Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.
Evacuated tubes are made from two layers of glasses. The inside glass is coated and the space between the glasses is evacuated. When sun radiations pass through the first layer and transfer heat to the inner side, since the space between them is evacuated it cannot cool down with convection or conduction. The common way of using an evacuated tube is to put an evacuated copper rod inside it to heat up and make contact with a water container to let the water boil. In the current study water is directly inside the inner evacuated tubes. Thus, the evaporation happens in these tubes and there is no need to use a water container or copper rods. Results show that when the amount of water is increased in the tubes the production raises significantly. Result for two values of volume of water in two days with acceptable similar solar radiation and ambient temperature are reported.