I don’t think the DC to DC conversion was adequately discussed in this article. If you were to implement a parallel DC and AC system in your home, you would need all of your DC devices to run on the same voltage, or you would need to convert them from the supply voltage to the useable voltage. The most efficient way to do a DC to DC conversion requires converting to AC to change the voltage, then converting the new voltage back to DC. If your goal is to reduce losses, these conversions would be much more efficient if you started with an AC source.
The only time you have big efficiency gains is when you’re supplying the exact DC voltage required by the device. In a practical house this would mean having a few different DC feeds all at different voltages. That means more cabling and more electrical protection equipment per voltage.
I love the idea that we have a DC source and DC devices, why go to AC in-between? It’s a compelling thought, but the reason is it’s a good general system that is robust and pretty efficient independent of individual situations. Can you make a more optimized system per house taking into account the amount of energy it took to extract the metal for the additional wires and the savings on each conversion device? Yes, of course. Is it practical on a large scale? I don’t think so.
The distribution of different DC voltages that any devices in your home use is already pretty small. USB combo outlets are already common… You get a pretty good capture of consumer devices just with 5V.
Toss a 12V in there as well and you’ve probably now got >%95 of a typical households devices covered.
Also, given a standard, manufacturing will follow to design around the constraints, so over time that 95% would grow as designs move away from “non-standard” voltages to voltages that are available on a standard DC grid.
If there was a DC voltage standard, most things could be made for that and improve efficiency. However, it likely isnt really going to be that much of an improvement to be worth doing.
That site is full of almost good ideas, it’s very odd.