Bicycle powered generator

Discussion in 'General Electronics Chat' started by Dawud Beale, Oct 30, 2013.

  1. Dawud Beale

    Thread Starter Member

    Feb 10, 2012
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    Hi everyone

    I am thinking of starting a bicycle powered generator project and wondered if anyone had any advice or recommendations that may help.

    I also wondered the best way to find out all of the characteristics of the generator and how to be sure whether an appliance will be safe to attach to the generator or not.

    I am interested in attaching a range of different appliances to it such as a 12V battery, a cooker, water purifier, battery charger to charge AA, AAA, C, D etc batteries.

    Any advice, links to potential products that can be used effectively, links on how to set it up, pitfalls, how to understand what appliances can be used with it, anything else that is useful will be much appreciated

    The first thing I really need help with is how to choose a suitable generator. What are my options, available price ranges etc?
     
  2. wayneh

    Expert

    Sep 9, 2010
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    One thing to consider is the concept of eating food to make electricity. Human food is a relatively high cost and quality source of energy. A human can generate mechanical power at about 25% efficiency, and a bicycle can deliver that with little loss to a generator. So maybe 20% of what you eat can be delivered to a generator. I think a generator is something like 85% efficient, half that if you store the energy into a battery.

    I personally can burn about 800 kcal/hour (physics kcal = nutrition cal) for a couple hours or so, but this is declining every year. :( That means that today I could deliver about 200 kcal/hr = 232W to the generator for a couple hours. Certainly an athlete could do far better. I believe values over 300W are not unusual for the Tour de France guys over long stretches, and well over 500W is possible for the one minute range.

    I'm not sure how you size a generator but I would assume you want it to tolerate some gorilla jumping on and spinning it like crazy, while being efficient at the normal human pace.
     
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  3. Dawud Beale

    Thread Starter Member

    Feb 10, 2012
    275
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    I think maybe a small generator to start with as a little project to learn more, before moving onto a larger project. I know very little about power generation currently. If you have any recommendations to help get me started it would be great
     
  4. absf

    Senior Member

    Dec 29, 2010
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    Well, never though of using bicycle to generate electricity to power appliances. Are you able to get efficient generators (dynamos) in UK and how are you going to couple it to your bicycle?

    On my bicycle which I used for exercise going round a jogging track, it has a small dynamo which generates 6V AC just enough to light a bulb. The dynamo is coupled to the rubber wheel surface. If I increase the load to draw more current, the dynamo would stall and makes paddling very tough.

    If your generator is coupled to the bicycle using gears, it would be more efficient and makes less effort on the person cycling. You can start by making a battery charger to charge a 6V or 12V battery as suggested by wayneh and take the power from the battery. Running a few LEDs or even a mcu or even a flourencent lamp are no big problem. But a cooker if it consumes more than 1 KW would be a bigger problem to solve unless you have 3 or 4 bicycle paddling at the same time.:D

    Allen
     
  5. elec_mech

    Senior Member

    Nov 12, 2008
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    This may provide some guidance - Hackaday just had a article on using a bike for emergency power here.
     
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  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    If I were going to make one, without doing any research, my first thought would be to obtain a treadmill motor like this (1.5HP, 100V, 14A, 4900RPM). Since the motor is a permanent magnet motor and it spins 4900RPM when 100VDC is applied to it, I would expect it to act as a generator and generate somewhere around 100VDC when I mechanically spin it to 4900RPM. Proportionally, I would expect it to generate around 12V when I spin it 588RPM. I haven't timed myself, but I estimate that a comfortable pedaling speed for me is around 30RPM, so I would use some belts & pulleys to step that up to 588 RPM (1:20 gearing). then connect the final pulley to the motor shaft and connect the motor leads via a diode (to prevent the battery from driving my bike) to the motor. Then I would start pedalling. Let's say the battery is discharged to 8V (2/3 of nominal); I would expect smooth sailing until I got up to 20 pedal RPM (2/3 of nominal) at which point I would expect to hit hard resistance as if someone suddenly attached a parachute to my back while I was accelerating. I would expect that if I changed my pedaling style from one that tries to maintain a constant speed, to one that tries to maintain a constant and comfortable torque load, my RPM would steadily increase as I charge the battery until I reach 30RPM and full voltage.

    But I have never done any of this, so I'm really just talking from my rear end.
     
  7. PackratKing

    Well-Known Member

    Jul 13, 2008
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    Hey Strantor !!... long time no talk -- how's this sound for the bicycle genny...

    I scored a 3/4 HP? PM motor, from a modern gas furnace, that had other PCB issues from getting wet [ drowned ] from exhaust stack condensation running back into the furnace... - the contractor had to eat that one :rolleyes:

    Thing is, upon a brief look into the motor, it appears to have been a PWM 3-phase, but I am likely looking at it wrong...but tapping into the wiring and spinning it w/ a pully on the shaft against a wire wheel, RPM not noted - it put up 150 volts, and I haven't messed with it since... or check what level of current that was good for.

    Main point here, is I have started building a stationary frame out of a wrecked mountain bike [ fair-to-middlin' machinist w/ necessary machines ] and plan to employ the chain derailleur system to enhance the effort needed to make it turn...
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Haha, you [Strantor] are what they call a "masher", as opposed to a "spinner". See here. Here too.

    Cyclists look for a pedal cadence of about 80-100rpm for peak efficiency. So I suppose I'd design to make 200W at that cadence. So if the generator needs 1600rpm to produce 200W, you'd need a 20:1 gear up to run at 80rpm at the pedals.

    There are generators wound for peak power at lower rpms, and I suspect that would be the right choice to make everything work better together. Big gear-ups are inefficient.
     
    Last edited: Oct 31, 2013
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Well, you're thinking from the perspective of a cyclist. I'm not a cyclist. I wouldn't want to have to don a spandex body suit any time I charge my ipod. :p

    P.S. keep in mind, pedalling 80-100 RPM, putting out 200+ watts on a stationary bike, you're probably going to give up the ghost long before the ipod gets charged. ...or maybe just me ;)
     
  10. wayneh

    Expert

    Sep 9, 2010
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    It's not just you. In the context of the OP's armageddon scenario, I can't see expending valuable food resources and human body wear and tear just to make a little electricity. Your energy would be better spent farming and arming.

    It wouldn't take much time on the bike for you to think of using the wind or a nearby stream to "pedal" for you while you sleep. I recall my grandmother describing how their windmill charged batteries for their radio.

    The one advantage I can think of for the bike is that it could be hidden and very private, compared to PV panels or a windmill.
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    Take the "f " out of "farming".

    Never thought of that... makes for a new line.:)
     
  12. PackratKing

    Well-Known Member

    Jul 13, 2008
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    Thank you for those two links... you saved me a lot of research :D
     
    Last edited: Nov 1, 2013
  13. wayneh

    Expert

    Sep 9, 2010
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    To paraphrase Newton, it is so very important to stand on the shoulders of giants. Translation: Read the literature. It is a rare day when you are working on a problem no one has worked on before. When you think you are, it usually means you didn't search with the right keywords. I've had the pleasure of finding new stuff in a research lab, and it is truly a precious experience.
     
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