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Some questions:

Can LED light provide same amount of energy as sunlight?

Can humanity get rid of the sun and charge solar panels from LED light alone?

If this is feasible, this would be truly sustainable energy. Have two panels of the same size, bottom one made of solar panel and the top panel made up LED light. Two panels facing each other.

As the LED light panel provide light source, the solar panel produces energy to make the LED light shine, the excess energy the LED bulbs doesn't need can be immediately consumed or stored in a battery.

This idea would be ideal for places that cannot reached by sunlight, like underground parking spaces and during evening hours.

  • Using artificial lighting with a solar cell is not perpetual motion. Perpetual motion means that once to start it, it does not stop. An artificial light source has a life span and so does a solar cell. If both the LED and the cell stop producing, it can not be perpetual motion. – user2815 Nov 29 '15 at 22:00
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There are a number of questions there.

"Can LED light provide same amount of energy as sunlight?"

In total, no, at least with humanity's available resources. The sun is kinda big. Per unit area? Sure, if you use enough LEDs and focus them tightly enough.

"Can humanity get rid of the sun"

Probably not, within our currently available technology ;-) Even destroying the Earth is a hard problem.

"...and charge solar panels from LED light alone? If this is feasible, this would be truly sustainable energy. Have two panels of the same size, bottom one made of solar panel and the top panel made up LED light. Two panels facing each other."

No. What you are suggesting is a perpetual motion machine (only without the motion). The efficiency of photovoltaic panels is somewhere in the region of 15%, so about 85% of the light energy is lost rather than being converted to electricity. The efficiency of the LEDs is also far short of 100%, so not all of the electricity is converted back to light. Morover, the second law of thermodynamics means that no matter how good technology gets, neither of these devices will ever be 100% efficient, so this will never work.

(In this context, a simple and helpful way in which to think of the 2nd law is perhaps: "You can't get back more than what you put in. In fact, you can't even get back what you put in")

(apologies to anybody who finds this answer too flippant. I'm in that sort of mood!)

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    I think perpetual motion machines deserve flippancy. – Móż Mar 22 '14 at 9:14
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    You wouldn't believe how many customers have asked me the same question and how many times I've had to explain this. Some of them have told me that they were going to try it anyway. When it doesn't work, instead of saying "Oh, you were right," they say "hmm, I must have done something wrong. It will work next time." – Maxfield Solar Mar 10 '16 at 15:22
  • In the same vein, I've had a few conversations where people simply wouldn't accept that putting windmills on top of cars/trains/buses doesn't give you more energy than you put in. – LShaver Jul 19 '16 at 0:43
  • Note that "indoor farms" suffer from exactly this problem. Except that instead of 15% efficient solar panels they use 5% efficient plants, then throw away half what they grow. – Móż Jul 19 '16 at 3:17
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Obviously you are not going to get a net return on investment on the energy you put into your LED. If you could, you'd have a perpetual motion machine which is impossible.

However, there are cases where doing this makes sense, and where you probably have such devices around. For example, some small portable electronics (calculators, for example) will use amorphous solar cells to power them in place of batteries.

In other words, the LED is not a replacement for the sun but it may be fine as a way to use light you are already using in place of batteries for some light work. Think of it as energy recycling.

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I've had the same idea - using artificial light to power a solar cell. It has been done with an incandescent bulb, but that throws heat and draws a lot more current. An LED would be ideal because of it's low power consumption. Solar cells use certain wavelengths of the light spectrum. An incandescent bulb produces all the wavelengths the sun does, but in different amounts. LEDs produce most of the wavelengths as well, but in different proportions. So, from a scientific standpoint, LEDs will probably produce the correct light to charge a solar cell.

Regarding "The Sun Is Kinda Big" issue, it's hard to dispute that. :) However, if you were to introduce passive components like mirrors, magnifiers (remember burning ants on the sidewalk with a magnifying glass?) and prisms (to optimize the correct wavelengths), it might be possible to get a solar system that runs 24X7. I'm not sure it's ever been tried with an LED light.

Is seems like it might also be possible to design a wind power system that powers and is powered by a DC fan. ;)

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    You can use as many mirrors, lenses, etc as you like, but the fact that remains is that neither LEDs or photovoltaic panels are 100% efficient, so you will always lose energy. – Flyto Jul 19 '16 at 0:50
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    Mirrors and lenses also lose energy, so more of them is worse unless you collect enough extra energy to compensate. Since your input is fixed, you should use as few collection aids as possible.. – Móż Jul 19 '16 at 3:18

protected by Community Jul 19 '16 at 4:55

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