Tens of thousands of people living in disadvantaged areas around the world now have reliable household lighting thanks to Scots-Canadian photonics engineer Dave Irvine-Halliday. For ten years he has been supplying low-cost lighting in developing countries through his foundation, Light Up The World, an achievement that has earned him a Rolex Awards for Enterprise. It is a project with potential to make a huge difference to the world as a whole: each year the kerosene lamps that flare in the homes of the poor liberate 244 million tonnes of CO2. Dave’s solar lighting sets offer huge scope to reduce those emissions and save poor people money at the same time. Francesco Raeli reports.