Rowing for 30 minutes can produce about 150 watts of electricity, enough to power this blender. Here, environmental science student Devon Snyder '10 makes smoothies while visitor Eli Howard lends a hand — and deltoids — on the rower.

Imagine, for a moment, that a space alien lands at the UVM Fitness Center. It's a busy day and the treadmills, elliptical trainers, and exercise bikes are all in use. Looking around, the alien shakes her head and asks: who has enslaved these workers and what are they making in this factory?

You earnestly explain about cardiovascular fitness, athletic training, endorphins and the Vermont winter. OK, she says, but asks again about what they're making. "I mean, isn't all that energy being used," she says, peering at the whirring innards of a rowing machine, "for something?"

People power

Brian Reed asked himself the same question. "I was in the gym one day and saw that all the machines had a flywheel," he says. "I thought: why not run it in reverse, like a Prius, and harvest all that power for the lights?"

That thought sparked Reed, a professor of physical therapy and associate dean in the College of Nursing and Health Sciences, to launch Pedal Power. The goal of this new interdisciplinary project, he says, is "to wire together all the aerobic exercise machines in the fitness center to generate and capture electrical power."

When the completed project comes on-line — "probably about a year from now," Reed says — it will be one of the first exercise-powered fitness centers in the United States, part of what may be emerging as a broader movement toward "green gyms."

"When you add up all our machines — there are about fifty — we expect to get in the neighborhood of 8 to 10 kilowatts," he says, enough power to run several classrooms, banks of lights — and the televisions over the treadmills.

But first, Reed, working with students, staff, and faculty from three UVM colleges and the athletics department over the last year — and with $5,000 in start-up funds from the provost's office — had a goal of simply showing that the idea could work.

"We needed proof of concept," Reed says.

A green concept

On a triumphant Thursday evening, in the atrium of the Davis Center, proof of concept comes in the form of a fruit smoothie.

"This one is strawberry with vanilla ice cream," says Devon Snyder '10 handing out small paper cups to bemused students passing by.

She pours the smoothie from a blender that is plugged into a power-strip attached to two car-style batteries in a box on the floor. The batteries, in turn, are wired to two rowing machines sitting nearby, donated to the Pedal Power project by the Vermont-based rowing company, Concept2. And, pulling mightily on the hardwood handles of these machines are two engineering students, Dave Ojala '09 and Will Bowen '09.

They're part of a team of five students who modified the rowers as part of their senior design work in the College of Engineering and Mathematical Sciences, working with Reed and professors Mike Rosen and Paul Hines.

Inside one rower, the fan blades of the flywheel have been removed. In their place, the engineering students have wired in a generator typically used in a small wind turbine.

"The heart of our system is the way we control the generator," says team member Owen Edgerton '09, pointing to an adjustable knob on the main beam of the rowing machine. "With this, as a user, I can control how much energy comes out," he says. And, of course, the more energy that comes out, the more that must go in. "If you want more power, you have to row harder," he says, grinning.

By using pulse width modulation — "basically, switching the generator on and off really quickly," says Ojala — the students have created a system that is adjustable without wasting a lot of power as happens when an electric source is managed by resistors. The efficiency of the students' rower system is around 70 percent, and "that's really good," says Bowen.

While the energy-harvesting rowers are now linked to batteries, once all the machines at the fitness center are wired together, they will likely be linked directly into the electrical grid, which will further increase their efficiency. That's what's happening at Oregon State University. In what may be the first U.S. university to develop such a system, OSU has 22 elliptical trainers that pump power directly back into the Oregon electrical grid. Their system was launched this winter and is projected to produce about 3,500 kilowatts annually.

Pulling for less carbon

"The basic point is to use human power instead of polluting power to reduce our carbon footprint," Devon Snyder says, as she dumps more strawberries in for the next round of smoothies. She has been working to promote the Pedal Power project with professor Robert Manning in the Rubenstein School of Environment and Natural Resources — including helping with this demonstration. "It's ridiculous that you are wasting energy to workout," she says, and she sees the project as a new way to educate about natural resource conservation.

"Any student in any major has been to the gym," she says. "Because it involves exercise, it's more appealing than recycling or turning off light bulbs."

Watts up

So, just how much power does an exercising student produce? About 150 watts can be sustained for about 30 minutes, Reed estimates. "Some of these guys might do 175 or 200," he says, and, in momentary bursts, the screen on the rower reads nearly 1,000 watts.

Working with his colleagues and with three health sciences students, Reed has been researching how this electrical power output relates to human metabolic costs and oxygen uptake for the exerciser. They have also spent days in the UVM Fitness Center — with support from athletics director Bob Corran and his staff — studying usage patterns, and getting exact measurements of when each machine is used.

"This has allowed us to make good estimates of how much energy we can harvest out of these things over time," Reed says, as he watches two new rowers take up the handles.

"People have been, like — that is such a good idea," Snyder says, holding out more smoothies, "Why isn't that already happening?"