340 comments on Multiple Birds – One Silver BB: A synergistic set of solutions to multiple issues focused on Electrified Railroads
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Why would 110VAC become a dinosaur, compared to 110VDC?
After all, we won't be connecting houses to the grid at 12VDC, the line losses are too large at low voltages.
For long hauls, HVDC makes a lot of sense ... both because of the line losses and because the conversion to AC to feed into a regional grid eliminates the problem of synchronizing AC over long distances ...
... but what pressure does that place on the local grid to change over?
One explanation I've seen is that more and more appliances don't need AC. Computers, TV:s and such would work just fine with DC; they have chopper power supplies since that's cheaper than a transformer, and such devices can work with DC input as well (meaning that nowadays you can cheaply and efficiently convert one DC voltage to another without an AC transformer in between). I've heard of other appliances like fridges and washing machines that have variable frequency drives in order to run at the optimal frequency rather than the usual stop-start with the 50/60 Hz from the grid.
That being said, the potential savings from switching to a DC local grid are almost certainly not worth the hassle.
One place where we might see more DC equipment in the future is data centers. Nowadays it's quite wasteful that input AC is first rectified to DC for the UPS:es, then it's inverted back to AC since all the machines have AC input, and the the power supply in each machine rectifies it back to DC.