Working solar panel vs. idling panel-what changes at panel?

red31 wrote:
I like this answer

Now what do you do with the electron-hole pair:


- You can do nothing: It recombines, emitting infrared (which is absorbed and becomes heat in the panel)

- You can use it to drive an electron through the wiring: Some of the energy goes into the load, some in to the panel resistance, and some into the electron-hole anihalation when a returning electron falls into the hole (across a much lower energy gap).

I do think this is the answer. What energy that goes into the load is subtracted from heating the panel or reflected as infrared into space. From reading this, shorting the panel or having it open circuit would have a similar result as far as the panel heating . The short circuit load would be entirely dissipated through panel resistance-and heating.

Could you point me to more info on the subject?

At this point I'm in the camp as you take useful energy from the panel, it cools (or reflects less infrared) to the degree of energy used. That energy the panel is producing has to come from somewhere. If the panel is exhibiting no changes while being 15% efficient at producing energy, we have a perpetual motion machine.

Guys with a whole roof of panels may be subtracting 1000 watts of heat from the roof area when charging those big batteries. Don't know how it translates in real world (some could be reflected anyway), but in theory..............

tpi wrote:
Could you point me to more info on the subject?

If there was ever a subject to which google was appropriate, this is it.

Best of luck learning about it. Not an easy subject, and I have my doubts the answers you seek will be on here.

I object to the panel cooling, I'll suggest that some photon energy is removed/used so it doesn't heat as much.

Goggle

http://www.reddit.com/r/askscience/comments/ye346/when_you_complete_a_circuit_with_a_solar_panel_it/

red31 wrote:
I object to the panel cooling, I'll suggest that some photon energy is removed/used so it doesn't heat as much.

Goggle

http://www.reddit.com/r/askscience/comments/ye346/when_you_complete_a_circuit_with_a_solar_panel_it/

Thanks-true-it wouldn't cool, it just wouldn't heat as much. But it is cooler relative to open circuit-by the amount of energy exported from the panels as electrical energy.

I appreciate your input on this thread. This is something I've wanted to know more about for some time..

The link is very interesting...

From Scientific American
"How does a solar cell turn sunlight into electricity?
In a crystal, the bonds [between silicon atoms] are made of electrons that are shared between all of the atoms of the crystal. The light gets absorbed, and one of the electrons that's in one of the bonds gets excited up to a higher energy level and can move around more freely than when it was bound. That electron can then move around the crystal freely, and we can get a current.

Imagine that you have a ledge, like a shelf on the wall, and you take a ball and you throw it up on that ledge. That's like promoting an electron to a higher energy level, and it can't fall down. A photon [packet of light energy] comes in, and it bumps up the electron onto the ledge [representing the higher energy level] and it stays there until we can come and collect the energy [by using the electricity]."

There are other articles that discuss the different materials in use like Gallium-selenide, Indium, and the mix of each to harvest power at the "junction" of the solar cell.

To theorize about the thermodynamic aspects of a module, you'd have to know the available photon makeup and transfer characteristics of the silicone, things that are way beyond my paygrade.

West - if we don't collect electricity from excited electrons, they will come down to their previous low energy level. This difference of energy needs to go somewhere, in idling panel - heat, glow etc.

Interesting! I see the current load on the panel will not change the light absorption properties of the silicon crystal so no visible change. The current carries away some power which tends to reduce the temperature but the remission of light (in the infrared range) from energized electrons that previously didn't make it out of the panel is reduced, reducing that cooling effect. These may well cancel each other out. If there is a reduction in temperature the flow of heat via convection and conduction will decrease and the temperature will quickly stabilize.

It takes a lot of electric power to equal what we think of as a small amount of heat flow so I doubt if there will be a noticeable temperature change.

Almot wrote:
West - if we don't collect electricity from excited electrons, they will come down to their previous low energy level. This difference of energy needs to go somewhere, in idling panel - heat, glow etc.

I would assume that the unbalanced excitation of free electrons morphs back into a balanced state when idling. If the bonds are weak or if the free electron is still "close" to the original structure, there probably is not a lot of energy dissipation going on.

Where I lose it thinking about this, is that this is not a chemical reaction but some voodoo between photons and the silicone structure. They do dope the cell to recover the energy to the cell's circuitry but this isn't a chemical reaction either, AFAIK.

The greater the panel efficiency, the cooler it becomes. A 90% efficient panel should remain close to ambient temperature. If the panel is not connected, its efficiency is 0%. It will have the highest temperature rise.