This is the VOA Special English Development Report.

More than one and a half billion people around the world live without electricity. Finding better ways to bring light to the poor is the goal of researchers like David Irvine-Halliday.

In the late nineteen nineties, the Canadian professor was working in Nepal when his return flight was cancelled. A delay gave him time to take a fourteen-day hiking trip in the Himalayas.

As he tells it, one day he looked in the window of a school and noticed how dark it was. This is a common problem for millions of children around the world -- and not just at school, but also at home.

Many families use kerosene oil lamps. There are many problems with these lamps. They produce only a small amount of light. They are dangerous to breathe. And they are a big fire danger, causing many injuries and deaths each year.

Kerosene costs less than other forms of lighting, but it is still costly in poor countries.

Professor Irvine-Halliday says many people spend well over one hundred dollars a year on the fuel.

When he returned to Canada, he began researching ways to provide safe, clean and affordable lighting.

He began experimenting with light-emitting diodes, L.E.D.s, at his laboratory at the University of Calgary in Alberta. As a professor of renewable energy, he already knew about the technology.

Light-emitting diodes are small glass lamps that use much less electricity than traditional bulbs and last much longer.

Professor Irvine-Halliday used a one-watt bright white L.E.D. made in Japan. He found it on the Internet and connected it to a bicycle-powered generator.

He remembers thinking it was so bright, a child could read by the light of a single diode.

In two thousand, after much research and many experiments, he returned to Nepal to put the systems into homes. His Light Up the World Foundation has now equipped the homes of twenty-five thousand people in fifty-one countries.

He says the one-time cost of the system is less than one hundred dollars. So one year of kerosene would pay for a solid-state lighting system.

Now his aim is to develop a lower-cost lighting system. In January, David Irvine-Halliday left the University of Calgary. He has also decided to give up leadership in the Light Up the World Foundation to start a company in India.

And that's the VOA Special English Development Report.