April 20, 2017

Submarine electricity discharge & generation using combinations of Diesels, LIBs, LABs & AIP

Following last week's articles (here, here and here) Anonymous continues representation of electricity discharge and generation using combinations of Lithium-ion Batteries (LIBs), Lead-acid Batteries (LABs) and Air Independent Propulsion (AIP). An extra variable is use of Diesels on full or half power.

Tables 1 and 2 present extra comparative information.


Figure 4 (below) is the output of diesel generators for model submarines:

Diesels in LIBs-sub operate once every two-days (no operation on Day 2) using diesel on full power.
(a) LIBs + new diesel generator (GE), Power of new Diesel increases to 125% compare to old Diesel. This is noting LIBs require (or benefit from) more powerful Diesels.
(b) LIBs + full power Diesel, 

C-rate of LABs is 0.2C. Output of each Diesel is 2 and 4M in half and full power, respectively.
(c) LABs + half power Diesel + AIP. In AIP operation. LABs are not discharged.
(d) LABs + half power Diesel, Operation cycle of LABs-sub is once a day. 

Grey represents no generation using Diesel; 
Green represents Diesel generation; 
Purple represents AIP generation; 

Lower axis Figure 4 represents electricity discharge and generation according to which team of the 3-watch crew roster are on duty. Where:
- Red represents team 1;
- Yellow represents team 2; 

- Blue represents team 3;  

Figure 4 
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4


Snorkeling/Diesel

(a)  LIBs+new Diesel (day 1 of 2 days)

















2
Discharge





Discharge to day 3, 20:00






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(b) LIBs +full power Diesel (day 1 of 2 days)







Snorkeling/Diesel







2
Discharge
Discharge to day 3, 20:00







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4








(c) LABs + half power Diesel + AIP (every day)





























2
Discharge
Snorkeling/Diesel

Discharge

AIP mode (240kW)

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(d)LABs + half power Diesel (every day)































2
Discharge
Snorkeling/Diesel
Discharge
Snorkeling
/Diesel
Discharge

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MW
























time
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00

01

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Table 1 - Performances of models
Model
Indiscretion ratio, IR [1] %
Submerge at max speed [2] h
Capacity of battery
MW
Output of Diesel [3]
MW
Rotation of Diesel
rpm
C-rate
Current
status
Limit [4]
LIBs + new Diesel
5.2
10
50
5
1200
0.1
1
LIBs + full power Diesel
6.3
10
50
4
1200
0.08
1
LABs + half power Diesel AIP
8.3
1
10
2
600
0.2
0.4
LABs + half power Diesel
12.5
1
10
2
600
0.2
0.4
[1] LIBs, IR=operation time (green)/48 x 100; LABs, IR= green/24 x100.
[2] Max speed is 18 knots; Energy consumptions are 4.5 and 40.5MW for LABs and LIBs, 
respectively.
[3] Data is total output of 2 Diesels. Model sub is equipped with 2 Diesels operating 
simultaneously.
[4] C-rate of LIBs is general data. Value of LABs is for high speed charge/discharge rate.


“C” means one Coulomb. C-rate is the inverse of charging time in hours. An empty
  battery with a C-rate of 0.5 just needs 2 hours to be recharged completely.


Table 2 -  Important factors
Term
Discussion
LAB
LIB
C-rate
As C-rate of LAB is small (0.1C, 0.2C) and capacity is low, C-rate dominates charge/discharge rate. Higher C-rate (0.4, 0.5C) is possible, but, it shortens life of LAB. Half power of Diesel can satisfy C-rate of 0.2C.
Dominative
-
Output of Diesel
As C-rate of LIB is large (0.5C, 1C) and capacity is high, output of Diesel  dominates charge/discharge rate. To get low indiscretion ratio, output of Diesel needs to be increased. In Fig.4 (a), C-rate is only 0.1C. Higher rotation of Diesel or increase of Diesels is possible measure, but it increases noise or vibration.
-
Dominative
Snorkel capacity
To realize high performance of LIBs, an improvement of the Diesel will be conducted within framework of snorkel system capacity to effectively discharge exhaust gases.

To achieve C-rate of 1 for LIBs is difficult (max. two- or three-fold increases?), C-rate of 1 is difficult to achieve (max 02-0.3?).
-
Dominative
Propulsion motor
To achieve high speed performance by LIBs, improvement of propulsion motor is required.
-
Important
Conclusion
To realize high performance submarine equipped with LIBs, comprehensive improvement of power system including Diesel, snorkel system and propulsion motors as well as development of LIBs are required.
Also, improvement and establishment of peripheral technologies including safety system and further reduction of noise/vibration are needed.

