Guide to fuel conservation

Ducimus · 07-29-07, 09:36 PM

Fuel consumption, and its conservation is actually a big part of the game, and i believe a part that is not fully understood by everyone.

First, lets get the basics out of the way:

Things that lower your fuel capacity

- Damaged fuel tanks (obviously)

- Recharging batteries

- Battery damage. ( Once a battery is damaged the game doesn't always turn "recharge mode" off, and you have to do this manually, the kicker is, you may not always realize it, so always make sure you CE goes back to normal running after a battery charge)

- High speeds chases

- Putting around at excessively low speeds.

Things that effect your total surface endurance

- the state of the sea. High waves and wind will hinder you on the surface.

A bit more on charging batteries

In SH3, when you were recharging your batteries one of your two engines was taken off propulsion and switched to charge the batteries, and thats all it did. While doing so, this engine would be running at an RPM equivlant to flank speed. While i'm unsure exactly how engine configurations in SH4 handle the charge, it is reasonable to assume that while charging your batteries, you have one or more engines running at a higher than normal RPM, this takes fuel.

With this in mind, you would do well to conserve your batteries when you can by running at lower submerged speeds. With patch 1.3, assuming your running TMaru, battery recharge time averages around 6 to 7 hours. Running submerged at 2 kts uses less batteries then running submerged at 3 kts. Running submerged saves fuel, so long as you keep your battery expenditure to a minium to reduce recharge requirements.

Midway and sub tenders...
Use them. Plan on using them, their there for a reason. Infact, if your a pearl harbor boat, you NEED midway. Any patrol route that leaves pearl harbor that does not figure in midway both when going to your patrol area, and coming back from your patrol area, is a failure. Asiatic fleet boats should count on the tenders which appear later in the war.

Ploting the first half of your patrol route
So you've left pearl harbor, and topped off your fuel tanks at midway, (Tmaru does this for you, but thats besides the point).

The first thing I should do, is take the ruler tool and plot a line from my current location near midway, to my patrol area. This gives me the most direct route. What i do then is zoom in the map and actually plot the course using the line(s) i just drew as a guide. The purpose being to make sure i don't run the boat aground on some small island or reef that does not appear on the map when zoomed out. You may also have to plot around some large islands, and you should *try* for the closest route to the line you drew, geography and ASW concerns should be part of your decision. Once i've plotted my course to my patrol area, i wlll go to AHEAD 2/3's, and while i wait for the boat to build up speed to around 8 or 9 kts, i proceed to my next step.

Plotting the second half of your patrol route
So the boats building up to a speed of 8-9 kts and while its doing so , i will go ahead and plot my course back from my patrol area to midway or whatever refueling point i will encounter before my home base. Having done that, and the boat at now my normal cruising speed, i start jabber jawing with my navigator.

"Hey Jim, whats the range to course end?"

"Eh, i calculate about its about 10,500 Nautical miles Rich".

"hmm, ok, at our current speed, how far do you think we'll go?"

"Given our current speed, i reckon we have enough fuel to travel about 14,500 NM, give or take"

"Ok, thanks jim".

Figuring out your actual patrol allowance
Patrol allowance is a term i give to how much fuel you have to actually operate on. In the above example, you have an estimate of about 14,500 nm, and your round trip ticket costs you 10,500 NM. That's just coming and going. This fuel is commited, theres no flexing here. So what you acutally have is 4,000 NM of fuel to operate on.

However, theres other factors to consider. Primarily Battery recharging and the weather, both of which will reduce your operational endurance. Given this, ill take my above data, and round up to compensate. So i fgure 11,000 NM to get to and from base, with a 14,000 NM endurance, which gives me 3,000 NM of fuel to work with. In the interests of giving myself a bit more flex for the return trip to make sure i can make it home, ill take 1,000 off of that. So in reality, i have an operational endurance of 2,000 NM. Thats ALL im giving it. If i push it more then that (and i could with that built in buffer), i endanger my ability to RTB.

Establishing when its time to RTB
The easiest and simplist way is to always be mindful of how far you are from the closest refueling point (midway in my case), and your maximum range at current speed is. If you have a maximum range of 6,500 NM, and you range to midway is 5,000 NM, its time to RTB! Always allow a buffer.

