As we all know, AC won the “War of the Currents”. The reasoning behind this is that AC voltage is easy to convert up/down with just a ring of iron and two coils. And high voltage allows us to transport current over longer distances, with less loss.

Now, the War of the Currents happened in 1900 (approximately), and our technology has improved a lot since then. We have useful diodes and transistors now, we have microcontrollers and Buck/Boost converters. We can transform DC voltage well today.

Additionally, photovoltaics produces DC naturally. Whereas the traditional generator has an easier time producing AC, photovoltaic plants would have to transform the power into AC, which, if I understand correctly, has a massive loss.

And then there’s the issue of stabilizing the frequency. When you have one big producer (one big hydro-electric dam or coal power plant), then stabilizing the frequency is trivial, because you only have to talk to yourself. When you have 100000 small producers (assume everyone in a bigger area has photovoltaics on their roof), then suddenly stabilizing the frequency becomes more challenging, because everybody has to work in exactly the same rhythm.

I wonder, would it make sense to change our power grid from AC to DC today? I know it would obviously be a lot of work, since every consuming device would have to change what power it accepts from the grid. But in the long run, could it be worth it? Also, what about insular networks. Would it make sense there? Thanks for taking the time for reading this, and also, I’m willing to go into the maths, if that’s relevant to the discussion.

  • talEnglish
    49·
    3 months ago

    DC is used for long-range transmission in high-voltage DC (HVDC) transmission lines today.

    https://en.wikipedia.org/wiki/High-voltage_direct_current

    A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages between 100 kV and 800 kV.

    HVDC lines are commonly used for long-distance power transmission, since they require fewer conductors and incur less power loss than equivalent AC lines. HVDC also allows power transmission between AC transmission systems that are not synchronized. Since the power flow through an HVDC link can be controlled independently of the phase angle between source and load, it can stabilize a network against disturbances due to rapid changes in power. HVDC also allows the transfer of power between grid systems running at different frequencies, such as 50 and 60 Hz. This improves the stability and economy of each grid, by allowing the exchange of power between previously incompatible networks.

    However, since grids are AC, it’s just to send power to a grid or pull from one.

    We also do have some increasingly beefy DC in individual households in some forms:

    • You mention solar PV systems, but more generally, 12V systems used in vehicles (and the related 24V and 48V systems that are sometimes used to push more power) are more common, with lithium batteries that can do many more charge cycles than lead-acid being available.

    • USB PD can negotiate pushing up to 240W now at 48V, which is a fair bit.

    • SoylentBlake@lemm.eeEnglish
      2·
      3 months ago

      Yep, the Pacific DC Intertie sends HVDC from the Bonneville Dam in The Dalles, Oregon down to LA, supplying LA with up to half their residential power needs. The Columbia River powers most of the west coast.

      Once we start talking long distance transmission HVDC becomes cheaper around mile 500 than our standard AC.

      Both AC and DC have their place, and applications each are particularly better suited for.

    • gazter@aussie.zoneEnglish
      1·
      3 months ago
      • USB PD can negotiate pushing up to 240W now at 48V, which is a fair bit.

      So if I wanted to wire my home to take advantage of this, supposing I had a house battery on solar, would I have some kind of DC-DC converter from battery to 48V, then cable to outlets with some kind of USB PD adaptor? How much advantage do I get from this, vs using existing 240V outlets + wall wart?