k. sundmacher: electrochemical energy conversion using fuel cell systems ntnu, 29 june 2007 1...
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NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 1
Electrochemical Energy Conversion using Fuel Cell Systems
Kai Sundmacher1,2
1 Max-Planck-Institute for Dynamics of Complex Technical Systems, Magdeburg2 Otto von Guericke University Magdeburg, Process Systems Engineering
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 2
Research Institutes at Magdeburg/Germany
Otto von Guericke University Magdeburg (11.000 students)
Max Planck Institute for Dynamics of ComplexTechnical Systems 1998 started 4 departments ~ 200 employees
Fraunhofer Institute forFactory Operation and Automation
Experimental Factory
EnvironmentalResearch Center
(UFZ)
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 3
World Energy Demand
• Strongly increasing energy demand, particularly in Asia
• Dependence of many countries on limited fossile resources
economic impact:increasing costs for energy „harvesting“ and transport political impact:fair distribution of resources
• Emissions local: air polution
global: climate change
Ref.: IEA (International Energy Agency) World Energy Outlook 2002 – Forecast of world energy consumption until 2020.
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 4
Solution Strategies
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Geothermal• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 5
Solution Strategies
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Earth heat• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
…how can Fuel Cellscontribute?
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 6
Solution Strategies: The Role of Fuel Cells
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Earth heat• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
More efficient production of
electrical energy!
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 7
Solution Strategies: The Role of Fuel Cells
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Earth heat• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
Direct conversion of primary energy at
the site of consumption!
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 8
Solution Strategies: The Role of Fuel Cells
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Earth heat• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
Fuel Cells ideally suited for
combined cycles!
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 9
Solution Strategies: The Role of Fuel Cells
Classical Energy Carriers Renewable Resources
Need for higher efficienciesGeneration
Distribution
Consumption
Dispersed power systems:+ lower losses+ combined cycles+ higher net stability- net operation difficult
• Sun• Wind• Water Flow• Earth heat• Biomass
Balancing Availability and Demand in Time and Space
Intelligent energy storage and transport
Fuel cells are key component in future hydrogen economy!
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 10
Working Principle of H2-O2 Fuel Cell (PEMFC)
PEM
PorousAnode
PorousCathode
Electrolyte
Hydrogen
Polymer Electrolyte Membrane Air
Bipolar Plate
Gas Diffusion Layer
Catalyst Layer
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 11
Fuel Cell Stack
Ucell = 0,5 - 0.9 V
Stacking N cells in series leads to higher voltages.
Larger cross sectional area A leads to higher currents:
+
- +
-
-
-
-+
+
+UStack = N · Ucell
Stack by ZSW, GermanyElectrical Power: 1 kW
ca. 350 mm
100 mm
100 mm
Stack
