What are the efficient ways to light up homes of the poor people in day light?

The Liter of Light project was launched six months ago by the My Shelter Foundation, a Philippines-based NGO which aims to provide light to 1 million of the roughly 12 million homes who are either still without light in their dark homes with no ventilation.

The scheme uses plastic bottles filled with a solution of bleached water, installed into holes made in shanty towns' corrugated iron roofs, which then refracts the equivalent of 55W of sunlight into the room – during the day, at least. It takes five minutes to make, and using a hammer, rivet, metal sheets, sandpaper and epoxy, it costs $1 to produce.

Eduardo Carillo, a resident in one of Metro Manila's many impoverished areas, said: "Before we had the bottle light, the walkways to our house were so dark and going inside made it even darker. The children are no longer scared – they are happy now and they laugh because they can play inside during the day instead of playing in the streets."

The idea of using plastic bottles as a light source is not a new one - it was developed in Brazil by Alfredo Moser in 2002. But with the help of a group of MIT students, the solar bulb used in the Philippines has been modified to meet local needs.

https://www.theguardian.com/environment/2011/dec/23/sunlight-bulbs-plastic-bottles-light