Electric street lamps are expensive. They are expensive to make, to maintain and to illuminate. However, cities are undoubtedly safer with them. So what to do in poorer countries?

Liter of Light, an NGO that focuses on illuminating the developing world without electricity, has figured out a way to light streets using soda bottles. In Bogota, Colombia, university students work hard to install these lights:

The lights’ beauty lies in theirsimplicity: A3-watt LED lamp is connected to a controller and a battery pack, which is powered by a small solar panel. Thelight fixture’s protective casingisan old plastic soda bottle. Each lampcosts around 176,000 Colombian pesos ($70) to build, and nothing to run. Parts are sourced locally and the battery can power the lamp for three consecutive nights without charging. pleted, the students install the lights throughout the neighbourhood, brightening dimly lit alleyways and dark clearings.

Illac Diaz is the founder of Liter of Light, and an MIT graduate. He founded the NGO in his native Philippines, and used his creation to light more than 28,000 homes in Manila before moving on to other places around the globe. Diaz says its important that his lighting technology is open-source and easy to replicate. In this way, lighting can quickly be made available in even very remote areas and during emergencies.

During an emergency if you want a thousand lights, it takes five months to order them from China or India and another two or three months to bring it over by ship,’ says Diaz. Once installed, lights are prone to break after a year or two, and without someone on hand to repair them, the expensive technology es redundant.

Liter of Light is trying to devolve and simplify the process. It share its designs with everyone, publishing how-to videos on YouTube that munities to build their own lights. The parts are cheap and the circuit board can be made using a marker pen. The NGO now has 53 chapters around the world, who between them have installed over 250,000 bottle lights and over 15,000 night lights. Each chapter is self-sufficient: Illac Diaz had only met the Colombian team once before and has never met the organisers in Ethiopia.

Lighting is important not just for safety. Children need light in order to study. In addition, many homes in the developing world use kerosene for lighting, and in enclosed spaces, this creates a health hazard; kerosene increases the occurrence of asthma, bronchitis and pneumonia in both children and adults. Diaz says lighting can also help local economies: shops can stay open longer, and people are more likely to shop when market areas are safely lit.

Read more of this story at Quartz.