Being stingy with your operational fuel
So, now that we've established we have about 2,000 NM of actual fuel to play with, your going to encounter situations that will tax that, and your going to have to make decisions based on that.

For instance, is the target your pursing worth the fuel expenditure? Is that 2,000 ton freighter worth the fuel it would take to do an end around attack? Or would you hold your cards and hope 5,000 ton freighter?

Is a submerged approach more economical then a surfaced one?

etc etc, theres all sorts of hypotheticals.

Extending your stay in the area of operations
In short, in daylight, patrol submerged at the most battery economical speed of 1/3rd, or 1 to 2 kts. Use as little of your battery as possible, so you use less fuel recharging it, not to mention *some* fuel savings for having not used your diesals to begin with.

Now then, that clear as mud to ya all?

if you read all that and understood it, now you know why ive always been saying fuel is a big part of the sim, and If your running out of fuel, well, you made some wrong decisions captain, better brush up!

Ducimus · 07-29-07, 09:53 PM

edited a A BUNCH of times if you started reading it. I got over complex in some areas.

Go4It · 07-29-07, 10:30 PM

Never new SH4 had sub tenders, if so, were does one find one....

Iceman · 07-29-07, 10:58 PM

Very good advice thank you for the post.

Von Tonner · 07-29-07, 11:58 PM

Quote:

Originally Posted by Go4It

Never new SH4 had sub tenders, if so, were does one find one....

They are those striped anchors you see on the map. You can refuel and rearm at them but not effect any repairs. Just be careful, I have been attacked at one and sunk.

Thanks for that info Ducimus, I was under the false impression that the longer I stayed under travelling to assignment the more fue I saved. Now I see why I could never handle coming out of Pearl and resorted to always playing Asiatic Fleet. Thanks.

Ducimus · 07-30-07, 12:03 AM

Quote:

I was under the false impression that the longer I stayed under travelling to assignment the more fue I saved.

That was true in SH3, because the battery recharge only took around 3 hours. Now they take around 7 hours (give or take an hour). The 6-7 hour recharge being more realistic of course.

THE_MASK · 07-30-07, 03:07 AM

Thanks for this awesome fuel summary

.

PepsiCan · 07-30-07, 03:44 AM

Quote:

Originally Posted by Ducimus

Quote:

I was under the false impression that the longer I stayed under travelling to assignment the more fue I saved.

That was true in SH3, because the battery recharge only took around 3 hours. Now they take around 7 hours (give or take an hour). The 6-7 hour recharge being more realistic of course.

There's also plain physics involved. If you burn diesel to charge your battery for the energy value of 100 kilowatts, then you will not charge your battery for 100 kilowatts. A lot of energy (as much as 50%) will be lost in the form of heat, friction (resistance in the .

So, the cycle looks like this:
- you start with a full battery and you use up 50 Kilowatts to transport yourself 50 miles.
- you then need to burn a 100 kilowatt to recharge your batteries (50% energy loss)
- so, you actually used up twice the amount of diesel to cover those 50 miles then you would have had to use if you'd run on the surface.

Conclusion: running submerged is very inefficient due to the way the recharge process works.

Steeltrap · 07-30-07, 07:45 AM

Another thing to consider is this: do I have to go anywhere IN my patrol zone? In other words, having reached your patrol zone there is no actual need to go anywhere until you find a target or have one reported you wish to intercept. That's why I lie motionless on the surface in my patrol zone once I'm in a likely encounter position.

O'Kane did that in Tang...he said to lie to like that took some getting used to!

Frederf · 07-30-07, 04:03 PM

Quote:

Originally Posted by PepsiCan

Quote:

Originally Posted by Ducimus

Quote:

I was under the false impression that the longer I stayed under travelling to assignment the more fue I saved.

That was true in SH3, because the battery recharge only took around 3 hours. Now they take around 7 hours (give or take an hour). The 6-7 hour recharge being more realistic of course.

There's also plain physics involved. If you burn diesel to charge your battery for the energy value of 100 kilowatts, then you will not charge your battery for 100 kilowatts. A lot of energy (as much as 50%) will be lost in the form of heat, friction (resistance in the .

So, the cycle looks like this:
- you start with a full battery and you use up 50 Kilowatts to transport yourself 50 miles.
- you then need to burn a 100 kilowatt to recharge your batteries (50% energy loss)
- so, you actually used up twice the amount of diesel to cover those 50 miles then you would have had to use if you'd run on the surface.

