No abstract

Keywords: EIS PEM fuel cells Hydrogen leak Hydrogen pumping Air starvation Fuzzy logic a b s t r a c t When hydrogen leaks through holes or cracks in membrane-electrode assemblies (MEAs) in Proton Exchange Membrane (PEM) fuel cells, it recombines directly with air. This recombination results in a reduction in oxygen concentration on the cathode side of the MEA. In this paper, the signatures of electrochemical impedance spectroscopy (EIS) are analyzed in different multi-cell stack configurations to show the relation betweenhydrogen leak rate and reduced oxygen concentrations. The reduction in concentration was made by mixing oxygen with nitrogen at different rates, and the increase in hydrogen leak rate was made by controlling the differential pressure (dP) between anode and cathode. To analyze the impedance signatures, we fit the data of oxygen concentration and dP with the parameters of a Randles circuit. The correlation between the parameters of the two data sets allows us to understand the change in impedance signatures with respect to reduction of oxygen in the cathode side. To have a better insight on the effect of insufficient oxygen at the cathode, a model that establishes a relationship between impedance and voltage was considered. Using this model along with the impedance signatures we were able to detect the reduction of oxygen concentrations at the cathode with the help of fuzzy rule-base. However, resolution of detection was reduced with the reduction of leak rate and/or increases in the stack cell count.

No abstract

The economics, infrastructure, transportation, and level of living of a country are all influenced by energy. The gap between energy usage and availability is a global issue. Currently, all countries rely on fossil fuels for energy generation, and these fossil fuels are not sustainable. The hydrogen proton exchange membrane fuel cell (PEMFC) power system is both clean and efficient. The fuel delivery system and the PEMFC make up the majority of the PEMFC power system. The lack of an efficient, safe, and cost-effective hydrogen storage system is still a major barrier to its widespread use. Solid hydrogen storage has the large capacity, safety and good reversibility. As a hydrogen source system, the hydrogen supply characteristics affect the characteristics of the PEMFC at the output. In this paper, a mathematical model of a hydrogen source reactor and PEMFC based on chemical absorption/desorption of solid hydrogen storage is established, and a simulation model of a PEMFC power system coupled with solid hydrogen storage is established using MATLAB/SIMULINK software, and the hydrogen supply of the reactor is analyzed in detail. The influence of prominent factors is evaluated. The research results show that the proposed method improved the system performance. At the same time, increasing the PEMFC temperature, increasing the area of the proton exchange membrane and the oxygen supply pressure can increase the output power of the power system.

The production of isotopes for diagnosis and treatment of cancer patients involves handling and processing of irradiated materials. This process is performed inside heavily shielded workstations termed Hot Cells. A modular robotic design for handling irradiated materials inside hot cells is introduced. The new robotic system is reconfigurable in order to enhance versatility of applications and precision of its tasks. The reliability of the introduced robot control system is assessed using Failure Trees (FT) Methodology. The technology developed in the present work allows for improving productivity and cost effectiveness for production of medical isotopes.