[Graeme]

Geothermal is my area of expertise, in particular high-temperature (T) geothermal resources. I'm presently working at a drilling site on a high-T geothermal field in New Zealand.
Geothermal resources are divided into 3 basic groups: high-T fields, low-T direct use, and low-T hot-dry rock (HDR). High-T and HDR are used to generate electricity, while low-T resources are used for domestic heating and cooling (heat pumps), greenhouses, OIL RECOVERY and others (see figure 10, iga link below). High-T resources are found at plate boundaries (see figure 12.5, worldenergy link below).

link1
link2
link3

Worldwide direct use is summarised here
link4

Recent developments in geothermal exploration in USA can be found here
link5
link6

and Europe here
link7
link8

Worldwide high T geothermal development is described here
link9

and here: link10
The last link is particularly important IMHO so I want to reproduce their abstract here: The world primary energy consumption is about 400 EJ/year, mostly provided by fossil fuels (80%). The renewables collectively provide 14% of the primary energy, in the form of traditional biomass (10%), large (>10MW) hydropower stations (2%), and the "new renewables" (2%). Nuclear energy provides 6%. The World Energy Council expects the world primary energy consumption to have grown by 50-275% in 2050 depending on different scenarios. The renewable energy sources are expected to provide 20-40% of the primary energy in 2050 and 30-80% in 2100. The technical potential of the renewables is estimated 7600 EJ/year, and thus certainly sufficiently large to meet future world energy requirements.

Of the total electricity production from renewables of 2826 TWh in 1998, 92% came from hydropower, 5.5% from biomass, 1.6% from geothermal and 0.6% from wind. Solar electricity contributed 0.05% and tidal 0.02%. The electricity cost is 2-10 US¢/kWh for geothermal and hydro, 5-13 US¢/kWh for wind, 5-15 US¢/kWh for biomass, 25-125 US¢/kWh for solar photovoltaic and 12-18 US¢/kWh for solar thermal electricity. Biomass constitutes 93% of the total direct heat production from renewables, geothermal 5%, and solar heating 2%. Heat production from renewables is commercially competitive with conventional energy sources. Direct heat from biomass costs 1-5 US¢/kWh, geothermal 0.5-5 US¢/kWh, and solar heating 3-20 US¢/kWh.

Geothermal has the potential to provide 65% of the renewable potential (see Table IV).

[SchroedingersCat]

There are some problems with geothermal. Basically, you are accelerating entropy by moving heat from a hot place to a colder place. Also, geothermal energy is not technically renewable, as the underground well will eventually cool.
Here in California we have several commercial geothermal power plants. It is starting to be shown true that these plants are contributing to an increase in earthquake activity in their areas. Geothermal induced earthquake references

As far as increasing entropy by using the oceans or ground, you might want to look at this thread: Methane Burps

[Graeme]

Chevron to launch geothermal power plant
$this->bbcode_second_pass_quote('', 'U').S. energy giant Chevron is ready to launch a 110-megawatt (MW) geothermal power plant project in Garut, West Java, after a team was set up to hopefully resolve a variety of problems with the local administration.
Located in the "ring of fire" volcano belt, Indonesia is thought to have about 40 percent of the world's geothermal reserves, equivalent to a total of 27,140 MW of power. While the country has several operational geothermal power plants, their combined capacity currently is only 807 MW or about 3 percent of the country's total geothermal potential.

[Starvid]

$this->bbcode_second_pass_quote('', ' ')"The price will be above 4 U.S. cents (per kilowatthour)," said Yudiana.

[Tanada]

$this->bbcode_second_pass_quote('Starvid', '')$this->bbcode_second_pass_quote('', ' ')"The price will be above 4 U.S. cents (per kilowatthour)," said Yudiana.

[GoIllini]

Out of all the U.S. oil companies, Chevron probably is one of the most environmentally friendly/ has the best folks in PR. They're the ones who managed to keep China from buying Unocal, and they're not in the news quite as much about rabidly pushing for drilling in ANWR like Exxon or Conoco.
So to be honest, I'm not that suprised. They're building this 110 MW geothermal plant because they have so much capital from the high oil prices that they don't know what to do with it, and because they can probably still get a *decent* rate of return.
In two years, Chevron will be able to run ads like BP is doing today, and claim that they care about sustainable energy and the environment.

[Caoimhan]

Chevron-Texaco also owns a 59% stake in the Ovonics NiMH battery technology, and have intentionally priced it to prevent it from being a viable option for battery-electric vehicles. So much for evironmental friendliness.

