Residents in the Philippines have taken a soda bottle filled with water, some flashing, and some ingenuity to create a 55-watt equivalent light source in the dark shacks that are so prevalent in the poor parts of the world. The shacks are dark during the day and many of the individuals can’t afford much. Taking any food grade bottle, filling it with distilled water and inserting it into the corrugated metal roof, they create a refracted light source. By using the bottle, the sunlight hits the water and scatters in multiple directions (or refracts), thus giving a light bulb effect without the heat or cost of traditional electric light during the daylight hours.
You can read more and donate at isanglitrongliwanag.org