Gyms Tap Into The Power Of Sweat

Working out at the gym takes a lot of energy — both for the patron and the gym itself. And now, new machines are being developed to capture it. A Seattle-based company has developed exercise equipment that takes the resistance generated by all that kinetic energy and sends it back into the electrical grid. "Green gyms" have popped up for like-minded exercisers to turn their sweat into kilowatts — although the net effect might be less than you'd think.

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The modern gym typically uses a lot of electricity, with all its Stairmasters, stationary bikes, big-screen TVs. Now, some gyms are trying to not only use less power but actually put some back into the grid.

From Portland, Oregon, Deena Prichep reports on exercise equipment that's designed to create electricity.

DEENA PRICHEP: In order to look good in a swimsuit on her upcoming trip to Hawaii, Cory Bilger has been hitting the elliptical trainer at Portland's Green Microgym pretty hard these days. And she's not just burning calories, she's making electricity.

Ms. CORY BILGER: This is the total power generated: 4.19 and counting.

(Soundbite of laughter)

PRICHEP: That's 4.19 watt hours of energy she's creating.

Ms. BILGER: I actually take a picture of every workout with my iPhone.

PRICHEP: The company that developed this machine is called Resource Fitness. Chief Technology Officer Aaron Bird says, basically, think of a windmill.

Mr. AARON BIRD (Chief Technology Officer, Resource Fitness): Wind turns the turbine, that kinetic energy is converted into electricity through a generator, it then runs through an inverter to convert it to AC electricity, which goes into the grid.

PRICHEP: In this case, instead of the wind, the power comes from your legs. Resource's bikes cost about $1,200, which is pretty standard for commercial gym equipment. And all of their machines plug right back into - excuse me, out to -the electrical grid. Bird says that makes them much more efficient than, say, using a battery.

Mr. BIRD: The problem with a battery is when you charge the battery, and then when you drain the battery to get the energy back, there's efficiency loss in both directions. There's also efficiency loss when the battery's just sitting there because it doesn't hold the energy forever.

PRICHEP: Bird says there's still some unavoidable loss in the conversion. But overall, energy-generating exercise equipment is pretty efficient. And it's cropping up across the country in gyms, colleges and condos.

One company, ReRev, is even getting ready to outfit an array of bikes at Edwards Air Force Base. But the amount of energy that all of these machines generate is less than you might think.

Green Microgym's owner, Adam Boesel, sees exercisers working out every day on his energy-generating bikes and elliptical machines.

Mr. ADAM BOESEL (Owner, Green Microgym): So, generally people generate somewhere between 30 to 60 watt hours.

PRICHEP: Boesel admits that's not a lot, but it is something.

Mr. BOESEL: Thirty watt hours can power an iPad for three hours; 60 watt hours can power a stereo for an hour.

PRICHEP: There are times when the Green Microgym actually generates more power than it draws, say when all the machines are going during a spin class. But on the whole, the gym doesn't even create enough electricity to meet its own demands. Still, Boesel says, every little bit helps.

Mr. BOESEL: Yeah, the way we look at it is that you can choose to be in a gym with machines that waste a lot of electricity, or you can choose to be in a gym that's very energy efficient, where you're creating electricity.

PRICHEP: For microgym member Cory Bilger, reducing her carbon footprint is definitely part of the draw. And if she can do it while getting ready for a Hawaiian vacation, all the better.

Ms. BILGER: I told you, I'm getting in a bathing suit. It's a big deal.

(Soundbite of laughter)

PRICHEP: According to Bilger's iPhone diary, she's already logged 258 watt hours in February, enough power to run her iPhone for about a month.

For NPR news, I'm Deena Prichep in Portland, Oregon.

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