Abundant Power from Universal Geothermal Energy

An MIT chemical engineer explains why new technologies could finally make "heat mining" practical nearly anywhere on earth.

A section of the geothermal plants north of San Francisco, known as The Geysers. These plants rely on relatively rare geologic formations. MIT professor Jefferson Tester believes geothermal can be much more widespread, by making artificial reservoirs for harvesting the earth’s heat. (Source: National Renewable Energy Laboratory)

The answer to the world's energy needs may have been under our feet all this time, according to Jefferson Tester, professor of chemical engineering at the MIT Laboratory for Energy and the Environment. Tester says heat generated deep within the earth by the decay of naturally occurring isotopes has the potential to supply a tremendous amount of power -- thousands of times more than we now consume each year.

So far, we've been able to harvest only a tiny fraction of geothermal energy resources, taking advantage of places where local geology brings hot water and steam near the surface, such as in Iceland or California, where such phenomena have long been used to produce electricity. But new oil-field stimulation technology, developed for extracting oil from sources such as shale, makes it possible to harvest much more of this energy by allowing engineers to create artificial geothermal reservoirs many kilometers underground.

Tester calls it "universal geothermal" energy because the reservoirs could be located wherever they're needed, such as near power-hungry cities worldwide.

Technology Review spoke with Tester about the potential of universal geothermal energy and what it will take to make it a reality.

Jefferson Tester: The figure for the whole world is on the order of 100 million exojoules or quads [a quad is one quadrillion BTUs]. This is the part that would be useable. We now use worldwide just over 400 exojoules per year. So you do the math, and you know you've got a very big source of energy.

How much of that massive resource base could we usefully extract? Imagine that only a fraction of a percent comes out. It's still big. A tenth of a percent is 100,000 quads. You have access to a tremendous amount of stored energy. And assessment studies have shown that this is thousands of times in excess of the amount of energy we consume per-year in the country. The trick is to get it out of the ground economically and efficiently and to do it in an environmentally sustainable manner. That's what a lot of the field efforts have focused on.

JT: In some cases nature has provided a means for extracting stored thermal energy. We have many good examples. The Geysers field in California is the largest geothermal field in the world -- it's been in production for over 40 years and produces high-quality steam that can readily be converted into electric power, and it's one of the rarities nature-wise in terms of what we have worldwide. In the mineral vernacular they would be regarded as sort of high-grade gold mines.

TR: But haven't people been talking about greater use of geothermal energy for years now? What's changed?

JT: Like many energy technologies, it had a lot of support structure back in the 70s and in the 80s, but our national priorities shifted from energy to other things, and we didn't necessarily invest enough in it at that time to bring it to fruition.

Many [energy] technologies, whether they're renewables or nuclear power or coal or whatever it might be, need to be continually revisited and placed in context with the current state of technology. In this case, our interest in trying to go after hydrocarbons and extract hydrocarbons has developed a lot of technology in subsurface engineering that's useful and makes geothermal worth revisiting.

JT: What we're trying to do is emulate what nature has provided in these high-grade systems. When we go very deep, [rocks] are crystalline. They're very impermeable. They aren't heat exchangers like we really need. We'd like to create porosity and permeability. [The rock] actually is filled with small fractures, so what you're trying to do is find those weak zones and reopen them. We need to engineer good connectivity between an injection set of wells and a production set of wells, and sweep fluid, in this case, water, over that rock surface so that we extract the thermal energy and bring it up another well.

JT: All the technology that goes into drilling and completing oil and gas production systems, [such as] stimulation of wells, hydraulic fracturing, deep-well completion, and multiple horizontal laterals, could in principle be extended to deep heat mining. Hydraulic methods have been the ones that hold the most promise, where you go into the system and you pressurize the rock -- just water pressure. If you go higher than the confinement stress, you will reopen the small fractures. We're just talking about using a few thousand pounds per square inch pressure -- it's surprising how easy this is to do. This is a technique that's used almost every single day to stimulate oil and gas reservoirs.

TR: What still needs to be done to make artificial reservoirs for geothermal possible?

