PET bottle filled with water and bleach, refracts sunlight to illuminate

Did you ever think that the empty PET soft drink bottles you throw can actually brighten homes and light up people’s lives? Yes, you read that right.  A slum just behind IIT Delhi, Munirka, where even sunlight inside homes seems to be a luxury, electricity is probably a far-fetched dream. The only way seems to be is by stealing power from the nearby electric poles. But close to 200 of the 500 plus shanties in this slum now have light, and they don’t have the govt to thank, but IIT Delhi students. And these bulbs don’t require electricity, but the sunlight above their roof tops to illuminate homes.

Sidharth Ranjan, a final year student of B.Tech & M.Tech dual degree in Electrical Engineering at IIT Delhi, was inspired by the ‘Liter of Light‘. This is a global initiative to convert plastic bottles, using a simple physics concept, to make energy efficient light bulbs. “It’s a very basic concept and extremely feasible. After reading about Liter of Light, I thought this can be implemented in Delhi as well, especially in the slums behind our campus,” says Ranjan. The solar bottle bulb costs Rs 10 to 15 per unit to manufacture, all of which is funded by the management of IIT D. It emits light equivalent to 40-50 watt bulb. The solar bulb lasts for 2-5 years without any sort of maintenance with the change of water at regular intervals. The biggest hurdle was not in making the bulb itself but in convincing the slum dwellers of its benefit.

A shanty in Munirka illuminated by Solar Bottle Bulb

“They were suspicious, and later puzzled about how the bulb will work. We also need to drill holes in the roof to fix them, for which we had a tough time convincing them. It took many rounds of workshops and showing them the process. They have now warmed up to the idea,” says Ranjan. Close to 500 homes are now illuminated by this Bottle Bulb. There was a lot of uneasiness about leakages due to drilling and the effectiveness of the bulb itself, but Ranjan and his team have put all their apprehensions to rest, and managed to convince them.

Sidharth Ranjan, IIT D, spending time with students explaining the process

To popularise this idea, Ranjan, with the help of the IIT Delhi NSS unit aand the Sustainable IIT Delhi group, has taken this initiative further, and involved students from schools and colleges. They are now on a mission to install bins and collect these PET bottles in major cities- a project that is being funded by Reliance Industries Ltd. “Ultimately as engineers, this is way we can make use of technology and benefit the society.” he concluded.