Fuel-cell testing
Components of a fuel-cell tester
 Hydrogenics' fuel-cell test system uses National Instruments' FieldPoint distributed I/O to monitor and control fuel-cell testing. |
Hardware and software
Although the needs of PEM test engineers are challenging, many components from the test and measurement industry are equipped to handle the task. The hardware components of a test stand include the controller, the fixturing, and the transducers. A popular choice for the controller is a PC-based one. This method offers the advantage of leveraging PC advancements such as speed, memory, and upgradability. A more robust form factor and operating system (OS) offers benefits for the demands of fuel-cell design testing.
A choice that has gained support in recent years is a PXI or Compact PCI, which offers PC capabilities in a rugged and modular form factor. These can be outfitted with a real-time OS that controls data-acquisition and safety features of the test stand.
The highest level of the control software is the test executive. This supervisory level piece of software calls individual test routines, indicates pass/fail, and generates results.
The next level is the test routine software. For reliability purposes, the test routine would run on the non-Windows real-time operating system. An ideal architecture for the routine software would promote modularity and ease of modification, which is important because the procedures for testing fuel cells are evolving along with the technology itself. Test systems built around test executive and graphical programming software are under development and will retain the ability for future modification and run out of the box.
In the testing hardware, I/O components that can digitize signals for the PC are needed. Testers equipped with a multifunction I/O board can scan many channels at both low and high rates. This ability allows engineers to monitor steady-state and transient voltage, current levels produced by the fuel cell, and stack operating parameters. Signal conditioning handles the conversion of current, pressure, and temperature to voltages. In addition to computer and data-acquisition cards, there are a programmable load, a humidification system, gas flow controllers, and a stack temperature controller. The last hardware element is the fixturing. To avoid ionic contamination of the cell membranes, 316 SS, Teflon, or titanium is often used in the water, hydrogen, and oxygen piping. For the same reason, all the water used for cooling and humidification must be deionized before introduction into the stack.
Continued evolution
Fuel cells, as a developing technology, show promise to become one of the most efficient and clean energy-producing sources available. In addition to providing on-demand energy without the CO and NOx typically associated with combustion, they also promise to reduce greenhouse gas emissions with their CO2-free exhaust. However, before they are practical for widespread use, great developmental strides need to be accomplished to reduce size and increase energy yield. Test systems that have the capability to make all relevant measurements while providing the flexibility to incorporate new procedures and calculations are critical to this development. A test platform based on PC technology with the open architecture of the PXI/Compact PCI form factor provides a good test foundation by blending mainstream PC technologies and a rugged reliability while delivering a high degree of modularity. With millions of dollars being invested each year and interest in fuel-cell development being propelled by environmental, governmental, and consumer pressures, the fuel cell will continue to evolve at a rapid pace, and virtual-instrumentation-based controllers will test it every changing step of the way.
Information for this article was supplied by Dave Wilson, Director, Automotive Market Development, and Todd Walter, Application Engineer, National Instruments.
