PEM Fuel Cells for Submarines

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Fuel CellApplications forelectric energy

production

Emergency power supply(PEFC)

Frighter

Emission-free and noiselessoperation (PEFC)

Bus

Delivery trucks

Elektrischer Antrieb

Bahn

Energy storage with gases(PEFC)

Storage system forregenerative energies

Space Shuttle

Grid-independent operation(SOFC, PEFC)

DecentralPower plants

Railroad

H2/O2

Reformer gas/Air

H2/Air

Passenger car

Emission-free and energy-efficient operation (PEFC)

Electrical propulsion(SOFC, PEFC)

Air-independent power supply(PEFC)

Emission-free and noiselessoperation (PEFC)

Gas tanker

Electrical propulsion(SOFC, PEFC)

Air-independent propulsion(PEFC)

Submarine

Reformer gas/Air

Fig. 1: Possible applicationsfor generating electrical energy

Fuel cells allow the direct generation of electricpower from hydrogen and oxygen with a consid-erably better efficiency and no pollutant emissioncompared to conventional combustion engines.Their operation is noiseless.

In addition to these basic advantages, the fuelcell with a solid, ion conducting, polymeric mem-brane (Polymer Electrolyte Membrane – PEM)has further positive properties:

• Quick switch-on, switch-off behavior

• Low voltage degradation and long service life

• Favorable load and temperature cycle behavior

• Overload possibility

• Low operating temperature (80°C)

• Absence of a liquid corrosive electrolyte.

All these characteristics make the PEM fuel cell(PEM FC) an ideal power unit.Aboard submarines they show their outstandingadvantages against conventional AIP systems(Air Independent Propulsion) using oxygen andhydrogen, carried on board.

The new submarines of class U 212 A areequipped with PEM FC modules with an electri-cal output of 30 to 40 kW each, which have beendeveloped since 1985 on behalf of the GermanMinistry of Defense. The new type U 214 classsubmarines will be fitted with 120 kW fuel cell

modules which have been developed bySiemens in a next step.

The basic suitability of fuel celltechnology onboard submarineshas been demonstrated by

installing a 100 kW FC powerplant with alkalinefuel cells on thesubmarine U1 ofthe Federal GermanNavy in 1988.During the tests the

performance of additionalequipment such as H2

and O2 components has beenproven.

Further possible applications of PEM FCs forpower generation are listed below (see also Fig. 1, left side):

Using hydrogen and oxygen

• Operation in spacecrafts

• Component in a long-term energy storage system (consisting of solar cells, an electrol-yser system and a hydrogen/oxygen storagesystem)

Using hydrogen and air

• Zero emission operation of electrically drivenvehicles

Using reformer gas and air

• Power supply far distant from a public powersupply system

• Safe, low emission power supply on cargo vessels especially in harbor

• Utilization of boil-off gases aboard gas tankers

• Power supply e.g. for drives on rail vehicles

Concentrating on manufacture and developmentof fuel cells for AIP applications, Siemensdemonstrated its technological competence inprojects for air-breathing PEM fuel cells, e.g.

– Fork lift truck

– Micro co-generation

– Propulsion systems for busses.

The Siemens R&D activities in the fields of Direct Methanol Fuel Cells (DMFC) and SolidOxide Fuel Cells (SOFC) are not presented in thisbrochure.

Introduction

OxygenHydrogen

Energy

Water

3

Cover photo: 30–40 kW module (top)and 120 kW module (below)

Both the basic function and the designof the PEM FC are very simple (Fig. 2): the electrochemical element at whichthe chemical energy is converted intoelectrical energy is the membraneelectrode unit. It consists of the poly-mer electrolyte, the gas diffusion elec-trodes with a platinum catalyst andcarbon sheets on each side.

After the abstraction of the electronsfrom hydrogen – they flow from theanode via the electrical load to thecathode – the resulting protonsmigrate from the anode to the cathodewhere they combine with oxygen (andthe electrons) to water. The theoreticalvoltage of an H2/O2 fuel cell is 1.48 V(referred to the upper heat value ofhydrogen). At zero load conditions,slightly more than 1 V per cell is avail-able.

