Problem: Indoor cooking fires create toxic fumes.

Solution: A superefficient clean-burning stove.

Three years ago Philips research chemist Paul van der Sluis, 44, set out to build a smokeless outdoor cooker. He wanted something for his backyard in the Netherlands that wouldn't annoy his neighbors. He wound up creating a lifesaver. Smoke and toxic fumes from indoor cooking fires are a serious health problem in the developing world. Van der Sluis's design reduces those emissions by using an electric fan, powered by the fire itself, to force air through the stove. "First, the wood evaporates into gas," van der Sluis says, "and then the gas burns. The smoke completely burns off." Philips plans to start selling the stoves this summer in India. Prices haven't been set. --Eva Barkeman

How it works:
1. Air enters through holes at the bottom.
2. An electric fan blows air upward.
3. A thermoelectric generator turns heat into electricity to power the fan and recharge its starter battery.
4. By improving the ratio of air to fuel, the fan makes the fire burn hotter and more efficiently. That reduces fuel consumption and means less smoke and faster cooking.