Fiber Optic Temperature Sensors for PEM Fuel Cells
Transcript of Fiber Optic Temperature Sensors for PEM Fuel Cells
Fiber Optic Temperature Sensors for PEM Fuel Cells
Timothy J. McIntyreW. P. Partridge, S. W. Allison, L. C. Maxey, M. R. Cates,C. L. Britton, R. Lenarduzzi, T. J. Toops, and T. K. Plant*
(* Oregon State University)
DOE Annual Program ReviewMay 23-26, 2005
This presentation does not contain any proprietary or confidential information.
Project ID# FC42
Project TimelineProject Overview
Partners
Project ID# FC42
January2003
January2004
January2005
Phase 1 - Concept Development
Phase 2 - Concept Validation
Phase 1 - Concept Utilization
Project Milestone
September2005
Advanced Concept Development
1 2
3 4
5
1 - Lab feasibility demo.Go/No-Go
2 - Concept complete3 - Field feasibility demo.4 - Field validation5 - Utilization in operating
system6 - Demonstrate novel 2
photon technique
6
Project Budget
FY 2005 = $405k, all DOE funds
Barriers - Transportation Systems B.• Automotive sensors required to meet performance and cost targets for measuringphysical conditions and chemical species in fuel cell systems.
• Current sensors do not perform within the required ambient and process conditions,do not possess the required accuracy and range, and/or are too costly.
Targets - Automotive Fuel Cell Systems, Temperature• Sensors must conform to size, weight, and cost constraints of automotive applications• Operating range: -40 to 150°C• Response time: -40 to 100°C range <0.5 seconds with 1.5% accuracy; 100 to 150°Crange <1.0 seconds with 2% accuracy
• Gas environment: high humidity reformer/partial oxidation: H2 30% - 75%, CO2, N2,H2O, CO at 1 - 3 atm total pressure.
• Insensitive to flow velocity.
Technical Barriers and Targets
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Overview of Reviewer FeedbackReview Comment: Develop a multiplexing approach for thermal mapping
• Demonstrated a 5 sensor platform that could easily be scaled to over 10
Review Comment: More interaction with auto companies
• Beginning collaborative efforts with GM
Review Comment: Focus more on robust measurement to acquire new information than low-cost system
Review Comment: Perform sensor durability/compatibility testingReview Comment: Demonstrate measurements in operating fuel cells, forget
about low cost• 2 parallel demonstration/evaluation programs (Plug Power and in-house)• Sensors have been demonstrated in operating fuel cells.
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Project Objective
Provide measurement and diagnostic tools to fuel cell developersfor system performance optimization and model validation.
Real-time intra-fuel cell measurements of temperature and species (Humidity) made within operating PEM fuel cells.
• Demonstrate intra-fuel cell transient temperature diagnostic
• Characterize ‘typical’ intra-fuel cell temperature distributions
• Demonstrate intra-fuel cell species diagnostic (developed in separate DOE program)
* Combining temperature and species measurements provides dynamic humidity distribution
• Identify performance characteristics of fuel cell that suggest operational/design limits
Technical Approach• Construct luminescence-based sensors w/micro-ruby transducers
• Instrument fuel cells (multiple testing platforms and sensor configurations)
• Operate fuel cells to characterize operational relationships
Fuel cell courtesy of
250 micron ruby sphere tipped fiber233 micron ruby rod straddling flow channel
OpticalFiber
Bi-polarPlate
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Technical Accomplishments
• Demonstrated intra-fuel cell temperature and species measurements within operating fuel cell(s)
• Characterized spatial distributions of temperature and humidity• Demonstrated correlation between temperature and humidity
distributions• Characterized time and temperature dynamics for improved
diagnostics• Demonstrated approach for improving detailed understanding of
realistic fuel cell system kinetics/chemistry* Pathway for optimizing operational and design parameters
(e.g. flow rates, pressure, concentrations, Pt distribution, flow path geometry, materials characteristics, etc.)
