NIGERIAN NAVAL ENGINEERING

COLLEGE SAPELE

MARINE ENGINEERING SCHOOL

OAC 14/SDOC 09

FUEL CELL APPLICATION IN THE

PROPULSION OF NAVAL VESSELS

BY

SLT O GOGOGWUTE NN/3594

APRIL 15

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RESEARCH REPORT ON THE APPLICATION OF A FUEL CELL TO PROVIDE POWER FOR THE

PROPULSION AND SERVICES FOR A NAVAL VESSEL

INTRODUCTION

1. Basic propulsion for marine vessel normally comes from an engine driving a crank shaft, turning

a propeller. In many vessel when the entire engine output is used on the propellers, for propulsion, a

generator is then used to provide electrical requirements. The engines and generators are heavy duty

diesel powered machines which are robust, reliable and work in testing conditions. Unfortunately they

can also produce a now unacceptable level of pollution, are very noisy, heavy, and can take up a large

amount of room including the rising price of fuel. These challenges and the impending environmental

regulations have created a pressure for ships to operate more efficiently, in an environmentally friendly

manner and with more stringent safety and reliability requirements. The main drivers for developing

maritime fuel cell technology are reduction in fuel consumption and less local and global impacts of

emissions to air from ships. Additional benefits include insignificant noise and vibration levels, and

lower maintenance requirements compared with traditional combustion engines.

2. NNS NWAMBA is used as a conceptual study guide in this research. NNS NWAMBA is a

military vessel belonging to the Nigerian Navy and shares many common features with other Naval

vessels especially the CAT class vessels. The space available on this ship and the accessibility of the

information due to the fact that the researcher served onboard the ship make it a good candidate to

evaluate the possibility of applying fuel cells to provide propulsion and services for naval vessels.

Function: NNS NWAMBA is a buoy tender by design but that function has been replaced. the

vessel now functions to patrol the waterways and to provide logistics to other vessels at sea.

To power the ship up to 13.5 knots (Max Speed), while supporting all the auxiliary machinery and

service loads, a total power of 1.5 MW is installed. This power is supplied by 2 x main diesel engines,

(for propulsion) and 2 x Ship service diesel generator sets (for auxiliary power). This implies that the

fuel cell needed to provide power for propulsion and service of a similar Naval vessel with the same

characteristics must be able to produce at least a minimum power of 1.5 MW

AIM

3. The aim of this report is to highlight the concept of fuel cell in order to evaluate the possibility of

its applications in propulsion and services of Naval Vessels.

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SCOPE

4. To achieve the above aim, this report will cover the following areas:

a. Technological Background of Fuel Cell

b. Basic principle of fuel cell.

b. Types of fuel cell.

c. Justification for the most suitable type of fuel cell.

d. Fuelling strategy.

e. Estimate size and weight of fuel cells and associated storage/supply equipment.

f. Requirements for electrical connection between fuel cell and electric motor.

g. Advantages and disadvantages compared to more conventional power plant.

h. Conclusion and recommendation.

TECHNOLOGICAL BACKGROUND OF FUEL CELLS

5. The fuel cell looks back on a long track record. It was initially observed in 1839 by Sir William

Grove while he was experimenting with the electrolysis of water. He reversed the electrolysis process,

reacting oxygen with hydrogen to produce electricity. His fuel cells featured electrodes made of

platinum sitting in a glass tube with their lower end immersed in dilute sulfuric acid as an electrolyte and

their upper part exposed to hydrogen and oxygen inside the tube. This was sufficient to produce a

voltage of 1 volt. Ludwig Mond and Charles Langer tried to build the first practical device in 1889 using

air and industrial coal gas. Francis Bacon made improvements to that model and invented the first

successful fuel cell device in 1932. It was a 20- horsepower fuel cell-powered tractor. In the late 1950’s,

NASA explored the use of fuel cell technology to develop a power source for space travel and,

ultimately, in the space shuttle program and space stations.

