So this is a bit of a gimmick—but it’s a GOOD gimmick: a new gym in Portland, OR is using stationary bicycles to produce electricity. (See here and here for recent press.)
First off, to any naysaying skeptics out there: there’s absolutely nothing wrong with recapturing a bit of power that would otherwise be wasted. So I don’t want to hear any talk-radio crank poo-pooing the idea. (Not that they’d ever listen to me—I just wanted to get this out of the way early.)
Second, and perhaps more importantly, this is a perfect example of the sort of creativity the market’s capable of. Once we set responsible limits on climate-warming emissions, we’ll find all sorts of ways, large and small, to eliminate energy waste, and do more work with less fossil fuels. Stationary bike-generators are just small examples of all the nifty stuff we can do when we let ourselves imagine new solutions to energy woes.
That said, since I’m an incurable geek, I just had to run the numbers. How much power can a person actually generate from one of those stationary bikes?
Answer: not much, unfortunately.
According to Calorielab.com, exercising on a stationary bike requires a rider to produce somewhere between 50 and 250 watts of power. A wattage of 50 is considered “very light effort”—just enough to get your heart rate above resting, I suppose. A wattage of 250 is considered “very vigorous effort.”
That sounds about right to me. Tour de France rider Floyd Landis (later caught doping) sustained an average of 232 watts over the course of the tour. Of course, that’s over a long race with lots of downhills; peak output during short bursts can be much higher. Super-biker Lance Armstrong could pump out about 500 watts for 20 minute bursts.
But Armstrong, obviously, is pretty abnormal. For the average gym rat looking for a cardio workout, I think that 150-200 watts would probably be in the ballpark. And let’s further assume that the generators are about 90 percent efficient—meaning that 90 percent of the mechanical energy from the bike actually gets turned into usable electricity.
Doing the math, a 45 minute ride at moderate-to-vigorous effort produces about 120 watt-hours of power. How much is that? Enough to:
- Run a 100-watt bulb for a little over an hour.
- Run 4 compact fluorescent bulbs for the same duration.
- Run an aquarium pump for a day.
- Power a small frost free fridge for about a half hour (give or take.)
You get the drift. Gym-rat power probably won’t do much more than keep the machines running and help keep the lights in the gym on. It certainly won’t heat the water for an after-workout shower.
The cost savings are pretty slim, too. Portland General Electric’s peak power rates are about 11 cents per thousand watt-hours. So 45 minutes of biking produces only about a penny’s worth of electricity. And that’s where the “gimmick” part comes in: I have to wonder if the cost and energy used to outfit bikes with generators really balances out the relatively small amount of electricity that’s generated. Maybe it does. But the question definitely runs through my mind.
And here’s another wrinkle. Imagine if, instead of riding a stationary bike attached to a generator, the gym rat had ridden a real bike in place of a car trip. That’s a much, much bigger energy saver, since cars are surprisingly bad at converting fuel into forward motion. A ten-mile bike trip reduces gas consumption by half a gallon—the equivalent of about 18,300 watt-hours, compared with the 120 watt-hour output of a stationary bike generator. Measured per unit of energy, biking instead of driving is, oh, about 150 times more eco-friendly than using a stationary bike generator. If what you really care about is saving energy, look to replace some car trips with bike trips, if you can.
Still, if you’re looking for an eco-friendly place to get a nice indoor workout in Portland, I’d check this gym out. It sounds like a cool idea, and a nice place to get a workout.
Bike photo courtesy of Flickr user Bibliona under a Creative Commons license.
morgan
Even though it strikes me as green-washing, this source of micro-energy should be as financially and ecologically viable as, say, micro hydro or a tiny wind turbine. Each provides a free source of raw energy for which we must ‘only’ design and build a small method of conversion. If it pencils out for a tiny hydro source that runs 24 hrs a day, it ought to do so for a bicycle that runs 12 hours a day. Now take that output and multiply by 500k or a couple million to imagine the national savings. Still not much, but something. otoh, some will argue this would provide a false sense of progress or is an example of picking the way-high fruit first, as you note. Reminds me of how, even in the enviro movement, we have difficulty making many of the highly impactful choices, like biking to work, because they require deeper change, and with the way many systems are poorly constructed, they require a degree of sacrifice.
Jesse
Actually, many stationary bike machines already have generators built in. These are often electronic so you can have easily variable intensities built in. This energy often goes to a big heat sink on the side of the machine. (You know, that big hunk of metal.) However, remove that, hook up the leads to a couple of capacitors and inverter and you’re set!
David Treadwell
Great analysis, and the structure of the argument sounds remarkably familiar: http://davidtreadwell.spaces.live.com/blog/cns!556BCC6296CD41D7!357.entry
Ben Brown
These should be marketed as a package with video games to concerned parents with fat kids. Peddle for 1/2 hour to play for an hour would be excellent. Of course, big-pharma’s obesity division would block it because it would cut into their profits.
kenzo
I’m proud to say that in a City Jail here in the Philippines they are implementing this. The article can be found here http://newsinfo.inquirer.net/inquirerheadlines/metro/view/20100619-276504/Jail-guards-invention-saves-on-power it talks about prisoners taking turns in using stationary bikes to generate power.As you can see on the photo on the article they are using an ordinary bike. I think it would be better if they used a real stationary bike, recumbent to be exact (go here http://www.dogengine.com/used-stationary-bikes.php to see the different types of stationary bikes) because it is more relaxed than the others thus maximizing our potential output. Nice huh?