International Journal of Engineering Trends and Technology (IJETT) – Volume 22 Number 9-April 2015
Modelling and Simulation of Proton Exchange Membrane Fuel Cell
Ketan R. Patel#1, Vipul K. Patel *2, Darshan R Vora#3
1
2
Post-Graduation, M.Tech, CGPIT, Bardoli, Surat
Post-Graduation, M.Tech, CGPIT, Bardoli, Surat
3
Assistant Professor, CGPIT, Bardoli, Surat
Abstract — This paper presents the simulation of PEM fuel cell
using electrical circuits. PEM fuel cell is considered to be a
Promising Power source and application due to its highefficiency; low temperature and fast start up. To meet the
demand for power sources it is constructive to combine the fuel
cell with energy storage system. The system design and
performance analysis could be achieved through simulation prior
to practical realization.
Cathode:
Overall:
+
+ Heat + Electricity
Keywords —Dynamic Model, PEM Fuel cell, Distribution
system
I. INTRODUCTION
Distributed generation represents a small-scale electric
power source connected directly to the utility’s distribution
network, and provides electric power at a site closer to the
customers. It is a collection of energy from many sources and
gives lower environmental impact and improved security of
supply. PEM fuel cells have the advantage that they can place
at any site in a distribution system, without geographic
limitation. PEM fuel cells are good energy sources to provide
reliable power, but they can’t respond to electrical load
transients as fast as desired. fuel cell are electrochemical
devices which consist of electrolyte an ion a solid in contact
with two electrodes which directly convert chemical energy of
fuel into electrical energy.
PEM fuel cells have great performance for use as
distributed generation sources. there are different types of fuel
cell like solid oxide fuel cell(SOFC), proton exchange
membrane fuel cell (PEMFC), alkaline fuel cell(AFC), molten
carbonate fuel cell(MCFC), direct methanol fuel cell(DMFC)
are the most impressive used for a distributed generation
purpose.
Fig. 1 Basic operation of PEMFC
Fig 1 shows the basic operation of PEM fuel cell. The
basic behaviour of fuel cell is generally depending on cell
temperature, reactant partial pressure and current density. The
best performances of a PEM fuel cell at temperature around
70-80˚C.the electrochemical model of PEM fuel cell have
some assumptions are follows as:
Fuel cell temperature is stable.
Nerst equation is applied.
The Gases are ideal.
Fuel cell is fed with Hydrogen and air.
The ratio of pressure between the inside and outside of
the electrode channel is large enough to assume
chocked flow.
II. BASICS OF PEM FUEL CELL
The basic structure of a PEM fuel cell has two electrodes
which is separated by a one solid membrane electrolyte. We
are feeding hydrogen from a anode side and oxygen from
cathode side. we are using a catalyst which has two
functions:1)By the use of catalyst hydrogen molecules broken
into electrons and protons at the anode. When hydrogen
proton pass through membrane to reach the cathode surface or
we can say electron s flowing from anode to cathode and
combine with each other provide a power to the load as well
as produce water. In given fig below a catalyst is used to
increase the reaction process without consuming and taking
part in process. The reaction process is as given below:
Anode:
ISSN: 2231-5381
Fig. 2 V-I Characteristics
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International Journal of Engineering Trends and Technology (IJETT) – Volume 22 Number 9-April 2015
Fig 2 shows the V-I Characteristic of PEM fuel cell which
operate in three potential region.in PEM fuel cell the voltage
across the cell is related with low current and it is due to
activation loss inside cell; output voltage at the end of the
curve will drop sharply as the load current increases.
III. MODELLING OF FUEL CELL
Where,
is the voltage drop affected only by
the fuel-cell internal temperature, while is both current and
temperature dependent. While
T*b*
) is both
current and temperature dependant. The equivalent resistance
of activation corresponding to is defined as:
……...……………….. (8)
To calculate the fuel cell output voltage, the effective
partial pressures of
and
need to be determined.
B. Ohmic Voltage Drop
… (1)
………………... (2)
The cell potential voltage (Vcell), at any instance could be
found using Eq. (1). When a cell delivers power to the load,
the no-load voltage (E), is reduced the voltage drop, namely,
the activation (Vact), ohmic (Vohm), and concentration (Vconc)
over voltages.
V………… (3)
Eq. (3) is called a Nerst Equation which gives output
voltage of a cell. The Nerst equation (Eq. (3)) gives the open
circuit cell potential (E) as a function of cell temperature (T)
and the reactant partial pressures [6].
The ohmic resistance of a PEM fuel cell consists of the
resistance of polymer membrane, the con-ducting resistance
between the membrane and electrodes, and the resistances of
electrodes. The overall ohmic voltage drop can be expressed
as
………………………………. (9)
…… (10)
C. Concentration Voltage Drop
During the reaction process, concentration gradients can be
formed due to mass diffusions from the flow channels to the
reaction sites. At high current densities, slow transportation of
reactants (products) to (from) the reaction sites is the main
reason for the concentration voltage drop. Any water film
covering the catalyst surfaces at the anode and cathode can be
another contributor to this voltage drop. The concentration
over potential in the fuel cell is defined as:
.. (4)
To calculate the fuel-cell output voltage, the following
estimations and equations are used:
A. Activation Voltage Drop
Tafel equation (5) is used to calculate the activation voltage
drop in a fuel cell.
…..……..….……………… (5)
……….……………….……… (6)
On the other hand, an equation for
a constant is added to as follows:
is given in , where
+ (T298)*a +*b*
=
....................………………………… (7)
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…….…….……….. (11)
Where, is the surface concentration and
is the bulk
con-centration. According to Faraday’s Law, the above
equation can be rewritten:
)………………….. (12)
The Equivalent resistance for the concentration loss is:
=
)…… (13)
D. Double-Layer Charging Effect
In a PEM fuel cell, the two electrodes are separated by a
solid membrane which only allows the
ions to pass, but
blocks the electron flow. The electron will flow from anode
through external load and gather at the surface of the cathode,
to which the protons of hydrogen will be attracted at the same
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time. Thus, two charge layers of opposite polarity are formed
across the boundary between the porous cathode and
membrane. The layers, can store electrical energy and behave
like a super capacitor.
TABLE I
FUEL CELL MODEL PARAMETER
Symbol
Ea
Parameter
Reference
Value
1.229 V
Potential
R
Universal Gas
8314
Constant
J/Mol*K
F
Faraday Constant
96485 C/Mol
T
Stack Temperature
353 K
Panode
Anode pressure
1.5 Atm
Pcathode
Cathode Pressure
1 Atm
N
No. Of Cells
48
_____
Capacity
500Watt
Operating
Operating
temperature
temperature
Fig. 4 Simulation Results
5˚C to 35˚C
IV. SIMULATION & RESULTS
Fig. 5 Result of V-I Characteristics without load using X-Y scope
Fig. 6 Result of P-I characteristics without load using X-Y scope
Fig. 3 Simulation of PEM fuel cell with load
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V. CONCLUSION
This paper presents the Dynamic model development for
PEM fuel cell in Matlab / Simulink environments. The
electrical circuit elements and their properties are used in the
modeling and simulation time for this model without load
490sec and with load 1sec. Validation of the models has been
carried out through experiments on a 500-W PEM fuel cell
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International Journal of Engineering Trends and Technology (IJETT) – Volume 22 Number 9-April 2015
IEEE, and Steven R .Shaw, Member, IEEE.” Dynamic Model and Validation for
stack at No load and while connecting Load the results are
shown.
[6]
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