3 ms·

Cars have regenerative breaking which is a help in urban areas. Ships tend to go not change course nearly as much on a several day journey. I guess a propellor

by zeristor 10mo ago

Cars have regenerative breaking which is a help in urban areas. Ships tend to go not change course nearly as much on a several day journey. I guess a propellor could run in reverse for regenerative breaking, but it wouldn’t help much.

dyauspitr 10mo ago
Wind, large surface area for solar Also wave based generators that could also act as dampers/suspension and they wouldn’t steal energy from forward motion like wind would (depending on if you’re generating wind energy or using wind to buttress the batteries). Ideally a combination of sails coupled with batteries and wave generators sounds like it would be very energy efficient.
- jacquesm 10mo ago
  Solar on board of cargo vessels is a pipe dream, as is 'wave based generation'.
tmountain 10mo ago
Isn’t regenerative braking reclaiming otherwise wasted energy from necessary deceleration? Running the propeller in reverse would result in having to apply equal or greater energy to regain the current speed, so it’s a net loss of energy if I’m understanding the suggestion properly.
jacquesm 10mo ago
Ships are subject to so much drag that this is rarely a problem, only in emergency situations and there is not much that you can do to stop a vessel that weighs 100,000 tons or more except to run your engines in reverse and start praying to your deity. Regenerative braking for boats would be a complete waste. There are some vessels that have single use emergency brakes, but the latest trend is to have motor 'pods' that are electrical and that can be used both for normal propulsion as well as to perform emergency stops that are quite impressive given the size of the vessels they are on. Typically an oceangoing vessel requires at least 3, but commonly 5 to 10 ship lengths to come to a full stop from moving forward under power. This is not necessarily because of limitations of the propulsion unit, but simply because stopping that much tonnage too fast would do as much damage as a collision would. With classical engines there is far more rotating mass so it would take much longer than with electrical propulsion to react before the beginning of the braking phase.
- NewJazz 10mo ago
  Regenerative braking for boats would be a complete waste. Unless you have a large sail to generate thrust to spin the propeller...
  - lostlogin 10mo ago
    It’s a pity that the sail isn’t also PV solar.
- VBprogrammer 10mo ago
  Pods are used primarily for manoverability. This allows Cruise ships to get in and out of ports with a minimum of assistance (none at all, if conditions permit). This is important because they are entering and leaving ports every day or two. It also makes sense as the hotel loads on these floating skyscrapers is similar to the propulsion loads so having combined main engines and generators gives other advantages. Ocean going container vessels on the other hand use massive direct drive two stroke diesel engines (usually they only have a single engine). They have no gearbox. The only way to go-astern is to literally start the engine in reverse. This can only be done up to a limited speed, otherwise the windmilling effect of the water passing through the prop would overpower the starting air. Suffice to say, I'd put a long bet on the overwhelming majority of containerships being powered by internal combustion engines in 30 years time. If we get our act together we might have come up with an alternative / synthetic fuel by then but I wouldn't hold my breath.
  - jacquesm 10mo ago
    > Pods are used primarily for manoverability. Check out the https://swzmaritime.nl/news/2022/11/08/how-abbs-braking-system-automates-a-cruise-ships-emergency-stops/ https://swzmaritime.nl/news/2022/11/08/how-abbs-braking-syst... 'wonder of the seas' e-brake system.
    - VBprogrammer 10mo ago
      It's interesting but it's just an automated system build on top of the existing pod drive architecture which is there for the reasons I suggested. Interestingly, there are situations in which it might be helpful where it wouldn't have worked. For example, the Francis Scott Key Bridge incident. The vessel suffering from a blackout caused by a transformer being tripped by a single loose wire.
tshaddox 10mo ago
Not changing course is good though. Regenerative braking is only good because it increases the efficiency when you absolutely must slow down, but it would always be more efficient to slow down less.

dyauspitr 10mo ago

Wind, large surface area for solar Also wave based generators that could also act as dampers/suspension and they wouldn’t steal energy from forward motion like wind would (depending on if you’re generating wind energy or using wind to buttress the batteries). Ideally a combination of sails coupled with batteries and wave generators sounds like it would be very energy efficient.

jacquesm 10mo ago
Solar on board of cargo vessels is a pipe dream, as is 'wave based generation'.

tmountain 10mo ago

Isn’t regenerative braking reclaiming otherwise wasted energy from necessary deceleration? Running the propeller in reverse would result in having to apply equal or greater energy to regain the current speed, so it’s a net loss of energy if I’m understanding the suggestion properly.

jacquesm 10mo ago

Ships are subject to so much drag that this is rarely a problem, only in emergency situations and there is not much that you can do to stop a vessel that weighs 100,000 tons or more except to run your engines in reverse and start praying to your deity. Regenerative braking for boats would be a complete waste. There are some vessels that have single use emergency brakes, but the latest trend is to have motor 'pods' that are electrical and that can be used both for normal propulsion as well as to perform emergency stops that are quite impressive given the size of the vessels they are on. Typically an oceangoing vessel requires at least 3, but commonly 5 to 10 ship lengths to come to a full stop from moving forward under power. This is not necessarily because of limitations of the propulsion unit, but simply because stopping that much tonnage too fast would do as much damage as a collision would. With classical engines there is far more rotating mass so it would take much longer than with electrical propulsion to react before the beginning of the braking phase.

NewJazz 10mo ago
Regenerative braking for boats would be a complete waste. Unless you have a large sail to generate thrust to spin the propeller...
- lostlogin 10mo ago
  It’s a pity that the sail isn’t also PV solar.
VBprogrammer 10mo ago
Pods are used primarily for manoverability. This allows Cruise ships to get in and out of ports with a minimum of assistance (none at all, if conditions permit). This is important because they are entering and leaving ports every day or two. It also makes sense as the hotel loads on these floating skyscrapers is similar to the propulsion loads so having combined main engines and generators gives other advantages. Ocean going container vessels on the other hand use massive direct drive two stroke diesel engines (usually they only have a single engine). They have no gearbox. The only way to go-astern is to literally start the engine in reverse. This can only be done up to a limited speed, otherwise the windmilling effect of the water passing through the prop would overpower the starting air. Suffice to say, I'd put a long bet on the overwhelming majority of containerships being powered by internal combustion engines in 30 years time. If we get our act together we might have come up with an alternative / synthetic fuel by then but I wouldn't hold my breath.
- jacquesm 10mo ago
  > Pods are used primarily for manoverability. Check out the https://swzmaritime.nl/news/2022/11/08/how-abbs-braking-system-automates-a-cruise-ships-emergency-stops/ https://swzmaritime.nl/news/2022/11/08/how-abbs-braking-syst... 'wonder of the seas' e-brake system.
  - VBprogrammer 10mo ago
    It's interesting but it's just an automated system build on top of the existing pod drive architecture which is there for the reasons I suggested. Interestingly, there are situations in which it might be helpful where it wouldn't have worked. For example, the Francis Scott Key Bridge incident. The vessel suffering from a blackout caused by a transformer being tripped by a single loose wire.

tshaddox 10mo ago

Not changing course is good though. Regenerative braking is only good because it increases the efficiency when you absolutely must slow down, but it would always be more efficient to slow down less.