DESIGN AND CONTROL OF
HIGH TEMPERATURE PEM FUEL CELL SYSTEMS
USING METHANOL REFORMERS
- AIR OR LIQUID HEAT INTEGRATION -
SØREN J. ANDREASEN
ASSOCIATE PROFESSOR, FUEL CELL AND BATTERY RESEARCH GROUP
Outline
• Introduction
• System control approach
• Methanol reformers and HTPEM fuel cells
• Air heat exchange
• Liquid heat exchange
• System control challenges
• Conclusion
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System control approach
System
Design
Component
Characterization
/Modelling
Control
Strategy
Development
Controller
Evaluation
/Implementation
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Reformed methanol HTPEM fuel cell systems
•
•
•
•
PBI-based MEAs have a high tolerance to CO
A liquid fuel, such as methanol is easily accessable and storable
Heat can be utililzed in fuel conversion
System energy density increase is ”cheap”
• System size and complexity increases
• Impurities are introduced
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Applications – Hybridization
•
Complicated system dynamics
often require hybridization with
electrical energy storage for
high lifetime and reliability
•
Improvements in load following
could be attained using control
schemes
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Reformer system - air heat exchange
•
Cathode air cooled FC
stacks have high quality
waste heat that can be
directly transferred and
used for evaporation of
reformer fuel.
•
Proper heat integration
and design is required to
avoid high BoP
consumption.
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Reformer system - air heat exchange
•
Individual system components are
characterized ex-situ, such that fuel cell
stack and reformer system behaviour can
be separated.
•
Fuzzy logic / Neural network models of
internal system states, can be developed
•
Model based control approaches are
implemented in system software and
system improvements are quantified.
Serenergy H3-350 off-grid
battery charger
(HTPEM + SR)
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Reformer system - air heat exchange
•
Example: Extensive ex-situ reformer
output gas measurements using gas
analyzers create the foundation for
”learning” system behaviour by an
Adaptive Neuro-Fuzzy Inference
System (ANFIS) model.
•
Proper prediction of gas composition,
a n o d e s t o i c h i o m e t r y, e t c . c a n e n a b l e
h i g h e r e f f i c i e n c y, r e l i a b i l i t y a n d
lifetime.
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Reformer system - liquid heat exchange
•
Liquid heat transfer can
minimize system size and BoP
power consumption.
•
System logistics are more
conventional.
•
Several system topologies are
usable depending on
application utility heat and
demand.
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System control challenges
•
Pump flow determines
usable hydrogen flow in the
FC anode, but fuel
evaporation and conversion
need to be considered.
•
A modelbased approach can
be used for proper
feedforward contol and
determination of system
setpoints.
•
For example ANFIS
modelling can provide high
prescision state prediction
based on experimental
results avoiding undesired
system operating conditions.
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Conclusions
• Efficient and reliable HTPEM fuel
cell systems are at a
development stage, where
system design and control are
increasingly relevant.
• Fuel cell systems are excellent
part load performers, but lag,
complex systems dynamics and
expensive state monitoring can
limit load following capabilities
and system performance.
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Acknowledgements
The authours would like to gratefully acknowledge the financial support from
the EUDP program and the Danish Energy A gency for sponsoring the project
:COmmercial BReakthrough of Advanced Fuel Cells - (COBRA)
Thank you
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