Heroes of the Environment 2008

When he was a young professor of nuclear physics at the University of Oldenburg in the 1970s, Joachim Luther's office was often besieged by students waving antinuclear banners and shouting slogans. "I'm a scientist," says Luther, "so I figured it was important to test their arguments and started reading everything I could about solar power."

Soon convinced that the future lay not in nukes but in regenerative energy sources like solar and wind, Luther set out to prove that they could run not just someone's country cottage, but entire countries. His university colleagues scorned him. "They said it wasn't real physics," says Luther, grinning.

In 1993, Luther became head of the world-renowned Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany. The ISE works hand-in-hand with corporations on research and real-world applications for new technology. During Luther's tenure, the institute created super-thin silicon-wafer solar cells, and also proved that solar cells can be made of multicrystal material, which is less expensive than silicon. Luther's team developed air-conditioning systems that run on solar power. And they created a solar-power module that, instead of using a flat panel, combines mirrors and lenses to focus the sun's rays, thus increasing the amount of energy that can be produced in a small space. The module sits on wheels; a motor allows it to track the sun. Such innovation is vital if we're to have any chance of slowing the effects of climate change. By the middle of this century, we will need half of our energy to come from regenerative sources, says Luther. "The question is whether we can limit the rise in 
 the earth's temperature to two degrees."

Luther retired from ISE in 2006, and recently became the head of the Solar Energy Research Institute of Singapore (SERIS), which aims to put the city-state on the alternative-energy map. As well as running collaborative research between ISE and SERIS, Luther is working on superefficient solar air-conditioning technology. "In Europe, the problem is the cold," he says. "In Asia, it's the heat." Whatever the temperature, Luther aims to use science to make us more comfortable — without fueling global warming.