Another FUSION thread...

S

Sarkus

Hippomonstrosesquippedalo phobe
Valued Senior Member
Well, seems that fusion power has inched a step closer... a Q of 1.54 has been reported by NIF (National Ignition Facillity), according to the news (e.g. here.

It's certainly an achievement - a Q > 1 means that it produces more energy than it uses from the ignition system. In this case roughly 2 MJ in produced roughly 3 MJ out.

Sounds impressive... and it is certainly a step forward (with previous best being c.0.7, I believe). BUT... and it's a big BUT... this is not the full picture.
This Q figure is known as the Q-scientific. It only takes into account the actual energy utilised within the ignition process, not all the waste energy due to engineering inefficiencies. To be of commercial viability (ignoring cost) it needs to produce more energy out than ALL the energy input into the system. This is known as Q-engineering, and Q-engineering will need to be in excess of 1. Ideally much higher.

Now, the reported Q of 1.54 was Q-scientific. An achievement for sure, but it's still far from commercially viable. The NIF reactor utilises laser tech from the 1980s, which unfortunately has an efficiency of c.1%. So in terms of Q-engineering we're at c.0.01 or so. I.e. it still requires c.100MJ of total energy in the system to produce c.1MJ output from the fusion. And that's possibly before all the other inefficiencies in the system beyond just the lasers.

More modern lasers are apparently c.20% efficient, so there's certainly some scope for improvement, and it's thought/hoped that the larger the reaction the far more efficient it actually becomes.

So it's a step in the right direction... and who knows, maybe Fusion is now only... what? 20 years (and many more billions/trillions in investment) away? ;)
 
Sarkus said:
This Q figure is known as the Q-scientific. It only takes into account the actual energy utilised within the ignition process, not all the waste energy due to engineering inefficiencies.
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In addition, that is HEAT energy out. Useful electrical energy is about 30-40% of that.
 
billvon said:
In addition, that is HEAT energy out. Useful electrical energy is about 30-40% of that.
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Yup. Possibly not even that, but I'd just be guessing.

It'd be good if journalists and media outlets could be a bit more transparent on such things, especially the mass media that is focussed on Joe Public, as opposed to the trade/scientific media who might be more au fait with the nuances. I mean, when they start going on about how they were "producing more energy from a fusion experiment than was put in" it would suggest to the majority that they are referring to all the energy put in to the entire thing - i.e. how much the whole shebang is drawing from the grid, so to speak. They don't speak anywhere how this is true only in a rather limited sense, when you only consider a certain aspect of the whole setup, and that we are far from it being what Joe Public would consider as "breakeven".

Ah, well. 'Tis good news, though. Progress is better than nothing.
 
Sarkus said:
Well, seems that fusion power has inched a step closer... a Q of 1.54 has been reported by NIF (National Ignition Facillity), according to the news (e.g. here.

It's certainly an achievement - a Q > 1 means that it produces more energy than it uses from the ignition system. In this case roughly 2 MJ in produced roughly 3 MJ out.

Sounds impressive... and it is certainly a step forward (with previous best being c.0.7, I believe). BUT... and it's a big BUT... this is not the full picture.
This Q figure is known as the Q-scientific. It only takes into account the actual energy utilised within the ignition process, not all the waste energy due to engineering inefficiencies. To be of commercial viability (ignoring cost) it needs to produce more energy out than ALL the energy input into the system. This is known as Q-engineering, and Q-engineering will need to be in excess of 1. Ideally much higher.

Now, the reported Q of 1.54 was Q-scientific. An achievement for sure, but it's still far from commercially viable. The NIF reactor utilises laser tech from the 1980s, which unfortunately has an efficiency of c.1%. So in terms of Q-engineering we're at c.0.01 or so. I.e. it still requires c.100MJ of total energy in the system to produce c.1MJ output from the fusion. And that's possibly before all the other inefficiencies in the system beyond just the lasers.

More modern lasers are apparently c.20% efficient, so there's certainly some scope for improvement, and it's thought/hoped that the larger the reaction the far more efficient it actually becomes.

