If all of mankind’s energy was supplied through solar panels would the effect be big enough to decrease the temperature (since light is converted in part to electricity)?
No. If a watt worth of sunlight hits the earth, it’s transformed into a watt of heat. If it hits a solar panel, it’s transformed into some heat and some electricity, which is then used to power something that then transformed it into heat. The only solar energy that doesn’t heat up the planet is the one that is reflected back into space, which, however, isn’t much for solar panels.
However, if you use a watt of sunlight to power your phone instead of a watt of energy you got from burning coal, this watt of energy instead stays below earth and therefore doesn’t heat up the planet. It also doesn’t release co2, which would otherwise reduce the atmosphere’s reflectivity, trapping even more sun heat on the planet.
So solar panels don’t reduce the temperature by not allowing sunlight to heat up the planet, they decrease the temperature by replacing other stuff that would otherwise heat up the planet.
Just note that the released energy of burning fossils (or nuclear) is orders of magnitude below what the sun does. It really is only the CO2 from coal (or CO2 and CH4 from natural gas, …) that does the heating, since it acts like insulation.
co2, which would otherwise reduce the atmosphere’s reflectivity
Just to be pedantic CO2 absorbs bands in the infrared and reemits it, energy that otherwise could be lost to space. This is part of the reason you can’t do infrared telescopes from earth.
https://news.climate.columbia.edu/2021/02/25/carbon-dioxide-cause-global-warming/
Water is an even more powerful greenhouse gas but fortunately the earth is cool enough for it to condense back out of the atmosphere. If temps got high enough that more evaporated than condensed then you’d get a runaway greenhouse effect and we’d be truly fucked.
Plants fixing carbon also converts energy to a form that isn’t heat, so I think we should count that along with reflection as a way that solar energy doesn’t become terrestrial heat.
Correct, but not only is it extremely little, this stored energy is also quickly released again after the organism dies.
quickly
Quick in geologic time. But this is what fossil fuels are, so it’s an order of magnitude or two different than the time in which generated electricity will be used.
And you’re right, it’s very small. Everything we know is pretty small, even combined. The amount of energy the sun imparts to the Earth every day equals what humanity would use over about 12 years at current levels.
when that electricity (photons absorbed by solar cells dumped into the grid) they’ll almost certainly be used in an application that generates heat, as well - data centers, phones, refrigerators, cars, they all generate heat as a byproduct of using that power.
I don’t think this is in any way a problem.
Yeah I think you’re somewhat repeating what was said above. No one said it was a problem, but the point was that solar panels don’t cool the earth because even if they do convert some sunlight into electricity instead of heat, it will soon become heat anyway when the electricity gets used.
Solar panels aren’t 100% efficient though, so isn’t a bunch of it is reflected back in to space?
No, they are covered in anti-reflective coatings to minimize reflection. Most of the excess is converted to heat (as would happen if the light just hit the ground).
Which is why if the objective was just to cool down the Earth (and ignoring that solar panels replace other sources of electricity that warm up the Earth more) just painting the ground white would be more reflective than solar panels as the white paint increases the amount of sunlight that gets reflected back to space whilst solar panels not only capture some of it as electricity (that will ultimately end up transformed into heat somewhere) but they also absorb some transforming it directly into heat (i.e. they warm up a bit).
it’s transformed into some heat and some electricity, which is then used to power something that then transformed it into heat. The only solar energy that doesn’t heat up the planet is the one that is reflected back into space
if you use a watt of sunlight to power your phone instead of a watt of energy you got from burning coal, this watt of energy instead stays below earth and therefore doesn’t heat up the planet.
What?
Fossil fuels are carbon.
That carbon was sequestered from the atmosphere millions of years ago.
Burning fossil fuels releases that carbon into the atmosphere, which then makes the earth hotter
Think of oil as dead dinosaurs and coal as dead trees, that’s basically what it is.
All that stuff was taken out of circulation over an insanely long timeline, and now on a very short timeline we’re digging it up and putting it back into circulation. So fast that species can’t adapt to the change and die out before they can evolve.
Not directly. That electricity is converted to heat when it’s used: All devices are space heaters, some just do other things as well. Even if not used, it would still be converted to heat by the panels. There’s no getting around the conservation of energy.
In theory, we could send that power out into space as microwaves or light, but in practice the effect would be negligible. The direct heat output of every human activity is nothing compared to the sun: All the electricity generated on earth is around 3 Terrawatts, while the sun hits us with 200 Pettawatts, 66 thousand times more.
