DUT description

The device under test (DUT) in this study is HT-PEM fuel cell composed of MEA and flow field plates. MEA is “heart” of fuel cell where electrochemical reactions take place and flow field plates supply and remove reactants and products, respectively.

3.1.1 HT-MEA

All experiments were conducted using commercial BASF Celtec®_{-P 2100 HT-MEA of 938}

μm thickness and 96 cm2 _{active area. The membrane was phosphoric acid doped}

polybenzimidazole (PBI) with woven carbon cloth gas diffusion layer. Based on technical specifications declared by the producer, the catalyst on the cathode side is made of a Pt- alloy with a loading of 0.75 mg Pt cm-2 whereas the anode Pt catalyst loading is 1.0 mg Pt cm-2. Other specification details concerning the HT-MEA remaining confidential and are not disclosed by the manufacturer.

3.1.2 Flow field plates

The Flow field plates are made of graphite composite material (FU 4369 HT) supplied by Schunk and more details regarding the material properties of plates are provided in Appendix A-1. The required flow pattern is carefully inscribed on to graphite plate using KERN CNC High Precision Micro Milling and Drilling Machine type EVO. The flow pattern on the anode side was multiple serpentine design and remained unchanged for all experiments. Three different flow field designs for the cathode side were used in this study to achieve the purpose of this thesis. The three designs are shown in Figure 3-1 multiple serpentine, segmented serpentine, straight and parallel. More details concerning the specifications of individual design are given in Table 3-1. The graphite plate on cathode side is of 4.675 mm thickness and 102 mm X 102 mm geometrical area.

a) Multiple serpentine b) Segmented serpentine

Figure 3-1 Graphite bipolar plate with flow field designs used for cathode in this study.

The apparent contact area of MEA with graphite flow plate is calculated for all the three designs and the values are almost the same. Multiple serpentine design consists of 23 channels with channel length of 302 mm each. Segmented serpentine design has 4 segments with 4 channels p

segments with 17 channels for each segment. The three flow field designs are in ‘Z’ type configuration. All the designs have channel depth of 0.735 mm.

Table 3-1 Design specifications of flow field pl

Flow field

design area with Contact MEA, % Multiple serpentine 53 Segmented serpentine 52 Straight and parallel 53

3.2 Test set-ups

The HT-MEA is sandwiched between two graphite plates with multiple serpentine flow field on anode side (Figure 3

(Figure 3-1) are used. The HT

b) Segmented serpentine c) Straight and parallel

Graphite bipolar plate with flow field designs used for cathode in this study.

of MEA with graphite flow plate is calculated for all the three designs and the values are almost the same. Multiple serpentine design consists of 23 channels with channel length of 302 mm each. Segmented serpentine design has 4 segments with 4 channels per each segment. The straight and parallel design has 4 segments with 17 channels for each segment. The three flow field designs are in ‘Z’ type configuration. All the designs have channel depth of 0.735 mm.

1 Design specifications of flow field plates.

area with channels/ No. of segments Channel dimensions Length, mm Width, mm Depth, 23 302 0.7 0.735 4/4 253 1 0.735 17/4 82 0.7 0.735

MEA is sandwiched between two graphite plates with multiple serpentine flow field on anode side (Figure 3-1a) and three different flow field designs on cathode side

The HT-MEA is compressed with 3 N m torque.

c) Straight and parallel

Graphite bipolar plate with flow field designs used for cathode in this study.

of MEA with graphite flow plate is calculated for all the three designs and the values are almost the same. Multiple serpentine design consists of 23 channels with channel length of 302 mm each. Segmented serpentine design has 4 er each segment. The straight and parallel design has 4 segments with 17 channels for each segment. The three flow field designs are in ‘Z’ type

Channel dimensions Rib Depth, mm Width, mm 0.735 0.7 0.735 1 0.735 0.7

MEA is sandwiched between two graphite plates with multiple serpentine flow 1a) and three different flow field designs on cathode side

a)

Figure 3-2 a) manual test station and b) components of fuel cell assembly.

