Hybrid AC/DC distribution system with a shared neutral (2020)
13 comments
·May 1, 2025deepsun
Gibbon1
What the world needs is a 150 watt low voltage power over ethernet standard for lighting an low power appliances.
deepsun
Was just thinking about it for my home. Googling showed that it's only for commercial applications now (like "request a quote" for a lightbulb).
There is a good opportunity for a startup IMHO.
With 100W PoE, one can daisy-chain 10 light bulbs on one cable (or put them on different pairs of wires within one cat6 cable).
But what I really wanted is controllable devices, so that I could re-assign lights<->switches in my home hub.
UPDATE: and you don't need an electrician license to work with low voltage.
holowoodman
There is, shockingly enough, 100W PoE lighting...
https://www.cisco.com/c/en/us/solutions/enterprise-networks/...
Imho a totally crazy waste of expensive gear, but whatever floats your boat...
kbaker
I could hope for a future PoE-over-Data Line (PoDL) version using an 18 AWG twisted pair that would work for this, providing something like 48V @ 3 or 4 A, and 10BASE-T1L for data. Hopefully a standard way to do this gains traction.
The existing limitation is with the 2x23 AWG (or 4x23 AWG) of Cat5e/6/6a not providing a lot of current-carrying capability at a safe voltage.
londons_explore
USB-C fulfils that already.
It doesn't work out economically because big networks of usb devices (ie. Hubs) all need the power components if one is to maintain the generalisability of being able to plug anything into the grid anywhere.
kevin_thibedeau
USB has significant length limitations and the cabling is generally not plenum rated. It's also silly to have a cable with wires that will never be used beyond negotiating for power.
deepsun
USB-C is for short distances (<4m) and is more expensive than CAT6 cable.
https://www.cablematters.com/Blog/USB-C/how-long-can-a-usb-c...
SigmundA
Not sure sharing the neutral buys much as conductor size needs to go up vs just running separate wire.
Most hybrid inverters now days are high frequency and have a HVDC bus sitting between battery DC/DC, solar MPPT and AC inverter/converter. Since solar comes down from roof with HVDC it can be inverted without a transformer to AC then the LV battery uses a physically smaller HF transformer on the buck/boost to that bus.
Seems to be lots of talk to tap that HVDC bus for say EV charging as its around 400v, also some inverters moving to HVDC batteries as well simplifying the DC/DC even more so.
Could see a future where houses have a HVDC panel with battery, solar, inverter and EV charger hanging off it, perhaps even HVDC from pole with solid state transformers. If/when EV become popular then you will have much more readily available/cheap HVDC switching gear at 400/800v. Hard to beat the simplicity and reliability of AC using transformers though for distribution.
MisterTea
> Not sure sharing the neutral buys much as conductor size needs to go up vs just running separate wire.
The article mentions a system which will balance the shared current. But that sounds like needless complexity that was introduced to entice power companies by saving a few bucks not needing two insulators and conductors installed on each pole.
So we're saving on the wire only. I would probably pay for extra wire just to make the system simpler, unless I was a builder aiming to save on costs.