Single Cell
A IStack = Icell = A · icell,av
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 12
Outline
Introduction
Solid Oxide Fuel Cell: SOFC
Molten Carbonate Fuel Cell: MCFC
Proton Exchange Membrane Fuel Cell: PEMFC
Enzymatic Fuel Cell
Summary
1000 °C
600 °C
80 °C
37 °C
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 13
Working Principle of MCFC
T = 580 - 650 °C
Anode
CO32-
Cathode½O2+CO2+2e-CO3
2-
(CH4)(H2)(CO)CO2
H2O
O2
CO2
ExchaustAir
Electrolyte
e-
CH4
H2O
Ucell
H2 + CO32- H2O + CO2 +2e-
CO + CO32- 2CO2+2e-
O2
N2
(Air)
CatalyticCombustion
CH4 + H2O CO + 3H2
CO + H2O CO2 + H2
(N2)(H2O)
Internal Reforming Anode:Ni-10% Cr3 – 6 m Pores60 % Porosity1 mm Thickness
Cathode:NiO7 – 15 m Pores
Electrolyte Matrix:-LiAlO2/-Al2O3
0,5 mm Thickness
Electrolyte:62% Li2CO3
38% K2CO3
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 14
250 kW MCFC Fuel Cell Plant “HotModule”
HotModule System being installed atthe University Hospital in Magdeburg• Molten Carbonate Fuel Cell: MCFC• 342 Cells, 250 kW Electrical Power• ca. 48% Electrical Efficiency• Feed Gas: Natural Gas• Size (L x W x H): 7,3 m x 2,5 m x 3,2 m• Mass 15 t
Developed by: MTU CFC Solutions, Germany
N2 / O2
ExhaustAir
StainlessSteal Vessel
Electrical.Heater
CatalyticCom-bustion
Feed Gas CH4 / H2O
CO2 / O2
Fresh AirN2 / O2
MixingChamber
GasDistributor
FC Stack
Fan
4 / H2O
CO2 / O2
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 15
System Features:• 3-dimensional cell stack• Cross-flow operation• External recycles
0.8 m
1.2
m
2.5 m ; 342 Cells
MCFC Fuel Cell “HotModule”
Catalytic Com-
bustion
Anode Feed
Cathode Feed
Anode Effluent
Exhaust Air Cathode Gas Recycle
CathodeEffluent
Fresh AirSupply
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 16
2D Model of MCFC Fuel Cell “HotModule”
Enthalpy and Mass Balances of Gas Phases
,,
,,
,,0
Enthalpy Balance in Solid Phase
,,2
2
ssss
Charge Balances at Electrolyte
,, saii
cell
A
IdAi
Conductive heat transport,parabolic PDE
Convective mass transport,hyperbolic PDE
Convective energy transport,hyperbolic PDE
Total mass balance,ODE in space
Local charge balance,ODE in time
Galvanostatic condition,Integral equation
Number
17 PDE, 4 ODE, 1 IE
2x7=14 PDE
2x1=2 PDE
2x1=2 ODE
1 PDE
2x1= 2 ODE
1 IE
K. Chudej, P. Heidebrecht, V. Petzet, S. Scherdel, K. Schittkowski, H.J. Pesch, K. Sundmacher, ZAMM 85 (2005) 132-140.
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 17
Steady State MCFC Simulation ResultsAverage Current Density: 125 mA/cm²; S/C = 2.5; Fuel Utilization: 70%
P. Heidebrecht, K. Sundmacher, Journal of the Electrochemical Society 152, 2005, A2217-2228.
Current Density
Hydrogen at Anode
Temperature at Cathode
AnodeFeed
CathodeFeed
CH4 / H
2O O
2 / CO
2
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 18
Dynamic Response to Load Change
0.85Icell
0.7
step=0.1
=500
P. Heidebrecht, K. Sundmacher, Journal of the Electrochemical Society 152, 2005, A2217-2228.
DoubleLayerCharging
Mass Transfer toElectrodes
Heat Transportin SolidParts
Time, - step
Cel
l Vol
tage
, U
cell
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 19
Model-based Observer
Measurable: cell voltage, gas exit temperatures, gas exit compositions
Desirable for process control and monitoring: Information on internal temperatures and gas compositions very difficult to measure!
Solution:
Observer / State Estimator
?
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 20
Model-based Observer
RealProcess
Inputs u
MCFC Sensoreny
States x
Sensor Modelsxx
!
)x(hy y
Outputs y
?
