TECHNICAL FIELD

The present invention relates to hydrogen/oxygen fuel cells having a solid-oxide electrolytic layer separating an anode layer from a cathode layer; more particularly, to fuel cell assemblies and systems comprising a plurality of individual fuel cells in a stack wherein air and reformed fuel are supplied to the stack; and most particularly, to such a fuel cell system including an integrated air supply system, including a central air pump, distribution manifold, air control valves, mass air flow sensors, and supply ducts, for controllably supplying air to all required fuel cell system functions.

BACKGROUND OF THE INVENTION

Fuel cells which generate electric current by the electrochemical combination of hydrogen and oxygen are well known. In one form of such a fuel cell, an anodic layer and a cathodic layer are separated by an electrolyte formed of a ceramic solid oxide. Such a fuel cell is known in the art as a “solid oxide fuel cell” (SOFC). Hydrogen, either pure or reformed from hydrocarbons, is flowed along the outer surface of the anode and diffuses into the anode. Oxygen, typically from air, is flowed along the outer surface of the cathode and diffuses into the cathode. Each O

2

molecule is split and reduced to two O

−2

anions catalytically by the cathode. The oxygen anions transport through the electrolyte and combine at the anode/electrolyte interface with four hydrogen ions to form two molecules of water. The anode and the cathode are connected externally through a load to complete the circuit whereby four electrons are transferred from the anode to the cathode. When hydrogen is derived by “reforming” hydrocarbons such as gasoline in the presence of limited oxygen, the “reformate” gas includes CO which is converted to CO

2

at the anode via an oxidation process similar to that performed on the hydrogen. Reformed gasoline is a commonly used fuel in automotive fuel cell applications.

A single cell is capable of generating a relatively small voltage and wattage, typically between about 0.5 volt and about 1.0 volt, depending upon load, and less than about 2 watts per cm

2

of cell surface. Therefore, in practice it is known to stack together, in electrical series, a plurality of cells. Because each anode and cathode must have a free space for passage of gas over its surface, the cells are separated by perimeter spacers which are selectively vented to permit flow of gas to the anodes and cathodes as desired but which form seals on their axial surfaces to prevent gas leakage from the sides of the stack. The perimeter spacers may include dielectric layers to insulate the interconnects from each other. Adjacent cells are connected electrically by “interconnect” elements in the stack, the outer surfaces of the anodes and cathodes being electrically connected to their respective interconnects by electrical contacts disposed within the gas-flow space, typically by a metallic foam which is readily gas-permeable or by conductive filaments. The outermost, or end, interconnects of the stack define electric terminals, or “current collectors,” which may be connected across a load.

A complete SOFC system typically includes auxiliary subsystems for, among other requirements, generating fuel by reforming hydrocarbons; tempering the reformate fuel and air entering the stack; providing air to the hydrocarbon reformer; providing air to the cathodes for reaction with hydrogen in the fuel cell stack; providing air for cooling the fuel cell stack; providing combustion air to an afterburner for unspent fuel exiting the stack; and providing cooling air to the afterburner and the stack. There typically are many gas conduit connections between components in the system. These connections typically are conveying high temperature oxidant gas (air and exhaust) or hydrogen-rich reformate fuel at high temperature. Conventional approaches for conveying these gases include plumbing networks comprising metal tubing, pipes, and fittings. These components often have welded or compression-fitting connections that have the undesirable characteristics of high cost, large size, complexity, and moderate reliability. Typically, each component is directed to a specific function without regard to an overarching system architecture and physical consolidation.

What is needed is a means for reducing the complexity, cost, and size of a solid-oxide fuel cell system by consolidating the auxiliary systems, piping, and connections.

It is a principal object of the present invention to simplify the construction and reduce the cost and size of a solid-oxide fuel cell system.

It is a further object of the invention to increase the reliability and safety of operation of such a fuel cell system.

