What do you get when you combine sunshine, water, and chlorine inside a used one-liter plastic bottle? For Illac Diaz, a social entrepreneur from the Philippines, this simple technology is a means of bringing cheap light to disadvantaged Filipinos and recycling tons of plastic waste that would otherwise end up in already-overburdened landfills.

“We have to design for the grassroots,” Diaz says — and he proves it with the "Liter of Light," as his eco-friendly bottle lamp has come to be known. Always made from locally available or scavenged empty bottles, the lamp is suspended from ceilings, where during daylight hours the water inside the bottle refracts natural sunlight to produce a light equivalent to a 55-watt solar bulb — which then extends for another 10 hours at night.

Originally developed for Brazil by mechanic Alfredo Moser, the Liter of Light has brightened 140,000 homes in the Philippines alone since 2011, and has spread to roughly 15 other countries, including India, Bangladesh, and Nepal. Diaz has set a goal of one million bottle lights installed worldwide by 2015.