Fresh water from the sea: designing a solar still

Your challenge is to design a solar still that uses the Sun’s heat to turn salt water into fresh water. A good design needs three places: one to hold the salt water, one where water can evaporate and then condense, and one to collect the fresh water. A simple design is a wide bowl with salt water in it. A small empty cup stands in the middle, with its top below the rim of the bowl. Plastic wrap covers the bowl and is held down tightly with tape. A small clean weight sits on the wrap over the cup. The Sun warms the bowl, water evaporates, the vapour condenses on the cooler wrap, and drops run down to the lowest point and fall into the cup. Each person first sketches an idea alone. Then the team compares, chooses one, and draws a detailed blueprint that lists each material and its job. Four roles help: a team captain, a materials manager, an engineer and a reporter.