Odd question regarding solar panels.

[Javaman]

as the worlds ice sheets melt, that lowers the reflectivity of the suns rays.

we build more blacktop parking lots, thus increasing the absorption of heat.

Okay, solar panels, by and large are dark. They aren't solar heaters but absorb the "rays" if you will, and because they are dark, will they also absorb heat?

wouldn't it be better to build a solar panel that is of a light color to reflect back the heat?

I'm no scientist, don't claim to be one and don't play one on tv.

So if this is a colossally dumbass question, pardon my ignorance.

[VLC]

1. Wow.

What is the purpose of solar panels? Is it to reflect heat back?

[Greyskye]

2. No.

The purpose is to convert certain frequencies of sunlight into electricity.

[Dora]

3. Solar panels generate electricity.

Solar panels generate electricity by "collecting" the sun's energy and converting it to electricity. That's the best way I can describe it. I'm not a scientist or a solar expert, but we intend to install a solar array on our home as soon as we can afford the upfront expense.

Solar panels are amazing. They can be configured to suit needs of any size - from stand-alone highway signs in the middle of nowhere, to single residential homes, to grocery stores, to office buildings...

The power and potential of solar energy is amazing.

[VLC]

5. I know... did you guys read the original post??

[Javaman]

10. did you? nt

[Dora]

14. I read the OP, but I did not know the answer to the OP's question.

I did, however, have enough basic knowledge to answer your question.

So? :shrug:

[Javaman]

4. Thanks for the snarky remark, but you missed the point entirely. nt

[VLC]

6. Was the point that you think they should be light colored to reflect heat back?

Because that's what you said.

[Javaman]

8. Yes, but I'm not talking about solar heaters. sigh. Solar energy panels. nt

[VLC]

11. Right.

[Javaman]

12. ???? nt

[kestrel91316]

20. If PV efficiency drops when they exceed a certain temp, this could

be an interesting angle and it is a VERY valid question.

Thanks for contributing so eloquently to the dialogue. You're an angel.

:sarcasm:

[OKIsItJustMe]

7. I don't think it's "a colossally dumbass question"...

Let's assume for a moment that the solar cells are 100% efficient in converting light to electricity. (They're nowhere close, but this is a thought experiment.) All of that power will eventually become heat. Whether you use it to power your toaster, or your TV or your electric car, it will all eventually become heat.

A solar cell absorbs light to work. (The power has to come from somewhere.) The more light is absorbed by an object, the darker it looks.

If a solar cell reflected 100% of the light which struck it, it wouldn't generate any heat. Unfortunately, it also wouldn't generate any electricity.


Okay, so solar cells sound bad. They heat up the Earth! Compare this however to generating electricity by burning fossil fuels. The normal way to generate electricity using fossil fuels is to burn them, generating heat which is used to make steam to turn turbines. It also generates CO₂, which means you both warm the earth, and generate a gas which helps trap the heat. The electricity that is generated eventually becomes heat (you can't avoid this.)

Nuclear power also works by generating heat, which is used to generate steam to turn turbines. Those massive cooling towers we associate with nuclear power are dumping off waste heat. The electricity generated eventually becomes heat itself.

Wind power doesn't work by generating steam. Electricity is generated directly, but that electricity eventually becomes heat.

Here then is the difference. Power generation frequently creates waste heat. Any power you use becomes heat. Burning fossil fuels however also traps heat in the atmosphere.

[Javaman]

9. I'm talking about the panels themselves.

The power generated from solar cells doesn't come from the heat. I'm talking about the dark color of the actual panel.

exhibit a: solar cell panel is black. it generates energy but reflects absorbs heat due to it's color.

exhibit b: solar water heater is black to absorb heat to heat the water.

exhibit c: solar cell panel is white. it generates energy but reflects back heat.

That's my point.

[OKIsItJustMe]

13. Yes, I understood your question

A 100% reflective solar cell (let's call it "white") would not generate any power.

It needs to absorb light to generate electricity.

[Javaman]

16. Okay, I see what you are saying, but...

since solar power is derived from the protons and not the heat in the solar rays, shouldn't a white panel have no effect upon the protons?

[skids]

25. No, heat in sunlight is light...

In the case of sunlight, the "heat" is light. It's either the type of light (infrared) that we call heat, or it's the type of light that will become either heat or electricity once it hits a surface that absorbs it.

There are indeed solar cells that are not black and do not turn the extra light into heat:

http://www.treehugger.com/files/2005/10/solar_power_gla.php

...these turn some of the light into electricity and let the rest through. If you put a white sheet under them, they'd reflect some of the light back.

But they are not as efficient as the black panels, which matters when roof space is tight.

The reason why none of this matters, though, is that the amount of heat emitted by enough solar panels to power our entire civilization would be completely insignificant compared to all the parking lots, roofs (which are usually black or grey) and albedo changes due to less snow and ice cover. It really is not a factor.

[kestrel91316]

21. You are probably interested in just reflecting back the infrared rays.....

Interesting question. Probably would adversely affect efficiency......

[Javaman]

23. There you go.

Like I said, I'm no scientist LOL. You hit it right on the head.

thanks :)

[OKIsItJustMe]

15. Back to the basics

You've got to look at the fundamentals. Here're some places to start:
http://www.howstuffworks.com/solar-cell.htm
http://en.wikipedia.org/wiki/Solar_cell

[Javaman]

17. Check out my reply on #16. nt

[OKIsItJustMe]

18. A white panel simply will not work

A white surface looks white because it is reflecting photons across the entire visible spectrum (not heat.)

Black surfaces get warm not because they absorb heat, but because they absorb light, which is converted to heat.

[Javaman]

22. Thanks! :) very cool. nt

[TreasonousBastard]

19. There are no light-colored solar panels yet, but...

even if there were, the amount of the planet covered with solar panels of any color is insignificant and wouldn't make any difference.

[Javaman]

24. yeah, I thought about that...

a very small percentage.

My other hair brained idea is painting all blacktops white. ;) lol

[diane in sf]

26. They are bribing apt owners in LA to go to white roofs when it is time to replace

and planting trees in parking lots. White topped parking lots would be great.

[Ready4Change]

28. Many flat roofs are coated in a silver paint.

The silver paint reduces heat absorbtion, both keeping the roof cooler and increasing the lifespan of the roofing material.

[Ready4Change]

27. No such thing as a dumb question.

If you don't know, then you need to ask. Otherwise you'd stay uninformed, and THAT would be dumb. :)

May I approach your question from a different angle? You are concerned about the sun shining on the panel and making it hot. Consider a solar panel mounted on a houses roof. If you take away that panel, the sun light now strikes the roof below, making it just as, or almost as, hot as the panel would have been. The heat is still transfered, just to a different object.

Looked at this way, you can see there are two choices. You can allow the suns light and heat to hit the roof, warming the house and forcing people to use more electricity for air conditioning.

Or, you can install solar panels a few inches, or feet, off the roof. That not only shades the roof, keeping the house cooler, but also converting some of that light (which would otherwise be totally wasted) into useful electricity.