Thought Experiment

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Hydrolisk
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Thought Experiment

Post by Hydrolisk » Sun May 25, 2008 10:22 pm

While I was reading a few Wikipedia articles on perpetual motion, I suddenly came across the idea of a solar energy collector.

Basically, a small number of solar cells (maybe spherical in overall shape?) is placed within a ball of one-way mirrors (the glasses that only allow light through one-direction, whilst the other side is a mirror), which has their reflective sides facing the solar cells.
There might be a few reflective wires that attach the solar cells with a battery or what-not.

The original idea was a solar collector that can collect a large amount of solar energy cheaply.

What are your opinions on this?

-Personal Reflection: I later found this rather trivial, as it seemed to be the equivalent of a plain solar cell without all the fancy mirrors and that stuff. Can anybody elaborate?
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Hydrolisk
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Re: Thought Experiment

Post by Hydrolisk » Tue Jun 03, 2008 7:40 pm

*Bump.*

It's been more than a week! :o
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Oxygen
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Re: Thought Experiment

Post by Oxygen » Tue Jun 03, 2008 7:59 pm

From personal experiences with perpertual motion, it doesn't exist. Yes, you can create a system that'll create its own energy, literally, but there's always a loss somewhere. With wheels and stuff, it'll be the friction with air. With a solar battery, like you're trying to create or study, there will be flaws in the wires, or glass, or whatever--. You'd need supraconduction for it to pass thru the wire perfectly, for instance, and perhaps the system could fuel its own energy in order to create that, but it'd require an immense prototype!

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Re: Thought Experiment

Post by Hydrolisk » Tue Jun 03, 2008 8:12 pm

I personally think that perpetual motion is possibly possible somewhere in the universe, but that wasn't exactly my question.

My question is more like, "is what I have thought up more efficient than current solar panel fields and what-not?"
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Oxygen
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Re: Thought Experiment

Post by Oxygen » Tue Jun 03, 2008 8:27 pm

Hydrolisk wrote:I personally think that perpetual motion is possibly possible somewhere in the universe, but that wasn't exactly my question.

My question is more like, "is what I have thought up more efficient than current solar panel fields and what-not?"
Ahh, I read it twice now, I see what you mean. You're trying to get light into a only-way in mirrored ball? I doubt that's possible, since the one-way mirror will still allow the light out, even though it might be very dim.

What you'd need to do is to create a 100% mirror ball, and find a way to put light into it. But err. You'd need to close it at... 300 000 km / second. That's the only problem. Other than that, sure!

But then again, since the light would warm the mirror, it'll lose energy.

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The Colonel
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Re: Thought Experiment

Post by The Colonel » Tue Jun 03, 2008 8:52 pm

If the mirror was perfect the light wouldn't warm it, but I'm pretty sure that a perfect mirror is impossible.
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Hydrolisk
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Re: Thought Experiment

Post by Hydrolisk » Tue Jun 03, 2008 9:50 pm

WHAT THE HELL. :evil:

Sorry, but it's either I'm getting impatient or people aren't understanding my question.

I want to know if what I have thought up of is more efficient that what people normally use of solar collectors!?
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The Colonel
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Re: Thought Experiment

Post by The Colonel » Wed Jun 04, 2008 4:52 pm

No, it really wouldn't help any significant amount.
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polishgangsta
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Re: Thought Experiment

Post by polishgangsta » Fri Jun 06, 2008 4:05 am

well, i think you misunderstand how a one-way mirror works. IIRC it reflects the same amount of light on both sides (as it a pane of glass with a thin metal coat) and the illusion of being "one-way" is only because one side is much more brightly lit than the other. Unfortunately, the bright side will almost always be the side facing the sun.

Now, from what i understand about solar energy, there are two types of devices for harvesting the sun's light. THe first focuses light on a central heat engine. In this case, most of the light hits the heat engine and the mojority of the inefficiency comes from the heat engine itself (most heat engines are very inefficient). (Also, most glass reflects IR spectrum radition- which basically amounts to reflecting heat)

The second type uses the photoelectric effect to convert em radiation directly into electricity. While it is possible that your setup might cause the em radiation to stay in contact with the photovoltaic cell for a longer time period, but the real problem in PV cells is that they can only efficiently absorb light of a specific wavelength.

I'm no professor, but i hope that helps (and i hope I didn't make something up :D )
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Oxygen
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Re: Thought Experiment

Post by Oxygen » Fri Jun 06, 2008 9:41 am

polishgangsta wrote:well, i think you misunderstand how a one-way mirror works. IIRC it reflects the same amount of light on both sides (as it a pane of glass with a thin metal coat) and the illusion of being "one-way" is only because one side is much more brightly lit than the other. Unfortunately, the bright side will almost always be the side facing the sun.

