More than 1.3 billion people, or approximately one-fifth of the world’s population, live without access to an electrical grid. That is roughly five times the number of people living in the United States, a country that is so plugged-in that access to electricity is all but taken for granted.

In places without electricity, kerosene has become the most common option for lighting. But kerosene is dangerous, dirty, expensive, and inefficient. People who burn kerosene, wood, and other fuels for energy face dire health consequences, including burns and respiratory disease. (See related story: “Five Surprising Facts About Energy Poverty.”)

Alternative energy sources exist, but it is a challenge to get them into the hands of the global poor. National Geographic has