2 ms·
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 vol
by toast0 2y 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.
- deleted 2y ago[deleted]
- timewizard 2y agoIf 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 2y agoLarge 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 2y agoYou'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 2y agoThis 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/0193-000178.pdf https://www.aceee.org/files/proceedings/2012/data/papers/019...
- hinkley 2y agoFor factories it’s both, but if by “this” you mean the article, I agree. Bursty traffic is the problem they’re most trying to solve. It’s akin (but other side of the coin) to when NAS hardware learned to stagger drive spool up during power on to avoid brownouts. Startup current on spinning platters is ridiculous. You have to do something to buffer, and you can do it on the supply or demand side. Or for large problems, both.
- quickthrowman 2y agoYou’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 2y agoPower factor, but most power supplies have a good amount of power factor correction on them now, and datacenters can have PFC as an independent system and/or inside some types/modes of UPSes. Oddly enough the capacitive power factor of power supplies cancels out with some of the inductive loads of supporting mechanical equipment.
- oakwhiz 2y agoThere is often a demand flux surcharge as well. Not just demand but delta in demand over some time period.