Litre of Light solar bottle bulb

MyShelter Foundation with students from Massachusetts Institute of Technology takes old plastic bottles, fills them with water and a capful of bleach – to prevent the build-up of algae – and embeds them in a piece of corrugated metal. This device is then inserted into a carefully-cut hole in the roof and sealed to prevent leaking during heavy rainfall. The bright Philippines sun is refracted through the water and penetrates the room below, illuminating it with the equivalent of a 50 watt bulb.

Source: World Architecture News