|CARRUTHERS (United Kingdom)|
Small Scale Desalination Dome
There are many types of solar powered desalinators being suggested, some even patented, but the one I am considering should be cheapest to build and run for very small scale or local uses, and easiest to use in areas of strong sunlight and salt water supply, such as coastal areas or brackish lakes.
A dome of clear material is placed over a pool of saline water, such as on a quiet coastal strip or brackish lake. The edges of the dome are submerged to several inches but is open underneath.
Inside the dome a mat black ceramic tile is placed angled so the flat facing is towards the prevailing sunlight direction. At the top of the dome a tube is connected and is angled towards the ground some distance away. At the other end of the tube, preferably below ground level, is a cooling radiator, and collection sump. These are protected from the sun but, like a weather station may be open to the winds. The radiator extends upwards and projects a couple of meters above the ground level to catch the winds.
At the opening to the tube, just at the top of the dome, is an impeller or fan, which is connected to a small fan on the outside of the tube.
The impeller is also connected to a small pump and tube inside the dome, behind the ceramic plate, that takes water from the saline pool and discharges onto the top of the tile.
Sunlight heats up the air in the dome and the black ceramic plate until it becomes hot enough to boil a thin film of water passing across its surface.
A combination of winds on the external fan, and internal pressure increase from the heated air within the dome, turns the impeller and activates the pump to pump a small amount of salt water up the pipe and discharges it across the face of the ceramic tile.
As the water on the tile evaporates into steam, the increased pressure drives the impeller in the tube and pumps more water onto the tile. The flow of water on the tile washes away any salt residue to keep the tile clean.
Steam from the dome flows down the tube from the impeller to the cooling radiators, held below ground level or protected under a cover. Winds, and the effect of cooler temperatures at sub-ground levels, condenses the steam which collects in the sump, ready for collection or piping away for use. Excess heat is lost to the atmosphere through the elevated radiator surfaces.
By being open ended at below the water surface the design allows the concentrated saline to flow away from the dome, whilst the salt water level keeps a pressure seal for the domes atmosphere to heat up and expand through the tube and impeller.