Geothermal Power

[Airbrush]

In 2008, according to Wiki, over 10% of world power generation was from geothermal. (2008 approx. sources: OIL 34%, COAL 27%, NAT GAS 21%, GEOTHERMAL 10%, NUCLEAR 6%, HYDRO 2%)

 

If you tunnel deep enough under ground, you reach high temperatures. Why not just tunnel deep enough, inject water, and harness the resulting steam? In hot areas, such as near volcanos, you don't need to tunnel very deep to get to hot stuff.

Edited April 8, 2014 by Airbrush

[Greg H.]

Why not just tunnel deep enough, inject water, and harness the resulting steam?

This is pretty much how geothermal power works.

 

See http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/how-geothermal-energy-works.html for more details.

[Sensei]

In 2008, according to Wiki, over 10% of world power generation was from geothermal.

 

Where do you have such data?

 

http://en.wikipedia.org/wiki/Renewable_energy

[Airbrush]

Good question Sensei. I was in Wikipedia when I found those numbers, now I can't find them again. So geothermal is much lower only 0.19%, only a fifth of one percent. I wonder why? Are there that few places on Earth that can be dug into? All you need to do is dig about 6 miles deep and anywhere on Earth could produce geothermal power.

Edited April 8, 2014 by Airbrush

[Sensei]

In

http://en.wikipedia.org/wiki/Geothermal_electricity

there is

"El Salvador, Kenya, the Philippines, Iceland and Costa Rica generate more than 15% of their electricity from geothermal sources."

 

But it's just these couple countries. Not entire world.

[Acme]

Geothermal power plants can induce earthquakes, so caution is warranted.

 

 

Geothermal Power Plants Are Causing Earthquakes Near San Andreas Fault

...

30-Year Study Finds Connection

The study, published July 11 in Science, analyzed 30 years of earthquake data since the geothermal power plants began operation on the southern edge of the Salton Sea in 1982. The study found earthquake activity rose in conjunction with geothermal power production. From 1981 through 2012, more than 10,000 earthquakes above magnitude 1.75 occurred in the area of the geothermal power pants. The largest quake measured 5.1 on the Richter scale.

...

source: >> http://news.heartland.org/newspaper-article/2013/08/13/geothermal-power-plants-are-causing-earthquakes-near-san-andreas-fault

[Enthalpy]

Earthquakes were also observed "in relation" with fracking for shale oil and gas.

At least for the quake in the Rhine valley, it happened as I had just applied at the geothermal energy company, and resulted from "human error" as they call it. That is, it didn't need to happen.

 

You can consider it differently: if one builds a home in a quake-prone region, the house shall be quake-safe, please. Basel was completely destroyed few centuries ago, so homes damaged by a magnitude <3 have nothing to do in the upper Rhine valley - whatever triggers the quake. If there's a devastating quake every 500 years and you build your house for >50 years, the odds are 1 to 10.

[Acme]

Earthquakes were also observed "in relation" with fracking for shale oil and gas.

At least for the quake in the Rhine valley, it happened as I had just applied at the geothermal energy company, and resulted from "human error" as they call it. That is, it didn't need to happen.

 

You can consider it differently: if one builds a home in a quake-prone region, the house shall be quake-safe, please. Basel was completely destroyed few centuries ago, so homes damaged by a magnitude <3 have nothing to do in the upper Rhine valley - whatever triggers the quake. If there's a devastating quake every 500 years and you build your house for >50 years, the odds are 1 to 10.

I agree that fracking has been shown to have caused some quakes. Moreover there is evidence it has contaminated groundwater.

 

As to geothermal power I think I'll stick with the years-long scientific study over your brief anecdotal observations, particularly when it comes to suggestions of drilling deep into volcanos as put forward in the OP.

[Endy0816]

A wise man is he who builds his house upon the sand. Sink hole risk could be better, but very few earthquakes.

 

Main issue with geothermal is that other types of plants offer higher thermal efficiencies. The temperatures we have access to are not that hot for all that the source is more or less free.

[Acme]

A wise man is he who builds his house upon the sand. Sink hole risk could be better, but very few earthquakes.

 

...

A wise person is one who knows that sink holes are [primarily] an artifact of karst topography and sandy soil is subject to liquefaction during an earthquake.

 

karst topography: >> http://en.wikipedia.org/wiki/Karst

soil liquefaction: >> http://en.wikipedia.org/wiki/Soil_liquefaction

[Endy0816]

A wise person is one who knows that sink holes are [primarily] an artifact of karst topography and sandy soil is subject to liquefaction during an earthquake.

 

karst topography: >> http://en.wikipedia.org/wiki/Karst

soil liquefaction: >> http://en.wikipedia.org/wiki/Soil_liquefaction

 

Still a good distance from the fault lines too.