BRIEF DESCRIPTION OF THE INVENTION

Briefly described, in a solid-oxide fuel cell system, a compact, highly space-efficient fuel/air manifold assembly conveys high temperature air, exhaust, and hydrogen-rich fuel such as, for example, reformate or pure hydrogen, to and from the core components of the system. The manifold is a three-dimensional assembly of plates and shallow partitioned elements which are easily and inexpensively formed. When assembled, the manifold comprises a network of passageways which allow for the mounting, close-coupling, and integration of critical fuel cell system components. An integrated fuel reformer partially oxidizes liquid hydrocarbon fuel catalytically into hydrogen and carbon monoxide and interacts via heat exchangers to controllably add or subtract heat in various gas flows in the system. An integrated air supply system pressurizes atmospheric air for providing oxygen for the fuel cell reaction, both through and controllably bypassing cathode air heat exchangers; combustion air for a combustor of tail gas from the anodes; cooling air for electronic controls; and reforming air to a liquid fuel vaporizer integral with the reformer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will be more fully understood and appreciated from the following description of certain exemplary embodiments of the invention taken together with the accompanying drawings, in which:

FIG. 1

is a schematic cross-sectional view of a two-cell stack of solid oxide fuel cells;

FIG. 2

is a schematic mechanization diagram of an SOFC system in accordance with the invention;

FIG. 3

is an isometric view from above of a two-stack fuel cell assembly, shown connected electrically in series between two current collectors;

FIG. 4

is an isometric view like that shown in

FIG. 3

, with a cover enclosing the stacks;

FIG. 5

is an elevational cross-sectional view taken along line

5

—

5

in

FIG. 4

;

FIG. 6

is an elevational cross-sectional view taken along line

6

—

6

in

FIG. 4

;

FIG. 7

is an equatorial cross-sectional view taken along line

7

—

7

in

FIG. 4

;

FIG. 8

is an isometric view from above, showing a fuel cell assembly comprising the apparatus of

FIG. 4

mounted on a manifold in accordance with the invention, along with reforming, combusting, and heat exchanging apparatus for servicing the fuel cell stacks;

FIG. 9

is an isometric view from above, showing the fuel cell assembly of

FIG. 8

mounted in the lower element of a thermal enclosure;

FIG. 10

is an isometric view from above of an integrated air supply system for controllably providing air to the fuel cell assembly shown in

FIGS. 8 and 9

;

FIG. 11

is an exploded isometric view of a fuel cell system in accordance with the invention, showing the air supply system of

FIG. 10

disposed in a structural enclosure, and showing the fuel cell assembly of

FIG. 9

fully enclosed by both upper and lower elements of a thermal enclosure;

FIG. 12

is an isometric view from above of a fully assembled fuel cell system in accordance with the invention;

FIG. 13

is an exploded isometric view from the front, showing a multi-element basal manifold in accordance with the invention for distributing air and reformate fuel and exhaust products through and around the fuel cell stacks, as shown in

FIG. 8

;

FIG. 14

is an isometric view from the rear, showing the manifold of

FIG. 13

partially assembled;

FIG. 15

is an isometric view from the rear, showing the manifold of

FIG. 13

further assembled;

FIG. 16

is a plan view of the lower level of chambers formed by the lower two elements shown in

FIG. 13

;

FIG. 17

is a plan view of the upper level of chambers formed by the third and fourth elements shown in

FIG. 13

;

FIG. 18

is a plan view of the uppermost element shown in

FIG. 13

, showing the mounting surface for the apparatus shown in FIG.

8

.

FIG. 19

is an isometric view from above of a fuel reformer and waste energy recovery (reforWER) system in accordance with the invention;

FIG. 20

is an isometric view from above of an elevational longitudinal section of the reforWER system shown in

FIG. 19

;

FIG. 21

is a plan view of a first horizontal section of the reforWER system shown in

FIG. 19

, showing the path of fuel reformation through the system;

FIG. 22

is a plan view of a second horizontal section of the reforWER system shown in

FIG. 19

, showing the path of combustor exhaust and exchange of heat through the system;

FIG. 23

is a detailed isometric view from above of an air distribution manifold assembly shown in

FIG. 10

; and

FIG. 24

is a horizontal cross-sectional view through the manifold shown in FIG.

23

.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to

FIG. 1

, a fuel cell stack

10

includes elements known in the art of solid-oxide fuel cell stacks comprising more than one fuel cell. The example shown includes two identical fuel cells

11

, connected in series, and is of a class of such fuel cells said to be “anode-supported” in that the anode is a structural element having the electrolyte and cathode deposited upon it. Element thicknesses as shown are not to scale.