[EnergySpin]

$this->bbcode_second_pass_quote('Caoimhan', 'C')hevron-Texaco also owns a 59% stake in the Ovonics NiMH battery technology, and have intentionally priced it to prevent it from being a viable option for battery-electric vehicles. So much for evironmental friendliness.

[Caoimhan]

It's not something that you can point to in any single document, because the stake that C-T has in Ovonics is hidden through their ownership in several companies which, in turn, own the patent.

Details can be read in THIS POST.

[J-Rod]

$this->bbcode_second_pass_quote('', 'A')n MIT chemical engineer explains why new technologies could finally make "heat mining" practical nearly anywhere on earth.

[Tanada]

$this->bbcode_second_pass_quote('J-Rod', '')$this->bbcode_second_pass_quote('', 'A')n MIT chemical engineer explains why new technologies could finally make "heat mining" practical nearly anywhere on earth.

[mekrob]

Geothermal is an amazing source and doesn't require nearly as elaborate systems as this one advocates. Geothermal has two main uses:
1) Electricity generation as advertised in this article. All you do is find a fault that is near a water source (isn't there another req?) and then drill. You flood the heat source rock with water. This water becomes heated and is then pumped back up to the surface. If it is hot enough, then it will just be steam. You then open up the steam in a turbine, it spins the turbine which spins a generator very rapidly, providing electricity. The water is then pumped back into the ground.
Or if the water is not hot enough, you depressurize the water, making it turn into gas anyway, which spins the turbine and...you get it.
Pros: Very cheap, very efficient, lasts as long as the Earth is naturally warm (too long to measure)
Cons: Potentially devastating to the local area (leaks harmful gases), very very hard to find. It must be along a fault which means there's dangers of earthquakes always.

2) Heating and cooling: Install a series of pipes in your (back)yard, connecting to your house on both ends of the system. The system must be beneath your water table I believe (anywhere from 6-200 feet, depending upon location, rainfall, rocks, etc).
In the summer, the ground is generally 60-70 degrees. Electricity pumps water from the house through the pipes. It cools down and recirculates to the house. A converter uses the cold water to cool the house (I forget the technical stuff). The winter does the exact opposite. Point is, the earth is always a certain temperature depending upon depth and a couple other variables, but very stable.
Pros: the US uses about a third of it's electricity or 10% of it's energy on heating and cooling. This can practically be eliminated with geothermal heat pumps. Heating and cooling consists of 50-60% of the homes electrical needs, thus saving hundreds every year. Costs only 10-15% of your home's value (or cost), so roughly 10-20 thousand. Repays itself in 5-10 years (supposedly). Is generally guaranteed for 50 years but would probably last much longer with very very little maintanence.

It's universal. This can work in the East, West coast, Japan, China, even the desert if you drill a little bit deeper.
Cons: ...none...

[mekrob]

Tanada, But for the electrical generation plants, they are all near faults and fractures, which not surprisingly are right near most volcanoes. Not to mention the fact that if your source rock goes 'dry' which wouldn't happen for about 100 years, you can just drill a little bit deeper again.

[Omnitir]

MIT study backs geothermal as key U.S. energy source.
Some snipits from the article:$this->bbcode_second_pass_quote('', 'E')nergy, it is the first study in some 30 years to take a new look at geothermal, an energy resource that has been largely ignored.
This new study takes a more ambitious look at this resource and evaluates its potential for much larger-scale deployment.
"We've determined that heat mining can be economical in the short term"
The expert panel offers a number of recommendations to develop geothermal as a major electricity supplier for the nation.
Unlike conventional fossil-fuel power plants that burn coal, natural gas or oil, no fuel would be required. And unlike wind and solar systems, a geothermal plant works night and day, offering a non-interruptible source of electric power.

Government-funded research into geothermal was very active in the 1970s and early 1980s. As oil prices declined in the mid-1980s, enthusiasm for alternative energy sources waned, and funding for research on renewable energy and energy efficiency (including geothermal) was greatly reduced, making it difficult for geothermal technology to advance. "Now that energy concerns have resurfaced, an opportunity exists for the U.S. to pursue the EGS option aggressively to meet long-term national needs," Tester observed.