Conclusion: running submerged is very inefficient due to the way the recharge process works.

On the surface, applied physics would seem to indicate that running submerged on batteries would have less overall range than running on diesels alone, but this is not neccesarily the case.

While it's true that the energy in the batteries used for submerged travel is not "free" and has to be gotten from fuel reserves and that the fuel-diesel-battery-motor energy chain is not 100% effecient, it's still possible for battery / electric engine use to increase, not decrease the range of the submarine. I will try to explain using the most extreme case of diesel/electric mixed propulsion.

Version A: A stopped sub with 0% charged batteries will run the diesel engines strictly as a generator to charge the batteries. Once the batteries have a charge, the sub uses its electric motor to move 10nm.

Version B: A sub uses its diesel engines to drive 10nm.

Which version uses more diesel? You may be tempted to say Version A uses more diesel fuel since the recharging, eletric motor process has more steps and thus more chances for energy to be lost due to heat, friction, 2nd law of thermodynamics, etc but it is not neccesarily the case.

It is because the diesel engine does not have the same effeciency at all RPM! It is possible to charge the batteries at the RPM that is the most effecient for the diesel engine while maybe the best RPM for the diesel engine/ boat hull is not so effecient for the diesel engine. The convoluted fuel-engine-battery-motor process, despite having more steps CAN (in theory) be more fuel effecient than the diesel engine alone because of the variable effeciency of the diesel engine under various loads.

Now I am completely uncertain about the following two concepts:

1. Were real life WWII submarines more effecient under mixed diesel-electric propulsion compared to pure diesel? It's theoretically possible but was it actually the case? Unknown. I thought German U-boats benefit from the mixed propulsion.

2. Are WWII submarines as modeled by the game (vanilla, modded?) more or less effecient under either method? Again unknown.

MORE INFO AND CITE:

http://www.ossapowerlite.com/tech_li...efficiency.htm

Not all of the points made in this article apply to WWII submarines as they are designed, but there are plenty of valid points made that do.

