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Author Topic: The earth as a source of energy ?  (Read 24931 times)

Offline neilep

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The earth as a source of energy ?
« on: 04/05/2006 17:32:26 »
Hello all,

What a wonderful day !!..

I know our ability to drill deep into the Earth is very very limited...but do you think as our progress continues to dig deeper, that the heat of the planet could be a source of energy ?

whajafink ?

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Offline Hadrian

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Re: The earth as a source of energy ?
« Reply #1 on: 04/05/2006 17:57:56 »

In a limited way we already get energy from thermal transfer that could be said
to be energy from beneath the earth. Deep drilling is still a long way off from being able to overcome the many problems that such a venture you are suggesting would have. In theory of course it could work. After all energy is energy. As long as you can tap into it is available.  
   




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another_someone

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Re: The earth as a source of energy ?
« Reply #2 on: 04/05/2006 18:37:13 »
I do remember asking, I think it was somewhere on TNS, but I cannot find it at present, about using geothermal energy from potential volcanoes and super-volcanoes in order to cool them down (while providing us energy), thus delaying their inevitable eruption.

I had hear that one reason is that tapping into all the geysers would lose tourist dollars.

Nonetheless, the underlying fact remains that if you use underground heat to provide energy, it is a finite resource, and will cool the ground below.  I'm not saying it will have much of an impact on the ultimate source of this heat, the core of the Earth; but it could have an impact on the magma immediately beneath the crust, as we may be extracting heat faster than the convection currents from the core can deliver more heat to the surface.

What the consequence of this underground cooling might be is open to anyone's imagination.  It could cause a slight collapse of the local terrain; at worst, it could cause a thickening of the crust.

I am not saying “don't do it”, I'm just saying there is no such thing as a free lunch.



George
 

Offline neilep

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Re: The earth as a source of energy ?
« Reply #3 on: 04/05/2006 19:29:31 »
quote:
Originally posted by another_someone

I do remember asking, I think it was somewhere on TNS, but I cannot find it at present, about using geothermal energy from potential volcanoes and super-volcanoes in order to cool them down (while providing us energy), thus delaying their inevitable eruption.



George




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Offline ukmicky

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Re: The earth as a source of energy ?
« Reply #4 on: 04/05/2006 22:02:59 »
NEIL

You dont need to go deep .

Provided youve got an average sized back garden and your home is insulated properly  then there is enough heat trapped six to eight feet down in the soil to heat your home and hot water all year round. Well provided you dont waste it that is.

The soil down there may not feel hot or warm to touch but theirs enough trapped thermal energy from the sun to heat an average sized home.

Lots of new homes are now using the system and You can even buy a do it yourself kit for your back garden if its big enough containing and a few hundreds of metres of piping that you bury in deep trenches running the lenght of the garden and a heat exchanger.

And the only day to day cost for obtaining this free energy is the electricity to run the water pump, or if you wish you can power it from solar energy or a small wind turbine.

Michael
« Last Edit: 04/05/2006 22:03:44 by ukmicky »
 

Offline neilep

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Re: The earth as a source of energy ?
« Reply #5 on: 04/05/2006 22:33:47 »
Are you serious Michael ?

That's amazing....thank you very much !

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another_someone

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Re: The earth as a source of energy ?
« Reply #6 on: 04/05/2006 23:12:10 »
I can imagine two problems with extracting heat created by solar heating of the soil.

In the long run, you cannot extract more solar heat from the soil than the sun can replenish.  Although it is true that the soil will allow a more stable heat supply, with less of a day to day, hour by hour, variation than is the case of directly trapping the heat at the surface; but the actual amount of energy cannot be any greater than that which is at the surface itself.

Secondly, if you do extract heat from a couple of metres down, that will inevitably cool the soil itself.  How is this going to effect worms, seeds and bulbs, etc; particularly in the winter months?



George
 

Offline JimBob

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Re: The earth as a source of energy ?
« Reply #7 on: 07/05/2006 02:50:20 »
If I had had enough money I would have invested in this 2 years ago

http://www.powertubeinc.com/

It was a local company. Heat exchange is by a patented fluid heated down-hole.




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Offline Laith

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Re: The earth as a source of energy ?
« Reply #8 on: 07/05/2006 03:03:43 »
If we dig deep enough to reach the lava would the pressure push the molten lava up like a volcano?

Laith
 

another_someone

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Re: The earth as a source of energy ?
« Reply #9 on: 07/05/2006 03:13:17 »
quote:
Originally posted by Laith
If we dig deep enough to reach the lava would the pressure push the molten lava up like a volcano?



It might be difficult to design drilling equipment that could tolerate those temperatures (although not theoretically impossible).

I don't know the answer (not sure anyone does), but I would think you would almost certainly have a lava flow to the surface, but not an explosive eruption (but then, not all volcanoes are explosive, some just quietly spill out hot lava).

How much lava came to the surface would ofcourse depend on the diameter of the hole, and probably the nature of the convection currents in the magma in that region of the magma that we have drilled down to.



