In the slums of Manila, an innovative project is shedding light on the city's dim and dreary shanties. Plastic bottles jut from the roofs, bringing light to the dark dwellings below. The technology is as simple as it could be. Each bottle contains water and bleach. When placed snugly into a purpose-built hole in the roof, the home-made bulb refracts and spreads sunlight, illuminating the room beneath. Eco-entrepreneur Illac Diaz is behind the project. SOUNDBITE: ILAC DIAZ, ISANG LITRONG LIWANAG (A LITER OF LIGHT) PROJECT, SAYING (ENGLISH) "What happens is, the light goes through the bottle, basically a window on the roof, and then goes inside the water. Unlike a hole which the light will travel in a straight line, the water will refract it to go vertical, horizontal, 360 degrees of 55 watts to 60 watts of clear light, almost 10 months of the year." The initiative, known as "A liter of light", aims to bring sustainable energy practices to poor communities, an idea originally developed by students at Massachusetts Institute of Technology. The bottles are designed to emit clear light for about five years, as the bleach prevents algae from building up in the water. For Erlinda Densing, a mother of eight, the technology has made a big difference to her small home. SOUNDBITE: ERLINDA DENSING, RESIDENT OF PAYATAS COMMUNITY, SAYING (FILIPINO) "'That's only water?!' my neighbours were asking. 'That's only water!' I said to them. Basically, the sun's rays are really bright. A lot of neighbours came and got curious. They were like, 'can we see? can we see?'. Maybe they also wanted to have lights installed. 'It's really bright,' I said." The device can be built and installed in less than an hour. A sheet of corrugated iron serves as a support structure to hold the bottle in place, and prevent any leakage. SOUNDBITE: ILAC DIAZ, ISANG LITRONG LIWANAG (A LITER OF LIGHT) PROJECT, SAYING (ENGLISH) "Liter of Light, lights up the house, saves a lot, but at the same time improves the standard of living across the board, of the bottom 90 per cent of this country." Working with low-income communities, local governments and private partners, the project has installed more than 10,000 bottle lights across Manila and the nearby province of Laguna. Rey del Mundo is a volunteer. SOUNDBITE: REY DEL MUNDO, PROJECT VOLUNTEER AND ENERGY UNIT HEAD AT SCHNEIDER ELECTRONICS, SAYING (FILIPINO) "This is very important. Because at present, we're too dependent on fuel that we don't produce. Although we have some local production, it's not sufficient for our needs. So if we strive to develop alternative sources of energy, which are the energy sources, this will help our country a lot." For residents, it means less money spent on electricity to power lights during the daytime, and more money on food. While for Diaz and his volunteers it's quite simply a bright idea. Gemma Haines, Reuters.