“Scientists have known for nearly 200 years that certain materials can convert heat to electricity…” reports Science, describing research into an intriguing new approach: Refrigerators, boilers, and even lightbulbs continually dump heat into their surroundings. This “waste heat” could — in theory — be turned into electricity, as it is sometimes done with power plants, automobile engines, and other high-heat sources. The problem: These “low-grade” sources give off too little heat for current technology to do the conversion well. Now, researchers have created a device that uses liquids to efficiently convert low-grade heat to electricity. The advance might one day power energy-scavenging devices that can light up sensors and lights and even charge batteries… Thermocells are good at converting small temperature differences into electricity, but they typically produce only tiny currents… This thermocell generated five times more power for the same electrode area than previous versions, materials physicist Jun Zhou and his colleagues at the Huazhong University of Science and Technology report this week in Science. It also more than doubled the efficiency needed to make a viable commercial device. A paperback book-size module of 20 thermocells could run LED lights, power a fan, and charge a mobile phone, the team found. Read more of this story at Slashdot.