FIELD OF THE INVENTION
The present invention relates to a device for testing a single Membrane Electrode
cell and assembly of one of a polymer electrolyte membrane fuel cell and
phosphoric acid fuel cell. More particularly, the present invention relates, to a
device for testing Low and High Temperature Polymer Electrolyte Membrane Fuel
Cells (PEMFC) and Phosphoric Acid Fuel Cells.
BACKGROUND OF THE INVENTION
A fuel cell is an electrochemical device wherein a fuel gas reacts
electrochemically with an oxidant gas in the presence of a catalyst, producing
electricity. When operated with Hydrogen as fuel, and Oxygen / Air as oxidant,
the operation of an 'acidic' fuel cell, at the atomic level, causes stripping off
electrons from the 'hydrogen' at the catalyst sites at the Anode. The 'ionized
hydrogen', known as a proton, traveling to the Cathode through the 'electrolyte'
medium and recombining with 'oxygen' which is supplied to the Cathode and the
'electrons' which reach the Cathode through the external 'load' circuit, produces
'water vapour'.
Several different types of Fuel cells are known based on name of the 'electrolyte'
used in them, for example, Alkaline Fuel Cells (which use KOH, as an
electrolyte), Phosphoric Acid Fuel Cells, Polymer Electrolyte Membrane Fuel Cells,
also known as Proton Exchange Membrane Fuel cells or Solid Polymer Electrolyte
Fuel Cells.
In the case of PEMFC, H2 fuel, supplied to the Anode, sheds one electron and
becomes H+ ion. This H+ ion or 'proton' travels to the Cathode through the
'proton conducting membrane'. The electron (e), shed by H2 at the Anode, travel

through the external 'load' upto the Cathode, thus completing the electrical
circuit and recombine with the proton and Oxygen. The H+, O2 e- combine with
each other at cathode, to yield product 'Water'. Since the above process is
'exothermic' in nature, some heat is also produced. 'Water' and 'Heat', therefore,
are the only bi-products of a typical fuel cell reaction, making them one of the
cleanest, efficient and reliable power generating systems.
Fuel cells are being considered for various potential applications as portable
power units and for providing clean power in transport and telecommunication
applications. Stationary applications for powering homes, school buildings,
hospitals, hotels, office buildings, to name just few, are also becoming
increasingly viable.
The prior art teaches different testing devices for Membrane electrode assembly
of different types. Although such prior art is directed to preheating the stacks,
which however entail various drawback.
In a typical low temperature PEMFC a single cell which is also known as an MEA
(Membrane Electrode Assembly) consists of two electrodes (Anode and Cathode)
and a solid polymer electrolyte membrane interposed between the two
electrodes by hot compression moulding. The solid polymer electrolyte
membrane is a polymer ion exchange membrane (proton exchange membrane)
which conducts protons when the membrane is sufficiently hydrated. Humidifiers
are kept in between the flow path of reactant gases so that the reactant gases
are humidified prior to their entry to the reaction sites at the catalyst and
membrane interface. The humidified reactant gases exchange their humidity with
the solid polymer electrolyte membrane and at the same time react with the
catalyst to produce electricity. The humidification of the membrane plays a major
role on the performance of the cell. As explained above, a fuel cell reaction

produces electricity as well as heat and water vapour as by-products. In the fuel
cell, if the ion exchange membrane is used at high temperature, the ion
exchange membrane will get damaged. Therefore it is necessary to humidify the
membrane. At the same time, excess humidification of the membrane due to
humidified reactant gases as well as the water vapour produced as byproduct
after the reaction would lead to flooding of the cell, which in turn obstructs the
reactant gases flow path on the bipolar side. Hence, the optimum humidification
of the membrane is very critical in the low temperature PEMFC.
Further, a low temperature PEMFC requires a high purity Hydrogen. In the case
of High Temperature PEM Fuel Cells (HT PEMFC), whose operating temperature
is above 120°C, humidification subsystem can be discarded because Poly Benz
Imidazole (PBI) and Pyridine based polymer electrolytes retain ionic
conductivities even in the absence of membrane hydration. As the typical
operating temperature of an HT PEMFC is between 150 °C to 210 °C, these
power packs can be used in for Combined Heat and Power (CHP) mode in which
high grade heat is made available to the end user.
Moreover, the relatively higher temperatures of operation of the HT PEMFC, not
only enhances the electrochemical kinetics of Pt catalyst, it also improves
catalyst's tolerance to CO poisoning. It may be noted that as compared to the CO
tolerance of upto 10 ppm in the case of conventional PEMFCs, the HT PEMFCs
can tolerance upto 3% of CO (30000 ppm) in the fuel stream, making it possible
to integrate the HT PEMFCs with commercially available NG/LPG/Methanol
reformers.
Prior to the making of a multiple cell assembly or stacks it is necessary to
evaluate the performance of a single cell and optimize the different parameters
which would result in the performance enhancement of an MEA.

In the case of a low temperature PEMFC the reactant gases are required to be
humidified prior to their entry into the cell for effective reaction. If the cell
temperature at the inlet of reactant gases happens to be lower than the
temperature of humidified reactant gases, then the water vapour in the reactant
gases may get condensed and would lead to flooding of the gas flow channels in
the bipolar plates there by obstructing the free path of reactants.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for testing one of a
single cell (a membrane electrode assembly - MEA), which may be a low
temperature polymer electrolyte membrane fuel cell PEMFC or a high
temperature polymer electrolyte membrane fuel cell (HT PEMFC) or phosphoric
acid fuel cell (PAFC), which eliminates the disadvantages of prior art.
A further object of the invention is to propose a device for testing one of a single
cell (a membrane electrode assembly - MEA), which may be a low temperature
polymer electrolyte membrane fuel cell PEMFC or a high temperature polymer
electrolyte membrane fuel cell (HT PEMFC) or phosphoric acid fuel cell (PAFC),
which is adaptable to any single cell operating between 60 °C TO 210 °C.
SUMMARY OF THE INVENTION
According to the invention, the device comprises a pair of half bipolar plates with
flow field configuration for supplying reactant gases to respective electrodes, a
pair of current collectors, a pair of heating pad assembly capable of generating
cell temperature between 60°C to 210°C being externally connected through a
temperature controller to maintain said cell temperature, and a pair of end plates
with a plurality of tie rods and fasteners for the device assembly.

While the MEAs are made by hot pressing an Anode and a Cathode on either side
of a membrane, the Anode and Cathode, in turn are made up of electrode
support, diffusion layer, and catalyst layer. The half bipolar plates provide the
necessary and suitable flow paths to make the respective Veactant gases'
available at the Anode and the Cathode. While the electrodes are generally made
of porous layers, the half bi-polar plates are impervious, electrically conductive
and non-corrosive in nature. Apart from providing a flow field to the gas
distribution, the half bipolar plates also provides physical strength to the
membrane electrode assembly (MEA).
According to the invention, the device is enabled to test a low and a high
temperature single cell PEMFC and also a PAFC operating 60 °C to 210 °C. Each
one of the heating pad is further assembled in two metallic half plates, which are
thermally conductive in nature so that the heat generated by the heating pads is
transmitted to the single cell. A power source is connected to the heating pads
through a temperature controller to maintain the temperature between 60 °C to
210 °C for effective reaction to take place in the Membrane Electrode Assembly
(MEA). The Membrane Electrode Assembly (MEA) consists of an Anode, a
Cathode and a solid polymer electrolyte membrane which would be able to
withstand the working temperature of 60 °C to 80 °C in the case of a Low
Temperature Membrane Electrode Assembly (MEA) and between 120 °C to 210
°C for a High Temperature Membrane Electrode Assembly (MEA). The pair of
half bipolar plates may include entry and exit provisions along with various flow
channels for the reactants gases. The PEMFC single cell assembly (MEA) is kept
between two half bipolar plates followed by the two current collectors facing on
the outer surface of the half bipolar plates. A pair of heating pad assembly along
with insulator plates followed by the pressure plates arranged on either side of
the current collector plates and assembled together using proper fasteners to
make it a total assembly set-up for testing a "single cell PEMFC/ HTPEMFC/

PAFC". The pair of heating pad assembly is externally connected through a
temperature controller to maintain the temperature between 60 °C to 210 °C
based on the type of electrolyte being used in the cell. The reactant gases would
be connected to the respective inlet and outlet ports of the test set-up. The
advantage of the high temperature PEMFC is, humidification of reactant gases is
not necessary, hence the intermittent stage of installing the humidifiers at the
entry point of the reactant gases is eliminated thereby reducing the size of the
system to some extent. In a low temperature PEMFC, humidification of reactant
gases plays a key role in the performance of the MEA. Another major advantage
of the high temperature PEMFC is, it can tolerate upto 3% of CO (30000 ppm) in
the fuel stream, where as the low temperature PEMFC can tolerate only up to 10
ppm that is why a very high purity hydrogen gas only is required to be used as a
fuel in the case of low temperature PEMFC. Due to high CO tolerance level of
high temperature PEMFC, it is possible to integrate the HT PEMFCs with
commercially available NG/LPG/Methanol reformer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Exploded view of a conventional test device for low temperature
PEMFC single cell.
Figure 2 - Exploded view of a test device for single cell low temperature PEMFC,
high temperature PEMFC and also for single cell PAFC according to the invention.
Figure 3 - Showing the individual parts of Heating Pad assembly of the test
device of Figure - 2.
DETAILED DESCRIPTION OF THE INVENTION
As shown in figure - 1, the device comprises:

1A,1B : Top and Bottom pressure plates.
2A,2B : Top and Bottom Insulating plates
3A,3B : Top and Bottom Current collector plates.
4A,4B : Top and Bottom Half bipolar plates.
5 : MEA (Membrane Electrode Assembly).
6 : Tie Rods.
7 : Dummies.
8A,8B : Oxygen inlet and Outlet.
9A,9B : Hydrogen Inlet and Outlet.
A conventional low temperature PEMFC single cell test device have the pressure
plates 1A, IB followed by the insulating plates 2A, 2B and then by the current
collector plates 3A,3B. Adjacent to the current collector plates 3A, 3B, the half
bipolar plates 4A,4B are disposed. Between both the half bipolar plates 4A,4B an
MEA 5 (Membrane Electrode Assembly of low temperature PEMFC) is placed. All
the individual components are assembled together and compressed using tie
rods 6 and fasteners to form a single cell test device for testing a conventional
low temperature PEMFC MEA (Membrane Electrode Assembly). The reactant
gases are connected to the inlet headers 8A,9A and the exit gases pass out
through the outlet headers 8B,9B on the diagonal side of the inlet headers. The
opposite side of the inlet and outlet headers are closed with dummies 7.
As shown in figure - 2, the device comprises:
1A,1B: Top and Bottom pressure plates.
2A,2B : Top and Bottom Insulating plates
3A,3B : Top and Bottom Current collector plates.
4A,4B : Top and Bottom Half bipolar plates.
5 : MEA (Membrane Electrode Assembly).

6 : Tie Rods.
7 : Dummies.
8A,8B : Oxygen inlet and Outlet
9A,9B : Hydrogen Inlet and Outlet.
10 : Heating pad assembly
Thus, the inventive device includes all the components as shown in figure 1 and
in addition to that it has an additional component named as heating pad
assembly 10. The heating pad assembly 10 is placed on either side of the current
collector plates 3A,3B and connected to a power source through a temperature
controller to enable it to maintain the operating temperature of the single cell
between 60 °C to 210 °.
As shown in figure - 3, the heating pad assembly comprises:
10a : Top plate.
10 B : Bottom plate.
10 c : Heating Pad.
Fuel cells generate electricity from an electrochemical reaction in which oxygen
and hydrogen-rich fuel combined to form water. The advantages provided by
fuel cells often out-weight those of combustion technologies. Fuel cells offer
genuinely unique operational characteristic, such as low emissions, exceptional
efficiency and reliability, and are capable of offering combined heating, cooling
and power in certain applications. The value proposition represented by fuel cells
has been realised in the recent years in end-use applications as diverse as
auxiliary power units (APU) for campervans, as power back ups (UPS) for
telecom towers, stationary prime power for large industrial installations, micro
combined heat and power (micro-CHP) for homes, clean city buses and
automobiles, and in industrial applications as material handling vehicles.


In particular, thousands of PEMFC and DMFC auxiliary power units (APU) are
used in boats and campervans, with similarly large numbers of micro fuel cell
units being used in toys and educational kits. Demand from the military also saw
hundreds of PEMFC and DMFC power units put into service for infantry soldiers,
where they provide power to communications and surveillance equipment and
reduced the burden on the dismounted soldier of carrying heavy battery packs.
The need for reliable on-grid or off-grid stationary power in developing countries
also gave a boost to fuel cells. Hydrogen and natural gas fuelled PEMFC units are
used to provide primary or backup power to mobile phone masts. The rapidity of
mobile phone adoption in these regions means that the conventional grid
infrastructure cannot keep pace with new power demands, or is too unreliable
for an effective mobile network. Fuel cells provide a solution for this previously
unmet need.

A PEMFC or a PAFC consists of two electrodes anode, cathode and a polymer
electrolyte membrane (PEM), often called a proton exchange membrane in the
case of a PEMFC that permits only protons to pass between an anode and a
cathode electrodes of the fuel cell. At the anode, hydrogen (fuel) is reacted to
produce protons (H+) that pass through the PEM. The electron produced by this
reaction travel through a circuitry that is external to the fuel cell to form an
electrical current. At the cathode, oxygen is reduced and reacts with the protons
to form water. The anodic and cathodic reactions are described by the following
equations Anode
Cathode
In general, fuel cell power output is increased by increasing the cell operating
temperature (limited by the electrolyte used in the fuel cell), fuel and air flow to
the fuel cell in proportion to the stoichiometric ratios dictated by the equations
listed above. Thus, a controller of the fuel cell system may monitor the output
power of the stack and based on the monitored output power, estimate the fuel
and air flows required to satisfy the power demand. In this manner, the
controller regulates the required hydrogen flow, and in response to the controller
detecting a change in the output power, the controller estimates new flow rates
of fuel and air and controls them accordingly. In addition to this, critical
parameters like cell operating temperature would be maintained at constant
value irrespective of the external load changes to the fuel cell stack.
Conventional PEM fuel cell (low temperature PEMFC) operates at a relatively low
temperature, between and 80°C. This enables the fuel cell to
reach its operating temperature quickly. Despite, the advantage of quick start-
up, low temperature PEMFC requires hydration in the electrolyte membrane
(PEM) for ionic (H+) conduction, therefore requires an additional external or
internal subsystems for maintaining the required humidity levels in the fed

reactant gases. In addition to this, water formation on cathode side may lead to
flooding on the cathode side which is undesirable and limits the electrical load
applied to the stack.
The global PEM fuel cells working communities giving more importance for High
temperature proton electrolyte membrane (HTPEM) fuel cells because of its
operating temperature range (150 °C to 210 °C), this temperature range
facilities for improved CO tolerances up to 3% in hydrogen feed gas. Moreover,
this temperature regime can provide i) easy thermal management ii) zero water
management problem iii) use of humid free feed reactant gases and iv) overall
system simplicity. Considering the facts mentioned about the HTPEM fuel cells,
could be relatively cheaper because of less number of subsystems, easy of
integration with the commercial reformers and more efficiently when they are
being used in CHP applications.
Performance of HTPEM fuel cell is influenced by the ionic conductivity of the
membrane; commercial high temperature membranes available in the market for
HTPEM fuel cell applications are PBI and Pyridine based membranes doped with
Phosphoric acid, whose ionic conductivity varies from 0.08 S-cm to 0.12 S-cm. It
is essential to operate the HTPEM fuel cell/ stack above 100 °C to avoid the
formation of liquid water, due to which acid content of the membrane is leached
out and in turn results in degradation of ionic conductivity. Therefore, it is
essential to start the HTPEM fuel cell above 100 °C, in order to meet the
requirement of start-up temperature, HTPEM fuel cell have to be heated above
100 °C by various methods such as external preheating of the reactants before
they are fed into the anode and cathode inlets of the fuel cell stuck or cell
temperature is maintained by providing heaters in cell assembly itself.

In view of the advantages available in HTPEM fuel cells, more and more
concentrated work is being done in this area world vide. During the initial
developmental stage, it is very essential to evaluate the performance of single
cells and optimize the different parameters which would result in the
performance enhancement of an MEA prior to going for assembling multi
cells/stacks. The present invention relates to an assembly test set-up for
evaluating the performance of single cells/MEAs of low and high temperature
PEMFC and also for PAFC.
The half bipolar plates 4A, 4B shown in the figure 1 and 2 are a typical single
entry-single exit serpentine flow fields. However, the single cell test device is
designed in such a way that, it can cater to various types of flow field design like
single entry-single exit, multiple entry-single exit, multiple entry-multiple exit
etc...
The advantage of this new invention is, various types of flow fields like single
entry-single exit, multiple entry-single exit, multiple entry-multiple exit etc.... are
possible to utilise in this test device which makes it a unique design.
The inventive device is enabled to adapt various types of flow fields like single
entry-single exit, multiple entry-single exit, multiple entry-multiple exit etc... are
possible to utilise in this test device which makes it a unique device.
Heating pad assembly provides uniform heat distribution for the adjacent half
bipolar plates.

WE CLAIM
1. A device for testing a single cell (a membrane electrode assembly - MEA),
which may be a low temperature polymer electrolyte membrane fuel cell
PEMFC or a high temperature polymer electrolyte membrane fuel cell (HT
PEMFC) or phosphoric acid fuel cell (PAFC), the MEA (5) being disposed
and securely held on the device during testing, the device comprising:
- a top and a bottom pressure plate (1A,1B);
- one each top and bottom insulating plates (2A,2B);
- one each top and bottom collector plates (3A,3B);
- one each half bipolar plates (4A,4B);
wherein the top plates (1A,2A,3A), the bottom plates (1B,2B,3B), the
collector plates (3A,3B), and the half bipolar plates (4A,4B) are sub-
assembled together by fastening means;
characterized in that the pair of heating pad assembly (4A,4B) having
flow field capable of supplying reactant gases to the MEA (5), and in
that one each heating pad (10) configured to generate cell
temperature between 60 °C to 210 °C is disposed in a spaced-apart
manner to cover the MEA (5) being connected through a temperature
controller.
2. The device as claimed in claim 1, wherein the fastening means comprises
a plurality of tie rods (6) which further connect the sub-assembly with the
heating pad assembly (10).

3. The device as claimed in claim 1, wherein the heating pad assembly
comprises a top plate (10a), a bottom plate (10b), and a heating pad
(10c).
4. The device as claimed in claim 1, comprising inlet headers (8A,9A) and
outlet headers (8B,9B) to allow passage of reactant gas.

ABSTRACT

The invention relates to a device for testing a single cell (a membrane electrode
assembly - MEA), which may be a low temperature polymer electrolyte
membrane fuel cell PEMFC or a high temperature polymer electrolyte membrane
fuel cell (HT PEMFC) or phosphoric acid fuel cell (PAFC), the MEA (5) being
disposed and securely held on the device during testing, the device comprising: a
top and a bottom pressure plate (1A,1B); one each top and bottom insulating
plates (2A,2B); one each top and bottom collector plates (3A,3B); one each half
bipolar plates (4A,4B); wherein the top plates (1A,2A,3A), the bottom plates
(1B,2B,3B), the collector plates (3A,3B), and the half bipolar plates (4A,4B) are
sub-assembled together by fastening means; the pair of heating pad assembly
(4A,4B) having flow field capable of supplying reactant gases to the MEA (5),
and in that one each heating pad (10) configured to generate cell temperature
between 60 °C to 210 °C is disposed in a spaced-apart manner to cover the MEA
(5) being connected through a temperature controller.