MCFC ModelObserver
Observer Correction
yyk
)(x)(x
+
-
messt
,x,xf
x
z
t
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 21
• Experimental results: Estimation Experimental Data
Experimental Information for Filter Correction
Good Filter Convergence
Experimental Information for Filter Validation
Good Precision of State Estimation
Model-based Observer
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 22
Outline
Introduction
Solid Oxide Fuel Cell: SOFC
Molten Carbonate Fuel Cell: MCFC
Proton Exchange Membrane Fuel Cell: PEMFC
Enzymatic Fuel Cell
Summary
1000 °C
600 °C
80 °C
37 °C
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 23
SOFC: Candidate for Steady State Power Plants
SOFC: Solid Oxide Fuel CellElectrolyte: Solid Oxide Ceramics (YSZ)Effectiveness: 55 – 65 %Temperature: 800 - 1000 °CFuture Use: Power plants for kW - GW range
AnodeSolid OxideCathode
Fuel Gas
AirSource: Siemens-Westinghouse, www.powergeneration.siemens.com/en/fuelcells
Gas Feed
Electrical Switches
Electrolyte
Anode
Cathode
CathodeContactors
DC/AC Converter
USV
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 24
Temperature Effects in Electrical Conductors
Metallic Conductor • Charge transport by electrons• Electrical conductivity decreases at
increasing temperature• If local temperature increases:
local current density decreases local heat production decreases
(Ohmic losses) self-stabilizing effect
Oxygen Ion Conductor (Fuel Cell)• Charge transport by ions• Electrical conductivity increases at
increasing temperature • If local temperature increases:
local current density increases local heat production increases (Ohmic losses + reaction heat) de-stabilizing effect
+
-current density
-
+current density
Mangold, M., Krasnyk, K., Sundmacher, K., Chemical Engineering Science 59 (2004) 4869 - 4877
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 25
Simple 1D Model for SOFC
Model asumptions: 1D approach (gradients only in y-direction) Heat transport via heat conduction (Fourier’s law) Concentration polarization neglected Infinitely high electrical conductivity of electrodes Arrhenius-type temperature dependence of electrical conductivity
Mangold, M., Krasnyk, K., Sundmacher, K., Chemical Engineering Science 59 (2004) 4869 - 4877
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 26
SOFC: Dimensionsless Model Equations
• Energy balance:
12
2
BiiUiB cell
• Boundary conditions: ),(Bi,
02
0
),(Bi,
12
1
1
exp1
)1(exp1
exp/
///
///CA
eqCACAeq
CAeqCACACA Ki
• Electrochemical kinetics at anode and cathode:
• Ohm’s law for ion transport in electrolyte:
totCAEE expi
1
• Overall charge balance for electrodes: 1
0
diI tot Arrhenius term
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 27
SOFC: Phase Portrait at Ucell = const.
Solutions for a fuel cell of infinite length:
Periodic solutions along space coordinate possible!
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 28
left boundary:
),0(20
Bi
right boundary:
),0(20
Bi
SOFC: Phase Portrait at Ucell = const.
Solutions for a fuel cell of finite length:
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 29
SOFC: Current Instabilities at Icell = const.
Mangold, M., Krasnyk, K., Sundmacher, K., Chemical Engineering Science 59 (2004) 4869 - 4877
E1 E
2>E1
E3>E
2
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 30
Outline
Introduction
Solid Oxide Fuel Cell: SOFC
Molten Carbonate Fuel Cell: MCFC
Proton Exchange Membrane Fuel Cell: PEMFC
Enzymatic Fuel Cell
Summary
1000 °C
600 °C
80 °C
37 °C
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 31
PEMFC: Use in Mobile Applications
PEMFC: Polymer Electrolyte Membrane Fuel Cell
Electrolyte: Polymeric Membrane as Ion Conductor
Efficiency: 30 - 50%
Temperature: 20 - 100 °C (Goal: 180 °C)
Use: Cars, portable devices, battery substitute
H+
O2
e-
AnodePEM Cathode
H2
H2O
Source: Adam Opel AG Opel HydroGen 3 (2001) H2-operation, 150 km/h, 400 km distance
Problem: Membrane Water Management
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 32
PEMFC: Multiple Steady Operating States
PEM Fuel Cell:
inOHOHsat
OHOHREM papa ,2222
)(
car
aa
OHL
OHOH
PROD
)(
)()(
2
2
2
Water production curve:
Water removal line:
H2 + ½ O2 H2O
Water activity in membrane, aH2O
Map of Operating Modi
Hanke, Mangold, KS, Fuel Cells 5 (2005) 133Hanke-Rauschenbach, Mangold, KS, JPS (2006) in prep.
