This is a beautiful example of the simplest idea making a difference in people lives. The slums of the Philippines hav the curious anomaly of almost constant sunshine and no light in people homes. running lightbulbs through the day is incredibly costly to already impoverished people. The solution: a cap full of chlorine, a plastic bottle and a hole in the roof, comparable light to a 50watt light bulb. Genius.
http://reut.rs/prA7tA