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Science Forum Index » Energy Forum » Tapping Volcanic Energy
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| Scott A Crosby |
 Posted: Thu Nov 13, 2003 9:29 pm |
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On Thu, 13 Nov 2003 17:13:31 -0700, quibbler <quibbler247@yahoo.com> writes:
Quote: In article <oyd8ymnrj91.fsf_-_@bert.cs.rice.edu>, scrosby@cs.rice.edu
says...
On Wed, 5 Nov 2003 14:38:44 -0700, quibbler <quibbler247@yahoo.com> writes:
The issue is that geothermal is a bit player,
No, it's perhaps the most extensive power source on earth if it could
be properly tapped. Of course, I was only talking about details that
Jonas brought up.
There exist lots of hypothetical sources, I'm looking for practical
sources that are reasonably implementable now. When things change, I'm
happy to adjust my expectations. (For one, I'm eagerly waiting for
Mr. Mook to make his billions.) Personally, I'm partial to the idea of
a dyson sphere or, if not that, at least a few thousand square km
solar array in orbit.
Quote: Even proponents who purport huge numbers end up
looking rather small in practice. 77 years of geothermal is NOT what
I'd call renewable.
In theory no form of energy is renewable. In practice there is enough
heat in the entire earth to last as long as humans do, assuming that it
is worth our while to extract it.
I need to be more clear in the future. :)
I was referring to economically useful energy for baseload
production. I'll conced that there is a lot of potential energy there,
but if it cannot be feasibly extracted at a price equivalent to other
alternatives its existance is a moot point, at least right now. If
prices or extraction costs change later, then its existance may become
critical.
Quote: is only enough to run the US's yearly electrical use of 3.6 T kW*h
for 77 years.
That's fine. This is pretty much the argument you use every time.
"Power source X can only provide 100% of our power needs for Y years.
Thats the same argument many of the 'we must save oil' use. If a 50
year supply of oil is enough to panic over, then why should a 77 year
supply of geothermal not also be?
Quote: Since Y is some duration that I consider insignificant, power source X
should never be developed in any way."
I'm not saying that it shouldn't be developed, what I'm saying is that
resources that can seriously contribute to our energy demands should
be developed. 5% here, 5% there, 5% in another corner, 5% swept behind
the bookcase are all good things, but where is the other 80% coming
from? I can't seem to make myself care about the 5% when I feel that
the burning question is the 80%. If one of the 5%'s grows into a 15%
(like wind), then the burning question is the 70%.
Amdahl's law says to focus on the big issues. Perhaps that makes me
too critical of the small issues.
Quote: ***
Have you bothered, on your own, to find/compute any ballpark figures?
Yep.
I applogize if this offended. This is not directed toward you. I
copied this text from a prior post.
Quote:
Here's some as the result of some simple web-searching and physics:
Cubic KM is about 2.5 billion tons, 2.5*10^15 grams. Cooling it by
1300C and crystalizing it (making white-hot lava become 0C) 500 cal/g,
Some lava is over twice this hot.
I used celsius not farenheit. Numbers are from:
http://www.geo.ua.edu/volcanology/lecture_notes_files/physical_properties_of_l.html
Quote: 2000J/g. Total thermal energy: 5*10^18G.[7]
That's still an ok ballpark.
US Elecriticty consumption(1999)[8]:
3.45 trillion kWh= 3.45*10^12 * 3.6*10^6 = 10*10^18
(about 400GW mean consumption)
Now, if I remember right, power generation through thermal means is
about 30% efficient? That'd mean that the entire US energy need would
require cooling about 4.5 cubic kilometers of white-hot lava to 0C per
year. Thats, enough lava to create the main volcano of Hawaii over the
course of about 20,000 years.[9]
Know any sources of lava that big?
Yep. It's called the mantle of the earth.
Yup, but how is the heat brought to the surface? There are issues with
both thermal mass and thermal conductivity.
Since each kg of lava has only about 2MJ of thermal energy, a 500MW
plant (1.5GW of heat) could absorb all heat within a 3m of a radius of
a pipe a kilometer long in a single day. (assuming 30% efficiency, and
lava goes from white hot to 0C.)
I've been looking for thermal conductivity numbers for lava without
success, but I have heard that is is very low. Using aluminum as a
hypothetical upper bound. (taking from another of my past posts on
this)
**
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatra.html
Assuming that you had a magma repository at 1000c seperated by 10
meters of aluminum with ice at 0C on the other side, what would the
thermal conductivity be? Well, if it is aluminum, 200
W/K/m. (Silver is twice this). This is only 20kW/M^2. Average
continental heat flow is .06W/m^2. To equal one nuclear reactor
(good for about 3GW of heat, 1GW of generation), it would need to
have a surface area in excess of 150,000 m^2
**
So, in about 18 days thermal conductivity would upper bound the
maximum heat out of the hypothetical 1km pipe to 1.5GW of heat. If
used as a giant closed loop system, you'd have to drill 2km/month. I
wish I knew what 'low thermal conductivity' meant.
Alternatives would be to drill a pipe to the surface and let the magma
flow up. For that, our 500MW plant would generate at least a hundred
thousand tons of hot rock a day. It may work and I'd certainly love to
see it in operation! :)
A final alternative thats hard to quantify would be to drill only two
holes in fractured rock and pump water between them. Conductivity and
thermal mass imply that such a plant wouldn't function for more than a
few decades before it'd deplete local heat. For reference, see
California Geyser's Recharge project. In 15 years, capacity has
dropped from 1.6GW to 850MW, and now accounts for about 25% of world
installed geothermal electrical production. [2]
I continue my search for other potential baseload electricity sources.
