Watts of Sweat

Eco-conscious gyms allow members to spin calories into electricity.

February 24, 2009
Gym members work out on the Human Dynamo.  When these machines are hooked up to a <br> special generator, people produce usable energy as they exercise [Credit: Caroline Woodham].
Gym members work out on the Human Dynamo. When these machines are hooked up to a
special generator, people produce usable energy as they exercise [Credit: Caroline Woodham].

Legs spinning. Muscles straining. Heart pumping. The human body is an energy-making machine. Yet a workout on a stationary bike or elliptical trainer usually only results in puddles of sweat and radiating body heat — and maybe that pleasant “done the body good” feeling. What if all that biomechanical work could be harnessed to do the Earth good, too?

This is just what inspired Mike Taggett to create the Human Dynamo, an exercise bike that turns calories into useable watts. “There’s a certain satisfaction when you work out and feel like you’ve actually accomplished something, instead of just spinning your wheels,” says Taggett, president and founder of Henry Works Research and Development in El Paso, Texas.

Harnessing human energy has recently left the realm of backyard hobbyists to become a viable commercial technology. Spurred at first by volatile oil prices, business owners are quickly discovering that the rising ranks of environmentally conscious gym-goers appreciate the ability to generate watts while working out. This past September, the Green Microgym in Portland, Oregon welcomed Taggett’s first installment of the Human Dynamo. The gym is now helping set the pace for a small but growing pack of patron-powered fitness clubs.

The idea for the Human Dynamo came to Taggett in the late 1980’s when he realized an “obvious waste of power” in the exercise bike. He began engineering a solution, at first in the primitive form of what he calls a “Gilligan’s Island human-powered blender.” By spinning the pedals of an exercise bike retrofitted with a car generator, he prepared margaritas without the need for an electrical outlet.

While a bit more serious in its intentions, the concept remains nearly unchanged twenty years later. Taggett started with a question: “How can I most efficiently generate the most power given my frame, my muscles and my capabilities?” The answer lay in a simple machine that combined rotary motions of both the arms and legs.

“It’s essentially a very small wind turbine, where the human being is the wind,” says Green Microgym owner, Adam Boesel.

The Human Dynamo’s unique design maximizes calories burned and watts created. A person in decent shape, Taggett estimates, can burn about 400 calories an hour and consistently generate about 100 watts of electricity. (Lance Armstrong’s numbers would be closer to 1400 calories and 350 watts, he says.) The legs produce approximately 70 percent of this energy, with the other 30 percent coming from the arms.

The machine itself looks and rides like an ordinary stationary bike. But a second power source – a hand crank that is spun while pedaling – replaces the handlebars. An odd black box and additional wires are the only things suggesting that energy is being harvested. The spinning of all four limbs turns the bike’s 18-inch flywheel, which is connected to a generator. An average person spins the pedals about 60 times per minute, or at 60 rpm, according to Taggett.  This translates to 300 rpm in the flywheel.  A belt then connects the flywheel to the generator, taking the speed up to 1500 rpm.

Human power flows directly into the electricity grid with Taggett’s new “FireWheel Inter Grid” (FIG) system. When a person first gets on a Human Dynamo, the FIG acts like a motor, taking a small amount of electricity from the grid to power up the bike. Once the pedals begin spinning, the FIG turns back into a generator and starts absorbing kinetic energy. Industrial electric controls then convert DC power from the generator into AC power, and this is pushed through a wall socket into the grid. “You literally just plug it in like a normal appliance,” says Taggett.

This new technology was installed at Portland’s Green Microgym in January, replacing an old battery-based system that utilized less than 50 percent of the current coming out of the Human Dynamo. The updated system delivers approximately 70 percent of the total watts produced into the building’s grid — enough electricity to power the lights and stereo in the gym’s largest room.

Green Microgym’s Adam Boesel finds his customers appreciate this merging of personal and environmental health. They know that the more they work out, and the more they get in shape, the more clean energy they can create. As an added bonus, for every hour of electricity produced by a member, the gym donates five dollars towards a membership for someone that can’t afford one. Not only does this healthy motivation lower Boesel’s electric bills, but the green gym concept has a strong marketing pull. He could have followed the “culture of gyms focused on vanity and luxury,” with energy-sucking flat-screen televisions and elaborate lighting systems, but instead opted for eco-sustainability. “I can provide just as great an experience for far less of a cost of operations for me than if I was trying to be the newest, fanciest gym,” says Boesel.

In addition to his Human Dynamo – two bikes connected to one generator – Boesel’s gym boasts energy-efficient treadmills, spin bikes retrofitted with batteries and his latest toy, a prototype of a calorie-recycling elliptical machine. High-tech solar-paneled awnings adorn the outside of the gym.

But technologies for harnessing human energy are not new, nor are they reserved for Portland — arguably America’s greenest city. In 2007, before these machines began appearing in U.S. gyms, a Hong Kong athletic club started collecting energy from step, elliptical and cycling machines. Within a few months of Human Dynamo’s inaugural spin at the Green Microgym, a gym in Connecticut attached Green Revolution’s stand-alone technology to its existing cycling equipment. And Florida’s ReRev.com continues selling similar retrofits they debuted last summer, mostly for elliptical trainers.

Mitchell Joachim, an award-winning architect and professor at Columbia University, is developing his own idea of an eco-friendly gym. The “River Gym,” he suggests, may some day exploit human movement on exercise bikes, treadmills and elliptical machines to shuttle small boats between New York City boroughs during morning and evening commutes. His design could solve two problems many New Yorkers face: long, aggravating commutes and a shortage of time for exercise.

No one seems to question that there is human power available for the harnessing. “Any physical act you perform produces some kind of energy,” says Joachim. Its contribution as an alternative energy source will probably never compare to that of solar or wind power, but every watt helps.

“People should be trying to capture power generation opportunities wherever they can,” says Steve Hammer, director of the Urban Energy Program at Columbia University. “You just have to think about how much it’s going to cost.”

Substantial upfront costs remain the primary concern for alternative energy investors, including gym owners. If the price of the bikes themselves is ignored – gyms need to purchase these anyway – a Human Dynamo runs at about four dollars per watt of electrical capacity. Depending on how many hours per day the machines are in use and how many individual units are attached to one generator, payback on the initial investment could take more than ten years. However, it’s a bargain compared to solar power, which costs ten dollars per watt. “Human power is a pretty economical alternative energy source,” says Taggett.

The benefits go beyond the electric bill, from diversifying the world’s alternative energy arsenal to awakening people’s consciousness about the energy they consume – or can create – in their daily lives. With human energy, says Adam Boesel, “you can help yourself, help the environment, and help the community.” Eventually, by adding additional technologies and drawing more environmentally conscious patrons, Boesel hopes his gym will be powered 100 percent by human movement.

“More power to them if they can,” says Hammer.

Related on ScienceLine:

Harnessing wind power.

Poo Power.

Turning tidal currents into electricity.

About the Author

Lynne Peeples

Lynne Peeples is a freelance journalist focusing on health and the environment. She graduated from NYU’s Science, Health and Environmental Reporting Program, where she was the editor-in-chief of Scienceline. She has also written for Scientific American online, Audubon Magazine, The Harvard Gazette and Amstat News. Before NYU, Lynne worked at Harvard University crunching numbers for HIV clinical trials and environmental health studies, while teaching an introductory biostatistics course. She also holds an M.S. in Biostatistics from Harvard and a B.A. in Mathematics from St. Olaf College. Her resume and clips can be found at: http://www.lynnepeeples.com


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