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01 October 2013 Jürgen Mergel
IEK-3: Electrochemical Process Engineering
Hydrogen Production by Water Electrolysis:
Current Status and Future Trends
IEK-3: Electrochemical Process Engineering 2
Outline
Introduction
Water electrolysis technologies
Alkaline water electrolysis
PEM electrolysis
Requirements for electrolysis by coupling with renewable
energies
Challenges for further development
Summary
IEK-3: Electrochemical Process Engineering 4
Functional principle of water electrolysis
Cathode -
½ O2H+H2
PEM-Elektrolysis20 – 100 °C
H2O 2H+
+ ½ O2 + 2e- Anode
2H+
+ 2e- H2 Cathode
H2O H2 + ½ O2 Total reaction
+ Anode
AnodeIr
CathodePt
Membrane
Cathode -
½ O2O2-H2
High-Temperature-Elektrolysis700 – 1000 °C
O2- ½ O2 + 2e- Anode
H2O + 2e- H2 + O2- Cathode
H2O H2 + ½ O2 Total reaction
+ Anode
AnodeCathode
O2– Ion conductor
Source: Proton OnSite Source: ELT Source: Ceramatec
IEK-3: Electrochemical Process Engineering 5
Water electrolysis - State of the art
Specification Alkaline electrolysis PEM electrolysis
Cell temperature 60 – 80 °C 50 – 80 °C
Pressure ≤ 32 bar < 30 bar
Current density 0.2 – 0.4 A/cm² 0.6 – 2.0 A/cm²
Cell voltage 1.8 – 2.4 V 1.8 – 2.2 V
Cell voltage efficiency* 52 – 69 % 57 – 69 %
Spec. energy consumption stack 4.2 – 5.9 kWh/Nm³ 4.2 – 5.6 kWh/Nm³
Spec. energy consumption system 4.5 – 7.0 kWh/Nm³ 4.5 – 7.5 kWh/Nm³
Load range 20 – 130 % 5 – 300 %
Cell area ≤ 4 m² ≤ 300 cm²
H2 production rate per stack/system ≤ 760 Nm³/h up to 10 Nm³/h / 30 Nm³/h
Lifetime stack < 90,000 h < 60,000 h
Lifetime system incl. maintenance 20 – 30 a 10 – 20 a
Source: NOW-Studie ‚Stand und Entwicklungspotenzial der Wasserelektrolyse zur Herstellung von Wasserstoff aus regenerativen Energien‘, 2011
*relating to LHV: 1.23 V
IEK-3: Electrochemical Process Engineering 6
Water electrolysis - Overview of leading manufacturers of alkaline electrolyzers
Manufacturer Series/operating
pressure
H2 rate
Nm³ h-1
Energy
consumption
kWh Nm-³H2
Load range
%
Hydrogenics HYSTAT /
10 – 25 bar
10 - 75
max.18/stack 5.2 - 5.4 (system)
40 - 100
5 - 120 (optional)
ENERTRAG HyTec
Take over by McPhy
Energy (1 Oct 2013)
NDE-15, NDE-30 / atm.
HDE-05-100/200
10 – 60 bar
185 – 450
100 – 200
4.48 (system)
< 4.75 (system)
20 – 100
25 - 130
Teledyne Energy
Systems
TITAN HM / 10 bar
TITAN EC / 10 bar
2.8 – 12
28 - 56 no details no details
Wasserelektrolyse
Hydrotechnik
EV 01 – EV 150
atmospheric 1 - 250 no details 15 - 100
IEK-3: Electrochemical Process Engineering 7
Water electrolysis - Overview of leading manufacturers of PEM electrolyzers
Manufacturer Series/operating
pressure
H2 rate
Nm³ h-1
Energy
consumption
kWh Nm-³H2
Load range
%
Proton OnSite
HOGEN S / 14 bar
HOGEN H / 15−30 bar
HOGEN C / 30 bar
0.25 - 1.0
2 - 6
10 - 30
6.7
6.8 - 7.3
5.8 - 6.2
0 - 100
0 - 100
0 - 100
Giner Electroch.
