# Capturing energy from stationary exercise bike

**URL:** <https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843>\
**Category:** Factual Questions\
**Created:** [September 9, 2005, 4:54pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843 "2005-09-09T16:54:12Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\
**Post date:** [September 9, 2005, 4:54pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/1 "2005-09-09T16:54:12Z")

</div>

I’ve searched through the archives because I thought there were threads on this, but no dice.

What would be required to adapt a piece of aerobic-exercise equipment such that the energy could be captured and used as house current? Would this result in any economically significant energy capture if you could force a 4-person household to crank for an hour per person each day?

---

<div class="post-metadata">

**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [September 9, 2005, 5:05pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/2 "2005-09-09T17:05:31Z")

</div>

[This recent thread](http://boards.straightdope.com/sdmb/showthread.php?t=333350) discusses power output.

I don’t know if there’s an off-the-shelf solution for this. I’d guess you can connect a bike to an automotive alternator and use it to keep a UPS (Uninterrupted Power Source) battery topped up. A UPS already contains a battery and DC-\>AC inverter.

---

<div class="post-metadata">

**Author:** ![Schuyler](https://avatars.discourse-cdn.com/v4/letter/s/54ee81/32.png) [@Schuyler](https://boards.straightdope.com/u/Schuyler)\
**Post date:** [September 9, 2005, 5:31pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/3 "2005-09-09T17:31:13Z")

</div>

> [@Brain Wreck](#):
>
> Would this result in any economically significant energy capture if you could force a 4-person household to crank for an hour per person each day?

No. As a species, our might lies in our minds, not our muscles. You know those little bike lights powered by a generator that rubs against the tire? They are pretty feeble - the point being, we’re only good for \<100W, and there just doesn’t seem like a lot you can do with that. Even say you could run a battery charger for an hour, you are only putting out \<0.1 kWhr. At current electricity rates, this is pennies. ☹

To reduce dependence on the grid, I would think that reducing energy consumption and/or solar collection are more viable. Also, this is the reason that biking is so economical - not because humans are so efficient, but because you don’t have to lug around 3000 lbs of metal everywhere you go.

---

<div class="post-metadata">

**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [September 9, 2005, 5:42pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/4 "2005-09-09T17:42:51Z")

</div>

[These guys](http://town.hall.org/environment/earth_day/15_eday.htm) did it but there are no specs on wattage output. [Here’s another](http://www.ph.unimelb.edu.au/~muppets/lasershow_details/teacher_info.htm) where among other things they suggest it would take up to 70 people pedaling to run an air conditioner.

---

<div class="post-metadata">

**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\
**Post date:** [September 9, 2005, 5:45pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/5 "2005-09-09T17:45:58Z")

</div>

> [@CookingWithGas](#):
>
> Here’s another where among other things they suggest it would take up to 70 people pedaling to run an air conditioner.

When asked why they needed an air conditioner, they replied “Do you know how hot we get pedalling that hard?”

---

<div class="post-metadata">

**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\
**Post date:** [September 9, 2005, 5:54pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/6 "2005-09-09T17:54:36Z")

</div>

I just figured it was better to capture the energy than let it go. Every time I put in an hour on one of these bikes, I can’t help thinking how much energy I’m wasting. I can do something like 120 watts, probably more when I’m in shape. I hear that top cyclists can do something like 900 watts in peak bursts.

---

<div class="post-metadata">

**Author:** ![threemae](https://avatars.discourse-cdn.com/v4/letter/t/5f9b8f/32.png) [@threemae](https://boards.straightdope.com/u/threemae)\
**Post date:** [September 9, 2005, 6:15pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/7 "2005-09-09T18:15:43Z")

</div>

> [@Brain Wreck](#):
>
> I just figured it was better to capture the energy than let it go. Every time I put in an hour on one of these bikes, I can’t help thinking how much energy I’m wasting. I can do something like 120 watts, probably more when I’m in shape. I hear that top cyclists can do something like 900 watts in peak bursts.

Lesse,

Armstrong, Basso, Ulriich, other major Tour riders can likely do around 500+ watts over thirty minutes at sea-level, around 260-280 watts over five to six hours, and sprinters like Petacchi can put out a stunning 1,500-2,000 watts in all out sprints for around ten to fifteen seconds. All of these are done at peak fitness with considerale efforts. Quite a few people, with training, would be able to do 200 consistently and comfortably for three or more hours.

---

<div class="post-metadata">

**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\
**Post date:** [September 9, 2005, 6:57pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/8 "2005-09-09T18:57:52Z")

</div>

So you could capture that energy, but as noted it’s about enough to run a light bulb. If you took all the effort to build a bicycle generator and instead put it towards going out and buying three compact flourescent light bulbs, you’d be better of, electrically speaking.

Of course, if you don’t have electricity, and need to power something, bicycles can make sense. That’s what these guys do : [http://www.pedalpower.org/maya.html](http://www.pedalpower.org/maya.html)

---

<div class="post-metadata">

**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\
**Post date:** [September 9, 2005, 7:02pm UTC](https://boards.straightdope.com/t/capturing-energy-from-stationary-exercise-bike/320843/9 "2005-09-09T19:02:22Z")

</div>

Oops, this is a better link for cool bicycle machines: [http://www.mayapedal.com](http://www.mayapedal.com)