Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Firstly I can say that I would love us to come up with a sustainable fusion solution. However with the latest estimates being 2050 at the earliest for an effective fusion solution and the planets energy needs growing by the year should we not be looking at alternatives?

I understand that in the EU alone we are spending billions of Euro's on an experimental fusion reactor.

We sit on top of a thin crust which is in turn on top of a mantle with abundant heat. Should we not be investing serious money into tapping into this heat source as a long term, sustainable solution to the planet's energy needs?

How far could we get if the money used for fusion was diverted to geothermal drilling and research?

share|improve this question
    
Some of my 2 cents: A good answer for this question should include the fact that the Earth's core produces 30 TW of power sustainably versus the 15 TW needed to power society. Temperature is a function of depth, so assumption of drilling tech limits max theoretical thermal efficiency, so assumptions about technology may limit the sustainable geothermal power to less that we use now. Or you suggest using it non-sustainably like a fossil fuel. Your choice. –  AlanSE Feb 23 '12 at 15:21
    
@Zassounotsukushi: This is not needed for a good answer, because the "unsustainable" use of geothermal energy is only unsustainable to the extent that it cools the entire Earth! The time scale for us to do that from even the most non-sustainable exploitation is measured in geological time. –  Ron Maimon Feb 23 '12 at 15:32
2  
In my opinion, the question is a political one, not a physical one. An energy portfolio, just like an investment one, is strongest when it is diversified. Scientific breakthroughs, just like the stock market, are hard to predict. –  AdamRedwine Feb 23 '12 at 16:08
    
@RonMaimon Point granted in the sense that fossil fuels, geothermal, and nuclear power are all unsustainable. Physics SE has covered this exact point before, and we have 10,000s of years to deplete the heat from the mantle. But depleting the heat from the mantle isn't the end point. Depleting heat from the reachable layers of the crust is the end point. Not even that. You decrease temperature (and efficiency) with use. You would need full simulation to see the real sustainability of it, and even the unsustainable use is likely to be only slightly better than fossil fuels. –  AlanSE Feb 23 '12 at 16:10
    
@Zassounotsukushi: The mantle is connected to the core--- you can't deplete the heat from the mantle only. I don't understand your calculation--- it should be in the million years range. –  Ron Maimon Feb 23 '12 at 16:28
show 1 more comment

closed as off topic by Qmechanic, David Z Feb 23 '12 at 17:15

Questions on Physics Stack Exchange are expected to relate to physics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

4 Answers

You can't directly compare investment in geothermal power and fusion because they're at completely different stages of development. We know how to use geothermal power; after all it's already used in many parts of the world. The problem is that unless you live conveniently near a volcano it's (currently) more expensive than using fossil fuels. Since the engineering issues are well understood, it's not obvious how more investment in research will make it significantly cheaper.

By contrast, no-one has managed to get a fusion reactor to produce more power than it consumes, or at least not for longer than a few moments, and no-one knows whether it will ever be commercially viable. But if it can be made to work its potential is vastly greater than geothermal energy. Unless we do the research we'll never know if fusion will work.

share|improve this answer
    
I don't agree with you on this. I think Geothermal power is very much in its infancy. It is not sexy hence why it gets no investment, but surely if we could drill effectively down into the Mantle the power would be limitless? I say we should spend the money being spent on fusion into drilling techniques / research. Not very exciting I grant you, but could return our investment a lot sooner... –  Matt Luckham Feb 23 '12 at 16:04
1  
As far as I know no-one has advocated drilling into the mantle to extract geothermal power. Not even research drilling has got that far; in fact it hasn't got close. The deepest drill ever, en.wikipedia.org/wiki/Kola_Superdeep_Borehole, got only a third of the way. Being able to drill into the mantle is even further away than fusion power. –  John Rennie Feb 23 '12 at 16:18
add comment

a) cost of ITER

Based on the European evaluation, we can estimate the cost of ITER construction for the seven Members at approximately EUR 13 billion, if built in Europe

ITER is financed by seven Members: China, the European Union (plus Switzerland, as a member of EURATOM), India, Japan, Korea, Russia and the United States. In all, 34 countries are sharing the cost of the ITER project.

So it is not the EU alone that is spending the millions.

Contrast the 13 billion euro to how much an aircraft carrier costs: the US by itself built 10 at a cost of 4.5 billion dollars each, total 45 billion..

So the expense of researching what will be practically a free energy machine of 13 billion shared by 34 countries should be put into perspective.

Now the cost of geothermal wells is documented, from a simple search one can have an order of magnitude estimate for the cost of single deep wells, down to 10km. Each well is about 10 to 20 million dollars. The 15 billion of ITER could drill order of magnitude 1000 wells.

That would not cover needs in gigawatts, imo, which are the world needs.

