Download - PEM Fuel Cell Simulation on Hysys Platform
PEM Fuel Cell – A case Study in Hysis Platform
Vinay K Sachan & Subhasish MitraDepartment of Chemical EngineeringIIT Kanpur
Motivation:
� Faster depletion of fossil fuels coupled with global warming issue.
� Hydrogen appears to be the most promising fuel which is inherently clean & green.
� With changing demands, distributed hydrogen economy is envisaged.
� Fuel cell drawing attention in various application areas e.g. micro-power, auxiliary power, transportation power, stationary power etc. as an efficient device for utilizing hydrogen potential.
Fuel Cell Principle:
� First demonstrated in principle by British Scientist Sir Willliam Robert Grove in 1839. The invention was based on idea of reverse electrolysis.
� In general, a fuel cell consists of two electrodes -Anode and Cathode.
� Hydrogen and Oxygen are fed into the cell.
� Catalyst at Anode causes hydrogen atoms to give up electrons leaving positively charged protons.
� Oxygen ions at Cathode side attract the hydrogen protons.
� Protons pass through electrolyte membrane.
� Electrons are redirected to Cathode through external circuit.
� This leads to production of electrical power.
Fuel Cell Principle (Contd.):
Fuel Cell Working Mechanism:
Fuel Processor: [1]
[1]. Simulation study of a PEM fuel cell system with autothermal reforming, Atilla Ersoz, Hayati Olgun, Sibel Ozdogan, Energy 31 (2006), 1490 - 1500
Catalyst:
ATR: PdO on Al2O3/CeO2
HTS : Fe/Cr
LTS : Cu/Zn/Al
PROX : Ru/Pt
Simulation Flow Sheet Data: [1]
[1]. Simulation study of a PEM fuel cell system with autothermal reforming, Atilla Ersoz, Hayati Olgun, Sibel Ozdogan, Energy 31 (2006), 1490 - 1500
Active cell areais 400 cm2
Simulation Flow Sheet Data: [1]
[1]. Simulation study of a PEM fuel cell system with autothermal reforming, Atilla Ersoz, Hayati Olgun, Sibel Ozdogan, Energy 31 (2006), 1490 - 1500
P1,P2,P3: Pumps, AC : Air Compressor, E : Power Turbine, HE : Heat Recovery Hx, COM : Combustor, C : Exhaust Stack
Modeling Strategy:
Process Simulator:
Hysis Version: 2006
Thermodynamic model:
Vapor phase : Peng-Robinson EOS (suitable for hydrocarbons)
Unit operations:
ATR, HTS, LTS, Combustor : Gibbs reactor
PROX, Fuel Cell Cathode : Conversion Reactor
Fuel Cell Anode : Separator
Fuel Processor Plant Simulation Diagram:
PEM Fuel Cell
Fuel Cell Cooling Unit
CO clean up section
Heat recovery-I
Heat recovery-II
Feed section
PEM Fuel Cell Simulation Diagram:
Anode block
Cooling loop
Cathode block
Combustor block
System Efficiency Calculations: [1]
[1]. Simulation study of a PEM fuel cell system with autothermal reforming, Atilla Ersoz, Hayati Olgun, Sibel Ozdogan, Energy 31 (2006), 1490 - 1500
Fuel Cell Polarization Curve:
Generalized polarization curve for a fuel cell
showing regions dominated by various types
of losses.
The single cell polarization curve taken for calculation.
[1]. Simulation study of a PEM fuel cell system with autothermal reforming, Atilla Ersoz, Hayati Olgun, Sibel Ozdogan, Energy 31 (2006), 1490 - 1500
Fuel Cell Polarization Curve – Curve Fitting:
PEM fuel cell characteristics y = -9E-10x3 + 2E-05x2 - 0.1076x + 1006.4
R2 = 0.9921
0
200
400
600
800
1000
1200
0 2000 4000 6000 8000 10000 12000
Current density (A/m2)
Cell V
olt
ag
e (
mV
)
A third order polynomial is fitted to describe cell voltage and current density relationship.
Overall System Efficiency Comparison:
•Total energy generated (PEMFC + Power Turbine) by the system is 100 Kw – claimed in the reference [1]
•PEMFC power calculation as a function of H2 generated not shown.
