[Corvettaholic]

So during one of my many smoke breaks, I just had a revelation. Actually, just a really cool idea. So as you all know, solar panels generate electricity when exposed to light. Neat. So is there an element that behaves that way? Its silicon, isn't it? I remembering hearing about some sort of stuff that acts like a solar cell, but isn't. So, lets say you have threads, really fine threads, of this stuff. Or yarn or string or something. Anyway. So you have this photovoltaic string, and when exposed to light it is now a power source. One end of the wire is negative, one end of the wire is positive. Weave this junk into your clothes, and have all the the threads connected by a bus along the side of your body. Make sure its all nice and flexibile of course, because comfort is important. At the end of each bus on your sides, connect them together through your belt (with a wire in it) so you have a complete circuit. Bam. Wearable power that isn't bulky or noticable. Figure you only need .1 volt or so per thread, just add them all up to power a radio or something. You could even remove the buttons on your shirt and replace them with NiCd batteries in case you walk into a shady spot.

So what exactly makes a material photovoltaic anyhow? Do photons knock around electrons or something? Photons are awfully small though...

And yes, I do think of this crap out of nowhere. Maybe I have some wires crossed in my head or something.

[arnyk]

Silicon is one of the common ones used in PV cells along with other semi-conductors (like in computer chips and transisters) such as CdTe and CdS.

And you're right on the photons knocking around electrons part.  The solar cell uses the energy of the photons to "move" the electrons thus creating an electrical current.

By "doping" the silicon layers with impurity atoms (that reside on either side of silicon on the periodic chart), photons of light will eject electrons from one layer, where they are swept into the adjacent area.

Also besides the actual solar module you would need a system to convert the D/C to A/C and also to store unused energy in a battery.  Otherwise, you can't generate enough power "on demand" continuously using solar energy, especially with the unit size you are proposing.  All this would be pretty bulky, the smallest you can probably get (super expensive though) would be around the size of a backpack of sorts.

All this to power a radio??  

I LOVE it.  

[lemonoman]

Not a BAD idea, just kind of random.

A couple things to consider:

1. The electricity generated by photovoltaic cells probably isn't as much as you expect.  I remember seeing a cell and they told me what the voltage was and I was like, "That's IT?" ... maybe it's a high current or something...

2. I don't think the photovoltaic part of the cell is conductive...it just alternates a current back and forth which drives a generator or capacitor or something.  You might need an auxiliary wire for each photovoltaic thread you have...and maybe a generator thing...

3. Don't forget that long-term exposure to electric and magnetic fields is thought to cause cancer and whatnot.  I personally wouldn't wear a conductive suit...but then again I listen to an MP3 player and have a watch and cell phone, and those are probably just as bad, if not worse.

Good luck on your invention though...

[arnyk]

Argh you beat me on the edit!  Oh well, yeah add the generator to the bulk of the unit too.  

[Corvettaholic]

Well bulk of batteries isn't so bad, just a lot of little ones! Where would you put them? Wherever you normally have buttons or where weight isn't noticable.

As far as fields causing cancer... not too worried about it. I do smoke after all, and at this age I'm still mostly invincible. Besides, its just for proof of concept. I don't this would ever be safe enough to market it.

Don't think I need a DC to AC converter either. I'm fine with having simple DC power available, and there's plenty of el-cheapo radio's that work off of it too. Since batteries already are DC, that reduces a lot of weight on the conversion junk.

About the generator... any ideas how to do that? So if there is a thread of silicon suspended in the air, it will do nothing. Dope the silicon with something, and it still will do nothing. Hook up some sort of generator to that thread and all of a sudden the generator makes power. I know the voltage is really low, commericial cells are something like 1.5V I think. But its the current that I want! Current is good for electromagnets too. I think this suit would be perfect for grabbing stuff with a heavy duty magnet, but it might get a bit warm. But back to the generator: why not have a secondary thread of copper follow the silicon thread? Since the silicon thread is wobbling like crazy, the copper wire is right there to 'catch' the current!

