Exploding Fuel Cell AIP. Safer alternative of LIBs in Soryus

Explosion of Fuel Cell AIP 

S comments that submarines that use Lithium-ion batteries (LIBs) have a superior performance in high speed situations and flexibility in operation compared with lead-acid battery (LAB) submarines with air independent propulsion (AIP). AIP is not as useful as extra battery capacity for relatively high speed cruising and quick recharging, because:

i) output of AIP is low and nearly constant (eg. 240kW for Stirling AIP of Soryu)

ii) Stirling AIP needs liquid oxygen (LOx) and kerosene which cannot be supplied by other ships. 

iii) LIBs need no fuel other than standard diesel for the diesel engines. Such fuel can be supplied by ships.

iv)  AIP uses particularly explosive chemicals, which are dangerous.

[Pete Comment - Here is a http://www.koreaittimes.com/story/55236/hhis-submarine-saw-explosion-hydrogen-tank November 4, 2015 report of an explosion of a fuel cell AIP hydrogen tank which occurred on November 3, 2015 very likely on a South Korean Son Won-Il Type 214 (KSS-II) submarine being constructed at HHI. The Chang Bogos (KSS-Is) don't have AIP:

"The explosion took place in Hyundai Heavy Industries’ submarine under construction on Tuesday [November 3], according to a local media outlet Money Today.

According to the report, the explosion occurred at the submarine at HHI's plant located in Ulsan on Monday morning. The fire was suppressed in 30 minutes and there was no casualty.

The explosion reportedly took place during the process of extracting remaining gas in hydrogen tank installed in the submarine. A local submarine does not generally [or ever] use nuclear energy as motive power but hydrogen fuel cells are installed in the tank instead.

"We are not able to disclose which type of submarine had the explosion accident," said the company's official, adding, "There will no problem in meeting the construction schedule.""  ENDs

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Soryu Table

SS No.	Building No.	Pennant No.	Name/Namesake	LAB or LIB & AIP *	Laid Down	Laun -ched	Commi-ssioned	Built By
16SS	8116	SS-501	Sōryū (そうりゅう) / Blue Dragon	LAB + AIP	March 2005	Dec 2007	March 2009	MHI
17SS	8117	SS-502	Unryū (うんりゅう) / Cloud Dragon	LAB + AIP	March 2006	Oct 2008	March 2010	KHI
18SS	8118	SS-503	Hakuryū (はくりゅう) / White Dragon	LAB + AIP	Feb 2007	Oct 2009	March 2011	MHI
19SS	8119	SS-504	Kenryū (けんりゅう) / Sword Dragon	LAB + AIP	March 2008	Nov 2010	March 2012	KHI
20SS	8120	SS-505	Zuiryu (けんりゅう) / Sword Dragon	LAB + AIP	March 2009	Oct 2011	March 2013	MHI
22SS	8122	SS-506	Kokuryū (こくりゅう) / Black Dragon	LAB + AIP	January 2011	Oct 2013	March 2014	KHI
23SS	8123	SS-507	Jinryū (じんりゅう)/ Benevolent Dragon	LAB + AIP	Feb 2012	Nov 2014	March 2016?	MHI
24SS	8124	SS-508	Sekiryu /Holy Dragon	LAB + AIP	2013	2 Nov 2015	2017	KHI
25SS	8125	SS-509	Soryu Mark 1 not yet named	LAB + AIP	2014	2016?	2018	MHI
26SS	8126	SS-510	Soryu Mark 1 not yet named	LAB + AIP	2015	2017?	2019	KHI
27SS	8127	SS-511	Soryu Mark 2	LIB only	2016?	2018?	2020?	MHI
28SS	8128	SS-512	Soryu Mark 2	LIB only	2017?	2019?	2021?	KHI
29SS	8129	SS-513	Next- Generation Japanese Submarine	LIB only	2018?	2020?	2022?	MHI
1AU?			1st Australian class?		2022?	2024?	2026?

The following details provide an insight on future Soryu design and battery issues. This level of detail may gain considerable importance if Australia finally chooses an "Australian Soryu" design after the SEA 1000 CEP process. The information below is drawn from several of S's Comments on Submarine Matters here and here with several translation-changes be Pete for clarity.

Japan has an advantage over the French and German contenders in being able to integrate an Australian "soryu" into an ongoing continuous build program. By continuous build this does not mean Australian submarines will be built in Japan. It means is that Japan is constantly redesigning improved submarines and designing key technologies (such as Lithium-ion batteries (LIBs)).

Japan’s MHI and KHI are careful to build submarines on time and on budget with submarines being launched within the planned year and month.

The versions of the Soryu preceding any Australian Soryu (maybe to be called "1AU" or "SEA 1000"?) will be 27SS, 28SS and 29SS (see table). 27 to 29SS will be Lithium-ion battery (LIB) submarines which will replace the Soryu's existing Lead-acid batteries (LAB) and the Stirling AIP. A more powerful diesel engine will, via a generator, charge the LIBs.

