FIELD OF INVENTION

[000l] The present invention relates to an electro—chemical fuel cell assembly
structure and more particularly to an electro-chemical fuel cell assembly structure
suitable for high temperature working conditions.
5 BACKGROUND OF INVENTION
[0002] For present needs of a power source, fuel cell is an effective and durable
option, which is also a clean and portable power source for transportation
applications and electric vehicles. Unlike battery, which is energy storage medium,
fuel cell is an energy conversion medium. In other words, a fuel cell acts like a l0 continuous reactor, which will produce electricity as long as fuel and oxidant are available.
[0003] A single cell in a fuel. cell is generally composed of a Membrane
Electrode Assembly (MBA) sandwiched between current collectors and fluid flow
field plates. The MBA consists of five different layers; anode gas diffusion layer
l5 (GDL), carbon supported anode catalyst layer, membrane with conducting medium,
. carbon supported cathode catalyst layer and cathode gas diffusion layer. GDL acts as
an electrical connector between fluid flow plate and the catalyst layer.
[0004] The surface area and porosity of GDL plays the major to determine the
diffusivity of the reactants to the catalyst layers. In addition, it helps for the removal
of by-produced water and heat, to improve the mechanical support for the
membrane and to protect the catalyst layer from corrosion by fluid flow other
factors;
[0005] The electro-chemical reactions generally take place on the interface of
the catalyst layer and the GDL. The fluid flow plates will pass. the fuel on one side
of the MBA and oxidant on the other side. The hydrogen fuel passed through an
Anb de side of the MEA reacts with the carbon supported noble metal catalyst to
dissociate into protons, which will pass through the membrane, whilst electrons are
conducted through an external load circuit by the current collector plates to perform
the useful work.
[0006] Current collectors are also used to provide the mechanical support to the
MEA. An oxidant passed through the cathode side of the MEA reacts with the
catalyst to dissociate into anions which will react with protons passed though the
membrane and electrons conducted through an external circuit to form harmless by product
of water and heat. Polymer membrane should conduct or permeate protons
but not fuel, oxidant and electrons i.e. membrane is a proton permeable but
electrically insulating medium.