Each fuel cell

11

includes an electrolyte element

14

separating an anodic element

16

and a cathodic element

18

. Each anode and cathode is in direct chemical contact with its respective surface of the electrolyte, and each anode and cathode has a respective free surface

20

,

22

forming one wall of a respective passageway

24

,

26

for flow of gas across the surface. Anode

16

of one fuel cell

11

faces and is electrically connected to an interconnect

28

by filaments

30

extending across but not blocking passageway

24

. Similarly, cathode

18

of fuel cell

11

faces and is electrically connected to interconnect

28

by filaments

30

extending across but not blocking passageway

26

. Similarly, cathode

18

of a second fuel cell

11

faces and is electrically connected to a cathodic current collector

32

by filaments

30

extending across but not blocking passageway

26

, and anode

16

of fuel cell

11

faces and is electrically connected to an anodic current collector

34

by filaments

30

extending across but not blocking passageway

24

. Current collectors

32

,

34

may be connected across a load

35

in order that the fuel cell stack

10

performs electrical work. Passageways

24

are formed by anode spacers

36

between the perimeter of anode

16

and either interconnect

28

or anodic current collector

34

. Passageways

26

are formed by cathode spacers

38

between the perimeter of electrolyte

14

and either interconnect

28

or cathodic current collector

32

. Anode spacer

36

and cathode spacer

38

are formed from sheet stock in such a way as to yield the desired height of the anode passageways

24

and cathode passageways

26

.

Preferably, the interconnect and the current collectors are formed of an alloy, typically a “superalloy,” which is chemically and dimensionally stable at the elevated temperatures necessary for fuel cell operation, generally about 750° C. or higher, for example, Hastelloy, Haynes 230, or a stainless steel. The electrolyte is formed of a ceramic oxide and preferably includes zirconia stabilized with yttrium oxide (yttria), known in the art as YSZ. The cathode is formed of, for example, porous lanthanum strontium manganate or lanthanum strontium iron, and the anode is formed of, for example, a mixture of nickel and YSZ.

In operation (FIG.

1

), reformate gas

21

is provided to passageways

24

at a first edge

25

of the anode free surface

20

, flows parallel to the surface of the anode across the anode in a first direction, and is removed at a second and opposite edge

29

of anode surface

20

. Hydrogen and CO diffuse into the anode to the interface with the electrolyte. Oxygen

31

, typically in air, is provided to passageways

26

at a first edge

39

of the cathode free surface

22

, flows parallel to the surface of the cathode in a second direction which can be orthogonal to the first direction of the reformate (second direction shown in the same direction as the first for clarity in FIG.

1

), and is removed at a second and opposite edge

43

of cathode surface

22

. Molecular oxygen gas (O

2

) diffuses into the cathode and is catalytically reduced to two O

−2

anions by accepting four electrons from the cathode and the cathodic current collector

32

or the interconnect

28

via filaments

30

. The electrolyte ionically conducts or transports O

−2

anions to the anode electrolyte innerface where they combine with four hydrogen atoms to form two water molecules, giving up four electrons to the anode and the anodic current collector

34

or the interconnect

28

via filaments

30

. Thus cells

11

are connected in series electrically between the two current collectors, and the total voltage and wattage between the current collectors is the sum of the voltage and wattage of the individual cells in a fuel cell stack.

Referring to

FIG. 2

, a schematic mechanization diagram of a solid-oxide fuel cell system

12

in accordance with the invention includes auxiliary equipment and controls.

A conventional high speed inlet air pump

48

draws inlet air

50

through an air filter

52

, past a first MAF sensor

54

, through a sonic silencer

56

, and through a cooling shroud

58

surrounding pump

48

. Preferably, an electronics cooling duct

51

(

FIG. 10

) is also provided in the inlet air feed as a preferred residence for electronic control system

200

.

Air output

60

from pump

48

, at a pressure sensed by pressure sensor

61

, is first split into branched conduits between a feed

62

and a feed

72

. Feed

62

goes as burner cooling air

64

to a tail gas afterburner or tail gas combustor

66

having an igniter

67

via a second MAF sensor

68

and a burner cool air control valve

70

.

Feed

72

is further split into branched conduits between an anode air feed

74

and a cathode air feed

75

. Anode feed

74

goes to a hydrocarbon fuel vaporizer

76

via a third MAF sensor

78

and reformer air control valve

80

. A portion of anode air feed

74

may be controllably diverted by control valve

82

through the cool side

83

of reformate pre-heat heat exchanger

84

, then recombined with the non-tempered portion such that feed

74

is tempered to a desired temperature on its way to vaporizer

76

. Downstream of vaporizer

76

is a start-up combustor

77

having an igniter

79

. During start-up, when the reformer is cold or well below operating temperature, vaporized fuel is ignited in combustor

77

and the burned gas is passed directly through the reformer to warm the plates therein more rapidly. Obviously, the start-up combustor is deactivated during normal operation of the system.