Systems
High pressure / 85 bar
30 kW / 25 bar
3.7
5.6
5.4
5.4 no details
CET H2 E5 – E40 / 14 bar 5 - 240 5 no details
H-TEC Systems EL30 / 30 bar 0.3 - 40 5.0 - 5.5 0 - 100
Hydrogenics HyLYZER / 25 bar
GEN3 (1 MW) / 30 bar
1 - 2
250
4.9 (stack) 6.7 (system)
no details
0 – 100
0 - 150
ITM Power HPac, HCore, HBox,
HFuel 15 bar 0.6 - 35 4.8 - 5.0 (system) no details
Siemens 100 kW (300 kW peak)
50 bar ~ 20 - 50 no details 0 - 300
IEK-3: Electrochemical Process Engineering 8
Typical current-voltage characteristics and operating
ranges for alkaline and PEM electrolysis
Source: Mergel, J.; Carmo, M.; Fritz, D.L.: Status on Technologies for Hydrogen Production by Water Electrolysis, Transition to Renewable Energy Systems,
Eds.: D. Stolten, V. Scherer, Wiley-VCH, Weinheim (2013), 423 - 450
IEK-3: Electrochemical Process Engineering 9
PEM water electrolysis
Advantages:
Higher power densities
Higher efficiency
Good partial load toleration
Simpler system structure
Compact stack design allows high pressure
operation
Challenges:
Cost reduction by reduction or substitution of
noble metals and cost-intensive components
Increasing the long-term stability
Scale-up stack and peripherals
Source:
Proton OnSite Source: IHT
Comparison of alkaline and PEM water electrolysis
Alkaline water electrolysis
Advantages:
Well-established technology
No noble metal catalysts
High long-term stability
Units up to 750 Nm³/h (3.5 MW)
Relatively low investment costs
Challenges:
Increasing the current densities
Expanding the part-load capability
System size and complexity
Reduction of gas purification requirements
IEK-3: Electrochemical Process Engineering 10
Requirements for electrolysis by coupling with
renewable energy
2050:
179 GW
40 GW
110 TWh
IEK-3: Electrochemical Process Engineering 11
Requirements for electrolysis by coupling with
renewable energy
MW power range (~ 100 – 200 MW / 50 – 130 t/day)
Pressure operation for cavern storage
High dynamics of the stack and system
Stand-by operation
Frequent starting and stopping
Increased partial load and overload capability
IEK-3: Electrochemical Process Engineering 12
0 2 4 6 8 10
1,2
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
3,0
3,2
Toll of overload on efficiency for a single electrolyzer
Current density / Acm-²
Mean c
ell
voltage / V
200 %
300 %
100 %
(nominal load)
61.5 %
76.9 %
51.3 %
43.9 %
68.3 %
55.9 %
47.3 %
87.8 %
Effic
iency / L
HV
41.0 %
PEM electrolysis, 80 °C
Alkaline
electrolysis
Advanced PEM electrolysis*
* Giner, Inc., 2013 DOE Hydrogen Program Annual Merit Review Meeting
IEK-3: Electrochemical Process Engineering 13
Production costs for hydrogen*
Electricity price is the most important variable for the plant
gate cost of hydrogen
followed by electricity use (kWh/kg)
and then by production purchased capital cost
Investment cost and installed electrolysis capacity
PEM Electrolysis
Stack and BoPs dominate
system costs
CCM, current collectors and
bipolar plates dominate stack
costs
Anode: Ir, Ru, Pt, mixed
oxides (2 – 6 mg/cm²)
Cathode: Pt (1 – 2 mg/cm²)
Separator plates and current
collectors (Ti, coated with
PGM)
*Source: Current (2009) State-of-the-Art Hydrogen Production
Cost Estimate using Water Electrolysis, NREL, 2009
Source: Proton Onsite
IEK-3: Electrochemical Process Engineering 14
Investment cost and installed electrolysis capacity
PEM Electrolysis
Stack and BoPs dominate
system costs
CCM, current collectors and
bipolar plates dominate stack
costs
Anode: Ir, Ru, Pt, mixed
oxides (2 – 6 mg/cm²)
Cathode: Pt (1 – 2 mg/cm²)
Separator plates and current
collectors (Ti, coated with
PGM)
IEK-3: Electrochemical Process Engineering 15
PEM Electrolysis
Stack and BoPs dominate
system costs
CCM, current collectors and
bipolar plates dominate stack
costs
Anode: Ir, Ru, Pt, mixed
oxides (2 – 6 mg/cm²)
Cathode: Pt (1 – 2 mg/cm²)
Separator plates and current
collectors (Ti, coated with
PGM)
State-of-the-art (2013)
0,0 0,5 1,0 1,5 2,0
1,2
1,3
1,4
1,5
1,6
1,7
1,8
1,9
2,0
2,1
2,2
Ce
ll V
olta
ge
/ V
Current Density / A cm-2
80 °C
50 °C
Investment cost and installed electrolysis capacity
2.440
IEK-3: Electrochemical Process Engineering 16
Investment cost and installed electrolysis capacity
PEM Electrolysis
Approaches for cost reduction
Reduction and substitution of
noble metals
Anode: Ir, Ru ~ 0,6 mg/cm²
Cathode: Pt ~ 0,2 mg/cm²
Low-cost, long-life separator
plates and current collectors
Scale-up single cell > 1.000 cm²
Reduction of BOP capital cost
nominal load
nominal load
Current density /
Cell
voltage /
IEK-3: Electrochemical Process Engineering 17
Investment cost and installed electrolysis capacity
PEM Electrolysis
Approaches for cost reduction
Reduction and substitution of
noble metals
Anode: Ir, Ru ~ 0,6 mg/cm²
Cathode: Pt ~ 0,2 mg/cm²
Low-cost, long-life separator
plates and current collectors
Scale-up single cell > 1.000 cm²
Reduction of BOP capital cost
IEK-3: Electrochemical Process Engineering 18
Source: D. Fritz, M. Carmo, J. Mergel, D. Stolten, Modeling of a PEM electrolyzer for component design,
manuscript in preparation.
