Would additional low voltage DC sockets be practical on mass scale?

Question

In RL I noticed that power supply cables with possibility to charge one mobile through USB compatible socket actually exist:

I actually started to wonder, whether for purpose of world building such idea could be move much more further. I mean both electronics and LED light has to convert electricity to low voltage DC, so the voltage would be already converted earlier.

OK, so the question is following: Would additional low voltage DC sockets be practical on mass scale for purpose of connecting small electronics and light? (Safety gains? More efficient conversion at socket instead of dozens of tiny converters? Only less cable clutter? Extra: Roughly which voltage would be reasonable?)

Clarification: I'm trying to make a setting, which is technically modern-like, but quite a few technologies and standards evolved in different direction. Instead of too improbable ideas like steampunk, I mostly try to use ideas that are technically feasible and reasonable enough, just in RL turned out not to be specially popular. I really doubt, that's a good question for EE because, they can can reasonably answer, that right now in RL trying to implement such standard would be not worth the effort.

It's like question concerning airships, ammo, etc... just not so cool.

I agree with @Secespitus, this question does not sound like worldbuilding — , May 19 '17 at 12:17
For local distribution (within a home, for instance), low voltage DC is usable for low-power loads in the USB-b range. Above that, the physics of I^2R losses favor distribution via high voltage ('tension' in 'high-tension' powerlines refers to voltage, not mechanical force.) And as for DC vs AC, Edison lost that bet. Though some superconducting cables have been tried (high voltage DC.) — Catalyst, May 19 '17 at 12:18
@Secespitus Most of the science-based questions could be asked in another topic, but he asks if it is possible and not if it should be done. I think this forum is perfect for this post — , May 19 '17 at 12:31
Are you talking about sockets where the stepdown conversion is performed at the receptacle, or a central transformer rectifier unit and DC distribution wiring? — ThreePhaseEel, May 19 '17 at 12:43
@Raditz_35 Most science-based questions are asking for something that doesn't exist and how to somewhat plasibly achieve it. This includes time-travel, dragons, new creatures and plethora of other topics. But they are trying to build a fictional world or elements of a fictional world. This question feels like experts on a dedicated site can give you a definite real-world answer, while such dedicated sites would normally say "This is not possible in the real world!" when asking WorldBuilding questions. It was a question to the OP why he thinks other sites would be less helpful here. — , May 19 '17 at 12:44
Something similar already exists with these 400V outlets that are used for anything that needs more power than a normal 230/240V outlet. So the household outlets are, in this relationship, already the low-powered ones. — dot_Sp0T, May 19 '17 at 12:45
@Secespitus here are many people from many fields and certainly electronics isn't an exotic topic. If it was asked in an electronics forum, most likely the author would've been declared stupid and ignored. I agree that this question feels super boring, but at least it is a real and focused question unlike so many questions here. Just imagine he wrote a story-based reason for the question and you wouldn't have complained I think — , May 19 '17 at 12:54
@Raditz_35 You are right. There are people from different fields and electronics is not exotic. But I don't see why "the author would've been declared stupid and ignored", which is why I asked him. When in doubt, ask. It doesn't feel boring, I was trying to understand and help him. It was not a "complaint". Helping someone find the right place with the right people to answer your question the way you need it is a way of helping people, too. — , May 19 '17 at 13:02
@Secespitus Mostly agreed, sorry if I misunderstood. I suggest you conduct an experiment though and ask a question like this in an electronics forum. You might get lucky, I always try my best in those cases (because of my background), but man have I seen people getting demotivated there ... — , May 19 '17 at 13:06
@Raditz_35 -- I've worked EE's close vote queue, and I can see why it can be demotivating (people who don't do the slightest bit of background research before tossing a half-baked excuse for a question up, or throw their homework up without a try at solving it for that matter...never mind questions that say the OP is simply out of their league and needs to learn to crawl before they try an Olympic sprint) — ThreePhaseEel, May 19 '17 at 13:12
Yes, it'd be fine, but this isn't worldbuilding, it's far more practical. All you're really asking here is should I plug an adaptor into the socket or install sockets to take more types of plugs. — , May 19 '17 at 13:30
Unless someone has a really good reason not to -- I've gotten a thumbs-up from a more-senior user of EE.SE to flag this for migration there... — ThreePhaseEel, May 19 '17 at 13:53
Its not flashy but this question is perfectly fine. Format and organization wise it is actually a really well written query. Quit close voting things because its not about a start ship or planetary bombardment please. — , May 19 '17 at 15:20

score 2 · Accepted Answer · answered May 19 '17 at 16:03

I see the point, because you don't really want to convert from 110VAC/220VAC down to (say) 5VDC for USB, or 15VDC for laptops etc.

