4 ms·

This sound like an absurd way to get fresh water to an island.

sliken 10y ago
Dunno. Maybe a few hours of a tug boat is less energy than desalinization of a similar amount of salt water? Not to mention desalinization plants likely cost more than a tug boat. Doubly so if you need to ship fuel to the desalinization plant via boat.
- aaron695 10y ago
  > The trip to Barbados was expected to take five or six days. One would think a pipeline would be cheaper. I guess they have done the maths on a $2 million investment though. But it's not intuitive.
  - geon 10y ago
    Thats a long pipeline. Apparently, the Keystone pipeline cost 7 billion $. https://en.m.wikipedia.org/wiki/Keystone_Pipeline https://en.m.wikipedia.org/wiki/Keystone_Pipeline I'm guessing a water pipeline would be cheaper, and it would need less capacity. But it would have to be constructed for underwater conditions, and any maintenance would be cumbersome.
    - semi-extrinsic 10y ago
      The Langeled underwater pipeline, carrying natural gas from Norway to the UK, is a bit longer than the Barbados-Surinam distance (at 1200 km), and cost approx. 2 billion USD adjusted for inflation. That's a really big-ass pipeline though, at 44" diameter. I guesstimate they could probably get this water pipeline done at about a hundred million USD. Edit: Digging a bit further, subsea pipeline lay cost can be roughly approximated at 0.04 million USD per inch-kilometer (that is, multiplied by pipeline length and by diameter in inches) for 8"-24" pipe. Furthermore we can estimate that Barbados would need a flowrate of 5 000 L/s to supplement their water supply, giving an optimal pipeline diameter of 8". That means it would cost 942km * 8in * 0.04 million USD/(km*in) = 300 million USD.
      - StavrosK 10y ago
        What do you base that estimate on, given that planning, permits, work etc don't scale with the diameter of the pipe?
        semi-extrinsic 10y ago
        Actually, work does scale with the diameter. For lower diameter pipe, you can use a smaller, less specialized lay barge with less crew, the welding goes quicker meaning progress is faster, and you can fit more km of pipe on each supply ship. Also, the cost of permits (called Right-Of-Way, ROW) is a very small fraction of the total cost, as is the planning cost. Materials cost for the pipe, OTOH, can be as much as 60% of total.
        aaron695 10y ago
        I guess the boat system can be moved around the world to meet demand. Unlike a pipeline that might not get used again for another 10 years. Still I think the numbers seem off for a boat dragging water in bags for 6 days to be cost effective.
        semi-extrinsic 10y ago
        If you've never purchased pressure-rated pipe, you'd be shocked at the cost of even a 6m piece of 1" PN20 pipe.
  - ghshephard 10y ago
    Pipelines for water are only energy efficient if you have gravity working for you. I'm willing to wager that there isn't a 10x difference in the cost of towing that water to the Barbados versus pumping it in a pipeline. And, of course, you don't need a pipeline when you tow it. (though you do need big bags)
slededit 10y ago
They used to tow ice bergs back before refrigeration was common. This seems normal by comparison.

Dunno. Maybe a few hours of a tug boat is less energy than desalinization of a similar amount of salt water? Not to mention desalinization plants likely cost more than a tug boat. Doubly so if you need to ship fuel to the desalinization plant via boat.

aaron695 10y ago
> The trip to Barbados was expected to take five or six days. One would think a pipeline would be cheaper. I guess they have done the maths on a $2 million investment though. But it's not intuitive.
- geon 10y ago
  Thats a long pipeline. Apparently, the Keystone pipeline cost 7 billion $. https://en.m.wikipedia.org/wiki/Keystone_Pipeline https://en.m.wikipedia.org/wiki/Keystone_Pipeline I'm guessing a water pipeline would be cheaper, and it would need less capacity. But it would have to be constructed for underwater conditions, and any maintenance would be cumbersome.
  - semi-extrinsic 10y ago
    The Langeled underwater pipeline, carrying natural gas from Norway to the UK, is a bit longer than the Barbados-Surinam distance (at 1200 km), and cost approx. 2 billion USD adjusted for inflation. That's a really big-ass pipeline though, at 44" diameter. I guesstimate they could probably get this water pipeline done at about a hundred million USD. Edit: Digging a bit further, subsea pipeline lay cost can be roughly approximated at 0.04 million USD per inch-kilometer (that is, multiplied by pipeline length and by diameter in inches) for 8"-24" pipe. Furthermore we can estimate that Barbados would need a flowrate of 5 000 L/s to supplement their water supply, giving an optimal pipeline diameter of 8". That means it would cost 942km * 8in * 0.04 million USD/(km*in) = 300 million USD.
    - StavrosK 10y ago
      What do you base that estimate on, given that planning, permits, work etc don't scale with the diameter of the pipe?
      - semi-extrinsic 10y ago
        Actually, work does scale with the diameter. For lower diameter pipe, you can use a smaller, less specialized lay barge with less crew, the welding goes quicker meaning progress is faster, and you can fit more km of pipe on each supply ship. Also, the cost of permits (called Right-Of-Way, ROW) is a very small fraction of the total cost, as is the planning cost. Materials cost for the pipe, OTOH, can be as much as 60% of total.
        aaron695 10y ago
        I guess the boat system can be moved around the world to meet demand. Unlike a pipeline that might not get used again for another 10 years. Still I think the numbers seem off for a boat dragging water in bags for 6 days to be cost effective.
        semi-extrinsic 10y ago
        If you've never purchased pressure-rated pipe, you'd be shocked at the cost of even a 6m piece of 1" PN20 pipe.
- ghshephard 10y ago
  Pipelines for water are only energy efficient if you have gravity working for you. I'm willing to wager that there isn't a 10x difference in the cost of towing that water to the Barbados versus pumping it in a pipeline. And, of course, you don't need a pipeline when you tow it. (though you do need big bags)

slededit 10y ago

They used to tow ice bergs back before refrigeration was common. This seems normal by comparison.