International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 6

Number 4

December 2012

1 INTRODUCTION

The shipping industry has come a long way using

combustion engines in transporting goods between

continents, but in general the transportation sector

accounts for a large fraction of air pollutant

emissions. Health and environmental effects of air

pollutants such as NOx, CO, VOCs, and particulates

are leading to stricter tailpipe emissions regulations

worldwide. [1, 2]. Virtually all transportation fuels

today are derived from oil. Oil production is

projected to peak worldwide within a decade and

there no guarantee that oil will be enough for

worldwide increase in consumption.

New frontiers have opened in the application of

hydrogen as fuel for ships. A hybrid research ship

[3], this research ship turns silent when scientists

start recording whale songs. A 42-m long slick,

hydrogen yacht with sufficient power was reported

in [4].

This paper is a step toward resolving the

integration of three main components required to

design and discuss the concept of a large power

hydrogen powered ship; the hydrogen fuel cell, the

electronic drive and a uniquely designed motor. The

uniqueness of the design is in integration 100kW,

250kW and the latest 4MW solid oxide fuel cells [5]

to energize each pole of a sixty pole induction

motor, assuming the drive system provides sixty Hz.

There is no doubt that there is much work to be

done in order to establish a hydrogen based shipping

industry, but the technology to initiate the

transformation is in place.

The fact that the process and the technology is in

place will require a resolution on how the new

industry should be developed. The overall idea of a

shipping economy based on hydrogen is discussed in

[6,7].

Integrating Modular Hydrogen Fuel Cell Drives

for Ship Propulsion: Prospectus and Challenges

P. Upadhyay, Y. Amani & R. Burke

SUNY Maritime College, Bronx, NY, USA

ABSTRACT: This paper proposes a new drive system for the ship propulsion. The drive power for propelling

ship varies from few MW in a small cruise ship to hundreds of MW for large cargo ships. A typical cruise

ship has a 6 MW drive whereas a cargo ship has 80 MW drive. Combustion drives are not sustainable and

environment friendly. An idea of electric drive system using hydrogen fuel cell and necessary storage has

been proposed. The hydrogen reformer develops hydrogen fuel cell using off-shore renewables like Wind,

Wave and Solar power but the power handling capability of this fuel cell system (100 kW) restricts the

application to the propulsion drives of several MW. The detail drive scheme describing; how multiple

modular hydrogen fuel cell drives are integrated to develop variable power. The different options available for

the propulsion system and factors affecting the choice are discussed in detail. Also, how such modular drives

are helpful in controlling torque and power requirements is discussed. Replacement of electric drive reduces

volume and weight of the ship and the available volume can be utilized for the storage and reform systems.

The proposed paper will give a remarkable concept to overcome the challenges of utilizing hydrogen fuel cell

to the larger scale and in future it can be extended to all other applications.

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2 HYDROGEN FUEL CELL

Energy can be stored in variety of forms, but clean

energy production from natural sources such as

wind, tidal, waves and sun are abundant, but need

storage to be utilized when needed. The electric

power produced by all means is used to split water

into hydrogen and oxygen. Hydrogen could be

stored in high pressure tanks, these tanks are getting

smaller to a degree that it could be utilized in ship

design. The DOE hydrogen program reports, tube

trailer delivery capacity of 700kg by 2010 and

1,100kg by 2015 at 8300psi. Note that heating

energy in hydrogen is 33.33kWh/kg, for methane it

is 13.9-kWh/kg and for petroleum 12.4kWh/kg. To

travel 400km, a modern combustion vehicle needs

24-kg of gas, 8-kg of hydrogen in hydrogen

combustion engine and 4-kg of hydrogen in a fuel

cell, electric drive vehicle.

A hydrogen fuel cell is a device that converts

hydrogen to electricity. The device exhausts pure

water and heat in the process of this transformation.

Fuel cell technology has improved to a degree that

many car companies are introducing new models of

commercially available hydrogen cars. DOE

projection of hydrogen fuel cell prices have been

achieved, as this market expands the fuel cell prices

will be much lower than DOE projection. Figure 1

depicts price trends for hydrogen fuel cell.

Fig. 1 Price Trend for Hydrogen Fuel Cell

To completely demonstrate the feasibility of the

hydrogen based economy a model cargo ship,

sixteen to twenty two mega watts should be

constructed using hydrogen fuel cells with

possibility of on board hydrogen reforming,

production and storage.

