Is LNG Fuel a good idea?

[Heidi13]

Trucks and buses typically run on straight LNG, but this requires a spark plug for ignition.

 

Almost all marine diesels that are LNG capable are "dual fuel" and can run on LNG, diesel, or residual fuel (and some can even run on crude oil), and the mixture between liquid fuel and gaseous fuel is infinitely variable between 0% gas to about 98% gas without requiring a spark ignition. This is one reason I think the ships will get away with limited bunkering facilities, is that once outside the US ECA, they will switch from LNG to diesel or residual fuel that still meets the emissions requirements outside an ECA. It takes about 3 times the volume of LNG to produce the same energy as diesel or residual fuel, so I've never been convinced of where they intend to store all this LNG if they intend on running on straight LNG.

 

The auto-ignition temperature of diesel or residual fuel is around 250*C (temperature at which it will burn without a flame or spark present), while natural gas is around 530*C. So, a little diesel in the fuel mixture when sprayed into the hot air in the diesel's cylinders, will provide the "spark" to start the natural gas burning.

 

I asked these questions when I went back to my old ship to check out the LNG conversion. I asked about the dual fuel and they confirmed that a small amount of diesel is sprayed in to get the LNG to ignite. Being secured for 7 hrs every night means they have a significant window for bunkering, so the volume of LNG required is not an issue. Total HP is significantly less than modern cruise ships at just over 20,000 HP.

 

In addition to emissions, the primary driver for switching to LNG was fuel cost. In only the 2nd month of operation, the month fuel bill is significantly reduced and the pay back is much shorter than I anticipated.

[bob brown]

Yeah, I've always thought this would be a chicken and egg situation. And Carnival blinked and made their commitment to Shell, with a good sweetener in it, I'm sure. Logistics for this is difficult in Europe, and they have a lot of LNG export facilities over there, way more than we do. I think that after about the first cruise to keep the hype up, they will start going to blended operation, only using a percentage of LNG until the infrastructure ramps up to meet demand.

Part of this hype is just "good corporate citizen" P. R. I suppose there is some measure of value to that, for them....

[Enforcer]

Hi,

 

As somebody who has found this thread very interesting, I would like to point out that I have no knowledge of this subject apart from what I have just read.

 

My question is, which may be seen as a bit daft is - can existing cruise ships be converted to this type of energy, is it feasible/possible or even cost effective?

 

Cheers

Pete

[chengkp75]

Hi,

 

As somebody who has found this thread very interesting, I would like to point out that I have no knowledge of this subject apart from what I have just read.

 

My question is, which may be seen as a bit daft is - can existing cruise ships be converted to this type of energy, is it feasible/possible or even cost effective?

 

Cheers

Pete

 

Engines: some of the newer engines could be modified to run on dual fuel, older ones would need to be replaced.

Fuel handling systems: Addition of cryogenic system and liquifaction equipment and added safety monitoring of the fuel system. Doubling up on the fuel system piping (liquid fuel and gaseous fuel).

 

Tankage: Here's the big one. Liquid fuel tanks are merely spaces that are part of the hull, with 6 steel sides, a vent, a pipe to fill and a pipe to empty. LNG tanks cannot be integral with the hull, cannot be placed on the sides of the ship like liquid tanks are, require insulation around them, and take up about 6 times the volume, for a given amount of heat energy from the fuel, as liquid fuel requires.

 

So, in reality, it's highly unlikely that any current cruise ship will be converted to LNG, as it would be far too costly to basically rip out the entire engineering space to install the LNG equipment and tankage. Plus, it would take up a lot of "real estate" and there isn't a lot of unused space on most ships. Smaller vessels like ferries, with smaller fuel requirements have been converted (as Heidi has mentioned), there are several in Norway, but this consists of placing LNG storage tanks out on deck (don't think that would go over on a cruise ship) to eliminate a lot of the problems mentioned above, as well as the real estate issue.

[chengkp75]

I asked these questions when I went back to my old ship to check out the LNG conversion. I asked about the dual fuel and they confirmed that a small amount of diesel is sprayed in to get the LNG to ignite. Being secured for 7 hrs every night means they have a significant window for bunkering, so the volume of LNG required is not an issue. Total HP is significantly less than modern cruise ships at just over 20,000 HP.

 

In addition to emissions, the primary driver for switching to LNG was fuel cost. In only the 2nd month of operation, the month fuel bill is significantly reduced and the pay back is much shorter than I anticipated.

 

Yes, the cost savings depends on the market. What I've seen is that LNG (per Mj of energy) provides a significant savings in the US (offset of course by the capital expense), slightly less savings in Europe, and very little to no savings in Asia. This is all due to availability of and demand for LNG and liquid fuels, regardless of the infrastructure investment in bunkering equipment.

[Enforcer]

Engines: some of the newer engines could be modified to run on dual fuel, older ones would need to be replaced.

Fuel handling systems: Addition of cryogenic system and liquifaction equipment and added safety monitoring of the fuel system. Doubling up on the fuel system piping (liquid fuel and gaseous fuel).

 

Tankage: Here's the big one. Liquid fuel tanks are merely spaces that are part of the hull, with 6 steel sides, a vent, a pipe to fill and a pipe to empty. LNG tanks cannot be integral with the hull, cannot be placed on the sides of the ship like liquid tanks are, require insulation around them, and take up about 6 times the volume, for a given amount of heat energy from the fuel, as liquid fuel requires.

 

So, in reality, it's highly unlikely that any current cruise ship will be converted to LNG, as it would be far too costly to basically rip out the entire engineering space to install the LNG equipment and tankage. Plus, it would take up a lot of "real estate" and there isn't a lot of unused space on most ships. Smaller vessels like ferries, with smaller fuel requirements have been converted (as Heidi has mentioned), there are several in Norway, but this consists of placing LNG storage tanks out on deck (don't think that would go over on a cruise ship) to eliminate a lot of the problems mentioned above, as well as the real estate issue.

 

Thanks for the response, very clear and appreciated.

 

Pete

[Heidi13]

Hi,

 

As somebody who has found this thread very interesting, I would like to point out that I have no knowledge of this subject apart from what I have just read.

 

My question is, which may be seen as a bit daft is - can existing cruise ships be converted to this type of energy, is it feasible/possible or even cost effective?

 

Cheers

Pete

 

While never impossible, I would say highly unlikely, as existing cruise ships have really no space for the fuel tank. Further to Cheng's explanation it would raise stability issues, as effectively they are raising the KG (height) of a significant weight.

 

My old ship was easily converted as it previously carried no fuel in the double bottoms and has a large void space between the tank top and car deck, where the insulated tank was installed.

[chengkp75]

While never impossible, I would say highly unlikely, as existing cruise ships have really no space for the fuel tank. Further to Cheng's explanation it would raise stability issues, as effectively they are raising the KG (height) of a significant weight.

 

My old ship was easily converted as it previously carried no fuel in the double bottoms and has a large void space between the tank top and car deck, where the insulated tank was installed.

 

Yes, I think that the LNG cruise ships are increasing their inner bottom height from 2 mtr to 3 mtr, and placing the LNG tanks in the inner bottom, in machinery areas not directly under the engines (to reduce heating). By class, the tanks can't be along the sides, or within 1/4 of the beam from the side. Doing this to an existing ship would cost almost as much as a new ship. Very similar to what your ship did with a void space, again keeping the weight down low.