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© Fraunhofer ISE
Review Lecture – Session HP.3d
PEM Water Electrolysis - Present Status of Research and Development
Tom SmolinkaFraunhofer-Institut für Solare Energiesysteme ISE
18th World Hydrogen Energy Conference 2010Essen, May 18, 2010
© Fraunhofer ISE
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Agenda
Background of PEM water electrolysis activities at Fraunhofer ISE
Fundamental of PEM water electrolysis
Electrodes and Membrane Electrode Assembly
Cell design and stack construction
System layout and efficiencies
Comparison to alkaline water electrolyser(Conclusion and summary)
© Fraunhofer ISE
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The Self-sufficient Solar House in Freiburg …
… begin of R&D activities in PEM electrolysis at Fraunhofer ISE
First developments in the eighties
Field test: 1992-1995
Complete hydrogen storage system consisting of:
PEM electrolyser
(30 bar / 2 kWel)
H2 and O2 pressure tanks
PEM fuel cell
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Regenerative fuel cell:
PEM electrolysis unit
(30 bar / 2 kWel)
H2/O2 storage tanks
PEM fuel cell
No mech. compressor!
The Self-sufficient Solar House in Freiburg …
ElectricityGasHeat
Warmwater
PV panel
Electrolyser Battery FuelCell
DC Load
Storagetanks
Inverter AC load
Cooking
Heating
Ther
mal
usa
ge
Elec
tric
alu
sag
e
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For more than 20 years experience in PEM electrolysis
Material characterisation
Cell and stack design
Balance of plant
Control strategies
Power electronics
Integration with RES
System evaluation
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Schematic of a PEM electrolysis cell
cathode anode
membrane
currentdistributor
electrode(electrocatalysts)
flow fieldplate
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cathode anode
H2 0.5 O2
H2O
H+
Schematic of a PEM electrolysis cell
Anode reaction:
H2O → 0.5 O2 + 2H+ +2e-
Cathode reaction:
2H+ + 2e- → H2
Total reaction:
H2O → H2 + 0.5 O2
Vrev = 1.23 V @ STP
endothermal reaction
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Decomposition of water
100
125
150
175
200
225
250
275
300
200 400 600 800 1000 1200
Temperature [K]
Enth
alpy
of R
eact
ion
[kJ
mol
-1]
Free
Ene
rgy
of R
eact
ion
[kJ
mol
-1]
0.52
0.65
0.78
0.91
1.04
1.17
1.30
1.43
1.56
Theo
retic
al C
ell V
olta
ge [V
]ΔHR ~ Vth
H2O(l) H2O(g)
ΔGR ~ Vrev
1.0
1.2
1.4
1.6
1.8
2.0
0 200 400 600 800 1000Current Density [mA cm-2]
Cel
l Vol
tage
[V]
iR A
η An
η Cath
V rev
Thermodynamics:
Reversible losses
HHV: 3.54 kWh/Nm³ H2
Reaction kinetics:
Irreversible losses
Overpotentials and internal resistance
Cell voltage affected by temperature and pressure
© Fraunhofer ISE
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The core component: Membrane Electrode Assembly
Cross Section of a MEA (Fraunhofer ISE) and reinforecd DMS membrane (Giner)
Membrane
Thickness: 100 - 300 μm (e.g. Nafion 117)
Coated on both sides with catalysts
Reinforcement possible
Cathode
Loading: 1.0 – 2.0 mg/cm²
Pt black or Pt/C based
Anode
Loading: 1.0 – 4.0 mg/cm²
Mostly Ir, Ru, Pt, (oxide) based
~180 μm
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Performance of a PEM electrolysis cell
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
Vol
tage
[V]
Current density [A/cm²]
80°C 60°C 40°C 20°C
Influence of cell temperature
V/I characteristics of a standard Nafion based MEA from SolviCoremeasured in a 25 cm² laboratory electrolysis cell (Fraunhofer ISE)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
50 bar 40 bar 30 bar 20 bar 10 bar
Vol
tage
[V]
Current density [A/cm²]
Influence of cell pressure
@ 1 atm @ 80°C
pressure
tempe-rature
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1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
0.0 0.2 0.4 0.6 0.8 1.0Current density [A/cm²]
Cel
l vol
tage
[V]
Pt / SPE / (Ir5Ru1)Ox
Pt / SPE / Ir
Optimised MEAs Metal(M)
Ir1Ru2OxM0.1 Fe
Ir1Ru2OxM0.1 Ni
Ir1Ru2OxM0.1 Co
Ir1Ru2OxM0.1 Sn
Alternative catalysts for the anode
V/i characteristic @ 80°C / 1 atm, cathode: Pt black (Fraunhofer ISE)
),(),(
pTVpTV
OP
HHV=ε
Cell efficiency:
82%
89%
93%
Efficiencies > 95% at 1000 mA/cm²reported in literature
© Fraunhofer ISE
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Current collectors/distributors
Challenge:
Porous, electrically conductive and corrosion-resistant material
Solution:
Sintered Ti powder (a)
Sintered Ti felt (b)
Expanded Ti mesh (c)