To supplement hydrogen, we propose an

aerodynamic cargo model ship with retrieving solar

panels and small onboard wind turbines to produce

power needed for in house hydrogen reformers.

Hydrogen production and dispensing is done by

creating small scale hydrogen producing platforms,

containing solar, wind, and wave energy conversion

mechanisms. The electric energy produced is used to

split water into hydrogen and oxygen. These

platforms also house a fueling station and limited

storage for hydrogen. A typical MERP- Marine

Energy and Refueling Ports is depicted in fig.2.

Using technology developed for automobile

hydrogen refueling stations and applying it to

Marine Energy and Refueling Port (MERP) is

feasible, however, more studies need to be

conducted to relate the two systems. Here are a few

proposed models:

1 The first model is suitable to coastal areas where

a hydrogen pipeline is part of an existing infra-

structure to bring energy to urban and coastal are-

as. The MERP’s can be integrated into this sys-

tem and could simply contain small storage and

fueling stations.

2 The second model is based on a distributed, small

scale local supply for hydrogen shipping. This

model encourages complete reliance on renewa-

ble energy resources such as tidal, wind, solar

and, where available, wave energy.

3 Designing and utilizing mobile hydrogen produc-

ing ships equipped with wind turbines and hydro-

gen reformers. These mobile vessels could catch

high winds and produce hydrogen and could also

serve as on the way mobile refueling stations.

Marine Energy & Refueling Ports are envisioned

as non-intrusive, small islands attached to coasts or

in off-coastal areas where maximum energy yields

can be harvested from wind, wave and tidal currents.

Such an MERP will house a compatible hydrogen

reformer, low pressure hydrogen storage and a

fueling station. In addition, these structures should

house a vertical axis wind turbine, a vertical axis

tidal turbine, photo voltaic panels and the

appropriate electronics necessary for the control and

conversion.

Fig. 2 Marine Energy & Refueling Port

Electric drives for ships are well developed and

require little change when coupled to hydrogen fuel

cells. The design proposed in this paper is an attempt

to show how the technology developed for cars

could be transferred to ship design.

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3 ALL-ELECTRIC SHIP CONCEPT

Combustion drives will not be sustainable over the

future and are not environmentally friendly. The

electric drive system for the ship propulsion

proposed in this paper has the advantages of [8]:

− Efficient and Improved life cycle cost

− High Power/volume and Power/weight ratio i.e.

high payload of vessel

− Less propulsion noise and vibrations

− Ease of speed control

− Flexibility in thruster device locations

All-electric ships using fossil fuels are a present

day reality. This concept leads to designs which can

use on-board electric power for effective and

efficient propulsion, while auxiliary systems usually

are converted to electrical power. This “single bus”

ship can thus allocate power as needed according to

the mission profile of the vessel. Electric propulsion

has been applied to different types of ships, such as

cruise vessels, ferries, dynamically-positioned drilling

vessels, thruster assisted moored floating production

facilities, shuttle tankers, cable layers, pipe layers,

icebreakers, supply vessels, and naval vessels.

There

are many different configurations available for the

propulsion systems.

In conventional all-electric ship design

configurations, sets of engine-generators produce

electric power that is distributed for all auxiliary and

main propulsion systems as shown in fig. 3. The

system is approximately about as efficient as

conventional non-electric drives, but the costs of

generators, motors and static drives can make this

solution expensive [9]. The operational benefits and

the advantages of design flexibility justify such

additional costs.

Fig.3 On-ship Power generation distribution and Propulsion

Motor Controls

Fig.4 Different Propulsion drive configurations

In these configurations, the power developed by

all generators is supplied to a common bus. Then the

ship propeller is supplied power through

transformers and converters as shown in fig.3.

Typically, for twin-screw ships, each propeller is

controlled by a single motor drive as shown in fig.

4(a). Other common schemes used for E-Ship

propulsion are shown in fig.4. A two winding motor

with redundant converters is shown in fig. 4(b), in

which the redundant winding is supplied through

another power electronic converter. Fig.4 (c) shows

Tandem motor with redundant converters, and fig.4

(d) shows a geared dual shaft propulsion drives in

which, two motors are coupled to the propeller

through a gear [10]. The application of these

configurations depends on size and type of the ship.

4 HYDROGEN FUEL CELL BASED DRIVE

As discussed in section-1, the limitation of hydrogen

fuel cell is to supply power at the level of 100 kW.