[SchroedingersCat]

Take a look here: Geothermal Energy in California

Use of deep heat to produce electricity has been going on for decades. There does seem to be a risk of increased seismic activity around these sites, however. Hot Rocks
$this->bbcode_second_pass_quote('', 'B')ut geothermal is not entirely risk-free. A recent effort to build such a geothermal power plant in Basel, Switzerland, came to an abrupt halt when it triggered an earthquake measuring 3.4 on the Richter scale, too small to cause damage but large enough to be felt by humans. "We generate between 3,000 and 5,000 earthquakes a year," Calpine's Gilles says.

[pea-jay]

Some personal experience with this: Geothermal for electrical production in the Geysers (CA) was initially produced by pulling the steam directly out, which resulted in a dicernable peak in steam production as the resource was being extracted faster than water was seeping in. The operators built a pipeline from Santa Rosa to carry their waste water, which they now inject. It seems to have held up. Up in Klamath Falls, OR, they too have geothermal resources which have been used more for district and individual space heating applications as well as melting snow on the city sidewalks. They too have gone to reinjecting the water from below to preserve heat production.

The key for both is the water. The heat energy is renewable, but extraction of water beyond a certain point is not. Which raises the next point that GAMPY also touched on. How about just go after the dry heat itself. My only explanation is that it is too expensive and requires too much energy to get down to a level where heat rises to the point where steam can be made to drive a turbine. Not a physics guy here but I imagine the energy costs of having to cycle water from more than a vertical mile or two may exceed the potential energy that could be created from steam.

Then again maybe not

Above is something I've thought about. Imagine a real deep hole and a closed loop of water circulating endlessly down ther
Phase one, the water heats in one tube, well past the boiling point. The use of oneway valves prevents water from reversing flow. Once the water reaches a certain temp, the lower, then upper valves are opened, releasing water into the empty chamber where it instantly flashes over to steam (phase 2) where it drives a steam turbine. Water waiting in the upper part of the first chamber falls down into the heating chamber, spinning another turbine. This phase generates electricity.
Phase 3, the heat energy is expended and the steam condenses back to water in the upper part of the first chamber while the lower part of the chamber starts heating up. Process returns to phase 1.

Line several of these and offset their cycles and you'd got a way to mine heat without a source of water and correct surface geology. This is purely conceptual, Ive got no idea if it works or even is allowed thermodynamically. Maybe the two chamber idea would work better if one chamber discharges to the other and that one heats up and discharges back to the first.

ANY SCIENTIFIC TYPES WANT TO PICK THIS IDEA APART?

[Graeme]

Pea-jay, The system you are describing has been thought of. It's called Hot Dry Rock or Enhanced Geothermal Systems. Although I'm not an expert in this area, you can get an introduction from the links in my post above - hotrock, ucsusa and eere, plus google HDR and EGS.

[reddal]

Hi, I've only recently discovered this whole peak oil concept. I'm not 100% convinced as yet - I'm hoping I can find something which proves you are all just a bunch of nutters . However after reading a couple of books and doing some internet research I'm still searching...
One idea for electricity generation post peak that I haven't seen any killer argument against is geothermal. I don't mean the small scale systems for extracting the heat stored a few feet down - I mean drilling miles down to where its really hot.

I read that this is done today to a limited extent - and apparently there are engineering problems and some locations are much better than others etc. However just intuitively it seems that these problems can't be unsolvable - and without taking decades if there was sufficient motivation....
Compared to some of the alternatives people talk about - like getting nuclear fusion working, or covering significant % of the world in solar panels etc - working out how to dig really deep holes in the ground doesn't sound that hard - lol? If I understand how it works, you dig 2 really deep holes, then pump water down one of them - and superheated steam comes back up the 2nd hole - which you can use to drive turbines etc.

Now - I'm a noob to this stuff - and I imagine theres probably half a dozen reasons why big scale geothermal electricity generation isn't a real option for the future. However I couldn't find them from a brief search - so I'm hoping one of you can put me right - in which case I'll take another step closer to becoming a fully signed up doomer .
thanks - reddal

[Graeme]

Yes, I've been following developments in the US on this for some time now. You are right - there is considerable potential for geothermal development in your country but it seems that this potential can only supply about 10-20% of total demand for electricity. Please do a search for "geothermal" on this site in the forums and news sections and you'll find more information. Especially look for news by MIT and SMU.

[frankthetank]

Check out Iceland. The whole country runs off geothermal and hydro. I think there is a lot of potential out there, its just pretty far off the beaten path and expensive to develop. With the cost of metals spiraling out of control, i doubt you'll see much money move into this sector.