Soryu LABs vs LIBs, AIP and Indiscretion Ratios

Anonymous has provided the following comments from January 13 to 15, 2018 (with some further translation by Pete). This is on the interrelated issues of LABs vs LIBs, AIP and Indiscretion Ratios. The maths are quite challenging.

According to the former Commander of the Japanese Navy Submarines Service, Vice Admiral (retired) Masao Kobayashi, in a lead-acid battery (LABs) submarine, one hour-ventilation by using a diesel generator (DG) is needed after battery charging to release hydrogen generated by the charging process. 

Based on this information, the indiscretion ratio of the five following submarine Cases/scenarios have been reviewed and very roughly estimated for Japanese submarine missions of 70 days. This is where the surveillance period is 50 days and transiting period is 10 days x 2 = 20 days) and the DG output (hotel load + propulsion) is 250kW:

The lower the Indiscretion Ratio (IR) (the snorkeling period per 24 hours) the better.

Case I   (submarine length 84m, LABs, powered 100MW (or is that 100 kW?) - air independent

             propulsion (AIP), 2 x 2MW-generators, model Soryu MK I, IR =7%;

Case II  (length 84m, lithium-ion batteries (LIBs), 2 x 2MW-generators, model Soryu MK II)

              see Table below) IR=6%;

Case III  (long range Soryu proposed for Australian Future Submarine (AFS), length 90m, LIBs, 

               4 x 2MW-gnerators) IR=2.5%;

Case IV  (AFS, length 96m, 100MW-AIP, LIBs, 4 x 2MW-gnerators) IR=2%;

Case V   (AFS, length 96m, 100MW-AIP, LABs, 4 x 1MW-generators) IR=7%.

Comparison of Cases I and V shows that IR is determined by slow charge rate of LABs in a LAB-submarine. Comparison of Cases II, III an IV shows that output of the DG shows critical effects on IR for LIB submarines.

Performance at low speed means IR is Case IV>= Case III >>Case II >Case V = Case I.

Performance at high speed, which depends on batteries, is Case III>= Case IV >>Case II >Case V = Case I.

The facts that:

-  using up stored liquid oxygen (LOx) ends the usefulness of the Soryu’s Stirling AIP, and

-  LIBs are better than LABs

shows the flexibility of operation of each cases: Case III>= Case II >Case IV> Case V=Case I.

The superiority of AIP and LIBs, or simple LIBs, depends on a submarine’s mission. DGs play a critical role in both LIBs-submarines (Cases II and IV) within certain diesel power output ranges.

Anonymous thinks the future of LABs-submarines (Cases I, III and V) are limited with or without AIP and recent the tragedy of Argentina’s ARA San Juan shows LABs are not automatically safe.

More mathatically IR was very roughly estimated as follows:

Over 24 hours the balance of energy supplied [Es] to batteries and energy consumed [Ec] form batteries and AIP is described in equation (1)

(1)   Es = Ec

(2)   Es = Energy from diesel generator [Ed] + Energy from AIP [Ea]

(3)   Ec = Energy for propulsion [Ep] + Energy for hotel load [Eh]

The Indiscretion ratio (IR) which is the snorkeling period [ts] per day (=24h) is described in eq (4)

(4)   IR = ts/24 x 100 (%) = (tg + th)/24 x 100 (%)

(5)   ts = snorkeling period for diesel generation [tg] + snorkeling period for hydrogen release [th] 

        This is where, th =1h for LABs with hydrogen generation, and th = 0h for LIBs without 

        hydrogen generation.

Charge of batteries (capacity X (MWh)) with Y of C rate, Ed for ts is described in (6)

(6)   Ed = 1000XYtg  This where C daily energy from Z (MWh)-AIP for 50 days-opertion is 

        described in (7)

(7)   Ea =1000Z/50 =20Z

(8)   is derived from (2), (6) and (7), Es =1000XYtg + 20Z

(9)   If 250 kW of energy is consumed in an hour, then, Ec = 250 x {24-(tg + th)} ---

(10) is derived from (1), (8) and (9), 1000XY tg+ 20Z = 250 x {24-(tg + th)}

(11) is derived from (4) and (10), IR =[1-{(1000XY tg+ 20Z)/(250x24)}]x100=(tg + th)/24 x100 .  