6. Today, it is on the point of ship propulsion use. Many studies on marine fuel cell applications

have been published and several successful technology demonstrations have been showcased by the

academic research and industrial or development communities. Among them, the fuel cell ship service

system sponsored by the Office of Naval Research, the Methapu and Fellowship under the European

Commission are representative examples. Most of the fuel cell studies and demonstration programs

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target auxiliary power applications, with some exceptions such as the submarine program and small

pleasure boats where the fuel cells are used for propulsion. In this study, however, the research is

focused on exploring the fuel cell as the primary power source for patrol vessels with moderate space

limitations such as the military vessels ( NNS NWAMBA) in order to understand the technology

potentials and limitations.

BASIC PRINCIPLES OF FUEL CELL

7. A fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has two

electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions

that produce electricity take place at the electrodes. Every fuel cell also has an electrolyte, which

carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the

reactions at the electrodes. Hydrogen is the basic fuel, but fuel cells also require oxygen. One great

appeal of fuel cells is that they generate electricity with very little pollution–much of the hydrogen and

oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water. A

single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are

usually assembled into a stack cell or stack, the principles are the same.

8. The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell

to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way

electricity behaves, this current returns to the fuel cell, completing an electrical circuit. The chemical

reactions that produce this current are the key to how a fuel cell works. There are several kinds of fuel

cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the

anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now "ionized,"

and carry a positive electrical charge. The negatively charged electrons provide the current through

wires to do work. If alternating current (AC) is needed, the DC output of the fuel cell must be routed

through a conversion device called an inverter.

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Diagram showing the basic principle of Fuel Cell

(Graphic by Marc Marshall, Schatz Energy Research Center)

9. Oxygen enters the fuel cell at the cathode and, in some cell types (like the one illustrated

above), it there combines with electrons returning from the electrical circuit and hydrogen ions that have

traveled through the electrolyte from the anode. In other cell types the oxygen picks up electrons and

then travels through the electrolyte to the anode, where it combines with hydrogen ions. The electrolyte

plays a key role. It must permit only the appropriate ions to pass between the anode and cathode. If

free electrons or other substances could travel through the electrolyte, they would disrupt the chemical

reaction. Whether they combine at anode or cathode, together hydrogen and oxygen form water, which

drains from the cell. As long as a fuel cell is supplied with hydrogen and oxygen, it will generate

electricity. Even better, since fuel cells create electricity chemically, rather than by combustion, they are

not subject to the thermodynamic laws that limit a conventional power plant. Therefore, fuel cells are

more efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed,

boosting system efficiency still further.

TYPES OF FUEL CELLS

10. There are many fuel cell types, but the principal ones include the alkaline fuel cell (AFC), proton

exchange membrane (PEM) fuel cell, molten carbonate fuel cell (MCFC), phosphoric acid fuel cell

(PAFC), and solid oxide fuel cell (SOFC. Each fuel cell type has its own unique chemistry, such as

different operating temperatures, catalysts, and electrolytes. A fuel cell’s operating characteristics help

define its application – for example, lower temperature PEM and DMFC fuel cells are used to power

passenger vehicles and forklifts, while larger, higher temperature MCFC and PAFC fuel cells are used

for stationary power generation. Researchers continue to improve fuel cell technologies, examining

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different catalysts and electrolytes in order to improve performance and reduce costs. New fuel cell

technologies, such as microbial fuel cells, are also being examined in the lab. The following list

describes the five main types of fuel cells;

a. Alkaline Fuel Cells: Alkaline fuel cells operate on compressed hydrogen and oxygen.

They generally use a solution of potassium hydroxide (chemically, KOH) in water as their

electrolyte.

Efficiency is about 70 percent, and operating temperature is 150 to 200 degrees C, (about 300

to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW). Alkali cells were

used in Apollo spacecraft to provide both electricity and drinking water. They require pure

hydrogen fuel, however, and their platinum electrode catalysts are expensive. And like any

container filled with liquid, they can leak.

b. Proton Exchange Membrane (PEM) Fuel Cell: Proton Exchange Membrane (PEM)

fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. Efficiency is

about 40 to 50 percent, and operating temperature is about 80 degrees C (about 175 degrees

F). Cell outputs generally range from 50 to 250 kW. The solid, flexible electrolyte will not leak or

crack, and these cells operate at a low enough temperature to make them suitable for homes

and cars. But their fuels must be purified, and a platinum catalyst is used on both sides of the

membrane, raising costs.

c. Molten Carbonate Fuel Cell (MCFC): Molten Carbonate fuel cells (MCFC) use high-

temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO3) as

the electrolyte.

