Will Supercapacitors Come to AI's Rescue?

https://spectrum.ieee.org/supercapacitor-2671883490

34•mfiguiere•5h ago

Comments

Animats•4h ago

Is that kind of load variation from large data centers really a problem to the power grid? There are much worse intermittent loads, such as an electric furnace or a rolling mill.

paulkrush•4h ago

Edit: It's interesting the GPU's are causing issues on the grid before they cause issues with the data center's power.

mystified5016•4h ago

Read the article.

toast0•4h ago

I suspect it's more of a problem for the data center's energy bill. My understanding is that large electric customers pay a demand charge in addition to the volumetric charge for the kWh's use at whatever rates given time of use / wholesale rates. The demand charge is based on the maximum kW used (or sometimes just the connection size) and may also have a penalty rate if the power factor is poor. Smoothing over small duration surges probably makes a lot of things nicer for the rate payer, including helping manage fluctuations from the utility.

There's probably something that could be done on the individual systems so that they don't modulate power use quite so fast, too; at some latency cost, of course. If you go all the way to the extremes, you might add a zero crossing detector and use it to time clock speed increases.

timewizard•3h ago

If you have a working thermometer you can predict when furnaces are going to run.

If you want to smooth out data centers then you need hourly pricing to force them to manage their demand into periods where excess grid capacity is not being used to serve residential loads.

hinkley•3h ago

Large customers pay not by wattage but by… I’m spacing on the word but essentially how much their power draw fucks up the sine waves for voltage and current in the power grid.

I imagine common power rail systems in hyperscaler equipment helps a bit with this, but for sure switching PSUS chop up the input voltage and smooth it out. And that leads to very strange power draws.

murderfs•3h ago

You're probably thinking of power factor, which is usually not a big deal for datacenters. All of your power supplies are going to have active PFC, and anything behind a double conversion UPS is going to get PFC from the UPS. The biggest contributors are probably going to be the fans in the air conditioning units.

Animats•2h ago

This isn't about power factor. That's a current vs. voltage thing within one cycle. It's about demand side ramp rate - how fast load can go up and down.

Ramp rate has been a generation side thing for a century. Every morning, load increases from the pre-dawn low, and which generators can ramp up output at what speed matters. Ramp rate is usually measured in megawatts/minute. Big thermal plants, atomic and coal, have the lowest ramp rates, a few percent per minute.

Ramp rate demand side, though, is a new thing. There are discussions about it [1] but it's not currently something that's a parameter in electric energy bills.

[1] https://www.aceee.org/files/proceedings/2012/data/papers/019...

quickthrowman•1h ago

You’re thinking of power factor. My utility will force companies to use power factor correction equipment (a capacitor bank) if their power factor is too low.

The data center issue is not related to power factor.

oakwhiz•3h ago

There is often a demand flux surcharge as well. Not just demand but delta in demand over some time period.

changoplatanero•4h ago

Yes its a problem for the grid and the power companies don't allow large clusters to oscillate their power like this. The solution that AI have to do during their training big runs is to fill in the idle time on the GPUs with dummy operations to keep the power load constant. Having capacitors would be able to save on power usage.

nancyminusone•3h ago

Inb4 a startup is created to sell power load idle cycle compute time in AI training data centers.

mystified5016•4h ago

Those loads aren't nearly as intermittent. Your furnace likely runs for tens of minutes at a time. These datacenters are looking at second-to-second loads.

Drawing high intermittent loads at high frequency likely makes the utility upset and leads to over-building supply to the customer to cope with peak load. If you can shave down those peaks, you can use a smaller(cheaper) supply connection. A smoother load will also make the utility happy.

Remember that electricity generation cannot ramp up and down quickly. Big transient loads can cause a lot of problems through the whole network.

paulkrush•4h ago

"Thousands of GPUs all linked together turning on and off at the same time." So supercapacitors allow for simpler software?, reduced latency? at a low cost?

mjevans•4h ago

They service 'spot demand moderation' as an extension of UPS and power smoothing. In this case it's flattening out spikes to smooth slopes.

sonium•4h ago

Or you simply use the pytorch.powerplant_no_blow_up operator [1]

[1] https://www.youtube.com/watch?v=vXsT6lBf0X4

janalsncm•3h ago

Pretty much. From the article:

> Another solution is dummy calculations, which run while there are no spikes, to smooth out demand.

metaphor•1h ago

Paraphrasing this[1]?

[1] https://github.com/pytorch/pytorch/pull/132936/files#diff-98...

0cf8612b2e1e•4h ago

  One solution is to rely on backup power supplies and batteries to charge and discharge, providing extra power quickly. However, much like a phone battery degrades after multiple recharge cycles, lithium-ion batteries degrade quickly when charging and discharging at this high rate.

Is this really a problem for an industrial installation? I would imagine that a properly sized facility would have adequate cooling + capacity to only run the batteries within optimal spec. Solar plants are already charging/discharging their batteries daily.

jeffbee•3h ago

In addition to what you said, nothing is forcing or even encouraging anyone to use lithium-ion batteries in fixed service, such as a rack full of computers.

pixl97•3h ago

Eh, I think part of the problem here is the speed of load switching. From the article it looks like the loads could generate dozens to hundreds of demand spikes per minute. With most battery operated loads that I've ever messed with we're not switching loads like that. It's typically 'oh a fault, switch to battery' then some time later you check the power circuit to see if it's up and switch back.

This looks a whole lot more like high frequency load smoothing. Really it seems to me like a continuation of a motherboard. Even if you have a battery backup on your PC you still have capacitors on the board for voltage fluctuations.

lstodd•3h ago

in a properly designed install you can actually use the compressors and fans for smoothing load spikes. won't be much, but why not.

edit: otherwise I'm not getting what the entire article is about. it's as contrary to what I know about datacenter design as it can get.

it's.. just wrong.

touisteur•2h ago

I'm thinking of sequences of 'put the sharded dataset through the ten thousand 2kW GPUs, then wait on network - all-reduce - then spike again - a mostly-synchronous all-on/all-off loop. Watching how quick they get to boost-frequency I can see where the worries come from.

lstodd•2h ago

does anyone actually do those kind of loads over entire dcs?

because if so, I have some nice east-european guys to teach them proper load-balancing.

0cf8612b2e1e•1h ago

Wouldn’t that situation arise when a company is training their top end model? Facebook/Google/DeepSeek probably trained on thousands of collocated GPUs. The bigger the cluster, the bigger the sync delays between batches as the model data gets shunted back and forth.

lstodd•20m ago

basically it's a load-spreading problem. this can be mitigated entirely by control plane alone. unless you think they really do a cluster-per-datacenter and in that case, I cannot believe the DC in question were not designed for peak and transient loads both in AC and power supply. Besides it would be stupud.

lawlessone•3h ago

No.

eikenberry•3h ago

https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headline...

amelius•3h ago

Maybe a superconducting superinductor would be a better fit.

lstodd•3h ago

that would be a blackhole bomb.

janalsncm•3h ago

I am curious about what the load curves look like in these clusters. If the “networking gap” is long enough you might just be able to have a secondary workload that trains intermittently.

Slightly related, you can actually hear this effect depending on your GPU. It’s called coil whine. When your GPU is doing calculations, it draws more power and whines. Depending on your training setup, you can hear when it’s working. In other words, you want it whining all the time.

touisteur•2h ago

You might need more memory for this secondary training workload. But yeah, donating/selling the 'network' time for high-intensity, low memory footprint workloads (thinking number crunching, monte-carlo stuff, maybe brute-force through a series of problems...) might end up making sense.