My daughter sent me a link to this YouTube video, since she knows I like sustainable, low-tech ideas like these.
Made from 1.5 liter Coke bottles, 2 cap-fuls of bleach and tap water, they are able to provide lighting to people who would otherwise live in the dark. They are made from recycled materials, are solar powered, and only need replacing every five years. I think the bleach keeps algae from growing in the tap water, which will eventually cloud the water. The only drawback is they do not work without sunlight, but since the families perpetually live in very dark areas, even in the daytime, having the solar water bottles is a big improvement for them.
This is the nonprofit organization in the Philippines is helping provide families who have no electricity with indoor lighting: http://isanglitrongliwanag.org/.
In the event of a lengthy power grid power failure, it doesn’t hurt to know about a variety of lighting sources such as this one.