I've been wondering for awhile about the economics of the AC vs DC grid thing. Historically, AC made a lot more sense because transformers are simple and relatively straightforward to make. But now we have amazing capabilities to handle enormous amounts of power with modern IGBTs and similar power-switching transistors. (A modern high-end EV motor controller, for instance, might be able to handle a megawatt of power. Not continuously, but still.) Is a DC-DC converter now more economically viable than an equivalent transformer? The former is more techincally complicated, but the latter is bulky and requires large quantities of expensive input materials like copper.
A big problem with solid state electronics is fault current handling. The grid would become extremely brittle if it was purely a DC conversion setup. Semiconductors don't do too well outside their happy zone. All it takes is some wind and tree to fire up a very large arc welder. If you can't momentarily handle 10x+ the rated system capacity, you are gonna have a really bad time. Ordinary transformers in oil bath can take a hammering for many cycles. A semiconductor wouldn't make it through one.
That seems like it's within striking distance of competitive, no? You get some major advantages in size and production automation. Perhaps it's ok for it to die sooner if you can get it built now and then replace it later.
well aside from being effectively 20 times more expensive over entire operation...
DC switches (as in, just a power switch) are vastly more expensive because while in AC you have 100 breaks in current a second, DC is constant so it is far harder to break. So even if you had device that could use both (not hard with SMPS, they have rectification as first step), it's still essentially " replace everything".
The protections side is a big problem - most HVDC has circuit breakers operating on the HVAC sides of the link so going to full DC transmission presumably wouldn't eliminate that equipment.
Or, alternatively, you switch to DC to get more current capacity over existing wires. (At a given voltage, a wire can generally carry more DC current because it doesn't have the same "skin effect" that AC has.) Even if the hardware at the substation is more expensive, it might be cheaper than upgrading the transmission lines.
I really want the US to get on board with solar in general. Parking lot solar is a good thing generally, but I don't think it should be mandatory because it's an inefficient use of resources. We don't have any shortage of rural land.
Maybe a more flexible policy could be something like: for every parking spot, you must add 1 kw of solar somewhere on your property (whether that's the parking lot or building roof or whatever is up to you) or add 2 kw of solar somewhere within a 20 miles of the site or add 3kw of solar somewhere in the US.
A lot of companies might find that the last option is the cheapest, and if that's the case we should want and encourage them to do that instead.
Feels a little gameable. I’d sell solar rights to some bit of land that I was already going to profitably adding solar to. It might still result in good incentives though.
It can be either AC or DC. Aluminum TIG welding uses AC, whereas you'd use electrode-negative DC for steel or copper. As I understand it, with aluminum you need the electrode-negative part of the waveform to transfer heat to the work piece, but you need the electrode-positive part of the waveform to clear out the crud that accumulates in the electrode-negative part. Often you set a lopsided duty cycle and use different frequencies depending on how deep you want the weld to penetrate.
If you go to 100% electrode positive you tend to heat the metal rather poorly, but can turn the end of your tungsten electrode into a molten blob -- which is usually not desirable.
It may be a boon to EV makers everywhere including in China, but I don't think it's a boon to China generally as they buy a lot of their oil from the Gulf states. Thus they're more directly affected by the Hormuz shutdown than the US (which is a net oil exporter and is mostly only affected indirectly by price increases).
Like the Ukraine war, maybe one good thing thing we can say about this terrible situation is that it may encourage a lot of countries to move to renewables (or nuclear) sooner than they otherwise would and cut back on fossil fuels.
The energy crises of the 1970s caused people to start caring a lot more about fuel economy. Now we have the technology for people not to need to buy gas to propel their vehicle at all, and many of them once they switch they're never switching back.
That's true enough at the level of individual households. If the whole neighborhood switches to EVs, the power grid in general might not be built to handle it.
(Personally I don't expect this will be that big a deal, since switching to EVs is something that happens one household at a time over many years. So, it shouldn't come as a sudden shock, and its something the utilities can make long term plans about. It just means power utilities need to be on the ball about not putting off infrastructure upgrades, and it means somewhat higher electricity prices for residential customers.)
Sure, that's basically just intonation (JI). You pick what key you want to play in and a scale, and then you build an instrument around that scale.
(Though something that happens in just intonation is that you often find out you need more notes than you might have originally thought, because JI makes distinctions between notes that are treated as the same in 12-TET. For instance, you might have 10/9 or 9/8 as your major second, or your minor seventh might be 9/5, 16/9, 7/4, or 12/7 depending on context.)
I don't think any just intonation guitar has been mass produced, but you can definitely build one or modify an existing guitar if you have the right tools and are willing to do a bunch of math and learn how to install frets.
Here's a so-so performance of myself playing a Bach piece on a newer and vastly improved version of that just intonation keyboard: https://www.youtube.com/watch?v=rqbWnDhip0A
In 12-EDO the song has 11 distinct pitch classes. (Bach used the tritone, but not the minor second.) In my straightforward JI interpretation, I use 15 pitch classes. (I would have used 16, but my keyboard simply doesn't have a key for that note.)
> the irony it comes from the same people who blame Israel for not letting supplies into Gaza during war.
Israel did in fact do that. In fact there were several months of Israel not allowing any food or supplies whatsoever into Gaza. That was about a year ago. (It's possible Israel may have been supplying rival groups unfriendly to Hamas with food/supplies/weapons in secret, but all regular humanitarian aid was shut off.)
Whether or not one would accept deaths of civilians to get rid of Khamenei, I don't think anyone should accept a school full of children being blown up for no obvious reason. If there was somehow a reason why Khameni could not have killed without attacking that school, then those reasons should be plainly spelled out and evidence presented. As things stand with the limited information we have now, it just looks like a war crime with no strategic upside.
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