07-29-07, 09:36 PM	#1
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	Guide to fuel conservation Fuel consumption, and its conservation is actually a big part of the game, and i believe a part that is not fully understood by everyone. First, lets get the basics out of the way: Things that lower your fuel capacity - Damaged fuel tanks (obviously) - Recharging batteries - Battery damage. ( Once a battery is damaged the game doesn't always turn "recharge mode" off, and you have to do this manually, the kicker is, you may not always realize it, so always make sure you CE goes back to normal running after a battery charge) - High speeds chases - Putting around at excessively low speeds. Things that effect your total surface endurance - the state of the sea. High waves and wind will hinder you on the surface. A bit more on charging batteries In SH3, when you were recharging your batteries one of your two engines was taken off propulsion and switched to charge the batteries, and thats all it did. While doing so, this engine would be running at an RPM equivlant to flank speed. While i'm unsure exactly how engine configurations in SH4 handle the charge, it is reasonable to assume that while charging your batteries, you have one or more engines running at a higher than normal RPM, this takes fuel. With this in mind, you would do well to conserve your batteries when you can by running at lower submerged speeds. With patch 1.3, assuming your running TMaru, battery recharge time averages around 6 to 7 hours. Running submerged at 2 kts uses less batteries then running submerged at 3 kts. Running submerged saves fuel, so long as you keep your battery expenditure to a minium to reduce recharge requirements. Midway and sub tenders... Use them. Plan on using them, their there for a reason. Infact, if your a pearl harbor boat, you NEED midway. Any patrol route that leaves pearl harbor that does not figure in midway both when going to your patrol area, and coming back from your patrol area, is a failure. Asiatic fleet boats should count on the tenders which appear later in the war. Ploting the first half of your patrol route So you've left pearl harbor, and topped off your fuel tanks at midway, (Tmaru does this for you, but thats besides the point). The first thing I should do, is take the ruler tool and plot a line from my current location near midway, to my patrol area. This gives me the most direct route. What i do then is zoom in the map and actually plot the course using the line(s) i just drew as a guide. The purpose being to make sure i don't run the boat aground on some small island or reef that does not appear on the map when zoomed out. You may also have to plot around some large islands, and you should try for the closest route to the line you drew, geography and ASW concerns should be part of your decision. Once i've plotted my course to my patrol area, i wlll go to AHEAD 2/3's, and while i wait for the boat to build up speed to around 8 or 9 kts, i proceed to my next step. Plotting the second half of your patrol route So the boats building up to a speed of 8-9 kts and while its doing so , i will go ahead and plot my course back from my patrol area to midway or whatever refueling point i will encounter before my home base. Having done that, and the boat at now my normal cruising speed, i start jabber jawing with my navigator. "Hey Jim, whats the range to course end?" "Eh, i calculate about its about 10,500 Nautical miles Rich". "hmm, ok, at our current speed, how far do you think we'll go?" "Given our current speed, i reckon we have enough fuel to travel about 14,500 NM, give or take" "Ok, thanks jim". Figuring out your actual patrol allowance Patrol allowance is a term i give to how much fuel you have to actually operate on. In the above example, you have an estimate of about 14,500 nm, and your round trip ticket costs you 10,500 NM. That's just coming and going. This fuel is commited, theres no flexing here. So what you acutally have is 4,000 NM of fuel to operate on. However, theres other factors to consider. Primarily Battery recharging and the weather, both of which will reduce your operational endurance. Given this, ill take my above data, and round up to compensate. So i fgure 11,000 NM to get to and from base, with a 14,000 NM endurance, which gives me 3,000 NM of fuel to work with. In the interests of giving myself a bit more flex for the return trip to make sure i can make it home, ill take 1,000 off of that. So in reality, i have an operational endurance of 2,000 NM. Thats ALL im giving it. If i push it more then that (and i could with that built in buffer), i endanger my ability to RTB. Establishing when its time to RTB The easiest and simplist way is to always be mindful of how far you are from the closest refueling point (midway in my case), and your maximum range at current speed is. If you have a maximum range of 6,500 NM, and you range to midway is 5,000 NM, its time to RTB! Always allow a buffer. Being stingy with your operational fuel So, now that we've established we have about 2,000 NM of actual fuel to play with, your going to encounter situations that will tax that, and your going to have to make decisions based on that. For instance, is the target your pursing worth the fuel expenditure? Is that 2,000 ton freighter worth the fuel it would take to do an end around attack? Or would you hold your cards and hope 5,000 ton freighter? Is a submerged approach more economical then a surfaced one? etc etc, theres all sorts of hypotheticals. Extending your stay in the area of operations In short, in daylight, patrol submerged at the most battery economical speed of 1/3rd, or 1 to 2 kts. Use as little of your battery as possible, so you use less fuel recharging it, not to mention some fuel savings for having not used your diesals to begin with. Now then, that clear as mud to ya all? if you read all that and understood it, now you know why ive always been saying fuel is a big part of the sim, and If your running out of fuel, well, you made some wrong decisions captain, better brush up! Last edited by Ducimus; 07-29-07 at 09:58 PM.

07-29-07, 09:53 PM	#2
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	edited a A BUNCH of times if you started reading it. I got over complex in some areas.

07-29-07, 10:30 PM	#3
Go4It Engineer Join Date: Apr 2007 Location: South of Buffalo N.Y. USA Posts: 209 Downloads: 0 Uploads: 0	Never new SH4 had sub tenders, if so, were does one find one....

07-29-07, 10:58 PM	#4
Iceman Ace of the Deep Join Date: Sep 2002 Location: Mesa AZ, Arizona, USA Posts: 1,253 Downloads: 5 Uploads: 0	Very good advice thank you for the post.

07-30-07, 03:07 AM	#7
THE_MASK Ace of the deep . Join Date: Jan 2006 Posts: 9,226 Downloads: 901 Uploads: 73	Thanks for this awesome fuel summary .

07-30-07, 07:45 AM	#9
Steeltrap Grey Wolf Join Date: Mar 2001 Location: Sydney, Australia Posts: 818 Downloads: 3 Uploads: 0	Another thing to consider is this: do I have to go anywhere IN my patrol zone? In other words, having reached your patrol zone there is no actual need to go anywhere until you find a target or have one reported you wish to intercept. That's why I lie motionless on the surface in my patrol zone once I'm in a likely encounter position. O'Kane did that in Tang...he said to lie to like that took some getting used to!