George
 

Offline Laith

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Re: The earth as a source of energy ?
« Reply #10 on: 07/05/2006 03:32:40 »
what matter could be used for the drilling machine (i.e. what doesnt melt or burn from lava)?

Laith
 

Offline neilep

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Re: The earth as a source of energy ?
« Reply #11 on: 07/05/2006 04:01:03 »
quote:
Originally posted by Laith

what matter could be used for the drilling machine (i.e. what doesnt melt or burn from lava)?

Laith



What about Diamond ? It's melting point is 3820 degrees Kelvin ? Though I realise there is no way enough diamond available.

How hot's your average Magma ?

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another_someone

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Re: The earth as a source of energy ?
« Reply #12 on: 07/05/2006 11:27:41 »
Not sure that even diamond would cope.  On the other hand, it is increasingly possible to fabricate diamond (at present, not good enough for jewellery, but still quite adequately for industrial diamond – there is always debate whether the fabrication process could be enhanced faster if there was not almost a monopolistic control over the diamond market).

On the other hand, you cannot easily make the drill shafts, etc. out of diamond (maybe out of carbon nanotubes, but they, at present, are more expensive than diamond, and would still need to be embedded is some sort of matrix).

I was thinking either of some very aggressive cooling, or using non-contact drilling (e.g. lasers, or acoustic drilling).



George
 

Offline neilep

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Re: The earth as a source of energy ?
« Reply #13 on: 07/05/2006 14:21:22 »
With non contact drilling the shaft will need be reinforced somehow unless the nature of the drilling will create a clean & secure surface, effectively creating a solid pipe from the very material you're drilling through.

What about diamond coating ?

I can see how a non contact drilling would be preferable....very little in the way of wear and tear compared to conventional drilling and far more pliable in use than physically drilling hundreds of miles which in no doubt would pose many issues and problems where the drill would have to be retracted.

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another_someone

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Re: The earth as a source of energy ?
« Reply #14 on: 07/05/2006 19:00:41 »
quote:
Originally posted by neilep
With non contact drilling the shaft will need be reinforced somehow unless the nature of the drilling will create a clean & secure surface, effectively creating a solid pipe from the very material you're drilling through.

What about diamond coating ?

I can see how a non contact drilling would be preferable....very little in the way of wear and tear compared to conventional drilling and far more pliable in use than physically drilling hundreds of miles which in no doubt would pose many issues and problems where the drill would have to be retracted.



Two problems I can see with diamond – it is very inflexible, and it is a good conductor of heat.  Even if it were not such a good conductor of heat, the heat would get through eventually, so you would still need some sort of cooling mechanism.

If the cooling was aggressive enough, you could at least ensure that a layer of solid rock remained coating the inside of bore hole, and it would then simply be a matter of preventing the drilling mechanisms from making contact with the still hot, but now solid, wall.

Maybe pump coolant down a channel, and into the space between the drill mechanism and the bore hole wall, and then use acoustics or magnetic fields to push the coolant away from the drill mechanism, thus simultaneously ensuring that hot coolant it kept away from the drill mechanism, and that the drill mechanism stays away from the bore hold walls.

For short durations, plain old ablative coating on the drill mechanism would suffice, but it would not last long, which is why pumping liquid coolant down makes more sense.

Another option would be to have two or three large wheels, or cylinders, around the drill mechanism.  The wheels will be constantly rolling around the perimeter of the bore hole.  They would both smooth out, and compact the side of the bore hole, as well as ensuring the the drill mechanism itself is kept away from the sides of the bore hole.  Because they are large diameter wheels, only a very small proportion of the rim is in contact with the wall at any one time, and since it is constantly rolling, that small part is never in contact for very long, and so will not absorb a great deal of heat.  It will still be necessary to aggressively cool the wheels, but they need to actually have any part that will get that hot, so long as the heat can effectively be dissipated from those parts of the wheel that are not in contact with the wall, so they are cool enough once they come back in contact with the wall.



George
« Last Edit: 08/05/2006 01:40:04 by another_someone »
 

Offline Bass

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Re: The earth as a source of energy ?
« Reply #15 on: 08/05/2006 17:42:21 »
JimBob and Ophiolite, with their experience in the oil patch, could better answer your questions about deep drilling techniques.  Us hard-rockers don't do it as large or as deep.
I've had good luck up to 2000 feet (650 meters for you folks that talk funny) using impregnated bits- bits using various alloys (depending on how hard a metal you need) impregnated with diamond chips.  Not only do you need a coolant, your drilling fluids also need to be high-density to counteract the pressures found at depth.  There's a whole industry built around the manufacture of various "drill muds".
As to lava flowing back up the drill tube- not likely to happen.  Very few magmas are truly "liquid", most are highly viscous combinations of rock, crystals and melts.  This is especially true in contintental land masses, where magma is likely to be more siliceous (which makes them more viscous).

Subduction causes orogeny.
 

