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Comment by algo_trader

4 months ago

> practical voltage for a DC grid using early electrical machinery is around 2 kV.

What is a current (pun!) practical limit?

If a 100MW PV farm and a data center are separated by 1km (20 Olympic pools) - is there a way to avoid AC?

I know there are future solutions [1]

[1] https://techcrunch.com/2025/04/07/former-tesla-exec-drew-bag...

9 comments

algo_trader

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analog31  4 months ago

The early limit was because high voltage DC required producing it at the generator, whereas you could produce high voltage AC by generating at a lower voltage and then stepping it up with a transformer for long distance transmission.

The rules are changing because of switchmode voltage conversion, using transistors to switch the voltage at a high frequency, where the magnetics (transformers, inductors) can be much smaller and more efficient, then converting back to DC. This is how virtually all smaller power supplies have been made for years, the only question (which I don't know) being how far along we are at reaching the voltage levels of long distance transmission in this way.

I'd think that hustling us towards DC with electronic voltage conversion would be a reasonable strategic goal for dealing with the transformer problem, worthy of support by a government.

  • angry_octet  4 months ago

    HVDC and UHVDC are used extensively for long distance transmission, notably for undersea cables and in China, which has made massive R&D investments in the technology in order to shift energy from West to East. Large solar, wind and hydro in the West.

    However, DC does not make sense for a radial power distribution network. The article is propagating nonsense.

lstodd  4 months ago

That link talks about 5MW 35kv AC / 800v DC converters.. completely different thing, they try to sell a single-source PV invertor-to-35KV AC solution first, then 35KV to 800V DC second, to have a sorta complete solution of PV-to-datacenter. And it's only 5MW. And only 35KV AC. For moving 100MW even over a few km you would need 110KV at least. I think. An overhead wire can handle about 600A of current, that's the physical limit and the reason for kilovolts there.

Consider also that there is nothing existing in transmission and switching gear certified for HVDC it being rare one-off projects so far, while AC is ubiquitious, more-or-less mass-produced and many people are trained in its maintenance.

quickthrowman  4 months ago

> If a 100MW PV farm and a data center are separated by 1km (20 Olympic pools) - is there a way to avoid AC?

Not in any economical sort of way. A rectifier and two transformers is cheaper than directly switching HVDC. If you step up the voltage to 115kV, a 100MW three-phase AC circuit is only 500 amps.