Carbon-based paper (d)
a) b)
d)c)
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From cell design …
Corrosion-resistant materials
Titanium
Coated metals
Plastic-composite
Pressure-resistant cell design
Metal-cutting production
Frame construction
Die cutting
Metal-laminate
injection molded
Structured plates with applied gaskets (Hamilton Sunderstrand, Fraunhofer ISE)
30 bar 12 bar 145 bar
7 bar 14 bar
© Fraunhofer ISE
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… to stack construction for PEM water electrolyser
Giner
Fraunhofer ISE
Helion
Fraunhofer ISE
Hydrogenics
h-tec
Fraunhofer ISE
Hamilton
Kurchatov
Filter press configuration
Pressure resistance: up to 207 bar
Active area: 10 – 750 cm²
Current density: up to 2.5 A/cm²
Cell voltage: max. 2.2 V
Number of cells: < 120
H2 production rate: 2 Nl/h – 30 Nm³/h
Power input per stack: up to 160 kWel (estimated)
Proton
© Fraunhofer ISE
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1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
0 5000 10000 15000 20000 25000
Mea
n C
ell V
olta
ge (V
)
Cumulative Time (hours)
On‐going testing
Long-term performance of PEM electrolysis stacks
Typical stack life time
5,000 - 20,000 h in a system
Stack replacement: every 5 - 9 years
In military applications up to 100,000 h reported
Hydrogenics 91E13 cells stackoperating @ 2 A/cm²
Hydrogenics 91E stack
© Fraunhofer ISE
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PEM electrolysis system = stack + balance of plant
Pressure balanced system:
O2 and H2 side operates at same pressure
Differential pressure system:
Only hydrogen side is pressurised
Cell/stack design is more sophisticated
BoP more simple and less expansive
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Commercial PEM electrolyser
Schmidlin Proton FuMA-Tech ITM Power Hydrogenics Proton Claind Proton Statoil Treadwell
Compared to alkaline systems low H2 production rates:
100 Nml/min – 15 Nm³/h today
Up to 30 Nm³/h in the near future
H2 output at 6 – 30 bar and purified up to 6.0
Applications:
Laboratory equipment (e.g. gas chromatography)
Generator cooling in power plants
Float glas manufacturing and further industrial processes (food industry)
Military (submarines) and space
© Fraunhofer ISE
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How efficent are PEM electrolysers?
Prefered measure: specific power consump-tion in kWh/Nm³ H2
High efficiencies on stack level
Moderate efficiencies on system level(low H2 production rates)
2
4
6
8
10
0.1 1.0 10.0 100.0
Hydrogen Production Rate [Nm3 h-1]
Pow
er C
onsu
mpt
ion
[kW
h N
m-3
H2]
systems
stacks
© Fraunhofer ISE
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Comparison of alkaline and PEM electrolysers
Comparable young technology, still high potential for further improvement
Principle advantages:
Simple system configuration
Very high current and power densities
High efficiencies on cell level
Very fast response time, suitable for coupling with RES
Usage of expensive materials (membrane, electrodes, bipolar plates)
Attractive competitive position for small electrolysis units << 100 Nm³/h
How large will PEM electrolysers become in the next 10 years??
Small footprint
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Comparison of alkaline and PEM electrolysers
AEL PEMELCurrent density
Power density
Efficiency (system)
System complexity
Durability / Life cycle
Investment costs
- +
-- +
+ o
- o
++ o
o -
today
AEL PEMELo ++
- ++
+ +
- o
++ +
o o
in the future
© Fraunhofer ISE
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Manufacturer of water electrolyser
Alcaline Electrolysis PEM-Electrolysis
R&D
Com-mer-
cial
This figure does not claim to be exhaustive!
Manufacturer of water electrolysers - Who is on the road?
© Fraunhofer ISE
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NEXPEL main objective: Develop and demonstrate a PEM water electrolyser integrated with RES:
75% Efficiency (LHV), H2 production cost ~ €5,000 / Nm3h‐1, target lifetime of 40,000 h
New membrane materials
New catalysts Improved MEAs
Novel stack design and new construction materials
Improved DC‐DC converter
Jan 2010 ‐ Dec 2012Co‐ordination: SINTEF
Funding: Fuel Cells and Hydrogen JUTotal Budget: € 3,353,549
www.nexpel.eu
© Fraunhofer ISE
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Thank you for your kind attention!
Tom Smolinka
Fraunhofer ISE
Heidenhofstr. 2 / 79110 Freiburg / Germany
Ph: +49 761 4588 5212
www.ise.fraunhofer.de
Questions?