ABSTRACT
Fuel cell performance tests for automotive applications include static and dynamic tests, and the dynamic load test is typically carried out to investigate the cell operating performance related to driving behavior in the particular use of fuel cell electric vehicles. The automatic hydrogen flow controller, utilized to regulate the hydrogen flow as a function of time, is one of the imperative apparatuses applied for the dynamic test. The driving behavior generally consists of rapid load fluctuations, several loads running at idle, full power, overload circumstances, start-stop repeats, and cold starting, and these dynamic variations are directly related to the power required for propelling a vehicle and the demand for hydrogen volume fluctuation throughout time. The desired automatic hydrogen flow controller was designed and manufactured for the dynamic performance test via the driving simulation protocol of a heavy-duty vehicle. The main experimental activities were performed to observe the responsibility and accuracy of the invented controller. The relation between the reliability of using the automatic hydrogen flow controller and the performance improvement of fuel cell operation was studied to gain ideas for further fuel cell modification. The hydrogen flow rates controlled by the created flow controller presented a data tolerance of approximately 0.84% which was not significantly different from the theoretical figure based on T-test analysis. The controller reacted to variations in flow rates in as little as 1-2 s, which was acceptable for the dynamic test. Regarding the performance enhancement, this automatic hydrogen flow controller assisted a single cell to generate 16% more power and 33% more energy at 45 mA as a minimum current demand in comparison with the results obtained from a test system using a traditional hydrogen controller with a constant flow rate.
ABSTRACT
In the cities in the future, seeing electric vehicles on the roads will be as ordinary an occurrence as seeing internal combustion engine cars today. Electric vehicles can greatly benefit from utilizing polymer electrolyte membrane fuel cells (PEMFCs) because they provide higher efficiency (40-50%) and are more environmentally friendly. However, there are some major drawbacks to using PEMFCs as electrical sources in vehicles; these are energy balance and management issues that must be addressed to meet vehicle power and energy requirements. Therefore, it seems that hybridizing PEMFCs with energy storage devices, such as supercapacitors (SCs), would be an efficient solution to address these drawbacks in order to accommodate driving behaviors such as dynamic loads. The goal of this research is, therefore, to demonstrate the use of a PEMFC-SC direct hybridization configuration with a dynamic stress test by simulating driving behavior in urban areas such as Bangkok. This research presents substantial advantages in energy management and voltage and material degradation. In order to achieve this objective, a quasi-static stress profile, including stationary conditions, load variations, and start-stop conditions, was specifically created for PEMFC-SC direct hybridization systems with 840 hours of operating duration. The performance, durability, and reliability of this system were investigated via polarization curves, hysteresis loops, and voltage degradation rates. Then, experimental results were compared to the degradation of the cell components. Any degradation in material components was observed through electrochemical impedance spectroscopy (EIS) and morphology studies. The characterization of materials in the PEMFC-SC direct hybridization systems via chemical and electrochemical analyses is an important approach in material invention and modification for the new generation of PEMFCs. This work strives to pave the way for PEMFC hybridization development to achieve effective commercialization.
