After downing a bottle of water, most people are probably inclined to toss it in the trash. Those people, however, don't realize that they're throwing away an ingenious means of lighting a home. Thanks to the ideas of a mechanic in Brazil, such “garbage” can bring light to homes in poor communities around the world.
How does a plastic bottle turn into a source of light? The answer  is both simple and brilliant. A small hole is cut in the roof of a house and a transparent, plastic bottle with clear water is fitted in. During the day, the sunlight is refracted  by the water bottle and spreads 360 degrees around the room. These “lights” are usually installed in urban slums and narrow alleys, where lighting is typically poor or absent entirely. When necessary, some residents do use electric lights during the daytime, but money is tight and a water bottle in the sunlight has the power of a 60-watt bulb . Adding bleach to the water makes it cleaner and clearer, and each bottle can last up to five years before corrosion finally claims it for the scrapheap.
The invention belongs to Brazilian mechanic Alfredo Moser , and the “Liter of Light ” project later adopted it on a large scale in Manila, where it used water bottles to provide sustainable, environmentally clean lighting to impoverished homes. Within a year of its inception, Liter of Light installed over 200,000 bottle lights. The organization aims to brighten up a million homes by 2015. The project is also working on a solar-powered, battery-attached version to provide lighting at night. It has also designed a mobile app  that gives installation instructions.
Back in 2011, when the Green Cupboards blog ran an article on Liter of Light , a reader commented that this idea would make a great difference in India.
This is the most ingenious invention ever and surely needs great acclaim. I live in India where the villages have no electricity and the people have to rely upon kerosene lamps, many time staying in the dark because kerosene is usually in short supply. Hopefully some NGOs will latch on to this and make the life of the villagers less grim.
It took a few years, but Liter of Light is now active in 15 countries, including Bangladesh and Kenya, as well as India . Liter of Light’s India chapter engages volunteers in larger cities like Mumbai, Bangalore, and Hyderabad. A message on the “Liter of Light – Bangalore” Facebook page  urges people to donate their used plastic bottles to the organization, rather than throw them in the garbage.
Please don't throw those Cola bottles away. Do contact us and we will try to find ways to pick it up from the nearest possible place
Writing on Twitter, Pollinate Energy , another non-profit organization that develops clean-energy products for India's urban slums, recently congratulated the Liter of Light team for their good work.
@literoflighthq  you're doing great work!
— Pollinate Energy (@PollinateEnergy) May 6, 2014 
Other NGOs, such as the Sanskar India Foundation and Labour Education and Research Network  (LEARN), are working with Liter of Light India to amplify the impact these bottles have on users’ lives.
Volunteer efforts are the heart of Liter of Light. A volunteer in Bangalore, Tripti, explains what drives the group :
We are eager to touch many more lives and lighten up the city in collaboration with like-minded organizations who want to take up this green movement with us.
Facts About India  reports that 288 million Indians have no access to electricity. An innovative solution like Liter of Light could mitigate the consequences of powerlessness, while putting to good use what was previously just plastic waste.