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Optimally placing containers on ships must be a very difficult problem. Consider you might want: -heavier containers at the bottom for stability -refrigerated

Optimally placing containers on ships must be a very difficult problem. Consider you might want: -heavier containers at the bottom for stability -refrigerated containers on the inside to reduce heat loss -containers to be unloaded first near the top etc And all in 3 dimensions!

IncreasePosts 2y ago
All of the refrigerated containers I have seen have had a built in generator/AC unit...why would shippers care about heat loss, unless they are providing the energy to refrigerate the containers?
- hermitcrab 2y ago
  I assume the shippers are providing the power for refrigerated containers. Otherwise they would need to have batteries or fuel that could last potentially weeks at sea. Anyone know?
  - ianburrell 2y ago
    Container ships do provide power to refrigerated containers. My understanding is that refrigerated containers are in row with the door accessible and power hookup. I was looking at photo of the row, and how container ships have extra power system to power them. It looked like it was far down with stacks of containers around and presumably on top.
  - throwup238 2y ago
    They do but most reefers (refrigerated containers) have build in or portable gensets to provide power when they’re not on the ship and plugged in. They could easily spend days in the port stacks and having to plug them in every time they moved would make life a lot more difficult for the port. They can burn anywhere from a few hundred to a few thousand liters of diesel per week which isn’t actually that much to a 40ft shipping container.
    - dmurray 2y ago
      It sounds like these are automated somehow, that the generator kicks in when it's not otherwise being powered - otherwise isn't it just as much work for the port to run around starting and stopping generators? But an automated system sounds like it has its own problems, how does it make sure it has proper ventilation and comes on at the right time? Probably I don't want the container to start venting diesel fumes when it's deep in a stack of lego surrounded on all sides.
      - throwup238 2y ago
        Reefers still get special treatment at ports because they have to be moved as quickly as possible. That includes not stacking them several layers deep horizontally so that ventilation is blocked (the gensets are very obvious from the outside). They’ll often get connected while in the port too, it’s just not a guarantee. Someone with more valuable produce will often pay for preferable treatment and a power connection to reduce risk from malfunction and running out of fuel. It has to be automated since it’s a refrigeration unit that needs to know when to turn on the cooler. The control circuit starts up the generator if it senses no power connection at that time, usually off a standard marine lead acid battery.
    - namibj 2y ago
      How important do you think would a grid hookup be on European freight trains for reefers? It should be straight forward to include full wagon power with the upcoming DAC4EU coupling (UIC 552 says that normal coaches are to have an 800A through connection that's regularly fed with 1000V 16.7Hz or 1500V 50Hz; this is single-wire earth(/track)-return). Keep in mind that unlike North American freight trains, Europe mainline service is almost fully electrified. Thus the reefer would be grid-fed. I'm asking because I'm looking to propose a change to the current plans for the electric coupler (use near-field RF instead of the currently-preferred single-pair Ethernet or it's fallback powerline; I think 802.11 has suitable PHY options, especially among the OFDM codes if the near-field chamber is dispersive and/or has problematic resonances in the channel), and throwing in "grid power for reefers" with actual numbers from the reefer container industry would be easy (a change to the coupler is a change, and the additional cable through the wagon shouldn't be that extensive either if it's an economical aluminum type; also this would allow passenger coaches that are currently using the pre-DAC4EU hook and chain coupling to be used with DAC4EU rolling stock).
- akira2501 2y ago
  That generator is for very short periods of time spent in transit. Once it's on the ship it's directly connected to ships power. This also has implications for it's placement as not all rows of stacks on a ship have power cables run out to them. Also, because of the short time requirement, and some extreme low temperature requirements on some cargo, it needs to be in a place where it can be disconnected and very quickly craned off the ship. The engineer making and breaking the connections will generally have to manually log the time of these actions and the time of the unload. It's all a very interesting and somewhat complicated process. [0]: https://www.youtube.com/watch?v=U75MZwtDCXA https://www.youtube.com/watch?v=U75MZwtDCXA
Terr_ 2y ago
> -heavier containers at the bottom for stability In the same vein, port /starboard / bow / stern balance. > -containers to be unloaded first near the top Containers with the same destination in separate places so that multiple cranes can run in parallel without infringing on each other's work-zones. Truly an interesting project for people who get stuck trying to optimize too many things at once. :p
- raverbashing 2y ago
  And there's also regulation IIRC dictating that more hazardous material should be packed at the center of the ship, to avoid falling off in case of accident.
  - mcguire 2y ago
    Don't store some classes of hazardous materials near specific other classes of hazardous materials (keep your oxidizers away from the fuels), don't carry too much hazardous material, keep good records of what's in each container and where that container is...
- smarm52 2y ago
  Wow, that's a great insight. Not only how to pack optimally, but how to balance the load. Then not just balance the load for shipping, but also to optimize packing the load. Sort of like torquing the lug-nuts on tires one at a time to avoid tipping the car.
uoaei 2y ago
Computer scientists are always so concerned with optimality. IMO it is sufficient to know an optimum exists and a way to converge on the solution, then finding quasi-optimal solutions is more than good enough.
- cerved 2y ago
  Not at all. Plenty of people are researching finding satisfiable solution that are quasi-optimal at scale. Once you reach a certain scale of optimization problem, proven optimality in a reasonable time-frame is often infeasible
  - uoaei 2y ago
    I'm not talking about academics I'm talking about your coworkers.
huygens6363 2y ago
Compared to.. protein folding, nuclear fusion? Sounds like a handful of parameters to me. What are computers good for if not looking for solutions in this space? It's strange to me that the cargo space has not been aggressively optimized. It's a pretty substantial part of civilization and, I believe, there's definitely some money sloshing around there.
- hermitcrab 2y ago
  A Panamax can carry ~5000 containers. 5000! (5000 factorial) is a BIG number. Bear in mind that 60! is more than the number of atoms in the observable universe. Combinatorial problems are hard.
  - pineaux 2y ago
    This is if you are looking in an naive way and are only interested in for THE BEST solution. However, there are many constraints and we are looking for a better solution not the best one.
    - smarm52 2y ago
      Yes exactly, I'm reminded of solutions to find numerical approximation results for very difficult problems like this. One of the most famous are Markov chain approaches to resolving similar issues. Then, for the interested: https://en.wikipedia.org/wiki/Markov_chain https://en.wikipedia.org/wiki/Markov_chain
  - huygens6363 2y ago
    For some reason, ignorance most likely, I'm not impressed. Looks relatively easy. Not for me, but for anybody with some math skills it looks easy to improve upon naive solutions. To be fair, a completely optimal solution definitely seems out of reach, but I'm not interested in those.
    - saagarjha 2y ago
      The constraints are not always easily evident, unfortunately.
Shrezzing 2y ago
There's quite a lot of other constraints too. Lots of goods aren't allowed to sit side-by-side, for example, anything explosive goods cannot sit within n containers of hazardous chemicals. Because goods codification is so low-fidelity, lots of things which aren't actually explosive/hazardous can't be stored in close proximity, because we can't differentiate them from things which are actually hazardous/explosive.
mcguire 2y ago
It's very much wackier than that. In addition to mere physical constraints, there are the laws and regulations of individual countries and a goodly stack of international treaties and standards.
- smarm52 2y ago
  Wow, that's an entirely different set of constraints that I hadn't considered. I have a whole new respect for logistics professionals that handle that sort of thing.