Hydrogen Feed Flow
Gas Humidity
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 33
PEMFC: Nonlinear Operating Dynamics
R. Hanke-Rauschenbach, M. Mangold, K. Sundmacher, JPS (2006) in prep.
R. Hanke-Rauschenbach, M. Mangold, K. Sundmacher, AIChE Meeting, San Francisco, 12-17 Nov. 2006.
Current Voltage Curve
Humidityreduction
Response behaviour at load variations
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 34
Outline
Introduction
Solid Oxide Fuel Cell: SOFC
Molten Carbonate Fuel Cell: MCFC
Proton Exchange Membrane Fuel Cell: PEMFC
Enzymatic Fuel Cell
Summary
1000 °C
600 °C
80 °C
37 °C
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 35
Enzymatic Fuel Cells: Possible Biomedical Applications
Hearing Devices
Neuro-Stimulators
ICD/CHF Devices LVAD Artificial Hearts
Pacemakers
Drug PumpsInsulin Pumps
Incontinence Devices
Bone Growth Stimulators Goal: Implantable fuel cell in the mW to W range
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 36
Redox Processes in Biology
OH
OH
OH
CH2OH
OH COOH
H2OO
OH
OH
CH2OH
OH
O
O2
FADH2FAD
O
OH
OH
CH2OH
OH
OH
H2O2
-D-glucose -gluconolactone gluconic acid
+2e-
+2H+
-2e-
-2H+
Oxidation
Reduction
FAD =
Flavin Adenin Dinucleotid
is a redox cofactor
of the enzyme
Glucose Oxidase
Glucose Oxidase, GOX
FAD
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 37
Enzymatic Fuel Cell: Working Principle
Ano
de
Cat
hode
H+
e- e-
glucose
gluconic acid
O2
H2O
enzymes
redox center
e-
Anode: C6H12O6
Cathode: ½ O2 + 2e- + 2H+
C6H10O6 + 2e- + 2H+ Oxidation E = - 0.5 V
H2O Reduction E = 0.7 V
Overall: C6H12O6 + ½ O2 C6H10O6 + H2O ΔE = 1.2 V
Voltage
Immobilisation
Electron transfer
ANODE
Current ~ Enzymes per Area
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 38
Immobilisation of Glucose Oxidase at Gold Electrode
SNH2
SNH2
S NH2
PQQS NH PQQ
H2N FAD
S NH PQQ NH FAD
apo-GOX
S NH PQQ NH FAD
e-
e-
glucose
gluconic acid
EDC, NHS EDC, NHS
Au
PQQ = Mediator: redox-active component for electron transfer between enzyme and electrode
N
O
O
HN
COOH
HOOC
HOOC
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 39
Enzyme Electrode: Proof of Principle with Glucose
S NH PQQ NH FAD
apo-GOX
S NH PQQ NH FAD
e-
e-
gluconic acid
glucose
Th
erm
od
yna
mic
po
ten
tia
l
On
set
po
ten
tia
l
Overpotential
NTNU, 29 June 2007 K. Sundmacher: Electrochemical Energy Conversion using Fuel Cell Systems 40
Summary: Important Trends in Fuel Cell Engineering
High temperature fuel cells: Molten Carbonate fuel cells (HotModule) are very close to the market Efficient co-production of electricity and heat Internal direct reforming (DIR) is most attractive process variant
Low temperature fuel cells: PEMFC: Problem of water management in membranes Development of water-free membranes for mobile applications
Enzymatic fuel cells: Biomedical applications: interdisciplinary collaboration between
chemical engineering, electrochemistry and organic chemistry necessary