6.

Task 66.1
6. 1

R & D Targets

6.1.1
6. 1.1Development of PEFC Utilizing Pure Hydrogen

Development Target for Phase II (FY 1999 to FY 2003) of WEWE - NET

This R & D work aims at establishing stack technologies for the pure hydrogen
PEFC system and demonstrating a stationary 30 to 50 kW class power generating
system with the electrical efficiency of more than 45% at HHV basis.
6.1.2
6. 1.2

Target for FY 2001

Verification of the reliability of cell stack using a short stack and the design and fabricationof a hydrogen fueled 30 kW class power plant.
6.2
6. 2
6.2.1
6. 2.1R & D Results in FY 2001
Development of Operating System with High Hydrogen Utiliz
Utili z ation

In FY 2000, a cell humidified at the cathode side and a divided stack system (serial flowmethod) consisting of the main and subordinate stacks were developed and the steady
performance under high hydrogen utilization up to 96% was verified by using a 5kW shortstack .In regard to the stacks for a 30 kW class plant which will be manufactured in FY 2002,
it is necessary to verify the stack stability in terms of long hour operation under the start andstop condition with high hydrogen utilization.
6.2.1.1
6.2.1.1 Verification of Long Term Operation Characteristics
In order to verify the reliability under long term operation, a long term operation test wasconducted by a three cell stack manufactured with MEA of FY 2000 specifications. This test
has been continuing since FY 2000 under the internal humidification at cathode, the external
humidification for anode (ambient temperature : 25°C to 30°C), hydrogen utilization of 85%,
air utilization of 40% and current density of 0.2 A/cm2.

Figure6.2.1-1 indicates a stableperformance even after 7,000 hours. In addition, a long term test using a 20 cell stack with FY
2001 specifications was commenced in preparation for the manufacture of stacks for 30 kWclass plant.

Figure6.2.1-2 shows the cell voltage trend.

After more than 1,500 hours ofoperation, the long term operation characteristics of the new stack is similar to those with FY
2000 specification. These two tests will be continued in FY 2002.

-44-

1,000900
Cell Voltage
Cell Voltage[mV] [mV]
at 0.2A/cm2900

CellVoltage
Voltage [mV]
[mV] at
at 0.2A/cm0.2A/cm
Cell800
7002.1mV/1000h

600
NO1CellNO2Cell
NO3Cell

500
400

800700600500

AVE
MAXMIN
2000 spec.

Anode Gas：H 2
Cathode Gas：Air
Current Density：0.2A/cm2
H 2 Utilization：85%
Air Utilization：40%

400
300
200
100300

00

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000 10,000

0500

Operation Time[h] [h]Operation
Time

Fig.6.2.1
Fig.6.2.16.2.1-1 Long Term Test of 3 Cell Short Stack

Figure6.2.1-3

shows

thefield plant such as the room
temperaturestartandtotalof28

Current Density:0.2A/cm
H2 Utilization:85%
Air Utilization:40%

0.758

0.80.70.6

start-stop

0.5

operations were conducted.

20.747
20.2A/cm2AVE

OCV AVE

0510In each operation, the system

15202530

Cycle Number

was operated for two hours
at the rated load after being

2,500

Fig.6.2.1
Fig.6.2.16.2.1-2 Long Term Test of 20 Cell Short Stack

0.9

A

nitrogen purge after stop.

2,000

1.0

using an 85 cell stack withprocedure was simulated to the1,500

1.1

results of the start-stop test
full size cells. The start-stop

1,000

OperationTime
Time [h]Operation[h]cell voltage [V]221,000

Fig6.2.1
Fig 6.2.16.2.1 - 3

StartStart - stop Test of 85 Cell Short Stack

started and data was recorded
after two hours operation to measure the cell voltage which could be affected by a numberof start-stop operations. It was verified that the impact of start-stop operation is minimal
and the average cell voltage degradation was 0.39 mV/cycle.

-45-

6.2.1.2
6.2.1.2 Verification of MultiMulti - Layer Stacks
For their integration to a 30 kW class plant, four 170 cell stacks and one 120 cell stack weremanufactured as the main and the subordinate stacks, respectively. For assembly ofmulti-layer stacks, 20 cell subordinate stack units were firstly assembled and the leakage test
was conducted for each unit to verify that the external leakage and cross leakage met theallowable limit. In the second step, the 20 cell stack units were piled together to make a
170cell stack. Figure 6.2.1-4 shows the external view of the 170 cell stack and Figure6.2.1- 5shows the power generation test results of 170 cell stack.