 

Much more concerned with depleted aquifers. I count myself lucky every day when I wake up and my bed hasn't fallen into some gaping maw of the Earth.

[Acme]

Still a good distance from the fault lines too.

 

Much more concerned with depleted aquifers. I count myself lucky every day when I wake up and my bed hasn't fallen into some gaping maw of the Earth.

What's not to love about a gaping maw? I count myself lucky every morning that I don't wake up dead from any cause.

 

Here's something on induced quakes while we wait to die.

 

...Current and Future Research

 

The USGS is coordinating with other federal agencies, including the EPA and Department of Energy, to better understand the occurrence of induced seismicity through both internal research and by funding university-based research with a focus on injection-induced earthquakes from wastewater disposal technologies. For instance, USGS and its university partners have deployed seismometers at sites of known or possible injection-induced earthquakes in Arkansas, Colorado, Ohio, Oklahoma and Texas. The USGS is also monitoring seismicity associated with a geologic carbon dioxide sequestration pilot project at Decatur, Illinois, and is working with industry, academia and other government agencies to study seismicity associated with geothermal energy development and production in California and Nevada.

 

Evidence from some case histories suggests that the magnitude of the largest earthquake tends to increase as the total volume of injected wastewater increases. Injection pressure and rate of injection may also be factors. More research is needed to determine answers to these important questions. ...

source: >> http://earthquake.usgs.gov/research/induced/

 

Then there is the Oklahoma swarm. It is of course not my fault.

 

Since January 2009, more than 200 magnitude 3.0 or greater earthquakes have rattled Central Oklahoma, marking a significant rise in the frequency of these seismic events.

 

The U.S. Geological Survey and Oklahoma Geological Survey are conducting collaborative research quantifying the changes in earthquake rate in the Oklahoma City region, assessing the implications of this swarm for large-earthquake hazard, and evaluating possible links between these earthquakes and wastewater disposal related to oil and gas production activities in the region.

 

Studies show one to three magnitude 3.0 earthquakes or larger occurred yearly from 1975 to 2008, while the average grew to around 40 earthquakes per year from 2009 to mid-2013. ...

source: >> http://www.usgs.gov/newsroom/article.asp?ID=3710#.U0WrlI2PJLM

 

While these are instances where pressure is being forced down a well, one might expect similar results from geothermal power production where pressure is being forced/released up a well.

[Enthalpy]

Main issue with geothermal is that other types of plants offer higher thermal efficiencies. The temperatures we have access to are not that hot for all that the source is more or less free.

 

Vapour rises at >300°C depending on the location and depth. That's as good as in water-cooled nuclear reactors, which have >30% conversion efficiency. Compare with 45% for gas power plants, and keep in mind that Earth's heat is for free.

Since January 2009, more than 200 magnitude 3.0 or greater earthquakes have rattled Central Oklahoma, marking a significant rise in the frequency of these seismic events.

 

In the former coal mining basin where I live presently, all houses tilt, some being rendered unuseable. A magnitude 3 quake makes less damage.

[Danijel Gorupec]

I don't understand some of you guys here... Why are you talking about 10km deep borehole as if it is a piece of cake? We are drilling into the Earth crust vigorously for decades and such depth still is an expensive adventure... and no one can say that our drilling technology is immature.

 

It seems that it is genuinely hard to drill deep holes. As a result, with today technology, we are either limited to low-temperature-low-efficiency plants, or to high-temperature-big-business plants. If this is true, we cannot expect that geothermal electrical plants will become as wide-spread as solar or wind. Big business might also prefer other reasons than ecology (and I am not suggesting that big-business is evil).

 

I suppose that geothermal heating of homes has more potential to become a wide-spread technology than electrical generation. Drilling low-depth (few km) holes might become a rudimentary job, maybe... (On the other hand, you can heat your home from coal/gas/nuclear plant for even less money. Not something you can do with wind or PV plants, btw.)

 

But the one thing I read on Wikipedia is the worst of all -> the heat flows to the Earth's surface at 30TW rate! This is much less than I expected (I even doubt it incorrect?). We will need that much in only a few years. In a hundred years 30TW might represent only 10% of our needs. Not much future for the geothermal energy, I would say.... Makes me sad.

[Endy0816]

Vapour rises at >300°C depending on the location and depth. That's as good as in water-cooled nuclear reactors, which have >30% conversion efficiency. Compare with 45% for gas power plants, and keep in mind that Earth's heat is for free.

 

Most geothermal plants are in the range of 10-23%. It is only the best sites that are in the upper percentile range.

Edited April 10, 2014 by Endy0816

[Enthalpy]

 

Most geothermal plants are in the range of 10-23%. It is only the best sites that are in the upper percentile range.

 

The primary source is for free, so efficiency doesn't make the cost directly. It's more a question of investment versus production.

We are drilling into the Earth crust vigorously for decades and such depth still is an expensive adventure.

