Pedal powered generator?

paulr

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I'm spending too much time on the computer and I need some exercise. But I'm too lazy to exercise, and too addicted to step away from the computer.

It occurs to me that maybe I can take care of both problems at once: power the computer from a bicycle-type generator, so that in order to use the computer, I have to pedal the generator for a while. The computer is a full sized laptop (700 mhz PIII) using maybe 40 watts on average. At moderate pedalling intensity (equivalent to a mild uphill grade) I can put out maybe 80 watts. So I'd have to pedal for 1/2 an hour to use the computer for an hour, which sounds like a good trade-off for me. At 20% efficiency that burns 340 Calories/hour. I'd use the generator to charge an SLA battery and use the SLA battery to run the computer through an inverter.

Any idea where to get the pedal powered generator? Can I buy stuff like that ready-made without spending a bundle? I know there are dynamo bike headlamps but those are in the under-5-watt range, I think. I could imagine trying to cobble something up out of an exercise bike and a car alternator, but it sounds clumsy.
 

MR Bulk

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Fabulous idea! How about one where you have to pedal WHILE the computer is running? Then you'd get max exercise if you're like the bulk of us, addicted to the computer for Several Hours a day. Set it up so that Very Moderate pedaling (no uphill, just flat land) would provide just the power needed to keep the transformer running the computer. In aerobicise the important thing is to keep the heart rate just Slightly elevated for a Longer period, rather than "going for it" uphill for only half an hour. Make it so that there is only enough reserve for powering down the computer after you get off the bike.

I think this would be popular if produced in a commercially available format. Far too many sit on the 'puter instead of exercise. Package it as just the transformer and hook-up hardware between the exercise bike and the computer (ie., rubber roller contacting the rear wheel, or whatever spins round on your exer-bike). Could be used for TVs as well.

You go, Paul!
 

paulr

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Pedaling to power a TV while watching it sounds fine, but for a computer I think I need batteries. I need to be able to type, and I need to be able to concentrate while typing. Pedalling at the same time won't go too well with either of those.
 

Steve K

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This is a fun idea, and even sorta practical!
And of course, it's crossed the minds of many people before. I only know of one person who actually converted the concept to actual hardware. His name was Bob, he lived in the Pacific Northwest, and I think he even worked for an electrical utility company.

His design was to use a bike on a typical indoor trainer (this holds the bike up, and provides some sort of drag on the tire). The design used the bike's rear wheel to drive a car alternator, which charged a battery (lead-acid), which drove an inverter, which powered his computer. He could then surf the web while exercising.

As PaulR suggested, the battery is needed to provide steady power to the computer, and it wouldn't be a bad idea for the TV either. The trick in this whole scheme is that the person has to adjust the field current in the alternator to control the load on the bike. Increased load is a result of generating more power to charge the battery, and reducing the charging current will reduce the load on the bike (and your legs). The battery acts as a buffer, to keep you from feeling every change in power required by the TV or computer.

To me, the trickiest part has always been how the alternator would be driven by the bicycle. A chain drive would be the best possible solution. A rubber roller riding on the tire would be the worst. Some calculations would be required to be sure the alternator was being spun at the correct speed. An alternator is easy and cheap to buy. Not sure how hard it is to dig in and control the field current yourself. And you'd probably want someone to weld a bike sprocket (or maybe a freewheel or cassette??) to the pulley, to permit a chain drive.

Sounds like a great project! Let us know how it works out!


Steve K.
 

Sub_Umbra

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paulr,

Great idea. IIRC selection of individual components is critical. In the late 70's I read a great trade paperback, Pedal Power. I searched around, and while there are many books by that name, I think this is the one:

Pedal Power by Rodale Press, 1977, by James C. McCullagh.

The above book was published at the right time to be the one I read. The best bet would be to find one in a library to make sure before you order.

It provides numerous applications for pedal power from running a grain mill to a portable washing machine and generating electricity. If you decide to 'roll your own' pedal electricity generator his discussion on component selection would be invaluable. You may even want to read it before you buy a 'store bought' generator.

If you determine that it's the right book it can be had for a reasonable price at ABEBOOKS on This Page.


sloegin,

The one in the link you provided looks pretty slick.
 

raggie33

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at the dam here they have a pedal powered stationary bike that turns a genrater and it lights up a bulb id guess was 100 watt ya would be suprised how hard it was.
 

idleprocess

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[ QUOTE ]
17330 Human Power System $599.00

[/ QUOTE ]
SIX HUNDRED DOLLARS?!

