Posted on 08/01/2006 11:15:01 AM PDT by aculeus
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.
Technology Review: How much geothermal energy could be harvested?
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.
TR: We do use some geothermal today, don't we?
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.
TR: How do you plan to harvest stored heat from more areas?
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.
TR: What technology do you need to open up the rock and harvest the heat?
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.
TR: You're working on new drilling technology. How does this fit in?
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.
TR: What are the advantages compared with other renewable sources of energy?
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.
TR: What are some environmental concerns with "heat mining?"
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.
TR: How fast do you think artificial geothermal systems can be developed?
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.
Copyright Technology Review 2006.
True.
Geothermal is expensive, so will probably not be a large factor in the near future.
The cost of geothermal power varies considerably, depending on location. In places where a geothermal power plant can be built relatively cheaply, it can be an economical thing to do.
Geothermal may or may not be able to be used around the world
Current geothermal power technology is only practical on a small percentage of the Earth's surface. The point of the above article, is that Professor Tester believes that the technology may soon make it practical to build geothermal power plants anywhere on Earth. This would require building artificial geothermal fields, several kilometers below the surface, something that would be tremendously expensive to do (presently), and would have been unthinkable a few years ago.
Geothermal is good as individual home pumps
These do exist and do seem to be practical for some people in some places, but are not a general solution to mankind's energy problem.
If we remove the heat from the earth's core, will that make the crust hotter?
No. Geothermal power plants don't go anywhere near the core. They simply intercept heat which has already traveled thousands of miles toward the surface, and is not quite there yet.
Will heat radiation from the earth increase?
The answer to this is a little too complicated to answer briefly, and you probably wouldn't understand a full answer, anyway. Suffice it to say that any difference would be insignificant, even if mankind's total energy needs were supplied from geothermal sources.
Will we be able to pump all excess waste back into the ground?
The only "excess waste" is hot water and gasses that come up from the geothermal field. Since only the heat is useful, it makes sense to pump the cooled materials back down to where they came from. In fact, if this is not done, the field loses efficiency, so this is how modern geothermal plants work. They sit on the surface, looking like they are doing nothing, and simply put out electricity.
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.
Drilling lots of very deep holes and installing plumbing deep underground, is very expensive to do. It also costs a lot of money for oil companies to do it, but what is required to build an "anywhere" geothermal plant is much greater than what is needed to drill oil. As technology advances, these costs decrease.
Hope this helps.
All that said, we already have the technology to build much better nuclear reactors. Modern reactors would be much cheaper to build, much cheaper (and safer to fuel), much cheaper (and safer) to operate, and much more efficient at extracting energy from available fuel sources than current reactors. They could also be used to eliminate (by burning as fuel) virtually all high level nuclear waste currently in existence.
Most of the technology to accomplish this has been well understood since the 1970s, but its use has been suppressed by the adherents of the anti-nuclear religion.
Ping me, please to energy related stuff.
Giving that as a preliminary, I would answer your questions as indicated below:
What are the environmental repercussions of Geothermal. In that process minimum, as the brine is reinjected. Possible danger from leakage of the Isobutane into the atmosphere.
If we remove the heat from the earth's core, will that make the crust hotter? I don't think you meant what you have asked. Removing heat never makes anything hotter, except the source that the heat is being transfered to, which in this case is the Isobutane. What would happen is a lower temperature brine would be re injected into the earth. If anything the earths core would be cooled. But this would be a very minimal effect.
Will heat radiation from the earth increase?
No comment.
Will we be able to pump all excess waste back into the ground? Yes unless not permitted to do so by local regulations.
What is it that makes it so expensive? Geothermal brine is very corrosive and abrasive, requiring high cost equipment.
If we can use some of our oil drilling techniques and machines, then why is the expense issue.Drilling is a capitol coast, what I refer to above is an ongoing maintenance cost and an high capitol cost.
pressure
I'll try this ONE MORE TIME. If geothermal is to be broadly useful in solving the energy problems of the United States, then either 1) its sources must be widely dispersed across the population in need of power, or 2) the power that it generates at the isolated points of availability must be transmittable to the places where it is needed.
A short perusal of any map of the potential area of availabilty shows that 1) is not the case. An examination of the physics of power transmission shows that 2) is impossible as long as the transmission is as electric power due to transmission losses. Being "attached to the grid" does ZIP to solve 2), given the size of the USA.
Because of these unchangeable facts, geothermal will never be a significant part of the solution to the United States energy needs.
The ONLY sense in which you could sell your position is an economic one--i.e. that energy is fungible, and that electricity generated by the relatively small and isolated geothermal "hot-spots" frees up other forms of energy usable in electrical generation to be used in other regions that don't possess geothermal. But "being hooked to the grid" is irrelevant in the economic sense, because what is being "transmitted" is the dollars to buy the fuel.
a) Why is the problem you speak of isolated to power produced by Geothermal?
b) Why can fossil and nuclear plants exist at remote (+300 miles) from major urban areas w/o problem?
Because all the OTHER major means of generating electricity can be sited according to the needs of the grid. Nuclear can be sited virtually anywhere (albeit less cheaply as one might be forced to use reactor-to-air cooling rather than reactor-to-water).
