Frano Barbir - Ruđer Bošković Institute · PDF filelocal electrochemical impedance...

Frano Barbir Pictorial Resume

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Diagnosis noun

Investigation or analysis of the cause or

nature of a condition, situation or problem

Diagnostic(s) noun

the art or practice of diagnosis

Diagnostics in fuel cell development process

design

fabricate

test

model

Knowledge:

materials

processes

interactions

requirements

diagnostics

Should

it work?

Does

it work?


Diagnostics in control development process



Diagnostics in operation

controller

fuel cell

control

element

measurement

sensor/

transmitter

process

variable

manipulated

variable

controller

output

signal

measured

value

disturbances

error

set point

measured

process

variable

signal

Observe (voltage/current, pressure drop, temperature)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 20 40 60 80 100 120


Change a parameter and compare

First fuel cell law:

One cannot change only one parameter in a fuel cell —

change of one parameter causes a change in at least

two other parameters, and at least one of them has an

opposite effect of the one expected to be seen.

F. Barbir, PEM Fuel Cells Theory and Practice, Elsevier/Academic Press, 2005

nm m mm m

Fuel cells: Problems at different scales

12700 km 12.7 km 12.7 m 12.7 mm


Change a parameter and compare

Disturb and observe Small disturbances

Large disturbances (exaggerate or accelerate)

controller

fuel cell

control

element(s)

diagnostics

process

variable(s)

manipulated

variable(s)

controller

output

signal(s) controller

action

signal

desired/expected

state of health

diagnosis

measured

values

disturbances



Diagnostics in operation

Post mortem diagnostics

Online

Offline

Post mortem

Electrochemical techniques Polarization curve

Current interruption

Electrochemical Impedance

Spectroscopy

Cyclic Voltammetry

CO Stripping Voltammetry

Linear Sweep Voltammetry

Current Distribution Mapping Partial MEA

Segmented Cells

Species Distribution Mapping Pressure Drop Measurements

Gas Composition Analysis

Neutron Imaging

Magnetic Resonance Imaging

X-ray Imaging

Optically Transparent Fuel Cells

Embedded Sensors

Temperature Distribution Mapping IR Transparent Fuel Cells

Embedded Sensors

Polarization curve

Polarization curve hysteresis

Comparative polarization curves

Current interrupt

AC impedance spectroscopy

Pressure drop

Current density mapping

Temperature mapping

Flow visualization

Neutron/X-Ray imaging

0

0.2

0.4

0.6

0.8

1

1.2

0 500 1000 1500 2000

current density (mA/cm²)

cell

po

ten

tial

(V)

activation losses

resistance losses

mass transport

losses resulting V vs. i curve

theoretical (ideal) voltage

0

0.2

0.4

0.6

0.8

1

1.2

0 500 1000 1500 2000

current density (mA/cm²)

ce

ll p

ote

nti

al

(V)

normal polarization

curve

higher resistance

drying?

mass transport problems

flooding?

hgher activation losses

Data should be taken at multiple current or voltage points.

Typical points would be open circuit and 5 or 6 points between 600 mV/cell and

850 mV/cell,

15 minutes dwell at each point

The data from the last five (5) minutes should be averaged and then plotted as

average current versus average voltage.

Protocol on Fuel Cell Components Testing

Polarization curve sweep

Qiangu Yan, J. Power Sources, Vol 161, 2006, pp 492–502

Presented at IECEC, Portsmouth, VA, August 12, 2003

Static Feed UNIGEN Cycle Test (Total 8/1/03 3:00 PM - 147 cycles)Electrolysis: 60 min @ 200 ASF; Fuel Cell: 40 min @ 300 ASF

160 F, 50-75 psig

0.50

0.70

0.90

1.10

1.30

1.50

1.70

1.90

2.10

2.30

2.50

50.00 50.50 51.00 51.50 52.00 52.50 53.00 53.50 54.00 54.50 55.00

Elapsed Time (hr)

Ce

ll V

olt

ag

e/D

iffe

ren

tia

l P

res

su

re

> 100 LEO cycles

Fuel Cell

40 min

Electrolysis

60 min

M. Weiland, Int. J. Hydrogen Energy,

2012, in print