The cooling units or bipolar plates incombination with carbon diffusion lay-ers distribute the reactants uniformlyacross the area of the cell, conduct theelectrons across the stack, remove theheat from the electrodes and separatethe media from each other.

PEMfuel cell

Fig. 3: Components of cell Fig. 5: Comparison of cells: 120 kW type (front)30–40 kW type (back)

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Fig. 3 shows the two core compo-nents of a cell with outside dimen-sions of 400 mm x 400 mm. As usedin 30–40 kW modules.

Fig. 5 compares the bipolar plate ofthe 30–40 kW modules to the 120 kWtype. Two cells of the 120 kW typeproduce about twice the power of onecell of the 30–40 kW type with nearlythe same active area.

The in principle high developmentpotential in regard to the membranematerial is shown in Fig. 4. Withimproved materials the power densitycan nearly be doubled.

The voltage of a PEM FC referred tothe operating time is stable, degrada-tion rates are less than 2 µV/h for the30–40 kW module (Fig. 6).

Cooling unit

Membraneelectrode unit

Cooling unit

400 mm

1500

1000

500

Cel

l out

put

Pz

0

W

1.1

V

0.9

0.7

0.5

Cel

l Vol

tage

Uz

0 500 1000 1500 2000ACurrentI

TKW

pO2

pH2

pK

Aact

= ~80°C= 2.3 bar abs.

= 2.0 bar abs.

= 5.0 bar abs.

= 1163 cm2

Dow (G 29)

Naf 115 (D 14)

Naf 117 (A 37)

Dow

Naf 115

Naf 117

60

56

54

52

50

Modulevoltage

[V]

Degradation of voltage (single cell):(55.75-55.56V)/72cells/1.500h = 1.76µV/h

1000

500

0

ModuleCurrent [I]

55.75V 55.56V

Operating time [h]2000 600400 800 1500

pO2: 2,3 bar apH2: 2,0 bar aTemp.: 80° CFakt.: 1163 cm2

Zellenzahl: 72

Electrical load

Polymerelectrolyte

Product waterH2O + O2

OxygenO2

HydrogenH2

Waste heat

4e–

H+

Anode Cathode

H+

H+

H+

O2+4e–=

2H2O

20- -

20- -+4H+=

4e–=2H2–4H+

Fig. 2: Functional principle

Fig. 4: Potential output increase when using various electrolytes

Fig. 6: Voltage degradation referred to operating time(measurement from 30–40 kW module)

Fuel cell modules

Fuel cellpower plant

The fuel cells need additional auxiliariesfor their operation. The FC stack,valves, piping and sensors form the FCmodule, the corresponding moduleelectronics controls the proper opera-tion of the FC process. The ancillariescomprise the equipment for supplyingH2, O2 and N2, for reactant humidifica-tion, for product water, waste heat andresidual gas removal. The FC stack andthe ancillaries are installed in a contain-er which is filled with inert gas (N2) at3.0 bar abs. to prevent a release of H2

and/or O2 in the case of leakage.

The FC module can be operated at vari-ous static load currents. Currentsbelow 650 A for 30–40 kW modules orbelow 560 A for 120 kW modulesrespectively can be applied in continu-

ous operation. The output power/cur-rent characteristics for 30–40 kWmodules are shown in Fig. 7.

For currents above the rated currentthe loading time is limited due to theinsufficient heat removal at such work-ing points. Even loads up to the doubleof the rated current can be applied fora short time.

At the rated operating point, the over-all efficiency is approximately 59%referred to the lower heat value of H2

(LHV). It increases in the part loadrange, reaching a maximum of approxi-mately 69% at a load factor of some20% of the rated current (approx. 100 A) (Fig. 8).

The properties of the 30–40 kW and120 kW modules are listed in thetable.

