This is a simple but genius invention where plastic bottles filled with filtered water are placed on a carefully cut hole in the roof of a building, creating a free energy light source equivalent to a 50 watt lightbulb. As the plastic bottles are cheap to acquire, it’s a brilliant 3rd world solution to a 3rd world problem for sure. 

[http://www.youtube.com/watch?v=SBWi3NtND68]

How it works? 

The top part of the bottle is positioned on the outside of the roof absorbing sunlight. The bottom part of the bottle hangs inside the building like a normal lightbulb. The water acts as a lens and refractor spreading the light to a wider area inside. As you can imagine this simple idea is perfect for buildings in developing countries where many people live in shanty towns or huts where energy is unaffordable or hard to come by. There are projects implementing these ‘lights’ in Brazil, Indonesia and the Philippines, and the invention most probably derived from one of these places.

One of the drawbacks is that the bottles of water obviously depend on sunlight to work, but if you can imagine a shanty town home, without conventional lightbulbs it’ll be pitch black inside regardless of the time of day.

Relevance to rich countries

As this is a free way to have light energy, this invention can also be used in developed countries too. Just have a look around all the buildings that have lights on during the day time and how much energy is being used. It just takes some good designers to come up with designs that considers the quality of materials used and how it can be fixed on top of buildings. The bigger the bottle the more light it refracts. People in the USA have been using it for their garden sheds and even a church hall has them fitted.

Check out this video to see how these solar light bottles work