4 ms·

Are the losses thermal? How significantly could this change the ocean temperature near the cable? 50% of 600 GW is enough to cause a 10C increase in the tempera

Are the losses thermal? How significantly could this change the ocean temperature near the cable? 50% of 600 GW is enough to cause a 10C increase in the temperature of 10 million liters of seawater every second?

elil17 5y ago
The short answer is that if 10,000,000 L/s of well mixed water passed over the wire, it’s temperature would increase by 0.75 degrees Celsius. The long answer is that this is not quite the right way to view the question. There will be a temperature gradient around the cable - a zone where water is heated. The question is, how hot is this zone and how large is it. The cable will be buried, which makes the zone larger and less hot. However, this all depends on the type of soil in the ocean floor. One thermal study estimated that, with typical operating temperatures and burying depths, the sea floor temperature (of the soil, not the water) would heat by 10 to 18 degrees Celsius. This is enough to potentially interfere with ocean life, according to the authors of the study. Because of limits in the operating temperature of cables, a project like this would make a larger zone like this, but the maximum temperature would stay the same. It’s important to note that we already mess up aquatic life by discharging thermal energy into bodies of water. High temperature water discharge from power plants can make rivers more friendly towards invasive species and shift the balance of aquatic ecosystems. This project might be a net neutral for aquatic life by reducing high temperature discharge into rivers while creating hot spots in the ocean. Thermal study: https://doi.org/10.1093/gji/ggw195 https://doi.org/10.1093/gji/ggw195
- deleted 5y ago
  [deleted]
- laurent92 5y ago
  What about the magnetic field? I think distance is required between the two sides of the cable to prevent arc, which also means there will be a magnetic field.
  - duskwuff 5y ago
    Negligible. The magnetic field is produced in the space between the conductors, and falls off very rapidly (inverse cube) as you move away from that.
  - elil17 5y ago
    Heat becomes an issue before magnets do. Magnets follow an inverse power law but thermal conduction regimes produce linear temperature gradients. The spacing required for cooling is greater than the spacing required for EM insulation except for very low power flows.
- AnimalMuppet 5y ago
  10,000,000 L/s over 15,000 km. That's 15,000,000 meters. That seems quite likely to happen, and then some.
  - elil17 5y ago
    What seems quite likely to happen?
    - AnimalMuppet 5y ago
      10,000,000 liters per second flowing past the cable.
frazbin 5y ago
hmm, 500 gigawatts dissipated over 300k square gigameters of ocean surface gives a forcing effect of 1.6 milliwatts per square meter. Global warming right now is forcing 1w/sqm, so it's not a problem at this scale. But it's not a crazy question either.
- elil17 5y ago
  It’s not evenly spread, though. It’s concentrated along the cable. It won’t heat up the ocean much as a whole, but it will create “hot spots”, which may change the balance of ecosystems in the regions of the ocean the cable passes through. Worth it to stop carbon emissions? Absolutely, in my opinion. Something that should be considered and minimized if possible? Also yes.
  - frazbin 5y ago
    That's a good point. 500 gigawatts over 15 megameters gives 20kw/m of local heat to deal with, which sounds kind of yikes.. but then again a pool heater draws 5kw. Seems clear the biggest effect will be on the seabed-- but that's already true because you gotta drop the cable. I reckon the cable itself, and its underwater infrastructure, might have more impact than the heat it generates. Another consideration is that there have always been heat sources in the deep ocean.

elil17 5y ago

The short answer is that if 10,000,000 L/s of well mixed water passed over the wire, it’s temperature would increase by 0.75 degrees Celsius. The long answer is that this is not quite the right way to view the question. There will be a temperature gradient around the cable - a zone where water is heated. The question is, how hot is this zone and how large is it. The cable will be buried, which makes the zone larger and less hot. However, this all depends on the type of soil in the ocean floor. One thermal study estimated that, with typical operating temperatures and burying depths, the sea floor temperature (of the soil, not the water) would heat by 10 to 18 degrees Celsius. This is enough to potentially interfere with ocean life, according to the authors of the study. Because of limits in the operating temperature of cables, a project like this would make a larger zone like this, but the maximum temperature would stay the same. It’s important to note that we already mess up aquatic life by discharging thermal energy into bodies of water. High temperature water discharge from power plants can make rivers more friendly towards invasive species and shift the balance of aquatic ecosystems. This project might be a net neutral for aquatic life by reducing high temperature discharge into rivers while creating hot spots in the ocean. Thermal study: https://doi.org/10.1093/gji/ggw195 https://doi.org/10.1093/gji/ggw195

deleted 5y ago
[deleted]
laurent92 5y ago
What about the magnetic field? I think distance is required between the two sides of the cable to prevent arc, which also means there will be a magnetic field.
- duskwuff 5y ago
  Negligible. The magnetic field is produced in the space between the conductors, and falls off very rapidly (inverse cube) as you move away from that.
- elil17 5y ago
  Heat becomes an issue before magnets do. Magnets follow an inverse power law but thermal conduction regimes produce linear temperature gradients. The spacing required for cooling is greater than the spacing required for EM insulation except for very low power flows.
AnimalMuppet 5y ago
10,000,000 L/s over 15,000 km. That's 15,000,000 meters. That seems quite likely to happen, and then some.
- elil17 5y ago
  What seems quite likely to happen?
  - AnimalMuppet 5y ago
    10,000,000 liters per second flowing past the cable.

frazbin 5y ago

hmm, 500 gigawatts dissipated over 300k square gigameters of ocean surface gives a forcing effect of 1.6 milliwatts per square meter. Global warming right now is forcing 1w/sqm, so it's not a problem at this scale. But it's not a crazy question either.

elil17 5y ago
It’s not evenly spread, though. It’s concentrated along the cable. It won’t heat up the ocean much as a whole, but it will create “hot spots”, which may change the balance of ecosystems in the regions of the ocean the cable passes through. Worth it to stop carbon emissions? Absolutely, in my opinion. Something that should be considered and minimized if possible? Also yes.
- frazbin 5y ago
  That's a good point. 500 gigawatts over 15 megameters gives 20kw/m of local heat to deal with, which sounds kind of yikes.. but then again a pool heater draws 5kw. Seems clear the biggest effect will be on the seabed-- but that's already true because you gotta drop the cable. I reckon the cable itself, and its underwater infrastructure, might have more impact than the heat it generates. Another consideration is that there have always been heat sources in the deep ocean.