We could replace coal power with geothermal—10 times over

[n2doc]

BY SARAH LASKOW
7 NOV 2011 10:56 AM


The United States has so many viable spots for producing geothermal energy -- i.e. tapping into the heat of the Earth’s core to generate power -- that the country's geothermal potential is equivalent to "10 times the amount of coal capacity in place today," according to Climate Progress.

Southern Methodist University developed this geothermal map in partnership with Google.The western half of the country has the greatest potential for geothermal development, but there are hot spots elsewhere -- check out that orange spot in the Northeast. That's in coal country and provides a way to keep jobs while shutting down dirty coal mines and power plants.

http://www.grist.org/list/2011-11-07-we-could-replace-coal-power-with-geothermal-ten-times-over

http://thinkprogress.org/romm/2011/11/06/359699/google-geothermal-supply-chu/

[OKIsItJustMe]

1. See also…

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=314946&mesg_id=314946

[RC]

2. Most of those "Hot Spots" are in inaccessible mountainous areas.

While this true geothermal energy can fill in some of the energy gaps in this country, it is not the panacea its promoters promise.
Why? because most of it in concentrated in hard to get to mountainous areas. Then there are areas like Yellow Stone National Park that would be impacted. On the slopes of beautiful Mount St. Helens? Be skeptical of the hype.

[OKIsItJustMe]

3. What if the hype is credible?

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=315070&mesg_id=315083

http://www.smu.edu/News/2011/geothermal-24oct2011.aspx

…

“This assessment of geothermal potential will only improve with time,” said Blackwell. “Our study assumes that we tap only a small fraction of the available stored heat in the Earth’s crust, and our capabilities to capture that heat are expected to grow substantially as we improve upon the energy conversion and exploitation factors through technological advances and improved techniques.”

…

In this newest SMU estimate of resource potential, researchers used additional temperature data and in-depth geological analysis for the resulting heat flow maps to create the updated temperature-at-depth maps from 3.5 kilometers to 9.5 kilometers (11,500 to 31,000 feet). This update revealed that some conditions in the eastern two-thirds of the U.S. are actually hotter than some areas in the western portion of the country, an area long-recognized for heat-producing tectonic activity. In determining the potential for geothermal production, the new SMU study considers the practical considerations of drilling, and limits the analysis to the heat available in the top 6.5 km (21,500 ft.) of crust for predicting megawatts of available power. This approach incorporates a newly proposed international standard for estimating geothermal resource potential that considers added practical limitations of development, such as the inaccessibility of large urban areas and national parks. Known as the ‘technical potential’ value, it assumes producers tap only 14 percent of the ‘theoretical potential’ of stored geothermal heat in the U.S., using currently available technology.

…

[kristopher]

5. It's another big ol' ring-shank nail in the coffin for nuclear power.

We don't need 10X the capacity of coal plants for it to be extremely important, just 20% of coal's capacity will be plenty. Geothermal is one of the options for dispatchable power, much like the function of natural gas in today's grid built on coal and nuclear.Wind and solar can easily provide the bulk power we need.

The geographic dispersion is nothing short of outstanding when considering new technologies.

http://www.smu.edu/News/2011/~/media/Images/News/2011/Fall%202011/geothermal-UnitedStates-google-SMUlogo-14oct2011.ashx

From wiki:

Geothermal power stations are not dissimilar to other steam turbine thermal power stations - heat from a fuel source (in geothermal's case, the earth's core) is used to heat water or another working fluid. The working fluid is then used to turn a turbine, which in turn a generator to produce electricity. The fluid is then cooled and returned to the heat source.

Dry steam power plants
Dry steam plants are the simplest and oldest design. They directly use geothermal steam of 150°C or greater to turn turbines.<2>

Flash steam power plants
Flash steam plants pull deep, high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines. They require fluid temperatures of at least 180°C, usually more. This is the most common type of plant in operation today.<22>

Binary cycle power plants

Main article: Binary cycle
Binary cycle power plants are the most recent development, and can accept fluid temperatures as low as 57°C. The moderately hot geothermal water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to flash vaporize, which then drives the turbines. This is the most common type of geothermal electricity plant being constructed today.<23> Both Organic Rankine and Kalina cycles are used. The thermal efficiency of this type plant is typically about 10-13%.

See also: http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x315070

[NickB79]

6. How rapidly are binary geothermal plants being built?

Until a few weeks ago I'd never even heard of them. Do you happen to know how many MW there currently are installed, and how many are in production or planned to be built in the next few years?

Also, does the relatively low efficiency have any significant impact on their cost to implement, or do the savings from lack of fuel costs offset it?

[kristopher]

7. Binary cycle is a relatively new approach but there's nothing radical about the tech

I first heard about it in a TV news piece on a plant in Alaska a couple of years ago IIRC. The amount currently installed or planned doesn't inform my comments about the relevance of this resource assessment to the place of geothermal in a renewable grid. The situation is one where we have large quantities of resources well distributed around the country but the distribution is not equal and uniform in all areas. That means that there are different approaches that will work best for different areas.

Making a grid work with all coal, all nuclear, all wind, all solar etc isn't a practical approach in a world where demand is constantly fluctuating. Each generating source has its own set of operational characteristics that determine its importance to the grid. For purposes of a renewable grid one of the challenges is loss of the ability to generate on command AKA "dispatchability". Natural gas is a great form of dispatchable power, but so is hydro, geothermal and all the storage techs. The fact that natgas is already deployed makes it the choice going forward while we lay down the basic infrastructure for bulk power production from solar and wind.