"wispywood2344" has drawn and labeled this very useful diagram of the Soryu.  A larger version of the diagram is at http://blog.livedoor.jp/wispywood2344/others/Soryu_cutaway.svg. 
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It is not yet known how often (every 7 - 10 years?) LIBs will need to be replaced on Japanese or Australian Soryus. This is because LIBs are new technology and may be used in different ways by different navies. 

Access To Replace LIBs

To permit replacement of LIBs using the mid access hatch (diagram above) there would need to be below the mid access hatch a hatch:

i) on the floor of the officer’s accommodation (6)

ii) on the floor of the mess/galley (7)

iii) between fore and aft batteries sections (5 and 8)

iv)  (on the Australian Soryu) also a hatch between the aft battery section (8) and new battery section (10)

As the LIB cell modules are too heavy for manhandling they are moved on the submarine aisles by using horizontal and vertical hydraulic jacks.

If the Australian Soryu “SEA 1000” concept is the expected 6 - 8 meters longer than 29SS, more LIBs can fit into the design.

[Pete has added - Here is the lowering of LAB cell modules through the mid section hatch and down into the battery section of a South Korean Chang Bogo Type 209 submarine

https://youtu.be/yE9lmXHpRho?t=1m35s   through to 1 minute 58 seconds]

Placing More LIBs (240) On Australian Soryus

On 27 to 29SS and the Australian Soryu an extra 240 LIB cell modules may be placed in the space (see section 10 of diagram (below) where the AIP's LOx tank assembly was. When those 240 are added to the existing 2 x 240 LIB cell modules existing battery spaces the submarines can have a total of 720 cells . 

240 comes from Japanese Ministry of Defence Standard NDS F8016B “General rules for design of equipment with small stray magnetic field”, 5.3”Arrangement of main batteries for submarine” which specifies that submarine generally equips with directly connected 240 single cells as a group. 

720 cells may mean an increased endurance (perhaps talking 2 to 3 weeks).

How it works. When snorting/snorkelling air is drawn into the diesels turning the generator, then the Motor to power the battery. When sub is fully submerged battery drives the motor, which turns propeller. The Soryu does not have reduction gearing system, as stepless speed control is conducted in the motor. (Diagram courtesy MARINEBIO)

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Maximum Range and Power Using LIBs

S estimates 720 cells will give Soryus 3 - 4.5 times longer submerged range than current Soryus using LABs alone. S estimates energy density of LIBs is 2-3 times higher than current LABs. LIBs will permit higher fully submerged speeds the submarine has a new generator system and new motor(s).  

S comments: If we adopt simple cubic rule between speed and power, maximum speed will be estimated to be 29-33knot/h for an extremely short period. S thinks actual speed will be lower than estimated value, but still high compared to LAB subs.

S assumed maximum power of 18,000-27,000kW@15min [for 15 minutes] is possible for propulsion motors operated by LIBs (5900kW@15min for current LABs submarine). However issues such as increased need for cooling and friction should be considered:

i)  there would be high temperatures at "silent mode operation" where auxiliary fans and oil pumps ( for bearings) have been stopped, and

ii)  increased energy for cooling and friction losses. 

S thinks safe-efficient levels of maximum power of motors and maximum speed may be at a lower 12,000kW, yielding 25knot@1hour. 

This compares with maximum fully submerged speed 18knot@1h for perhaps for the current Soryu and "dash" speed 20knot@15min.

Used lead-acid batteries for one or several? Collins submarines. Description is "They were/are manufactured in Australia [probably by PMB Defence] weigh something like 3 tons each cell and are about 1.5m high and a metre wide...The entire battery weighs in at about 450 tons [150 cells] (Photo and description overclockers forum Comment #9)

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Reduction of Stray Magnetic Field Using LIBs

A stray magnetic field is undesirable in batteries. Reduction of stray magnetic field must be considered in cell arrangement and cell-to-cell connection according to Japanese Ministry of Defence Standard NDS F8016B. Rules of the arrangement and the connection are as follows:

i) width of each column of cell module should be the same.  (240 = 20 columns x 12 cell modules) was decided based on these rule. In this case colums of 20 satisfies rule. 

ii) numbers of each column are desirably multiples of four or must be at least an odd number (20 = 4 x 5) and number (12) of cell module in a column satisfies rule 

iii) desirable numbers of cell modules in a column are multiples of four. (12 = 4 x 3). Logically speaking, if the rules are satisfied, other arrangements such as three groups of 24 columns or four groups of 16 columns are possible.

iv) polarity cancellation of a pair of neighbouring columns should be conducted by cross connection of these columns, and so on.

S and Pete