IncreasePosts 2y ago

All of the refrigerated containers I have seen have had a built in generator/AC unit...why would shippers care about heat loss, unless they are providing the energy to refrigerate the containers?

hermitcrab 2y ago
I assume the shippers are providing the power for refrigerated containers. Otherwise they would need to have batteries or fuel that could last potentially weeks at sea. Anyone know?
- ianburrell 2y ago
  Container ships do provide power to refrigerated containers. My understanding is that refrigerated containers are in row with the door accessible and power hookup. I was looking at photo of the row, and how container ships have extra power system to power them. It looked like it was far down with stacks of containers around and presumably on top.
- throwup238 2y ago
  They do but most reefers (refrigerated containers) have build in or portable gensets to provide power when they’re not on the ship and plugged in. They could easily spend days in the port stacks and having to plug them in every time they moved would make life a lot more difficult for the port. They can burn anywhere from a few hundred to a few thousand liters of diesel per week which isn’t actually that much to a 40ft shipping container.
  - dmurray 2y ago
    It sounds like these are automated somehow, that the generator kicks in when it's not otherwise being powered - otherwise isn't it just as much work for the port to run around starting and stopping generators? But an automated system sounds like it has its own problems, how does it make sure it has proper ventilation and comes on at the right time? Probably I don't want the container to start venting diesel fumes when it's deep in a stack of lego surrounded on all sides.
    - throwup238 2y ago
      Reefers still get special treatment at ports because they have to be moved as quickly as possible. That includes not stacking them several layers deep horizontally so that ventilation is blocked (the gensets are very obvious from the outside). They’ll often get connected while in the port too, it’s just not a guarantee. Someone with more valuable produce will often pay for preferable treatment and a power connection to reduce risk from malfunction and running out of fuel. It has to be automated since it’s a refrigeration unit that needs to know when to turn on the cooler. The control circuit starts up the generator if it senses no power connection at that time, usually off a standard marine lead acid battery.
  - namibj 2y ago
    How important do you think would a grid hookup be on European freight trains for reefers? It should be straight forward to include full wagon power with the upcoming DAC4EU coupling (UIC 552 says that normal coaches are to have an 800A through connection that's regularly fed with 1000V 16.7Hz or 1500V 50Hz; this is single-wire earth(/track)-return). Keep in mind that unlike North American freight trains, Europe mainline service is almost fully electrified. Thus the reefer would be grid-fed. I'm asking because I'm looking to propose a change to the current plans for the electric coupler (use near-field RF instead of the currently-preferred single-pair Ethernet or it's fallback powerline; I think 802.11 has suitable PHY options, especially among the OFDM codes if the near-field chamber is dispersive and/or has problematic resonances in the channel), and throwing in "grid power for reefers" with actual numbers from the reefer container industry would be easy (a change to the coupler is a change, and the additional cable through the wagon shouldn't be that extensive either if it's an economical aluminum type; also this would allow passenger coaches that are currently using the pre-DAC4EU hook and chain coupling to be used with DAC4EU rolling stock).
akira2501 2y ago
That generator is for very short periods of time spent in transit. Once it's on the ship it's directly connected to ships power. This also has implications for it's placement as not all rows of stacks on a ship have power cables run out to them. Also, because of the short time requirement, and some extreme low temperature requirements on some cargo, it needs to be in a place where it can be disconnected and very quickly craned off the ship. The engineer making and breaking the connections will generally have to manually log the time of these actions and the time of the unload. It's all a very interesting and somewhat complicated process. [0]: https://www.youtube.com/watch?v=U75MZwtDCXA https://www.youtube.com/watch?v=U75MZwtDCXA