The problem is that for a given power as you drop the voltage the current goes up, which means you need thicker wires and lose more in resistive heating. However, there might be an argument for a secondary "ring main" in each house for (LED) lighting and electronics. Maybe 12VDC would be suitable. At 20A that's 240W which is quite generous just for lights, TV and laptops

score 1 · Answer 2 · answered May 19 '17 at 16:34

Almost a century ago Telecom started to fill basements full of 2V 250kg cells to make a giant -48V battery to power all their subscriber telephones with ringer bells drawing power and now we use MagicJack, VOIP, mobile phones ( and power load on Telecom CO batteries has not risen)

But 48V is just below 50V which is almost universally considered a "safe" voltage meaning no safety agency peripheral approvals needed. (actually -48V lead acid battery is above >50V and this was not the reason for choice of voltage)

Every home has dozens of wallwarts now for a variety of different purposes. They eventually fail due to cost reduced construction and add to the human waste of electronic disposable products often due to temperature rise in the windings.

For a world-changing evolution in DC power distribution in the home, it must be;

reliable,
cheaper,
efficient (low I²R losses on pre-wire house DC cables)
good EMC , meaning low conducted and radiated noise ( no antenna loop effects)
a DC voltage suitable for all DC-DC converters for all home appliances and all expected power levels.
short circuit protection and isolation
conducted DC current noise crosstalk prevention ( with random switched loads)
a low cost centralized DC battery with charger source for uninterrupted standby power is a big plus for some. (not here in Canada where availability for AC is 99.99%)
connected to sustainable free energy source for battery charger is a big plus but has Cost of ownership issues with maintenance

If you can satisfy all these requirements by identifying all the expected loads including DC LED ceiling lights, kitchen electric tools , mobiles etc. then you have a great idea turned into a real solution.

When you satisfy these requirements - then you can define a game-changing DC power strategy in the home. ( A USB power bus is not a game changer)

Harper - Reinstate Monica · Answer 3 · 2017-05-19T21:48:06.857

I see it as a foregone conclusion

I expect this to happen because of the sea changes happening

on the load side: so many important appliances are emerging which either need low voltage (phones, smart home controls, cable boxes, LED luminaires) or are low enough draw to be practical on low voltage (TV, PCs, Energy Star refrigerators and deep freezers, etc.)
on the generation side: home solar is exploding, and we are nearing roof parity - where solar shingles are cheaper than plain old shingles, net of earnings/savings from generating electrical power. At that point it becomes stupid to use regular shingles.
with local storage, thanks to the "market pushing" done by Tesla etc., using hybrid cars as energy storage, consumer fascination with off-grid tech, and consumer frustration with regional power outages rendering their homes uninhabitable, increasingly even though there's a massive solar panel on the roof.

Having battery storage in the house is a good idea, but running an AC inverter 24x7 is sheer lunacy. So I expect low voltage DC in the home to become a huge thing.

Of course we are still arguing about voltages: will it be 12, 24, 36, 48 or some voltage which favors lithium or other batteries?

And we haven't really settled on any sort of plug styles to be a standard. There's no lack... if anything there's a glut of potential plug/socket candidates.

Not least USB, which is already a platform for the power supply negotiating with the load to decide what power level it can draw, it could just as easily negotiate which voltages to provide.

For instance an appliance will have a very tiny buck converter powering a power manager chip, and when plugged into a USB, will negotiate with the supply: "hi, can I have 48v@2A please?" And the plug will either turn that on or say "nope, try an orange receptacle".

So it'll happen, probably with two plug styles, USB for tablets and desk lamps, and the fat DC connector for PCs, cable boxes, refrigerators and the like.

Not sure which sea you're sailing on, but none of your bullet points will resonate with readers here. 400l fridge running via a 5mm barrel connector? Presumably without fast freeze. Will we keep the current 240VAC wiring and have two parallel distribution systems? — Paul Uszak, May 19 '17 at 23:26
Some further points are here : https://electronics.stackexchange.com/questions/34557/getting-rid-of-ac-dc-adapters/247765#247765 — Paul Uszak, May 19 '17 at 23:30
@PaulUszak dude, what the heck? Fridge on a 5mm connector!? I was thinking more like NEMA 2 or SB50. Your link talks like voltage conversion is hard (yet every router I own has a 12VDC wallwart) while proposing the impractical 3.3V as a bus voltage. It's like you're trying to fail. Exactly like that, this is called a strawman argument where you make intentionally stupid choices. AKA Naysaying. Thousands of off-grid homes using DC distribution everyday and it works fine. But they're not trying to fail. — Harper - Reinstate Monica, May 20 '17 at 03:04
Au contraire mon dude, I'd love to see all those dammed little black boxes disappear. They're so not feng shui. I think you might have the wrong end of the stick though. The solution to those few off grid homes is not a whole scale migration of civilisation to DC distribution. It's to eliminate the remaining ones and bring them into the modern world and on to a grid. — Paul Uszak, May 20 '17 at 23:54

Would additional low voltage DC sockets be practical on mass scale?

3 Answers3

I see it as a foregone conclusion