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Fuel Cell Platform(Plug Power)
2530354045505560657075
90 100 110 120 130 140Time (minutes)
Tem
pera
ture
(°C
)
MEA Centered Temperature Sensor Monitoring Cooldown
Water droplet passing sensor due to nitrogen purge
Water droplet events observed prior to shutdown
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55
60
65
70
75
150 170 190 210 230 250 270 290Time (minutes)
Tem
pera
ture
(°C
)Temperature Sensor at MEA Center
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55
60
65
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150 170 190 210 230 250 270 290
Temperature Sensor Near Gas Inlet
Time (minutes)
Tem
pera
ture
(°C
)
Thermography Data from Experiments at Plug Power
Water droplet formation rate varies with Operating Parameters
Cell temperature varieswith applied load and operating parameters
And position in cell
Sensors show similar trends in fuel cell temperature.
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Fuel Cell Platform(in house)
• Commercially available 2-cell stack• 7-cm x 7-cm active area per cell• Flow path: 13-pass, 918-mm dual-serpentine, crossed anode-cathode flows,
~1.27-mm diameter half channel, 0.633-mm2 flow area
Probes toInstruments
BPRBPR
MFCMFC
Gas BottlesExhaust
PEM
Fue
l Cel
l
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Probe Access for Intra-Fuel Cell Measurements• Fiber and capillary probes were installed at the inlet, 2x, 6x, 8x,
10x, (0, 0.2, 0.4, 0.6, 0.8, and 1L) and outlet positions• Temperature Probes ~0.4-mm OD: 19.9% flow area (next
generation 80 micron probe: 0.8% flow area)• Species Probes ~0.15-mm OD: 2.8% flow area• Thermocouples at fuel cell inlet and outlet
Ruby-tippedtemperature sensor
Micro-capillaryfor species measurements
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Experimental ConditionsThe fuel cell was evaluated at :
• Two temperatures: 30° and 72°C• Three gas flow rates: 50, 100 and 200 sccm• Two power levels: Low Power (LP), & High Power (HP)
Room Temp High Temp
Nominal Inlet/Outlet FC Temp (°C)
Water Bath Temp (°C)
Inlet Relative Humidity (%)
Anode (dry)
Cathode (dry)
30 72
27 58.9
84 56
50% H2 in N2, 10 psig 50% H2 in N2, 10 psig
20% O2 in N2, 12.5 psig 20% O2 in N2, 12.5 psig
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High-Temp Operation Shows Stepped Temperature Changes
Fuel Cell Conditions
Slow cooling, ~4°C/hr
All temperature measurements show stepped behavior
Inlet heats up too –strong front-end reaction?
High Temp PEM Fuel Cell Heating : 100sccm Case
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71
72
73
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75
300 320 340 360 380 400 420 440 460 480 500 520Time (min)
Tem
pera
ture
(C)
InletOutlet20pt Avg (10x Temp)20pt Avg (6x Temp)
Spac
iMS
'1O
hm',
100s
ccm
Spac
iMS
'Sho
rt', 1
00sc
cm
H2, O2 On,Very LP
LPH2, O2 Flow Off H2, O2 Flow OffHP
• Fuel cell heating ~ on the order 3-5°C• Interior temperatures can be > or < inlet and outlet temperatures• Temperature dynamics occur on 1-10 minute time scales• Even fast dynamics occur on the order of ~1 minute
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Phosphor Thermography Resolves Transient Intra Fuel Cell Temperature Distributions
Slow heating, ~5°C/hr
Species Measurements
