<The post-oil energy economies of the future - by Gordon Brown The Oil Drum DrumBeat: July 16, 2008>

340 comments on Multiple Birds – One Silver BB: A synergistic set of solutions to multiple issues focused on Electrified Railroads

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robert2734 on July 14, 2008 - 8:25pm Permalink | Subthread | Parent | Comments top

No, AC is still cheaper than DC for a substation every 30 miles. I just worry as electronics get cheaper, AC is going to become a dinosaur. But not yet. Say the railroad puts wind and solar along the way. Than it will be easier to interface to DC. But one humungous project at a time I guess.

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eric blair on July 15, 2008 - 3:59am Permalink | Subthread | Parent | Comments top

I just worry as electronics get cheaper, AC is going to become a dinosaur.

Alas, "we" have no way of knowing if the doomer predictions of 'no IC's' will be the way things go, copper becomes expensive due to mass electrification, or some break-through with super-conductors make them truly room-temp - picking AC or DC might be seen as a bad move with the lens of history. (Great IC's should make DC 'better', no copper and no superconductors ruins the tradition of AC step up/step down transformers as 2 examples)

I'd worry more about government mandates being made not due to being the 'best' choice but because some quid crossed the right palms.

Perhaps Alan can toss into the mix suggestions about Open Records so if there is corruption, the parties can be fingered in the future or perhaps get lucky in preventing the public funds being used for private benefit.

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BruceMcF on July 15, 2008 - 5:49pm Permalink | Subthread | Parent | Comments top

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?

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jbl on July 16, 2008 - 3:45am Permalink | Subthread | Parent | Comments top

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.

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340 comments on Multiple Birds – One Silver BB: A synergistic set of solutions to multiple issues focused on Electrified Railroads

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