A "light bulb" now exists that does not use any conventional energy.
Introducing the Solar Bottle Bulb -- an alternative source of daylight powered by the sun. It is made from an old soda bottle. By filling it with water and sealing it into the roof, the water refracts the sun's rays and provides about 55 watts of light to a darkened room.
This video introduces you to the village of Sitio Matigaya in the Philippines where hundreds of these bottles have been installed. The villagers are saving money on electric bills, and literally seeing a big difference in their lives.
This was invented in 2006 by students at the Massachusetts Institute of Technology (MIT). It can be built and installed in less than 1 hour, and uses inexpensive or recycled materials. The water is mixed with some bleach and does not need replacing for about 2 years.
The organization Myshelter Foundation plans to light up a million homes in the Philippines by 2010!