For conventional diesel-generators and fuel based

generators, one of the configurations discussed in

section 3 can be used. Also, for boats and small

ships, it is easier to handle propulsion power through

one of the schemes shown in fig. 4. For cargo ships

having power requirements much greater than 5

MW, it is difficult to address the challenge of

making the ship all electric-ship utilizing hydrogen

fuel cells. Two configurations are proposed in this

paper namely (a) distributed modular generators, and

(b) modular drive operation. Following section

discusses each of the schemes in detail.

4.1 Distributed modular generators

A distributed modular generation configuration is

shown in fig. 5. It is possible to mount the hydrogen

fuel cell (FC) modules in a distributed form in the

ship. An AC bus can run through the ship and all

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power is generated by fuel cells (FC) and controlled

by a power electronic (PE) converter is supplied to

this bus. A transformer provides the higher voltage

required for the propulsion motor. The auxiliary

supply can be met by either the similar fuel cell or

using diesel-generator set. This configuration is

advantageous when the fuel cells are located as

distributed form. Control of each individual fuel cell

power generator module is a challenge if they are

located as distributed manner.

Fig. 5 Distributed Hydrogen Fuel Cell Power generations and

Propulsion Motor Controls

4.2 Modular drive operation.

Fig. 6 100 kW Hydrogen FC power module

Another scheme is to place all hydrogen fuel cells

centrally. Each of FC produces power in order of

100 kW. The PE module designed to work at low

power rating of 100 kW, can control power flowing

to the stator of the main motor as shown in fig. 6.

The sensors measure speed, position, load current

and all necessary control parameters. The controller

senses all these signals and send signals to centrally

located control station for monitoring and control

action. The controller also develops control pulses

for the FCs, PE converters, and inverters. All these

modules are synchronized with motor parameters.

Due to low power and voltage ratings, the cost of

this module is low as compared to developing large

rating PE converters discussed in section 4.a, and a

transformer is not required to boost the ac voltage.

A typical small ship may have a 6 MW drive

whereas a large cargo ship has an 80 MW drive [5].

To control 6 MW propulsion power, sixty such

modules are placed as shown in fig.5. All these

modules are integrated through a centralized

distributed control system. For higher power

applications, Permanent Magnet Synchronous

Motors (PM SMs) could be employed. The

advantages of PMSMs include high efficiency, ease

of control, and high torque/weight ratio. Due to

reductions in the cost of rare-earth magnets, these

machines have lower payback periods. Thus,

designers may select among alternative

configurations depending upon the size and type of

application for ship propulsion.

Fig. 6 Integrating Modular Hydrogen Fuel Cell Drives for ship

Propulsion

5 SIZING EQUATION FOR PERMANENT

MAGNET PROPULSION MOTOR

The output equation for the radial-flux PM BLDC

motor is derived based on the expressions for the

torque and back emf [11];

phphcmr

IENTP

ηω

(1)

phphc

IEN

(2)

By substituting the values of induced emf in the

above equation, the torque is given as;

550

)2/(

srogwsppmc

phmsrogwsppmc

ILDBKNNN

InLDBKNNN

ωη

(3)

sgwsppmc

IBKNNN

(4)

The rated power output is the product of

efficiency, phase voltage, phase current and the

number of coil conducting simultaneously. The

output is also given by the product of developed

torque and the motor speed in rad/sec. Comparing

the two and simplifying the equation the output

equation for the radial-flux PM BLDC motor can be

obtained. A specific slot loading I

can be considered

for the output equation. The LD

product depends

on the torque developed by the motor, specific

magnetic loading, specific slot loading, and the

efficiency as shown below;













spp

(5)

Output equation relates the physical dimensions

of the radial-flux PM BLDC motor with the power

output, speed, assumed efficiency, number of phases

conducting simultaneously, number of magnet poles,

slots per pole per phase, winding factor, assumed

magnetic loading and assumed electric loading [11].

For the rated power of 6 MW, 100 rpm, 1000 V

per drive module, 60 poles, 3 slots/poles/phase and

Average airgap flux density of 0.6 T, following

overall machine dimensions are obtained;

Core Length of machine = 0.95 m

Rotor inner diameter = 0.95 m

Outer diameter of stator = 1.57 m

Efficiency of the machine = 0.96

Usually, the shaft diameter for 6 MW propeller is

0.9 m. This parameter matches with the rotor inner

diameter. The machine can accommodate 60 coils

for each power electronics module. An idea of

electric drive system using hydrogen fuel cell and

necessary storage has been proposed [2]. The

hydrogen reformer develops Hydrogen fuel cell

using off-shore renewables like Wind, Wave and

Solar power but the power handling capability of

this fuel cell system (100 kW) restricts the

application to the propulsion drives of several MW.

