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Comment by throwawaymaths

1 year ago

Sounds expensive

I believe underwater lines are typically not that expensive (compared to other major energy generation/transmission projects). It's actually much easier to lay a cable in water (just drop it in) that it is over land (where you either have to construct pylons or dig a trench).

  • Well... the HVDC cables and in particular the converter stations at each end are quite a bit more expensive than equivalent HV AC infrastructure. But yes, it's definitely affordable and there are many submarine transmission interconnects throughout the world these days.

  • If nothing else, environmental review is a thing for anything that goes into the water in Hawaii, and that is very expensive.

  • They are actually in a trench unless it's super deep. You don't want a ship anchor to catch a submarine cable...

    • Are you guessing based on installations in other countries, or do you know that?

      I would presume that volcanic rock is difficult to put a trench down through. But I am interested to know.

      Edit: I found a good article with pictures of the equipment used about water jets to trench in soft seabeds: https://www.mdpi.com/2077-1312/8/6/460/htm It mentions cable ploughs and mechanical trenching machines. I would presume trenching in rock is sometimes required near-shore.