Scott
[1]
http://www.energy.ca.gov/geothermal/fact_sheets/geothermal_projects/SANTA_ROSE_RECLAIMED_H20.PDF
[2] From [1] and http://www.energy.ca.gov/geothermal/overview.html |
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| Pete Lynn |
| Posted: Fri Dec 05, 2003 7:45 pm |
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Just back from Australia, water current project...
"william mook" <william.mook@mokindustries.com> wrote in message
Quote: "Pete Lynn" <pete@peterlynnkites.com> wrote in message
Yes, but the timing is not yet right, nor am I the right person,
perhaps another decade.
Hmm.. that's what they've been saying about *any* development in
space for the past thirty years. Too bad. You had me going there
for a sec.
This is longer than I have lived. :-)
The business case is relatively high risk, I do not have a $100 million,
nor the means or willingness to use other peoples' money. While I would
greatly like to do such a thing now, the task is currently far too great
for my available resources and competencies. I have to build up to such
a task over many years, starting on lesser projects that are within my
grasp. I am hopeful that one day I will be up to such.
Quote: I think those estimates are low. I'm familiar with DC-X and Roton.
Both are no more. Although DC-X is interesting. It took about $60
million to build the demonstrator. But part of the very low cost of
development was the fact that it used RL10 engines, off-the-shelf.
The XVan was a Len Cormier design, with every passing year it gets
easier an the estimates lower, I am thinking more of an up scaled
X-Prize approach. I think the $100 million price tag for such a small
vehicle should now almost be possible. There are various estimates of
vehicles in the three ton payload range coming in at around $200-300
million, and these had definite room for improvement.
Yes, I was assuming a somewhat lower figure and even at that I was
dubious whether it was worth it, better economies in using your own
vehicle, though on orbit assembly would be required.
Quote: The business case for all of this is highly speculative, the
technology is not however.
Yes. As such I would want to spend my own money, (which obviously I do
not have), I doubt the development would be possible otherwise, too many
compromises. For starters, it should probably be done in Russia, also,
at such low cost levels, regulatory hurdles dominate, and must be
avoided wherever possible, (but not safety/reliability).
Pete. |
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| william mook |
| Posted: Mon Dec 08, 2003 11:42 am |
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"Pete Lynn" <pete@peterlynnkites.com> wrote in message news:<1070671557.510134@kyle.snap.net.nz>...
Quote: Just back from Australia, water current project...
"william mook" <william.mook@mokindustries.com> wrote in message
"Pete Lynn" <pete@peterlynnkites.com> wrote in message
Yes, but the timing is not yet right, nor am I the right person,
perhaps another decade.
Hmm.. that's what they've been saying about *any* development in
space for the past thirty years. Too bad. You had me going there
for a sec.
This is longer than I have lived. 
Well, that would give you a little different view certainly. I would
suggest that you become friendly with a librarian, and get some old
copies of LIFE, NEWSWEEK, US NEWS & WORLD REPORT, TIME, AVIATION WEEK,
SCIENTIFIC AMERICAN, POPULAR SCIENCE from say, oh, 1956 through 1966 -
and read all the articles that appear on space - and the ads too! Mix
in TV shows like "21st century" Which was narrated by Walter Conkrite
on CBS.
Before the assasination of Kennedy, space was a great field of
opportunity. Two years after Kennedy's assasination, that went away.
My formative years was that decade just mentioned.
Quote: The business case is relatively high risk, I do not have a $100 million,
nor the means or willingness to use other peoples' money. While I would
greatly like to do such a thing now, the task is currently far too great
for my available resources and competencies. I have to build up to such
a task over many years, starting on lesser projects that are within my
grasp. I am hopeful that one day I will be up to such.
That's great. Every great journey starts with the first step. You
have a worthy goal. Good luck. You know, if no one had gone to the
moon, then there would be those who would always tell us it was
impossible.
Quote: I think those estimates are low. I'm familiar with DC-X and Roton.
Both are no more. Although DC-X is interesting. It took about $60
million to build the demonstrator. But part of the very low cost of
development was the fact that it used RL10 engines, off-the-shelf.
The XVan was a Len Cormier design, with every passing year it gets
easier an the estimates lower, I am thinking more of an up scaled
X-Prize approach. I think the $100 million price tag for such a small
vehicle should now almost be possible. There are various estimates of
vehicles in the three ton payload range coming in at around $200-300
million, and these had definite room for improvement.
I don't have the detailed technical data that would let me make such
statements about these vehicles.
Quote: A proton launch cost over $120 million last I looked.
http://www.space.com/missionlaunches/launches/proton_garuda_000211.html
So, a single launch would shoot your budget in the head. That's all
I'm saying.
Yes, I was assuming a somewhat lower figure and even at that I was
dubious whether it was worth it, better economies in using your own
vehicle, though on orbit assembly would be required.
Orbital assembly has its own risks and costs.
Quote: The business case for all of this is highly speculative, the
technology is not however.
Yes. As such I would want to spend my own money, (which obviously I do
not have), I doubt the development would be possible otherwise, too many
compromises. For starters, it should probably be done in Russia, also,
at such low cost levels, regulatory hurdles dominate, and must be
avoided wherever possible, (but not safety/reliability).
Pete. |
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| william mook |
| Posted: Sun Dec 14, 2003 5:27 pm |
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