11 ms·

The article mentioned 100-160ft from the surface, so i'm not sure where the "deep" part mentioned in the headlines comes in. Perhaps their ultimate plan is for

The article mentioned 100-160ft from the surface, so i'm not sure where the "deep" part mentioned in the headlines comes in. Perhaps their ultimate plan is for deep & this demo didn't try to address the deep part? That said, if 100ft below had enough forces to produce 100kw (ecological issues aside) that sounds pretty fantastic, even if just a demo.

martyvis 4y ago
I imagine the "deep" aspect is that it seems to be well below surface waves that seem to reek havoc on other projects. That depth is still pretty difficult to service as install without pretty sophisticated planning I would think.
- bayesian_horse 4y ago
  They would be easier to service than off-shore wind turbines. You just need a light cable attached to a buoy, the service ship goes to the boy, pulls up a heavier cable with the light cable, then pull up the whole structure. Come to think of it, the turbine pods may include a ballast tank that can be evacuated, to adjust the height in normal operation or to pull itself up to the surface for maintenance.
  - stjohnswarts 4y ago
    unless it's a rigid structure mounted to the ocean floor then it will almost definitely have ballasts
    - bayesian_horse 4y ago
      The article explicitly states they are free floating tethered to the ocean floor. And this is by far the easier way, I'd think.
  - gehsty 4y ago
    I'm not so sure. For a wind turbine a lot of maintenance can be done without any additional vessel / cranes. If you need to do a major component change you do it with a similar vessel to the ones which installed the turbine. For a subsea tidal turbine you'd need some frame or similar to land the tidal turbine onto, you'd need to clean it before anyone could access it for the maintenance etc. Generally speaking if you have something subsea it should be designed to be maintenance free as recovery costs are so high (like subsea oil and gas production systems).
D13Fd 4y ago
I actually thought the 100kw number sounded awfully low. A typical wind turbine generates around 2 or 3 MW of power at capacity.
- Aeolun 4y ago
  That’s the rating at capacity though, which barely ever happens. The ocean current will never stop, so over the course of it’s life the ocean turbine might well beat out a wind turbine (ok, I consider that mildly unlikely, but it’s nice to have power generation that’s less susceptible to suddenly not producing anything). Also note they say it produced 100kw, not what it was rated for.
  - jojoo 4y ago
    I'm not good at nautics, but in my understanding currents slowly stop and later turn around. Most tide charts are more or less a sine wave, with different highs and lows. So it's interesting how this 100kw was produced. The article only says: "The business was able to generate roughly 100 kilowatts of steady electricity during demonstrations earlier this year." So is this over a few days or just a few hours while peak flow? While currents change, their change is highly forseeable - unlike wind.
    - bayesian_horse 4y ago
      The pods with the turbines are floating in the water, tethered to the seafloor, so they will turn in any direction the current is going.
    - sandpaper26 4y ago
      Currents are relatively unrelated to tides, and are fairly consistent over time (with some seasonal variation due to differences in hemispheric temperatures). From [1], "the large scale prevailing winds drive major persistent ocean currents..." Keyword is persistent. [1] https://en.m.wikipedia.org/wiki/Ocean_current https://en.m.wikipedia.org/wiki/Ocean_current

martyvis 4y ago

I imagine the "deep" aspect is that it seems to be well below surface waves that seem to reek havoc on other projects. That depth is still pretty difficult to service as install without pretty sophisticated planning I would think.

bayesian_horse 4y ago
They would be easier to service than off-shore wind turbines. You just need a light cable attached to a buoy, the service ship goes to the boy, pulls up a heavier cable with the light cable, then pull up the whole structure. Come to think of it, the turbine pods may include a ballast tank that can be evacuated, to adjust the height in normal operation or to pull itself up to the surface for maintenance.
- stjohnswarts 4y ago
  unless it's a rigid structure mounted to the ocean floor then it will almost definitely have ballasts
  - bayesian_horse 4y ago
    The article explicitly states they are free floating tethered to the ocean floor. And this is by far the easier way, I'd think.
- gehsty 4y ago
  I'm not so sure. For a wind turbine a lot of maintenance can be done without any additional vessel / cranes. If you need to do a major component change you do it with a similar vessel to the ones which installed the turbine. For a subsea tidal turbine you'd need some frame or similar to land the tidal turbine onto, you'd need to clean it before anyone could access it for the maintenance etc. Generally speaking if you have something subsea it should be designed to be maintenance free as recovery costs are so high (like subsea oil and gas production systems).

D13Fd 4y ago

I actually thought the 100kw number sounded awfully low. A typical wind turbine generates around 2 or 3 MW of power at capacity.

Aeolun 4y ago
That’s the rating at capacity though, which barely ever happens. The ocean current will never stop, so over the course of it’s life the ocean turbine might well beat out a wind turbine (ok, I consider that mildly unlikely, but it’s nice to have power generation that’s less susceptible to suddenly not producing anything). Also note they say it produced 100kw, not what it was rated for.
- jojoo 4y ago
  I'm not good at nautics, but in my understanding currents slowly stop and later turn around. Most tide charts are more or less a sine wave, with different highs and lows. So it's interesting how this 100kw was produced. The article only says: "The business was able to generate roughly 100 kilowatts of steady electricity during demonstrations earlier this year." So is this over a few days or just a few hours while peak flow? While currents change, their change is highly forseeable - unlike wind.
  - bayesian_horse 4y ago
    The pods with the turbines are floating in the water, tethered to the seafloor, so they will turn in any direction the current is going.
  - sandpaper26 4y ago
    Currents are relatively unrelated to tides, and are fairly consistent over time (with some seasonal variation due to differences in hemispheric temperatures). From [1], "the large scale prevailing winds drive major persistent ocean currents..." Keyword is persistent. [1] https://en.m.wikipedia.org/wiki/Ocean_current https://en.m.wikipedia.org/wiki/Ocean_current