Suitable operating conditions for fuelcell modules are provided for subma-rine application by a fuel cell system inwhich fuel cell modules are connected

• to the hydrogen and oxygen supply• to disposal units such as for

– cooling – residual gas– reaction water

• to auxiliary systems such as for– inert gas drying– nitrogen supply– evacuating system

• to the propulsion/ship’s system asthe purpose of the whole FC system.

Operator control and visualization ofthe fuel cell system is effected by theintegrated platform management sys-

tem, or directly by the control panel ofthe fuel cell system.Fig. 10 gives a simplified impression ofthe AIP system.

The fuel cell system in its entirety –the complete fuel cell power plant,especially the supply and disposal sys-tems described above for AIP opera-tion including spatial and functionalintegration on board – has been devel-oped by HDW (HowaldtswerkeDeutsche Werft AG).The new submarine classes U 212 Aand U 214 are equipped with the newfuel cell power plant by HDW with thePEM fuel cell modules by Siemens.

Fig. 9 shows PEM fuel cell modulesassembled in a test rack.

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Technical data

Rated power 30–40 kW 120 kW

Voltage, about 50–55 V 215 V

Efficiency atrated load 59% 58%

Efficiency at 20% load 69% 68%

Operatingtemperature 80°C

H2 pressure 2.3 bar abs.

O2 pressure 2.6 bar abs.

Dimensions H = 48 cm 50 cmW = 48 cm 53 cmL = 145 cm 176 cm

Weight (without moduleelectronics) 650 kg 900 kg

Propulsion switchboardFeeding of

propulsion/ship’s system

H2 supplyO2 supplyRemoval • Waste heat

• Product water• Residual gas

Integrated PlatformManagement System (IPMS)

FUEL CELLMODULES

Fuel cell systemControl panelModule electronicsControl and monitoring

kW

0

Mod

ule

outp

ut P

M

0 AModule current IM

TKW

pO2

pH2

pK

Aact

n

Membrane: Nafion 117

= ~80°C= 2.3 bar abs.

= 2.0 bar abs.

= 5.0 bar abs.

= 1163 cm2

= 72 Cells

60

200 400 600 800 1000

10

20

30

50

1200

40

%

0

Ove

rall

effic

ienc

y η

o

0 AModule current IM

TKW

pO2

pH2

pK

Aact

n

Membrane: Nafion 117

= ~80°C= 2.3 bar abs.

= 2.0 bar abs.

= 5.0 bar abs.

= 1163 cm2

= 72 Cells

100

100 200 300 400 500

20

40

60

80

600

After the successful developmentthe FC modules are now undermanufacturing. They have proventheir performance and reliability inextensive tests including long termtests. They are an integral part ofan AIP system for modern sub-marines like that of Class U 212 A(30–40 kW modules) and U 214 (120 kW modules).

The field for use of PEM FC willbe widened when suitable reform-ers produce hydrogen from liquidfuels, e.g. methanol. Then it maybe possible that fuel cells canbecome the sole power source of submarines of the future.

Using PEM fuel cells and replac-ing oxygen with air, they are aninteresting alternative for environ-mental-friendly power generation,e.g. for vehicles in cities.

In general: the excellent operatingperformance of PEM fuel cells likehigh efficiency and noiseless oper-ation can lead to a promisingfuture upon further reduction inmanufacturing and operatingcosts.

Fig. 7: Module output referred to load current(measurement from 30–40 kW module)

Fig. 8: Efficiency (measurement from 30–40 kW module)

Fig. 10: Integrated AIP system

Outlook

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Fig. 9: PEM fuel cell modules assembled in a test rack

Order No. E10001-A930-A35-V3-7600Dispo No. 16600Printed in Germany174D6077 PA 08012.

OurProgram

Systems Engineering andQuality Management

Propulsion Systems

Air-IndependentPropulsion (AIP)

Electrical Systems

Integrated Platform Management System

Auxiliary Systems

Engineering

Logistics

Service

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