Testing Performance of the Fuel Processor Subsystem of an Automotive Fuel Cell System
|Publication Date:||1 August 2011|
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/expansio
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.