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# emergency flywheel generator

human power to power non-power tools
 (+2) [vote for, against]

I'd guess this is definitly baked somewhere but after some (lush) searching i haven't found anything close to this idea:

Everybody seems to be hyped to get some sort of solar charger for his travelling energy needs. But solarpanels are pretty big and I prefer not to have something the size of a medium-sized notebook just to power my cellphone on the go.

On the other hand there are these tiny flashlights that get their power from a crank and store excess energy in some kind of energy storage assembly.

What i propose is a low-output power generator powered by the human operator. Energy is preserved in a small flywheel.

The human body is supposed to be able to produce around 100W over a longer period with peaks at around 300W. When i turn a the handle on the generator for 5 minutes i get:

100 W * 5 min = 30kJ

If i assume that i can store all of this energy in a flywheel attached to a small electrical generator i could power a cellphone that draws around 3 W (rated at 6V and 0.5A) for almost forever:

30kJ / 3 W = 2.8 hours

Even at 50% effectively i'd be able to charge the phone for more than one hour, enough to do a full charge.

Now i guess the whole device could be made the size of a dish and weight a kilogram which whould be due to the size an mass of the flywheel. That is quite heavy for traveling purposes, but everyone who needs a mobile on the walk can be bothered to pack another kilo.

So ... why is this not baked anywhere? Do i miss some curial part? Are the losses due to friction bigger than what i estimated? Or does everyone today use one of these smart phones that require you to charge them every night?

 — fho, Aug 30 2011

Human power for your cell phone,but no flywheel http://www.bionic-power.com/
Does it count as baked if you can't actually buy it? [scad mientist, Aug 30 2011]

Another option that is "almost" available to buy. http://www.npowerpeg.com/

Weza http://www.batteryj...m/frwefrfopoge.html
Discontinued, but still available at some locations. [Klaatu, Aug 31 2011]

//heavy// unless it's hollow and you fill it with water when needed.
 — FlyingToaster, Aug 30 2011

 // that be leg power //

 bonus points for making this leg powered and compact. possibly some kind of stepper-like contraption

 // charge the mobile battery //

 i was hoping that the power could be used for different purposes too. There where actually two situations that got me thinking about this:

 First there was this year's festival summer and the guys with the big solar panel on there bus ... who weren't there and we where lacking power. A human powered generator for illumination and possibly a small soundsystem would be nice in such a situation.

 And a wooden carousel at the local medival market that was powered by two people (including me for one ride). Payload where 8 persons and all 'vehicles' where made from wood. There was a double crank in the middle and we got the whole thing to turn pretty fast for what felt like half an hour (but probably was just about 5 minutes ;) )

 // fill it with water //

good idea! then there would be the need for barriers inside the container to stop water motion.
 — fho, Aug 30 2011

 // help link: exercise gym //

 urgs ... i've been stalking the halfbakery for like 10 years now ... but i never have clicked the help link ... shame on me

i guess i'll just delete this idea
 — fho, Aug 30 2011

far be it from me to presuppose etc. but this seems outside m-f-d territory.
 — FlyingToaster, Aug 30 2011

 Hmmkay ... then i'll keep it :)

 A related (and maybe feasable) addition would be to make a small portable flywheel suitable for 'camping purposes'. And to use this as a collective collector for our annually festival camp. I guess there are about 4-5 qm of solar panels around that charge individual car batteries. On second thought ... maybe that's a better way after all.

But i guess flywheels are something that work effectively only when build huge.
 — fho, Aug 30 2011

Why a flywheel and not just turn the generator itself? You're wasting energy on the flywheel.
 — DIYMatt, Aug 30 2011

 //If i assume that i can store all of this energy in a flywheel// I would be making a mighty assumption.

You might want to remember that the way you store energy in a flywheel is by accelerating it. You can't just spin it at a constant rate - every time it goes around has to be quicker than the time before. Do that for 5 minutes continuously, and it's going to be going awfully quick. You can't do it in direct drive; there would need to be a transmission of some sort. A CVT with a very wide range, or an awful lot of gears.
 — lurch, Aug 30 2011

I linked two almost baked (but not actually available) examples similar to this idea. Neither uses a flywheel, but I agree with others that skipping the flywheel and just storing the energy in a battery would be a better solution. These are nowhere near 100W, but still usefull.
 — scad mientist, Aug 30 2011

Fitting a light cover around the flywheel and filling it with hydrogen (easiest source electrolysis), will not only protect it from dust but cut air friction losses by over 93%.
 — FlyingToaster, Aug 30 2011

Freeplay made the Weza [supposedly, that was the sound it made as you stepped on it..."weee-zah"]. 30W power from a stepping action. I understand that they deployed many to rural areas in Africa. <link>
 — Klaatu, Aug 31 2011

 // needs CVT // i was aware of that fact, altough i am not sure there many lightway CVTs out there. I like the NuVinci design, but i do not think you can get much range that way.

// Weza // aaah ... definitly baked then :) ... hmm... discontinued ... but maybe i can hunt one or two of these things done somewhere. Thank's for the hint!
 — fho, Sep 01 2011

 Someone on this site proposed pulling a string to generate electrical power, I think that would go well with this idea, it could be a leg powered string or not. Oh it was Things with Strings from this same category.

The advantage a flywheel could potentially have over a battery is faster charging. Putting a hundred Watts directly into your phone would probably kill it so you need a larger battery capacity than you actually use to charge it in a minute or five.
 — caspian, Sep 01 2011

Hmm... that brings me to the question: does joe fat use 'eaten energy' less efficient than bob workout? Or will they both be able todo the same amount of work just over different periods of time?
 — fho, Sep 01 2011

 //heavy// //unless it's hollow and you fill it with water when needed.// //good idea! then there would be the need for barriers inside the container to stop water motion.//

A flywheel that stored compressed air for ballast wouldn't need baffles and would still have energy stored after it's revolutions were depleted to warn you that you need to quit holding your chest and wheezing so you can get back in the saddle.
 — 2 fries shy of a happy meal, Sep 01 2011

 // filling it with hydrogen //

 // compressed air for ballast //

You *are* trying to make this go boom aren't you? ;)
 — fho, Sep 02 2011

So? Everything has failure modes. But some failure modes are more interesting than others.
 — mouseposture, Sep 03 2011

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