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

[tpi]

Just a theoretical discussion-

You have a solar panel producing full power to charge batteries. Versus an identical panel on an open circuit adjacent.

The working panel is essentially moving energy from the surface of the panel to the work. The other one isn't. Nothing free in energy transfer.

If you're up on roof observing these panels, what is different about the working panel vs. the idling panel? Is the reflectivity of the idling panel different? Is the temperature of the working panel less? It would have to be something..right? If they were both identical in reflectivity and temperature, then you would be violating some thermodynamic law....?

[red31]

What causes atoms to move?

[grizzzman]

12thgenusa wrote:
I agree with tpi. If 1000 w/m^2 is striking the panel then 1000 w is heating the panel assuming no reflection. If a 15% efficient panel shuttles away 150 w there is only 850 w left to heat the panel. Should be 15% cooler than an open panel if everything is linear. Now assume the panel could be 100% efficient. All 1000 w are shuttled away. What is left to heat the panel?

The panel temp is an equilibrium between how much energy is absorbed and how much is transferred or rejected to the environment.

The panel producing power won't look any different but should be slightly cooler than an open panel.

Seems to me that if you have atoms in motion it would create heat. Please explain how this isnt the case?

[12thgenusa]

I agree with tpi. If 1000 w/m^2 is striking the panel then 1000 w is heating the panel assuming no reflection. If a 15% efficient panel shuttles away 150 w there is only 850 w left to heat the panel. Should be 15% cooler than an open panel if everything is linear. Now assume the panel could be 100% efficient. All 1000 w are shuttled away. What is left to heat the panel?

The panel temp is an equilibrium between how much energy is absorbed and how much is transferred or rejected to the environment.

The panel producing power won't look any different but should be slightly cooler than an open panel.

[westend]

tpi wrote:
Just a theoretical discussion-

You have a solar panel producing full power to charge batteries. Versus an identical panel on an open circuit adjacent.

The working panel is essentially moving energy from the surface of the panel to the work. The other one isn't. Nothing free in energy transfer.

If you're up on roof observing these panels, what is different about the working panel vs. the idling panel? Is the reflectivity of the idling panel different? Is the temperature of the working panel less? It would have to be something..right? If they were both identical in reflectivity and temperature, then you would be violating some thermodynamic law....?

You're ecuating reflectivity (or it's opposite, absorption) with module power Neither have much to do with the production of power in a solar cell. It is the structure of the silicone interacting with photons and the imbalance in the silicone junction that makes power. Better explanation here: Physics.org.

Unless your eyes are from the planet Transistorus, the surface of the module will remain constant whether unloaded or seeing a load.

[SCVJeff]

The panel glows green when unloaded

[tpi]

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).

That's interesting. The way I read that is the panel would actually cool off under load.

[red31]

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).

[tpi]

If the panel is 14% efficient, then somehow 14% of the light energy falling on it would have to be exported..right?

If a panel is in open circuit, no energy is exported.

I'm just trying to get a handle on how that shows up at the panel. If the panel had exact same reflectivity, and measured exact same temperature (or higher), yet it was giving 14% of the light falling on it as electrical energy-then it would seem we have something which violates the law of physics...

[time2roll]

Similar to a battery. The connected battery powers your flashlight. The other battery just sits.
You will observe nothing what so ever.

[Ed_Gee]

tpi wrote:
Just a theoretical discussion-

You have a solar panel producing full power to charge batteries. Versus an identical panel on an open circuit adjacent.

The working panel is essentially moving energy from the surface of the panel to the work. The other one isn't. Nothing free in energy transfer.

If you're up on roof observing these panels, what is different about the working panel vs. the idling panel? Is the reflectivity of the idling panel different? Is the temperature of the working panel less? It would have to be something..right? If they were both identical in reflectivity and temperature, then you would be violating some thermodynamic law....?

In your " theoretical " example, the working solar panel is producing current flow to your batteries. The un-connected panel is not. Theoretically the temperature of the working panel should be minutely higher than the non-working panel due to current flow through it's internal resistance, ALL OTHER THINGS BEING EQUAL. However I doubt you have the equipment or the procedural knowledge to measure this tiny difference in temperature. There is absolutely no physical difference in the two panels that you can detect visually.

[Golden_HVAC]

14% Efficient - that has to do with the 'rated output' power and the typical lab test input of 1000 watts per square meter.

So if the panel is putting out 140 watts per square meter, it will be considered 14% efficient.

Some panels are a little more efficient in low light cloudy conditions, because they are more square feet for a given rating at 1000 w/square meter. But in clouds, where it might be only 500 watts per square meter, the flexible solar panels will collect a little more wattage than a polycrystalline panel.

So in cloudy conditions a 150 watt flexible panel might put out say 50 watts, the poly panels rated at 14% might only put out 40 watts under a cloudy condition at 500 watts per square meter.

I measured the watts per square meter in San Diego CO in Boulavard, and also in Lakeside close to 1 pm in January. At 3,800' elevation the W/M was close to 950, while in Lakeside about 45 minutes later it was only 860 W/M. This indicates that you are much more likely to get 1000 watts per meter at a higher elevation.

Also enhancing the solar panels is cold temperatures, wind helps a lot too! I mounted my panels about 1" above my roof, so that air can circulate below the panels, and keep them as cool as possible.

When the solar panel is not connected to 12 volt battery or load, nothing happens to the power that 'might have been' generated. .

Good luck!

Fred.

[NinerBikes]

tpi wrote:
I did read some general stuff about solar panel function-but didn't see that specific question answered. Somehow there has to be a physical change at the panel whether it is loaded or not. What 14% efficient? That energy is going away from the panel..

My guess would be reflectivity. If someone turned panel off and on I wouldn't be surprised if an observer could see it...

Start measuring, and get back to us, tell us what you find.

[2oldman]

Perhaps you're equating a panel with a computer chip, which gets hot when it's working. ..?

[tpi]

I did read some general stuff about solar panel function-but didn't see that specific question answered. Somehow there has to be a physical change at the panel whether it is loaded or not. What 14% efficient? That energy is going away from the panel..

My guess would be reflectivity. If someone turned panel off and on I wouldn't be surprised if an observer could see it...

[2oldman]

There's no circuit so there's no electron flow. What that has to do with temperature or reflectivity is beyond me. You could always look up 'how a solar panel works.'