What is a Bottle Bulb ??
The concept is simple. Each plastic bottle contains filtered water and bleach. When placed snugly into a hole in the roof, the homemade bulb refracts and spreads light illuminating the room. This simple yet novel idea refracts the light in 36o degrees, providing light to an equivalent of an astounding 55-60 w light bulb. From the incandescant tungsten filament bulb invented by Edison to the state of the art LED bulbs, their average life is 2 to 3 years. However the bottle bulb lasts for about 5 years and the bottle could still be re-used with having to replace only the bleach and water inside. This is done to prevent any possible buildup of algae. This device could be built within an hours time even by a novice. The one hour includes even the installation, which could be done using an ordinary sheet of corrugated iron which serves as a support for the bulb.
With simple tutorials given, the local communities of the Manila city in Philippines such as Sitio Miligaya and the neighbouring province of San Pedro in Laguna  have installed over an amazing 10,000 bottle lines of these novel solar bulbs. Reid Del Hondu a volunteer of this Solar initiative, says that this novel idea lessens our dependency on the fuel which we produce. This novel idea has helped millions of financially challenged people in small cities like Manila of Philippines, cut down the redundant costs on electricity and channel that money towards the basic needs as per Maslows Hierarchy being food , clothing and shelter.
Another inconspicuous aspect of this technology is that it uses plastic bottles which are non-biodegradable. Thus using them we are not only recycling the waste plastic bottles which would harm the environment but also shedding light across millions of homes which are financially challenged.
This ingenious idea stems from two basic yet fundamental concepts of physics. The first being Snell’s Law and the second being total internal reflection.
When light moving through the air runs into a denser material like water, it changes direction. That is, the light beam kinks where it encounters the water surface so that it’s traveling more directly down into water. This is very helpful if you are trying to get more light to go down through the hole. However, during much of the day, the light will strike the cylinder walls in such a way that lots of light will be reflected down toward the hole. This is called total internal reflection. Light reflected this way will bounce back and forth as it travels down through the water column, much like signals passing through an optical cable.
After the solar bulb is installed in the roof, this is how much light will be gathered.
Because of multiple reflections and different paths caused by Snell’s Law refraction and internal reflection, light spreads out as it passes through the water column. That’s what makes the bottles appear to glow in the video of Solar Demi doing his stuff.
Green Technology at grass root levels :
Green technology which has its foundation paved out of Renewable resources has been rampant only to places where wealth is in exuberance. However the need of the hour is that there needs to be a sudden spurt in the green technology in the downtrodden areas. It is really sad that there are places in the cities of Asia where having light indoors is a luxury. My shelter foundation is a non profit organization in Philippines which started this initiative with its sole aim of taking the green technology to the grassroot levels. This ingenious idea is not patented persay. However it dates back to 2002 where a mechanic named Alfred Moser  came up with this revolutionary Solar bottle due to frequent powercuts. It soon took the neighbourhood by a storm. Alfred Mosers solar bottle used chlorine as the fluid inside. The idea was later fine tuned by a few students from M.I.T ( Massachussets Institute of Technology ) replacing chlorine with beach and filtered water. The movement called Isang Litrong Liwanag— A Liter of Light — is the perfect grassroots campaign. The movemen has brought light into a whopping 28,000 homes and has been a boon to the lives of 70,000 people in the Metro Manila alone. This movement has now extended to other countries like India, Indonesia and even Switzerland.