Endurance voyages - Battery vs Diesel

Stix · 12-23-06, 04:59 AM

Well considering my Carribean hunting grounds thread has been highjacked by range finding juckies i did some maths

Basically i can travel 84nm using batterys for the same amount of fuel as it would cost me to travel 21 nm on diesels.

Quick maths for you.

SUBMERGED

23 hours submerged @ 3kt = 69nm
3 hours recharging @ 5kt = 15nm
Total 84nm for the loss of 3 hours fuel at "Ahead slow"

SURFACED

3 hours crusing @ 7kt = 21nm
Total 21nm for the loss of 3 hours fuel at "Ahead slow"

Doing this increases range by 75% in my book, did i go wrong somewhere?

Stix

EDIT, This is in GWX.

Letum · 12-23-06, 05:13 AM

Yes, you went wrong.

You are assumeing that you are useing the same ammount of fuel in 3 hours. Just because you have the same speed setting does not mean you are useing the same ammount of fuel with chargeing on/off.

Letum · 12-23-06, 05:29 AM

If you want to do a definitive test you must:

1) note down the weather conditions (these must not change in the test)
2) Run at 1/3 speed. when you are at the maximum knots for 1/3. Ask the navigator for your maximum range. Note it down. This is "Max Range 1"

3)
i) Start at periscope depth.
ii) Run at 1/3 speed underwater until your battery is totally dead
iii) Surface and run at 1/3 on the surface until your battery is at 100%
iv) note the distance. This is the "test distance"

4) As soon as the batteries are charged run at 1/3 speed. as soon you are at the maximum knots for 1/3 ask the navigator for your maximum range. Note it down. This is "Max Range 2"

3) Run at 1/3 speed. when you are at the maximum knots for 1/3. Ask the navigator for your maximum range. Note it down. This is "Max Range 3"

4) As soon as step (3) is complete run at 1/3 for "test distance"

5) when you reach the end of "test distance" ask the navigator for your maximum range. Note it down. This is "Max Range 4"

Repeat the test at least once
It is essensial that there are no time gaps between the steps of the test.

If "Max range 1" - "Max range 2" is greater than "Max range 3" - "Max range 4" than using electrics is less efficient.

If the results are not clear than repeat the test, but do steps 3i, 3ii and 3iii twice to dubble the test distance.

Corsair · 12-23-06, 05:47 AM

Quote:

Originally Posted by Letum

Yes, you went wrong.

You are assumeing that you are useing the same ammount of fuel in 3 hours. Just because you have the same speed setting does not mean you are useing the same ammount of fuel with chargeing on/off.

Why would not you be using the same amount of fuel ? Both engines work the same way when reloading, only difference is the right one is coupled to the alternator instead of being coupled to the driving shaft...
And definitely yes if you submerge during the day and run surfaced at night you will go further than driving surfaced all the time (except of course if you want to have the same speed on surface with one engine instead of two) and you probably will live longer...

Letum · 12-23-06, 05:50 AM

Quote:

Originally Posted by Corsair

Quote:

Originally Posted by Letum

Yes, you went wrong.

You are assumeing that you are useing the same ammount of fuel in 3 hours. Just because you have the same speed setting does not mean you are useing the same ammount of fuel with chargeing on/off.

Why would not you be using the same amount of fuel ? Both engines work the same way when reloading, only difference is the right one is coupled to the alternator instead of being coupled to the driving shaft...
And definitely yes if you submerge during the day and run surfaced at night you will go further than driving surfaced all the time (except of course if you want to have the same speed on surface with one engine instead of two) and you probably will live longer...

http://www.subsim.com/radioroom/show...8&postcount=19

Read and understand that. I can not make it any more simple.
There is a simple efficancy loss in chargeing the battrys. No system can run above 100% efficancy!

Stix · 12-23-06, 05:54 AM

Hmmmm, that test doesn't make sense to me mate. i understand what you are saying but it won't calculate fuel burn.

It all comes down to does SH3 GWX model increased fuel burn while batterys are recharging or simply slower speed i.e. same fuel burn but less power to the props because of increased load from the altinators.

Stix

Corsair · 12-23-06, 05:57 AM

@ Letum

If you want to believe it, it's your absolute right...

But you still have to demonstrate that a diesel engine running at a fixed rpm uses more fuel when it is driving an alternator than when it is driving the boat shaft.

