Abundant Power from Universal Geothermal Energy

Technology Review (MIT) ^ | August 1, 2006 | By Kevin Bullis

[domenad]

I have never understood how Geothermal energy works. Theoretically, a very hot earth core would radiate heat outward until temperature throughout the crust equalized. What produces the heat? If you drain the core of heat, how is it replenished?

[Uncledave]

here's and Aussie firm working on this:
http://www.geodynamics.com.au/

[eraser2005]

Very interesting stuff - thanks for the post

[scooter2]

Abundant, yes. However, it's going to be very expensive to create such reservoirs in areas where near-surface geothermal sources are not available.

[Gay State Conservative]

I'm not sure about the "anywhere in the world" part,but I've seen geothermal power at work in a city in New Zealand called Rotorua.

Many,if not most,of the buildings in the town are heated by geothermal steam (it's located in an active geothermal area).

The downside is that when you're walking down the street you can get a powerful,and unpleasant,smell of sulfur in the air.

[thackney]

Think about emptying the ocean using a thimble.

You are depleting it, but not measurably.

[RightWhale]

What technology do you need to open up the rock and harvest the heat?

Nukes

[RightWhale]

The earth is still giving off more heat than it gets from the sun. The core won't be cooled off much by thermal mining. It should be good at least as long as the sun itself, that is, another 500 million years.

[eraser2005]

The oil industry does this already with water injection and conventional explosives - no need for nukes...

[Michael.SF.]

I don't think the Geyser's is the largest area of Geothermal production in the USA. I believe that honor would go to the Imperial Valley.

Geothermal Energy is not inexpensive due to the corrosiveness and abrasiveness of the fluid and it's effect on the equipment needed to convert this source to energy. The Geothermal Brine pumps for example are made primarily by only one company in the USA (Johnston Pumps), as such the costs are not onbly high due to materials, but unusually high due to higher then normal margins. Others have tried, but with limited success (Flowserve, Goulds, Floway).

Geothermal sounds like a good idea, but it is far more difficult then this article implies.

[RightWhale]

That's the problem. Whatever is done will take building of infrastructure and even if the energy is free the infrastructure is not. Same problem as solar cells and wind power.

[Fudd]

Theoretically, a very hot earth core would radiate heat outward until temperature throughout the crust equalized.

I am not a geologist, so take this with a grain of salt.

Yes, the earth is cooling down, However, the process is cosmically slow, and delayed by mitigating factors such as the decay of radiactive elements in the crust and tidal convection from the Moon's gravitational field. If we had a smaller planet (that cools faster) without a significant moon, our planet would be a cold, lifeless rock (like Mars).

[Uncledave]

I'm in the renewable energy business. I think I'll start a Renewable Energy Ping list.

Who wants on?

[eraser2005]

It doesn't seem like you would need a natural geothermal source like a geyser (think Iceland or Yellowstone)...

Heck, you can get a geothermal heat pump in the middle of Ohio that is enormously efficient. While you get about 93% efficiency out of a gas furnace, you can get 300+% efficiency out of a geothermal heat pump - all that is doing is extracting heat energy from the earth. That's not that unlike what this is proposing. Just think of an open loop system rather than closed loop, and on a MUCH bigger scale...

[Eric in the Ozarks]

We put in a geothermal system (four 200 foot wells under our driveway) when we built our new house five years ago. The AC is essentially free.

[CedarDave]

Don't want to inject fluids under pressure near earthquake zones:
Earthquake Studies -- Triggering quakes with waste

BTW, President Bush installed a geothermal heat pump at his new ranch house in Crawford; however, the pipes are only 300 feet deep, not anywhere near the depth proposed here, and use naturally occurring constant temperature groundwater for heat exchange.

[js1138]

If you drain the core of heat, how is it replenished?

Radioactive decay. This has been understood for nearly a hundred years.

[Species8472]

The average geothermal gradient of the earth is 25°C/km in depth. This means that anywhere that you drill on earth over 4000 meters depth the temperature is above the boiling point of water. You drill to the proper depth, pump water down and collect the steam and recover energy from the heat.

[Gorjus]

What produces the heat? If you drain the core of heat, how is it replenished?

The heat is actually caused by - as the article says - "naturally occurring" radioactive materials. Basically, it's an underground nuclear reactor used to heat water to make steam.

And you don't replenish it, but you probably don't have to worry about depleting it, either, since you're not really changing the amount of radioactive decay, just taking advantage of it.

The problem is money. The 'expert' makes light of the fact that there are a few engineering issues to resolve, and I don't doubt the technology is there to do what he wants. But the cost of establishing and maintaining the reservoirs (and the pumping, etc.) is not small. Would this be economically competitive with above-ground nuclear reactors to provide the same heat? I'd like to see the numbers.

Of course, we're nationally stupid on nuclear reactors - paranoid far beyond any rational risk assessment. So on one hand, you might think it would be easier to use a naturally occuring underground nuclear reactor instead. But the first time there's a tiny little earthquake somewhere that someone blames on the drilling, or the pressure, or whatever . . .

It's not clear to me that the socialists who live for the power of restricting other people's choices will ever allow such a 'risky scheme.'