Cathode air feed

75

is controlled by cathode air control valve

86

and may be controllably diverted through cathode bypass air feed

87

by cathode air preheat bypass valve

88

through the cool side

90

of cathode air pre-heat heat exchanger

92

on its way to stacks

44

,

46

. After passing through the cathode sides of the cells in stacks

44

,

46

, the partially spent, heated air

93

is fed to afterburner

66

.

A hydrocarbon fuel feed pump

94

draws fuel from a storage tank

96

and delivers the fuel via a pressure regulator

98

and filter

100

to a fuel injector

102

which injects the fuel into vaporizer

76

. The injected fuel is combined with air feed

74

, vaporized, and fed to a reformer catalyst

104

in main fuel reformer

106

which reforms the fuel to, principally, hydrogen and carbon monoxide. Reformate

108

from catalyst

104

is fed to the anodes in stacks

44

,

46

. Unconsumed fuel

110

from the anodes is fed to afterburner

66

where it is combined with air supplies

64

and

93

and is burned. When gases are below self ignition temperature, they are ignited by igniter

67

. The hot burner gases

112

are passed through a cleanup catalyst

114

in main reformer

106

. The effluent

115

from catalyst

114

is passed through the hot sides

116

,

118

of heat exchangers

84

,

92

, respectively, to heat the incoming cathode and anode air. The partially-cooled effluent

115

is fed to a manifold

120

surrounding stacks

44

,

46

from whence it is eventually exhausted

122

.

Still referring to

FIG. 2

, a first check valve

150

and a first oxygen getter device

124

are provided in the conduit feeding reformate

108

to the anodes (not visible) in stacks

44

,

46

. A second check valve

152

and second oxygen getter device

126

are similarly provided in the conduit feeding spent reformate

110

from the anodes to afterburner

66

. As described above, during cool-down of the fuel cell stacks after shut-down of the assembly, it is important to prevent migration of oxygen into anode passageways

24

wherein anode surface

20

, comprising metallic nickel, would be subject to damaging oxidation. Each check valve includes a typical frusto-conical valve seat

154

receptive of a valve ball

156

. Preferably, each valve

150

,

152

is oriented within SOFC system

12

such that the ball is held in the seat by gravity when reformate is flowed through the system in the forward direction. Thus, fuel flow opens the valve sufficiently for fuel to pass in the forward direction. When SOFC system

12

is shut down, each valve is closed by gravity. The valves may not be identical, as oxygen flows opposite to the reformate in valve

152

, but in the same direction as the reformate in valve

150

, so the balls and seats may require different weights and/or sizes to function as intended. Each getter

124

,

126

includes a passageway

128

having an inlet

130

and an outlet

132

through which reformate is passed during operation of the fuel cell assembly. Within the passageway is a readily-oxidized material

134

(oxygen-reducing means), for example, nickel metal foam, nickel wire or nickel mesh, which is capable of gettering oxygen by reaction therewith but which does not present a significant obstruction to flow of reformate through the passageway. Nickel in the getters reacts with oxygen to produce nickel oxide, NiO, when the assembly is shut down, thus protecting the nickel-containing anodes from oxidation. When the assembly is turned back on, reformate is again produced which, in passing through the getters, reduces the NiO back to metallic nickel, allowing the getters to be used repeatedly.

Still referring to

FIG. 2

, three-way control valve

160

is disposed in line

93

conveying spent cathode air from the stacks

44

,

46

to combustor

66

. To control combustion temperature in combustor

66

by controlling air volume sent thereto, a portion of spent cathode air may be bypassed around the combustor and diverted into the combustor exhaust stream downstream of heat exchanger

84

. If the mixture in the combustor is relatively rich in fuel, as may happen during start-up, the combustion temperature can be high enough to generate undesirable oxides of nitrogen and/or damage the combustor components. If the mixture is relatively lean in fuel, the resulting combustion temperature can be too low for supporting an endothermic reforming reaction, or can cause reduced efficiency in the cathode pre-heat heat exchanger

92

.

