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High Temperature Electrolysis Experimental Activities At The Idaho National Laboratory
Carl StootsJames O’BrienJ. Stephen HerringIdaho National Laboratory
Joseph HartvigsenCeramatec Inc., Salt Lake City, UT
Thomas L. CableUniversity of Toledo, Cleveland, OH, USA
High Temperature Electrolysis Limiting FactorsKarlsruhe, Germany, June 9 – 10, 2009
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Overview
• INL HTE is funded by the US DOE Nuclear Hydrogen Initiative (NHI)• The goal of the NHI is to demonstrate the economic, commercial-scale
production of hydrogen using nuclear energy. • INL is lead lab under the NHI for studying HTE• Historically we have concentrated on SOEC designs from Ceramatec Inc.• With increasing interest in H2 production, we have tested more designs from
various vendors• My talk – overview of experimental activities at INL with some Lessons Learned
Typical Ceramatec SOEC Stack
Rolls Royce Fuel Cell Systems
NASA BSC Stack
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Electrolysis Experimental Activities
Multi-cell (Stack) Testing
Button cell testing
different cell designs & vendorscell material performancelong term performance -- degradation
BOP issues• thermal management / heat recuperation• H2 recyclemulti-stack manifolding / interconnectsassess technology readiness
Bench Scale
Integrated Laboratory Scale (15kW)
ILS Facility (15kW)
Bench scale test stands
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL Bench Scale Electrolysis Test Apparatus (Button Cell)
Bench Scale CapabilitiesINL can simultaneously test:• two button cells• two stacks• special stand for single cell testing
T
P H
D I Water
TPH
T
TsTsT
TTT
I
V
To Roof Vent
T
T
V
Ts
T
T
Nitrogen
Hydrogen
Air
CoolingWater
SV
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL Bench Scale Electrolysis Test Stands
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL Bench Scale Electrolysis Test Stands
Stoots, HTE Limiting Factors, Karlsruhe, 2009
NASA Bi-Supported Cell (BSC)
Construction:
• Structurally symmetric• Electrolyte supported by both
electrodes• Electrodes made by freeze casting and
infiltration (nitrate solution)• YSZ scaffolding• Graded porosity• Ni cathode• LSF anode
• YSZ electrolyte• High power-to-weight ratio (1 kW/kg?)
Stoots, HTE Limiting Factors, Karlsruhe, 2009
NASA BSC Sweeps
Cell area = 2.25 cm2
T = 850 CH2,inlet = 50 sccmN2,inlet = 350 sccmTdp,inlet = 50 C, 62 CyH2O,inlet = 0.35
0
0.1
0.2
0.3
0.4
0.50.8
0.9
1
1.1
1.2
1.3
1.4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Initial Sweep 1Initial Sweep 2Sweep at 20 hoursSweep at 40 hoursSweep at 80 hours
Vol
tage
(V)
Current Density (A/cm2)
ASR
(Ωcm
2 )
Inlet Dew Point T = 50 C
Inlet Dew Point T = 62 CT
furnace = 850 C
H2,inlet
= 50 sccm
N2,inlet
= 350 sccm
Inlet Dew Point T = 50 C
Stoots, HTE Limiting Factors, Karlsruhe, 2009
NASA BSC Long Duration Test
Cell area = 2.25 cm2
T = 850 CH2,inlet = 50 sccmN2,inlet = 350 sccmTdp,inlet = 50 C, 62 CyH2O,inlet = 0.35
2
2.1
2.2
2.3
2.4
2.5
2.6
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 100 200 300 400
Cur
rent
(A) A
SR (Ω
cm2)
Elapsed Time (hours)
Tfurnace
= 850 C
Vref
= 1.2 V
Inlet Dew Point = 62 CH
2 = 50 sccm
N2 = 350 sccm
Swee
pSw
eep
Add
ed in
sula
tion
to v
alve
s Swee
p
Lost
pow
er
Tem
pora
ry sh
ut d
own
Current (A)
ASR
Experimental disruptions affect degradation• Erratic steam flow due to condensation• Power losses• Thermal transients
