[Graeme]

Energy search goes underground

$this->bbcode_second_pass_quote('', 'A') study released this year by the Massachusetts Institute of Technology said if 40 percent of the heat under the United States could be tapped, it would meet demand 56,000 times over. It said an investment of $800 million to $1 billion could produce more than 100 gigawatts of electricity by 2050, equaling the combined output of all 104 nuclear power plants in the U.S.

"The resource base for geothermal is enormous," Professor Jefferson Tester, the study's lead author, told The Associated Press.

But there are drawbacks — not just earthquakes but cost. A so-called hot rock well three miles deep in the United States would cost $7 million to $8 million, according to the MIT study. The average cost of drilling an oil well in the U.S. in 2004 was $1.44 million, according to the U.S. Energy Information Administration.

Also, rocks tapped by drilling would lose their heat after a few decades and new wells would have to be drilled elsewhere.

Bryan Mignone, an energy and climate-change specialist with the Brookings Institution in Washington, D.C., said alternative sources of energy face stiff price competition.

"Currently in the U.S. new technologies in the power sector are competing against coal, which is very cheap," he said.


Susan Petty, one of the 18 co-authors of the MIT study, works for Black Mountain Technology, a company promoting hot rock energy. She predicts that 10 percent of the world's power could come from geothermal sources in the next 50 years, from the current 0.3 percent, rising to half in around 100 years.

[wisconsin_cur]

So will the physicists in the room help me out here.

The middle of the earth is hot because of gravity and friction? As the earth moves around the sun things are moved and squished and thereby produce heat?

Gravity is a function of mass and while, as an energy source, it is not created or destroyed it does seem like a truly "infinite" source since it is not "spent" in the process of burning it (ie the earth's core has been hot for a very long time.)

I freely confess that this is based on what I remember of my High School science class. What above is wrong with my analysis? What would be the drawback of using the earth internal heat on a massive scale? Could it produce an positive EROI assuming we have the resources and the good sense to use our current energy surplus to start the ball rolling?

[lawnchair]

Much of the geothermal energy is a result of spontaneous decay of mostly Uranium, Thorium, and Potassium-40. Eventually, most of these isotopes would decay and the core of the Earth will get colder. However, since their half-lives are on the order of 1e9 to 1e10 years, this source will only get to half its current power before the sun dies.

[EnergyUnlimited]

$this->bbcode_second_pass_quote('wisconsin_cur', '
')Gravity is a function of mass and while, as an energy source, it is not created or destroyed it does seem like a truly "infinite" source since it is not "spent" in the process of burning it (ie the earth's core has been hot for a very long time.)

[Blacksmith]

Deep wells pose a particular set of problems, particularly with regard to the mud system, as they found out in Iceland when they went deep. The mud system must cool the bit, remover cutting, and maintain the intergrety of the hole (by maintaining a pressure against the sides of the hole). You can solve some of you rock pressure problems by running casing, but then your hole gets smaller.
I am sure technology and good engineering will eventually beat the problem, but for now it is a consumation devoutly to be wished.

[WatchfulEye]

Does anyone have any hard figures for how long geothermal resources last?

The article alludes to a 'few decades', but how variable is this, and what sort of extraction profile is available?

I know that it places where heavy use has been made of geothermal resources (e.g. in Iceland, and some parts of California) they are finding that there reserves are 'tapped out' - and this isn't just individual wells that are tapped out, but potentially whole 'heat fields'.

[steam_cannon]

$this->bbcode_second_pass_quote('wisconsin_cur', 'T')he middle of the earth is hot because of gravity and friction? As the earth moves around the sun things are moved and squished and thereby produce heat?

[frankthetank]

Just a thought, and this has been discussed on here before, but wouldn't it be easier to get at the hot stuff near the surface (Yellowstone/etc) then dig holes miles deep?

[steam_cannon]

Small scale Geothermal
* Home heating/cooling systems like heat pumps are fairly easy to install and the shallow ground recharges seasonally.
* Air tubes though the ground can be used similarly to draw heat or cool air to maintain a more constant temperature for a dwelling.
* Caves, living in a cave would be the natural form of geothermal.



Small scale geothermal probably has good prospects. Like if we go back to the stone age and end up living in caves! Hahaha

[steam_cannon]

Large Scale Geothermal - for power generation
* Drawing heat for generators...
This requires intense heat to be near the surface or very high energy prices to be economical.

$this->bbcode_second_pass_quote('frankthetank', 'J')ust a thought, and this has been discussed on here before, but wouldn't it be easier to get at the hot stuff near the surface (Yellowstone/etc) then dig holes miles deep?

[Blacksmith]

Small scale geothermal, with the exception of sea water, are really just a heat sink or storage system which requires energy to pump the fluid through the system. In addition thay are quite expensive to install and I question the economics.

[steam_cannon]

Summary of my thoughts

The bankers think it is a very interesting study but no one is putting any money into this. Maybe it's a technology we could use in the future, but there is almost no implementation of this deep well stuff in the present. And at max production, it could only supply 10% of energy at 2005 levels. Plus it would dreg up huge volumes of arsenic...

[Blacksmith]

http://www.madsci.org/posts/archives/ma ... .Es.r.html

http://www.damninteresting.com/?p=567

[frankthetank]

steam-

I'm not serious. It was just a thought. Its never going to happen. This article is just more "we'll be saved by technology" bullshit. It's too late anyways.

[steam_cannon]

The Deepest Hole
$this->bbcode_second_pass_quote('Blacksmith', 'h')ttp://www.madsci.org/posts/archives/mar97/855593397.Es.r.html

http://www.damninteresting.com/?p=567

[Blacksmith]

It's called deficit spending.

[steam_cannon]

$this->bbcode_second_pass_quote('frankthetank', 'J')ust a thought, and this has been discussed on here before, but wouldn't it be easier to get at the hot stuff near the surface (Yellowstone/etc) then dig holes miles deep?

[Zardoz]

I've been in the industrial supply business since 1972. I've sold a ton of stuff to the geothermal industry.

Theoretically, it's a great source of energy. The problem is the fantastic mineral content of the hot geothermal brine. You have to have mechanical equipment to recover the heat from the brine, and the super-heavy mineral content clogs, erodes, and corrodes the equipment something awful. I've been through many geothermal plant equipment boneyards, and the condition of the scrapped hardware is something to see.

It's been a while since I've had any contact with geothermal producers as I'm now working with different types of equipment, but the last I heard, the problem was not close to being solved. Personally, I don't see how it can be.

Down the road, when oil gets scarce, perhaps the economics of geothermal power will look better. For now it's still an expensive way to generate electricity. I think it always will be.

(BTW, for reference, here's the official site of the largest geothermal plant in the world:

The Geysers )

[EnergyUnlimited]

$this->bbcode_second_pass_quote('steam_cannon', '[')b]The Deepest Hole
$this->bbcode_second_pass_quote('Blacksmith', 'h')ttp://www.madsci.org/posts/archives/mar97/855593397.Es.r.html

http://www.damninteresting.com/?p=567

[steam_cannon]

$this->bbcode_second_pass_quote('EnergyUnlimited', '.')..and first man in space as well.