Feature 5
design, the fuel-cell system size would be Hybrid SSN/FC
PEM
signifi cantly greater than that in Option FC/LYSER submarine fuel-cell
2, which would be sized for emergency system schematic.
power only.
H2 METAL HYDRIDE
(DIS)CHARGING TANKS
In order to fully explore the concept of a
DC BALANCE
DISTRIBUTION OF PLANT
hybrid nuclear/fuel-cell submarine Option 3
SYSTEM SYSTEMS
O2 COMPRESSED
was selected for further investigation.
COMPRESSOR O2 TANKS
Fitting fuel cells to a submarine results
in a significant operational advantage.
DEMIN
With both hydrogen and oxygen stored WATER TANKS
onboard, a fuel-cell-equipped SSK can
remain submerged for many weeks without
the requirement to snorkel and run diesel
generators with the attendant signature hull breach; removal of dangerous (in a thus significantly reducing the required
issues (noise and visual signature of the fi re) hydrocarbon fuel; nil emissions when battery size, whereas diesels can only be run
snort induction and diesel exhaust masts). on auxiliary power source and therefore once the submarine reaches the surface and
Whilst a SSN has no requirement to snort, future-proof to IMO legislation; easier the snort mast has been raised. In general
and can therefore remain submerged build and maintenance as the components these points give the platform greater
indefinitely, the noise of continually of the fuel-cell system are small and can fl exibility and reduce the risk of mission
running pumps and the large quantity of be removed through existing hatches. Th e compromise. However, the limited energy
waste heat rejected to the sea signifi cantly exception is the metal hydride cylinders, density of hydrogen and oxygen storage
increase the submarine’s signature. depending on whether they are located results in a lower fuel-cell range than that
A fuel-cell-equipped SSN could shut internally or externally. Th is is in contrast available from diesel generators.
down the reactor for quieter performance to diesel engines, which require hull cuts
during operational patrols, remain on task for removal. Submarine characteristics
following a scram - giving ships staff time Other potential benefits include the In the absence of a defi ned operational
to rectify the defect and recover to normal fact that, during an emergency surface, requirement a number of assumptions
reactor operation - and maintain a fully compressed oxygen tanks could contribute were made as to the SSN’s role, size
air-independent auxiliary power source for to emergency blow air, and there would be no and power requirements. The exact
under-ice operations. requirement for oxygen candles in a DISSUB displacement was not required but
Other benefi ts that would accrue from environment, thus reducing the potential for was assumed to be similar to a small
such a design include: removal of diesel fi re and explosion. Moreover, fuel cells can SSN/large SSK (Rubis/Collins class,
exhaust mast with associated large-pressure be rapidly ‘switched on’ following a scram, that is, 2000–3000tonnes), making it
Volume (litre) and mass (kg)
-3
State Symbol Atomic mass Density kgm
per kg of Hydrogen
Hydrogen Gas (STP) H 2.016 0.095 10,500 1.00
2
Hydrogen Gas(250bar) H 2.016 23.75 42.00 1.00
2
Hydrogen Liquid (70K) H 2.016 71 14.08 1.00
2
Water Liquid H O 18.015 1000 8.94 8.94
2
Methanol Liquid CH OH 32.042 794 10.01 7.95
3
Ethanol Liquid C2H OH 46.068 798 9.55 7.62
5
Dodecane (Diesel)* Liquid C H 170.340 748 8.69 6.50
12 26
Liquid (300K
Ammonia NH 17.032 623 9.04 5.63
10bar)
3
Titanium hydride Solid TiFeH 105.763 5470 9.59 52.46
2
* Dodecane is accepted as a representative average of the many constituents of Diesel.
Comparison of hydrogen vectors (excludes containment vessel).
Warship Technology October 2008 43
WT_Oct08_p42+43+44+46+47+50+
51.indd Sec1:43 10/10/08 1:17:15 PM
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