For clarity of presentation and to enhance the reader's understanding, the numbers of elements of the invention as presented further below are grouped in century series depending upon the functional assembly in which the elements occur; therefore, elements recited above and shown in

FIGS. 1 and 2

may have different numerical designators when shown and discussed below, e.g., stacks

44

,

46

become stacks

344

,

346

.

Referring to

FIGS. 3 through 7

, in a fuel cell stack assembly

300

in accordance with the invention, the cells

311

are arranged side-by-side and may comprise a plurality of cells

311

, respectively, such that each of first stack

344

and second stack

346

is a stack of identical fuel cells

311

. The plurality of cells is preferably about

30

in each of the two stacks. The cells

311

in stack

344

and stack

346

are connected electrically in series by interconnect

347

, and the stacks are connected in series with cathode current collector

332

and anode current collector

334

on the bottom of the stacks. The current collectors are sized to have a “footprint” very close to the same dimension as a cover-sealing flange

340

. The current collectors preferably are adhesively sealed to a stack mounting plate

338

, and the stacks preferably are in turn adhesively sealed to the current collectors. The sealing flange

340

for the cover

342

and top

343

is then mounted and sealed to the current collector plates. A gasket

341

between flange

340

and the current collectors is a dielectric so that flange

340

does not cause a short between the current collectors. Power leads

350

,

352

are attached to current collectors

332

,

334

, respectively, through strong, reliable and highly conductive metallurgical bonds, such as brazing. In this manner, the current collectors may pass under the cover sealing flange

340

, with no additional sealing or power lead attachment required, and do not have to pass undesirably through the cover itself, as in some prior art stack assemblies. Passing leads through the cover makes the assembly more complex and less reliable.

Referring to

FIG. 8

, a fuel cell assembly

400

in accordance with the invention comprises stack assembly

300

operatively mounted on an integrated fuel/air manifold assembly

500

which also supports first and second cathode air heat exchangers

600

and an integrated fuel reformer and waste energy recovery unit (“reforWER”)

1100

. Assembly

400

receives air from air supply system

900

(

FIGS. 10-12

) as described below and selectively preheats air going to the reformer. ReforWER

1100

reforms hydrocarbon fuel, such as gasoline, into reformate fuel gas comprising mostly hydrogen, carbon monoxide, and lower-molecular weight hydrocarbons, tempers the air and reformate entering the stacks, selectively burns fuel not consumed in the stacks, recovers heat energy generated in various internal processes which would otherwise be wasted, and exhausts spent air and water, all in order to efficiently generate DC electric potential across power leads

350

,

352

(not visible in FIG.

8

). The structure and internal functioning of reforWER

1100

is discussed in detail hereinbelow.

Referring to

FIGS. 9 through 11

, there are two basic functions for the enclosure of a fuel cell system. The first is to provide thermal insulation for the components which function at an elevated temperature (700-900° C.) to maintain them at that temperature for efficient operation, to protect lower temperature components, and to reduce the exterior temperature over the overall unit to a human-safe level. The second is to provide structural support for mounting of individual components, mounting the system to another structure such as a vehicle, protection of the internal components from the exterior environment, and protection of the surrounding environment from the high temperatures of the fuel cell assembly. Prior art systems utilize a single enclosure to provide all functions, which can be complex and costly to fabricate and assemble, and consumptive of space.

Still referring to

FIGS. 9 through 11

, in the present invention, enclosure of the fuel cell assembly comprises two nested enclosures: a thermal enclosure

700

and a structural enclosure

800

. Fuel cell assembly

400

is first disposed in a “clam-shell” type thermal enclosure

700

, comprising a bottom portion

702

and a top portion

704

, which in turn is disposed in a structural enclosure

800

. The split line

706

between bottom portion

702

and top portion

704

is easily arranged such that all pipes, manifolds, shafts, power leads, etc., which need to pass between the “hot zone”

716

within the thermal enclosure and the “cool zone”

816

within the structural enclosure, do so in the middle of split line

706

. This provides for easy assembly of the hot components into the thermal enclosure. Preferably, flexible bellows isolator couplings

902

-

1

,

902

-

2

,

904

-

1

,

904

-

2

,

912

in air tubes connecting the air supply system to the manifold system and disposed specifically within the wall of the thermal enclosure, as shown in

FIG. 10

, to further minimize heat transfer out of the hot zone.