[0007] In order to avoid the humidification problem, the operating temperature
of the fuels cell is generally maintained above the boiling point of water. The
temperature mainly depends on the conducting medium -in the membrane. Solid
p0lymer,v aqueous phosphoric acid, alkali, molten carbonate and solid oxide fire
commonly used electrolytes for high temperature fuel cells.
[0008] Furthermore, the fuel and oxidant manifolds can be internal or external.
The ‘location of the manifolds mainly depends on the flow channel design of the
fluid-flow field plate. Generally, gaskets are placed between the fluid flow field plate
and MBA to avoid the leakage of fuel or oxidant.
[0009] A number of fuel cells in series are connected to each other to form a fuel
cell stack wherein each fluid flow field plate has one side machined or sintered for
fuel flow while the other side is machined or sintered for oxidant flow. From the
ends, end plates hold together the individual fuel cells and stack of fuel cells support
by help of fasteners. Because of tightening with bolt, MBA and gasket are held
together under compression.
[000l0] Furthermore, during operation, due to the different thermal expansion of
the fuel cell components, the tightening torque will decrease and that affects the
performance and durability of the fuel cell. Compression retention mechanism
should be needed to avoid the relaxation of the tightening torque level
PQTEMT EFFEEF CHENMAE aawmafi2mia l2=R£
[00011] US Granted Patent 600l500 titled “Cylindrical Proton Exchange
Membrane Fuel Cell and Methods of Making Same” discloses a method of
manufacturing a cylindrical fuel‘ cell comprising an anode preferably a porous,
moulded or machined graphite cylindrical electrode which is supported by stainless
steel screen which further acts as an anode current collector. The catalyst—
containing solution is prepared by mixing slurry of catalyst and carbon with an
ionomer solution in an appropriate solvent. This solution is applied to the outer
surface of the anode to a thickness of between about 0.003-0.0l inches. The cathode
electrode which is carbon fibre is? wound around the assembly without contacting the
uncoated portions of the inner electrode. The outer electrode is supported by
stainless steel screen which is acting as cathode current collector. In yet another _
embodiment, yet another commercially available catalyst-coated carbon cloth and
membrane sheet is used. The challenge: of this type of construction is to form an
intimate contact between the layers and to seal the longitudinal seams of the cell.
[000l2] US Granted Patent 6884745 and 690402 titled “Perforated Cylindrical
Fuel cells” discloses tubular shaped fuelcells, which are fluid permeable in the
radiél direction and methods of making the same. The fluid permeable Structure
includes a plurality of perforétions and it is situated around the céntral core. A
catalyst layer is on the outer surface of the central core. This combination of central
core and the catalyst acts as an electrode. The catalyst layer is followed by a solid
polymer electrolyte, second layer of catalyst material and a second fluid permeable
structure. In this arrangemént, fuel is distributed through perforations in the central
cofle and oxidarit is passed through the outer chamber, the inner electrode is the
anode and the outer electrode is the cathode. Thelelectrodes arrangement can further
be reversed. This prior art patent discloses the methods of making perfofated
structure and forming the perforated structure into a tubular fuel cell.
[000l3] US Granted Patent 60635l7 titled “Spiral Wrapped Cylindrical Proton
Exchange Membrane Fuel Cells and Methods of Making Same” discloses the usage
of pre-spiral bundle for making a spiral wrapped cylindrical fuel cell. The hydrogen
flow bath is defined by a sleeve which is in the pre-spiral bundle. The sleeve
comprises of a membrane electrode assembly which is in ionic communication with
the noble metal electro-catalyst. A cylindrical fuel cell is made by abutting a
flexible, porous cathode to the sléeve in ionic communication with a noble metal
catalyst and the sleeve and the cathode around one of the hydrogen inlets are
wrapped. A PEM fuel cell with spiral wrapped configuration reduces the losses
associated with electn‘cal resistance even in a large size fuel cell without increasing
the resistance of both electrode and electrolyte. The major advantages of spiral
geometry is compact packing and self-supporting structure i.e. a packing with
multiple layers and provision for clamping force for every underlying layers.
[000l4] US Granted Patent 6007932 titled “Tubular Fuel Cell Assembly land
Method of Manufacture” discloses an improved construction for a fuel cell, which is
inexpensive to manufacture and eliminates the complexities in the planar design. In
addition, it discloses a fuel cell design, which does not require separate external
reactant source. The assembly consists of porous tubular substrate through which
fuel can be supplied to the anode side. The porous gas permeable structure is.
wrapped around Anode current collector, membrane. electrode assembly and then
cathode current collector. The .current collector element can be either of a braided
wire(s), braided tubes or perforated foils. and is exposed to a reaction fluid. In the
disclosed fuel cell assembly, the anode charge éollector of one wound membrane
electrode assembly is electrically connected to the cathode charge collector of
adjacent membrane electrode assembly.
[000l5] ‘US Granted Patent 6376ll6 titled “Tubular Polymeric Membrane Fuel
Cell System” discloses a mechanically integrated tubular polymeric membrane fuel
cell through manifolds, whichalso acts as electrical power leads. The fuel cell can
be stacked in parallel and series to achieve the required power.>The dual-purpose
manifolds allow the fuel Cell to operate under low parasitic powér losses, thereby
simplifying as well as improving the system. The manifold design mechanically
integrates the fuel cell and the fuel cell stacks without the need of external clamping.
[000l6] US Granted Patent 6972l60 titled “Fuel Cell” discloses a low
temperature fuel cell consists of tubular flexible polymer electrolyte membrane,
with a fuel electrode on one side of the membrane and with an air electrode on other
side of the membrane. Both fuel and air (oxidant) electrode is composed of carbon
fibers on. which a

