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.
That’s the most common proposal for MHD generators - once it goes thru the MHD proper you use the waste heat to drive a conventional powerplant. Unfortunately MHD requires the production of plasma to be effective, and plasma just does not like to exist, so the engineering practicalities make it… unlikely to ever be even remotely viable outside of incredibly niche applications (although non-plasma MHD has been studied, and I believe there are even some human trials, to power implants in the body like pacemakers and I remember reading about nervous-interface devices in mice that used arterial MHD on to generate the microcurrent needed)
ooo, i’m trying to keep up on Deep Brain Stimulation research (i want one for reasons. they aren’t doing what i want yet, but in about 5 years they should be there) and that sounds like related research
I’ll admit I’ve been out of the field for a couple years so my information is going to be outdated, but I believe the issue with using MHD for continuous stimulation is that it generates tiny amounts of power - enough to trickle-charge a pacemaker, but not enough to keep tickling the brainstem with the frequency needed in DBS. Hopefully there have been/will be improvements to the tech that I am unaware of!
huh, so you wouldn’t have to plug in and recharge your pace?
I think the idea was to provide a redundant method of charging in case you’re unable or forget to recharge it externally. But ideally yes, it would be entirely internally powered so you wouldn’t be tethered to the grid.
edit:
A more promising approach is this which is, somewhat unglamorously, just a small turbine implanted into the heart that is spun by bloodflow. oh, no, this is a different study than the one I was thinking of! This uses a flexible generator that generates power from the deformation of the Vena Cava. Fascinating, I’ll have to dig thru it.
now that is a novel use of piezoelectricity. whoever thought of that needs many sloppy kisses from many cats
Yeah. Unfortunately even rechargeable pacemakers are extremely rare - almost all of them just expect that you’ll have to replace the battery every several years (I think the average is 5?), which in the long run isn’t terrible but still. Rechargeable batteries self-discharge far too much and as a result require quite frequent recharging so are far from ideal for implantation, although not having to undergo regular surgery to replace the battery is obviously a highly desirable outcome. The idea with internal power generation is to bridge the gap between the two and allow a person to go for far longer without the need for invasive surgery (there’s a whole sidebar here about rechargeable battery chemistry not being ideal for implantation) but without the drawbacks inherent to rechargeable batteries.
our experience was 7, but that was probably more because it was powering a DBS and it was time to implant a probe on the other side of the brain.
Jesus Christ, I imagined some kind of Matrix scenario when you said human trials.
Worry not, the implanted power systems I know of generate at peak a few nanowatts. Enough to tricklecharge an extremely low power device or run some very very very efficient digital hardware, but no way you’re harvesting that power for anything more useful. It’d be far more practical just to have the humans chained to bicycle generators…