171 sreenivasulu

AN EXPERIMENTAL STUDY ON FLOW FIELDS IN A PEM FUEL CELL

B. Sreenivasulu

Dept of Chemical Engg, G V P College of Engineering, Visakhapatnam-48.

V. Dharma Rao , B.Govinda Rao

Dept of Mechanical Engg, G V P College of Engineering, Visakhapatnam-48.

S.V. Naidu,

Dept of Chemical Engineering, Andhra University, Visakhapatnam-3.

Vasu Gollangi

Fuel Cell and Renewable Energy, BHEL R&D, Hyderabad.

INTRODUCTION

• A fuel cell is an electrochemical energy converter that converts chemical energy of fuel directly into DC electricity.

• Fuel cells resemble batteries in many ways, but in contrast to them they do not store the chemical energy, fuel has to be continuously provided to the cell to maintain the power output.

Typically, a process of electricity generation

1.Combustion of fuel converts chemical energy of fuel into heat,

2.This heat is then used to boil water and generate steam,

3. Steam is used to run a turbine in a process that converts thermal energy into mechanical energy, and finally

4. Mechanical energy is used to run a generator that generates electricity.

Typical Characteristics of Fuel Cells

AFC PAFC MCFC SOFC PEMFC DMFC

Primary

Application

Space Vehicles and drinking water

Statinory Power

Statinory Power

Vehicle auxiliary Power

Automotive and Statinory Power

Portable Power

Electrilyte Concentrated (30 – 50%) KOH in H20

Concentrated 100% Phosphoric acid

Molten carbonate retained in a ceramic matrix of LiALO2

Yttrium-Stabilized Zirkondioxide

Polymer (plastic) Membrane

Polymer (plastic) Membrane

Operating Temperature Range

50 -200 OC 150 – 200 OC 600 - 700 OC 700 – 1000 OC 50 – 100 OC 30 – 60 OC

Charge Carrier OH- H+ CO3- O- H+ H+

Prime Cell Component

Carbon-based Graphite-based Stainlees Steel Ceramic Carbon-based Carbon-based

Catalyst Platinum Platinum Nickel Perovskitse Platinum Pt-Pt/ruPrimary Fuel H2 H2 H2, CO, CH4 H2, CO H2 Methanol

Start-up-Time min Hours Hours Hours Sec-min Sec-minPower Density (KW/m3)

1 0.8-1.9 1.5 - 2.6 0.1 -1.5 3.8 - 6.5 0.6

Fuel Cell Efficiency

50 - 60% 55% 55 - 65% 55 - 65% 50 - 60% 30 - 40%

Advantages of PEM fuel cells:

•Low operating temperature (<100oC)

•Quiet operation

•High power density

•Quick startup and

•Zero emissions, which leads directly to a reduction

of air pollution and greenhouse gases.

Components

Working of Fuel Cell

Components of Fuel Cell

Component Description Common Types

Proton exchangemembrane

Enables hydrogen protons to travel from the anode to the cathode.

Persulfonic acid membrane(Nafion 112, 115, 117)

Catalyst layer Breaks the fuel into protons andelectrons. The protons combine with the oxidant to form water at the fuel cell cathode. The electrons travel to the load.

Platinum/carbon catalyst

Gas diffusion layer

Allows fuel/oxidant to travel through the porous layer, whilecollecting electrons

Carbon cloth or Toraypaper

Flow field plate Distributes the fuel and oxidantto the gas diffusion layer

Graphite, stainless steel

Gasket Prevent fuel leakage, and helps todistribute pressure evenly

Silicon, Teflon

End plate Holds stack layers in place Stainless steel, graphite,polyethylene, PVC

Functions of components

The experimental set up contains a single PEM fuel cell with active surface area 9.6 × 9.8 cm.

The membrane electrode assembly (MEA) consists of Nafion 1135 (88 µm) Gas diffusion layers (400 µm) Catalyst layers

• Catalyst used is carbon supported platinum• Catalyst ink is applied as a layer on the GDL• The catalyst loading on the anode-side is 0.15 mg/cm2

with a thickness of catalyst layer of 20 µm• A catalyst loading of 0.3mg/cm2 is used on the cathode-

side with a thickness of catalyst layer of 40 µm

The MEA is placed between two graphite plates and is pressed between gold-coated copper plates.

Experimental Setup

Different Parameters studied

Effect of Channel geometry

•4-Serpentine

•Interdigitated

•Dual-inlet-single-outlet

Effect of Stoichiometry

4-Serpentine flow channel fig

Schematic diagram of 4-serpentine flow channel

Dimensions of the computational domain

Channel length :98mm

Channel width :1.5mm

Rib width :2mm

Channel height :0.8mm

GDL thickness :0.4mm

Anode Catalyst-layer thickness :0.02mm

Cathode Catalyst-layer thickness :0.04mm

Membrane thickness :0.088mm

Active area :94cm2

All the components are meshed and assembled in GAMBIT.