catalyst is loaded. Even though two types of electrode
arrangement are possible, i.e., fuel electrode on the inner side and air electrode on
the outer side of the tubular polymer electrolyte membrane and vice versa, the
«former was preferred. A mixed solution of l-M sulphuric acid and 3-M methanol
was injected as fuel to the air breathing fuel cell, which was operating at l00 °C.
SUMMARY OF THE INVENTION
[000l7] The objective of present invention is to provide a high temperature based
fuel cell with a tubular structure. By using tubular structure in high temperature fuel
cell to achieve uniform contact pressure distnlbution, better mass transfer, more
gravimetric and volumetnlc energy density without any complex water management
préblem can be achieved.
[000l8] As number of cells incfeases, stacking as well as the removal of
degraded cell will be difficult in the case pf planar design. However, stacking and
l
unstacking are simple in the case of tubular cells. Furthermore, there is ho need of
compression retention mechanism in ‘tubular design as every dell is compressed
individually but in the planar design, all.the cells will be compressed together.
[000l9] Inl yet another Embodiment, the present invention describes a tubular fuel
cell structuré for operation at highér temperatures lwherein outer cover also shields
find protects the fuel cell membrane from humid atmospheric air.
[00020] Summary provided abbve explains the basic features of the invention and
does not limit the scope of the invention. Additional detailed information related to
the enablement of the invention will be provided in the detailed descfiptidn and
accompanying claims. Scope of the invention shall be based on the claims provided.
BRIEF DESCRIPTION OF DRAWINGS
[0002l] The present invention will become more fully understood from the
detailed description given herein below and the accompanying drawing(s). The
drawings provided. herein incorporate and constitute embodiments of the invention
and illustrate several aspects of the invention and togethgr with a description of the
embodiments serve to explain the principles of the invention. Drawings given
below are provided to support the description of the invention and are notl limiting
the scope of the present invention.
[00022] Figure l illustrates the Single Fuel Cell assembly structure with an
exploded View of a fuel cell.
[00023] Figure 2 illustrates the Single Fuel Cell assembly structure; viewed from
the fuel and oxidant outlet/exhaust side.
[00024] Figure 3 illustrates the Single Fuel Cell assembly structure viewed from
the fuel and oxidant intake side.
[00025] Figure 4 illustrates the fuel side flow field design.
[00026] Figure 5 illustrates_the oxidant side flow field design.
DETAILED DESCRIPTION OF THE INVENTION
[00027] The embodiments disclosed Below are not inténded to be exhaustive or to ‘
limit the pfeserit invention to the precise forms Elise‘iosed in the following. detailed
description. Rather, the embodiments are chosen and described so that best enabling
arrangements of the invention can be explained through all possible embodiments
and examples of it. ‘Thg invention may have application to all kind of two wheeled
vehicles.
[00028] Referring to Figure l shows a singie tubular fuel cell assembly l0 which
includes a membrane electrode assembly (MBA) l40 sandwiched betwé‘en fuel flow
field solid tube 20 and oxidant flow field plate 60‘ and héldl under compression by
means of plurality of bolts 70. The MBA 40 has an ion exchange membrane which
will allow only protons to pass through it and porous catalyst layers which are
located on either side of the membrane to perform the electro-chemical reaction i.e.
oxidation on the fuel side and reduction on the oxidant side.
[00029] The MBA further consists of a
.
membrane with proton conducting
medium which will operate at higher temperature ranging from l60 to l80 degree
centigrade. In this present invention, phosphoric acid doped PBI
(Polybenzifnidazole) is used as a membrane. One of the gaskets is placed on fuel
side 30 while another gasket is placed ‘on oxidant side 50; to achieve an effective
sealing. Metal flow field mediums also act as a current collector plate to form an
electrical connection terminal of the fuel cell assembly. Teflon sleeves can be used
over the bolt (not shown in the figure) as alprecautionary method to avoid the short .
circuit between the fuel flow field solid tube and an oxidant flow field plate.
[00030] The; first gasket 30 is partially wrapped around the fuel flow- field plate
60 covering a portion of lateral surface of said fuel flow field plate 20 which forms a
’
covered portion ll which covers said fuel flow field plate 60 and an uncovered
portion l2 which is exposed, on the fuel flow field plate 20.
[0003l] The membrane eleétyode‘assembly 40 is>rolled and wrépped around said
first gasket 30 which cbvers said Covered portion ll and uncovered portionll2lof
said first. gasket 30;.
[00032] The sécond gasket 50 is partially wrapped around said membrane
electrode assembly 40, thus covering a portion of lateral surface of said membrane
electfqde assembly 40;lthereby forming .a‘
covered portion l3 which covers said
membrane electrode assembly 40 and an uncovered portion l4 Which is exposed on
the, membrane eleptrode assembly 40.
[00033] An _oxidant flow field plate 60 is rolled in A cylindrical shapeL—VThe
oxidant flow field pléte 60 comprises oflan oxidant flow path 66 and tightly encloses
said second gasket 50, said membrane electrode assembly 40, said gasket 30 and
said fuel flow field plate 20; which together forms the tubular fuel cell structure l0._
[00034] Referring to Figure 2 and Figure 3., the fuel flow field tube 20 is provided
with an inlet 22 and an outlet 24 for fuel, fuel side power lead 28, and opening for
metal fod heater l00 as well as for temperature sensor 90. The metal rod heaters are
used to heat up the fuel cell to the Operating temperature i.e., l40-l60 degree
centigrade. Furthermore, an oxidant flow field plate 60 has an inlet 62 and outlet 64
for oxidant, oxidant flow channels 66 and oxidant sidé power lead 68.
[00035] The tubular fuel cell l0 is held togetherlby plurality of bolts 70 using
suitable nuts. Gasket 30, and gasket 50 are located at the end portions of each fluid
flow field plate 20, 60 and MBA 40 to prevent the leakage of fuel and oxidant
outside the fuel cell structure. Qxidant which Enters the oxidant inletlopening 62
passes through the oxidant flow channels 66 in thé oxidant flow field plate 60. Fuel
which enters the fuel inlet opening 22 passes through the fuel flow channels 26
in."
the fuel flow field tube 20. The fuel ‘reactsl with the anode electro-catalyst in the
MBA 40 to form protons and eiectrons.
[00036] The protons are allowed to pass through the membrane and the eléctrons
pass through an external circuit. The oxidant which is flowing through an oxidant
flow channels of the dxidant flow field plate 60l reacts with the cathode electrocatalyst
in the MBA 40 and forming anions. The ariions react with the protons
‘ passed through the membrane and electrons fiassed through an external circuit to
form by-product of water vapour and heat.
[00037] Refeming to Figure 4, in fuel flow field tube 20 the .fuel inlet passage and
fuel flow channels 26 are aligned with fuel inlet opening 22. And also, the fuel
outlet passage and fuel flow channels 26 lare aligned with fuel outlet opening 24.‘
[00038] Referring to Figure 5,‘ oxidant flow field plate 60 has an oxidant inlet 62
and outlet 64.The oxidant inletl62 and outlet 64 openings are connected by oxidant
flow Channels 66. Oxidant power lead 68 is uséd to connect to the load. An oxidant

