The idea is as simple as it is effective. Ordinary plastic bottles are recycled and turned into solar bottle bulbs. This is done by filling bottles with water and a drop of bleach and next, installing the bottles in the roofs of huts in a slum. When the sun light shines through the bottle, the water spreads the light. Light as bright as a 55 watt light bulb is generated. Temperature-resistant glue ensures that the solar bottle bulb is waterproof and stays in place.