The detail drive scheme describing; how multiple

modular hydrogen fuel cell drives are integrated to

develop variable power is shown in fig. 6.

6 ECONOMIC CONSIDERATIONS

The economic advantages of hydrogen-based ship

propulsion remain uncertain at present, but may

become more apparent as hydrogen production and

consumption becomes widespread. The factors that

must be considered for an economic analysis of

hydrogen ship propulsion include:

− The weight, volume, and cost of shipboard hy-

drogen fuel storage compared to traditional stor-

age of fuel oil.

− The weight, volume, and cost of electric generat-

ing equipment and main propulsion motors com-

pared with traditional diesel or steam main pro-

pulsion machinery and associated ship’s service

generators.

− The cost of obtaining hydrogen fuel as compared

to obtaining hydrocarbon fuels that will satisfy

environmental requirements in the future, on an

energy-equivalence basis.

− The cost of periodic maintenance of hydrogen-

electric machinery compared to traditional marine

power plants.

This assumes that the availability and reliability

of hydrogen-electric machinery will be equivalent to

traditional plants. This is a fair assumption with

respect to the electrical machinery, but remains to be

proven for fuels cells and related equipment. Also,

one must assume that adequate supplies of hydrogen

will be available.

Given a twenty year life for a ship, an

incremental analysis of equivalent ships having

alternative propulsion modes would rely upon a net

present value expression such as:

NPV(∆Cost)=∆Cost

MACH

+ ∆ Cost

FUELSYS

+ (P|A,i%,20) [∆AnnCost

FUEL

+ ∆AnnCost

MAINT

] (6)

where the change in costs of machinery and fuel

systems are capital expenditures in the present, and

the sum of annual differences in the costs of fuel and

maintenance are reduced to a single present value by

the application of the Series Present Worth Factor

over the life of the ship at a cost of capital of i%.

For a cargo ship, the Minimum Required Freight

rate (MRFR) is often used as a figure of merit is

assessing a ship design. This is simply a ratio of the

annualized cost of the acquisition and operation of

the ship over the life of the ship, divided by the

annual tonnage of cargo carried (i.e., the ATC), and

the owner seeks to have a vessel with the minimal

MRFR to be more competitive. Assuming that the

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cargo carrying capacity of a hydrogen-powered

vessel is the same as a conventionally powered ship,

the change in Minimum required Freight rate would

(7)

A singular advantage that could accrue to a

hydrogen-powered vessel could be a reduction in

weight and volume of the machinery and fuel

storage, which would allow for additional cargo to

be carried in a ship of equivalent displacement.

7 CONCLUSIONS

Replacement of electric drive reduces volume and

weight of the ship and the available volume can be

utilized for the storage and reform systems. The

proposed modular drive scheme will give a

remarkable concept to overcome the challenges of

utilizing hydrogen fuel cell to the larger scale and in

future it can be extended to all other type of marine

applications.

REFERENCES

[1] Jennifer Guevin-Global shipping pollution ain‘t pretty

Green Tech. Feb.26, 2009

[2] John Vidal, Environment editor , guardian.co.uk

[3] Jerry Stanfield, “Moving Ahead” Yatch International ID

Magazine, Winter 2010, pp 22-28

[4] Greg Trauthwein, “Back to the Arctic” Marine Technology,

October 2009, pp 24-26.

[5] American Bureau of Shipping, ACTIVITIES, August 2010

[6] Yaqub M. Amani “Hydrogen Based Shipping

Industry”AG11 Presentation, Pusan South Korea Oct. 2010

[7] Yaqub M. Amani “A pioneering Hydrogen Fueled Ship”

[8] The Institute of Marine Engineers, All Electric Ship,

developing benefits for maritime applications, Conference

Proceedings, UK, 29-30, September 1998

[9] The First Global Conference on Innovation in Marine

Technology and the Future of Maritime Transportation

[10] Hackman, T. “Electric propulsion systems for ships” ABB

Review, No.3 pp. 3-12, 1992

[11] Parag R. Upadhyay and K. R. Rajagopal, “FE Analysis

and CAD of Radial-Flux Surface Mounted Permanent

Magnet Brushless DC Motors”, IEEE Transactions on

Magnetics Vol. 41, No. 10, October 2005, pp 3952-3954.

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