According to studies, an economically competitive geothermal power plant can cost as low as $3400 per kilowatt installed

Geothermal is an interesting parallel source of power, where ever it can be extracted, but cannot beat fusion.

share|improve this answer
1  
You are not comparing apples with apples. The ITER 13 billion will produce 0 watts of commercial power. So, lets use the 13 billion to research drilling technology only - not very sexy, but could provide a breakthrough to make geothermal workable? –  Matt Luckham Feb 23 '12 at 16:00
    
There are some research articles on laser earth boring? Could this be the way forward? –  Matt Luckham Feb 23 '12 at 16:06
1  
@MattLuckham The technology of well drilling is advanced and detailed in the links I gave.One does not need research on that.I would expect laser technology to be more expensive than standard technology. –  anna v Feb 23 '12 at 17:01
1  
Anna - as we can only drill a fraction in the earths crust at present I would say some research may be useful. I think there are many precedents of scientists thinking we cannot learn anything more in an area only to be proven wrong. If we can put a man on the moon then surely we can drill a hole 30 miles deep? –  Matt Luckham Feb 23 '12 at 18:01
1  
@Matt read a bit the link about drilling and its difficulties. I would not call research something that is engineering. –  anna v Feb 23 '12 at 19:59
add comment

I don't think its time to scrap the whole idea, but definitely it is time to devote more resources to alternative approaches. Out of the top of my mind there are two non-mainstream approaches worth pursuing:

Focus fusion: or as some like to call it, 'spark-plug fusion' because its basically huge spark plugs generating strong magnetic fields during the corona discharge period, they also expect to minimise X ray emission by some clever manipulation of the magnetic field, but i don't get the fine details

Polywell fusion: this is another approach trying to keep a virtual electron anode in the center of a structure of geometrically aligned magnetic toroids that try to minimise the electron leakage rate by tweaking their circulation pattern around the toroids

share|improve this answer
1  
I hate downvoting people I agree with, but the reality is that you didn't really address the question. –  AlanSE Feb 23 '12 at 15:28
add comment

If by fusion you mean hot fusion, the kind done in Tokamaks, then yes, we should forget it. This is a terrible waste of money--- the designs are not going to produce a power plant in 2050 or 2080 or 2100, or 3000, or anytime. It was a good idea, it just didn't pan out, and the scientists involved are constantly afraid of losing their funding, something which should have happened a long time ago. The major issue is that you don't get factors of 100 in efficiency from scaling up, so if the current billion-dollar projects do not produce usable levels of power already (and they don't), scaling them up is not going to produce a realistically competitive power source.

Different ideas for hot fusion, like inertial confinement, are promising. Although they are no closer to a power-plant today, they haven't been explored as well. The only scalable fusion we have today is the H-bomb. There once was a proposal for generating fusion energy by exploding hydrogen bombs in a gigantic underground enclosure. Even considering the enormous size of the enclosure, this would probably be cheaper and easier to make work than a Tokamak. Of course, the security danger of using hydrogen bombs in day-to-day activities probably rules this idea out.

Geothermal energy is very similar to extracting the heat from an underground nuclear explosion. It is a potentially limitless source of energy, and it will not require an open-ended neverending research program.

In this context, one must always mention the great work of Pons and Fleischmann on cold fusion, which is completely separate. This is a set of different research directions and ideas, and it makes all this hot fusion nonsense moot. It is clear from Pons and Fleischmann's seminal, era-defining work, that it is possible to use atomic scale chemistry to get fusion. This is where the hot fusion money should have been diverted back in 1989, and some speculate that the prospect of losing money led the hot-fusion scientists to suppress Pons and Fleischmann's work.

share|improve this answer
2  
Ron, has anybody been able to replicate the positive results claimed by Pons & Fleischmann? –  Michael Luciuk Feb 23 '12 at 15:12
3  
Sorry to down vote , Ron, but you are off on the Pons et al cold fusion. All physicists were very excited when it broke back then and we all spent time thinking about it. The reason I stopped supporting it is that the energy output is of the order of chemical energies, energies that were spent to make the palladium crystals and are released in their experiment. There is some hope in the recent Low energy Nuclear Reactions, LENR, which they try to separate from the word "fusion". NASA recently went out of the closet on this. youtube.com/watch?v=JBlKc0TaqPs –  anna v Feb 23 '12 at 15:56
2  
I think I was thinking of some sort of recombination of oxygen and hydrogen from the electrolysis. It is too long ago. At the time a lot of people were trying to reproduce the results unsuccessfully. I think you are overestimating the importance of criticism on what by now, 20 years later, should have been a working device. I am open to the possibility of new ways of tapping energy, even this Rossi/, Defkalion thing: if it works, it works, the theory will follow.Calling it fusion is the problem for me. –  anna v Feb 24 '12 at 20:06
2  
@RonMaimon, as anna, i don't understand how after 20 years there would not be a single enterprenurial scientist which would have developed this into something easier to replicate; let me remind you that the whole "selling point" of cold fusion is that is cheap to setup, compared to the mainstream approaches. If P&F would had something, and that something were cold fusion, we should be having flying cars by now powered by our garden hoses, don't you think? –  lurscher Feb 24 '12 at 23:16
2  
not a fair comparison Ron, people was able to build simple setups back then that probed the physical concepts; there was the volta battery, the faraday cage, simple dynamos. Nothing designed with engineering concerns, just to prove that it can be physically done, and more importantly, that could be reproduced. And they did that very well. What i'm seeing is that all these experiments of cold fusion have not been able to reach the stage when their setups are reproducible enough. It reminds me a bit back on the 1994 when Potklenov claimed gravitational effects from superconductor ceramics,.. –  lurscher Jan 10 '13 at 6:54
show 8 more comments

Not the answer you're looking for? Browse other questions tagged or ask your own question.