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Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C

(1,200 degrees F). Units with output up to 2 megawatts (MW) have been constructed, and

designs exist for units up to 100 MW. The high temperature limits damage from carbon

monoxide "poisoning" of the cell and waste heat can be recycled to make additional electricity.

Their nickel electrode-catalysts are inexpensive compared to the platinum used in other cells.

But the high temperature also limits the materials and safe uses of MCFCs–they would probably

be too hot for home use. Also, carbonate ions from the electrolyte are used up in the reactions,

making it necessary to inject carbon dioxide to compensate.

d. Phosphoric Acid Fuel Cell (PAFC): Phosphoric Acid fuel cells (PAFC) use

phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating

temperature is between 150 to 200 degrees C (about 300 to 400 degrees F). Existing

phosphoric acid cells have outputs up to 200 kW, and 11 MW units have been tested. PAFCs

tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of

fuels they can use.

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If gasoline is used, the sulfur must be removed. Platinum electrode-catalysts are needed, and

internal parts must be able to withstand the corrosive acid.

e. Solid Oxide Fuel Cell (SOFC): Solid Oxide fuel cells (SOFC) use a hard, ceramic

compound of metal (like calcium or zirconium) oxides (chemically, O2) as electrolyte.

Efficiency is about 60 percent, and operating temperatures are about 1,000 degrees C (about

1,800 degrees F). Cells output is up to 100 kW. At such high temperatures a reformer is not

required to extract hydrogen from the fuel, and waste heat can be recycled to make additional

electricity. However, the high temperature limits applications of SOFC units and they tend to be

rather large. While solid electrolytes cannot leak, they can crack.

JUSTIFICATION FOR THE MOST SUITABLE TYPE OF FUEL CELL

11. Each fuel type is well-suited for specific applications. A typical fuel cell produces a voltage from

0.6 V to 0.7 V at full rated load. To deliver the desired amount of energy, the fuel cells can be combined

in series to yield higher voltage, and in parallel to allow a higher current to be supplied. Such a design is

called a fuel cell stack. Additionally, given the nature of the shipboard loads to be served by the power

plants, the future fuel cell power systems should have the following characteristics which, in turn, will

dictate the decision on the fuel cell technology and configuration selection.

a. High power density for large scale power application (mega-watts level).

b. Simple reforming and fuel processing requirements.

c. Capability of combined-heat-power-steam generation to support electrical, heat, and

steam loads that co-exist onboard the ship.

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These requirements naturally lead to high temperature fuel cell technologies, among which the solid

oxide fuel cells (SOFCs) are considered as the most promising one. High temperature fuel cells offer

higher system efficiency and higher power density, compared to low temperature fuel cell technologies.

They also allow more flexibility in their fueling strategy, thanks to the internal reforming capability

offered by high temperature operation. This report therefore propose a solid oxide fuel cell system as

the most suitable power module for propulsion and services of Naval vessel. The SOFC system

module, which will be the building block for the proposed power plant, has the capacity of generating an

electrical power output range of 1KW to 2 MW with efficiency of 50% and volumetric density of 40

W/liter. This is within the power range generated by the two main Detroit diesel engines used for the

propulsion of NNS NWAMBA(the conceptual guide) which is about 1050KW Here only one SOFC

module is required to produce a total electrical net output power of 1.5 MW for the power plant since

the ship requires only 1.05 MW for its propulsion and 0.3 MW for other major loads such as the Bow

thruster and Air conditioning system including cargo handling. Also the choice of solid oxide fuel cell as

a means of propulsion of NNS NWAMBA was informed by the following characteristics of the vessel for

which Solid oxide fuel cell will conveniently take care of.

