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 

8
6
4			Snorkeling/Diesel						(a)  LIBs+new Diesel (day 1 of 2 days)
2	Discharge							Discharge to day 3, 20:00
0
8
6
4									(b) LIBs +full power Diesel (day 1 of 2 days)
			Snorkeling/Diesel
2	Discharge								Discharge to day 3, 20:00
0
8
6
4									(c) LABs + half power Diesel + AIP (every day)
2	Discharge		Snorkeling/Diesel																Discharge
							AIP mode (240kW)
0
8
6
4									(d)LABs + half power Diesel (every day)
2	Discharge		Snorkeling/Diesel				Discharge												Snorkeling /Diesel		Discharge
0
MW
time	19		20		21		22		23		00		01		02		03		04		05		06

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