Room Temp PEM Fuel Cell Heating
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0 20 40 60 80 100 120 140 160 180 200 220Time (min)
Tem
pera
ture
(C)
InletOutlet20pt Avg (6x Temp)20pt Avg (10x Temp)
Spac
iMS
'1O
hm' ,
100s
ccm
Spac
iMS
'Sho
rt', 5
0scc
m
Spac
iMS
'Sho
rt', 2
00sc
cm
Spac
iMS
'Sho
rt', 1
00sc
cm
H2,O2 On,100 sccm,Very LP
100 sccm,LP
H2, O2 Flow Off 100 sccm,HP
50 sccm,HP
200 sccm,HP
100 sccm, Very LP
Fast Transients occur on 1-2 minute timescale
Intermittentcooling event(s)
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SpaciMS Resolves Transient Intra Fuel Cell Water and Species Distributions
Fuel cell power shows dynamic behavior at ‘stationary’ conditions
Local N2 ~ mirrors O2
Humidity increases inside fuel cell
O2 increases in outlet manifold to ~ inlet value
• un-instrumented cell inactive or degraded
Room Temp, 100 sccm, High Power
0.0E+00
2.0E-10
4.0E-10
6.0E-10
8.0E-10
1.0E-09
1.2E-09
1.4E-09
7 9 11 13 15Time (min)
H2O
, N2,
O2
and
Blan
k S
igna
l (A)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
FC O
utpu
t Pow
er (W
)
H2ON2O2BlankPower
10xOutlet 8x 6x 2x Inlet
With temperature and pressure can determine relative humidity from H2O
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High Humidity at 6x Location for Room Temp 200 sccm Case
Distinct and localized high humidity
8% Power increaseRoom Temp, 200 sccm, High Power
0.0E+00
2.0E-10
4.0E-10
6.0E-10
8.0E-10
1.0E-09
1.2E-09
1.4E-09
8.5 10.5 12.5 14.5 16.5Time (min)
H2O
, N2,
O2
and
Bla
nk S
igna
l (A
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
FC O
utpu
t Pow
er (W
)
H2ON2O2BlankPower
10xOutlet 8x 6x 2x Inlet
O2 depletion is greater in lower-flow case
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Without Condensation, Temperature and Relative Humidity Profiles are Flat within Fuel Cell
Largest temperature and relative humidity gradients occur in front 2x of fuel cell
Temperature and relative humidity decrease at outlet
• consistent with degraded parallel cell
Room Temp, 100 sccm, High Power
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Inlet 2x 6x 8x 10x OutletPosition Along FC Cathode Flowpath (x : number of passes)
Loca
l Tem
pera
ture
(C)
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Loca
l Rel
ativ
e H
umid
ity (%
)
Temp%RH
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Locally Condensing Conditions Create Localized Cooling
Relative humidity = 100% Locally Condensing Conditions
Localized cooling : Condensation orEvaporative cooling?
Room Temp, 200 sccm, High Power
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31
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Inlet 2x 6x 8x 10x OutletPosition Along FC Cathode Flowpath (x : number of passes)
Loca
l Tem
pera
ture
(C)
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85
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100
Loca
l Rel
ativ
e H
umid
ity (%
)
Temp%RH
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Increasing Reactant Flow Rate Cools Fuel Cell and Decreases O2 Consumption Rate
6% power increase
Major heating is in fuel cell front end (like at room temperature)
Overall cooling trend
O2 rate difference primarily 6x to 10x
O2 rate similar at fuel cell front
Output power increases despite less O2 consumption• Due to cooling effect?
