Description / Abstract:
This recommended practice is intended to serve as a design
verification procedure and not a product qualification procedure.
It may be used to verify design specifications or vendor claims.
Test procedures, methods and definitions for the performance of the
fuel processor subsystem (FPS) of a fuel cell system (FCS) are
provided. Fuel processor subsystems (FPS) include all components
required in the conversion of input fuel and oxidizer into a
hydrogen-rich product gas stream suitable for use in fuel cells.
Performance of the fuel processor subsystem includes evaluating
system energy inputs and useful outputs to determine fuel
conversion efficiency and where applicable the overall thermal
effectiveness. Each of these performance characterizations will be
determined to an uncertainty of less than + 2% of the
value.
The method allows for the evaluation of fuel processor
subsystems for two general cases.
• Compare fuel processors with different designs (e.g.,
catalytic partial oxidation reforming, autothermal reforming or
steam reforming) on a common basis where no specific fuel cell
system design has been identified.
• Assess the performance of a specific fuel processor in the
context of a specific fuel cell system design.
This document applies to all fuel processor subsystems for
transportation applications regardless of fuel processor type, fuel
cell type, electrical power output, thermal output, or system
application (propulsion or auxiliary power unit (APU)). For
example, the fuel processor subsystems associated with proton
exchange, molten carbonate and solid oxide fuel cells can differ
due to the requirements of the fuel cells themselves.
Performance of the fuel processor subsystem, and preprocessor if
applicable, is evaluated. A stand alone processor "system" or even
the primary reactor (e.g., autothermal, partial oxidation or steam
reforming reactor) of a fuel processor subsystem that would
normally be integrated into a fuel cell system can be evaluated.
The fuel processor together with the preprocessor (if required)
converts the fuel (gasoline or other liquid hydrocarbon) to a
reformate gas consisting largely of H2, CO,
CO2, H2O and N2 (if air is sued).
After the fuel processor subsystem, reformate gas typically
contains only trace levels of carbon bearing components higher than
C1. The FPS would be evaluated in a test facility that
is designed to evaluate a stand-alone component rather than a
portion of the reformer such as a specific catalyst or a particular
vessel design.
Any fuel(s) mutually agreed to by the test parties can be sued
such as 1) straight run gasoline (EPA Fuel-CARB reformulated
gasoline Tier II, 30ppm sulfur), or 2) methanol or 3) hydrocarbon
fuel such as iso-octane, naptha, diesel, liquefied natural gas
(LNG) or LPG (propane), etc.
The procedures provide a point-in-time evaluation of the
performance of the fuel processor subsystem. Steady state and
transient (start-up and load-following) performance are included.
Methods and procedures for conducting and reporting fuel processor
testing, including instrumentation to be used, testing techniques,
and methods for calculating and reporting results are provided. The
boundary limits for fuel and oxidant input, secondary energy input
and net energy output are defined. Procedures for measuring
temperature, pressure, input fuel flow and composition, electrical
power and thermal output at the boundaries are provided.
Procedures for determination of the FPS performance measures
such as fuel processor efficiency and cold gas efficiency at a
rated load or any other steady state condition are provided.
Methods to correct results from the test conditions to reference
conditions are provided.
SI units are used throughout the recommended practice
document.
Limitations of Test Procedure
Performance measures included in this document are consistent
with generally accepted conventions. Efficiency, for example, is
based on hydrogen (or hydrogen and carbon monoxide in the case of
solid oxide fuel cells) produced or consumed divided by fuel fed.
This convention for fuel processor efficiency is not consistent
with a strict thermodynamic definition of thermal efficiency based
on a rigorous energy and material balance. Building on this
convention, the recommended practice provides a method to evaluate
fuel processor subsystems based on different designs or different
scope (e.g., air compression or fuel pumping included or excluded).
An approach based on ASME PTC 50 is provided that allows the test
parties to adjust the efficiencies for systems operating at other
than reference conditions during a performance test. In its
simplest application, the approach enables the user to correct
performance measures to a consistent basis without having to
identify a specific fuel cell system or make assumptions about the
performance of other subsystems. If the user has this information
the approach allows for corrections for efficiencies of other
subsystems or components (e.g., oxidant compression/expansion,
water pump, or fuel pump). Terms are included that correct the
compression energy for other inefficiencies in the system such as
power conditioner inefficiency or electrical/mechanical conversion
inefficiency. Values for these terms can be 1) provided based on
the design of a specific system, 2) estimated based on typical
values for these type of energy conversion processes, or 3) omitted
from the expressions and results reported on an ideal compression
basis. Option 3 introduces the least error in the reported
efficiency value. Option 3 would also be the approach the user
would use if the user wanted to use the measured FPS efficiency in
the expression for overall fuel cell system efficiency given
below.
In other words, the calculations to support the determination of
FPS efficiency as provided in the recommended practice document
collapse to a form that is suitable for incorporation in the
generally accepted expression.
The following additional limitations are identified:
a. Excludes performance evaluation over the Federal Urban
Driving Schedule (FUDS) driving cycle. Performance over FUDS
driving cycle is left for evaluation at the vehicle level. A
transient test is included to evaluate response of system to step
change in input demand.
b. Assumes component is provided in its final form, i.e.,
insulated, inlet connections to receive fuel, steam or air (if
required), and exhaust connections to vent reformate gas to flare
stack or hood.
c. Excludes sulfur greater than 30 ppm as described above. It is
assumed that impacts of sulfur or other contaminants such as
chlorides will be addressed by a separate life cycle test to
evaluate long-term performance.
d. Excludes consideration for manufacturers sampling for
production.
e. Assumes specifications for catalyst conditioning are
developed and agreed to by the testing parties.
f. Excludes survivability tests i.e., tilt, vibration, extremes
in ambient conditions. These standard tests will be developed at a
later date.
g. Does not address performance tests for specific components
such as shift reactors or heat exchangers.
h. Excludes tests for environmental factors such as tilt.
i. Excludes tests for human factors such as acoustics/noise,
vibration, harshness.
j. Intended to be a point-in-time test and therefore does not
address aging studies or life.
k. Excludes performance tests for evaluating reliability.
l. Excludes discussion of general safety. Fuel cell system
safety is covered by J2578 document. Safety concerns and
precautions unique to the FPS are addressed.
m. Excludes vehicle level performance (efficiency, acceleration,
emissions, etc.) evaluation.
n. Excludes contamination.
o. Excludes emissions characterization.
p. Does not assess performance on any cost basis.
An example of a fuel contaminant which is likely to have a
cumulative effect on some systems' performance is sulfur (as
determined by ASTM D 129, D 1266, D 1552, D 2427 or D 5453).
Another is chlorine but, there are many others that can affect
system performance through catalyst degradation. For these reasons,
fuel composition and quality have implications far beyond simple
heating values and far beyond the implications for other types of
energy converters. Degradation in long-term performance due to the
presence of contaminants in the fuel is not considered.