Offline neilep

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Re: The earth as a source of energy ?
« Reply #16 on: 08/05/2006 17:56:14 »
Hi Skip..Thanks.

You're so right about the science of 'drill muds'. I never realised how an exact science it is. Fascinating.

In what capacity were you drilling down 2000 feet ?..sounds like ' fun '.

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Offline Bass

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Re: The earth as a source of energy ?
« Reply #17 on: 08/05/2006 18:31:21 »
Neil
Back in the early 80's (the good old days, Reagan, the evil empire, etc.) molybdenum was the next holy grail in mining.  I worked on several deep "moly" systems that required extensive drilling.  Don't know if 'fun' is quite the appropriate word, but it was interesting.
I am now revisiting several of these moly systems, not so much for their moly potential (even though the price hit new highs recently), but for precious metals zoned around the moly.

Subduction causes orogeny.
« Last Edit: 08/05/2006 18:32:39 by Bass »
 

another_someone

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Re: The earth as a source of energy ?
« Reply #18 on: 08/05/2006 19:18:17 »
From what I see, the Earth's crust is between 10Km down to 35Km (and even 70Km under the Himalayas) thick.  A bore hole of 650 meters, while impressive if itself, is still only scratching the surface.



George
 

Offline JimBob

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Re: The earth as a source of energy ?
« Reply #19 on: 09/05/2006 04:00:21 »
I must agree with Bass. Not likely due to the high pressures which increase viscosity so much. The technique of laser drilling, although promising for depths up to the curent record depth, is not going to change much. This is because of the problem George pointed out with the "drill string" It just isn't much better than high temp steel.



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Offline Bass

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Re: The earth as a source of energy ?
« Reply #20 on: 09/05/2006 05:32:59 »
Neil
Just for fun, I once visited the 9000 foot level of an operating mine.  I pity the miners that work at that depth- bad air, excessive heat, rock bursts, scalding water- but I had fun.  The ride down the hoist- basically free-fall in an open cage for 7000 feet, then 2000 feet to slow down and stop, was definitely one of the highlights.  They should probably advertise and charge folks for that ride!
Like I said, just for fun.

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another_someone

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Re: The earth as a source of energy ?
« Reply #21 on: 09/05/2006 11:31:50 »
quote:
Originally posted by JimBob
I must agree with Bass. Not likely due to the high pressures which increase viscosity so much.


But if you punch a hole down to that depth, unless you maintain substantial pressure within the hole, is it not going to have the consequence of a pressure release?



George
 

Offline JimBob

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Re: The earth as a source of energy ?
« Reply #22 on: 09/05/2006 21:15:40 »
We already have these holes to the mantle. They are called mid-ocean ridges and there is no massive pressure release there.



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another_someone

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Re: The earth as a source of energy ?
« Reply #23 on: 09/05/2006 22:23:04 »
quote:
Originally posted by JimBob
We already have these holes to the mantle. They are called mid-ocean ridges and there is no massive pressure release there.



Not comparable.  I am not saying they are irrelevant, only that it is not the same situation.

Mid oceanic ridges push the match up a 10 Km gap, before reaching cold air – that is 10Km of rock pushing back down against the flow of lava.

This is why I allowed the possibility that a bore hole down to the mantle might need positive pressure to hold back the lava.  Otherwise, rather that the lava having to push back against 10Km of basalt, it merely has to push back against 10Km of air.  A significant difference.

Beyond that, we really don't know at first hand what happens 10Km beneath the mid oceanic ridges; we see them only as they arrive at water level.  By comparison, if we drill down to meet the mantle, we would have to be concerned very much about what happens to the drill mechanism at 10Km (or 35 Km, depending on where the bore hole happens to be) beneath the surface, where the crust meets the mantle.

I never suggested that the mantle would gush to the surface, but the fact that the mantle is capable of providing enough pressure to push basalt 10Km up through the crust at mid oceanic ridges clearly indicates that the pressure available there must be comparable to the weight of 10Km of basalt rock.



George
 

Offline Bass

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Re: The earth as a source of energy ?
« Reply #24 on: 10/05/2006 01:03:56 »
George
Keep in mind that the basalt that erupts at the mid-oceanic ridge is not the same material that you would hit if you drilled down 10 km to the top of the mantle.  The basalt has differentiated- probably several times- before reaching the surface.  Seismic evidence suggests that even the upper mantle behaves like a high-viscosity plastic material (I always imagined a crystal mush).  
Pulling tectonic plates apart at the mid-oceanic plates creates lower pressure zones that allow the more liquid part (basalt) of the magma to ascend, leaving behind the more crystalline portion (peridotite).
Also, the mantle material would be pushing back against a 10km hydrostatic head, not merely air pressure.  The small diameter of any borehole would not release enough pressure to cause an eruption of mantle material.

Subduction causes orogeny.
 

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Re: The earth as a source of energy ?
« Reply #24 on: 10/05/2006 01:03:56 »

 

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