I wanted to share this opinion on Hackaday about a topic that is the usefulness of a something that has become ubiquitous relatively fast.
This techonolgyy has a lot of potential, what do you think?
I wanted to share this opinion on Hackaday about a topic that is the usefulness of a something that has become ubiquitous relatively fast.
This techonolgyy has a lot of potential, what do you think?
Meh. I hate it.
I think society should be moving towards buildings having a dedicated DC source.
International Standardize on a DC wall plug.
Each device can step it down easily/efficiently with little electronics to their own needs.
That’s pretty much the “we should all put PoE everywhere” debate, and I don’t think that’ll happen (or is a good idea) - and that’s coming from me as someone with switches providing 1.5kW of PoE power budget in the garage.
The alternative would be a shared conductor like we have now - and while that is working will in data centres doing a conductor in the required dimensions for that would be too big, and potentially dangerous, so that’ll happen even less.
No, it’s got nothing to do with power over ethernet.
It’s simply having only one high power rectifier at the breaker box.
And removing all those rectifiers from every device in the house.
We don’t need AC in the home anymore. Every device is now using DC, and any other device will still work with DC.
The only thing really left are motors, but even those are going brushless and we can chop half of the inverter out of the equation of those as well.
And every device won’t even need smart electronics for PD either.
It would also solve the North America 60Hz and EU 50Hz issue, where the AC coming in doesn’t matter. We all standardize on a DC output.
And when people want to add alternative power (Solar/Wind/etc), it’s a HELL of a lot easier to just push the DC into the existing system without having to worry about frequency matching.
Since when is it an issue?
A lot of stuff accepts both and the plugs are different anyways so why does it matter?
Btw most of the world uses 50hz not just the EU.
again, simpler and cheaper electronics for everything
Yeah, but they would be simpler but you would instead have to put powerful DC-DC converters in pretty much everything.
It sounds like a solution to a problem which isn’t a big deal. In theory it might be nice but it works fine as it is. We know very well how home AC grids work and charging that would be a mess.
powerful DC-DC
No, are you not aware how these work?
A step down DC-DC is nothing compared to a transformer rectifier or PD electronics with communication with a USB-C.
Maybe, DC wiring at home will never happen though (except in the form of POE).
It was once upon a time, in the age of olde, where switched-mode power supplies were not the norm and GaN semiconductors weren’t in the process of taking over the whole power IC market. Taking in any mains voltage/frequency and spitting out any reasonable DC voltage is no issue for those things, they simply don’t care.
It’s still going to be an issue in the future but pretty much only for resistive heaters (well, at least the voltage part) and motors with oomph.
Speaking of DC though: The EU is looking into applying HVDC not just to point-to-point connections but at a network level. Don’t expect that to hit your home in your lifetime, but if you’re an aluminium smelter it would make a lot of sense to have a direct connection to tons of DC.
I laughed and wrote out a list of things in my house using AC but I see you’re talking more theoretically. Most of the things using ac in my house are only ever plugged into one circuit, so we could leave those circuits alone. I don’t think USB C PD could handle a hairdryer though, and they aren’t always used on the same circuits (eg sometimes bathroom, sometimes bedroom)
It’s really tough to displace entrenched standards.
Lots of small kitchen appliances would be out of luck. Or how about vacuum cleaners as an example that needs a lot of power but might be plugged in for every room …. Where would I recharge batteries for my lawn care equipment?
What?
Most vaccums are brushless, where they are already converting the AC to DC internally. Your vacuums would be cheaper.
Where would I recharge batteries for my lawn care equipment?
again what? The same way? Your charger is converting AC to DC. You could skip that step.
All of these appliances would work better/cheaper with a 110VDC@15A source.
Yeah I think many of us missed that you’re proposing a full power replacement circuit, rather than USB power everywhere
One of the things you’re missing about USB and would likely lose here is that it’s “smart”. Both sides negotiate an acceptable power profile. If you only have one converter for the house I don’t think you could easily deliver many different power profiles to many points
You wouldn’t have to.
Every device instead of having an expensive PD communication device in it, would have an even cheaper PWM DC Step-down.
No communication needed.
Each device would just draw what it needs to.
_ I don’t think USB C PD could handle a hairdryer though_
Of course it wouldn’t. The idea would be get rid of USB-C and PD completely.
You’d have 110VDC@15A available for your hairdryer. Heating coils don’t care if it’s AC or DC, and the blower fan would be a brushless fan.
You’re compressors for AC or fridge would be freq drives, which are cheaper because they could drop the rectifier circuit, and highly efficient.
The only real concern about having DC in the home as standard is the safety aspect of DC doesn’t let go if you get shocked.
But that is already being worked on in general as many homes have high-voltage DC circuits from solar panels.
But different devices need different voltages. Does every outlet in my house have to have its own connection to the central rectifier? It’s a lot of re wiring.
PWM DC to DC dropping voltage to what you need is easy/cheep.
So instead of a big transformer + rectifier that each device has now, it would be a much smaller/cheaper step down at like 99.8% efficiency
This doesn’t seem better.
Well, I mean if you don’t understand power electronics I don’t see how you can make that statement.
