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Reducing the fuel consumption of ships
Georgeb
10 Posts
Question

We could greatly reduce the fuel consumption and emissions of ships if we used the energy of waves. This could done by adding a pipe all the way around the ship above sea level. Water enters the pipe at the bow and exits at the stern to push the ship forward. The pipe is higher and wider at the bow than the stern. Waves force water into one way openings at the bow to give pressurised water with potential energy. This pressurised water forces jets of water out at the stern.

All the pipework is above sea level so ships could be retroftted without the need to go into dry docks. There is no change to the laminar flow of water below sea level.

The motion of the ship adds to the kinetic energy of waves. By diverting this energy around the ship we can reduce drag and fuel consumption. This would be a low cost way to reduce greenhouse gas emissions without the need for people to reduce their standards of living.

17 Replies
mapj1
4166 Posts

Do you have any evidence that this idea works ? - to demonstrate a scale model would be very interesting.

 

Mike.

Georgeb: 
 

We could greatly reduce the fuel consumption and emissions of ships if we used the energy of waves…... 

There is no change to the laminar flow of water below sea level.

This is contradictory. If the pipe is able to take in water at the bow, it must be below the level of the water, and therefore affecting the flow of water round the hull. The amount of energy available from this would be minimal, bearing in mind the engine power required to propel the ship (for a large ship we are talking of tens of MW) and the drag would cause more losses than would be gained.

For a small ship, the bow would pitch up with the waves and the system might not take on any water anyway.

I think if you want to reduce fuel consumption on ships it can be done by utilising wind power. There is, after all, a correlation between the height of the waves and the power of the wind. If we were to fit tall masts on the ships with horizontal bars and hang large squares of canvas to be driven by the wind, this might work……. 

mapj1
4166 Posts

now you mention it something like that has been done. But squares are not always the best shape unless you want to run from the wind.

Ah yes, that's probably what you are thinking of.

 

KiwiBuzz
4 Posts

Nuclear ships is the obvious answer.

Georgeb
10 Posts

The last time I looked the bow of a ship was above sea level. Due to the motion of the ship,  waves will strike the ship at the pointed front end rather than the sides. Wave energy is more concentrated and available for more of the time than wind energy. The plumbing necessary to capture wave energy would be a lot cheaper than using masts and sails and would be much  easier to operate.

Wave energy is equal parts potential energy and kinetic energy. When a wave strikes a wall such as the side of a ship the kinetic energy is transformed into pressure energy and more potential energy plus friction losses. This pressure and potential energy can be piped to the rear of the ship to be reconverted to jets of kinetic energy to push the ship forward.

Waves have potential energy so all the pipework to capture it is above sea level. There is no impediment to flows below sea level to increase drag.

There will be less energy lost by the ship forming bow waves.

DavidS
2 Posts

I'm not a naval architect, but…

When the waves hit the bow of the ship, they are forced into constricted openings. This increases the pressure of the water (compared to a sharp bow cutting through the wave), pushing back on the ship.

Interesting idea, but I suspect that it would create more drag than the propulsive force that it generates.

Georgeb
10 Posts
When a wave hits a ship it causes drag because the ship has to expend energy to push the water to the sides. If some of this water and its pressure and potential energy  is channelled to the rear to be reconverted to kinetic energy, the energy losses to the sides can be reduced. The ship has to expend the same amount of energy to push against the wave but it will recover some of the energy that is channelled to the rear rather than lost to the sides.
Mik3_Pog
1 Posts

An interesting concept.

Would the addition of a pipe to the ship not ruin it's streamlined design and introduce more drag and increase the power requirement to move through the water? I'm thinking that the bow is rather smooth and sharp to cut through the water more easily.

I also think that a ‘passive pipe’ wouldn't be very useful for propulsion. I use the phrase ‘passive pipe’ as opposed to that of say a jetski where water is forced through. What about adding a dynamo into the pipe to generate power from the water rushing through it (assuming that water does enter the pipe)?

Could we perhaps tow a series of turbines behind the ship which generate electricity? (Again adding drag, of course)

I'm no expert (not even an amateur really), just my stream of thought…

The waves are not ‘hitting the ship’ since they are transverse waves - the water itself merely moves up and down. What is actually happening is the ship is hitting the waves - I am of course referring to the behaviour of waves in deep sea rather than in shallow water close to shore where the action of the water does change.

In hitting the waves the ship is losing energy and adding pipes would result in more energy being lost due to the reduction in streamlining. We are battling with the second law of thermodynamics here and I can't see a way that we can get more energy than is being lost. However if anyone wants to do a study with a model and a tank I would be interested in seeing the results - just don't ask me to contribute to the cost.

