The solar water purifier collects heat from sunlight and uses it to evaporate unpurified water running through the panel. The vapour collects inside the glass forming the panel’s surface and is collected - leaving behind most impurities. Margaret Folkard and John Ward’s inspiration behind inventing the Solar Water Purifier has been effect of polluted water and water-borne diseases on the health and life expectancy of the population, young people in particular.
Let’s begin with a description of the appearance of the product. The Solar Water Purifier is a rectangular shaped unit that contains an array of 32 shallow, square trays interconnected by a series of weaves. The trays are made from a black plastic sheet that is vacuum formed onto an aluminium pattern to reach the desired cell shapes. The panel of cells is covered by a sheet of white-glass and sealed using the surface tensions of water vapour produced in the unit. The undersides of the black plastic trays have been thermally insulated to maximise heat absorption. The unit is framed by an aluminium mount for strength and to keep shadowing to a minimum. It is also fitted with folding legs, so that the entire system is inclined at 12.5º to the horizontal.
How it works : Polluted water is fed into the unit and cascades down, filling the trays. The sun’s radiated heat shines through the glass onto the water. The sun rays are only partially absorbed by the water and then more completely by the black plastic lining of each cell which in turn heats the water more.
As the water is heated to 85º, water vapor condenses on the inside surface of the glass and runs down into the purified water channel into a collection container. The unique design of the cells maximizes heat absorption and condensation which increases the pure water output.
The ultra-violet radiation from the sun combined with prolonged exposure times prove to be extremely effective for killing commonly occurring bacteria and other water borne diseases.
Other pollutants do not evaporate and are flushed away in unpurified water into a chamber called the ‘overflow channel’. Virtually none of the dissolved solid waste is collected in the trays. If the SWP is being used consistently there should be no build up at all. If solid impure material has been collected in the trays, the hardened deposit can be easily removed by using a diluted acid solution such as citric acid (or lemon juice).
The water output of the unit can be maximized when it is correctly positioned to the sun. John recommends rotating the unit every 30 minutes or so throughout the day, so its shadow is underneath itself, effectively tracking the sun. This will increase the output by about 30%.
The cell geometry maximizes the resultant condensation and high yields of pure water are obtained. Multiple units can be connected in a series to produce larger volumes of water.
The Solar Water Purifier can produce about 6 liters of pure water per square meter per day at 20ºC ambient and 9 liters at 35ºC. So an individual unit (which is 1/3 m²) can produce up to 3 liters per day.
The plus points are many. The Solar Water Purifier uses direct sunlight to convert any source of contaminated water – seawater, bore water, effluent, wine – into drinkable water. It uses no filters, no electronics, has no moving parts, rarely needs cleaning, uses no chemicals to purify water and gives a greater yield than existing solar purifiers.
To obtain even greater purified water output, several sets of 12x Array SWP systems can be banked together. The banked arrays can all be supplied from a single impure input water feed tank. The Clean Water output for a 12x array system operating in Southern Australia can produce on average 30 - 40 litres of pure water at an ambient temperature of 35° C Clean Water Output at a latitude of 20° from the equator from a 12x array may be around 50 to 60 litres at an ambient temperature between 35°C and 40°C. The SWP Panels have been engineered to international standards, using components that maintain quality of purified water and withstand a range of environment conditions.
This innovative water purifying device is being distributed worldwide by Charity Rotary International.
Via: New Scientist