       Where, tg = (250 x24-20Z-250 th)/(1000XY+250)  IR is from eq (11)

10MWh-LAB, non-AIP, 0.2 C rate, 2MW-diesel: X=10, Y=0.2, Z=0, th =1, IR=14.8%

10MWh-LAB, 100MWh-AIP, 0.2 C rate, 2MW-diesel: X=10, Y=0.2, Z=100, th =1, IR=11.1%

20MWh-LIB, non-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=0, th =0, IR=5.8%

20MWh-LIB, non-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=0, th =0, IR=3.0%

20MWh-LIB, 100MWh-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=100, th =0, IR=3.9%

20MWh-LIB, 100MWh-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=100, th =0, IR=2.0%

ANONYMOS’s CONCLUSION (LIBs Over LABs)

Though the estimates are based on many assumptions and are rough, the results clearly show the superiority of LIBs over LABs. Anonymous believes LIBs are indispensable to maintain the regional superiority of a conventional submarine.

 TABLE - SORYU & Oyashio Program as at January 16, 2018 

SS No.	Build No Name	Pennant No.	MoF approved amount ¥ Billions FY	LABs, LIBs, AIP	Laid Down	Laun -ched	Commi ssioned	Built By
5SS Oyashio	8105 Oyashio	SS-590/ TS3608	¥52.2B FY1993	LABs only	Jan 1994	Oct 1996	Mar 1998	KHI
6SS-15SS Oyashios 10 subs	8106 -8115 various	SS-591-600	¥52.2B per sub FY1994-FY2003	LABs only	15SS Feb 2004	15SS Nov 2006	15SS Mar 2008	MHI & KHI
16SS Soryu Mk 1	8116 Sōryū	SS-501	¥60B FY2004	LABs + AIP	Mar 2005	Dec 2007	Mar 2009	MHI
17SS	8117 Unryū	SS-502	¥58.7B FY2005	LABs + AIP	Mar 2006	Oct 2008	Mar 2010	KHI
18SS	8118 Hakuryū	SS-503	¥56.2 FY2006	LABs + AIP	Feb 2007	Oct 2009	Mar 2011	MHI
19SS	8119 Kenryū	SS-504	¥53B FY2007	LABs + AIP	Mar 2008	Nov 2010	Mar 2012	KHI
20SS	8120 Zuiryū	SS-505	¥51B FY2008	LABs + AIP	Mar 2009	Oct 2011	Mar 2013	MHI
No 21SS			No 21SS built
22SS	8121 Kokuryū	SS-506	¥52.8B FY2010	LABs + AIP	Jan 2011	Oct 2013	Mar 2015	KHI
23SS	8122 Jinryu	SS-507	¥54.6B FY2011	LABs + AIP	Feb 2012	Oct 2014	7 Mar 2016	MHI
24SS	8123 Sekiryū	SS-508	¥54.7B FY2012	LABs + AIP	15 Mar 2013	2 Nov 2015	13 Mar 2017	KHI
25SS	8124 Seiryū	SS-509	¥53.1B FY2013	LABs + AIP	22 Oct 2013	12 Oct   2016	Mar? 2018	MHI
26SS	8125 Shoryu	SS-510	¥51.7B FY2014	LABs + AIP	2014	6 Nov 2017	Mar 2019?	KHI
27SS First Soryu Mk 2	8126	SS-511	¥64.4B FY2015	LIBs only	2015	2018?	Mar 2020	MHI
28SS  Second Soryu Mark 2	8127	SS-512	¥63.6B FY2016	LIBs only	2016?	2018?	Mar 2021?	KHI
29SS First Soryu Mk 3 (1) (3)	8128	?	¥76B FY2017	LIBs only	?	?	2023?	MHI?
30SS Second Soryu Mk 3 (2)	8029?	?	¥71.5B FY2018	LIBs only	?	?	2024?	KHI?

Table from information exclusively provided to Submarine Matters. LABs = lead-acid batteries, AIP = air independent propulsion, LIBs = lithium-ion batteries. ¥***B = Billion Yen. MHI = Mitsubishi Heavy Industries, KHI = Kawasaki Shipbuilding Corporation of Kawasaki Heavy Industries.

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By Anonymous