• PEMFC power (Pcell) is calculated using the following reference [2]
Pcell = Molar flow rate of H2 X LHV of H2 X electrochemical efficiency
Using this with electrochemical efficiency 0.6
Pcell : 54.21 kW , Ppower turbine : 16 kW, Total energy : 70.21 kW
Global system efficiency : 0.2473
[2]. L. Salemme, L. Menna, M. Simeone, Analysis of energy efficiency of innovative ATR based PEM fuel cell system with hydrogen membrane separation, International journal of hydrogen energy 34(2009) 6384-6392.
Pe : Power generated by the fuel cell system
Pa : Auxiliary power consumption
Molar flow rate & LHV will be for liquid fuel instead of CH4
Section Wise System Efficiency Comparison:
0.38160.3447
0.55840.5016
0.76870.7355
0.78060.744
0.80160.7453
0.80720.762
0.7680.771
Simulated - efficiencyRef-efficiencySection
1000No of cells
0.36570.3447
0.53520.4346
0.76870.7355
0.78060.744
0.80160.7453
0.80720.762
0.7680.771
Simulated - efficiencyRef-efficiencySection
500No of cells
0.37220.3447
0.54470.4846
0.76870.7355
0.78060.744
0.80160.7453
0.80720.762
0.7680.771
Simulated - efficiencyRef-efficiencySection
750No of cells
0.38940.3687
0.56990.5176
0.76870.7355
0.78060.744
0.80160.7453
0.80720.762
0.7680.771
Simulated - efficiencyRef-efficiencySection
1250No of cells
System Efficiency Comparison:
Comparison of system efficiency - No of Cells 500
0
0.2
0.4
0.6
0.8
1
1 2 3 4 5 6 7
System section
Eff
icie
ncy
Ref-efficiency
Simulated efficiency
Comparison of system efficiency - No of Cells 750
0
0.2
0.4
0.6
0.8
1
1 2 3 4 5 6 7
System section
Eff
icie
ncy
Ref-efficiency
Simulated efficiency
Comparison of system efficiency
- No of Cells 1000
0
0.2
0.4
0.6
0.8
1
1 2 3 4 5 6 7
System section
Eff
icie
ncy
Ref-efficiency
Simulated efficiency
Comparison of system efficiency
- No of Cells 1250
0
0.2
0.4
0.6
0.8
1
1 2 3 4 5 6 7
System section
Eff
icie
ncy
Ref-efficiency
Simulated efficiency
Efficiency : Ratio of outlet & inlet heat content in a section.
Section 1:Liquid fuel, Section 2: ATR, Section 3: HTS, Section 4: LTS, Section 5: PROX
System Power Consumption Comparison:
1600016700Expander (E)
1518015430Air Compr (AC)
5.885.87Water pump (P2)
200.4210Cooling loop pump (P3)
3.684.3Liquid fuel (P1)
Power (W) (Simulated)
Power (W) (Reference)
Power Consumption/Generation
Source
Stack Voltage Efficiency Comparison:
0.7120.6461250
0.6980.6261000
0.6810.605750
0.6690.542500
Simulated - efficiencyRef-efficiencyNo of cells
Stack voltage
efficiency
Comparison of stack voltage efficiency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 500 1000 1500
No of cells in stack
Eff
icie
nc
y
Ref-efficiency
Simulated efficiency
Higher simulated values obtained due to
•Probable error in fitting voltage/current density curve
•Mismatch in Fuel Cell feed flow rate. (Reference: 6 kmol/hr, Sim:8.385 kmol/hr)
Wind up:
� Fairly close agreement is obtained between simulated and reference efficiencies of various section of the fuel cell system.
� Fairly close agreement is obtained between simulated and reference power consumptions in various sections of the fuel cell system.
� Stack voltage efficiency is observed to increase with number of cells in the stack. Simulated stack voltage efficiency is found to be on higher side than reference values.
� The obtained net electrical efficiency (7) varies in the range of 34% – 37% which is comparable with the conventional gasoline based IC engine.
� To make fuel cell more appealing, volume & mass of reformer system need to be compact by material & catalyst improvement .
Thanks
for
your attention!