You can't move a geothermal site. Even solar is much better than geothermal with respect to "location, location, location".
"b) Why can fossil and nuclear plants exist at remote (+300 miles) from major urban areas w/o problem?"
You're the one fixated on +300 miles as "remote". I consider 300 miles or so to be reasonably "nearby". "Remote" is >700 miles (the length of the longest single transmssion line in the world). Why do you think I'm talking about California vs. Maine, or the region West of the Mississippi vs. the region east of the Mississippi?
The only way geothermal can contribute in a significant way is if technology develops super-conducting transmission of electricity, or if there is a shift from the "electric grid" to the "hydrogen economy" to overcome the problems of transmission losses. Fundamental physics will NOT be denied.
Geysers is 150 miles from SF.
Steamboat is 30 miles from Reno, 175 from SF.
You are all wet on this one. Bye.
I've looked at the map. I think you need to spend a bit more time doing so. Geothermal is useful in a very SMALL portion of the area of the United States, and accessible to only a tiny fraction of the population. Thus it won't ever make up a significant fraction of the total energy usage of the country--and in fact is probably not even capable of supplying the total electric needs of the area you mention.
I note you never did answer the question of what is the likely total DEVELOPABLE geothermal potential even of California. I also noted in passing through various online geothermal energy references that they can't even run the full installed capacity of "The Geysers", I assume because they were depleting the available resource.
You need not assume that. If you had been paying attention to my posts you would have seen that I said that much earlier in this thread.
But I think you only listen to what you want to listen to and tune out much of everything else.
Drill Yellowstone!! Chill the Caldera!!!
They picked a good area, imo. Of all the areas I have worked on oil wells, Nevada had the highest bottom hole temperatures (easily) at 10,000 ft. In places, on the order of 350+ degrees. (It cooked the film in the survey tools we used back then and made it difficult to keep track of hole deviation).
Here's the information YOU consistently "tune out":
http://geoheat.oit.edu/images/map/usmap.map
http://upload.wikimedia.org/wikipedia/en/thumb/9/90/USA-2000-population-density.gif/800px-USA-2000-population-density.gif
Note the location of the geothermal resources.
Now note the location of the population.
Now note that the vast majority of that population is greater than 700 miles from those geothermal resources.
I can' make it any plainer than that---geothermal energy is a typical "green boutique" project. It makes the greens "feel good" but it doesn't do much to solve environmental problems.
a) The distances to Urban areas that I mentioned in my post above and
b) There are fossil fuel plants (I have named several) which are located at distances further away from urban areas then are the geothermal fields.
Who do you think is using the 230 MW (the size of an average fossil fuels plant) from the Geysers?
Who do you think is using the 200+ MW in the Imperial valley?
By using such power locally, it FREES up more energy to be used by plants already located in major urban areas.
For being a self proclaimed Phd, I should not have to explain such simple facts.
Now I suggest we end this conversation as it has become tedious.
So they're located at distances further away--I'd be willing to bet that those fossil fuel plants are closer than 700 miles, though. But as long as the plants are within economical transmission distance, that isn't the point. The point is that the amount of available geothermal energy is trivial compared to the need for energy. I suspect that any one of those "fossil fuel" plants is on the order of 1000MWe in size. The engineering talent wasted to design the plant(s) to harvest the dinky amounts of geothermal energy would be better invested in an energy source with more viability.
"Who do you think is using the 230 MW (the size of an average fossil fuels plant) from the Geysers? Who do you think is using the 200+ MW in the Imperial valley?"
Again with the dinky numbers. This is half the output on a single nuclear plant.
"By using such power locally, it FREES up more energy to be used by plants already located in major urban areas."
Why not simply build a nuclear plant, and free up a lot MORE energy??
"For being a self proclaimed Phd, I should not have to explain such simple facts."
I understand all those "simple facts". I simply deny that they are relevant to solving the energy problem. (Oh, and btw, I'm not a "self-proclaimed PhD"--that proclaiming was done by a university).
"Now I suggest we end this conversation as it has become tedious."
Feel free.
Nukes provide 10% of the electricity in Calif. That is a dinky number. So nukes are only apart of the solution.
The total solution comes from a multitude of fuel sources including nukes, water,fossil fuels, and alternative and or renewables.
The difference is that nukes have the capacity to be the entire solution--geothermal does not. And the main reason that number is as small as it is in California is that the folks there have bought the eco-lies, hook, line, and sinker and forced the shutdown of nuke plants, instead of building more as fast as possible (which is what they SHOULD be doing).
"The total solution comes from a multitude of fuel sources including nukes, water,fossil fuels, and alternative and or renewables."
Lets see. The Greens tell us we can't build nukes (they might melt and release radiation), we can't build dams (they harm the fishies life cycle), we can't build fossil fuel plants (they cause global warming), we can't build windmills (they hurt the birdies). I'm sure they'll come up with reasons why we can't use solar or geothermal, either.
But of the sources listed, only two have the capacity to replace fossil fuel usage---nuclear fission and solar.
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