, frame and wire construction makes a good parabola, is inexpensive, lightweight, andcan be easily assembled/disassembled.

The aluminum frame is much stronger than necessary (& more expensive) and could easily be made

out of a cheap local material like wood or plastic. The function of the frame is to 1) hold/capture themylar sheet, and 2) provide some stiffness so the wire stays taught. The wire length determines howsteep or shallow the parabola is, which in turn determines how close/far the focus of the mirror is

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from the mirror surface. The mirror is cheap (a few dollars) and ideally the frame should only cost afew more, altogether Id guess it should cost under $10 to make the mirrors in any serious volume(maybe $10-$15 in moderate volume). I say should, because Im still working with a prototype, anda custom job costs at least 10 times what I think the cost should be Still I imagine a big cheapmirror can be useful in any number of solar applications besides water purification.

The mirror is placed under an evaporation chamber where the water is purified. The evaporationchamber has an aluminum pan (painted black to absorb the sunlight/heat) into which I add a trickleof dirty water which is heated until it evaporates. This pan has a clear plastic cover which capturesand condenses the water vapor as well as an interior lip that channels this pure/condensed water outof the distiller. The two piece evaporation chamber can be taken apart for cleaning or storage. At the

moment the parabolic mirror needs to be adjusted by hand each hour to keep the sunlight focusedon the pan, although this tracking could be automated fairly simply by adding a small motor.

In the interest of keeping the device portable, Ive only used a 2 square meter mirror which distills ~1 gallon of water/day. Im working to boost the treated volume by a factor of two with additionaldesign improvementsin theory a mirror this size could distill 4 gallons/day. I could also increasethe distilled water production volume by using a larger mirror, doubling the mirror would doublethe production, although it would be that much harder to transport. The device weighs about 40 lbs,and the mirror can be rolled up like a poster.

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In fact my big problem at this time is that Im collecting too much sunlight/heat onto the pan andthe plastic cover gets so hot (60-70 degrees C) that the water vapor doesnt condense as well as itshould. The little metal fins at the top of the distiller are designed to help remove heat from thecondensing cover. For scale, the mirror is 6 ft. x 4 ft. and the evaporation chamber is roughly 3 feetoff the ground.

This is a fairly simple device. Ive spent a few years working and improving the design almostentirely on my own. Last year I filed for a US patent on it, so the design is officially patent pending.Id be delighted if some person or group found a situation in a developing/island country where thisdistiller would be useful (and Id be happy to help in any way I canadapting the design for localconstruction with local materials etc.), but I dont want some major US corporation copying theidea, filing for a patent and potentially preventing me from using my invention!

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