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Carbon-free fusion power could be ‘on the grid in 15 years’

Snaploud

Snaploud

Admiral
Admiral
This project looks promising:

...Decades of disappointment in the field has led to the joke that fusion is the energy of the future – and always will be.

The just-over-the-horizon timeframe normally cited is 30 years, but the MIT team believe they can halve this by using new superconducting materials to produce ultra-powerful magnets, one of the main components of a fusion reactor...

...The experimental reactor is designed to produce about 100MW of heat. While it will not turn that heat into electricity, it will produce, in pulses of about 10 seconds, as much power as is used by a small city. The scientists anticipate the output would be more than twice the power used to heat the plasma, achieving the ultimate technical milestone: positive net energy from fusion...

https://www.theguardian.com/environ...on-brink-of-being-realised-say-mit-scientists
 
Still wondering about the method of conversion...

I know there are a bunch of different ideas floating around (some have been for decades) but, I keep hearing the old "boil a liquid to turn a turbine" solution and that's got a LOT of lost energy in it...
 
I assume it's a D-T fusion device so you'd still have to deal with the physical damage caused by pesky by-product neutrons. Consequent failure of the superconducting magnet coils could cause severe damage to the machine. Even with He3 fusion, you'd still get neutrons from by-product reactions. ...and, yes, efficient conversion to electricity of the heat produced would still need to be addressed.
 
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The fifteen-year figure doesn't sound "Scottied."

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StarCruiser said:
Still wondering about the method of conversion...
Click to expand...
Standard brayton cycle. That's all they've really got, mainly because for all the research done into sustaining the fusion reaction at appropriate power levels, there is very little corresponding research into magnetoplasmadynamic energy conversion, and thermo-electric conversion is inherently inefficient at those power levels. Even a combination of MHD and Brayton cycle conversion -- assuming you could even make that work, which given the containment problem you probably couldn't -- would only be at most 40% efficient for a fusion reactor. This makes commercial grade fusion that much trickier to pull off because it needs to produce FAR MORE than twice as much power than is required to start the reaction in the first place.
 
StarCruiser said:
Still wondering about the method of conversion...

I know there are a bunch of different ideas floating around (some have been for decades) but, I keep hearing the old "boil a liquid to turn a turbine" solution and that's got a LOT of lost energy in it...
Click to expand...

Yeah, the second principle of thermodynamics is not your friend in that case. It would be better to do away with heat altogether and turn it directly into electricity.
 
The Brayton Cycle is just inefficient enough to quite possibly be a killer for fusion power.

It takes a fair amount of the energy in the reaction to sustain the reaction and maintain control. They REALLY need to redirect some effort to finding a better way to convert the power.

Something similar to Solar Cells - optimized for IR instead...maybe?
 
About 80% of the energy generated during D-T fusion is carried away by the neutrons that are produced. The only currently feasible choice you have for extracting their energy is thermalisation, allow them to undergo beta decay within a moderating blanket or to be captured by the nucleus of an atom with a high cross-section such as cadmium or boron. The Brayton cycle is the only practical solution for extracting the energy at the present time. Neutrons are tricky blighters to tame.
 
Asbo Zaprudder said:
About 80% of the energy generated during D-T fusion is carried away by the neutrons that are produced. The only currently feasible choice you have for extracting their energy is thermalisation, allow them to undergo beta decay within a moderating blanket or to be captured by the nucleus of an atom with a high cross-section such as cadmium or boron. The Brayton cycle is the only practical solution for extracting the energy at the present time. Neutrons are tricky blighters to tame.
Click to expand...
And it gets worse when you consider neutron flux is next to useless in MHD conversion since they don't have a net charge and don't induce a current when they move. Really, the only way to convert the by products DIRECTLY into energy would be to use a form of fusion whose byproducts are mostly charged particles.

I think only proton-proton fusion would really be able to achieve that, or maybe DT-He3.
 
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