Anonymous

12 comments:

Josh said...

@Pete:

I admit to not keeping up on all the details of different battery types and power generation methods, since the devil is in the details and the actual open source details is subject to a lot of supposition. So I've missed the 'half diesel' aspect of the argument. What is the advantage? You're generating most of the noise and generating half the power. I could see this arrangement being slightly more efficient on diesel consumption by charging batteries more slowly, but total snort time generally won't be the limiting factor of patrol time.

Also I'd argue that the AIP method used matters greatly when doing those snort chart comparisons. A Stirling engine is a reciprocating combustion engine with non zero amount of noise associated with its moving parts, likely at a low frequency of engine rotation. Further more its sound characteristics likely immediately identify the source as a submarine from one of only several navies. Where as a fuel cell arrangement is likely for all intents and purposes silent, in that other sources of self generated noise are detectable first.


Cheers,
Josh

Anonymous said...

What will happen if glass batteries hit it big?:

"For John Goodenough, the 94-year-old co-inventor of the lithium-ion battery, lightning
appears to have struck twice. He recently published his latest battery design, the
lithium-glass battery, an entirely solid cell that has a strikingly long list of
admirable characteristics.

The new technology not only triples the energy density of lithium-ion, it also recharges
in minutes, survives thousands charging cycles, operates across a wide range of
temperatures (-4˚ F to 140˚ F), and won’t catch fire."

See:

http://www.pbs.org/wgbh/nova/next/tech/super-safe-glass-battery-charges-in-minutes-not-hours/

Peter Coates said...

Hi Anonymous

Reaction of sodium with water may be a worry https://www.webelements.com/sodium/chemistry.html.

"Sodium metal reacts rapidly with water to form a colourless solution of sodium hydroxide (NaOH) and hydrogen gas (H2). The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic.[up to explosive] During the reaction, the sodium metal may well become so hot that it catches fire and burns with a characteristic orange colour."

Although Lithium is also a worry, though less. https://www.webelements.com/sodium/chemistry.htmlhttps://www.webelements.com/sodium/chemistry.html

"The [sodium] reaction is slower than that of potassium (immediately below sodium in the periodic table), but faster than that of lithium (immediately above sodium in the periodic table)."

Then again if a submarine is deep and its pressure hull ruptered chemical reactions would no longer ruin one's day.

Regards

Pete

Peter Coates said...

Hi Josh

Yes half-diesel and other propulsion combinations are highly complex.

Japan might be specificly developing diesels with an expectation of running them more often (more quietly) at half power?

Half may be an alternative (or response) to running the diesels more noisely at 125% power compared to the old diesels.

Regards

Pete

Anonymous said...

"Reaction of sodium with water may be a worry https://www.webelements.com/sodium/chemistry.html."


Maybe, but the initial lithium-glass battery shouldn't be any worse that what is
available now.

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Anonymous said...

Hi Pete

Considering lifetime of LAB, C-rate of 0.1C is better than 0.2C, but indiscretion ratio becomes twice larger (25%). C-rate of 0.4C is too high as routine operation and shorten lifetime of LABs.

I estimated life time (mor than 1500 cycles ) of LABs based on exchange cycles of LABs, operation efficiency of J-submarine and daily cycle at 0.2C, and this value satisfy general value (more than 1000 cycles) of lifetime at 0.2C.

Though high C-rate charge shorten lifetime of LABs, it may be required for imergency. For this purpose, high power diesel generators are required. Output of 2000kW is enough for ordinary operation, but, full power output is required to achieve 0.4-0.5C.

DCN and RAN seem to think same thing as JMSDF, because Scorpène class and Collins equip with 4 BTUs (4000kW?) and 3 Hedemoras (4200kW), respectively, which are too large for routine charge/discharge cycles. I think maximum underwater speed at snorkeling will be achieved by half power of these diesels.

Regards

Anonymous said...

Running diesel engines at low rpm for long periods is not advisable leading to all sorts of engine reliabilities. Most diesel engines idle close to 60rpm so there is no load. there since torque is nil.
KQN

Anonymous said...

Continued (21/4/17 9:33 PM)

In the German submarines equipped with high performance AIP, operation using battery is different from said navay. At emergency situation, G-subs can hide in deep water, transfer to safe zone and charge battery slowly. That’s why German AIP submarines equip with small numbers of diesel generators (one for TYPE 212, two for TYPE 214), I think.

Conversely, they can not consum all LOx, and when consumption of LOx exceeds a certain threshold value, they will return to the base. After depletion of LOx, FC-AIP/LAB submarine becomes vulnerable than LAB submarine and loses freedom of operation because of lower power supply from diesel and smaller amount of LABs.

