Brizilian mechanic created a light bulb from old water bottles filled with bleach. 

Alfredo Moser’s cheap and environmentally friendly invention is picking up steam in developing nations around the world. The 'Moser lamp' was picked up by the Liter of Light campaign and is now brightening 140,000 homes in the Philippines.

So how does it work? Simple refraction of sunlight, explains Moser, as he fills an empty two-litre plastic bottle.

"Add two capfuls of bleach to protect the water so it doesn't turn green [with algae]. The cleaner the bottle, the better," he adds.

Wrapping his face in a cloth he makes a hole in a roof tile with a drill. Then, from the bottom upwards, he pushes the bottle into the newly-made hole.

"You fix the bottle in with polyester resin. Even when it rains, the roof never leaks - not one drop."

"An engineer came and measured the light," he says. "It depends on how strong the sun is but it's more or less 40 to 60 watts," he says.