First, all hot zone components, included in assembly

400

, are nestled into in bottom portion

702

, which may be provided with a conforming well

708

for securely holding and cushioning assembly

400

, as shown in FIG.

9

. The mating surface

710

of bottom portion

702

, along split line

706

, is configured as required to accommodate the lower halves of the components extending through enclosure

700

. Top portion

704

is configured to matingly engage bottom portion

702

. Top portion

704

is placed onto bottom portion

702

and may be sealed thereto along line

706

as desired. Thermal enclosure

700

may be formed of any suitable high-temperature high-efficiency insulating material, as is known in the insulating art, and may be a composite including a light-weight metal case. The range of suitable insulating materials is expanded by removing the constraint of overall structural integrity afforded by providing a separate structural enclosure

800

.

Structural enclosure

800

preferably is fabricated from thicker metal, for example, to provide structural strength and a simple shape, such as a box with a removable lid, for ease of fabrication. Features such as brackets, studs, electrical connectors, studs, weld-nuts, air intake ducts, and exhaust ducts, for example, may be part of the structural enclosure for mounting internal components thereto and for connecting the system to external structures. Features for vibration and shock isolation (not shown) may also be provided with the enclosure.

The air control assembly

900

is connected to elements of fuel cell assembly

400

projecting through split line

706

; and assemblies

700

,

900

are then installed within structural enclosure

800

, as shown in

FIG. 12

, to form a fuel cell system

1000

in accordance with the invention. Preferably, control system

200

(shown schematically in

FIG. 2

as power conditioner

202

, circuit protection I/O

204

, drivers

206

, and electronic control unit

208

, but not visible in

FIG. 12

) is also installed onboard the system within cool zone

816

to minimize the number of discrete signals

210

which must be passed through enclosure

800

via connector

820

. Note also that high current capacity power leads also pass through enclosure

800

via dual connectors

821

. Preferably, control system

200

is mounted in either an air inlet duct

51

supplying air pump

48

or in active air flow space (not shown) in air distribution manifold block

908

(FIGS.

23

-

24

), for maximum cooling of electronic components as well as beneficial pre-heating of the incoming air.

Referring to

FIGS. 13 through 18

, an integrated fuel/air manifold assembly

500

receives air via flexible bellows elements from air supply system

900

and reformed fuel from reforWER

1100

and conveys high temperature air, exhaust, and hydrogen-rich reformate fuel to and from the core components of the system. Basal manifold assembly

500

is shown in

FIG. 13

as comprising a three-dimensional assembly of three perforated plates and two partitioned elements which are easily and inexpensively formed and which comprise a two-level network of passageways which allow for the mounting, close-coupling, and integration of critical fuel cell system components, including heat exchangers, combustors, fuel reformers, solid-oxide fuel cell stacks, check valves, threaded inserts, and catalyzed and non-catalyzed filters. Of course, while a five-component manifold is shown for simplicity, within the scope of the invention any two of the perforated plates obviously may be incorporated into the partitioned elements, through appropriate and obvious casting or moulding processes, such that the manifold comprises only three elements.

It should be noted that manifold

500

is actually two mirror image manifolds

500

-

1

,

500

-

2

sharing some common features, for example, cathode air return from the stacks. Thus, reformate fuel flows from reforWER

1100

in two parallel streams to stacks

344

and

346

and is returned to reforWER

1100

in two parallel streams. Likewise, cathode air flow from air supply system

900

is divided into two parallel streams and enters into each manifold

500

-

1

,

500

-

2

via mirror image bellows insulator couplings

902

-

1

and

902

-

2

(

FIGS. 8-10

and

13

). Fuel cell assembly

400

thus is seen to have its fuel cell stacks

344

,

346

connected in series electrically but serviced by gas flows in parallel.

For simplicity of presentation and discussion, except where functions are unique, the following construction and function is directed to manifold

500

-

1

but should be understood to be equally applicable to mirror-image manifold

500

-

2

.

Bottom plate

502

is the base plate for the manifold and forms the bottom for various chambers formed by combination of plate

502

with lower partitioned element

504

, defining a lower distribution element

505

, as shown in FIG.

16

. Intermediate plate

506

completes the chambers in element

504

and forms the bottom plate for upper partitioned element

508

, defining an upper distribution element

509

. Top plate

510

completes the chambers in element

508

and forms the mounting base for fuel cell assembly

300

, heat exchangers

600

, and reforWER unit

1100

, as described above.

