(Business 2.0) -- Ever watch people exercising and wonder if all that energy could be put to better use? A couple of students at the University of Stirling in Scotland did, and the result is a prototype for a system that uses stationary bikes and rowing machines to power the lights at a gym. That won Emmanuel Pogoson and Tao Pei a $4,600 entrepreneurship award from the university in May. Now they're planning a patent filing, hunting for technical partners, and figuring out how to add treadmills to the mix.

A typical gym runs up an energy bill of $75,000 a month, and Pogoson thinks the system could slash that by 20 percent. "It will be linked to every machine in the gym and be centrally controlled," Pei says. One person exercising vigorously on a bike can produce about 200 watts--enough to power eight 4-foot-long fluorescent tubes. Exercise machines that power their own LED displays, on the market for a decade, are already in widespread use. And, of course, gyms are interested in any device that will save them even more money. "Conservation is a big priority for us," says Gold's Gym spokesman Dave Reiseman. "If it's easily adaptable and practical for gyms, it is something we would certainly consider." The days of discounted membership fees for exercisers who make the most energy may not be far off.