In Soryu-clas, Stirling AIPs as auxiliary equipment were simply attached to normal LAB submarine (Oyashio-class), and original ability of power supply and amount of LABs are retained. Effect of LOx depletion on submarine performance in Soryu is smaller than that in FC-AIP submarine.

Regards

Peter Coates said...

Hi Anonymous [at 22/4/17 9:18 AM]

Most German 212A missions may be in the Baltic Sea and the (close to Germany) North Sea. The Italian 212As/Todaro class may similarly operate at short ranges in the Mediterranean.

The Type 212A FC-AIP/LAB and Diesel capacity can indeed be limited. Once most of the 212A FC-AIP LOX is used the limited battery and less diesel power is adequate to return 212A to the German submarine squadron base at nearby Eckernförde. Eckernförde is on the Baltic coast and I believe close, via Kiel Canal, to the North Sea.

Regards

Pete

MHalblaub said...

Dear Pete,

I stumbled about the rate of the rotation mentioned in Table 1.
MTU 396 Diesel engines run at 1,800 RPM with 2.000 RPM max. The newer 4000 Series is running up to 2,100 RPM. The submarine MTU 4000 is rated 1,300 kW at 1.800 RPM.

In my opinion the term "C-rate" is not well explained.
A small battery has e.g. a capacity of 2,000 mAh (or 2,000 x 1/1000 x C/s x 3.600s). So this battery could provide a current of 7,200 Coulomb or 2 Ampere for one hour.
Reducing the current to 1 A would provide a battery support of 2 hours.

A C-rate of 0.1 means this battery will be recharged with a current of 200 mA. Battery capacity is given in Ah so it is easier to calculate the total charging time to 10 hours. So C-rate is the inverse of charging time in hours. An empty battery with a C-rate of 0.5 just needs 2 hours to be recharged completely.

--- Some math ---
Diesel generator of a Type 212A has power output of 1,050 kW. Let's estimate this power is equivalent to an optimal c-rate for battery life of just 0.1. So 1,050 kW could be stored for 10 hours or a total energy storage of 37,800 MJ (1,050 kW x 10 x 3600 s) or 10,5 MWh (~300 t LAB). No fast charging is required due to AIP back up.
--- Hint: battery capacity is not MegaWatt MW rather MegaJoule MJ or MWh MegaWattHours. ---
Max propulsion power is 1700 kW. Reducing the available energy to 75% to avoid deep discharge leaves about 7.875 kWh. That leads to about 4.5 hours at full speed ahead.
On the other side a Type 212A can travel submerged on just two fuel cells with a maximum power output of together just 240 kW. Therefore the batteries should at least keep the submarine running for one day and 8 hours. I would guess two days should be possible with LABs so required power for operations at slow speed should be around 160 kW.

160 kW within 24 hours could be replaced by recharging the batteries at 1050 kW within 3.7 hours. Maybe required power is even less?

Type 214 also just has two fuel cells but two Diesel engines instead of one. With a higher battery capacity this could lead to faster transit times or just a higher C-rate.

Instead of running two engines on half power running one engine at optimum power could be far better.

--- 5.2 MW submarine ---
A submarine with 4 MTU 4000 engines at 1,300 kW each. With LIBs and a charging time of 2 hours about 10.4 MWh of energy could be stored. The 10.4 MWh has not to be the complete battery capacity. This leads to a sustained power of 433 kW for the whole day. Such a submarine is far bigger than a Type 212A to maintain 3 more Diesel engines. Frontal surface of a Barracuda submarine is twice as big as a Type 212. Wetted surface is more than three times greater. This leads to far higher drag. Therefor the advantage of more engines is not proportional to installed power. Equipped with an energy hungry combat system the advantage shrinks even more.

Running a combined engine power of 5.2 MW also mean a huge amount of heat.

--- Indiscretion Ratio ---
The Indiscretion Ratio IR can be calculated for a whole mission. It is also possible to calculate IR for different parts of a mission. Then AIP has the advantage to offer an IR of 0 % for at least two weeks on station. IR on journey is than equivalent to a normal submarine but possibility of detection is far lower for complete mission.

--- LIB vs. LAB ---
Lithium Ion Batteries offer the advantage of a five times higher energy density according to weight. A normal submarine will not gain different IR but snorkeling times could be better adapted to expected detection threats.



Regards,
MHalblaub

Peter Coates said...

Hi MHalblaub [at 24/4/17 10:41 PM]

Thanks for all your calculations particularly on "C-rate".

I'll add "C-rate is the inverse of charging time in hours. An empty battery with a C-rate of 0.5 just needs 2 hours to be recharged completely." to the definition to make it a little more understandable.

Regards

Pete