We did. It’s called USB-C and my house has outlets with AC/USB-C combo.
You want another standard?
More importantly, standards do change. Many of us did the same with USB-A, now a few years later we can update to USB-C by replacing outlets cheaply.
Can you imagine having to replace both the outlets for a new connector and a house-sized converter for new power profiles? So expensive and likely turns a simple DIY project into calling an electrician
PoE would be that standard, since it’s 48V already and can run all over the house. However, we don’t actually save anything in terms of efficiency by having everything be DC.
The problem is that nothing wants the same DC voltage. It wants 3.3V, or 5V, or 12V, or 48V, or 18.7V, or whatever. You end up with layers of conversion and save nothing in the end.
Let’s say you start with solar photovoltaic panels, a DC source. It feeds into a DC-DC inverter that puts out a steady 48V. Existing DC-AC microinverters can get 95% efficiency, and DC-DC conversion can be around the same.
In an AC system, we convert to DC at point of use (be it through a wall wort, a floor wort, a USB power port integrated into traditional AC plugs, or something else). This conversion can likewise be around 95% efficient.
In a DC system, we still have to do a DC-DC conversion to get the voltage you actually want at point of use. This is around 95% efficient, as well.
In the end, we stack the same number of conversions at around 95% efficiency no matter if we run AC or DC. Except that assumes we’re coming from a DC source in the first place, like solar photovoltaic. If we come from an AC source, like wind or hydro or pretty much anything besides a solar panel, then we only have transformer losses of converting the higher line AC voltage to what your house uses. Those aren’t 95% efficient; they’re closer to 98% efficient, so we’re better off.
Not only that, but we would still prefer AC for basically anything with a high draw motor, like air con or refrigerators. Now we’re doing DC-AC conversion, and that’s closer to 85% efficient. These are some of the highest draw items in a house–and they’re going to be used more as heat pumps for HVAC, water heaters, and clothes dryers become more common–so that drop in efficiency hits that much harder.
So DC home power sounds like a good idea until you break down how conversion efficiency hits things in practice. If we’re just going to get to the same place, why bother ripping out our current system?
That said, I would like to see PoE get used for residential more. There’s lots of devices that can run off 48V and can also use networking (like smart LED lights). Why not put it over the same plug and skip having to put those devices on a wireless network? Also, you don’t need a licensed electrician to run it. You can’t be an idiot about how to run and terminate it, but you don’t need a license. This would likely be alongside our existing AC wiring, though.
In general, you don’t want DC or Ethernet cabling directly next to AC wiring. I forget the exact rules and distances, but you definitely don’t want them in the same conduit at least. Shielding only helps so much. Just a general note as you probably didn’t mean it quite so literally…
I do like PoE though! I have a server rack that powers a bunch of RPi 4s through a PoE+ switch. Had to make sure there was plenty of headroom as RPi 4s can pull just a wee bit of current under full load. I am just happy it works at all.
It’s running parallel to AC wiring. It’s usually not a big deal in practice, except for higher draw cable.
Your right. I was thinking about my job that runs 480VAC. Either way, testing for interference and noise when you run into issues can go a long way. I am just glad that, to my knowledge, CAT 7 is one standard with everything shielded. CAT 6 had so many variations and most packaging and online portals would not even tell you which ones they were using in the first place. Almost as bad as USB-C connectors.I gave up and ordered some short CAT 7 patch cables for the server so I wouldn’t stress over it. Ended up being a little cheaper than a lot of the cat 6 sets too.
_ It wants 3.3V, or 5V, or 12V, or 48V, or 18.7V,
Exactly
That’s why if you had a 110VDC supply at the wall, you do a simple PWM step-down to the required voltage in every device.
LOADS cheaper/efficient than any USB-C PD circuit…
Saves on transformers, saves on dozens of USB PD wall outlets, saves on communication needed to communicate the PD required between each device and every USB PD wall outlet.
Much cheaper. More efficient.
If only the wall was 100VDC instead of AC
Why would 100VDC help over AC? You lose very little by rectifying AC.
And again, these aren’t the high draw items in the house. Stuff with motors are, like air con and refrigerators. Those are better left on AC. Why bother when the gains are small?
Stuff with motors are, like air con and refrigerators. Those are better left on AC.
No. Trend is they are all showing up with frequency drives. Of which those inverters are rectifying to DC before making their own AC.
Efficiency gains are massive of a frequency drive , hence why they are doing it.
Would be even better if they could drop the first rectifying circuit and just use the inverter portion only.
You lose very little by rectifying AC
You lose a lot actually in all the small cheap rectifiers that are in every device in the house.
Where a single purpose designed FET rectifier that is built for efficiency at the breaker would be drastically better.
AC steps up or down easily and efficiently, DC not so much.
No, AC requires large heavy transformers and then rectifying.
DC dropping down to a lower DC is way easier and more efficient.
Wasn’t that a recommendation for LED 10 years ago already?
Yeah, but frequency drives/inverters were still pretty pricy things back then to for high powered motors for compressors/blowers/etc.
But the cost and efficiency of those things have dropped SIGNIFICANTLY in the past decade…