It seem very doubtful that we’ll have practical fusion power any time soon or necessarily ever. The technical hurdles are immense. Note that any form of fusion plant will almost certainly be using deuterium-tritium fusion. That means you need tritium sources. This also means that the internal structure will undergo constant low-level neutron bombardment which seriously reduces the lifespan of basic parts such as the electromagnets used. If we look at he form of proposed fusion that has had the most work and has the best chance of success, tokamaks, then we get to a number of other serious problems such as plasma leaks. Other forms of magnetic containment have also not solved the plasma leak problem. Forms of reactors that don’t use magnetic containment suffer from other similarly serious problems. For example, the runner up to magnetic containment is laser confinement but no one hasa good way to actually get energy out of laser confinement.
That said, I think that there are enough other potential sources of energy (nuclear fission, solar (and space based solar especially), wind, and tidal to name a few) that this won’t be an issue.
...the runner up to magnetic containment is laser confinement but no one has a good way to actually get energy out of laser confinement...
Um.. not sure what you mean. The energy out of inertial (i.e., laser) confinement is thermal. You implode and heat a ball of D-T, causing fusion, releasing heat energy, which is used to generate steam for a turbine.
Fusion has a bad rap, because the high benefits that would accrue if it were accomplished encourage wishful thinking. But that doesn’t mean it’s all wishful thinking. Lawrence Livermore has seen some encouraging results, for example.
Yeah, but a lot of that energy that is released isn’t in happy forms. D-T releases not just high energy photons but also neutrons which are carrying away a lot of the energy. So what you actually need is something that can absorb the neutrons in a safe fashion and convert that to heat. Lithium blankets are a commonly suggested solution since a lot of the time lithium will form tritium after you bombard it with neutrons (so you get more tritium as a result). There’s also the technically simpler solution of just using paraffin. But the conversion of the resulting energy into heat for steam is decidedly non-trivial.
Imagine what people must have thought in 1910 about the feasibility of getting to the Moon or generating energy by artificially splitting atoms (especially within the 20th century).
Imagine what people must have thought in 1910 about the feasibility of getting to the Moon or generating energy by artificially splitting atoms (especially within the 20th century).
Two problems with that sort of comparison: First, something like going to the Moon is a goal, not a technology. Thus, if we have other sources of power, the incentive to work out the details for fusion becomes small. Second, one shouldn’t forget how many technologies have been tried and have fallen by the wayside as not very practical or not at all practical. A good way of getting a handle on this is to read old issue of something like Scientific American from the 1950s and 1960s. Or read scifi from that time period. One of example of historical technology that never showed up on any substantial scale is nuclear powered airplanes, despite a lot of research in the 1950s about them. Similarly, nuclear thermal rockets have not been made. This isn’t because they are impossible, but because they are extremely impractical compared to other technologies. It seems likely that fusion power will fall into the same category. See this article about Project Pluto for example.
These are perfectly valid arguments and I admit that I share your skepticism concerning the economic competitiveness of the fusion technology. I admit, if I had a decision to make about buying some security, the payout of which would depend on the amount of energy produced by fusion power within 30 years, I would not hurry to place any bet.
What I lack is your apparent confidence in ruling out the technology based on the technological difficulties we face at this point in time.
I am always surprised how the opinion of so called experts diverges when it comes to estimating the feasibility and cost of different energy production options (even excluding fusion power). For example there is recent TED video where people discuss the pros and cons of nuclear power. The whole discussion boils down to the question: What are the resources we need in order to produce X amount of energy using
nuclear
wind
solar
biofuel
geothermal
power. For me, the disturbing thing was that the statements about the resource usage (e.g. area consumption, but also risks) of the different technologies were sometimes off by magnitudes.
If we lack the information to produce numbers in the same ballpark even for technologies that we have been using for decades (if not longer), then how much confidence can we have about the viability, costs, risks and competitiveness of a technology, like fusion, that we have not even started to tap.
Re: “Second, one shouldn’t forget how many technologies have been tried and have fallen by the wayside as not very practical or not at all practical. [...] It seems likely that fusion power will fall into the same category.”
Er, not to the governments that have already invested many billions of dollars in fusion research it doesn’t! They have looked into the whole issue of the chances of success.