Terr_ 2y ago

> -heavier containers at the bottom for stability In the same vein, port /starboard / bow / stern balance. > -containers to be unloaded first near the top Containers with the same destination in separate places so that multiple cranes can run in parallel without infringing on each other's work-zones. Truly an interesting project for people who get stuck trying to optimize too many things at once. :p

raverbashing 2y ago
And there's also regulation IIRC dictating that more hazardous material should be packed at the center of the ship, to avoid falling off in case of accident.
- mcguire 2y ago
  Don't store some classes of hazardous materials near specific other classes of hazardous materials (keep your oxidizers away from the fuels), don't carry too much hazardous material, keep good records of what's in each container and where that container is...
smarm52 2y ago
Wow, that's a great insight. Not only how to pack optimally, but how to balance the load. Then not just balance the load for shipping, but also to optimize packing the load. Sort of like torquing the lug-nuts on tires one at a time to avoid tipping the car.

uoaei 2y ago

Computer scientists are always so concerned with optimality. IMO it is sufficient to know an optimum exists and a way to converge on the solution, then finding quasi-optimal solutions is more than good enough.

cerved 2y ago
Not at all. Plenty of people are researching finding satisfiable solution that are quasi-optimal at scale. Once you reach a certain scale of optimization problem, proven optimality in a reasonable time-frame is often infeasible
- uoaei 2y ago
  I'm not talking about academics I'm talking about your coworkers.

huygens6363 2y ago

Compared to.. protein folding, nuclear fusion? Sounds like a handful of parameters to me. What are computers good for if not looking for solutions in this space? It's strange to me that the cargo space has not been aggressively optimized. It's a pretty substantial part of civilization and, I believe, there's definitely some money sloshing around there.

hermitcrab 2y ago
A Panamax can carry ~5000 containers. 5000! (5000 factorial) is a BIG number. Bear in mind that 60! is more than the number of atoms in the observable universe. Combinatorial problems are hard.
- pineaux 2y ago
  This is if you are looking in an naive way and are only interested in for THE BEST solution. However, there are many constraints and we are looking for a better solution not the best one.
  - smarm52 2y ago
    Yes exactly, I'm reminded of solutions to find numerical approximation results for very difficult problems like this. One of the most famous are Markov chain approaches to resolving similar issues. Then, for the interested: https://en.wikipedia.org/wiki/Markov_chain https://en.wikipedia.org/wiki/Markov_chain
- huygens6363 2y ago
  For some reason, ignorance most likely, I'm not impressed. Looks relatively easy. Not for me, but for anybody with some math skills it looks easy to improve upon naive solutions. To be fair, a completely optimal solution definitely seems out of reach, but I'm not interested in those.
  - saagarjha 2y ago
    The constraints are not always easily evident, unfortunately.

Shrezzing 2y ago

There's quite a lot of other constraints too. Lots of goods aren't allowed to sit side-by-side, for example, anything explosive goods cannot sit within n containers of hazardous chemicals. Because goods codification is so low-fidelity, lots of things which aren't actually explosive/hazardous can't be stored in close proximity, because we can't differentiate them from things which are actually hazardous/explosive.

mcguire 2y ago

It's very much wackier than that. In addition to mere physical constraints, there are the laws and regulations of individual countries and a goodly stack of international treaties and standards.

smarm52 2y ago
Wow, that's an entirely different set of constraints that I hadn't considered. I have a whole new respect for logistics professionals that handle that sort of thing.