Desalination For Hydration
Madeleine Lilly, Samantha Chisham
Point Grey Secondary
Floor Location : J 187 N

We wanted to focus on water desalination and how to make a fresh water producing water bottle because fresh water shortage is a serious problem the world is facing. We tested our hypothesis by running several experiments. Our first experiment used jars, which we discovered were too small and the wrong shape. For our second experiment, we used several different bowls and beakers sized much larger than the jars. We heated the saline solution to a range of temperatures from 30 to 50 degrees Celsius. We then put the articles outside in the cold for a fixed amount of time to let the water condense, and measured how much water was collected in each sample. This gave us data about the effect of bottle size and water temperature on the rate of water production. Our experiments showed that the water bottle needs to be larger in order to collect enough fresh water, and it also showed that temperature cycles are required to evaporate and condense the water. The first experiment was conducted at a constant warm temperature, and without a natural cooling cycle no water condensed. The data showed that the amount of water condensing depends on the free (i.e. not containing water) volume of the container, and the peak temperature of the water prior to the cooling cycle. Higher temperature water and a bigger volume results in more water vapour in the bottle and therefore more condensed water for each cooling cycle. The shape of the lid is also a key design factor. The lid must have a steep enough angle leading to the collection chamber for the condensed droplets to roll down and collect. As well, the sides must be steep so the water does not have a chance to condense on them, only on the top where they can be directed to a centre cup and collected. An ideal design for a desalination water bottle using the evaporation condensation method is a large volume container with materials and design selected to concentrate the sun’s heat as much as possible. A lid designed to have a space to put cold seawater to act as a cooling device would allow for more than one cooling cycle per day. Our analysis concluded that in order to provide enough water for a person to survive (2-3 litres per day), the water bottle must be approximately 2667 litres in volume if a water temperature of 40C can be achieved through a design that concentrates the solar heat of the liquid to that temperature. With a lid designed to provide five cooling cycles per day, the volume could be reduced to 533 litres. Therefore the conclusion is that the concept works, but the water bottle would be too large for a person to carry around. It may be a suitable device for someone living by the ocean in a warm climate