Absorbed energy from the sun, where does it end up?

[Baconfish]

Ok, we had a discussion in class: If we build solar panels all over the Earth's surface we can collect a good amount of energy. If we use this energy to power el-cars where does the energy end up? The energy law states that no energy can be lost from a system.

 

[Vagn]

Ok, we had a discussion in class: If we build solar panels all over the Earth's surface we can collect a good amount of energy. If we use this energy to power el-cars where does the energy end up? The energy law states that no energy can be lost from a system.

Heat, the answer is almost always heat. There's some sound production as well from the motor, but it'll be heat lost in the wiring, heat transferred to the air and any moving part etc. Some will also be radiated away, but most of this will be in the IR part of the spectrum.

 

[A.T.]

The energy law states that no energy can be lost from a system.

From an isolated system. If the Earth was isolated, the Sun's Energy wouldn't get here in the first place, would it? Some energy leaves the Earth on the same way as it got here, as radiation.

 

[Baconfish]

Yes i just thought about the Earth as a isolated system afther the energy was taken in. Ok so basically we would heat up the Earth since the IR radiation would come back down again. So if kinetic energy usually ends up like heat this means that power production like fission and fusion (in the future :) ) will heat up the planet?

 

[Nugatory]

So if kinetic energy usually ends up like heat this means that power production like fission and fusion (in the future :) ) will heat up the planet?

Yes, although it is a good exercise and somewhat fun to calculate by how much. Try it!

Google will give you some decent values for annual energy production and the mass of the earth, and you can make some reasonable order of magnitude estimate for the specific heat of the earth.

 

[A.T.]

Yes i just thought about the Earth as a isolated system afther the energy was taken in.

Then no more energy would come in.

Ok so basically we would heat up the Earth since the IR radiation would come back down again.

Why would it come back? Some of it escapes into space.

 

[Baconfish]

Yes, although it is a good exercise and somewhat fun to calculate by how much. Try it!

Google will give you some decent values for annual energy production and the mass of the earth, and you can make some reasonable order of magnitude estimate for the specific heat of the earth.

But i should count out wind, wave, water and all kinds of renewable energies right? Since they are in a natural cycle. Or maybe not, as the water in a reservoar for example would naturally not end up as heat, but rather move around some rocks on the natural path down the mountain?

 

[A.T.]

the water in a reservoar for example would naturally not end up as heat, but rather move around some rocks on the natural path down the mountain?

If it moves rocks down, then even more potential energy is released and converted to heat.

 

[Baconfish]

If it moves rocks down, then even more potential energy is released and converted to heat.

Oh ye! So the i probably should count them out if I am interested in a net heating of the earth. I should only count fission and solar.

 

[Nugatory]

But i should count out wind, wave, water and all kinds of renewable energies right? Since they are in a natural cycle. Or maybe not, as the water in a reservoar for example would naturally not end up as heat, but rather move around some rocks on the natural path down the mountain?

Wind, wave, and water are all directly or indirectly powered by incoming solar radiation so power from these sources contributes no heat that wasn't coming in anyways.

Burning fossil fuels does contribute additional heat.

 

[Baconfish]

Ah yes that makes sense. Thanks! :)

 

[CWatters]

So if kinetic energy usually ends up like heat this means that power production like fission and fusion (in the future :) ) will heat up the planet?

Correct. Perhaps see..

http://www.cgd.ucar.edu/tss/ahf/

They suggest that in 2005 this effect accounts for about 1% of global warming.

 

[Baconfish]

This maybe explaines one other thing: Many times i´v wondered why often in cities its wet while its laying snow just outside it eaven though the topography is the same, so its probably just waste heat!

 

[rcgldr]

If it moves rocks down, then even more potential energy is released and converted to heat.

Angular momentum is conserved. If rocks move down (inwards), then the angular velocity of Earth and rocks increases by a tiny amount, and the angular kinetic energy of Earth and the rocks increases.

 

[A.T.]

Angular momentum is conserved. If rocks move down (inwards), then the angular velocity of Earth and rocks increases by a tiny amount, and the angular kinetic energy of Earth and the rocks increases.

That doesn't contradict what I wrote, does it?

 

[Baconfish]

Angular momentum is conserved. If rocks move down (inwards), then the angular velocity of Earth and rocks increases by a tiny amount, and the angular kinetic energy of Earth and the rocks increases.

Hehe that's really cool to think about :) so easy to change the world :p

 

[DaveC426913]

This maybe explaines one other thing: Many times i´v wondered why often in cities its wet while its laying snow just outside it eaven though the topography is the same, so its probably just waste heat!

Yes. They are commonly called 'heat islands'.

I live in one, and enjoy that fact immensely.
http://images.slideplayer.us/4/1425045/slides/slide_7.jpg

 

[rcgldr]

Angular momentum is conserved. If rocks move down (inwards), then the angular velocity of Earth and rocks increases by a tiny amount, and the angular kinetic energy of Earth and the rocks increases.

That doesn't contradict what I wrote, does it?

I'm wondering how much of the decrease in GPE goes into the increase in angular kinetic energy versus heat.

 

[CWatters]

This maybe explaines one other thing: Many times i´v wondered why often in cities its wet while its laying snow just outside it eaven though the topography is the same, so its probably just waste heat!

According to wikipedia...

The main cause of the urban heat island effect is from the modification of land surfaces, which use materials that effectively store short-wave radiation.[2][3] Waste heat generated by energy usage is a secondary contributor.

 

[Baconfish]

According to wikipedia...

The main cause of the urban heat island effect is from the modification of land surfaces, which use materials that effectively store short-wave radiation.[2][3] Waste heat generated by energy usage is a secondary contributor.

Aha so basically removal of trees and lots of black asphalt..

 

[DaveC426913]

Aha so basically removal of trees and lots of black asphalt..

Actually, if you look a the heat map I posted, it seems that concrete (buildings) is hotter than asphalt (roads).