January 16, 2018

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
KHI
25SS
8124
SS-509
¥53.1B FY2013
LABs + AIP
22 Oct 2013
12 Oct   2016
Mar? 2018
MHI
26SS
8125
Shoryu
SS-510
LABs + AIP
2014
6 Nov 2017
Mar 2019?
KHI
27SS First
Soryu Mk 2
8126
SS-511
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 MattersLABs = 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

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