In operation, air enters a first bottom chamber

512

via coupling

902

-

1

, flows upwards through slots

514

-

1

,

514

-

2

,

514

-

3

into heat exchanger

600

-

1

, through the heat exchanger conventionally where the air is heated as described below, downwards through slot

516

-

3

into a first upper chamber

518

, thence through opening

520

in plate

506

into a second lower chamber

522

. In chamber

518

, the heated air is controllably mixed with cool air entering the chamber via bypass bellows insulator coupling

904

-

1

from air supply assembly

900

. The tempered air flows upwards from chamber

522

through opening

524

in plate

506

into a chamber

526

which defines a cathode supply plenum for supplying reaction and cooling air upwards through slotted openings

528

to the cathode air flow passages in stack

344

. Spent air is returned from the cathodes via slotted openings

530

into a cathode return plenum

532

and flows downwards through an opening

534

in plate

506

into a common cathode air return runner

536

leading into a tail-gas combustor

1102

within reforWER

1100

.

Hot reformate from reforWER

1100

enters manifold

500

-

1

via opening

538

in top plate

510

and flows into chamber

540

, thence downwards through opening

542

into a feed runner

544

, and upwards through opening

546

into a chamber

548

defining an anode supply plenum for stack

344

.

Preferably, opening

546

defines a seat for a valve having a ball

550

(FIG.

14

), preferably held in place by gravity, for allowing flow of reformate during operation but preventing flow of oxygen into the anodes when the system is shut down. Further, preferably, feed runner

544

and/or chamber

548

contains an oxygen-reactive material (not shown here but indicated as

134

in FIG.

2

), such as nickel wool, through which reformate may easily pass but which can scavenge any oxygen passing by ball

550

on its way to the anodes.

Preferably, lower chamber

522

and feed runner

544

are configured to maximize the area of the common wall between them, such that chamber

522

and runner

544

define a co-flow heat exchanger which tends to decrease the temperature difference between the cathode supply air and the anode supply reformate.

From chamber

548

, reformate flows upwards through slots

552

into the anode flow passages in stack

344

. Spent reformate (“tail gas”) flows downwards through slots

554

into an anode return plenum

556

and thence downwards through opening

558

into a reformate return runner

560

. From runner

560

, spent reformate flows upwards through opening

562

into elongate chamber

564

common with manifold

500

-

2

and thence through openings

566

into the tail-gas combustor

1102

in reforWER

1100

. Preferably, opening

562

is also formed as a check valve seat like opening

546

for receiving a check ball

563

preferably held in place by gravity for preventing reverse flow of oxygen into the anodes when the system is shut down. Further, preferably, plenum

556

and/or runner

560

, like chamber

548

, contains an oxygen-reactive material (not shown here but indicated as

134

in FIG.

2

), such as nickel wool, through which the tail gas may easily pass but which can scavenge any oxygen passing by ball

563

on its way to the anodes.

Burned tail gas from the combustor enters manifold

500

-

1

via slot

568

-

3

and flows via slots

568

-

2

,

568

-

1

into bottom chamber

570

and thence through opening

572

into chamber

574

which acts as a supply plenum for cathode air heat exchanger

600

-

1

. Burned tail gas flows upward from chamber

574

through openings

576

and through heat exchanger

600

-

1

, thus heating incoming cathode air, returning through openings

578

into chamber

580

and thence via openings

582

into a tempering jacket space

354

(

FIG. 7

) surrounding stack

344

between the fuel cells

311

and cover

342

. The stack is thus tempered by the exhaust gas. The burned tail gas returns from jacket

354

via openings

584

into an exhaust plenum comprising openings

586

-

3

,

586

-

2

,

586

-

1

which is vented to the atmosphere by exhaust pipe

588

and pipe flange

590

.

Referring to

FIGS. 19 through 22

, a reforWER

1100

in accordance with the system is mounted on the upper surface of plate

510

(

FIG. 18

) over opening

566

and slot

568

-

3

in manifold portions

500

-

1

,

500

-

2

, as described below. ReforWER

1100

is generally laid out having a first portion

1104

for receiving, metering, and mixing liquid fuel and air, for vaporizing the fuel/air mixture, and for passing the vaporized mixture into a second portion

1106