So it's a step in the right direction... and who knows, maybe Fusion is now only... what? 20 years (and many more billions/trillions in investment) away? ;)
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My sentiments entirely, Doctor. Rather a lot of hype, considering the monstrous engineering challenges of turning this concept into a commercial power station, none of which have yet been addressed.

I think it must be still 30 years away. The tokamak approach is almost as far from reality, but that design looks a bit easier to envisage turning into a commercial reactor.
 
exchemist said:
My sentiments entirely, Doctor. Rather a lot of hype, considering the monstrous engineering challenges of turning this concept into a commercial power station, none of which have yet been addressed.
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This piece is quite good: not a lot of jargon but sets out the hurdles, at least of the route this inertial fusion needs to take.

I think it must be still 30 years away. The tokamak approach is almost as far from reality, but that design looks a bit easier to envisage turning into a commercial reactor.
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I'd say 50 to 100 for the NIF approach. It seems to take 10 years just to build the next iteration of reactor, and there'll need to be several more, I think. If ITER can achieve the 10-fold increase in thermal power as is hoped, then I think that will be the death-knell to the inertial fusion approach as anything other than a curious side-project; funding will gradually dry up for it as they put the full weight behind the magnetic confinement approach. If ITER does achieve it then maybe we're 40-50 years away, which I still think is optimistic. But I'm that sort of guy! (Really just wishful thinking in that I'd like to see it happen before I shuffle off this mortal coil ;))
 
Sarkus said:
This piece is quite good: not a lot of jargon but sets out the hurdles, at least of the route this inertial fusion needs to take.

I'd say 50 to 100 for the NIF approach. It seems to take 10 years just to build the next iteration of reactor, and there'll need to be several more, I think. If ITER can achieve the 10-fold increase in thermal power as is hoped, then I think that will be the death-knell to the inertial fusion approach as anything other than a curious side-project; funding will gradually dry up for it as they put the full weight behind the magnetic confinement approach. If ITER does achieve it then maybe we're 40-50 years away, which I still think is optimistic. But I'm that sort of guy! (Really just wishful thinking in that I'd like to see it happen before I shuffle off this mortal coil ;))
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Well I'm pushing 70, so it's not going to be in my lifetime, but for the sake of my son I hope it eventually succeeds. One of these two technologies is going to be Betamax and one will be VHS. In principle, the tokamak approach is more betamax, is it seems technically far more elegant than ICF. As the Betamax saga showed us, engineering and commercial muscle can have as much to do with the eventual outcome as technical elegance.
 
ITER
In for a penny
In for a pound?

.................................. what if
the tokamak design is fundamentally flawed?
 
James R said:
It isn't. It has been tested. It works.
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A different definition of 'works' than I would use. Being sufficient to induce some fusion is a milestone achievement but is still a lot of miles short of 'working fusion power plant'.

If it is this hard to do at all, doing it reliably and cost effectively - even leaving aside the R&D costs, which are primarily borne by taxpayers - will be a remarkable achievement.
 
Ken Fabian said:
A different definition of 'works' than I would use. Being sufficient to induce some fusion is a milestone achievement but is still a lot of miles short of 'working fusion power plant'.

If it is this hard to do at all, doing it reliably and cost effectively - even leaving aside the R&D costs, which are primarily borne by taxpayers - will be a remarkable achievement.
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Indeed. However I don't believe any of the methods of achieving fusion has addressed in practical terms the capture of the energy released and its conversion into electricity. So they are all at the same stage from that point of view.