On the other hand, burning fuels releases gasses like CO2, which can traps sunlight and creates thousands of times more heat than the actual amount of power generated. If we stopped burning fuel, it would stop the current massive increase in global temperature, which would then slowly be reversed by things like the carbonate-silicate cycle.
The worst part is that convincing people to use less is difficult even when it’s something easy. Let’s say for example that your dryer brakes and you need to replace it and up until this point you’ve been using either a standard resistive electric dryer or a gas dryer. Heat pump dryers are now readily available, of good quality, and use literally 1/4 the power of a resistive electric to do the same job.
If we could convince everyone to just only buy heat pump dryers from this point forward that alone would create a ridiculous drop in energy usage for drying clothes as it’s a very energy intensive task. But people don’t like things that are different and so convincing them to try it is very hard. I had to basically purchase one for my grandparents to get them to be willing to try it and now they love it but initially they were very strongly against trying
There’s also a bunch of dumb but sometimes arguments. Take LED stop lights for example one of the biggest arguments against them is in places where it tends to snow every year they say oh well they aren’t worth it here because when it snows they get covered and if you put a heating wire on them to melt the snow then you’re not saving any power over the standard ones. But it’s like hello rub a couple brain cells together unless you are somewhere where it snows 365 days of the year you’re still saving the power whenever it’s not snowing which is a pretty drastic amount of power across an entire city or state.
I could sit here and give examples all day but suffice to say convincing people to use less even when It ultimately results in a better end result for them is exacerbatingly difficult
Also large numbers of solar panels like that have other effects, changes in wind patterns and such.
Changes for the better in deserts: https://farmingdale-observer.com/2025/01/05/china-confirms-desert-solar-panels-permanently-alter-ecosystems-environmental-impact-revealed/
I mean I noticed just in small effects the parking lots that have them installed over the parking spaces seem less urban hellscapey to me, by like 5 to 10 degrees hamburger
We already have buildings all over the place. I like the idea of installing them there. Parking lots would be awesome too since it’s otherwise wasted space, but this way cars and people are protected from the sun and rain. Win/win.
Directly, as you phrased the question: No.
Indirectly: Yes. Because we would automatically stop burning fuels when we get all our energy from solar. That would decrease the temerature a tiny little bit.
But the temerature of the planet does not really depend on such actions. For example, the indirect effects of CO2 and Ozone in the atmosphere have much more powerful impacts - and still they can only change the temperature at the planet’s surface (that’s what our lives depend on). The whole of the planet is yet another thing.
Don’t forget industrial heat. If we had infinite electricity for free everywhere there would still be fossil fuels burned for industrial heat. We need more technology to finish it like plasma torches.
No need to despair, the technology is being actively developed and a lot of the sub 600 Celsius temps have an electric solution now.
I was rather surprised to find out there was something like a smelter running on electricity (well industrial scale one). It will be a big deal if solar panels and wind turbines can be made exclusively with electricity from mining to final product.
Don’t forget industrial heat
Why? Is it different from “all of mankind’s energy”?
Industrial electric arc furnace temperatures can reach 1,800 °C (3,300 °F)
Technically, if you built enough solar panels in space, they would completely block the sun and massively decrease global temperature
Yeah, on the earth surface 23% of the light gets absorbed by the atmosphere before it even hits the panel, and 85% of the remained doesn’t get absorbed by the panel at all.
Most of the sunlight doesnt even hit Earth
Could you imagine how much more energy we could produce if we used all the empty space in space?
Conservation of energy equation says otherwise.
The assumption here is that solar panels make sure that the energy from the sun gets turned into electricity instead of heat. However, pretty much everything that uses electricity is technically a 100% efficient electrical space heater (eg. A fan turns electricity into heat and kinetic energy… which dissipates into heat). So the only way that solar panels could have a cooling effect is if we didn’t use the electricity (someone smarter than me will probably be able to point out exceptions to this, but still this should be the case for the majority of uses).
Also, since solar panels are intended to capture as much solar energy as possible (hence why they are typically black), the realistic effect of covering the planet with them would probably be a temperature increase
The sum of consumed energy will stay the same, so will be the heat generated by consumption. The only way to efectively decrease temperature is to reduce consumption. http://www.zo.utexas.edu/courses/THOC/Global-Warming.htm