‘ [00039] The fuel cell assembly structure as described above is a single cell high
5 temperature PEM fuel cell and is manufactured to operate at higher temperatures.
This particular fuel céll functioning atlhighér temperature further requires shielding
of said membrane by way of a closed oxidant flow field to avoid the difect contact
of atmospheric air with proton conducting medium which may lead to acid leaching
i.e., the removal of proton conducting medium from the membrane because of high ll0 solubility of phosphoric acid in water.

We claim:
1. A tubular fuel cell assembly structure (10) comprising:

a substantially cylindrical fuel flow field plate (W0) comprising of a fuel flow
path (W6); said fuel flow field plate (W0) functioning as an anode terminal; .
a first gasket (30) partially wrapped around said fuel flow field plate (W0),
thereby covering a portion of lateral surface of said fuel flow field plate (W0)
which forms a coveredportion (11) that partially covers said fuel flow field plate
(W0) along (ends of said fuel flow field plate (W0), and an uncovered portion
(1W) that 'exposes a mid-portion of said fuel flow field plate (W0);
’a membrane electrode assembly (40) rolled and wrapped around said first gasket
(30) which covers said covered portion (11) and uncovered portion (1W) of said
first gasket (30);

a second gasket (50) partially wrapped around said membrane electrode
assembly (40), said second gasket (50) covers a portion of said membrane
electrode assembly (40); said second gasket forms a covered portion (13) which
partially covers said membrane electrode assembly (40) along two ends of said .
membrane electrode assembly (40), and an uncovered portion (14) which
exposes a mid-portion of said membrane electrode assembly (40);

an oxidant flow field plate (60) comprising an oxidant flow path (66)
circumferentially disposed around said second gasket (50),. said membfane
electrode‘assémbly (40), said gasket (30) and said fuel flow field plate (W0), such
that said oxidant flow field plate (60) firmlybnbompasses said second gasket
(50), membrane electrode assembly (40), said gasket (30) and said fuel flow
field plate (W0) and functions as a cathode terminal;
characterized in that:
"said oxidant flow field plate (60) comprises an outer surface (16) and an ‘inner
Surface (17), said inner surface (17) comprises plurality of oxidant flow channels
(66); the oxidant flow field plate (60) is rolled in a cylindrical shape, wherein

said inner surface ('17) comprising said plurality of oxidant flow channels (66)
faces said membrane electrode assembly (40), the oxidant flow channels? (66)
along with the membrane electrode fissembly (40) are shielded to avoid direct
contact of proton conducting medium inside rhembranie electrode assembly (40)
with atmospheric air.

2. The tubular fuel cell assembly structfire (10) wherein the membrane electrode
assembly (40) is made of phosphoric acid doped Polybenzirnidazole (PBI).

3. The tubular fuel cell assembly structure (10) wherein the membrane electrode
assembly (40) is sandwiched between fluid flow field plates (W0) and oxidant
flow field plates (60) to convert fuel and oxidant into water and generate
‘ electricity.

4. The tubular fuel cell assembly structure (10) wherein the gaskets (30, 50) are
.placed between fluid flow field plate and membrane electrode assembly (40) to
prevent leakage of‘oxidant or fuel.