Letum · 12-23-06, 05:57 AM

Quote:

Originally Posted by Stix

Hmmmm, that test doesn't make sense to me mate. i understand what you are saying but it won't calculate fuel burn.

It all comes down to does SH3 GWX model increased fuel burn while batterys are recharging or simply slower speed i.e. same fuel burn but less power to the props because of increased load from the altinators.

Stix

The test calculates the diffrance between the loss of Km from the maximum range for surface and submerged/chargeing along a set distance.
This has a direct relationship to fuel burn.

Corsair · 12-23-06, 06:00 AM

Quote:

Originally Posted by Stix

Hmmmm, that test doesn't make sense to me mate. i understand what you are saying but it won't calculate fuel burn.

It all comes down to does SH3 GWX model increased fuel burn while batterys are recharging or simply slower speed i.e. same fuel burn but less power to the props because of increased load from the altinators.

Stix

There is no increased load. One engine is decoupled from the driving shaft (thus the drop down in speed) and is actioning an alternator instead for reloading the batteries. This engine still works at the same rpm and has no extra load, it's just used for something else.

Letum · 12-23-06, 06:03 AM

Quote:

Originally Posted by Corsair

@ Letum

If you want to believe it, it's your absolute right...

But you still have to demonstrate that a diesel engine running at a fixed rpm uses more fuel when it is driving an alternator than when it is driving the boat shaft.

You guys are driveing me mad!

There is efficancy loss when chargeing the battrys, but no efficancy gain when powering the screw from e-motors.

Running and chargeing e-motors results in a net efficancy loss. Less efficancy = more fuel for the same distance / time.

Ducimus · 12-23-06, 06:04 AM

Good greif.

Look, its late and im tired so im going to put this in undersimplified terms.

In SH3 you basically have this:

ENG_Power effects, how large a unit of fuel/energy the game will use. It also effects top speed. Increase this number, you engines will suck a largerfuel/energy unit.

Eng_RP are used in AI detection routines (IE, how noisy are you?) and are i beleive how many units of energy are being used exponentially at a given point in time, depending on what settign you define. slow, 1/3rd, etc.

Orginaly the submerged endurance was MUCH larger. So large infact, that you rarely ran low on batteries. With upgraded battery units, you probably never ran out of electricity. I dont recall of ever having run a battery dry in stock SH3.

What was the battery fix? It reduced the maximum range of your undwater endurance. So your power pool to draw from isnt so vast, and thats ALL it does. Everything else remains the same.

Energy expenditure does not fluxuate excpet by what you tell it to do via throttle settings. Your surface range varies by your uboats mass and displacement and its relationship with weather. You see this every time you play. at your crusiing speed you might be doing 9 kts on a clear day and 7 kts in a heavy sea.

Now, lets talk about Hydrodynamics, or rather, LACK THEREOF. Drag, and such is not modled. This means that your not subject to any restriction of forward momentum while submerged. By cruising at a low RPM setting to achieve say 2 kts or so you get the maximum mileage out of your batteries. Your batteries will run dry around the same time you run out of oxygen, maybe a little before that. Anyway because the maximum capacity of the batteries isnt very large, it only takes about 3 hours to recharge them on the surface. Thats only 3 hours of being subjected to drag and running your diesals such to top off a smaller battery that will see you through an entire day and then some if you manage it wisely.

Letum · 12-23-06, 06:13 AM

Quote:

Originally Posted by Ducimus

Energy expenditure does not fluctuate except by what you tell it to do via throttle settings.

If by "throttle settings" you mean the speed settings in SH3 then yes it does!
You set Speed in SH3, not throttle.

If you think my calculations are wrong then please feel free to show me where my Math is wrong. Its very basic stuff.
There is a good reason surface ships don't run off batteries some of the time like u-boats do. It is because it is less fuel efficient.
If it was more fuel efficient then all ships would run of electric motors and just charge them up with diesel every now and again.

Corsair · 12-23-06, 06:13 AM

Quote:

Originally Posted by Letum

Quote:

Originally Posted by Corsair

@ Letum

If you want to believe it, it's your absolute right...

But you still have to demonstrate that a diesel engine running at a fixed rpm uses more fuel when it is driving an alternator than when it is driving the boat shaft.

