Scale up the Faraday Flashlight model for household applications?

Question

I want to build a unit large enough to be able to recharge a battery powering an inverter so I can run regular 110-120V appliances. I'm thinking something that will harness the rotational power of a bicycle (21+ gears) and move a magnet thru the solenoid (either direct rotation at the wheel, OR movement in a verticle tube and use an upward force to move the magnet up, with gravity pulling it back down, to simulate shaking) to generate the electricity to recharge a battery.

I'm wondering why this hasn't yet been done and think it could be impracticle if not impossible. But I can't get the idea out of my head.

Can anyone see anything wrong with this idea?
I have the battery (12v, 4.5 A) and inverter. I have a solar panel but that takes too much time to recharge.

Answer 1

If you "average guy" level of fitness, you can generate maybe 200 watts for an hour. Maybe. As you build up your fitness, if you achieve professional bike racer levels of endurance, you could up that to 300 watts for 8 hrs. To generate that power, you would have to eat something on the order of 8000 calories per day (assuming around 1000 calories per hour). Charging a battery, assuming no power losses, you could then run one 100W light bulb for 24 hrs. Tomorrow, you get to do the same thing again.

Happy riding!

Answer 2

In order to calculate exactly how many turns, etc. you would need in your solinoid to get a particular voltage you would need to use Maxwell's Equations. I can't talk you through them because I have yet to take calculus :)

I can point out, however, that a wall outlet, at what I think is 10 amps and 115 volts therefore has 1150 watts going through it. Now in order to provide this kind of power with an inverter you will need a little more than that because some energy will be lose in the inverter itself.

In the end all, the idea is great in theory but, unless you have AMAZING leg muscles I think you might be better off trying to power something smaller.

That said, you may be able to change some products, like a computer for example, to run off fewer watts since the power from the wall has to go through the transformer anyway. So if you find out what the amps/volts the transformer puts out are and then provide that with your bike you may be able to power it when you ride.

Thats just a theory but I think you may have more luck with that.

Answer 3

Lots of people have thought of this and quite a few have built them. Most if not all of them used conventional rotary generators or alternators rather than the Rube Goldberg device you described. A conventional generator would be far more efficient than what you have in mind.

The reason that very few are actually used is that it's not a practical idea. An ordinary person can't produce very much energy over the long haul. And people get bored after a while.

The most practical idea I've heard of is someone who needed more exercise. He hooked his bicycle/generator to a small TV such that the TV would only work when the person was pedaling.