Alfredo Moser's invention is lighting up the world. In 2002, the Brazilian mechanic had a light-bulb moment and came up with a way of illuminating his house during the day without electricity - using nothing more than plastic bottles filled with water and a tiny bit of bleach.In the last two years his innovation has spread throughout the world. It is expected to be in one million homes by early next year.So how does it work? Simple refraction of sunlight, explains Moser, as he fills an empty two-litre plastic bottle.

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