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)?
this post was submitted on 08 Jan 2025
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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.
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).
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.
Your comment in pictures:
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).
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.
Yeah, that explanation sounded off to me. CO2 and other greenhouse gases are the issue, not heat directly released from combustion. The sun is doing the overwhelming majority of heating. Carbon staying underground matters far more than watts staying underground.
Isnt the energy also stored in batteries until ready to be used?
Yeah, so what? Eventually, it'll be heat.
Isnt that a more controlled snd efficient way to use the energy though
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.
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.
Correct, but not only is it extremely little, this stored energy is also quickly released again after the organism dies.
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.
No, quickly as in years. There is no more coal or oil formed today, there are now organisms that can digest every part of organic stuff. There were none back then for example for lignin from wood, which is where we got coal from.
What?