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Typical Steam Electrolysis Stack Test Ceramatec 10 cell, 20cm x 20cm
0
5
10
15
770
780
790
800
810
820
830
0 20 40 60 80 100
Stack Voltage (V)
ASR (Ωcm2)Stack T #1 (C)
Stack T #2 (C)
Stack T #3 (C)
Stac
k O
pera
ting
Vol
tage
(V)
ASR
(Ωcm
2 )
Stack Internal Tem
perature (C)
Stack Current (A)
Per-Cell ASR
StackVoltageH2 production measured by:
• Change in dew points• Cell current
Measurement of internal stacktemperatures
6
7
8
9
10
11
12
13
14
0
1000
2000
3000
4000
5000
6000
7000
8000
0 20 40 60 80 100
H2 Production (dew points)
H2 Production (current)
Stac
k O
pera
ting
Vol
tage
(V) H
2 Production Rate (sccm
)
Stack Current (A)
StackVoltage
H2
Production
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Typical Steam Electrolysis Stack Test Ceramatec 10 cell, 10cm x 10cm
0
5
10
15
50 100 150 200 250 300
Shunt Current (A)Vint #1Vint #2Vint #3Vint #4Power Supply Voltage (V)Stack Operating Voltage (V)ASR
Elapsed Time (hrs)
Humidifier performance erratic -- humidifier float valve failed and had to be replaced.
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL 15 kW Integrated Laboratory Scale Test
Designed to study BOP issues:• thermal management• heat recuperation• H2 recycle• multi-stack gas manifolding• multi-stack electrical interconnects• technology readiness
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL 15 kW Integrated Laboratory Scale Test
Full operation – September 2008• 3 parallel semi-independent loops• H2 recycle• heat recuperation
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL 15 kW Integrated Laboratory Scale Test
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL 15 kW Integrated Laboratory Scale Test
Safety: One electrical disconnect point for entire experiment
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL ILS Data Acquisition and Control
• Software written in-house using LabView• Lesson learned – high bias voltage problems• 2 National Instruments SCXI signal measurement / conditioning systems
• Isolate high bias voltage measurements from others• 233 I/O channels
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL H2 Recycle Components
• Double-diaphragm H2 recycle pump• Feed-back controlled via computer• User-selectable product recycle split
• H2 recycle storage tank• Condensation in pressurized H2 product is important
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL ILS Modules
• Modules provided by Ceramatec Inc.• Each cell is 10cm x 10cm (8cm x 8cm active area)• Module comprised of 4 60 cell stacks• 3 modules (total of 720 cells)• Stacks are electrically interconnected every 5th cell
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Final Installation Of Cells
Module measurements include voltages, currents, temperatures
240 cells plus manifolds are heavy!
Stoots, HTE Limiting Factors, Karlsruhe, 2009
INL ILS Heat Recuperation Design• Internally manifolded, plate-fin design• 2 heat exchangers per module
• One for steam hydrogen• One for air sweep
• Heat recuperation reduced total electric heater power requirements by half
Example CFD calculation for INL heat recuperation concept
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Three Module ILS Results
• 18 kW peak electrolysis power• 5.7 Nm3/hr peak H2 production rate• Ran for 1080 hours• Condensation in H2 MFCs caused problems for first ~500 hours -> degradation• Proper design and operation of BOP important for cell performance.• Electrolyser cell performance degradation remains problem.