Halving residence time did not half O2 consumption• Not reactant limited at 100sccm; maybe diffusion limited
Heating Rate and Oxygen Consumption, High Temp, High Power100sccm base flow (2Y mpm), HF:200sccm (4Y mpm), LF:50sccm (1Y mpm)
0
0.4
0.8
1.2
1.6
2
Inlet 2x 6x 8x 10x OutletPosition Along FC Cathode Flowpath (x : number of passes)
Rel
ativ
e H
eatin
g R
ate
and
O2
Con
sum
ptio
n
dT/dt, 100sccmdT/dt, 200sccm-dO2/dt, 100sccm-dO2/dt, 200sccm
P(100sccm, HP) : 1.16 WP(200sccm, HP) : 1.23 W
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Decreasing Reactant Flow Rate Cools Fuel Cell and Increases O2 Consumption Rate
Heating Rate and Oxygen Consumption, High Temp, High Power100sccm base flow (2Y mpm), HF:200sccm (4Y mpm), LF:50sccm (1Y mpm)
0
0.4
0.8
1.2
1.6
2
Inlet 2x 6x 8x 10x OutletPosition Along FC Cathode Flowpath (x : number of passes)
Rel
ativ
e H
eatin
g R
ate
and
O2
Con
sum
ptio
n
dT/dt, 100sccmdT/dt, 50sccm-dO2/dt, 100sccm-dO2/dt, 50sccm
P(100sccm, HP) : 1.16 WP(50sccm, HP) : 0.36 W
69% power decrease
Overall cooling trend
O2 is depleted by the 2x position
Back >80% of the flow path is inactive
Relative humidity was near or at saturation throughout fuel cell
Significant heating at 50 sccm indicative of strong spatially confined reaction?Doubling residence time completely depleted O2
• Reactant limited at 50 sccm • Further indicates diffusion limitation at 100 sccm
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Intra Fuel Cell Temperature and Species Measurements can Identify Performance Limitations
• The performance-limiting process can vary across the fuel cell (e.g., reactant depletion, diffusion, product surplus, localized site blocking,…)
• Intra fuel cell measurements can identify the local limiting processes
• More detailed experiments required* Change anode and cathode flows individually* Change concentration at constant residence time* Change residence time at constant molar flow rate
• Better understanding of these processes in realistic systems may improve performance via improved design and materials selection
* Temperature profile, Pt distribution, transport characteristics (O2, H2, H+, H2O)
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Fuel Cell Performance can be Dynamic Even at ‘Stationary’ Conditions
• Power dynamics may indicate regulation by limiting process
• O2 dynamics correlate with fuel cell output power
• Temperature and humidity may also correlate similarly
• Power-chemistry relationships are observable
Suggests meaningful chemical insights are accessible
Correlation of PEM FC O2 Use and Power, High Temp, 100sccm
0.0E+00
5.0E-11
1.0E-10
1.5E-10
2.0E-10
2.5E-10
3.0E-10
0 20 40 60 80 100Time (min)
O2
Sign
al (A
)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
FC O
ut P
ower
(W)
O2Power
LP,6x
HP,6x
HP,8x
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Summary Conclusionsand Technical Accomplishments
• Intra-fuel-cell measurements demonstrated* Temperature* Humidity* Species including H2, O2, H2O, N2, Ar (others possible)
• Dynamics are slow, ~ minutes, and temperature changes are small, ~5°C
• No localized dry zones were observed
• Dynamic behavior routinely observed under stationary conditions* Symptomatic of detailed process limitations?
• Diffusion layer appears to efficiently transport water along flow path
• Methods demonstrated for achieving next-level performance understanding and improvements
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Future WorkMore extensive spatial mapping
• Stacks, not just cells?• Does feed gas short circuit flow path via diffusion layer?
Anode and cathode side instrumentation• Balance of reactants and products?
More extreme operating conditions to highlight barriers• Localized drying/flooding?
More controlled operation variations (drive cycle) to identify origins of local efficiency limitations.
Further instrument improvements• Advanced measurement methods instead of single probes, probe size,
signal-to-noise, temperature and time resolution, etc.
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Presentations, Publications and PatentsPresentationsFiber Optic Temperature Sensors for PEM Fuel Cells: Progress Report, Fuel
Cell Expo, San Antonio, TX, 2004.
Publications1. Development of Fiber Optic Sensors for Fuel Cells: Issues and Results,
Cates, M. R., S. W. Allison, L. C. Maxey, and T. J. McIntyre, Instrument Society of America, 2005.
2. Development of Optical Fuel Cell Temperature Measurements, Maxey, L. C., and T. J. McIntyre, Instrument Society of America, 2005.
Patents1. Duel-mode Optical Temperature and Humidity Sensor for PEM Fuel
Cells.2. 2-photon Induced, Spatially Resolved Temperature Sensing.3. Embedded Waveguide Sensors and Thin Polymer Membranes.
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Project SummaryRelevance: Help to answer fundamental questions necessary for energy-
efficient PEM fuel cell implementation.