General Characteristics of NNS NWAMBA

Hull form Steel

Length overall 58.86 m

Beam 11.34 m

Draught 3.60 m

Service Speed 13.5 Kts

Displacement (loaded) 1088 Tons

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Power Plants Base of NNS NWAMBA

Propulsion 2 x 525 kw = 1.05 MW

Ship Service Diesel Engine 2 x 200 kw = 400 MW

Emergency Diesel Generator 1 x 50 kw

Total Power 1.5 MW

FUELLING STRATEGY (eg STORED HYDROGEN OR FUEL REFORMER)

11. Fuel processing is defined as conversion of the primary fuel (gaseous or liquid hydrocarbons)

supplied to a fuel cell system to the fuel cell gas H2 supplied to the stack. Fuelling strategy involves the

various methods of making hydrogen ( H2) which is the major fuel for the Fuel cell available. Hydrogen

is the most abundant element in the universe. It’s a component in a wide variety of compounds (CH4,

H2O etc.), but is rarely found in our natural world as H2 – the form we need for a fuel cell. Thus, we

need to make hydrogen to supply the H2 fuel required for a fuel cell vessel. It must be produced from

the following sources:

a. Fossil fuels: natural gas, petroleum (gasoline, diesel, JP-8), and coal and coal gases.

b. Biofuels (such as produced from biomass, landfill gas, biogas from anaerobic digesters,

syngas from gasification of biomass and wastes, and pyrolysis gas; generally they contain

mixtures of CH4, CO2 and N2, together with various organic materials)

c. Chemical intermediates (methanol, ethanol, NH3, etc,).

d. Renewable energy sources, such as solar, wind, hydro, geothermal, etc. from which

electricity is generated (which is a non-continuous supply) and is used to electrolyze water to

generate hydrogen.

ESTIMATE SIZE AND WEIGHT OF FUEL CELLS AND ASSOCIATED STORAGE/SUPPLY

EQUIPMENT

13. The size of fuel cell installations varies with the type of technology chosen. however, in terms of

volume and weight per KW installed, it will be hard to compete with combustion engines, especially for

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Fuel Cell types that require a complex balance of plant. Below is a table showing the characteristics

properties of two fuel cell type and two types of combustion engines.

Electric Power

System

Electric Efficiency Specific Power

(kw/m2)

Power Density

(w/kg)

Fuel Cell (MCFC) 45-50 3 15

FuelCell (SOFC) ~ 45 30 50

Marine Diesel Engine

(4-stroke)

40 80 90

Marine Gas (4-stroke) 45 80 90

Table showing the characteristics properties of two fuel cell and two combustion engines: Numbers are

roughly estimated based on the available product documentation for Fuel Cell and DNV internal Report

NO 2010 - 0605 for combustion engine.

Fuel Cell Storage

a. Gaseous Storage: Due to the high pressure and temperature of stored gases, carbon-

fibre composite tanks are used. Pressure in the tank can be up to 350bar.Gas is retained at room

temperature and released at 200-300oc.

b. Liquid Storage: Liquid storage is at -253oc and permits high gravimetric density.

c. Solid Storage: The most suitable materials for solid storage are metal hydrides, having

storage capacity exceeding 8wt%.

Hydrogen can be stored in extremely strong fibre cylinders because, it diffuses very rapidly, any

spill will dissipate quickly. Other methods of storing hydrogen include:

i. The use of metal hydride reaction with water.

ii. Using an irreversible metal hydride.

iii. Storage in a cryogenic liquid.

iv. The use of carbon-fibre.

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REQUIREMENTS FOR ELECTRICAL CONNECTION BETWEEN FUEL CELL AND ELECTRIC

MOTOR.

14. Fuel Cell installation for ship propulsion and services is a wholesome system that involves the

process of production and storage (in some cases) of hydrogen and the various stages of power

production and delivery. This whole system is called Balance of Plant (BOP). the balance of plant is

made up of the following components; inverter, control electronics, humidification, H2 and air

pressurization, cooling systems, electric motor, H2 storage system. The energy or power produced by

fuel cell is electrical power and is a direct current (DC). in this case, the SOFC delivers electrical power

to a direct current (DC) link that is connected to the ship's alternating (AC) bus through power

converters. The converters are connected to the main motor which convert this electrical power to

mechanical power to drive the propulsion system.

