Though its really not as glamorous an environmental issue as some of the others out there (no high profile wind turbines, no hockey stick graphs and Keynote slideshows) access to clean drinking water is a major problem for many of the world’s people. Now a relatively simple device called the Solvatten hopes to provide a solution to the issue. Though I’m not really sure it's accurate to call it a solar-powered device, at least in the sense that most people would conceive it, here’s how it works:Sun Purifies Water in 3-4 Hours
Similar to a standard jerrycan, the Solvatten can hold 10 liters of water, divided into two 5 liter compartments, each with a clear face. When you open the device and place it in the sun, exposing the two chambers to sunlight. This heats the water to 50-60°C, killing any pathogens which are present in a few hours. An indicator signals when the water is safe to drink (it changes from red to green). The whole process takes 3-4 hours in sunny conditions and 5-6 hours if it is cloudy.
video showing how the Solvatten works and experiences in Nepal using the device: Solvatten