an integrated high pressure sofc and premixed …
TRANSCRIPT
An Integrated High Pressure SOFC and Premixed
Compression Ignition (PCI) Engine System
Sage Kokjohn, University of Wisconsin - Madison
Development of a “plug and play” engine system for integration with
solid oxide fuel cell based distributed power generation systems
Project Vision
Project Overview
Project Context
Project brings together expertise in advanced combustion engines and
solid oxide fuel cell systems to harness synergies between the devices
Fed. funding: $1.7YM
Length 24 mo.
Team member Location Role in project
University of
Wisconsin -
Madison
Madison, WI Program Lead
Advanced Combustion Development
Caterpillar Peoria, IL Balance of Plant Component Development
Tech to market
United
Technologies
Research Center
East Hartford, CT Fuel Cell Modeling
System Layout
Wisconsin Engine
Research
Consultants
Madison, WI Engine Modeling
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Phase I: Approach and Objectives
ApproachIntegration of an advanced, combustion
engine with a solid oxide fuel cell
system to enable operation on depleted
anode tailgas beyond what is possible
with current combustion technology
Task outline, technical objectives• Evaluate the needed combustion
strategy to efficiently consume
depleted anode tailgas
• Develop air and fuel handling system
(integrated with the engine) to supply
air and fuel to the engine and SOFC
• Evaluate approaches for load
following / transient operation
Tech-to-Market objectives
• Identify customers for a “plug and
play” engine system for the
distributed generation market
• Assess market potential and “value”
of a 70% distributed generation
system
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System Overview
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‣ System layout (Aspen HYSYS) developed demonstrating 70% electrical efficiency
at 1 MWe
‣ Key system components
– High efficiency, pressurized SOFC
operating near 80% fuel utilization
(~90% of net power 900 kW)
– Energy recovery using
reciprocating engine with
advanced combustion (~10% of
net power 100 kW and cathode
air flow assistance)
– Energy recovery using turbo-
machinery for both engine and
SOFC
– Fuel processing (desulfurization,
pre-reforming, etc…)
1 MWe System at 70% Electrical Efficiency
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‣ System model used to evaluate
part-load operation and identify
pathways to maintain high
efficiency
‣ Increase in efficiency at part
load due to combination of lower
current density and lower BOP
losses
‣ Cathode airflow reduced, pre-
reforming increased, and anode
heat exchanger bypass used to
maintain stack temperature
Displacement [L] 2.5
Stroke [mm] 171
Bore [mm] 137
Con. Rod [mm] 261
Swirl Ratio 0.7
Compression Ratio 16.8:1
IVC [°ATDC] -154
EVO [°ATDC] 113
‣ Single-cylinder test cell setup to
represent operation on anode tailgas
‣ Engine represents one cylinder of the
6 cylinder, 15 L engine
‣ Fuel blending system allows
operation at SOFC fuel utilization
above 80% (CO, H2, CO2, H2O)
Engine Operation on Dilute Tailgas
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Utilizing Dilute Anode Tailgas in a Recip.
‣ Operation on anode tailgas is challenging due to the low flame speed resulting
from dilute mixtures
‣ Two approaches investigated to enable operation on diluted anode tailgas
– Homogenous Charge Compression Ignition (HCCI) combustion
– Pre-chamber assisted spark-ignited combustion
Spark Ignition HCCI Combustion Pre-chamber SI combustion
Pre-chamber image from
Zigler DOE AMR 2019
Utilizing Dilute Anode Tailgas in a Recip.
‣ HCCI combustion
– Stable combustion is achievable with relevant operating temperature (~80°C)
– Peak gross indicated efficiency ~45%
– Engine out NOx less than 0.05 g/kW-hr NOx aftertreatment is not required
– Operation at intake pressures below 225 kPa is challenging requires SOFC pressure greater than ~250 kPa
– Combustion phasing is controllable using water injection
𝐺𝐼𝐸 =𝐼𝑛𝑑𝑖𝑐𝑎𝑡𝑒𝑑 𝑃𝑜𝑤𝑒𝑟
𝑚 𝑎𝑛𝑜𝑑𝑒𝑡𝑎𝑖𝑙𝑔𝑎𝑠
𝐿𝐻𝑉𝑎𝑛𝑜𝑑𝑒𝑡𝑎𝑖𝑙𝑔𝑎𝑠
Increase
Water
All cases at 80% SOFC fuel utilization
Utilizing Dilute Anode Tailgas in a Recip.
‣ Pre-chamber SI combustion
– Stable operation possible at
intake pressures up to ~225
kPa at 80% fuel utilization
(85% is possible at intake
pressures up to 175 kPa)
– Peak gross indicated efficiency
approximately 45%
– Easily controllable combustion
phasing
– NOx below 0.1 g/kW-hr
NOx aftertreatment not
required
Stable
Combustion
Unstable
Combustion
Utilizing Dilute Anode Tailgas in a Recip.
‣ Peak gross indicated efficiency occurs under spark-assisted
compression ignition (SACI) conditions
– Early portion of burn is flame propagation
– Final burn is auto-ignition
Utilizing Dilute Anode Tailgas in a Recip.
‣ The impact of water
knockout was studied
‣Minimal benefit of
water removal
– Gross indicated
efficiency increases
by ~0.7%
– Engine efficiency
increase likely
outweighed by
system efficiency
penalty
Remove
Water
Add
Water
Utilizing Dilute Anode Tailgas in a Recip.
‣ HCCI and pre-chamber SI show similar
efficiency
‣ Evaluation of complete water removal shows
minimal benefit
‣ Stable combustion is possible using both
strategies, but the pressure range is different
– HCCI > 225 kPa
– Pre-chamber SI < 225 kPa
‣ System may require CO aftertreatment
‣ NOx aftertreatment is not required and NOx is
an order of magnitude below US electricity
generation average ultra dilute combustion
Other Developments
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‣ Printed heat exchangers using a range of materials have been tested
and performance is similar to / or better than fabricated versions with
more material / geometry flexibility
‣ Load following studies using transient flow model have demonstrated
ability to add / remove power using the engine
Phase I Summary and Future Plans
‣ Effort has identified a system capable of achieving greater than 70% electric efficiency over
a wide range of operating conditions
‣ Engine combustion experiments show that a passive pre-chamber is suitable to enable high
efficiency operation up to 85% fuel utilization
– Combustion mode is spark-assisted compression ignition (SACI)
– Indicated efficiency near 45% (approaching diesel engine efficiency)
– Ultra-low NOx without aftertreatment NOx below 0.1 g/kW-hr (engine only) and
0.01 g/kW-hr (system)
– CO aftertreatment may be required (low cost, passive, mature technology)
‣ Cost assessments suggest stack cost dominates system cost, but overall cost-uncertainty
is high Market assessment suggests multiple regions where payback may be favorable
‣ Ongoing efforts will finalize engine testing and systematic evaluation of engine system and
refine cost-assessment
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