Yes this and it is also much harder to switch off a heavy DC load than an AC one. Once current starts flowing in DC and you try to open a switch, an arc will form that never gets extinguished since the voltage doesn't cross 0 like it does in AC. Hence why switches are always significantly derated for DC versus AC.
That absolutely is. You could be better with 48 or even 24 volts, but then you are out of luck if you want to power a majority of devices which are 12v. So your only option is to go for USB-A wall socket which essentially is a wall-wart hidden in your wall. I do not see a good solution here.
Well, there is less drop with more copper, so it's more about costs. Cost of cables, DC-DC converters, power supplies and their efficiency determine optimal configuration. Probably going as high as cheap mass market DC-DC converters and PSUs allow is good rule of thumb for low voltage, so like 20-24 V. Beyond that better to go with high voltage.
For some reason, I feel like 48V DC over super-chunky aluminum bus bars is the only way you could avoid making the DC whole-house wiring cost less than the entire rest of the house.
As I understand it, the problems that make aluminum wire strictly inferior to copper wire--expansion coefficient, heat dissipation, non-conductive oxide, and strand breakage--are less significant in bus bars. The remaining concerns would then be bimetallic junction corrosion and work hardening.
Maybe a bus duct with polybenzimidazole spacers and insulation? Still sounds expensive and inefficient, though.
Boats and RVs do this but the cables are gigantic compared to AC cables. Also as they age voltage drop becomes a big issue, especially on boats since the environment is so corrosive.
You have to choose wire gauges carefully. A lot of cables that connect power supplies to their devices have thin wires that don't loae much voltage over the meter or so of cable. But if you woukd extend that with an equal gauge wire to some meters if length, the conmected device will likely burn out around then as well.
