Shoesies that recharge batteries

[the.fee.fairy]

I was reading this topic http://selfsufficientish.com/forum/view ... sc&start=0

but it was locked (and for good reason) BUT, i wanteed to ask about these battery charging shoes!!

There was talk that they had to be compressed to work - much in the same way as those really cool kids shoes that flash, right? So, electricky people...would there be a way of turning the flashy things round to make it so that instead of using battery power, they provided it?

It'd be might handy for when the battery on my MP3 runs out, or my camera!!

And it would give me a reason to buy the really cool flashy shoesies...i want a pair desperately, but they only go up to a size 2...2 sizes too small..

[Muddypause]

I did give some thought to that shoe recharger idea at the time. Trying to figure out exactly what is going on when the process of walking is converted into electricity required me to excercise my brain in ways that hurt.

There is no reason why it couldn't work OK, but as ever, you do have to remember that you will not be able to get anything for free - walking will, in fact, be a little harder than normal, and it is this extra effort which is being converted into electricity (this would be quite apart from the extra effort require to hoick about a shoe weighed down with a generator, some sort of drive mechanism, and the batteries you are recharging).

Basically, you have to have some sort of mechanism to make the dynamo in the shoes work. You could do this by having a compressible sole, so that when you put your weight on it the sole compresses, giving you some 'invisible' motion that could be used to drive the dynamo. The trouble is, it's not really invisible - the next step you take will effectively be up to a higher step. It may only be a few millimeters, but over a thousand steps, that will have added up to a few meters. It would be equivalent to constantly walking up a slight hill. And I reckon you'd have to do quite a lot of walking to recharge even a small battery. Rigging a bicycle dynamo up to do the job, and cycling would really be a more effective solution.

Regarding those flashing shoes - I've never felt the need to buy any myself, but I reckon they would utilse what is called a piezo-electric device to light up some diodes (LEDs). A piezo-electric device is usually a thin sliver of quartz or some ceramic that will give out a charge when pressure is applied to it. You may be more familiar with such things in gas cooker lighters (press the button to get a spark), and they are also in some types of microphone, or pick-up cartridge, turning vibrations into electricity. Some of these devices can produce high voltages, but the actual charge is very small, and it only lasts for a fraction of a second at a time - good for making pretty sparks or lighting LEDs, but not much good for charging up batteries, I'm afaird.

You could always buy thoes shoes on the pretext of doing some scientific research - take them apart, work out how they work, and then put the mechanism into a pair that fit you.

[the.fee.fairy]

I saw some instructions once that told you how to take them apart and put the lights into adult shoes, but they looked extremely complicated!!

I wondered how they worked, because kids don't seem to have a problem walking in them.

[Muddypause]

Thinking on about this, if piezo-electric material was used to replace all or part of the sole, rather than adding to it, such that the overall flexibility and compressibility remained unaltered, then you probably could generate a small amount of electricity, without adding to the overheads of effort. The piezo-electric elements could respond to the flexing of the sole, as well as just the pressure of weight applied to it when you stand on it.

I'm going to get another headache trying to fugure this out, now, but I reckon that the effort required to flex the sole of your shoe as you walk would normally simply be lost as frictional heat. Piezo-electric material would convert that otherwise lost energy into something more useful. Probably still only talking about very small amounts, though, and it assumes that there is some PE material with the same flexibility as shoe sole.

How about roller skates with a built in dynamo?

[Muddypause]

It looks like you're not the only person thinking about this, FF.

http://www.media.mit.edu/resenv/power.html

I haven't looked at the videos it links to, but it says of the piezo-electric shoes "...average powers of 10 mW." This is really a very small amount of usable power. Of the shoes with a built in dynamo it says "...it's not very easy to walk with", which is pretty much what I had thought.

But it does make the interesting point that the energy requirements of microelectronics continually decreases, so there might be a future for this sort of thing before long.

[Milims]

My daughter has a pair of size 4 flashy trainers - but they are kind of pink - and since my mam put them thru the washer they don't flash any more!!! The thing is its possible to have larger than size 2!!
I wonder if its possible to create flasing trainers on the Farahday principle of creating electricity - the only thing is they would probably only work if you moon walked or pranced like a horse everywhere you went!!!

[wulf]

So how about marketing these battery recharging shoes as good for the environment (free electricity) and good for you (more exercise)? That could be a winner... ;)

Wulf