0
1
2
3
4
5
6
0
5
10
15
20
200 400 600 800 1000
H2 Production (Nm3/hr)
Mod 1 ASR
Mod 2 ASR
Mod 3 ASR
H2 P
rodu
ctio
n R
ate
(Nm
3 /hr)
Per-Cell A
SR (Ω
cm2)
Elapsed Time (hrs)
Peak 5.7 Nm3/hr
0
0.5
1
1.5
2
2.5
3
3.5
4
0
5
10
15
20
16 17 18
ASR
(Ωcm
2 )
H2 Production R
ate (Nm
3/hr)
Electrolysis Pow
er (kW)
Elapsed Time (hrs)
Electrolysis Power (Peak = 18kW)
H2 Production Rate (Peak = 5.7 Nm3/hr)
Module 1 Per-Cell ASR
Module 2 Per-Cell ASR
Module 3 Per-Cell ASR
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Steam Electrolysis Experimental Status
• Studying electrolysis degradation mechanisms through bench scale testing
– Dr. O’Brien will speak more about this
• Continuing to characterize performance of cells from various vendors
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Coelectrolysis Experimental Activities
Stoots, HTE Limiting Factors, Karlsruhe, 2009
• Smaller/lighter (more mobile) molecules of H2 -H2 O pair could favor steam electrolysis– Our Area Specific Resistance (ASR) measurements support this:
• ASRcoelectrolysis ~ ASRH2O• ASRdry CO2 > ASRH2O
• Seems that:– H2 O consumed in electrochemical reaction– CO2 consumed in RSR
• Dry CO2 electrolysis is not desirable– High ASR– Possibility of further reduction of CO to C
OHCOHCO 222 +⎯→⎯+
22,
2 22 OHOH heatyelectricit +⎯⎯⎯⎯ →⎯
2,
2 22 OCOCO heatyelectricit +⎯⎯⎯⎯ →⎯Steam electrolysisCO2 electrolysis????Reverse shift reaction
22,
22 OCOHCOOH heatyelectricit ++⎯⎯⎯⎯ →⎯+Coelectrolysis
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Steam vs. Coelectrolysis ASRs
Same stack800 C operating temperature
• Dry CO2 ASR significantly higher than steam ASR• Stack performance same for steam electrolysis or coelectrolysis• Explanation (as stated earlier):
• H2 O consumed in electrochemical reaction• CO2 consumed in RSR
6
7
8
9
10
11
12
13
14
0 5 10 15 20 25
Stac
k O
pera
ting
Vol
tage
(V)
Stack Current (A)
H2O Electrolysis
CO2 Electrolysis
ASRCO2
~ 3.84 Ωcm2
ASRH2O
~ 1.36 Ωcm2
H2O/CO
2 Coelectrolysis
ASRH2O/CO2
~ 1.38 Ωcm2
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Typical Coelectrolysis Stack Results
• At zero current (no electrolysis)• CO2 , H2 consumed• CO produced
• Yield of syngas increased linearly with current• oxygen is removed from gas mixture
• Good agreement with INL-developed coelectrolysis model
0
5
10
15
20
0 2 4 6 8 10 12
Mol
e %
(Dry
Bas
is)
Electrolysis Current (A)
Inlet CO2
Inlet CO
H2
CO
CO2Inlet H
2
Reverse shift reaction
Model Results
Experimental Results
Stoots, HTE Limiting Factors, Karlsruhe, 2009
0
20
40
60
80
100Te
st 1
, Sta
ck In
let
Test
1, S
tack
Out
let
Test
1, M
etha
natio
n O
utle
t Te
st 2
, Sta
ck In
let
Test
2, S
tack
Out
let
Test
2, M
etha
natio
n O
utle
t Te
st 3
, Sta
ck In
let
Test
3, S
tack
Out
let
Test
3, M
etha
natio
n O
utle
t Te
st 4
, Sta
ck In
let
Test
4, S
tack
Out
let
Test
4, M
etha
natio
n O
utle
t Te
st 5
, Sta
ck In
let
Test
5, S
tack
Out
let
Test
5, M
etha
natio
n O
utle
t
CH4
CO
CO2
N2
H2
Coelectrolysis With Subsequent Methanation
Ceramatec extended coelectrolysis with downstream methanation reactor
• 18mm x 1.5m tube• Commercial steam reforming
catalyst (R-67R, Haldor Topsoe)• Outer sleeve to reduce axial
temperature gradient• Reactor T = 300 C• 40% - 50% CH4 (by volume)
produced
Stoots, HTE Limiting Factors, Karlsruhe, 2009
Coelectrolysis Experimental Status• Designing and constructing an integrated demonstration
– Syngas via electrolysis
– Methane via methanation of syngas
– Liquid synfuel
• Methanol
• Fischer-Tropsch liquids