There seem to be major challenges there. There has to be some kind of shield around the fusion chamber that can absorb the particles emitted and convert their energy to heat and then a means of running some fluid through the shield to transport the heat to a steam generator, so that a turbine can be run. The shield itself captures fast neutrons and α-particles. The former process apparently generates tritium for use in further fusion. However this will presumably mean periodic replacement of the shielding so it can be extracted. A huge number of engineering imponderables, it would seem. There's a description of some of this here:

The D-T fusion process produces a 3.5 MeV alpha particle and a 14.1 MeV energetic neutron, with the later to be trapped in a lithium-containing blanket, surrounding the core plasma. The reaction of neutron with Li produces tritium (which was earlier consumed in D-T fusion) and the energy deposited by neutron creates heat that is used to heat the primary coolant, which is used to produce steam to run a steam-turbine. Different types of coolants have been commonly proposed to be used in different concepts of breeding blankets. Among them: Helium cooled Lead-Lithium (HCLL), Water cooled Lead Lithium (WCLL), Helium cooled Pebble-bed (HCPB) and Dual Coolant Lead-Lithium (DCLL) breeding blankets are some of the options for the future DEMO reactor. Many of these concepts are also planned to be tested in ITER, thereby creating a comparison of various concepts. Interestingly, such concepts have some kind of parallel in that the Fast breeder test reactors use liquid-metal, Gas
cooled reactors plan to use gas (like He, CO2, etc.).
Peculiar geometry of the tokamak-based reactors, constraints posed by nuclear radiation and space available for pipe routing leads to very challenging engineering-constraints. There could be several configurations which need to be systematically examined in future. The paper presents preliminary calculations for power extraction (starting from the blanket up to the steam-generator) considering Helium-cooled blanket system. There are special constraints on configuration of piping and building design. These arise from the fact that the machine itself can be imagined to be in the form of ‘nested toroidal layers’ of progressively increasing radius (the vacuum vessel, superconducting Magnets, Thermal Shield, Cryostat, Containment Building etc. in increasing sequence).

From: https://nucleus.iaea.org/sites/fusi...s/FEC 2018/fec2018-preprints/preprint0688.pdf
 
The money would be better spent on further research and development of solar, wind, non-dam hydro, geothermal and tidal power as well as storage and transmission options.
 
Wizard of Whatever said:
The money would be better spent on further research and development of solar, wind, non-dam hydro, geothermal and tidal power as well as storage and transmission options.
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My personal view is most of these are already commercially viable so the R&D is funded adequately by industry.

However what I would like to see is more R&D on improving the efficiency of electrolysis of water. Hydrogen is key to decarbonising a number of applications. Examples are reduction of iron ore in steelmaking, fuel for ships, for instance in the form of ammonia, and possibly fuel for heavy goods vehicles, for which batteries are too heavy and bulky to be practical. There is little work on this commercially because hydrogen produced by electrolysis seems to be double the cost of "grey" or "blue" hydrogen derived from fossil fuel (methane, chiefly), both of which end up generating CO2 as a byproduct.
 
The only potential draw back with water electrolysis is that where it occurs, excess oxygen is produced, and where it is used excess water vapor is produced. Saying this, H from methane still produces carbon dioxide which will add to global warming.
Electrolysis cost would go down through economies of scale.
Considering all this it would be better to use electrolyzed H in many application/
 
Wizard of Whatever said:
The only potential draw back with water electrolysis is that where it occurs, excess oxygen is produced, and where it is used excess water vapor is produced.
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Not quite the only. Whilst Hydrogen (made without emissions) displacing higher emitting industrial processes reduces global warming potential, leaked Hydrogen (increased atmospheric concentration) adds to global warming, indirectly, by affecting persistence of atmospheric methane and slowing the breakdown to CO2 and water vapor. Overall less global warming by doing so but not zero.

Direct additions of water vapor don't look problematic - power plant (and other) cooling towers already make lots of it. Agricultural irrigation adds lots more over vastly larger areas. Not sure of how much each adds but those 'direct' additions look small compared to natural water cycle and they don't persist in the atmosphere.

A warming atmosphere itself has resulted in overall increase in atmospheric water vapor content - from warmer air taking up more water vapor; this does persist and is a key component of enhanced greenhouse effect; without that the impacts of CO2 would be smaller.

Might have to check the numbers but I suspect that the warming of atmosphere induces greater increase in water vapor than any direct 'emissions' can add. It both makes more intense rainfalls where conditions for rain occur - the air has more water vapor in it - and less rainfall in more arid conditions - the air needs to have more water vapor in it in order to saturate and have precipitation.
 
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