Heh I should have read your whole post before replying to the first line, but let me pick you apart in another one instead.
1. Most stuff just works on high voltage DC as discussed above. Most switching power supplies simply don't know or care about AC or DC and due to their efficiency switching power supplies are used in almost everything electronic.
Absolutely wrong. The first thing most power supplies do is step down from high voltage AC to something in the general range of whats needed on the highest output value. They step down with a transformer. That transformer only works with AC, if you put DC in it, you're just going to burn it up as it turns into a magnet carrying more current (because its not AC, so the there is no inductive resistance, so there is more current). Please don't give anyone advice on electricity. Ever.
You are living in the past on this one. Most modern electronic equipment utilize switching power supplies because they are cheaper to make, lighter and more efficient. Modern switching supplies almost invariably just rectify the AC into DC as the first step, usually using a full wave rectifier. Full wave rectifiers don't care if you feed them with AC or DC, you get DC out either way and as long as you have the right DC voltage range coming out of the rectifier, the switching power supply will work just as well on AC as DC. Where this is not UNIVERSALLY true (you CAN damage some stuff doing this), it is generally true.
Now, I want to point out to you that I did say there where exceptions. Devices that employ transformers and induction motors will NOT work on DC. That includes CFL's, Ceiling Fans, some Wall warts, most major appliances and the like, but it's pretty obvious they won't run on 12 V DC either...
2. It's easier (and more efficient) to use high voltage DC for charging the batteries. All you need is a rectifier to convert that 220 into about 250V DC and charge the batteries, which is about as simple and efficient as it comes.
... You do realize those batteries you're referring to are actually made up of a bunch of smaller batteries right? There is no single cell at 200v. You aren't charging one 200v batter, you're charging a handful of 12v batteries that you're just blissfully ignorant of.
And you seem to be ignoring the fact that that 12V (aka 13.8V) battery *really* is just a number of 2.3 Volt cells (like 6) strung into a series to get you up to 12 V. So we put 100 in series and get a working voltage of about 230V DC? How's that an issue of ignorance? Or, parish the thought, we just take 10 of your standard 12V batteries and connect them in series to get 120 (138) Working voltage?
It's all for naught anyway because different battery chemistry gives you different cell voltages. But no mater what the battery chemistry, you just string enough cells in series to get you up to the desired working voltage... Or that's what electrical engineers had been designing a long time before I got my EE degree..
3. It's easer (and more efficient) to make an inverter that uses high voltage DC as input. It's pretty easy to just flip the current one way then the other to get AC sufficient to run most induction motors and transformer powered devices.
You have absolutely no idea what you're talking about. The conversion from DC to AC is THE BIGGEST LOSS in the inverters you're referring to. The actual transformer itself is pretty damn efficient if designed properly. Dealing with high voltage DC is extremely dangerous. It ARCs over distances that AC won't. You can put 200v AC traces on a circuit board with little space between them. Do the same thing with the same DC voltage and the board is going to randomly arc all over itself.
So are you claiming that YOUR design where you use a transformer to step down to 12 V THEN rectify it (which is the classical DC supply design) is indeed more efficient than just rectifying it at 120V? Um, don't you have the transformer losses AND the rectifier losses where my design only has the rectifier losses? Further, I would contend that your 12V rectifiers at higher current will actually have MORE losses than mine which run at lower current and would have less IR losses. But don't let pesky facts stop you..
Arcing is an issue, Just because I didn't discuss it here, doesn't mean I'm not aware of it. Yes, you will need to change some stuff out like Circuit breakers and wall switches. You are likely to be required to put in metal pull boxes and conduit for the wiring too. The electrical and building codes and a competent electrician should be employed to keep things up to code. However, that doesn't change the fact that a LOT of stuff in your home can easily run on DC without modification.
Also, I'd like to point out that the fine article is suggesting LOW VOLTAGE DC is the solution. One is going to need to rewire their home for that solution too, I'm just suggesting that the more efficient and cost effective solution is to go with high voltage DC. I'm not claiming that there are not issues to be dealt with, only that these issues are easier and cheaper to deal with than wiring the house for 12V..
4. It's more efficient to use higher voltage in terms of wire size because IxR losses are less for the same power transfer. Chances are the same wires you have now will be fine, but if you go to low voltage (say 13.8V like in your car) you are going to need bigger conductors to avoid the voltage drops over long high current runs. Use higher voltage and lower current, and stick with the wires you have.
The first part is true, larger wires are better for lower current loss. The rest of this is false. DC has different properties than AC. Insulators, wire spacing, and load will behave differently at 200v AC versus DC. You CAN NOT use the same wiring unless you want to burn the building down. Please don't ever tell people anything about electrical wiring, you're going to get someone killed.
Sir, respectfully I disagree that wire size would need to change all that much if you assume you switch to a similar voltage DC from AC. However, I will agree that there ARE issues with DC that will need to be addressed. Arcing of DC when switching is a problem which would require changing out AC switches currently in place (Circuit Breakers and light switches). But I don't think the standard house wiring would necessarily need to be altered that much in conductor size, but I would defer to your local licensed electrician and building codes for a full list of what you are going to need to stay within code.
Full disclosure.. I hold a BSEE and have an interest in emergency power operation of Ham Radio equipment. I've experimented with some of what I suggest here and it works with caveats as noted, at least for the things I've tested. My laptop charger was fine, my desktop PC and LCD display worked great as did the Switching DC power supply for my radios. If you hook up your expensive Flat Screen TV to the battery in your Prius, usually it works, it might not and it might self destruct. Without looking at the power supply design, there's no way I can tell you which option you will get.