If the surface of our planet was covered with solar panels, would they absorb the heat we receive from the sun?
Yes, and no. With no being the answer correct for the most assumptions about your question. Here are a few loosely connected points relating to solar panels and heat.
[ul]
[li]Solar panels mostly don’t produce electricity from infrared radiation, which is what people often mean when they write heat. In physics on the other hand, all of the radiation is heat.[/li][li]It is theoretically possible to take the energy absorbed and store it, which would reduce the heat (energy) everything else on Earth receives, and reduce temperatures.[/li][li]It’s even possible to remove that energy from the Earth system all-together, but if you use any of it down here, the energy is going to end up as heat warming the Earth.[/li][/ul]
It also depends on the degree of reflectivity of your solar panel array. If they were all black they would decrease the albedo of the planet, and actually increase the amount of heat/energy the planet receives (well, receives and doesn’t bounce back to space)
The “heat” that the earth receives from the sun remains the same whatever we do with it.
All energy eventually ends up as heat somehow or other. The only difference is whether it does anything useful in the process of becoming heat (and of course what “useful” means could be debated endlessly).
If you mean would the earth cool as a result, no.
If solar cells were 100% efficient, converting all received radiant energy to electricity, then as Chronos says since all energy ends up as heat eventually, the same amount of heat would be produced. But the difference is that none of it would be reflected back into space as happens with real-world surfaces (a 100% efficient solar cell would look totally black) so we’d be warming even faster.
In real life, solar cells are relatively inefficient, so they act as low-albedo surfaces that get warm and theoretically warm the local microclimate, and they produce electricity that ends up as heat.
This is not to say that solar cells are bad. All of these theoretical factors are outweighed by the fact that they produce clean energy that mitigates the use of fossil fuels, which is where the really harmful warming comes from. In fact, solar panels installed on rooftops tend to have direct beneficial effects for the buildings they’re installed on, aside from the electricity they produce. By shading and insulating the roof from direct sunlight (to different degrees depending on whether they’re tilted or flush mount) studies have shown that they tend to result in cooler ceilings and lower air conditioning costs in summer, while having no discernible effects on heating costs in winter.
Yes, but the albedo of the surfaces that receive it has a lot to do with how much gets reflected back into space and hence the amount of local warming. Thus, accelerated Arctic warming due to reduced ice cover and more darker water and land being exposed, or urban heat islands in part due to dark colored roofs and pavements.
Solar panels in theory change the albedo of whatever surface they’re on top of, but that’s rarely a practical concern, though there is some concern about the land use and potential microclimate effects of very large solar farms but, again, it depends what they’re covering up.
If you’re asking whether installing solar panels will increase the amount of heat absorbed, it depends on what was there before. Solar panels convert about 15% of the received energy into electricity, and probably reflect about 10%. So it converts about 75% of received sunlight into heat.
Which means, in terms of the fraction of sunlight energy converted into heat, it’s the same as a surface with 25% albedo (i.e. reflects 25% of the sunlight, and absorb the rest). This diagram shows albedo values for various surfaces. If you put solar panels on top of a surface with <25% albedo (e.g. the ocean), you end up with LESS heat than before. If you put it on a high-albedo surface (e.g. desert, ice, snow), you end up with more heat than before.
Of course the 15% that gets converted into electricity will eventually turn into heat somewhere. (Unless you power a searchlight aimed at the night sky.) But we can ignore it if we assume it’s replacing power generated by some other means.
I think they somewhat increase the heat Earth receives from the Sun because they are darker than most of the land they cover, so they decrease what is reflected back into space as light. I’m pretty sure this has to be the biggest effect.
If installed on land, yes, as already noted the reduced albedo would likely induce a small amount of local heating. If installed on rooftops, as also previously noted, there will typically not be a reduced albedo (roofs are usually already dark) and there is a net cooling benefit to the building.
But you also need to factor into the equation the emissions reduction that accrue to the solar panels. It’s been calculated that even when panels are placed in a high-albedo area like desert, where the light-to-dark transformation creates the worst-case net increase in radiative heating, over a 20 year lifespan the panels will avoid 25 times more GHG warming than they will cause. In most other areas the net gain would be much better than 25:1. Furthermore, the GHG effects would persist for centuries, while the panels generate heat only while they’re in place.
When we are not using solar panels we are burning fossil fuel which was created from energy that the earth received millions of years ago and stored in the ground. If we use today’s sunlight and stop burning these fuels, the earth cools, right?
Yes, technically, but the amount of heat released by the burning of fossil fuels is pretty insignificant compared to the amount of received received from the sun, and the amount that is reflected/radiated back out into space.
And if this is asked thinking of global warming, the heat released by burning is also insignificant compared to the amount of extra heat trapped by the carbon dioxide released.
Wait a minute. Not all electrical energy is converted to heat. A lot of electricity goes into producing other light, much of which escapes directly into space. And what about sound? Would that end up as heat, or escape the earth too?
Since sound consists of vibrations through the air, water, and other media, those vibrations would generate heat through friction alone I’m thinking.
How much is producing light though? And how much of that light escapes to space?
Sound will not escape the Earth.
I don’t know, but there’s this. In any case, it’s a certain amount.
Yes, the surface of the earth affects the earth’s albedo which in turn has a big effect on climate.
Will solar panels affect the Earth’s albedo more than a completely miniscule amount? No.
That said the most efficient form of solar power is simply doing what you describe. Allowing water to be heated by light, using it instead of water that’s been heated by fossil fuels. It is (or at least was the last time I looked into it) far more efficient, and cost effective, than any system that relied on generating electricity from sun light.