It seem very doubtful that we’ll have practical fusion power any time soon or necessarily ever. [...] This also means that the internal structure will undergo constant low-level neutron bombardment which seriously reduces the lifespan of basic parts such as the electromagnets used.
Automatically self-repairing nanotech construction? (To suggest a point where a straightforward way of dealing with this becomes economically viable.)
You would need not only self-repairing nanotech but such technology that could withstand both large amounts of radiation as well as strong magnetic fields. Of the currently proposed major methods of nanotech I’m not aware of any that has anything resembling a chance to meet those criteria (with the disclaimer that I’m not a chemist.) If we had nanotech that was that robust it would bump up so many different technologies that fusion would look pretty unnecessary. For example the main barrier to space elevators is efficient reliable synthesis of long chains of carbon nanotubes that could be placed in a functional composite (see this NASA Institute for Advanced Concepts Report for a discussion of these and related issues). We’d almost certainly have that technology well before anything like self-repairing nanotech that stayed functional in high radiation environments. And if you have functional space elevators then you get cheap solar power because it becomes very easy to launch solar power satellites.
I’m not talking about plausible now, but plausible some day, as a reply to your “It seem very doubtful … any time soon or necessarily ever”. The sections being repaired could be offline. “Self-repair” doesn’t assume repair within volume of an existing/operating structure, it could be all cleared out and rebuilt anew, for example. That it’s done more or less automatically is the economic requirement. Any other methods of relatively cheap and fast production, assembly and recycling will work too.
Ah ok. That’s a lot more plausible. There’s still the issue that once you have cheap solar the resources it takes to make fusion power will simply cost so much more as to likely not be worth it. But if it could be substantially more efficient than straight fission then maybe it would get used for stuff not directly on Earth if/when we have large installations that aren’t the inner solar system.
Estimating feasibility using exploratory engineering is much simpler than estimating what will actually happen. I’m only arguing that this technology will almost certainly be feasible on human level in not absurdly distant future, not that it’ll ever be actually used.
It seem very doubtful that we’ll have practical fusion power any time soon or necessarily ever. The technical hurdles are immense. Note that any form of fusion plant will almost certainly be using deuterium-tritium fusion. That means you need tritium sources. This also means that the internal structure will undergo constant low-level neutron bombardment which seriously reduces the lifespan of basic parts such as the electromagnets used. If we look at he form of proposed fusion that has had the most work and has the best chance of success, tokamaks, then we get to a number of other serious problems such as plasma leaks. Other forms of magnetic containment have also not solved the plasma leak problem. Forms of reactors that don’t use magnetic containment suffer from other similarly serious problems. For example, the runner up to magnetic containment is laser confinement but no one hasa good way to actually get energy out of laser confinement.
That said, I think that there are enough other potential sources of energy (nuclear fission, solar (and space based solar especially), wind, and tidal to name a few) that this won’t be an issue.
Um.. not sure what you mean. The energy out of inertial (i.e., laser) confinement is thermal. You implode and heat a ball of D-T, causing fusion, releasing heat energy, which is used to generate steam for a turbine.
Fusion has a bad rap, because the high benefits that would accrue if it were accomplished encourage wishful thinking. But that doesn’t mean it’s all wishful thinking. Lawrence Livermore has seen some encouraging results, for example.
EDIT: for fact checking vis-a-vis LLNL.
Yeah, but a lot of that energy that is released isn’t in happy forms. D-T releases not just high energy photons but also neutrons which are carrying away a lot of the energy. So what you actually need is something that can absorb the neutrons in a safe fashion and convert that to heat. Lithium blankets are a commonly suggested solution since a lot of the time lithium will form tritium after you bombard it with neutrons (so you get more tritium as a result). There’s also the technically simpler solution of just using paraffin. But the conversion of the resulting energy into heat for steam is decidedly non-trivial.
I see, thanks.
Imagine what people must have thought in 1910 about the feasibility of getting to the Moon or generating energy by artificially splitting atoms (especially within the 20th century).
