Last night, channel 12 ran a news story about a new Portland gym that has outfitted its exercise machines with generators. This is the first gym of its kind in the United States, although a few such gyms have been operating in Hong Kong. I found it a bit surprising that nobody in this country had built a gym like this because the idea is pretty low-tech.

According to the story, a variety of devices, such as weedwhacker motors and truck alternators were being used to generate electricity. One of the setups shown was a stationary bike with a big flywheel that was being used to drive what appeared to be a large permanent magnet motor. This was connected to a storage battery. The story said that the gym covers about 20% of its total energy usage with electricity generated by people working out on the modified machines. They hope to get closer to 100% as they convert more machines and get more people to go there.

Some time ago, I was thinking about modifying a belt-resistance exercise bike to generate electricity, as the people running this gym did. Unfortunately, I never got too far along on this project.

ADD: The device that was being charged by the exercise bike in the KPTV story looked like a Duracell Power Pack ( http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200355924_200355924 ). This has a rechargeable battery and a built-in DC to AC inverter, which would allow the gym to easily run lights, fans, TVs, etc.

Nice!! I've had that idea for years. All those people on the equipment could easily power some lighting,etc.
A human can make approx 100Watts of continuous power,for a shorter time period.(15-30mins? About the average workout length?)
50W continuous per-person might be more reasonable. (short bursts can be up to 300W,for an athlete,etc.)
Assuming 10 people on the equipment on average,at any given time, 10x50W=500W of continuous power. You could easily run some efficient lighting with that.Or a couple TV's..or the music system..or?
Add a big battery bank as a buffer/storage,and I bet you could run the lighting 24/7.
I'm glad someone finally got around to doing it.

An article on the gym's web page made some pretty good points (that I hadn't considered) about how typical gyms use a lot of energy. Cooling a busy gym in the summer uses a lot of electricity. Heating water for showers is another big energy hog. The "green" gym is aimed at people who live close by and can take their after-workout shower at home (the gym has no showers of its own).

Another web page about electric-generating stationary bikes posed an interesting usage scenario: use the stationary bike to charge the batteries on an electic scooter. The author had a generator bike and was using it to power his laptop, lights, small TVs, etc. He said that the electric scooter (if he were to buy one) might be useful to him for the work commute, as pedaling a bicycle while wearing a suit is not feasible.