3 ms·

For the sake of argument if we decide that DC in the home makes sense then the logical follow-on question is: what voltage? While there are 24, 48, and other v

by mikece 5y ago

For the sake of argument if we decide that DC in the home makes sense then the logical follow-on question is: what voltage? While there are 24, 48, and other voltage DC devices is the expectation that we would replace 120VAC (in the US) with 12VDC? For the same power we would be pushing 10x the amps which means more copper in the wiring lines, more line loss as currents go up, etc. In the end I think we would still end up with dozens of voltage changers to step up or step down voltage for our devices. (And then there's the question of what electrical interface we should use -- are we really going to go with USC-C for power delivery despite it's inability to lock into place?)

beardyw 5y ago
Yes, low voltage means high current. OK for consumer devices but scary for stuff like heaters. AC is very convenient to convert to the required DC voltage, which will always vary. Switched mode adapters are light weight and efficient. Not convinced this is going anywhere.
rektide 5y ago
Not a particularly useful point of reference but the International Space Station's secondary bus (that powers all the devices) is 124Vdc. Stepped down from ~160Vdc provided by solar+batteries. Worth noting that 120Vac goes considerably higher than 120V. 120 is supposed to be the average, root mean squared. This implies to me we might be able to have lower currents if we wanted to go even higher voltage DC, without having to rewire. One other note, usb-c defined a locking connector in 2016. There's a m2 screw 6.8mm above the flat of one side of the jack.
- mikece 5y ago
  124VDC on the ISS: I wonder if that means that all electrical items on the ISS have to made to operate with that voltage? I don't think they would want to waste power making heat in order to change 124VDC to 12V, 6V, 9V, 20V, etc.
  - rektide 5y ago
    I'm expecting this is just the bus power to the "modules", the different sections of the ISS. I rather expect most modules probably have a down-converter & run off something like 12, 24, or perhaps the shuttle's 28Vdc. ISS isn't afraid to waste some power. The photovoltaic arrays send power to a "sequential shunt unit", which adds resistive load to maintain a constant voltage/current from the array. Admittedly, not applicable when running off battery, but it shows that power efficiency is not really the priority.

by mikece 5y ago

beardyw 5y ago

Yes, low voltage means high current. OK for consumer devices but scary for stuff like heaters. AC is very convenient to convert to the required DC voltage, which will always vary. Switched mode adapters are light weight and efficient. Not convinced this is going anywhere.

rektide 5y ago

Not a particularly useful point of reference but the International Space Station's secondary bus (that powers all the devices) is 124Vdc. Stepped down from ~160Vdc provided by solar+batteries. Worth noting that 120Vac goes considerably higher than 120V. 120 is supposed to be the average, root mean squared. This implies to me we might be able to have lower currents if we wanted to go even higher voltage DC, without having to rewire. One other note, usb-c defined a locking connector in 2016. There's a m2 screw 6.8mm above the flat of one side of the jack.

mikece 5y ago
124VDC on the ISS: I wonder if that means that all electrical items on the ISS have to made to operate with that voltage? I don't think they would want to waste power making heat in order to change 124VDC to 12V, 6V, 9V, 20V, etc.
- rektide 5y ago
  I'm expecting this is just the bus power to the "modules", the different sections of the ISS. I rather expect most modules probably have a down-converter & run off something like 12, 24, or perhaps the shuttle's 28Vdc. ISS isn't afraid to waste some power. The photovoltaic arrays send power to a "sequential shunt unit", which adds resistive load to maintain a constant voltage/current from the array. Admittedly, not applicable when running off battery, but it shows that power efficiency is not really the priority.