Interdigitated flow channel

Photograph of single PEM fuel cell Experimental set up

Dual inlet single outlet flow channel

Current (A)

0 10 20 30 40

Vol

tage

(V

)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

15010050

% excess oxygen flow rate

Pressure =1atm, H2 flow rate=0.32lpm,Cell temperature=40oC, Anode and Cathode humidification temperature=30oC

Effect of Stoichiometry

Interdigitated flow channel

Current (A)

0 10 20 30 40

Vol

tage

(V

)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

15010050

% excess oxygen flow rate

50% excess O2 flow rate

Current(A)

0 10 20 30 40

Volt

age

(V)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

4-Serpentine flow channel Interdigitated flow channelDual inlet single outlet flow channel

Effect of flow Channel

Pressure =1atm, H2 flow rate=0.32lpm,O2 flow =0.22lpm,Cell temperature=40oC, Anode and Cathode humid temp=30oC

100% excess flow rate

Current(A)

0 10 20 30 40

Vol

tage

(V)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

4-Serpentine Interdigitated Dual inlet single outlet

Type of channel


150% excess flow rate

Current(A)

0 10 20 30 40

Volt

age(

V)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


Type of flow channel


without backpressure

Current(A)

0 10 20 30 40

Pow

er(W

)

0

2

4

6

8

10

12

14

16

18


Type of channel

Effect of Back pressure

12 in H20 backpressure

Current(A)

0 10 20 30 40

Pow

er(W

)

0

2

4

6

8

10

12

14

16

18

20

4-Serpentine Dual inlet single outlet Interdigitated

Type of channel

Effect of Back pressure

Hysteresis study fig

Dual inlet single outlet flow channel

Current(A)

0 5 10 15 20 25 30

Volt

age(V

)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

forwardbackward

Pressure =1atm, O2 flow rate =0.36lpm, H2 flow rate=0.32lpmCell and anode humid temp=40oC ,Cathode humid temp=35oC

Conclusions As the oxygen flow rate is increased, there is an increase in the cell

voltage due to maintaining sufficient oxygen on the cathode catalyst surface and carryover of water by oxygen.

When the flow rate is doubled (0.2 to 0.4 lpm) a 10% increase is found in power output (17.7 to 19.4W).

Under identical operating conditions, at 25A current the fuel cell gives the highest voltage with 4-serpentine flow field plates (0.6V). The interdigitated and dual-inlet-single-outlet flow geometries occupy the second and third positions (0.48 and 0.4V) respectively in the performance.

The 4-serpentine and dual inlet and single outlet flow channels show improvement in overall performance and power with an increase in back pressure.

References:1. Hawang,J.J. , Hawang,H.S. (2002).Parametric studies of a double-cell stack of

PEMFC using GrafoilTM flow-field plates. Journal of Power Sources, 104:24-32.

2. Wang.L., Husar,A. , Zhou.T, Liu,H. (2003). A Parametric study of PEM fuel cells performances. International Journal of Hydrogen Energy, 28: 1263-1272.

3. Wang,L., Liu,H. (2004). Performance studies of PEM fuel cells with interdigitated flow field. Journal of Power Sources, 134: 185–196.

4. Hermann,A., Chaudhuri,T., Spagnol,P. (2005), Bipolar plates for PEM fuel cells: A review. International Journal of Hydrogen Energy, 30,12: 1297-1302.

5. Yan,W.M., Yang,C.H., Soong,C.H., Chen,F., Mei,S.C. (2006). Experimental studies on optimal operating conditions for different flow field designs of PEM fuel cells. Journal of Power Sources, 160: 284-292.

6. Maher A.R. Sadiq Al-Baghdad and Haroun A.K Shahad Al-Janabi, (2007). Influence of the design parameters in a proton exchange membrane (PEM) fuel cell on mechanical behavior of the polymer membrane. Energy & Fuels, 21: 2258-2267.

7. Wang, X.D., Duan,Y.Y., Yan,W.M., Peng,X.F. (2008). Local transport phenomena and cell performance of PEM fuel cells with various serpentine flow field designs. Journal of Power Sources, 175:397-407.

8. Kuo, J.K., Yen, T.S., Chen, C.K. (2008). Improvement of performance of gas flow channel in PEM fuel cells. Energy Conversion and Management, 49, 10: 2776-2787.

9. Jeon, D.H., Greenway,S, Shimpalee,S., Van Zee, J.W. (2008). The effect of serpentine flow-field designs on PEM fuel cell performance. International Journal of Hydrogen Energy, 33, 3:1052-1066.

10. Kloess, J.P., (2009). Investigation of bio-inspired flow channel designs for bipolar plates in proton exchange membrane fuel cells, Journal of Power Sources, 188,pp. 132-140.

11. Hamilton,P.J. and Pollet,B.G. (2010). Polymer Electrolyte Membrane Fuel Cell (PEMFC) Flow Field Plate: Design, Materials and Characterisation. Fuel Cells, 10,4: 489-509.

27

THANK YOU

171 sreenivasulu

Technology

Transcript of 171 sreenivasulu