1.00
0.90

Cell voltage[V]

0.80
0.70
0.60
0.50
0.40

0.3A/cm2
0.2A/cm20.1A/cm2
0.05A/cm2
OCV

Anode Gas：H 2
Cathode Gas：Air
H 2 Utilization：85%
Air Utilization：40%

0.30
0.20
0.10
0.00
1214161

81101

121141

161

Cell No.

Fig.6.2.1
Fig.6.2.16.2.1- 4 170 Cell Stack

Fig.6.2.1
Fig.6.2.16.2.1- 5 Power Generation Test of 170 Cell Stack

6.2.2
6.2.2 Design and Manufacture of 30 kW Class Plant
6.2.2.1
6.2.2.1 System and Equipment DesignThe ambient pressure operation was adopted to satisfy such basic performancerequirements as improved electric efficiency, cost reduction and reliable operation, and themass and heat balances were calculated. The design balance are shown in Figure 6.2.2-1. A
electric efficiency of 50% (LHV) was achieved under the conditions of a fuel cell efficiency of60%, inverter efficiency of 93%, auxiliary equipment efficiency of 91% and hydrogenutilization of 98%. The plant safety was secured by providing the plant with a package
ventilation function, discharged fuel dilution function, combustible gas detection function andcombustible gas purge function. Figure 6.2.2-2 shows the safety measures for fire by hydrogen.

-46-Exhaust G as

Air
T = 65 ℃
P = 0.10 M Pa
F = 0.5 N m 3 /h
H 2 = 75 %H 2 O = 25 %T = 30 ℃
P = 0.12 M Pa
F = 20.8 N m 3 /h
H 2 = 96 %H 2O = 4 %T = 45 ℃
D ilution Fan
P = 0.10 M Pa
3Condenser F = 118 N m /hCell Stack

H2C ooling Tow erAnodeA ir Blow er

C ooling Pum p

C athode

AirCooler
T = 15 ℃
P = 0.10 M Pa
F = 117 N m 3 /h

Stack Cooling Pum p

R ated Pow er : 30kW
E lectrical Efficiency : 45% (H H V, 50% LH V)

W ater Treatm ent

Fig.6.2.2Fig.6.2.2 - 1 Mass & Heat Balance of 30kW Class Power Plant

Occurrence Portion

Occurrence Factor
H2 Leak in Package

Joint by Welding

Elimination of Leak Part

Airtight Test

Confirmation of no Leak Part

Ventilation by Fan

Enough Dilution to Inflammability

Detection of Fan Failure

Automatic Shutdown

Detection by Gas Detector

Automatic Shutdown

Detection by Tem. Fuse

Automatic Shutdown

Dilution by Fan

Enough Dilution to Inflammability

Detection of Fan Failure

Automatic Shutdown

Suction Ventilation by Fan

No Leak from Package Inside

Detection of Fan Failure

Automatic Shutdown

Dilution by FanEnough Dilution to Inflammability

Detection of Fan Failure

Automatic Shutdown

Inside of Package

Fire by Hydrogen

Ignition of Exhaust
H2

Leak from Package
InsideOutside of Package
Ignition of Exhaust
H2

Elimination of Fire Causes

EffectMeasureMeasures for Fire Case

Fig.6.2.2.Fig.6.2.2. - 2 Safety Measures for Fire by Hydrogen-47-6.2.2.2
6.2.2.2 Manufacture
Ma nufacture of 30 kW Class Plant
In order to ensure the compactness and maintainability of the package, the optimal
equipment layout was designed. Figure 6.2.2-3 illustrates the internal layout of the package
and Figure6.2.2-4 shows the external view of the package. Four main stacks units were placedin the highest position for easy management of the humidifying water and drain. In addition,
the rotating machines were placed near the air intake and outlet to improve their accessibility
from outside and their cooling effects. Moreover, the package consists of two compartments ofcombustible gas treatment section and electrical component section which were separated by
the cathode exhaust gas condenser, and combustible gas detectors were installed at the air
intake and outlet to improve the safety features.
Power Unit

Fuel Unit

Fig. 6.2.2
6.2.2--3 BirdBird-eye View of 30kWClass Power Plant
Plant Package

6.2.3
6. 2.3Fig. 6.2.26.2.2-4 The external view of 30kW Class
Power Plant Package

Humidity Control System for Hydrogen Gas Fe
F e ed

6.2.3.1
6.2.3.1 Dehumidification
Dehumidific ation Method by Hollow Fibe
Fib e r Membrane
Applicability of a dehumidification system by hollow fiber membrane (polymer membrane)to this power system was examined as a more economical and compact dehumidification
method than the one by granular absorbent. This dehumidification system by hollow fiber
membrane utilizes the selective permeation and separation of water vapor through-48-the membrane. The one selected thistime is fluorocarbon separation membrane

A part of dry air is usedas purging air

from the standpoint of its high selectivity
and compactness. Figure6.2.3-1 shows theDry Air

principles of dehumidification by hollow
fiber

membrane.

