[ExI] Heat of the Earth [WAS Re: Efficiency of wind power]

[Kelly Anderson]

2011/4/19 Mr Jones <mrjones2020 at gmail.com>:
>> Kelly Anderson:> It would be very good if we could figure out how to steal
>> heat from
>> > the hot spot under Yellowstone to the point of putting off the next
>> > eruption of the super volcano... Probably a more potent risk than
>> > asteroids, but fixing the problem seems significantly more difficult.
>
> **nods** I've thought of this very same thing.  If we could somehow draw
> away some of that heat safely, we could prevent the super-volcano from
> sending us into the history books.

Not that there would be any history books. :-)

> The problem is, we like to take the
> easy/cheap way, instead of the long-term responsible way...so we'd pollute
> the area, and destroy the balance; because it was cheaper.

If we could do it at all, that might still be a long term good
trade-off. Geothermal itself is relatively clean, though what you do
with it might not be. If you could steal enough energy to make a
difference, it would be a huge power source. The environmental damage
of a super volcanic eruption (which could lead to a 90% reduction in
the overall population of people world wide) seems more than any
industrial complex I can imagine.

Parenthetically... why do we even have a hot spot under Yellowstone?
It has been there for a very long time. I have heard a hypothesis for
the hot spot under Hawaii... but that theory doesn't fit for
Yellowstone. The Hawaiian hypothesis noted that the hot spot now under
the new underwater island near the big island is at the same place on
our planet as the great spot on Jupiter. Perhaps the same fluid
dynamics that cause the great spot are at work in the magma under the
earth's surface? It's an interesting theory, but I don't know if
serious scientists give it the time of day. It could just be a strange
coincidence, with the Yellowstone hot spot being contrary evidence...
I haven't heard if there is a similar hot spot under Tambora
(http://www.youtube.com/watch?v=bqpOTJAAwBU), or the Kamchatka
peninsula (which has similar geothermal properties to Yellowstone). I
actually got very side tracked here, as there is apparently a newly
discovered (2006) supervolcano in Kamchatka, but it isn't widely
known. More on this later.

>> Eugen: Geothermal is a niche. It can be an important niche for some
>> locations, but in the great total it doesn't matter that much.
>
> What about ground loops, versus wells.  5-8' deep loops, 100's or 1000's of
> meters in length, acting as the 'heatsink'.  I'm thinking of geo in terms of
> a supplementation to home heating/cooling solutions.  Granted, some areas
> don't have open space to trench in this manner, but I've heard that
> lakes/ponds are also good sources.

Lakes and ponds have convection currents that allow them to dissipate
heat in just the way that in ground systems take advantage of. So I
would assume that water based systems wouldn't work quite as well as
underground systems since they generally change temperature more with
the seasons.

I did a lot of caving in my youth, and was always impressed that while
it was ten degrees outside, it was always comfortable in the cave.

I have always had my doubts about these in ground systems, in that the
sizing of the system to prevent the slow cooling of the ground in the
winter would have to be very large, making them expensive. Basically,
it is a heat pump that takes advantage of the constant 55 degree
temperature of the underground below a certain depth. The heat pump
has to work much less to extract heat from 55 degrees than from 10
degrees.

>> You can also deplete the local reservoir very easily and/or
>> cause earthquakes and ground sinking if you don't know where
>> you're doing. E.g. my place is tapping the Malm karst
>> geothermal aquifer, which is somewhat anomalously high
>> http://www.liag-hannover.de/fileadmin/produkte/20070713113243.pdf
>> and uses to adjacent well to reinject the Kalina cycle-depleted water,
>> causing a cooler plume dowstream so you must take care with
>> well spacing and alignment.
>
> Yeah, see I'm thinking more along the lines of using the top layer of ground
> to act as a heat-sink for our homes...not so much tapping into giant
> geo-thermal geysers n' such.
> In winter I'd only need to heat from 55-70 or so, so approx 15degrees of
> difference, which would come by way of a high efficiency natural gas boiler.
>  During summer, the geo would MORE than cool the home enough, requiring no
> supplementation.

There are issues of condensation and humidity to be dealt with in such
systems. These are not insurmountable problems, but they do require a
bit of additional energy to be introduced into the system. I tried to
talk my in floor heating guy into circulating cold water through the
in floor heating system in the summer, and he was very much against it
on these grounds.

> Certainly the energy savings from this setup would
> be sizable.  If millions of homes across the globe did this, that'd be a lot
> of coal/oil not being burned.

Once again it is the short term capital vs the long term cost. Same
economics as PV panels and wind turbines. Also, you need a particular
geology to make the excavation pay off. Too much rock, and it just
doesn't pay.

> Once the loops are ran/connected, there's no reason we can't use the land
> for other purposes right?  We could still grow crops over them, have animals
> graze, etc.

Yes, but the systems aren't all that big...

> I see what you're saying though, it's a regional thing.  Not everywhere is
> suited for this type of system.  But isn't it a good idea to implement it in
> the areas where we can?  It's nothing but some trenches, and tubing, some
> anti-freeze and plumbing equipment etc.

Yes, conceptually it is pretty simple, but in practice it is a bit
more complex. The trenches have to be pretty deep, repairing leaks is
very difficult so you have to design so that there aren't likely to be
any, you have to deal with ground water and condensation in various
parts of the system. Almost anything is simpler in theory than in
practice, so don't let me discourage you. It has been done
successfully. It is not cheap. It is not easy. Unless you compare it
to something like orbiting solar power satellites or nuclear power
plants... :-)

-Kelly