lumpenproletariatboiling water again
FuglyDucki mean, they can run the plasma through some magnetic fields…
But it’s less efficient that boiling water.
MinnesotaGoddamwhy not do both? get both efficiencies
Well, not an engineer myself, either, but generally speaking that would greatly increase the systems complexity, which generally increases maintenance costs, down time, and the initial cost of the system.
You might be able to eke out a bit more power, but there’s more to the decision than total output and how efficient it is.
What I would imagine were a fusion-powered MHD being useful would be as a front end to fusion-based plasma propulsion. (Basically something like the VSIMR, Hall effect or whatever plasma thruster, where the fusion reaction generates both some power to create the thrust and its exhaust plasma is also the reaction mass.(I mentioned I’m not an engineer… right? Just an incorrigible nerd who likes sci-fi.)
GreenCrunchThere’s a few things (I am an engineer, though not nuclear):
1) Efficiencies don’t necessarily stack like that. For boiling water you’re dependent on kinetic energy as heat. I’m not familiar with running plasma through magnetic fields for power generation, but if you lose thermal energy, your overall efficiency may be worse.
2) In power generation, reliability is obviously extremely important, and the nuclear industry is highly risk-averse. So doing something in a known, tested way is preferable. Any downtime is extremely expensive if things break, since it may be gigawatts of power you’re not selling.
3) Big magnets and handling highly energetic plasma are both really expensive. Steam turbines and generators have existing supply chains since we use them everywhere. I think cost is a big part, since the people building power plants want to make their money back sooner, so may not want to pay millions to billions more for a few percent efficiency gain.
Reading a bit more about it, the MHD generator does indeed reduce the temperature and velocity. The Rankine cycle (steam turbines) is most efficient with a large difference between inlet and outlet temperatures, so if you have MHD first, you have a very cold inlet and the steam turbine won’t be effective.
The other way around doesn’t work either, as the steam turbine system would absorb all the heat from the plasma, making the MHD ineffective.