Challenges for further development - Overpotential losses
CCMs - Catalyst layers - Membrane
Endplates Separator plates Current collectors
IEK-3: Electrochemical Process Engineering 19
Challenges for further development - Alkaline water electrolysis
New electrocatalysts to decrease overpotentials and increase efficiency
New diaphragms to increase partial load and minimize ohmic losses
Enable alkaline water electrolysis for overload operation
Anode: Ni/Co/Fe
Cathode: Ni/C-Pt
Advanced (FZJ, 1979 – 2002)
conventional
IEK-3: Electrochemical Process Engineering 20
Challenges for further development - Alkaline water electrolysis
New electrocatalysts to decrease overpotentials and
increase efficiency
New diaphragms to increase partial load and minimize
ohmic losses
Enable alkaline water electrolysis for overload operation
1 MW Prototype (Lurgi/FZJ, 1994)
100 cells, 1.6 m diameter
200 Nm³ H2/h and 100 Nm³ O2/h
Nominal current 5000 A, nominal current density 3 kA/m²
spec. energy consumption (stack) 3.9 – 4.1 kWh/Nm³ H2 Source: Fortschrittliche Wasserelektrolyse, Lurgi,
Wasserstoff als Energieträger, Wasserstoff-
Statusseminar, Würzburg, 24. Oktober 1995
Current density
Sp
ec. en
erg
y c
on
su
mp
tio
n
Spec. energy consumption
IEK-3: Electrochemical Process Engineering 21
Challenges for further development - Alkaline water electrolysis
Specification Type NDE-30 Type HDE-05-200
Cell temperature 80 °C < 80 °C
Pressure atmospheric 10 … 60 bar
Spec. energy consumption < 4.48 kWh/Nm³ < 4,75 kWh/Nm³
Part-load range 20 % 25 %
H2 production rate max. 450 Nm³/h max. 200 Nm³/h
2 MW NDE stacks
Source: ENERTRAG HyTec
take over by on October 1, 2013
IEK-3: Electrochemical Process Engineering 22
Challenges for further development - PEM water electrolysis
Approaches for cost reduction
Reduction and substitution of noble metals
Anode: Ir, Ru ~ 0.6 mg/cm²
Cathode: Pt ~ 0.2 mg/cm²
Low-cost, long-life separator plates and current collectors
Scale-up single cell > 1000 cm²
Source: M. Carmo, D. Fritz, J. Mergel, D. Stolten
Int. J. Hydrogen Energy, 2013. 38(12): p. 4901-4934
IEK-3: Electrochemical Process Engineering 23
Challenges for further development - PEM water electrolysis
Approaches for cost reduction
Reduction and substitution of noble metals
Anode: Ir, Ru ~ 0.6 mg/cm²
Cathode: Pt ~ 0.2 mg/cm²
Low-cost, long-life separator plates and current collectors
Scale-up single cell > 1000 cm²
Source: M. Carmo, D. Fritz, J. Mergel, D. Stolten
Int. J. Hydrogen Energy, 2013. 38(12): p. 4901-4934
80 °C, Nafion112
IEK-3: Electrochemical Process Engineering 24
Challenges for further development - Cell efficiency vs. catalyst loading, Pt loading cathode, 80 °C, Nafion 117
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0
1,4
1,5
1,6
1,7
1,8
1,9
2,0
FZJ CCMs:
Loading cathode:
0.8 mgPt
cm-2
0.2 mgPt
cm-2
Anode:
2.25 mgIrcm
-2
2.25 mgIrcm
-2
Ce
ll vo
ltag
e /
V
Current Density / Acm-2
IEK-3: Electrochemical Process Engineering 25
Challenges for further development - Cell efficiency vs. temperature & membrane thickness
Nafion 117
°
IEK-3: Electrochemical Process Engineering 26
Challenges for further development - Cell efficiency vs. temperature & membrane thickness
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,51,4
1,6
1,8
2,0
2,2
30 oC - 0.75 Acm
-2
50 oC - 1.00 Acm
-2
70 oC - 1.28 Acm
-2
80 oC - 1.46 Acm
-2
Ce
ll vo
ltag
e /
V
Current Density / Acm-2
Increasing operating temperature
can improve membrane
conductivity and catalytic activity
Requirements:
Improve catalyst durability
Reduced gas permeation
Nafion 117
Cathode: 0.8 mgPt/cm²
Anode: 2.25 mgIr/cm²
IEK-3: Electrochemical Process Engineering 27
Challenges for further development - Cell efficiency vs. temperature & membrane thickness
Nafion 117
°
IEK-3: Electrochemical Process Engineering 28
Challenges for further development - Cell efficiency vs. temperature & membrane thickness
Nafion 115
°
IEK-3: Electrochemical Process Engineering 29
Challenges for further development - Cell efficiency vs. membrane thickness
