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

In summary, the discussion in class covered the use of solar panels to collect energy and the energy law stating that no energy can be lost from a system. It was determined that the energy collected would mostly end up as heat, with some sound production and radiation. The conversation also touched on the potential heating of the Earth from power production methods like fission and fusion. It was noted that wind, wave, and water power do not contribute additional heat, but burning fossil fuels does. The conversation also discussed how waste heat from cities can create "heat islands" and increase the angular kinetic energy of the Earth.
  • #1
Baconfish
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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.
 
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  • #2
Baconfish said:
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.
 
  • #3
Baconfish said:
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.
 
  • #4
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?
 
  • #5
Baconfish said:
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.
 
  • #6
Baconfish said:
Yes i just thought about the Earth as a isolated system afther the energy was taken in.
Then no more energy would come in.
Baconfish said:
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.
 
  • #7
Nugatory said:
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?
 
  • #8
Baconfish said:
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.
 
  • #9
A.T. said:
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.
 
  • #10
Baconfish said:
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.
 
  • #11
Ah yes that makes sense. Thanks! :)
 
  • #12
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.
 
  • #13
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!
 
  • #14
A.T. said:
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.
 
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  • #15
rcgldr said:
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?
 
  • #16
rcgldr said:
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
 
  • #17
Baconfish said:
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 [Broken]
 
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  • #18
rcgldr said:
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. said:
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.
 
  • #19
Baconfish said:
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.
 
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  • #20
CWatters said:
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..
 
  • #21
Baconfish said:
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).
 

1. Where does the energy from the sun that is absorbed by the Earth go?

The absorbed solar energy is converted into different forms and is used by various processes on Earth. Some of the energy is reflected back into space, while the rest is absorbed by the land, ocean, and atmosphere.

2. How does the Earth use the absorbed solar energy?

The Earth uses the absorbed solar energy for various purposes, such as powering photosynthesis in plants, heating the Earth's surface and atmosphere, and driving the water cycle. It also plays a crucial role in sustaining life on Earth.

3. Does all of the absorbed solar energy stay on Earth?

No, not all of the absorbed solar energy stays on Earth. Some of it is reflected back into space, and some is radiated back into the atmosphere as heat. This process helps maintain the Earth's energy balance and prevent it from getting too hot or too cold.

4. What happens to the absorbed solar energy when it reaches the Earth's surface?

The absorbed solar energy is converted into heat and is used to warm the Earth's surface and atmosphere. It is also used to power various processes on Earth, such as photosynthesis, evaporation, and wind. Some of the heat is also radiated back into the atmosphere, contributing to the Earth's energy balance.

5. How does the absorbed solar energy affect the Earth's climate?

The absorbed solar energy plays a crucial role in regulating the Earth's climate. It helps maintain the Earth's average temperature and drives weather patterns and the water cycle. Changes in the amount of absorbed solar energy can lead to shifts in the Earth's climate, such as global warming or cooling.

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