JT: Like any new technology, there are technical issues. But I don't see any show-stoppers. I think that the evolution of the technology, with 30-plus years of field testing, has been very positive. The basic concept has been demonstrated. We know how to make large reservoirs. We need to connect them better, to stimulate them better than we have in the past using some of these hydraulic methods and diagnostics that are now available to us.

So it's the scale-up to a commercial-sized system that has to be done, making a heat mine that is large enough and productive enough to sustain the economic investment. But we believe that's possible to do based on where we are now with the technology.

JT: We feel that as part of a long-term view of the possibility of universal heat mining, we should also be thinking about revolutionary methods for cutting through rock and completing wells. Most of the drilling that's done today is made by crushing and grinding our way using very, very hard materials to crush through and grind through minerals in the rock. And it's been very successful. It's evolved tremendously over the past century, and we can do it, certainly, routinely, to 10 kilometers. But it costs a lot. So we're looking for a fundamental way to change the technology that would change the cost-depth relationship, and allow us to drill deeper in a much more cost-effective manner. It would open up the accessibility tremendously.

JT: Geothermal has a couple of distinct differences. One, it is very scalable in baseload. Our coal-fired plants produce electricity 24 hours a day, 365 days a year. The nuclear power plants are the same way. Geothermal can meet that, without any need for auxiliary storage or a backup system. Solar would require some sort of storage if you wanted to run it when the sun's not out. And wind can't provide it without any backup at 100 percent reliability, because the typical availability factor of a wind system is about 30 percent or so, whereas the typical availability factor of a geothermal system is about 90 percent or better.

JT: Obviously in any system where you're going underground, you need to think about are you disturbing the natural conditions in the earth that might cause bad things to happen. We have a pretty good history of knowing the effects of extraction. Nevertheless, it has to be monitored carefully and managed carefully.

In some natural systems you have to deal with the emissions -- control of hydrogen sulfide and other gases. Environmental regulations insist on full re-injection of the fluid.

This is not a free lunch, but there's virtually no carbon dioxide, so you're producing baseload electric power without generating any carbon dioxide.

JT: With sufficient financing and a well-characterized field, you can go into existing areas right now and build a plant, getting it operational within a few years. But to get universal heat mining is going to take an investment which won't be quite that quick. It might take 10 or 15 years of investment to get to the point where you have confidence that you can do this in virtually any site that you can go to. Once it gets in place, though, it can be replicated. I think it's very reproducible and expandable. That's the great hope at least.

What perspective did you THINK I had, other than relative to the entire USA??

Well, since the link I provided was to an international company, and I posted a map showing world wide distribution of plants from one small company, one could easily have surmised you were referring to the world total.

Quibbling over "exceedingly rare" vs. "small number", not withstanding, you were also wrong that Geothermal plants need to be located near major urban areas. I have referenced you to numerous plants where this is not the case. I am not in my office and thus I do not have access to one of my books, which if I recall correctly lists the MW capacity of the USA (as of 2002) by fuel source and or Plant type. There are about 40 geothermal plants located in California and Nevada alone, a number which in all likelihood exceeds your original thinking, which I was first addressing.

"Quibbling over "exceedingly rare" vs. "small number", not withstanding, you were also wrong that Geothermal plants need to be located near major urban areas. I have referenced you to numerous plants where this is not the case."

And what percentage of all the urban areas of the USA does this dinky little figure represent??? 0.001%??

I'll say it ONE MORE TIME--the vast majority of potential geothermal sources are too remote from urban areas to be successsfully utilized. LOOK AT THE DAMNED MAP OF THE US. Probably 95% of the POTENTIAL (not practical) geothermal is west of the Mississippi River, while most of the population is east of the Missippi. You don't transmit electricity thousands of miles--not with current (no pun intended) transmission technology, you don't.

"I am not in my office and thus I do not have access to one of my books, which if I recall correctly lists the MW capacity of the USA (as of 2002) by fuel source and or Plant type. There are about 40 geothermal plants located in California and Nevada alone, a number which in all likelihood exceeds your original thinking, which I was first addressing."