You guys are driveing me mad!

There is efficancy loss when chargeing the battrys, but no efficancy gain when powering the screw from e-motors.

Running and chargeing e-motors results in a net efficancy loss. Less efficancy = more fuel for the same distance / time.

Why would there be an efficiency loss ? The engine generates the same power, while reloading this power is used to drive an alternator for reload, while not reloading the same power is used to drive the propeller shaft...

Letum · 12-23-06, 06:24 AM

Quote:

Originally Posted by Corsair

Why would there be an efficiency loss ? The engine generates the same power, while reloading this power is used to drive an alternator for reload, while not reloading the same power is used to drive the propeller shaft...

YaY! I think your starting to catch on!

Every time energy is changed (i.e. from chemical fuel to kinetic) some energy is lost, usually through heat.
Energy is also lost when the energy passes through components. (i.e. wear on the drive shaft)

The efficiency loss on e-motors is greater because the energy goes through more systems and changes.

On the surface it changes from fuel to the propeller motion and finally to the boats motion. It passes through the motor, the drive shaft and the screw. The main efficiency losses are in the motor, which heats up, and the screw, which is never 100% efficient.

On e-motors it must go from fuel to the motor to the alternator, the batteries, the e-motors, the drive shaft and then the prop. Efficiency is lost at the D-motor, the alternator, the batteries, the e-motor and the screw. The alternator and the batteries both get hot when they are charged.
When fuel is used less efficantly the boat can not go as far.

Letum · 12-23-06, 06:33 AM

I thought of a simpler way of saying it:

With a 100% efficient charging system you get as much out of the batteries as you put in.

No charging system is 100% efficient , so you get slightly less out of the batteries then you put in.

Lets say charging efficiency is at 90%
1 unit of fuel = 1 unit of energy
If you burn 100units of fuel you will put 90units of energy in the battery.
If you can go 1 mile one one unit of fuel/energy you will go 90 miles, but burn 100 units of fuel.
10 units of fuel have been lost as heat because the charging system is only 90% efficient.

On the surface you will go 100 miles on 100 units of fuel because you don't have the 10% loss in charging the batteries.

Claiming you go further running on batteries is saying that you get more out of your batteries than you put in. This is obviously impossible!

*edit* sorry, my spell check bugger things up for a second there

12-23-06, 04:59 AM	#1
Stix Mate Join Date: Dec 2006 Location: Gold Coast, Australia Posts: 54 Downloads: 0 Uploads: 0	Endurance voyages - Battery vs Diesel Well considering my Carribean hunting grounds thread has been highjacked by range finding juckies i did some maths Basically i can travel 84nm using batterys for the same amount of fuel as it would cost me to travel 21 nm on diesels. Quick maths for you. SUBMERGED 23 hours submerged @ 3kt = 69nm 3 hours recharging @ 5kt = 15nm Total 84nm for the loss of 3 hours fuel at "Ahead slow" SURFACED 3 hours crusing @ 7kt = 21nm Total 21nm for the loss of 3 hours fuel at "Ahead slow" Doing this increases range by 75% in my book, did i go wrong somewhere? Stix EDIT, This is in GWX. Last edited by Stix; 12-23-06 at 05:13 AM.

12-23-06, 05:57 AM	#7
Corsair Ace of the Deep Join Date: Nov 2006 Location: Toulouse France Posts: 1,140 Downloads: 51 Uploads: 0	@ Letum If you want to believe it, it's your absolute right... But you still have to demonstrate that a diesel engine running at a fixed rpm uses more fuel when it is driving an alternator than when it is driving the boat shaft. __________________ NYGM 3.4A / Living SH3 V5.1 + SH3 Commander

12-23-06, 06:33 AM	#15
Letum Navy Seal Join Date: Feb 2005 Location: York - UK Posts: 6,079 Downloads: 43 Uploads: 0	I thought of a simpler way of saying it: With a 100% efficient charging system you get as much out of the batteries as you put in. No charging system is 100% efficient , so you get slightly less out of the batteries then you put in. Lets say charging efficiency is at 90% 1 unit of fuel = 1 unit of energy If you burn 100units of fuel you will put 90units of energy in the battery. If you can go 1 mile one one unit of fuel/energy you will go 90 miles, but burn 100 units of fuel. 10 units of fuel have been lost as heat because the charging system is only 90% efficient. On the surface you will go 100 miles on 100 units of fuel because you don't have the 10% loss in charging the batteries. Claiming you go further running on batteries is saying that you get more out of your batteries than you put in. This is obviously impossible! edit sorry, my spell check bugger things up for a second there __________________ Last edited by Letum; 12-23-06 at 06:56 AM.