Approach: Develop and apply intra-FC diagnostics to characterize transient performance characteristics
Technical Accomplishments and Progress: Demonstrated dynamic temperature, humidity and species distributions throughout an operating PEM fuel cell
Technology Transfer/Collaborations: Active partnership with Plug Power and others, new partnership with GM, presentations, publications and patents
Proposed Future Research: Apply intra-FC diagnostics to identify performance barriers and pathways for performance
Tim McIntyre865-576-5402
Project ID# FC42
Hydrogen SafetyThe most significant safety risk would be a hydrogen supply gas leak or mishandling of unutilized hydrogen exhausted from the fuel cell.
• All project activities at ORNL are covered by a formal, integrated work control process for each project/facility
– Definition of task– Identification of hazards– Design of work controls– Conduct of work– Feedback
• Each work process is authorized on the basis of a Research Safety Summary (RSS) reviewed by ESH subject matter experts and approved by PI’s and cognizant managers
• RSS is reviewed/revised yearly, or sooner if a change in the work is needed• Staff with approved training and experience are authorized through the RSS
To minimize any potential safety risks on this project the following actions are taken:
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Interesting Observations via Multiple DiagnosticsHigh Temperature Fuel Cell Operation
FC@~71C, Anode 50%H2 50%N2 ~10psig, Cathode 20%O2 80%N2 ~12.5psig, H2Osat@~58.9C100sccm base flow, HF:200sccm, LF:50sccm
0
2
4
6
8
10
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16
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Inlet 2x 6x 8x 10x OutletLocation along 13-Pass Serpentine Fuel Cell Cathode Channel
Oxy
gen
Con
cent
ratio
n (%
V/V
)
1 OhmShort1 Ohm, HFShort, HF1 Ohm, LFShort, LF
High Temperature Fuel Cell OperationFC@~71C, Anode 50%H2 50%N2 ~10psig, Cathode 20%O2 80%N2 ~12.5psig, H2Osat@~58.9C
100sccm base flow, HF:200sccm, LF:50sccm
20
30
40
50
60
70
80
90
Inlet 2x 6x 8x 10x Outlet
Location along 13-Pass Serpentine Fuel Cell Cathode Channel
Rel
ativ
e H
umid
ity (%
)
1 OhmShort1 Ohm, HFShort, HF1 Ohm, LFShort, LF
High Temp PEM Fuel Cell Exp.
70
70.5
71
71.5
72
72.5
73
73.5
74
Inlet 2X 6X 8X 10X OutletPosition Along PEM Cathode Serpentine Flowpath (x : number of passes)
1Ohm, 100sccmShort, 100sccm1Ohm, 200sccmShort, 200sccm1Ohm, 50sccmShort, 50sccm
High Temperature Fuel Cell OperationFC@~71C, Anode 50%H2 50%N2 ~10psig, Cathode 20%O2 80%N2 ~12.5psig, H2Osat@~58.9C
100sccm base flow, HF:200sccm, LF:50sccm
-30
-20
-10
0
10
20
30
40
Inlet 2x 6x 8x 10x Outlet
Location along 13-Pass Serpentine Fuel Cell Cathode Channel
Cal
cula
ted
Wat
er G
ener
atio
n (b
ased
on
O2
Use
) (%
V/V
)
1 OhmShort1 Ohm, HFShort, HF1 Ohm, LFShort, LF
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Under Differing Operational Conditions the Fuel Cell Thermal Profile Varies
Average FC Heating Rate
0.015
0.020
0.025
0.030
0.035
0.040
Inlet 2X 6X 8X 10X Outlet
Position Along PEM Cathode Serpentine Flowpath (x : number of passes)
50sccm100sccm200sccm
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Observed Power Outputfrom Fuel Cell During Testing
High Temperature Fuel Cell OperationFC@~71C, Anode 50%H2 50%N2 ~10psig, Cathode 20%O2 80%N2 ~12.5psig, H2Osat@~58.9C
100sccm base flow, HF:200sccm, LF:50sccm
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1 Ohm Short 1 Ohm, HF Short, HF 1 Ohm, LF Short, LF
Fuel Cell Load and Flow Conditions
Fuel
Cel
l Out
put P
ower
(W)