For that much, it had better include more than you see in the picture - including a few 20Ah batteries and an inverter.
 

UncleFester

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When you get this thing working, I think you'll be surprised at how much effort it takes to make a usable amount of electricity. Just intuition speaking here. Someone mentioned the alternator on the bicycle is only a few watts. It's VERY different with the alternator running and not. Like about two gear's worth of different.
 

idleprocess

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I seem to recall a demo at a power company "museum" of sorts that let you operate a treadmill to power a small TV & video camera. It took a decent amount of effort.

The average human can generate about 0.10 HP working steadily all day. I'm not sure how many watts that would equate to.
 

Darell

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I've always wondered about putting all that wasted power at gyms to work for us. There's all these muscle-bound guys (If I were in shape, they'd just be "guys") lifting iron weights against gravity. For HOURS. Often hundreds of pounds at a time. All that energy just wasted! Then they take the escalator to street level, hop in the SUV and drive the 1/2 mile home. I don't think gyms should have automobile parking lots.

Oh wait... I'm getting off track here. Yes, it would be great to have a device like this.. but it *certainly* needs batteries and an inverter!
 

markdi

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about 746 watts per hp
so if you are saying that I can only generate 74.6 watts in
a day I think you are wrong
 

paulr

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I can generate 100 watts for a few minutes. It's pretty strenuous, but if I were in better shape I could keep it up for longer.

A world-class athlete can generate 300 watts for hours. There's a huge difference between a world-class athlete and an ordinary person.

One hp is 550 ft-lb/sec, so it's like lifting a 550 pound weight one foot and putting it back down, once a second. I guess I could do a few reps of that with 110 pounds. I couldn't keep it up. 550 pounds, I wouldn't be able to lift.
 

UncleFester

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Darrel
I've been saying the very same thing for years. somebody is missing the boat there. That energy could be stuffed back into the grid......
 

Brock

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Markdi, I think were talking about 75w each hour. I know I have run a bike one for an hour and generated about 125w, but I was much younger and did bike regularly at the time.
 

turbodog

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[ QUOTE ]
paulr said:
I can generate 100 watts for a few minutes. It's pretty strenuous, but if I were in better shape I could keep it up for longer.

A world-class athlete can generate 300 watts for hours. There's a huge difference between a world-class athlete and an ordinary person.

One hp is 550 ft-lb/sec, so it's like lifting a 550 pound weight one foot and putting it back down, once a second. I guess I could do a few reps of that with 110 pounds. I couldn't keep it up. 550 pounds, I wouldn't be able to lift.

[/ QUOTE ]

You're thinking of lifting a load with your arms. Change that to your legs and we now have a different solution.

I person in decent shape can output about 175 watts or so on a bike for an hour or more.

I consider myself a "sport" class racer and have measured output of 325 watts or so for 8+ hours at a stretch.

Lance would likely hit 50% above that level.
 

Darell

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[ QUOTE ]
markdi said:
about 746 watts per hp
so if you are saying that I can only generate 74.6 watts in
a day I think you are wrong

[/ QUOTE ]
markdi -

A Watt is is an instantanious measure of power. A unit rate. There is no such thing as "generationg 74.6 Watts in a day." It is a bit like saying that San Francisco is 87mph from here. Now, if you were to generate 74.6 Watts all day long, that would be almost 1.8kWh - and that would truly be awesome. I can drive my car 7.2 miles - at freeways speeds - on that much energy. With the whole family doing that, we could commute in the car on just human power alone. Fred Flinstone lives!

**ooops. I see that I was a bit late... Brock got it. /ubbthreads/images/graemlins/smile.gif

Man, I need ol' Turbodog over here pedaling for me when the sun isn't out!
 

markdi

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watt hour-minute-second-pico second
so a watt is not a measure of instanious power every time.
got to go a vey beautiful woman is waiting for me
so no spell check
 

3rd_shift

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I would suggest a laptop for this idea to work.

#1 It uses less power than a desktop, which would be better suited for the majority of us couch potatos. /ubbthreads/images/graemlins/wink.gif
Pedaling would be just easy enough to allow typing and mousing around while exercising.

#2 It comes with a rechargeable battery already.

#3 It's portable for outdoor exercising too.

#4 Ideal for places where there is no other power source.
 

markdi

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so Darrell where did you hear that a watt was a measure of instantaneous power(It can be-watt second)
just curious
at 14 years old I knew what a watt hour was
 
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