Judging from the ones you posted, the total output of geothermal energy in your list doesn't even meet the output of two standard nuclear power plants. Of course, it's hard to tell , given your "mixed units" including either megawatts or "number of homes" (a meaningless measure).

Geothermal will NEVER provide a significant portion of the US's energy needs. Better to spend the money and energy building a breeder fission capability.

And what percentage of all the urban areas of the USA does this dinky little figure represent??? 0.001%?? I'll say it ONE MORE TIME--the vast majority of potential geothermal sources are too remote from urban areas to be successsfully utilized.

LOL. Yeah, I guess, Los Angeles, Phoenix, SLC, SF don't really count as urban areas, do they?

You also do not understand the grid system of transmission very well, do you? As far as mixing of units go, I took the data, as given. I figured a Phd. would be able to do the conversion. Guess you could not figure out that the average home uses 908 kw-hr per month either that or you were too lazy to do the math.

I have known, in my life, a number of both Phd's and MD's and it has usually been the Phd's who have been overly pompous and arrogant, not willing to admit when their logic is fallible. Real Doctors usually seem to be willing to admit that they do not really know a subject and can take information from others.

I have never said that Geothermal would be a significant part of our electrical supply, I have just always contended that you have grossly underestimated it.

"LOL. Yeah, I guess, Los Angeles, Phoenix, SLC, SF don't really count as urban areas, do they?"

So I ask once again--what percentage of the urban US do these areas constitute. Of course you are bogusly assuming that all their electricity will be provided by geothermal, aren't you.

"You also do not understand the grid system of transmission very well, do you?"

So why don't you explain it, genius boy??

"As far as mixing of units go, I took the data, as given. I figured a Phd. would be able to do the conversion. Guess you could not figure out that the average home uses 908 kw-hr per month either that or you were too lazy to do the math."

Now WHY would I bother to have the amount of electricity the "average home" uses memorized?

"I have known, in my life, a number of both Phd's and MD's and it has usually been the Phd's who have been overly pompous and arrogant, not willing to admit when their logic is fallible. Real Doctors usually seem to be willing to admit that they do not really know a subject and can take information from others."

I take ACCURATE information from others just fine. But when someone spouts bullshit, I "will" call them on it.

"I have never said that Geothermal would be a significant part of our electrical supply, I have just always contended that you have grossly underestimated it."

So, I'll ask again---what fraction of the total US energy demand does geothermal provide?? The answer is "an insignificant one".

But you keep on living in your dream world, "wishin' and hopin" for someone to make geothermal useful except in very unsual confluences of easy supply and a nearby dense population.

Nope. Just a PhD Analytical Chemist with Nuclear minor. I occasionally make noises like an engineer, though, sufficient to have 24 issued patents, with more coming, and two R&D 100 awards.

Then you should know the difference between someone proposing to violate the laws of thermodynamics, and simple matters of efficiency.

In fact, there are geothermal power systems that use even smaller temperature differences, also some of the newer geothermal power plants, that now exist, operate very efficiently using steady state energy extraction.

Professor Tester was merely pointing out that subsurface technology has advanced to the point where it may soon become practical to create, artificially, the conditions which we now use as non-depleting, geothermal, energy sources.

That said, I still think that a much more promising, near term, energy source is to build sodium cooled, fast neutron, fission reactors.

Now WHY would I bother to have the amount of electricity the "average home" uses memorized?

It has been common practice, for many years, for power companies to describe power plant capacity both in megawatts, and in hundreds of homes, when talking to the press. The common rule is that 1 megawatt of power plant capacity will reliably serve about 100 homes. I suspect that power producers like to use this number, because it is close enough, and results in math that even a newspaper reporter can, generally, handle.

---what fraction of the total US energy demand does geothermal provide??

What fraction of the total US energy demand was supplied by nuclear reactors, in 1950?

What fraction of the total US transportation demand was supplied by automobiles, in 1910?

Arguments about future practicality, based on the current state of an infant technology, are specious.

to make geothermal useful except in very unsual confluences of easy supply and a nearby dense population.