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12-23-06, 05:13 AM	#2
Letum Navy Seal Join Date: Feb 2005 Location: York - UK Posts: 6,079 Downloads: 43 Uploads: 0	Yes, you went wrong. You are assumeing that you are useing the same ammount of fuel in 3 hours. Just because you have the same speed setting does not mean you are useing the same ammount of fuel with chargeing on/off.

12-23-06, 05:29 AM	#3
Letum Navy Seal Join Date: Feb 2005 Location: York - UK Posts: 6,079 Downloads: 43 Uploads: 0	If you want to do a definitive test you must: 1) note down the weather conditions (these must not change in the test) 2) Run at 1/3 speed. when you are at the maximum knots for 1/3. Ask the navigator for your maximum range. Note it down. This is "Max Range 1" 3) i) Start at periscope depth. ii) Run at 1/3 speed underwater until your battery is totally dead iii) Surface and run at 1/3 on the surface until your battery is at 100% iv) note the distance. This is the "test distance" 4) As soon as the batteries are charged run at 1/3 speed. as soon you are at the maximum knots for 1/3 ask the navigator for your maximum range. Note it down. This is "Max Range 2" 3) Run at 1/3 speed. when you are at the maximum knots for 1/3. Ask the navigator for your maximum range. Note it down. This is "Max Range 3" 4) As soon as step (3) is complete run at 1/3 for "test distance" 5) when you reach the end of "test distance" ask the navigator for your maximum range. Note it down. This is "Max Range 4" Repeat the test at least once It is essensial that there are no time gaps between the steps of the test. If "Max range 1" - "Max range 2" is greater than "Max range 3" - "Max range 4" than using electrics is less efficient. If the results are not clear than repeat the test, but do steps 3i, 3ii and 3iii twice to dubble the test distance.

12-23-06, 05:54 AM	#6
Stix Mate Join Date: Dec 2006 Location: Gold Coast, Australia Posts: 54 Downloads: 0 Uploads: 0	Hmmmm, that test doesn't make sense to me mate. i understand what you are saying but it won't calculate fuel burn. It all comes down to does SH3 GWX model increased fuel burn while batterys are recharging or simply slower speed i.e. same fuel burn but less power to the props because of increased load from the altinators. Stix

12-23-06, 06:04 AM	#11
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	Good greif. Look, its late and im tired so im going to put this in undersimplified terms. In SH3 you basically have this: ENG_Power effects, how large a unit of fuel/energy the game will use. It also effects top speed. Increase this number, you engines will suck a largerfuel/energy unit. Eng_RP are used in AI detection routines (IE, how noisy are you?) and are i beleive how many units of energy are being used exponentially at a given point in time, depending on what settign you define. slow, 1/3rd, etc. Orginaly the submerged endurance was MUCH larger. So large infact, that you rarely ran low on batteries. With upgraded battery units, you probably never ran out of electricity. I dont recall of ever having run a battery dry in stock SH3. What was the battery fix? It reduced the maximum range of your undwater endurance. So your power pool to draw from isnt so vast, and thats ALL it does. Everything else remains the same. Energy expenditure does not fluxuate excpet by what you tell it to do via throttle settings. Your surface range varies by your uboats mass and displacement and its relationship with weather. You see this every time you play. at your crusiing speed you might be doing 9 kts on a clear day and 7 kts in a heavy sea. Now, lets talk about Hydrodynamics, or rather, LACK THEREOF. Drag, and such is not modled. This means that your not subject to any restriction of forward momentum while submerged. By cruising at a low RPM setting to achieve say 2 kts or so you get the maximum mileage out of your batteries. Your batteries will run dry around the same time you run out of oxygen, maybe a little before that. Anyway because the maximum capacity of the batteries isnt very large, it only takes about 3 hours to recharge them on the surface. Thats only 3 hours of being subjected to drag and running your diesals such to top off a smaller battery that will see you through an entire day and then some if you manage it wisely.