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0
1,4
1,5
1,6
1,7
1,8
1,9
2,0
Nafion 117
Nafion 115
Nafion 112
Cell
voltage / V
Current density / Acm-2
ambient pressure, 80 °C
Decreasing membrane thickness
can improve voltage efficiency but
decreasing faraday efficiency
Nafion 117 – 1.00 Acm-2
Nafion 115 – 1.20 Acm-2
Nafion 112 – 1.85 Acm-2
IEK-3: Electrochemical Process Engineering 30
Challenges for further development - Cell efficiency vs. membrane thickness & pressure
80 °C
0,0 0,5 1,0 1,5 2,00,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
112
115
117
j (A/cm²)H
2 in
O2 (
%)
1bar
Gas diffusion losses are highly dependent on
membrane thickness, operating pressure and
temperature
Source: Pressurized PEM water electrolysis: Efficiency and gas crossover
M. Schalenbach, M. Carmo, D. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy (2013), article in press
IEK-3: Electrochemical Process Engineering 31
Challenges for further development - Stack efficiency vs. membrane thickness & pressure
80 °C
At low and moderate operating
pressures stack efficiency are
mostly dependent on iR-losses
Source: Pressurized PEM water electrolysis: Efficiency and gas crossover
M. Schalenbach, M. Carmo, D. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy (2013), article in press
IEK-3: Electrochemical Process Engineering 32
Challenges for further development - Stack efficiency vs. membrane thickness & pressure
Simulated anodic hydrogen content
in dependence of current density at
30 bar and balanced and differential
pressure
Simulated stack efficiency loss due to
crossover and ohmic losses at 30 bar
for balanced and differential pressure
Source: Pressurized PEM water electrolysis: Efficiency and gas crossover
M. Schalenbach, M. Carmo, D. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy (2013), article in press
Faraday efficiency losses are
lower in differential-pressure
operation
Highly dependent on membrane
thickness, operating pressure and
temperature
IEK-3: Electrochemical Process Engineering 33
Challenges for further development - PEM water electrolysis
Approaches for cost reduction
Reduction and substitution of noble metals
Anode: Ir, Ru ~ 0.6 mg/cm²
Cathode: Pt ~ 0.2 mg/cm²
Low-cost, long-life separator plates and current collectors
Scale-up single cell > 1000 cm²
Source: First International Workshop on
Endurance and Degradation Issues in PEM
Electrolysis, March 12th, 2013 | Freiburg, Germany Source: Symposium on Water Electrolysis and Hydrogen as Part of the Future
Renewable Energy System, 10-11 May 2012, Copenhagen, Denmark
IEK-3: Electrochemical Process Engineering 34
Challenges for further development - PEM water electrolysis
Approaches for cost reduction
Reduction and substitution of noble metals
Anode: Ir, Ru ~ 0.6 mg/cm²
Cathode: Pt ~ 0.2 mg/cm²
Low-cost, long-life separator plates and current collectors
Scale-up single cell > 1000 cm²
Source: First International Workshop on
Endurance and Degradation Issues in PEM
Electrolysis, March 12th, 2013 | Freiburg, Germany
Source: Giner Inc.
65 kW / 0.9 m²/cell PEM electrolyzer stack (low-pressure)
IEK-3: Electrochemical Process Engineering 35
Summary
Through the extension of the renewable energies, new challenges emerge with
respect to the storage of large energy quantities.
Hydrogen produced by water electrolysis from renewable energies can solve the
problem of power fluctuation
Only alkaline and PEM electrolysis are commercially available
Investment costs for PEM electrolyzers must be drastically cut
PEM electrolysis development focuses on cost reduction, improving long-term
stability and increasing system size
In addition to more materials research (catalyst and membranes) current
densities and stack size for alkaline electrolysis must be increased and the ability
to handle overloads must be improved
IEK-3: Electrochemical Process Engineering 36
Acknowledgements
Co-workers:
Marcelo Carmo
David Fritz
Maximilian Schalenbach
Daniel Holtz
Stefanie Fischer
Thank you for your attention !