I gave links to all the numbers and data that I used, so don't try and pass this off as BS, when you simply do not know what you are talking about.

For example:

You keep saying that geothermal electricity can only be used if the geothermal plant is located near an urban area. What are you making that erroneous assumption on?

What does the source of fuel/heat have to do with the transmission of electricity to a distant location?

Answer: none. The problems of transmitting electricity are unrelated to the type of fuel used to produce the electricity. Evidence: Colstrip Power Plant, Montana, Jim Bridger PP, Wyoming, Navajo PP, Az., Springerville PP, Az., Four Corners, N.M. plus the geothermal plants I named. All are located 100's of miles from major urban areas, yet all manage to supply a portion of the countries total electrical requirements.

Now, for the last time (I hope) I will state what I have been saying all along: 1) Geothermal produces more electricity then you originally gave it credit for and 2) the location of a geothermal plant is immaterial to the possibility of supplying energy into the system (yes costs will be higher, but it poses no technological problems.)

Now, read some of the links that I have posted and educate yourself on the subject or you will just continue to look foolish.

And I am not a big advocate of geothermal electricity because it is a very expensive, I just try to place facts out for people to consider. But some are not willing to look at simple facts when they are presented to them.

"Now, for the last time (I hope) I will state what I have been saying all along: 1) Geothermal produces more electricity then you originally gave it credit for and 2) the location of a geothermal plant is immaterial to the possibility of supplying energy into the system (yes costs will be higher, but it poses no technological problems.)"

No, Mikey, I'll say no such thing. I took the time to do a little of my own homework, and found that the TOTAL INSTALLED GEOTHERMAL CAPACITY of the USA is 3000 megawattss (i.e. the equivalent of 3 "standard nuclear reactors", but that only 2000 megawatts is available. This contributes 0.2% of the US's installed electrical capacity (based on 2001 numbers) and a damned close match for my estimation based on your posting.

IOW, geothermal is just as miniscule a source of power as I thought.

"Then you should know the difference between someone proposing to violate the laws of thermodynamics, and simple matters of efficiency."

Who said anything about violating the laws of thermodynamics. I'm talking about the difficulty of drilling thousands of holes four kilometers deep to GET TO the geothermal power.

"In fact, there are geothermal power systems that use even smaller temperature differences, also some of the newer geothermal power plants, that now exist, operate very efficiently using steady state energy extraction."

Excuse me, but this is BS. Maximum thermal efficiency is determined ENTIRELY by temperature differential---the higher the differential, the higher the efficiency. There may be plants that are capable of operating on small temperature differences, but EFFICIENT they are not. You've got to be careful with how these turkeys define "efficiency". A lot of them use a "theoretical percentage of the theoretical maximum FOR THE TEMPERATURE DIFFERENCE". That way they can quote a "90% efficiency" for a process that is actually only 10% of the maximum thermal efficiency. It makes'em sound really good--until, that is, you check the actual numbers.

"Professor Tester was merely pointing out that subsurface technology has advanced to the point where it may soon become practical to create, artificially, the conditions which we now use as non-depleting, geothermal, energy sources."

And "Professor Tester" is full of it. To get TO those sources will require holes four kilometers deep. They're VERY EXPENSIVE.

"That said, I still think that a much more promising, near term, energy source is to build sodium cooled, fast neutron, fission reactors."

And THAT I can agree with. The US needs a fast-breeder fission power system.

It is easy to be "proved right, when you define the territory after making a statement. I have never disagreed that Geothermal was a small part of the total power picture. But it is a significant part of the picture, which warrants further consideration.

I did a little more research and found:

Nuclear Power capacity in Calif.: 4314 Mw
percent of total power generated: ~ 9.8%

Geothermal capacity in Calif: 2500 Mw
Percent of total power generated: 4.8%

I do fully agree that nuclear is the better way to go for clean efficient energy, but you should not be so condescending in your abrupt and often erroneous assumptions regarding geothermal.

"You are still wrong about the transmission of power over long distance, so we will call this one a draw. I also note that you did not answer any of my questions regarding your second pint. You just cannot stand it that someone proved you wrong, can you?"

