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Comment by martinald | Hacker News Reader

No, not really. As far as I'm aware HVDC links are more efficient than AC links (even with AC/DC/AC conversion).

It looks like a tradeoff. The only place in the world doing a significant amount of long distance transmission is China. Their wind and coal resources are in the west, and demand is in the east, and transporting coal by rail just further increases air quality problems in the east. Based on what they are implementing, HVDC make sense at 800km+, and AC for shorter runs. I think it comes down to HVDC requires less conductor due to the AC skin effect, weighed against cost/loss for DC->AC.

https://en.wikipedia.org/wiki/Ultra-high-voltage_electricity...

Manitoba Hydro's total DC transmission distance is +3,000km over 3 runs.

https://www.hydro.mb.ca/corporate/facilities/bipole_lines/

Hydro-Quebec is also doing at least one 1500km hvdc to the US and multiple 1000+km lines to the dams in the north. https://en.m.wikipedia.org/wiki/Hydro-Qu%C3%A9bec%27s_electr...

If anyone is curious about this HVDC line and the Quebec grid in general I gave a small talk about it ;)

https://github.com/pirate/quebec-power-grid-talk

It's one of the only multi-terminal HVDC lines in the world, most of the others are just point-to-point.

They also literally short out the power lines with DC to warm them up and melt the ice off during ice storms, pretty crazy stuff.

You also have reactive losses with AC.

The Pacific DC Intertie was the biggest in the world until the Three Gorges stuff.

https://en.wikipedia.org/wiki/Pacific_DC_Intertie

More interestingly--it dates to the Kennedy Administration.

Yes, exactly. But for example interconnecting Houston with AZ or NM power plants, I think HVDC will have fewer losses than AC. Could be wrong thoguh.

Yes, for that run. The reality is that a far cheaper option would be to just install natural gas peaker turbines in Houston. Chienre Energy is exporting LNG from there so plenty of gas, and I’d estimate the cost per GW at $200M vs $1B, and the time to complete at 1 year vs 5 years.

AC transmission has worse power loss per unit distance. But has very little 'base' cost.

HVDC has better marginal loss , but you pay a loss up front for conversion

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