Hi,
Shipping companies calculate CO 2 emissions based on the simple formula "fuel consumption times emission factor". So the task is to measure the amount of fuel consumed. However, it is not as simple as it seems at first glance. A ship carries various types of fuel used in main engines, auxiliary engines, gas turbines, boilers or inert gas generators. Consumption scenarios range from the exclusive access of one consumer to one type to the simultaneous access of several consumers to one type. The fuels are fed to the consumers through ring lines, i.e. fuel that is not used strangely back to the tank or tank. In addition, some of the types have to be pumped between different containers to balance the ship. Complexity of the fuel system
Based on Regulation 2015/757, since 2019 shipping companies have been required to submit a report on CO 2 emissions and other relevant information to the relevant Commission and flag authorities until 30 April each year for each ship under their responsibility. This report is transmitted through automated systems and exchange formats data.
Most ships consume significantly less fuel per tonne of fuel compared to trucks or trains. However, the values ​​can vary greatly depending on the size of the ship or truck. Example: Container ships (3,000-8,000 TEU) emit about 17 grams of CO 2 per tonne-kilometer (tkm), while a truck (truck / truck 24-40 tons, average goods) emits around 68 grams / km / h.
Vehicle fuel consumption per hour, depending on speed, Calculate and leaves with the following function: And (x) = 1, 4 + 0, 0025 X3 where: X .. Speed ​​in SM / h (nautical miles per hour) f (x) .. Diesel consumption in tons Which speed x should the captain choose if he wants to use the amount of fuel for at least 800 nm (nautical miles)? I can not move forward .. my thoughts: The faster the ship travels, the more it takes per hour, but it takes fewer hours to 800 nautical miles, so there are two interrelated functions.
Vehicle fuel consumption per hour, depending on speed, Calculate and leaves with the following function: And (x) = 1, 4 + 0, 0025 X3 where: X .. Speed ​​in SM / h (nautical miles per hour) f (x) .. Diesel consumption in tons Which speed x should the captain choose if he wants to use the amount of fuel for at least 800 nm (nautical miles)? I can not move forward .. my thoughts: The faster the ship travels, the more it takes per hour, but it takes fewer hours to 800 nautical miles, so there are two interrelated functions. 1. Solve the formula v = s / t for t .. t = 800 / v ... so in our case 800 / x 2. Full consumption = t * Hourly consumption so G (t) = t * f (x) 3. It becomes G (x), which is then tested to a minimum, I reach x min = 6.542 sm / h, then the total consumption is the lowest with 256.8 t

Canvas? Dear me! How about Flettner rotors? Said to save 25%. 

2ecea85ea2a50ab9899df437b2066cec-origina
Enercon's E-Ship-1

Sorry, forgot the photographer. Lpele CC BY-SA 4.0, from the German WWW page on E-Ship 1.

Flettner rotors are being seriously considered on a number of projects, though the 25% saving is going to be under ideal conditions (ship with a lowish speed, so low power, with the wind directly from the side). The benefits are only when the wind is from the side, so say 50% of the time, and for 25% of the time with the wind from ahead the rotors will add to the fuel consumption due to the extra wind resistance. They also need power to operate and can cause issues with stability in high winds and provide little (or no) benefit when the wind is low. They also are impractical for some ship types.

Please note I am in favour of them, but we must be realistic about how much benefit they provide.

mapj1
4166 Posts

Peter Bernard Ladkin: 
 

Sorry, forgot the photographer. Lpele CC BY-SA 4.0, from the German WWW page on E-Ship 1.

That's a fantastic machine. 25m high cylinders 4m diameter doing up to 300 RPM.

That is a surface speed on the cylinders of ~ 60 metres per second at full chat !! Finger nipping good.  I assume the bottom bit is fenced off.

I wonder how noisy it is and if the gyroscopic effects make it hard to turn the ship..

Mike

Georgeb
10 Posts

I am proposing we recover some of the energy lost to the production of bow waves and moving the ship up and down and from side to side, by diverting the energy to kinetic energy at the rear. There is no change to the smooth flows below sea level. There is no extra drag at the bow  as water applies pressure against the one way openings  rather than the side of the ship. The pipes on the side of the ship are raised to minimise drag losses.

Georgeb
10 Posts

There is of course the option to increase the speed of the ship in rough seas for the same amount of fuel consumption by utilising wave energy. As there would be less movement of the ship up and down the journey would be smoother.

Simon Barker
968 Posts

Have you actually done any modelling of this idea yet. Either computational fluid dynamics, or a model boat in a wave tank?

Until you know how much propulsion you're going to get out of it, you aren't going to attract much interest.

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