Now, from what i understand about solar energy, there are two types of devices for harvesting the sun's light. THe first focuses light on a central heat engine. In this case, most of the light hits the heat engine and the mojority of the inefficiency comes from the heat engine itself (most heat engines are very inefficient). (Also, most glass reflects IR spectrum radition- which basically amounts to reflecting heat)

The second type uses the photoelectric effect to convert em radiation directly into electricity. While it is possible that your setup might cause the em radiation to stay in contact with the photovoltaic cell for a longer time period, but the real problem in PV cells is that they can only efficiently absorb light of a specific wavelength.

I'm no professor, but i hope that helps (and i hope I didn't make something up :D )
Very well said, though! And this explains exactly why we can't ONLY rely on sun to get our energy -- clouds, night, and ineffectiveness of light energy gathering system. Which is what I believe hydrolisk is trying to create, or at least, figure out.

I've personally thought about it, and our best bet, as humans, would be to use various sources all at once. Imagine, a structure that could use geothermy ( warmth and movement of the earth as energy ), wind, water and sun. With the steady income of earth and water, you'd always have some power -- and water is actually very substancial to work fine on its own ( 95% of our electricty comes from water, where I live ) but warmth and wind would obviously help.

Now, why aren't we doing this? Too costly!

I know, this is quite off topic, but I just thought I'd share.

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The Colonel
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Re: Thought Experiment

Post by The Colonel » Fri Jun 06, 2008 7:58 pm

Ironicly, with the money the United States had spent on The War on Terror we could've also built enough eco-friendly plants to power the whole world. Hell, 1 square mile of solar panels could generate enough power even with the day-night intervals according to Scientific American.
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Oxygen
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Re: Thought Experiment

Post by Oxygen » Fri Jun 06, 2008 8:38 pm

The Colonel wrote:Ironicly, with the money the United States had spent on The War on Terror we could've also built enough eco-friendly plants to power the whole world. Hell, 1 square mile of solar panels could generate enough power even with the day-night intervals according to Scientific American.
I know... I know... sad isn't it?

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Re: Thought Experiment

Post by Hell_Tempest » Fri Jun 06, 2008 8:49 pm

It costs two billion dollars for one week of war.
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TheDeathstalker
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Re: Thought Experiment

Post by TheDeathstalker » Thu Jul 10, 2008 7:09 pm

First, i apologize for the thread necromancy...

Second... Having a sphere reflect light around so that it hits solar panels repeatedly won't work because you're missing a very fundamental part of what exactly an efficient solar panel does. When incoming light hits a solar panel, it does so with a set energy based on the wavelength of the light. When this light hits the panel, some part of the energy is absorbed by the solar panel. When this energy is absorbed by the solar panel, it can free an electron within the solar cell (the actual process is a bit trickier, but close enough). This freed electron, as well as many others that are freed by the same process, are what make up the current generated by such devices. However, the energy absorbed by the solar panel is lost by the photon, and in a fairly optimal setting, it takes a majority of the energy from the photon. If we were to try using that same photon again to free another electron, it wouldn't have enough energy to free another electron. Essentially, making such a sphere would probably lose you energy over an area because you would lose surface area by using a sphere, so no, it is less efficient.

Third... Perpetual motion is possible, but only at absolute zero (or effectively well below the fermi energy). This is because anything with a temperature is losing some energy because of friction resulting from the vibration of the atoms. This is (somewhat) like what Dusk is doing, if you have a free floating object in space that's rotating, if there is any part of it that is sloshing around, rotational energy is lost. So while wheels and gears may not be creating friction, you are still losing minute amounts of energy from subatomic motions, so the motion is not perpetual.

As for Perpetual Energy, the answer is clearly no. The energy of a system is conserved in all circumstances*, so no system can create more energy than it began with, it's as simple as that.

*Note: the law of energy conservation can be broken over very small time intervals, which explains how Nuclear Strong forces and such work, but beyond these time intervals it is again constrained, so barring really skilled advanced quantum physics, i don't think there's a way to exploit this.

I think that's all... If you're wondering why I actually know about this stuff, it's the topic of the research I'm doing for the summer with UF's Quantum Theory Project group. Sadly I haven't gotten to do anything but read about this stuff yet.
And though you come out of each gruelling bout,
All broken and beaten and scarred,
Just have one more try—it’s dead easy to die,
It’s the keeping-on-living that’s hard.

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