 

Like 1M$ for one hole. That can be a reasonable investment to provide heat and electricity to a town.

 

Geothermal energy would need more holes than oil and gas, sinking the unit cost. Extinguishing rig fires was also considered mature technology, but when all Koweit rigs burned, people found methods to extinguish them hundred times faster and cheaper than before.

I suppose that geothermal heating of homes has more potential to become a wide-spread technology than electrical generation.

 

Think at co-generation. Produce electricity with a limited conversion efficiency, heat the homes with the unconverted energy. Operational with fossile fuels, just transfer the technology 1:1 to geothermal.

You can heat your home from coal/gas/nuclear plant for even less money. Not something you can do with wind or PV plants, btw.

 

No. Nuclear electricity is expensive, much more than fossile fuels, and more than wind power. Britain has just guaranteed a MWh price for its future EPR more expensive than for wind electricity.

 

Please don't suggest (I know you haven't) heating homes from reactors without conversion to electricity. Reactors are concentrated poison. Connecting cities to them through a shisha would be insane.

The heat flows to the Earth's surface at 30TW rate! This is much less than I expected (I even doubt it incorrect?). We will need that much in only a few years. In a hundred years 30TW might represent only 10% of our needs.

 

That's absolutely right in principle, though I didn't check the figures again. The total flux is comparable with Mankind's energy consumption. So strictly speaking, it isn't a renewable energy.

 

It remains very interesting nevertheless, because the heat stored in Earth's accessible rocks is immense, and covers our consumption for millenia. Call it an abundent fossile clean energy if you wish, I won't argue about the words - but it's there and advantageous.

[Airbrush]

Geothermal all depends upon our ability to drill holes very deep. Why not think of it as a long-term project? Drill as many holes as you can, as deep as you can, and in the future with better technology, you can make the holes wider and deeper. Why can't we invent autonomous tunneling machines that can be set to dig straight down, and move on to start the next one?

 

This sounds nuts, but could you invent a nuclear device that is intended to melt down in such a way that it goes straight down the 6 miles you need to go, at which time it simply merges into the lava beneath, not to return to the surface?

 

If we are ever to become a Type I civilization we will need to harness all volcanos on Earth (in addition to controlling the weather). Render volcanos harmless by allowing them to constantly erupt in a predictable manner, and also use them to cool the Earth from the warming trend, and as a bonus harness the geothermal energy closer to the surface?

Edited April 12, 2014 by Airbrush

[Danijel Gorupec]

No. Nuclear electricity is expensive, much more than fossile fuels, and more than wind power. Britain has just guaranteed a MWh price for its future EPR more expensive than for wind electricity.

 

Please don't suggest (I know you haven't) heating homes from reactors without conversion to electricity. Reactors are concentrated poison. Connecting cities to them through a shisha would be insane.

 

I was referring here to heating homes from a thermal plant waste heat - in a sense that if you already have the thermal electrical plant, then you can cheaply heat homes with that waste heat (PV/Wind do not offer this possibility) - this in a sense increases thermal plant efficiency. I was not referring to price of electricity from nuclear or fossil-u plant. (Btw, I am only partially agree that the nuclear produced energy is more expensive than wind - we can discuss this if you want, but I am afraid this could be off topic here?)

 

I agree that public would not accept home heating from nuclear plant even if it is from its tertiary circle. But I don't think that, technically, there is more radioactivity problem with nuclear plant tertiary circle than it is with geothermal heating... Do you disagree?

 

I mostly accept your other claims.

[Tim the plumber]

Good question Sensei. I was in Wikipedia when I found those numbers, now I can't find them again. So geothermal is much lower only 0.19%, only a fifth of one percent. I wonder why? Are there that few places on Earth that can be dug into? All you need to do is dig about 6 miles deep and anywhere on Earth could produce geothermal power.

Or very near the surface if you have a handy volcanoe.

 

Yellowstone and Etna spring to mind.

[Sensei]

Geothermal all depends upon our ability to drill holes very deep. Why not think of it as a long-term project? Drill as many holes as you can, as deep as you can, and in the future with better technology, you can make the holes wider and deeper.

 

Internal heat of Earth is result of decay of radioactive isotopes that are present inside of Earth, and initial heat of forming planet.

It's *finite* source of energy.

 

There is finite quantity of radioactive isotopes, and new one meteorites are rare at this stage of formation of Solar System.

At one day they will all change to stable isotopes and no longer release enough energy.

 

Abusing geothermal power would lead to unprecedented results.

 

You have many examples in Solar System of what happens with planets or satellites after losing all heat: Mars or Moon.

 

Lack of energy will change metal liquid core to solid, which would result in lost of magnetic field, which would result in lost of protection against Solar storms, flares, particles with high energy.

Which would lead to lost of atmosphere and sudden death of all organisms.

