The Student Room Group

Is Geothermal Energy a form of indirect solar energy?

see title.
No - that heat was 'put there' when the planet was formed by gravitational accretion (some contribution from nuclear reactions too but not much iirc) it wasn't radiated in from the sun. if you could switch the sun off the heat in the molten core would still be there...

therefore It's different from wind or hydro which are dependent on weather systems which are being continually driven by insolation, or fossil fuel which is fossilised solar radiation from the past.
Original post by Joinedup
No - that heat was 'put there' when the planet was formed by gravitational accretion (some contribution from nuclear reactions too but not much iirc) it wasn't radiated in from the sun. if you could switch the sun off the heat in the molten core would still be there...

therefore It's different from wind or hydro which are dependent on weather systems which are being continually driven by insolation, or fossil fuel which is fossilised solar radiation from the past.


oooh I see, so in theory, even if for some reason we stopped getting sunlight, if we were underground and had enough preserved food and water and access to geothermal power we could survive for a long period of time?
Original post by davidtyoember
oooh I see, so in theory, even if for some reason we stopped getting sunlight, if we were underground and had enough preserved food and water and access to geothermal power we could survive for a long period of time?
Depends on what you mean by a 'long period' of time.

Months or perhaps a few years may well be possible.

But unless science develops a method of cultivating food sources which do not require photosynthesis or at least geothermal/nuclear energy is harnessed to produce light enough for photosynthesis on an industrial farming scale, then living underground beyond that timeframe becomes increasingly unlikely.

Human interstellar and deep space missions lasting years, will also need to solve similar problems.
Original post by uberteknik
Depends on what you mean by a 'long period' of time.

Months or perhaps a few years may well be possible.

But unless science develops a method of cultivating food sources which do not require photosynthesis or at least geothermal/nuclear energy is harnessed to produce light enough for photosynthesis on an industrial farming scale, then living underground beyond that timeframe becomes increasingly unlikely.

Human interstellar and deep space missions lasting years, will also need to solve similar problems.


By Long period of time I mean some tens of thousands of years or so
Original post by uberteknik
Depends on what you mean by a 'long period' of time.

Months or perhaps a few years may well be possible.

But unless science develops a method of cultivating food sources which do not require photosynthesis or at least geothermal/nuclear energy is harnessed to produce light enough for photosynthesis on an industrial farming scale, then living underground beyond that timeframe becomes increasingly unlikely.

Human interstellar and deep space missions lasting years, will also need to solve similar problems.


and yeah I was imagining the underground population making underground farms with lights and an artificially made atmosphere specifically for growing food crops like how some people (:smokin:) grow certain plants (:leaf:) in their houses without using natural sunlight.
Original post by davidtyoember
oooh I see, so in theory, even if for some reason we stopped getting sunlight, if we were underground and had enough preserved food and water and access to geothermal power we could survive for a long period of time?


Yes, but that would firstly require the infrastructure to already be in place and also, you definitely couldn't sustain the current world population. I can't see how you could sustain more than a million or so people, even with a huge amount of preparation. That's barely 0.01% of the population.
Original post by davidtyoember
By Long period of time I mean some tens of thousands of years or so
We are in the realms of pure speculation now. Never say impossible but at the current state of technology, food production methods (food preservation currently only lasts a handful of years), medicines, engineering capability etc. nigh on impossible.

Geothermal on it's own does not have the energy density needed for serious power uses like the large scale generation of electricity for high power applications (factories, cities etc).

Perhaps when science develops fusion power sources and we harness the output for everyday use and put in place plans for migrating underground, then it may be possible sometime in the next few centuries to support a small population as Chlorophile suggests. Your guess is as good as anyone else's though.
(edited 9 years ago)
Original post by uberteknik
We are in the realms of pure speculation now. Never say impossible but at the current state of technology, food production methods (food preservation currently only lasts a handful of years), medicines, engineering capability etc. nigh on impossible.

Geothermal on it's own does not have the energy density needed for serious power uses like the large scale generation of electricity for high power applications (factories, cities etc).

Perhaps when science develops fusion power sources and we harness the output for everyday use, then it may be possible sometime in the next few centuries. Your guess is as good as anyone else's though.


lol yeah the main premise of my question was a question of whether or not there would be enough geothermal energy to support such a civilization, assuming we had all the technology needed to harness it effectively.
Original post by uberteknik
We are in the realms of pure speculation now. Never say impossible but at the current state of technology, food production methods (food preservation currently only lasts a handful of years), medicines, engineering capability etc. nigh on impossible.

Geothermal on it's own does not have the energy density needed for serious power uses like the large scale generation of electricity for high power applications (factories, cities etc).

Perhaps when science develops fusion power sources and we harness the output for everyday use and put in place plans for migrating underground, then it may be possible sometime in the next few centuries to support a small population as Chlorophile suggests. Your guess is as good as anyone else's though.


It definitely does in some areas, Iceland's doing pretty well! Obviously it's got a very small population but still, they're (pretty) civilized.
Original post by Chlorophile
It definitely does in some areas, Iceland's doing pretty well! Obviously it's got a very small population but still, they're (pretty) civilized.


Certain types of industry, but not for things like large scale steel smelting and production, chemical plants etc. Iceland is still heavily reliant on imports for these essentials.
Original post by uberteknik
Certain types of industry, but not for things like large scale steel smelting and production, chemical plants etc. Iceland is still heavily reliant on imports for these essentials.


As far as I'm aware, Iceland produces a lot of excess energy which is used to drive their aluminium extraction industry? And besides, if some kind of apocalypse really did lead to the sun going out, I don't think steel smelting would be our biggest concern!
Original post by Chlorophile
As far as I'm aware, Iceland produces a lot of excess energy which is used to drive their aluminium extraction industry? And besides, if some kind of apocalypse really did lead to the sun going out, I don't think steel smelting would be our biggest concern!
It may well be if the population has to move underground and support it's infrastructure! :tongue:

But I get your drift!

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