ADVANTAGES AND DISADVANTAGES COMPARED TO MORE CONVENTIONAL POWER PLANT

Advantages

15. The main advantages of fuel cells over other conventional propulsion systems are:

a. Efficiency: Fuel cells are generally more efficient than combustion engines as they are

not limited by temperature as is the heat engine.

b. Simplicity: Fuel cells are essentially simple with few or no moving parts. High reliability

may be attained with operational lifetimes exceeding 40,000 hours (the operational life is

formally over when the rated power of the fuel cell is no longer satisfied).

c. Low emissions: Fuel cells running on direct hydrogen and air produce only water as the

byproduct. Fuel cell vessels that use an on-board fuel reformer will emit two-thirds less pollution

than a gasoline combustion engine. A similar comparison applies to stationary and portable fuel

cell applications.

d. Silence: The operation of fuel cell systems are very quiet with only a few moving parts if

any. This is in strong contrast with present combustion engines.

e. Flexibility: Modular installations can be used to match the load and increase reliability of

the system.

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f. Versatile: Fuel cells can operate on a wide load range and scale from micro production

to megawatt production.

Disadvantages

a. Cost: The principal disadvantages of fuel cells, however, are the relatively high cost of

the fuel cell and to a lesser extent the source of fuel. The cost of fuel cell power systems must

be reduced before they can be competitive with conventional technologies.

b. Durability and Reliability: The durability of fuel cell systems has not been established.

For transportation applications, fuel cell power systems will be required to achieve the same

level of durability and reliability of current automotive engines, i.e., 5,000 hour lifespan (241,000

km equivalent), and the ability to function over the full range of vehicle operating conditions

(40°C to 80°C). For stationary applications, more than 40,000 hours of reliable operation in a

temperature at -35°C to 40°C will be required for market acceptance.

c. System Size: The size and weight of current fuel cell systems must be further reduced to

meet the packaging requirements for automobiles. This applies not only to the fuel cell stack,

but also to the ancillary components and major subsystems (e.g., fuel processor,

compressor/expander, and sensors) making up the balance of power system.

d. Air, Thermal, and Water Management: Air management for fuel cell systems is a

challenge because today's compressor technologies are not suitable for automotive fuel cell

applications. In addition, thermal and water management for fuel cells are issues because the

small difference between the operating and ambient temperatures necessitates large heat

exchangers. Another challenge is to develop a reliable and durable membrane that operate in

low humidity conditions so as to eliminate the need for complicated water management

equipment.

e. Improved Heat Recovery Systems: The low operating temperature of PEM fuel cells

limits the amount of heat that can be effectively utilized in combined heat and power (CHP)

applications.

CONCLUSION

16. This report showed that a fuel cell powered military vessel is possible. it also documents that

such vessel has tremendous potential in reducing fuel consumption and NOx emissions. The

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associated economic and environmental benefits present a great incentive for naval and maritime

industry to pursue fuel cell technology for the next generation green ships. The extended range and

improved endurance of SOFC, together with the reduced fuel cost and environmental impact, also

represent a unique opportunity for military sealift ships. The study also revealed that a minimum power

requirement of 1.5 MW has to be achieved in order to meet the vessel power requirements under the

existing characteristics. It should be pointed out that this level of power density for SOFC has not been

achieved by the state-of-the-art technology, even at a much lower power scale.

16. Large technology gaps exist, and provide opportunities for development in all associated areas,

including stack development, system integration, and control, just to mention a few. Fuel cell

technology has recently been proven successful in large maritime demonstration projects. Although fuel

cell technology is not new, this success means that it has become relevant to discuss the potential for

fuel cell technology in on-board applications and the advantages and disadvantages of fuel cell

compared to more conventional power plant as done in the present paper. This paper also discusses

certain justification for the most suitable type of fuel cell, fuelling strategy (eg stored hydrogen or fuel

reformer), requirements for electrical connection between fuel cell and electric motor.

RECOMMENDATION

17. This research also led to many open questions that warrant further investigation. The following

efforts are recommended as follow up activities to complement, substantiate, or extend this study:

a. That more time be given for research of this nature to enable detailed information.

b. That more effort be made in the storage strategy.

c. That modeling and methodology for system optimization and design be developed.

c. That comprehensive performance of weight/space analysis is carried out.

d. That enough effort be made for large scale production in order to reduce cost. Currently,

the cost of fuel cell systems is greater than that of similar, already available systems.

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