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The Potential of Geothermal Power
EskimoJoe wrote with a link to an AP article about progress in the development of geothermal energy. A Swiss company is competing with another in Australia to be the first to commercially develop a geothermal power plant. The concept is simple to understand: earth's core heat transforms water into steam, which in turn causes a turbine to revolve. The potential, though, is enormous. "Scientists say this geothermal energy, clean, quiet and virtually inexhaustible, could fill the world's annual needs 250,000 times over with nearly zero impact on the climate or the environment. 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 summary is misleading, Geothermal power plants already exist.
A Swiss company is competing with another in Australia to be the first to commercially develop a geothermal power plant.
I think they should go on a trip to Iceland... Frankly...
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This will never work because, as we all know, the earth is hollow.
Well they may be right that just 40% of the heat flow through the continental shield of the US may meet the energy demand 56k times over, the ticklish part is extracting the energy in an economic way. So far the only places where geothermal energy is usable is near active Volcanic areas where the geothermal gradient is steep enough to allow high temperatures near the surface and thus a high enough energy density to make the investment profitable (Think Iceland and California). All the other places the heat flow is too low to be usable for anything else than house heating.
Another thing one must address is that the heat flow can only be used where permeable strata exists in the ground making it possible to circulate water to extract the heat. In places with crystalline bedrock, the heat flow can not be used.
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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.
Why do science journalists insist on giving human-unfriendly numbers like this? Is 40 percent feasible? No. Does 56,000 times hold any special significance? No. So why don't they say that 1% would meet demand 1,400 times over? It's a lot more realistic and more comprehensible for readers. Or why don't they say that the USA need only tap a thousandth of a percent of its heat to more than completely power the country? That's more relevant.
I guess we already "make" this heat to power the turbines in power stations(i.e. we transform other types of energy into heat), so I would be inclined to say that using geothermal power would not result in a net increase of heat output on the surface. Unless perhaps, that that now guilt-free and cheap electricity causes everyone to go on a leccy binge for the next 200 years and consumption goes through the roof.
I recently visited Iceland where they use the country's ample supply of superheated steam to produce electricity (and provide hot water and heating). A related question that sprang to mind was "if the rest of the world did this, what would be the effects of letting all that heat out? Would the amount of heat that we would cause to escape from the planet's core be significant? We need a geophysicist to give a proper answer to that - but I'm a suspicious bugger and all this "free" electricity looks too good to be true - you know what they say about free lunches. Essentially, we'd be using the planet like a battery: it's just a question of how long it will last - millions of years? Thousands?
One of the other things that struck me about what the Icelanders are doing, is that they may just have struck their country's equivalent of oil. In the past, they couldn't really export their natural resource - steam goes off quite quickly. Then, they figured out how to make electricity with it, which is a bit easier to store and transport, but not out of the country. Now though, it looks like there may soon be a large world market for hydrogen, if fuel cells and other hydrogen consuming automotive engines take off. Iceland has all the ingredients to produce it - seawater, and abundant electricity. There are a number of problems to overcome in transporting it safely, but I reckon these guys may soon be rolling in it.
The Shell petrol station in Reykjavik already sells hydrogen. It's not clear who to exactly right now, but Shell obviously believes it has a future.
TFA says the goal of the project is nice, but cost is a big barrier. "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."
/ Spending.asp#USMilitarySpending US military spending was over $570 Billion in 2006. So why not spend, oh, say one percent of that figure to go towards coming up with clean energy?
Yea, so that's about six times more expensive. But wouldn't the savings be much more in the long run? And more "environmentally friendly"? After all, according to http://www.globalissues.org/Geopolitics/ArmsTrade
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That said, I am sure that someday in the distant furure, such concerns would be warrented. I can forsee a day when the power needs of the earth and the technology is such that we would be tapping heat more directly from the mantle or core in amounts that we might be able to affect the magnetosphere by cooling the mantle/core significantly. This is not a problem for these projected plans. I would be doubtful of our ability to cool even a localized area enough that we could accomplish something like "eliminate the possibility of the Yellowstone supervolcano erupting." We have to keep in mind the scale of our activities compared to the size of the earth. Our ability to communicate only makes the earth seem to be small....
Finally, on the subject of heating the earth: all electricty generation and consumption creates heat. We take fossil fuels from deep inside the earth and burn them, generate electricity and consume it, converting it back to heat as we do. This is all heat that would not have otherwise ever been found on the surface of the earth. Or we can take heat that is rising to the surface of the earth anyways, fast track it to the surface, generate electricity and do the consumption/conversion thing. Yes, we bring heat to the surface, but since it was on its way to the surface anyways, it seems a no brainer to me.
That being said, Earth is about 6E24 kg. The specific heat of silica & iron (the two most common minerals) is .7 & .45 J/gk - average it to .55. That would mean 3E24 J for a 1 degree drop. 3600J is a watt-hour... so 2.1E19 J is a terawatt-year. That means it would take about 140,000 years of 1TW 'drain' to cool the entire (interior of) earth about 1 degree. Even assuming that all human electricity was generated via geothermal energy, it would take somewhere in range of millions of years.
So, yeah, I wouldn't really worry about it.
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