4 ms·

It would take a long time to pump that amount of water out of the lock that you’re lowering, and over time you’ll be pumping saltwater into a freshwater system,

by ok_dad 3y ago

It would take a long time to pump that amount of water out of the lock that you’re lowering, and over time you’ll be pumping saltwater into a freshwater system, which isn’t good. You’d have to do filtering or something, at great expense. Currently it takes a short time to drain the lock, so ships transit faster. It’s pretty fun to do that transit, but I was amazed that the pilot let me conn the ship the whole time instead of doing it themselves. I guess on military ships they prefer we do it maybe, but I was glad for that experience. My ship had two jet turbine engines that did 31 MW of propulsion, which was a small ship compared to most freighters, so energy wise it would be very efficient still.

nashashmi 3y ago
Saltwater mixing is a good point. But the canal has two lanes. One lane is for one direction. The other lane is for the other direction. I can imagine cases where the saltwater is never used.
- ok_dad 3y ago
  The way locks work you can save some by using extra storage ponds but you can’t save it all. You have to move some water into the ocean, because that’s the cost for the physics that move giant ships up and down as easily as this.
Veserv 3y ago
The Panama Canal Authority derives ~3 G$ in fees over ~14 K crossings per year for a average cost of ~200 K$ per crossing. 40 M gallons is ~150 K*m^3. Modern bulk desalination turns seawater into potable fresh water at ~0.40 $/m^3, so only ~60 K$. The cost of filtering out any incidental saltwater mixing should be a tiny fraction of that cost. Even at full desalination it would only constitute ~30% cost increase. Given the minimal amount of filtering that should be required for incidental mixture, it is hard to call that a great expense except in relation to rainwater.
- ok_dad 3y ago
  30% is a large increase to a canal that we use for a huge portion of our consumer goods, I think. I do agree that they soups build desalination plants now, so they can use them in twenty years when they’re finished and the drought is even worse!
  - Veserv 3y ago
    A Neopanamax vessel is allowed to transport 120,000 metric tons of cargo [1]. ~60 K$ would only amount to 0.50 $/t of extra cost. That is only low single-digit percentage increased shipping cost [2]. And again, that is the cost of desalinating 100% seawater, not the proportionally cheaper cost of desalinating whatever single-digit to maybe low double-digit percent you would actually get from incidental mixture during reclamation. [1] https://en.m.wikipedia.org/wiki/Panamax https://en.m.wikipedia.org/wiki/Panamax [2] https://unctad.org/system/files/official-document/rmt2022_en.pdf https://unctad.org/system/files/official-document/rmt2022_en...
    - ok_dad 3y ago
      Good points, I hope the canal authority gets on that! It seems a no brainier to set up even a small desalination plant to make up for droughts.

by ok_dad 3y ago

nashashmi 3y ago

Saltwater mixing is a good point. But the canal has two lanes. One lane is for one direction. The other lane is for the other direction. I can imagine cases where the saltwater is never used.

ok_dad 3y ago
The way locks work you can save some by using extra storage ponds but you can’t save it all. You have to move some water into the ocean, because that’s the cost for the physics that move giant ships up and down as easily as this.

Veserv 3y ago

The Panama Canal Authority derives ~3 G$ in fees over ~14 K crossings per year for a average cost of ~200 K$ per crossing. 40 M gallons is ~150 K*m^3. Modern bulk desalination turns seawater into potable fresh water at ~0.40 $/m^3, so only ~60 K$. The cost of filtering out any incidental saltwater mixing should be a tiny fraction of that cost. Even at full desalination it would only constitute ~30% cost increase. Given the minimal amount of filtering that should be required for incidental mixture, it is hard to call that a great expense except in relation to rainwater.

ok_dad 3y ago
30% is a large increase to a canal that we use for a huge portion of our consumer goods, I think. I do agree that they soups build desalination plants now, so they can use them in twenty years when they’re finished and the drought is even worse!
- Veserv 3y ago
  A Neopanamax vessel is allowed to transport 120,000 metric tons of cargo [1]. ~60 K$ would only amount to 0.50 $/t of extra cost. That is only low single-digit percentage increased shipping cost [2]. And again, that is the cost of desalinating 100% seawater, not the proportionally cheaper cost of desalinating whatever single-digit to maybe low double-digit percent you would actually get from incidental mixture during reclamation. [1] https://en.m.wikipedia.org/wiki/Panamax https://en.m.wikipedia.org/wiki/Panamax [2] https://unctad.org/system/files/official-document/rmt2022_en.pdf https://unctad.org/system/files/official-document/rmt2022_en...
  - ok_dad 3y ago
    Good points, I hope the canal authority gets on that! It seems a no brainier to set up even a small desalination plant to make up for droughts.