Once that part of the system starts to form up, and in response to various incentives to reduce carbon further, the hope is that we turn the screws down and start making natgas economically unattractive. It will be much easier to abandon than coal or nuclear because the capital costs are much lower.

It is into that void that things like storage or binary cycle geothermal will start to gain real traction. Germany is beginning to approach this point now, I believe.

There is already a lot of this stuff (alternative sources of dispatchable power) floating around, but it isn't anything like what will be called for in the future when it will form a double digit part of the mix. What this study shows is that even if things like biofuels for electric generation don't advance as hoped, that slot is nonetheless covered.

[OKIsItJustMe]

8. You might be interested in reading about them here

http://www1.eere.energy.gov/geothermal/enhanced_systems.html
http://www1.eere.energy.gov/geothermal/pdfs/egs_basics.pdf&id=4691
http://www4.eere.energy.gov/geothermal/projects/binary
http://www4.eere.energy.gov/geothermal/projects/Enhanced
http://www4.eere.energy.gov/geothermal/projects/EGS

[OnlinePoker]

13. I went to the top link in your list

They have an animation that explains the process. One of the things I'm concerned about, though is the fracturing (fracking) that has to take place for the system to work. One of the complaints about gas fracking is they believe it can cause earthquakes. Since much of the geothermal potential is in already earthquake prone areas, would this be a concern for development of this energy source?

[OKIsItJustMe]

14. Yes, that can be a problem. Queue the folks from MIT

http://upload.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=314946&mesg_id=314963

…

http://www.gtherm.net/">GTherm, founded in 2008, says it has come up with an approach that doesn't require any fracturing or water cooling. It uses a kind of solid-state heat exchanger—what the company calls a "heat nest"— at the bottom of wells. The nest draws heat away from the surrounding rock more efficiently, with the help of a highly conductive grout that encases the heat exchanger.

…

Thousands of depleted oil and gas wells across the United States and Canada are prime candidates for development, Parrella says. Temperature data is already known in these fields, significantly reducing exploration costs. Parrella is convinced GTherm can deliver clean power for less than 10 cents per kilowatt-hour.

…

[NickB79]

17. Thanks for the links!

I'm still working through them, but so far interesting reads.

[tinrobot]

9. We drill for oil in the middle of the deep ocean. Talk about inaccessible.

A deepwater oil rig costs almost a billion dollars and has to drill thousands of feet below the surface.

Putting a geothermal plant in an "inaccessible" mountain region can't be any more difficult.

[Nihil]

12. Spot on with that post ...

> We drill for oil in the middle of the deep ocean. Talk about inaccessible.

:toast:

Yes, the practical utilisation of geothermal sites *is* driven by location
but, in those most suitable locations, it is a resource that is very under-used
at the moment - largely as a result of the "BIG PROFIT NOW!" approach rather
than the "sustainable for more than one financial cycle" one that is required.

[XemaSab]

16. Not in California

The Modoc Plateau has some steeper areas, but most of it is flatter than you'd think, almost totally unoccupied, and covered with non-endangered vegetation types which support few rare species.

Ditto for the east side of the Sierras and the Salton trough.

I say we go forward with this. :)

[abelenkpe]

4. K&R nt

[wtmusic]

10. The quality of specific drilling sites is nearly impossible to predict,

it's expensive, and the wells tend to dry up relatively quickly.

Saying the geothermal potential is equivalent to 10 times the amount of coal capacity is similar to saying the amount of sunlight which strikes the Earth is thousands of times what we need.

It will be worth taking seriously when someone drills a 500MW geothermal well that lasts a decade or more - but we're not even close.

[Nihil]

11. Part of the issue is the good old "short term profit" mindset again.

> ... the wells tend to dry up relatively quickly.
>
> It will be worth taking seriously when someone drills a 500MW geothermal
> well that lasts a decade or more

In a similar way to the problems caused by extracting water from an
aquifer at a far higher rate than replenishment or from forcing the
oil out of a reservoir by rapid water pumping, you can totally screw
up a geothermal well by trying to get too much out in too short a time.

The resource being extracted is heat so when you are doing that at
a rate far higher than replenishment (i.e., cooling the rock at a
far greater rate than it is being heated) then it will fail and
"dry up" your site.

This means that if you want a "500MW" plant it will last for a fraction
of the time that a "50MW" would do so. On the other hand, if you ran it
at a "10MW" rate, it would last for the decade or more that you desire.

Smaller geothermal plants providing a lower but constant supply of energy
is (generally) the best way to use this resource - not to directly replace
the major centralised plants but to nibble at the edges.

[OKIsItJustMe]

15. What if you start with pre-existing drill holes, whose temperature is already known?

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=316291&mesg_id=316344

[NickB79]

18. How does a geothermal well "dry up"?

Forgive the ignorance, but I thought geothermal was steady and constant. Nothings being consumed, so how does the well eventually fail?

[wtmusic]

19. "Dry up" is a confusing way to put it.

"The normal lifespan for a deep geothermal well is around 30 years, after which the rock has cooled down too much from the cold water injected into the well. However, if left for 25-30 years, the geothermal well will have heated up again."

http://www.renewableenergyfocus.com/view/12469/drilling-10000-m-deep-geothermal-wells/

[txlibdem]

20. Thanks for clarifying.

I almost posted the same thing.

Question: when the rock at the drilling depth is too cold, why can they not simply drill down further? Or would they have to drill a new hole, and if so how far away??? 10 feet? 1 mile? 20 miles?