I guess it'd only work in places where the locals don't use AC. Otherwise it'd be a killer to run in the summer, and so you'd have capital goods rotting in a persons basement half the year.
If the user has AC for the summer, then running the AC in reverse for the winter will provide the homeowner with far more heating per joule than running a computer.
So the issue boils down to, there's not enough people living in places cold enough to make it worthwhile.
Of course, Id argue AI data centers aren't worth it full stop.
How is DC better than a three phase delta 800Vrms, at 400Hz?
- Three conductors vs two, but they can be the next gauge up since the current flows on three conductors
- no significant skin effect at 400Hz -> use speaker wire, lol.
- large voltage/current DC brakers are.. gnarly, and expensive. DC does not like to stop flowing
- The 400Hz distribution industry is massive; the entire aerospace industry runs on it. No need for niche or custom parts.
- 3 phase @ 400Hz is x6 = 2.4kHz. Six diodes will rectify it with almost no relevant amount of ripple (Vmin is 87% of Vmax) and very small caps will smooth it.
As an aside, with three (or more) phase you can use multi-tap transformers and get an arbitrary number of poles. 7 phases at 400Hz -> 5.6kHz. Your PSU is now 14 diodes and a ceramic cap.
- you still get to use step up/down transformers, but at 400Hz they're very small.
- merging power sources is a lot easier (but for the phase angle)
- DC-DC converters are great, but you're not going to beat a transformer in efficiency or reliability
"now run that unshielded wire 50 meters past racks of GPUs and enjoy your EMI"
Multipole expansion scales faster than r^2.
Also, im not in the field (clearly) but GPUs cant handle 2.4 kHz? The quarter wavelength is 30km.
"nothing in that catalog is rated for 100kW–1MW rack loads at 800Vrms"
Current wise, the catalog covers this track just fine. As to the voltages, well that's the whole point of AC! The voltage you need is but a few loops of wire away.
"you still need an inverter-based UPS upstream, which is the exact conversion stage DC eliminates"
So keep it? To clarify, this is the "we're too good for plebeian power, so we'll transform it AC->DC->AC", right?
"SiC solid-state DC breakers are shipping today from every major vendor"
Of course they do. They're also pricey, have limited current capability (both capital costs and therefore irrelevant when the industry is awash with GCC money) and lower conduction, and therefore higher heat.
They're really nice though.
"wide-bandgap converters are at 95%+ with no moving parts"
transformers have no moving parts. Loaded they can do 97%+ efficiency, or 2MW of heat eliminated on a 100MW center.
An advanced AI rack might use 100kW = 800V 125A, requiring gauge 2, quarter inch diameter---this isn't your lol speaker wire. Actually, I apologize, I realized I may be talking to a serious audiophile, didn't mean to disrespect your Monster cables.
The skin depth by the way is sqrt(2 1.7e-8 ohm m / (2 pi 400Hz mu0))=~3mm for copper---OK for single rack, but starts to be significant for the type of bus bars that an aisle of racks might want.
As for efficiency, both 400Hz transformers AND fancy DC-DC converters are around 95% efficient, except that AC requires electronics to rectify it to DC, losing another few percent, so the slight advantage goes to DC, actually.
As for merging power, remember that DC DC converter uses an internal AC stage, so it's the same---you can have multiple primary windings, just like for plain AC.
> I realized I may be talking to a serious audiophile, didn't mean to disrespect your Monster cables.
I am a recovering audiophool.
I do own a pair of 2m long Monster Cable speaker cables (with locking gold plated banana plugs). I am fairly certain I've used welders with smaller cables.
(In my defence, I bought those as a teenager in the late 80s. I am not so easily marketed to with snake oil these days. I hope.)
(On the other hand, I really like the idea of a reliably stable plus and minus 70V or maybe 100V DC power supply to my house. That'd make audio power amplifiers much easier and lighter...)
>- no significant skin effect at 400Hz -> use speaker wire, lol.
What are you talking about? There's a very significant skin effect at 400Hz. Skin effect goes up with frequency. These datacenters use copper busbars, not cable, so skin effect is an important consideration.
At 100 000 A for a 100 MW data center at 1000 V, speaker wire is a joke.
You obviously need at least a dozen stands in parallel!!
Clearly skin effect scales with frequency but, 400 Hz is still low, only 2.5x lines frequency (the scale is by the root); so the skin depth is 3mm. 3mm on each side makes for a pretty hefty rectangular cross-section.
If you could get that 100,000Amps flowing through your speaker wire, the vaporised copper and the plasma channel would probably keep your 100MW flowing, at least until your building caught fire.
This would be the funniest thing to do. 100K Amps is doable, the question is for how long. That would be one very impressive bank of capacitors. And to turn a 00 into plasma would have some spectacular side effects, such as raining molten copper across a sizeable area. Just your reading glasses would indeed not be enough, there probably isn't any PPE that I would consider entirely safe other than sufficient distance from ground zero. But now I'm really curious. I have a spot welder that will do bursts of 5KA and that will happily throw the breaker every so many welds. 100KA sustained will be a fair engineering challenge.
Ah, that lego project... that was one I always wondered if I should have industrialized it but sourcing enough lego was a real problem.
Holy crap. That's a whole series of bad ideas extremely well executed. That guy probably has never seen what a lead acid battery can do when it explodes. He keeps hiding away from the hot metal but in the path of ~half of those batteries. Ignorance is bliss.
This really shouldn't surprise anyone. Iran graduates as many engineers as the US (70% women), but few of them are working on front-end A/B optimization of some boutique dating site.
And, having taken grad classes with folks graduated from Iranian universities, their training is excellent. The Persian kids were always at the top of their class.
EDIT: for the record the class I merely audited was graduate level (rational) mechanics - the class par excellence if you're going to build a hypersonic.
Some observations:
Half the class was Chinese, the academically better half was Persian.
I was the only Westerner (albeit also foreigner)
The girls were wearing veils.
According to the professor, the best mecanist (?) of the 20th century, Clifford Truesdelle, was an American
To be fair, a golf ball's trajectory is hardly ballistic given its relatively large surface to volume ratio. Never-mind the dimples are there to cause a turbulent boundary layer to lower drag.
You don't need a full model of every atomic interaction because all of those chaotic interactions end up averaging out. Given enough coin flips you will end up on a 50/50 split even if the individual flips are unpredictable. Given enough atomic interactions the heat will transfer in the same way every time.
The problem is both highly complex, but fairly easy to model. Engineers have been doing this for over a century.
Of all the cooling modes identified by the author, one will dominate. And it is almost certainly going to have an exponential relationship with time.
Once this mode decays below the next fastest will this new fastest mode will dominate.
All the LLM has to do, then, is give a reasonable estimate for the Q for:
$T = To exp(-Qt)$
This is not too hard to fit if your training set has the internet within itself.
I would have been more interested to see the equations than the plots, but I would have been most interested to see the plots in log space. There, each cooling mode is a straight line.
The data collected, btw, appears to have at least two exponential modes within it.
[The author did not list the temperature dependance of heat capacity, which for pure water is fairly constant]
I was even going to point out how ironic it is that the mans first name and last name fit together so well.
In my defense I only got as far as idraulico and missed the "Mamma mia, they're super!"
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