Every once and while, some brilliant soul comes up with such an clever solution to a problem, it's simplicity and perfection is awe inspiring. Things are commonly accessible, but not common sense. Coupled with the fact that this one improves the lives of third world persons and saves energy they don't have to spare, I think this might be my favorite DIY project of the year.
In the Sitio Maligaya region of the Phillipines, the homes are often covered with fluted or corrugated sheet metal for roofs. Which means, their homes are pretty dark. While many have electricity, many do not, and those that do don't want to use it to power light bulbs to light their homes.
So, the clever "Solar Demi" created a way to bring light into their homes with something that's essential free: empty plastic drink bottles. The results are amazing, and cost very little to build, and nothing to maintain. See how it works in the video below: