FIELD OF THE INVENTION
The present invention generally relates to proton exchange membrane fuel cells
(PEMFC) and high temperature polymer electrolyte membrane fuel cells
(HTPEMFC) which convert chemical energy directly into electrical energy. More
particularly, the present invention relates to an improved fuel cell stack assembly
system operably connected to an internal gas preheating device to improve
performance of proton exchange membrane fuel cells and high temperature
polymer electrolyte membrane fuel cells.
BACKGROUND OF THE INVENTION
Fuel cell an electrochemical device that converts chemical energy directly into
electrical energy. One type of such fuel cell is proton exchange membrane fuel
cell (PEMFC). It consists of two electrodes anode, cathode and a polymer
electrolyte membrane (PEM), often called a proton exchange membrane 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 electrons produced by this reaction travel through
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
anode and cathode reactions are described by the following equations
Anode H2--------- 2H+ + 2e
Cathode O2 + 4H+ + 4e--------- 2H2O

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 then 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 60°C and 80°C. In practice, cooling load required for
maintaining such low temperature of stack draws more energy than to maintain
a high temperature for the same electrical output. Apart from containing a Fuel
Cell stack, a conventional PEMFC power pack would also contain the following
sub systems for i) Air supply; ii) Fuel supply; iii) humidification iv) stack cooling
v) power conditioning & vi) controls. In addition to this, low temperature PEM
fuel cells require pure hydrogen, in terms of CO content (CO<10 ppm) present in
the reactant feed gas. Considering the afore said facts and to meet the
requirements of fuel cell operating conditions, subsystems like humidification,
cooling and air supply subsystems are indispensable in addition to the PEM fuel
cell stack.

In 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 &. 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 uptd 10
ppm in the case of conventional PEMFCs, the HT PEMFCs can tolerate upto 3%
of CO (30000 ppm) in the fuel (Hydrogen) stream, making it possible to integrate
the HT PEMFCs with commercially available compressed natural gas (CNG),
Methanol, ethanol, Liquefied petroleum as (LPG) and Diesel reformers etc.
High temperature proton electrolyte exchange membrane (HTPEM) fuel cells are
widely used because of its operating temperature range (150°C to 210°C), which
contributes improved CO tolerances up to 3% in hydrogen feed gas. Moreover,
this temperature range provides i) easy thermal management, ii) eliminates zero
water management problems iii) allows use of humid free feed reactant gases
and iv) simplifies overall system operability. Apart from the advantages as stated
hereinabove, the HTPEM fuel cell systems are relatively cheaper because of
having less number of subsystems. Further, HTPEM cells are easily integratable
with the commercial reformers and more efficient when used in CHP applications.
Typical operating temperature of the HTPEM fuel cell/stack is above 100°C to
avoid the formation of liquid water, due to which acid content of the membrane
is leached out which leads to degradation of electrolyte ionic conductivity.

Therefore, it is essential to start the HTPEM fuel cell above 100°C, in order to
meet the requirement of startup temperature. HTPEM fuel cell is heated above
100°C by various methods i) external preheating of the reactants before they
are fed into the anode and cathode inlets of the fuel cell stack ii) continuous
circulation of the hot fluid through the stack cooling passages until the stack
reaches a specified startup temperature iii) circulation of the fuel burner exhaust
gases through the stack coolant passages and iv) circulation of catalytic
combustor exhaust gases through the stack coolant channels depends on the
fuel used in catalytic combustor.
As described hereinabove, HTPEM fuel cells are required to be operated at above
120°C (startup temperature). In practice, a control system ensures that the
electrical load is ON once the fuel cell temperature reaches its startup
temperature. Stack startup temperature can be achieved using either of the
methods as mentioned above. Stack temperature increases soon after the stack
external electrical load is ON, due to exothermic reaction of water formation on
cathode side. Once the stack is subjected to an external electrical load, a
continuous rise in stack temperature takes place. In order to obtain optimal stack
performance, stack temperature is controlled at specified value between 160°C
and 210°C depending on the electrolyte used in the fuel cell. Typically, the stack
temperature is controlled either using radiator fans by which ambient air is
circulated through the cooling channels or by continuous circulation of high
boiling temperature liquid through the cooling channels. In case of liquid
circulation method, stack hot exit coolant fluid is cooled further with the
assistance of external radiators provided or the heat is recovered for various
applications.

It is known that performance of any fuel combustion process depends on the
temperature of fuel and oxidants fed and oxidants fed into the combustion
chamber. In order to meet the requirement of specified temperatures of fuel and
oxidant (air), preheating systems are used. Performance of either PEM/HTPEM
fuel cell further depends on inlet temperatures of the reactants. Therefore, the
reactants are heated either with externally or internal heat source to a specified
temperature to obtain better fuel cell performance. In case of external heating
process, an external heat exchanger is used, wherein the reactants are typically
heated by utilizing the available stack heat carried away by the coolant or by the
heat released from a catalytic combustor placed after the fuel cell stack to
ensure clean emissions. Accordingly, the hydrogen exited by uncoverted anode,
and air exited by cathode side are fed into the catalytic combustion chamber
followed by mixing where they react each other and produces heat. In case of
internal reactants preheating process, the reactants are heated within the stack
assembly without using any external heat exchanger. In this regard, significant
numbers of patents have been filed on utilization of heat generated during the
operation HTPEM fuel cells, in particular the stack heat is used for preheating
liquid fuel before it is fed into fuel processor for hydrogen generation.
US patent No. 20050014040 to Ian W. Kaye utilized the heat generated in the
stack for preheating the reformer liquid fuel (methanol/Ethanol/Ethanol) in
efficient way in view of increasing the fuel cell system efficiency. In this case,
liquid fuel is preheated in a heat exchanger by utilizing the hot air which is being
heated in the fuel cell stack housing. The exhaust air from the heat exchanger is
finally fed into the fuel burner for maintaining the catalytic reformer
temperature. In this case air required for burner is passed over the appended
heat transfer plate, on the other hand, cathode air is fed with separate air blower
through a separate air line.

US patent No. 20060099467 to Richard H. Cutright et al. developed an integrat
ed high temperature PEM fuel cell system. An overall fuel cell system comprises,
a High temperature fuel cell stack for generating electricity, air supply system for
supplying the oxidant to cathode, auto thermal reformer system for supplying
hydrogen rich gas to anode side, cooling system for maintaining the temperature
of subsystem and control system for ensuring the specific operating conditions of
the individual subsystems. In their invention, the cathode side receives ambient
air directly through the blower and reacts on cathode side of PEM fuel cell. The
exhaust of cathode side air is in communication with the auto thermal reformer,
where partial amount of exhaust cathode air is fed into the reformer inlet
section. The exhaust of reformer, hydrogen rich gas is in fluid communication
with the anode inlet of HTPEM fuel cell stack. The exhaust of stack anode,
hydrogen lean gas is fed to the oxidizer along with the partial amount of cathode
side exit gas where the unconverted hydrogen is oxidized in the catalytic
converter (oxidizer) and then the exhaust of oxidizer is vented to atmosphere. In
their invention, the exhaust hot air from the HTPEM fuel cell stack is directly fed
into the oxidizer and auto thermal reformer by which they have improved the
system overall efficiency.
US patent 20020160239, PEM fuel cell system is integrated with a fuel processor
and an exhaust gas oxidizer to ensure clean emissions. In their study HTPEM fuel
cell is used with an operation temperature of 120-200°C. Cathode exhaust of fuel
cell is used to provide steam and oxygen to a reformer to convert a hydrocarbon
fuel to hydrogen, wherein the hydrogen is provided to a fuel cell. In addition to
this partial amount of cathode exhaust is fed into the oxidizer along with anode
side exhaust gases to result in clean emissions.

US patent 20056,899,062 fuel cell stack is cooled by ambient air using a blower,
exhaust hot air from the blower is directly fed into the cathode inlet as a result
cathode side hot feed supply is achieved. US patent 20060099467, fuel cell stack
having a cathode inlet to receive a flow of ambient air and a cathode outlet to
provide a cathode flow; and a fuel processing reactor having an inlet and an
outlet, the inlet and outlet being in fluid communication with a catalyst suitable
for converting a hydrocarbon into a gas containing into a gas containing
hydrogen and carbon monoxide, the outlet being in fluid communication with an
anode chamber of the fuel cell and the outlet of the reactor being in fluid
communication with the cathode outlet for combustion of exhaust gases.
US patent 2107666539B2, by Jennifer E Branley et al. In their invention,
unconverted or exhaust gases of burner are passed over heat transfer
appendages which are thermally in contact with the stack bipolar plates finally
the burner exhaust gasses passes through catalytic combustor which is intact
with the stack externally, the outlet gases of the catalytic combustor are
thermally in contact with stack using a heat pipe. In which the appendages are
thermal bridging pieces between a thermal catalytic combustion and bipolar
plates. In more details, part of the appendages is coated with a thermal catalyst
by which the temperature of the circulating gas will be increased further to heat
the stack. In all their invention, heat is recovered efficiently external to the stack.
In addition to this, cathode exhaust is used for preheating the methanol fuel
which fed into reformer for generation of hydrogen.
US Patent 20100297516 Al, by S K Das et al. wherein anode gas flow is opposite
to membrane face and the other side of the anode plate is left blank, the other
plate whose gas flow for cathode side is opposite to other side of membrane face
and the other side of cathode plate is allowed for cooling circulation whose

channels are perpendicular to the cathode gas flow channels. The key
components in HTPEM fuel cell stack assembly are membrane electrode
assembly cathode plate anode plate, blank plates and seals are assembled co-
axially in a sequence of end plate, current collector plate, blank plate, anode
plate and cathode plate having cooling channels followed by other side end plate
and intermittent seals between plates of anode and cathode. In their stack
assembly there is no provision given for internal preheating of gases.
A prior art of PEM/HTPEM fuel cell (single) comprises three basic components
such as electrolyte, anode and cathode. Electrolyte is used for ionic conduction
between two electrodes (anodes and cathode). Oxidation of hydrogen takes
place at anode over catalyst to give protons and electrons; the electrons are
transferred to the external circuit through electrical conduction medium and
protons are conducted to another side (cathode) through ionic conducting
medium (proton electrolyte membrane). At cathode, reduction reaction between
hydrogen ions, electrons and oxygen takes place in presence of catalyst to form
water, as a result of the exothermic reaction significant amount of heat would be
released. In order to form a complete single cell, the membrane is hot pressed
between two electrodes to form a membrane electrode assembly (MFA). Further,
the MEA is placed between two copper plates followed by gas flow field plates on
each side of MFA; finally the whole assembly is tightened between two end
plates to form complete single PEM fuel cell. The fuel cell has a terminal voltage
of up to one volt DC. For purposes of producing much larger voltages, several
fuel cells are electrically connected in series and assembled together between
the end plates to form an arrangement called a fuel cell stack.

In case of conventional PEM fuel cells whose operating temperature is below
80°C requires humidification for the feed reactant gases and it is possible to start
cell/stack at room temperature itself. The humidification of gases is carried either
external to the stack or internal method. Where as in high temperature PEM fuel
cells, no humidification required for feed reactant gases, besides this prerequisite
startup temperature above 120°C is of critical importance. In order to maintain
this prerequisite temperature of HTPEM fuel cell/stack is heated by feeding the
hot gases which were heated externally or heating the stack by providing heating
plates at the ends of intermittent positions across the stack.
Various preheating methods discussed above would increase subsystems by
providing external system for preheating the gases or preheating the stack by
providing heating plates would result in non-uniform heating of cells across the
stack. In view of the above the present method of heating would results in near
uniform cell temperatures because of uniform supply of gases to each cell
without adding any additional subsystem to fuel cell stack just by adding two
plates at ends of stack assembly.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved fuel cell stack
system assembly operably connected to an internal gas preheating device to
improve performance of proton exchange membrane fuel cells and high
temperature polymer electrolyte membrane fuel cells.

Another object of the invention is to propose an improved fuel cell stack system
operably connected to an internal gas preheating device to improve performance
of proton exchange membrane fuel cells and high temperature polymer
electrolyte membrane fuel cells, which allows utilization of the cathode exhaust
heat for preheating the reactant gases of anode and cathode after the stack is
attained its startup temperature.
A still another object of the invention is to propose an improved fuel cell stack
system operably connected to an internal gas preheating device to improve
performance of proton exchange membrane fuel cells and high temperature
polymer electrolyte membrane fuel cells, which ensures that the inlet gas
entered at the cathode inlet is heated above 120°C prior to entry into the
cathode inlet manifold.
Yet another object of the invention is to propose an improved fuel cell stack
system operably connected to an internal gas preheating device to improve
performance of proton exchange membrane fuel cells and high temperature
polymer electrolyte membrane fuel cells, which allows heating of the inlet gas
into the anode inlet manifold above 120°C.
A further object of the invention is to propose an improved fuel cell stack
assembly system operably connected to an internal gas preheating device to
improve performance of proton exchange membrane fuel cells and high
temperature polymer electrolyte membrane fuel cells, which allows utilization of
the cathode hot exhaust gas as a heating source for heating the anode and gas
preheating plate device.

A still further object of the invention to propose an improved fuel cell stack
system operably connected to an internal gas preheating device to improve
performance of proton exchange membrane fuel cells and high temperature
polymer electrolyte membrane fuel cells, which enables the heat source for
heating the HTPEM fuel cell stack to meet the stack startup temperature using
gas preheating plate device.
Yet further object of the invention is to propose an improved fuel cell stack
assembly system operably connected to an internal gas preheating device to
improve performance of proton exchange membrane fuel cells and high
temperature polymer electrolyte membrane fuel cells, which is provided with an
assembly of pressure or temperature sensor to monitor the pressure drops of
reactant flow fields and exit gas temperature after preheating plates at anode
and cathode sides respectively.
SUMMARY OF THE INVENTION
Mechanism of reactant gases preheating in PEM/HTPEM fuel cells is disclosed in
Indian Patent Application No 204/KOL/2012 titled "Method of preheating of
reactants in Low/High temperature proton exchange membrane (PEM) fuel cell
stack using an integrated plate". The present invention provides an improved
fuel cell stack system operably connected to an internal gas preheating device to
improve performance of proton exchange membrane fuel cells and high
temperature polymer electrolyte membrane fuel cells. The system basically
constitutes a fuel cell stack incorporated an improved device having gaskets and
a heating means for preheating of the reactant gases such as Hydrogen and Air
within the stack assembly (internal gas preheating) before they are fed into

electrochemical active zone of anode and cathode sides respectively in low
temperature/high temperature PEM fuel cells. The system comprises two
additional plates placed between the insulation plate and current collector plate
at two ends of the stack end plates, wherein special type gaskets are disposed in
between these plates. The device plate is provided with at least two numbers of
window type gaskets to provide uniform load distribution during compression
and low pressure drop of the gas flow. In addition, an independent electrical
heating source is provided on each plate for which the power is supplied
externally either from a battery or AC supply source to maintain the stack at
required temperature to allow an instant startup of the fuel cell stack. A plurality
of through passages is provided for fluid flow circulation through the gas
preheating device which can be used for efficient utilization of cathode side
exhaust heat carried by the cathode side exit air. Also, the present system has a
provision to monitor the PEM/HTPEM stack back pressure inside the stack
without disturbing the fluid stream of the inside reactant gas manifold of stack.
The system is further provided with means to monitor and control temperature
of the reactant feed gas prior to inputting into the reactant manifold of the stack.
The gas preheating plate receives the reactant gas through the regular stack
inlet and then the gas is circulated around the heating source where the gas is
being heated then the hot reactant gas exits from the heating plate and enters
into the electrochemical active zones of stack anode and cathode sides
respectively complete mechanism known from Applicants Admitted prior
Art.(AAPA).
It is known from the AAPA that the fuel cell reactant gases are pre-heated to a
required temperature before they are fed into the electrochemical active sides of
the fuel stack anode and cathode respectively. The reactants preheating device

of the inventive system can be adapted for conventional, HTPEM and internal
reformed HTPEM fuel cells. Preheating plate is configured such that it can easily
be accommodated within a conventional stack assembly sequence without the
need of change in the regular inlets and outlets of cathode and anode
respectively. Typically a PEM/HTPEM fuel cell assembly follows the sequence of
placing a top pressure plate, an insulation plate, a copper plate (anode), an
anode half-bipolar plat e membrane electrode assembly (MEA), a bipolar plate, a
MEA, a bipolar plate, and a repetitive sequence of MEA followed by bipolar plate,
cathode half-bipolar plate, cqpper plate (cathode), insulation plate and bottom
pressure plate. All the afore said components are tied together for a required'
torque applied over the top and bottom pressure plates using tie rods to form a
PEM cell stack.
According to the invention, the reactants gas preheating device of the system
consists of two metal plates in addition to the conventional stack assembly
components. The additional components are anode side reactant preheating
plate which is placed between the insulation plate and anode side copper plate
with said special gaskets. On the other hand, the cathode side reactant
preheating plate is placed in between the cathode copper plate and insulation
plate. These preheating plates are provided with an electrical heating source
including a temperature controller to maintain a temperature set point, and for
circulating the hot fluid by which the plate is initially heated to the set point
temperature by the electrical source. Typically the reactants are fed to the
regular stack inlet and the inlet of preheating plate is directly in fluid
communication with the regular stack inlet. The system is configured such that
reactant gases after heating are redirected to its regular inlet gas manifold as in
conventional PEM fuel cell stacks. In addition, the stack system is provided with

a monitoring device to measure actual pressure/temperature of the reactant
gases after they are heated and prior to entry into the electrochemical reaction
zone of the anode or cathode respectively. A plurality of sensors are mounted at
dead ends of the respective inlets to avoid disturbance of the actual gas stream
lines of the anode or cathode reactant gases. Finally, all the components of
HTPEM fuel cell stack are assembled with one each external and internal tie rods.
Theses external tie rods are metal based having no electrical insulation and the
internal tie rods are encapsulated with an electrically insulated material.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Conventional PEM fuel cell stack assembly
Figure 1.1 - Bipolar plate two sides gas flow grooves
Figure 1.2 Half bipolar plate with cooling grooves
Figure 2. PEM fuel cell stack system with integrated reactant preheating plates
Figure 3. Gas preheating plate device
DESCTIPTION OF THE PREFERRED EMBODIMENTS
A prior art PEM fuel cell stack is shown in figure 1, the stack comprises two end
plates (1A, 1B) between which the balance components of the HTPEM fuel stack
are tightened using tie rods (7A,7B). The components of PEMFC stack includes
insulating plates (2A,2B) to protect against thermal and electrical looses, cooper
plates (3A,3B) for collecting the electrons generated at the electrocatalyst sites
of t he membrane electrode assemblies (5) through half bipolar plates (one side
groove and other side blank) of anode (4A) and cathode (4B) respectively. An
half bipolar plate (4A or 4B) having a serpentine flow pattern (4B) can be seen in

the bottom half section. In addition to this, number bipolar plates (6) having
both the side gas flow grooves as shown figure 1.1 are used in the stack
assembly, these plates have gas flow grooves on both sides, one side is used for
anode gas circulation and the other side is used for cathode gas circulation. The
assembly also consists number of half bipolar plates, one side consists of gas
" grooves (6A) and is for routing the reactant gas from manifold (8A and 9A) and
the second side (6B) consists of parallel grooves to allow the coolant circulation
(19). One such plate is shown in Figure 1.2, two such half bipolar plates (6A,6B)
are laminated together to form bipolar plate having inner gas cooling grooves
and appears like conventional bipolar plate (6).
The bipolar plate as shown in figure (1.1) is designed such that one side of the
gas distribution pattern is for receiving the air/oxygen from a bulk oxygen/air
manifold (8A) and routing to a bulk exit air/oxygen manifold (8B) represented
with up and down arrows respectively. In a stack, the oxygen/air gas manifolds
(8A,8B) are directly in fluid communication with their stack inlet (14) and outlet
(15) respectively. In case of anode, the second side of the bipolar plate (6) has
the gas distribution pattern for receiving and Hydrogen from a bulk inlet manifold
(9A) and routing to a bulk exit (9B) represented with down and up arrows
respectively. In a stack, the Hydrogen manifolds (9A,9B) are directly in fluid
communication with their stack inlet (16) and outlet (17) respectively.
Conventional PEM fuel cells operate below 80°C and require hydration for the
membrane ionic conduction. One such method for maintaining the hydration of
the membrane is by feeding the humidified reactants into the fuel cell stack. In
practice, humidification of the reactants is achieved by external (out side the
stack assembly) methods. In practice, there might be of vapor condensation
between the iines of humidification and reactant inlets of the stack, which may

lead to local condensation of water vapor at the electrocatalyst layer resulting in
adverse effect of drop in cell voltage. In order to overcome this problem,
reactants of either anode side or cathode side gas lines are provided with the
heating arrangement external to the stack. The heating source could be an
electrical or a cathode side exhausts gas.
In principle, the chemistry involved in LTPEM fuel cells and High Temperature
PEM Fuel Cells (HT PEMFC) are same except their operating temperature and
properties of the membrane. HTPEMFC operating temperature is above 120°C,
ionic (H+) conduction of membranes like Poly Benz Imidazole (PBI) and Pyridine
based polymer electrolytes retain their conductivities even in the absence of
membrane hydration. Since these membranes are doped with phosphoric acid
for better ionic conductivity, they become sensitive for the acid leaching in
presence of liquid water. Therefore, the HTPEMFC stack has to be started above
100°C to avoid degradation of the membrane ionic conduction. As the typical
operating temperature of an HT PEMFC is between 150°C to 210°C, the reactants
have to be heated to a prerequisite temperature preferably above 120°C. In
practice, HTPEMFC startup temperature is reached by circulating the hot gases
through the cooling channels. Once the stack is attained its startup temperature,
reactants preferably preheated hydrogen/reformer hydrogen and air are fed into
the anode and cathode inlets of the stack respectively. Now the electrical load is
allowed to turn ON once the stack temperature reaches the startup temperature.
In case of HTPEMFC stack, hot hydrogen and air have to be fed into stack to
obtain better stack performance which is analogues to the conventional air-fuel
mixture preheating in combustion chamber for delivering better performance. In
this regard, many of the prior art use reformer final outlet hydrogen directly fed
at the anode side inlet, on other hand, hot air from the air cooled stack exhaust

is directly used at the cathode inlet using blower. In some cases, the stack is
heated using flexible heating tapes wrapped around the stack. Present invention
is pertaining with the assembly of complete stack which includes integrated gas
preheating device having two additional components used for preheating the
anode and cathode gases prior to feed them into anode side and cathode side
gas distribution plates receives hydrogen and air respectively. In this case, the
reactants are heated within the fuel cell stack assembly. In contrast to the
conventional PEM/HTPEM fuel cell as shown in figure 1, an integrated
PEM/HTPEM fuel cell stack is shown in figure 2 and comprises two additional
plates (8,9) in addition to the conventional PEM fuel cell components which are
placed adjacent to cathode side copper plate (3A) and anode side copper plate
(3B) respectively with special gaskets (11) to avoid gas leakage also to provide
uniform load distribution while compression and low pressure drop for gas flow.
The detailed schematic of a preheating plate (15,16) is shown in figure 3. It
consists of common through holes (1,2) for tightening the stack and for routing
the reactants to their respective manifolds. In addition to this, the preheating
plate consists of two semi drilled holes (3A,3B) opposite to each other separated
with a solid barrier. In this case these, two holes are inline with the conventional
reactant (air or hydrogen) inlet and its manifold used for receiving and
distributing the concerned reactant to the individual cells of anode or cathode
respectively. One side of the semi drilled hole receives the hydrogen or air from
the hydrogen or air inlet and it is allowed to reach the other side of the semi
drilled whole for hydrogen or air outlet through direct slot (6) provided for direct
fluid communication between top and bottom faces of preheating plate. In
addition to this, integrated preheating plate is provided with long through holes
(4), few of these holes are to be used for heating the plate by means of inserting

an electrical heaters (5) in holes (4) or to circulate the burner exit gases and the
remaining holes (4) would be used for heat recovery to collect the heat from the
exhaust cathode gases with the assembly arrangement made (10,11). Heat
recovery from cathodes exhaust gases connected to t he inlet side assembly (10)
can be achieved by allowing the cathode exit gases pass through the holes (4)
via the assembly made (10 or 11). It is explained in figure 2 by providing direct
fluid communication between top preheating plate (8) and top cathode exit (18)
providing suitable piping (15A), similarly providing a piping (15B) at the bottom
section to provide cathode exhaust fluid communication between cathode bottom
exit (15) and cathode preheating plate (9). Through this process of assembly
provided for cathode exhaust gases circulation, the preheating plates get heated
up by gaining the heat from the cathode exhaust gases, on the other hand inlet
reactant gases are heated up when they flow over the preheating plate. These
preheating plates are in thermal communication with the stack copper plates of
anode and cathode respectively, therefore these plates are useful in gaining
thermal energy from the stack bipolar plates as well transferring the same to the
stack bipolar plates through the copper plates.
In a convention PEMFC stack as shown in figure 1, all anode and cathode plates
of stack receives air and hydrogen from their respective inlet gas manifolds
(8A,9A), where inlet manifolds of air and hydrogen are directly in fluid
communication with their inlets of air (14) and hydrogen (16), where as in
integrated gas preheating PEMFC stack as shown in figure 2, inlet gas manifolds
(8A,9A) are not directly in fluid communication with their respective gas inlets
(14,16). In both the stacks (figure 1, figure 2) un-reacted hydrogen and air
(contains product water) from each anode and cathode side plates are routed to
their exit gas manifolds (8B,9B) having a direct fluid communication with their
respective gas outlets of air (15) and hydrogen (17).

A device of integrated gas preheating piate is shown in figure 3 is more generic
design without augmentation of any flow pattern designs, gas distribution
designs varies based on the application and purpose for which the plate is used.
The device is used for multipurpose function such as to provide electrical heating
source using a straight heaters (5) provided with electrical wire (9) where they
can connected to either DC or Ac power source using which the plate can be
maintained at required temperature by connecting the thermocouple (7) to the
temperature controller (8) using which required temperature of the plate can be
maintained. In addition to that there is provision to maintain the device
temperature by circulating the hot exhaust gases of cathode connecting them to
the through holes (4) using the common pipe network (10) through which the
stack exhaust cathode gases enter and leaves through the other pipe network
(11). During this process the gas is allowed to flow twice over the hot plate
device, therefore the reactant gas gains the maximum possible heat. Various
flow patterns can be used which may be similar to fins structure to allow the gas
flow in between. The device is assembled in a stack such that the inlet section is
in fluid communication with the regular gas inlet and the other side (exit section
preheating device) is in fluid communication with the respective inlet gas
manifold.
In principle, heating of air over the cathode side gas preheating plate device is
similar to the process of anode side gas preheating as discussed in
204/KOL/2012.

WE CLAIM :
1. An improved fuel cell stack system assembly operably connected to an
internal gas preheating device to improve performance of proton
exchange membrane fuel cells and high temperature polymer electrolyte
membrane fuel cells, the improvement is characterized by comprising an
anode side reactant preheating plate placed between the insulation plate
and the anode side copper plate; and a cathode side reactant preheating
plate interposed between the cathode copper plate and the insulation
plate, the preheating plates, are connected to an electrical heating source
and circulating hot fluid, the plate being initially heated to a pre-
determined temperature using an electrical heater provided with a
temperature controller, an inlet of the preheating plate is disposed directly
in fluid communication with the regular stack inlet receiving reactants, the
received reactants are heated prior to enter into electrochemical active
zone inlet manifold line of anode or cathode side; and in that the system
is configured to be in direct communication with the cathode exhaust
gases through an external assembly interposed between cathode exit and
the preheating device for preheating the reactants once the stack attains
its startup temperature.
2. The system assembly as claimed in claim 1, wherein the inlet of the anode
side gas preheating plate is positioned in line with hydrogen inlet.
3. The system assembly as claimed in claim 1, wherein the inlet of the
cathode side gas preheating plate is positioned inline with air or oxygen of
stack inlet.

4. The system assembly as claimed in claim 1, wherein the cathode exhaust
hot gas is in fluid communication with the gas preheating device of anode
side and cathode side through an external device for heat recovery from
the cathode side exhaust gases.
5. A method of assembly of an internal gas pre-heating device and a fuel cell
stack for enhancing performance of PEMFC and PEM stacks in a system as
claimed in claim 1, comprising the steps of:

- assembly of the cathode side gas pre-heating plate device with window
gaskets with electrical an heating source;
- assembly of the cathode side gas preheating device in cell/stack for
preheating the air substantially to the cathode exhaust gas temperature
through an assembly between nearest paths of cathode side gas
preheating device and its cathode exit section of top/bottom side;
- assembly of the anode side gas preheating device in cell/stack for
preheating the Hydrogen gas substantially corresponding to the cathode
exhaust gas temperature through an assembly between nearest paths of
anode side gas preheating device and its cathode exit section of
top/bottom side;
- discharging the un-reacted air and produced water through the anode and
cathode side gas preheating device outlets and simultaneous heat
recovery from the exhaust cathode gases;

- heating the stack gas pre-heating plates in absence of electrical power
supply using an exhaust cathode hot gases by circulating through a
plurality of holes provided in the gas preheating device; and
- assembly of the fuel stack at anode and cathode side with multiple
internal and external tightening rods including window gaskets.

ABSTRACT

The invention relates to an improved fuel cell stack system assembly
operably connected to an internal gas preheating device to improve
performance of proton exchange membrane fuel cells and high
temperature polymer electrolyte membrane fuel cells, the improvement is
characterized by comprising an anode side reactant preheating plate
placed between the insulation plate and the anode side copper plate; and
a cathode side reactant preheating plate interposed between the cathode
copper plate and the insulation plate, the preheating plates, are
connected to an electrical heating source and circulating hot fluid, the
plate being initially heated to a pre-determined temperature using an
electrical heater provided with a temperature controller, an inlet of the
preheating plate is disposed directly in fluid communication with the
regular stack inlet receiving reactants, the received reactants are heated
prior to enter into electrochemical active zone inlet manifold line of anode
or cathode side; and in that the system is configured to be in direct
communication with the cathode exhaust gases through an external
assembly interposed between cathode exit and the preheating device for
preheating the reactants once the stack attains its startup temperature.