Nope. You haven't proved anything. I did some homework on what the grid is, and how it works, and it is YOU who don't understand it. The grid is a mechanism for establishing redundancy, allowing load sharing, and bypassing outages. What it is NOT is a means for transmitting power an appreciable amount of power from California to Maine. The basic laws of physics preclude that---it's called "transmission losses". High voltage power cables have a resistance of about 1 ohm/mile. If the transmission voltage is 475KV, and the distance is guesstimated at 4000 miles, then the maximum current you can transmit is around 120 Amps--or about enough to power a single household.

"Nuclear Power capacity in Calif.: 4314 Mw
percent of total power generated: ~ 9.8%"

"Geothermal capacity in Calif: 2500 Mw
Percent of total power generated: 4.8%"

And the total possible developable geothermal power for California is what?? THAT is the statistic that counts.

"I do fully agree that nuclear is the better way to go for clean efficient energy, but you should not be so condescending in your abrupt and often erroneous assumptions regarding geothermal."

The only problem with your little fantasy is that I haven't been wrong on any point.

allowing load sharing, and bypassing outages. What it is NOT is a means for transmitting power an appreciable amount of power

You are getting tiresome with your weak understanding and misconceptions of what I have been saying. I never have said that the grid was a method of transmitting power across the country. I said that you do not understand how it works. Further I will say that the answer is in the sentence above, yet you do not realize it.

Here is what you said that was factually wrong:

In a very limited area, where it (electricity derived from geothermal plants) happens to be both readily accessible and near population centers,

Admittedly you did not define "near" I would define near as being within 15-200 miles. I gave you a list of power plants that are located several hundred miles from the urban areas that use "their" electricity.

The grid allows this to happen. You seem to think that if a plant in California produces electricity, then that electricity must travel the entire distance to Maine to be used in Maine. That is not the case and you are clearly wrong on that point.

Here is why:

The grid could be viewed as a charged energy field with multiple inputs and multiple outputs. Electricity is put in at any point and can be taken out at any point. The controllers who operate the grid have the ability to bring up plants, or bring down plants anywhere on the grid to balance the total power distributed.

A sudden surge in usuage, in say Denver, could cause a shortage in the grid sector covered. Thus, they could ramp up power plants in SLC, Wyoming, Kansas or other surrounding areas, to replenish this surge. This is called "load sharing" which you mentioned, but did not understand.

Power plants are paid based on their feed into the grid and are paid at various rates depending on the complexities of established agreements (the commercial agreements are not an area that I have experience).

There are also independent producers who do not tie into the grid and in those cases, then their electrical distibution is limited, but it is limited to a distnace which my not be as "near" as you seem to think.

i have been following the discussion between you guys. I was really hoping to find out some useful information about the use of geothermal, so let me see if i got this all straight:
Geothermal is a viable option
Geothermal is expensive, so will probably not be a large factor in the near future.
Geothermal may or may not be able to be used around the world
Geothermal is good as individual home pumps
What are the enviornmental reprocussions of Geothermal. If we remove the heat from the earth's core, will that make the crust hotter? Will heat radiation from the earth increase? Will we be able to pump all excess waste back into the ground? What is it that makes it so expensive? If we can use some of our oil drilling techniques and machines, then why is the expense issue.

Maximum thermal efficiency is determined ENTIRELY by temperature differential...

The way that one determines whether a power plant is practical is by looking at its ECONOMIC efficiency. This is a combination of many factors including construction cost, operating and maintenance cost, power produced, location of produced power, etc.

There are already a number of geothermal power plants which are economically efficient, though they have a high construction cost, some also have very low operating and maintenance costs, combined with a very long projected operating life.

Some very small geothermal power sources have a very low thermal efficiency, but are economically efficient, because they deliver power to a remote area and have very low operating costs.

What you are objecting to, in this article, are the very high construction costs, which you are assuming will remain prohibitively high. Professor Tester is pointing out that they have decreased greatly, in recent years, and is projecting that they will continue to do so. He may be wrong, but it's unlikely that he is a fool.

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