From Nature:
Do you spend your free time sweating away in the gym? Ever wonder whether all that energy might be put to better use? Well fear not, because you might soon find yourself converting those calories to light, and helping the club out with its electricity bill. The California Fitness club in Hong Kong is among the first to jump on the green energy treadmill — stairmaster and cross-training machines at the gym have been wired up to the building’s lighting system. If other gyms follow suit, it could kick off a new motivational craze, in which sweat equals glow.
The idea of gaining light from pedal power is not exactly new — kids have been riding bikes with dynamo-powered lights for years, and you can buy watches that never stop working as long as you remember to move your arm. But the Hong Kong scheme is one of a new wave of ‘energy recapture’ ideas aimed at harnessing the surplus power of casual activities, to generate electrical power that would otherwise come from the national grid.
Other recapture ideas include using the energy of footfalls to light up pedestrian tunnels, and military backpacks that use the wearer’s movements to refrigerate the medical supplies inside. And a Dutch nightclub has even installed a dance floor that lights up when tiny ‘piezoelectric’ crystals inside it are deformed by the dancers’ feet.
More here.