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Summary: Catalyst layer (CL) is the most important component in the high‐temperature proton exchange membrane fuel cell (HT‐PEMFC), as it offers reaction sites for hydrogen oxidation reaction (HOR) and oxygen reduction reactions (ORR). As the electrochemical reactions take place at gas/electron/proton interface, the length of this triple‐phase boundary (TPB) in the CL governs the rate of electrochemical reactions. As the TPB in the HT‐PEMFC has not been studied yet, a numerical non‐isothermal 3D model and a percolation micro model were developed in this work to investigate the effect of CLs' properties on both the TPB length and cell performance. The volume fractions, particle size, and particle size ratio of ionomer and Pt/C were selected for optimization. The results show that peak current density could be achieved at an ionomer volume fraction of 52%. Further improvement of cell performance requires smaller particle size and smaller particle size ratio of ionomer. Novelty statement: A three‐dimensional non‐isothermal model of HT‐PEMFC was developed. By adopting the percolation model, length of triple phase boundary of HT‐PEMFC was successfully quantified. The particle parameters including the particle size and ionomer volume fraction can be optimized to increase the length of triple phase boundary, thus achieving higher cell performance. [ABSTRACT FROM AUTHOR]

Self-regulation capability of the open-cathode PEMFC generally means that the stack itself can adjust its state to response to different operating conditions to achieve better performance when the external control strategy remains unchanged. In this paper, self-regulating capability of the stack are analyzed when its cooling fan works under blow or suction mode at different voltages. The result of output voltage shows that the stack achieves better self-regulation when the fan operates at 8.5 V in both blow mode and suction mode. Analysis of impedance spectra reveals that the stack can realize self-regulating function by adjusting activation resistance and ohmic resistance, and the cathode activation resistance is dominant. Furthermore, the result of a cycle load test indicates that the stack can better reflect the self-regulating capability in fan suction mode than in blow mode, and the stack can achieve better water and heat regulation in suction mode. Finally, according to the air velocity distribution and temperature change, it is found that self-regulating capability in suction mode play a better role due to more uniform heat remove. A suitable fan operating voltage and mode are critical for the self-regulating capability of the open-cathode PEMFC stack to maintain a water-heat balance. • Stack voltages under different fan voltages and modes are analyzed. • Mechanism of self-regulating capability of the stack is revealed. • Air velocity distribution maps in fan blow mode and suction mode are compared. • The stack in fan suction mode is proven to have better self-regulating capability. [ABSTRACT FROM AUTHOR]

The application of open-cathode proton exchange membrane fuel cell (PEMFC) has been extended to unmanned aerial vehicles (UAVs), light duty vehicles and other fields, but its performance is highly affected by the temperature fluctuation of stack and ambient temperature. This paper aims to design a thermal management system to achieve higher stack performance and lower fan power consumption by considering ambient temperature and practical application. To do that, a new temperature control strategy is first proposed by studying the relationship between optimal operating temperature and ambient temperature. Then, a model of 1000 W stack including thermal system is built for designing a temperature controller based on constraint generalized predictive control (CGPC). After that, the CGPC controller is enhanced by adding optimized strategy and control rules related to practical application to avoid irreversible damage especially when the current density increases. Finally, the control system with enhanced CGPC is effectively reduce the average error compared with PI control, which is only 0.032 °C. The proposed control strategy with additional control rules is valid by experiments and shows higher performance and lower fan duty cycle of 28.9 % compared with manufacture's default strategy. Thus, the proposed method has significant for widespread application of PEMFC. [ABSTRACT FROM AUTHOR]

This study aims to reveal the mechanism of variable fan speed control in Open cathode PEM fuel cell (OC-PEMFC) by the experiments, which analyze the effects of variable fan speed on the operating parameters under different fuel cell loads. The operating parameters are cell temperature, stack voltage, voltage uniformity, and parasitic power. The results reveal that the fan speed has strong effects on the operating parameters: (1) it affects the temperature distribution and overheats the middle cells of fuel cell stack, especially, when it operates at high power; (2) it affects the variation trend of the voltage under different loads; (3) it affects the voltage uniformity, which can be improved via forced convection; (4) it affects the system efficiency due to the parasitic load consumed by the fan. Considering the varying effects of these operating parameters on performance, durability and system efficiency under different fuel cell loads, the variable fan speed control should adapt the variation of fuel cell loads and weigh multiple operating parameters. • Effect of fan speed on operating parameters is experimentally investigated. • The influence on the performance, durability and efficiency are discussed. • The fan speed control should consider varying demand under different loads. • An adaptive multi-objective optimization problem is introduced. [ABSTRACT FROM AUTHOR]