About silicon though, how flexible and strong is it? Will a thread of it survive if its woven into clothes? Maybe pairing it up with ultra-thin copper wire will make it better? Not sure how to mate up copper and silicon though, because I want to use extremely thin stuff since I'd like to wear it. Weight is bad.

[xiankai]

how would u wash such a fabric eh? wait till its raining and u may get a small electric shock

[Dude]

Not as far-fetched as you might think.  Polymeric photovoltaic cell research has been going on for some years now.  Check google and you should find a good introduction.  If you can make the polymeric material into a fiber, retain some level of efficiency (or improve what is out there, polymers are not very good currently), and work out the practical details, you might attract some interest from investors.  Probably not from Duracell- since that would be taking some of their business.

[Corvettaholic]

Another thought just popped into my head this morning! Well since using the solar method would require a generator of some kind to catch the vibrating current... why not use motion instead of solar? Kind of like a rolex or something. Since when you move around, your clothes will bend a bit too, isn't there a way to generate a voltage with that? I'm fairly clueless as to how the piezoelectric effect works, or even how a rolex maintains the time just by moving your wrist around...

[lemonoman]

NOW we're talking...that piezoelectric effect thing while walking might have something to it...

Like with footsteps...maybe you could put a piezoelectric crystal on the bottom of your shoe...and it would produce a tiny tiny current everytime you took a step...then this current gets stored up somewhere, and you can charge custom batteries as you walk!

Thats awesome!

[Corvettaholic]

I was reading up on piezo stuff and those battery-less watches. Those watches apparently just use motion to wave some gears around, which is too mechanical for this application. So thats out. But the crystal in the shoe... I like that!

Now how does the math work with piezoelectic crystals? Need a certain amount of pressure to 'make' current? How is the voltage determined? Maybe we can still weave stuff in clothing, but instead of the power source, its just the carrier. Weave in a bunch of ultra thin wires to carry the charge from the crystal in the shoe, to a belt-mounted battery unit thingy. About the amount of pressure needed on the crystal: if there are crystals that barely need any physical contact to make power, you could always put those somewhere that they'll get banged up a lot. Like around your knees or something.

[Grumples]

For your solar panel jacket, why not just skip the complicated and expensive idea of woven strands of silicon, and just mount ordinary solar panels to a packpack or such?  It's not very cool, but it'll work.

On a related note, why not try to use the temperature difference between your body and the ambient air? I can think of a few far-fetched ideas, but the easiest would be just a process whose name I can't remember.  Basically, the concept is to have a loop of wire, one half copper, one half iron (I think) with one part in something relatively hot, and the other in something relatively cold.  in that loop, you put whatever takes the charge (such as a battery).  Simply the difference in temperature will cause the electrons to start moving, although the power would be low.  

[xiankai]

the surface of our body isnt very hot, and to obtain temperatures closer to that of the body (eg. 36 degrees celsius), u'll have to put the whatever conductor u choose to use in a inappropriate part of your body, heheh.

[lemonoman]

Oh man, I was SO all-about thsi idea...it's perfect!

Then I went to look up the math behind piezoelectrics and stuff, and found THIS LINK.

Turns out MIT beat us to the punch.  Those Bah-stords, lol

Boooooooooo!

[Corvettaholic]

Well instead of putting the crystal in a shoe, we should put it in a glove so whenever you punch somebody, you can power your radio that way! But seriously, I like the idea of using a temperature difference to get power. I'm familiar with how stirling engines work, but not electrical generation with temperature. Since I live in Arizona and my patio is currently 110 degrees fahrenheit, I could be the cold surface and the ambient air can be the hot surface. Just have your circuit be smart enough to figure out which side is supposed to be what so it'll work whether you step into a freezer or outside in Phoenix.

[arnyk]

We could probably exploit athletes for this eh, like for the glove punching just use boxers.