Atthissystem,

pressurized wet air is fed to the inside,

Permeated
Water Vaporand dry air is fed to the outside of thehollow fiber tube. The water vapor in wet
air permeates the membrane due to thepartial pressure difference of water vapor
through the membrane. This system,
therefore, has such characteristics asHollow
Fibre
Membrane

Discharge

maintenance free due to the absenceofmechanicallymovingunits,

water
steamvapor
oxygennitrogen

asimple system configuration and good
controlabrity

totheaimedWet Air

de-humidification level.

Fig.6.2.3
Fig.6.2.36.2.3-1 Principles of Dehumidificationby Hollow Fibe
Membraneane
Fiber Membr6.2.3.2
6. 2.3.2 Preliminary Test of Dehumidification System by Hollow Fibe
Fib e r Tube
The dehumidification unit applied to an actual some equipment is an air dryer designed todehumidify wet air. Therefore there is uncertainly regarding to the permeation of hydrogengas through the membrane together with water vapor. A simple test to simulate thedehumidification system was conducted to measure quantitatively the amount of permeatinghydrogen through the membrane. The results were that the amount of permeating hydrogenis small and the higher the pressure of feed hydrogen the higher the flow rate of purging gas
become, the larger the dehumidification effect becomes resulting in small amount of
permeating hydrogen and large amount of permeating water vapor.

-49-6.2
6.2.3.3 Design of Hydrogen Gas Humidity Control System
Based on the Preliminary test, a hydrogen gas humidity control system was designed tomaintain the required specifications for fuel cells. In this system, the by-product hydrogen gas
supplied from the adjacent factory is supplied through water sealed safety tank. The wethydrogen with water droplet is dehumidified by the hollow fiber membrane dehumidification
unit. Figure6.2.3-2 shows a schematic diagram of hydrogen gas humidity control system.

PureWater

Heating Water
Heating Air

Housing(Water andAir Heater)

To Fuel Cell
Pressure Switch

Frame Arrester
ExhaustAir

Air Compressor
Power RoomPurging Air
Wa ter S ea led
Safety Tank

Thermocouple

Flow
Meter
To Fuel Cell

GasDetector

Hyd rog en
Gas

Hydrogen
Concentration
Meter
Dehumidification
Unit
FlowMeter

To FuelCell

PEFC

Dilute Air
FlowMeter

Dew PointMeter

Fig. 6.2.36.2.3-2 Schematic Diagram of Hydrogen Gas Humidity Control System
6.2.3.4
6. 2.3.4 Design of Peripheral SystemThe remote monitoring system was examined to combine the old data gathered by theexisting system with the new data gathered by this demonstration plant. Moreover, the safety
items of our system were examined and their contents were approved at the experts meetingfor disaster prevention in the factory where our new plant will be installed. Based on thecontents approved by the factory, design work was conducted to dismantle or remodel someparts of the existing equipment.

-50-

6.2.4
6. 2.4

Conclusions

The results in FY 2001 are as follows.
(1)

A low pressure loss-type separator which will contribute to improve plant efficiency
was developed and verified. The 20 cell stacks were manufactured in combination withthe low pressure loss-type separator and the FY 2001 specification MEA designed toimprove performance further at high hydrogen utilization. The initial performance anddurability characteristics for 20 cell stack were confirmed.

(2)

Based on the performance confirmation of the 20 cell stack, a 30 kW class stack wasmanufactured. Prior to its integration to the system, the power generating tests of thesestacks were conducted and the small dispersion of the cell voltages were confirmed.

(3)

The package design with its optimum arrangement to ensure compactness,maintainability and safety requirement were completed.

(4)

The assembly of a 30 kW class plant package incorporating the full stacks andcomponents was almost completed.

(5)

The applicability of the dehumidification system by hollow fiber membrane (polymerfilm) to an actual equipment was examined and verified. The hydrogen gas humidity
control system by the hollow fiber was designed and the component specifications weredecided.

(6)

The contents of the safety measures for the demonstration plant were examined andthe specifications for the remote monitoring system were decided by examining theinput and output signals at the existing power panel and at the new data acquisition
system.

6.3
6. 3
(1)

Future R & D Tasks
Continuation of the long hour test of the three cell stack and 20 cell stack to verify
the steady performance over long hours.

(2)

Factory test of 30 kW class plant to verify its performance and operability.

(3)

Field test of the 30 kW class plant at the by-product hydrogen gas production
site to verify the field performance and reliability .

-51-