Two problems with that sort of comparison: First, something like going to the Moon is a goal, not a technology. Thus, if we have other sources of power, the incentive to work out the details for fusion becomes small. Second, one shouldn’t forget how many technologies have been tried and have fallen by the wayside as not very practical or not at all practical. A good way of getting a handle on this is to read old issue of something like Scientific American from the 1950s and 1960s. Or read scifi from that time period. One of example of historical technology that never showed up on any substantial scale is nuclear powered airplanes, despite a lot of research in the 1950s about them. Similarly, nuclear thermal rockets have not been made. This isn’t because they are impossible, but because they are extremely impractical compared to other technologies. It seems likely that fusion power will fall into the same category. See this article about Project Pluto for example.
These are perfectly valid arguments and I admit that I share your skepticism concerning the economic competitiveness of the fusion technology. I admit, if I had a decision to make about buying some security, the payout of which would depend on the amount of energy produced by fusion power within 30 years, I would not hurry to place any bet.
What I lack is your apparent confidence in ruling out the technology based on the technological difficulties we face at this point in time.
I am always surprised how the opinion of so called experts diverges when it comes to estimating the feasibility and cost of different energy production options (even excluding fusion power). For example there is recent TED video where people discuss the pros and cons of nuclear power. The whole discussion boils down to the question: What are the resources we need in order to produce X amount of energy using
nuclear
wind
solar
biofuel
geothermal
power. For me, the disturbing thing was that the statements about the resource usage (e.g. area consumption, but also risks) of the different technologies were sometimes off by magnitudes.
If we lack the information to produce numbers in the same ballpark even for technologies that we have been using for decades (if not longer), then how much confidence can we have about the viability, costs, risks and competitiveness of a technology, like fusion, that we have not even started to tap.
Ask and ye shall receive: David MacKay, Sustainable energy without the hot air. A free online book that reads like porn for LessWrong regulars.
Yes, I’ve read that (pretty good) book quite a while ago and it is also referenced in the TED talk I mentioned.
This was one of the reasons I was surprised that there is still such a huge disagreement about the figures even among experts.
Re: “Second, one shouldn’t forget how many technologies have been tried and have fallen by the wayside as not very practical or not at all practical. [...] It seems likely that fusion power will fall into the same category.”
Er, not to the governments that have already invested many billions of dollars in fusion research it doesn’t! They have looked into the whole issue of the chances of success.
Automatically self-repairing nanotech construction? (To suggest a point where a straightforward way of dealing with this becomes economically viable.)
You would need not only self-repairing nanotech but such technology that could withstand both large amounts of radiation as well as strong magnetic fields. Of the currently proposed major methods of nanotech I’m not aware of any that has anything resembling a chance to meet those criteria (with the disclaimer that I’m not a chemist.) If we had nanotech that was that robust it would bump up so many different technologies that fusion would look pretty unnecessary. For example the main barrier to space elevators is efficient reliable synthesis of long chains of carbon nanotubes that could be placed in a functional composite (see this NASA Institute for Advanced Concepts Report for a discussion of these and related issues). We’d almost certainly have that technology well before anything like self-repairing nanotech that stayed functional in high radiation environments. And if you have functional space elevators then you get cheap solar power because it becomes very easy to launch solar power satellites.
I’m not talking about plausible now, but plausible some day, as a reply to your “It seem very doubtful … any time soon or necessarily ever”. The sections being repaired could be offline. “Self-repair” doesn’t assume repair within volume of an existing/operating structure, it could be all cleared out and rebuilt anew, for example. That it’s done more or less automatically is the economic requirement. Any other methods of relatively cheap and fast production, assembly and recycling will work too.
Ah ok. That’s a lot more plausible. There’s still the issue that once you have cheap solar the resources it takes to make fusion power will simply cost so much more as to likely not be worth it. But if it could be substantially more efficient than straight fission then maybe it would get used for stuff not directly on Earth if/when we have large installations that aren’t the inner solar system.
Estimating feasibility using exploratory engineering is much simpler than estimating what will actually happen. I’m only arguing that this technology will almost certainly be feasible on human level in not absurdly distant future, not that it’ll ever be actually used.
In that case, there’s no substantial disagreement.
There don’t seem to be too many electromagnets at the NIF: https://lasers.llnl.gov/
It seems to me that the problems are relatively minor, and so that we will have fusion power—with high probabilty this century.
[Wow—LW codebase doesn’t know about https!]