 

[Airbrush]

Even a vast number of geothermal "steam-wells" would be mere pin pricks in the Earth's crust. They would not even reach the outer mantle and certainly not interfere with the outer liquid core convection currents that creates our magnetic field.

 

 

Edited April 14, 2014 by Airbrush

[Enthalpy]

 

I was referring here to heating homes from a thermal plant waste heat - in a sense that if you already have the thermal electrical plant, then you can cheaply heat homes with that waste heat (PV/Wind do not offer this possibility) - this in a sense increases thermal plant efficiency.

[...]

But I don't think that, technically, there is more radioactivity problem with nuclear plant tertiary circle than it is with geothermal heating... Do you disagree?

 

Accidents do happen, and not in the way we imagined them, because then we would have avoided them (often). So instead of "safe because on the tertiary circuit" is say "unsafe because of pipes between a reactor and homes". The toxicity of a nuclear reactor is so immensely huge that any connecting tube is too much.

[Airbrush: dig 6 miles deep anywhere to have geothermal power]

 

Or very near the surface if you have a handy volcano.

 

Yellowstone and Etna spring to mind.

 

It doesn't even need an active volcano. Geothermal energy works in the Rhine valley or in Bavaria, because people want so. The next active volcano is 1,000km away, the next geyser 2,000km. Volcanos quiet since millenia are nearer, like 300km.

 

These are only especially favourable places. Geothermal heat is available everywhere - but the investment and returns differ, sure.

[Tim the plumber]

^ Yes sure.

 

The choice is one of cost of power lines to a volcano or the cost of drilling a deep hole.

 

I don't see why anyone would choose nuclear over drilling a hole into the ground. It has to be a lot cheaper than the billions needed for a nuclear power!

[Endy0816]

 

Accidents do happen, and not in the way we imagined them, because then we would have avoided them (often). So instead of "safe because on the tertiary circuit" is say "unsafe because of pipes between a reactor and homes". The toxicity of a nuclear reactor is so immensely huge that any connecting tube is too much.

 

You would need contamination to go from the primary to the secondary to the tertiary. In physical terms we're talking about leaks in two separate heat exchangers. If the maintenance team is that incompetent you have much bigger issues.

 

At some point you have to dump the heat back to the environment. Can't get around that. Better to use it and minimize the thermal footprint of your reactor.

Edited April 24, 2014 by Endy0816

[Acme]

Internal heat of Earth is result of decay of radioactive isotopes that are present inside of Earth, and initial heat of forming planet.

It's *finite* source of energy.

 

There is finite quantity of radioactive isotopes, and new one meteorites are rare at this stage of formation of Solar System.

At one day they will all change to stable isotopes and no longer release enough energy.

...

These are not the only factors heating Earth. Tidal heating from the Moon has been and remains a contributor. Granted it is slight today, but it is there.

 

...

The Earth was thought unique as the only active planet in the solar system with its plate tectonics, volcanic resurfacing, and biological life. Earth was assumed to still have its heat from accretion only because of its relatively large size. In general, secondary or tidal heating was not considered a significant contributor to overall planetary heating. Recent findings throughout the solar system make us aware that tidal heating caused by the gravitational pull of two bodies is very much a factor.

...

Tidal heating in the Earth-Moon system would impact both bodies. Geologic evidence of a tidal heating event on the Earth and Moon, expressed by the outpouring of basalts, could confirm a close approach of the Moon to Earth and allow for the place of this event in the geologic timescale. A mechanism for reheating in the Earth-Moon system could provide the energy source that drives the Earths current dynamic systems and thus offers an explanation for why the Earth has remained so geologically active. Although the Moon is not appreciably heated by tidal heating at its current distance from the Earth, the potential impact of tidal heating at the previously close distance should be investigated.

source: >> http://lunarorigin.com/tidal-heating

 

This source gives the value from tidal heating as .007 W/m² (Scroll down to the illustration of cubes.) >> http://www.skepticalscience.com/heatflow.html

...The spinning of the Earth, as well as the rotation of the Moon around the Earth and the orbit of both bodies around the Sun, do indeed have an impact on the energy of the Earth, through tidal friction. The ultimate source of this energy is the Earths rotation, to which the Moon and the Sun provide a gentle brake, resulting the generation of frictional heat and the slowing down of the Earths rotation (days were two hours shorter 600 million years ago). The Moon gains some energy from this interaction, being gradually boosted into a higher orbit above the Earth. The total Earth energy flow from tidal effects is about 3.7 TW (0.007 Wm-2 ), of which 95% goes into the familiar ocean tides and some 5% (0.2 TW or 0.0004 Wm-2) goes into Earth tides, which are small deformations of up to a few centimetres that occur on twice-daily or longer timescales. Earth tides contribute approximately 0.5% to the heat flow of the Earth. ...