The fuel cell is tested using manual test station as shown in Figure 3 control based application. The fuel cell assembly is

gasket, current collector, insulating sheet and end plates as shown in Figure 3

end plates are made of aluminium and current collector plates are made of copper metal coated with gold. The temperature is controlled

to silicone heating pads (200 W) mounted on the surface of aluminium endplates. The water collection points from anode and cathode are extended using a Teflon tube and connected to water bottle of limited capacity. Active c

for water condensation. Prolonged operation at high temperature caused issues related to fuel cell set-up (such as copper plates, copper bars are used to connect the fuel cell to thick current carrying cables from DC load bo

inaccurate results. This particular test set

b)

2 a) manual test station and b) components of fuel cell assembly.

The fuel cell is tested using manual test station as shown in Figure 3-2a with LabView control based application. The fuel cell assembly is achieved using in-house designed gasket, current collector, insulating sheet and end plates as shown in Figure 3

end plates are made of aluminium and current collector plates are made of copper metal coated with gold. The temperature is controlled using a PID controller connected to silicone heating pads (200 W) mounted on the surface of aluminium endplates. The water collection points from anode and cathode are extended using a Teflon tube and connected to water bottle of limited capacity. Active cooling methods are not employed for water condensation. Prolonged operation at high temperature caused issues related up (such as copper plates, copper bars are used to connect the fuel cell to thick current carrying cables from DC load box) leading to measurement errors and inaccurate results. This particular test set-up is used for evaluation of three flow fields 2a with LabView house designed gasket, current collector, insulating sheet and end plates as shown in Figure 3-2b. The end plates are made of aluminium and current collector plates are made of copper using a PID controller connected to silicone heating pads (200 W) mounted on the surface of aluminium endplates. The water collection points from anode and cathode are extended using a Teflon tube and ooling methods are not employed for water condensation. Prolonged operation at high temperature caused issues related up (such as copper plates, copper bars are used to connect the fuel cell to x) leading to measurement errors and up is used for evaluation of three flow fields

(section 4.2) and before each test the gold coated copper current collector plates and copper bars are scrubbed to remove surfa

has not resulted in significant improvement in measurements. So, all the experiments (section 4.1, 4.3, 4.4 and 4.5) are conducted using FuelCon Evaluator as controlling the operation parameters is accurate.

C1000-LT fuel cell test station that was adapted for HT Figure 3-3 along with flow field plates.

a)

Figure 3-3 a) FuelCon fuel cell test stand and cathode flow serpentine c) segmented serpentine d) straight and parallel design.

(section 4.2) and before each test the gold coated copper current collector plates and copper bars are scrubbed to remove surface impurities and other corrosion products but has not resulted in significant improvement in measurements. So, all the experiments (section 4.1, 4.3, 4.4 and 4.5) are conducted using FuelCon Evaluator as controlling the operation parameters is accurate. The HT-PEMFC is tested using FuelCon Evaluator LT fuel cell test station that was adapted for HT-PEMFC operation as shown in

3 along with flow field plates.

3 a) FuelCon fuel cell test stand and cathode flow field plates b) multiple serpentine c) segmented serpentine d) straight and parallel design.

(section 4.2) and before each test the gold coated copper current collector plates and ce impurities and other corrosion products but has not resulted in significant improvement in measurements. So, all the experiments (section 4.1, 4.3, 4.4 and 4.5) are conducted using FuelCon Evaluator as controlling the PEMFC is tested using FuelCon Evaluator PEMFC operation as shown in

b)

c)

d)

The MEA is compressed between graphite plates using Cell fixture from balticFuelCells GmbH model cF 100/400 HT and quick connect fixture qCf FC100/400 shown in F

4a is used to apply uniform and repeatable compression pressure of 2 Nmm

fixture is slightly modified to accommodate the flow field plates and the drawings of three flow fields used on FuelCon Evaluator are shown in Appendix A

gases are supplied to fuel cell in counter flow configuration. The soft

in Figure 3-4b from fuel cell test station is used to control the operating conditions and data logging process.

a)

Figure 3-4 a) Cell fixture quick connect fixture integrated in FuelCon test stand b) FuelConTestWork software

parameters and data collection.