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This paper presents an innovative thermally coupled system architecture with a parallel coolant-heated metal hydride tank (MHT) designed to satisfy the hydrogen supply requirements of proton exchange membrane fuel cell s(PEMFCs). This design solves a problem by revolutionising the cold start capability of PEMFCs at low temperatures. During the design process, LaNi5 was selected as the hydrogen storage material, with thermodynamic and kinetic properties matching the PEMFC operating conditions. Afterwards, the MHT and thermal management subsystem were customised to integrate with the 70 kW PEMFC system to ensure optimal performance. Given the limitations of conventional high-pressure gaseous hydrogen storage for cold starting, this paper provides insights into the challenges faced by the PEMFC-MH system and proposes an innovative cold start methodology that combines internal self-heating and externally assisted preheating techniques, aiming to optimise cold start time, energy consumption, and hydrogen utilisation. The results show that the PEMFC-MH system utilises the heat generated during hydrogen absorption by the MHT to preheat the PEMFC stack, and the cold start time is only 101 s, which is 59.3% shorter compared to that of the conventional method. Meanwhile, the cold start energy consumption is reduced by 62.4%, achieving a significant improvement in energy efficiency. In conclusion, this paper presents a PEMFC-MH system design that achieves significant progress in terms of time saving, energy consumption, and hydrogen utilisation. [ABSTRACT FROM AUTHOR]

Featured Application: The multi-stack fuel cell system proposed in this paper can be applied to high-power generation, transport, and other engineering fields. A multi-stack fuel cell system (MFCS) is a promising solution for high-power PEM fuel cell applications. This paper proposes an optimized stack allocation approach for power allocation, considering economy and dynamics to establish integrated subsystems with added functional components. The results show that an MFCS with target powers of 20 kW, 70 kW, and 120 kW satisfies lifetime and efficiency factors. The common rail buffer at the air supply subsystem inlet stabilizes pressure, buffers, and diverts. By adjusting the volume of the common rail buffer, it is possible to reduce the maximum instantaneous power and consumption of the air compressor. The integrated hydrogen supply subsystem improves hydrogen utilization and reduces parasitic power consumption. However, the integrated thermal subsystem does not have the advantages of integrated gas supply subsystems, and its thermal management performance is worse than that of a distributed thermal subsystem. This MFCS provides a solution for high-power non-average distribution PEM fuel cell systems. [ABSTRACT FROM AUTHOR]

To describe the degradation of proton exchange membrane fuel cells (PEMFCs), empirical degradation models of different indexes of PEMFCs are established. Firstly, the simulation process and assumptions of PEMFC degradation are proposed. Secondly, the degradation simulation results including the performance and distribution indexes under the different degradation levels are conducted by AVL FIRE M. Finally, the empirical degradation models of performance and distribution indexes are established based on the above simulation results and experimental data. The results show that the relationship between the experimental and simulation results is established by the index of current density. The empirical degradation models of current density, average equilibrium potential on the cathode catalyst layer (CL), average membrane water content, average oxygen molar concentration on the cathode CL, and average hydrogen crossover flux are the linear function. The empirical degradation models of average exchange current density on the anode CL, average hydrogen molar concentration on the anode CL, and average oxygen crossover flux are the quadratic function. The empirical degradation model of average activation overpotential on the cathode CL is the quintic function. [ABSTRACT FROM AUTHOR]

To study the effect of component degradation on different degradation indexes of the proton exchange membrane fuel cell (PEMFC), a novel model of the PEMFC based on component properties was established. Firstly, the four main components, namely the proton exchange membrane (PEM), catalyst layer (CL), gas diffusion layer (GDL), and bipolar plate (BP), were selected. Moreover, a model of each component reflecting their properties was established and verified. Secondly, calculations of the component properties at the initial state and 5% changed were conducted. The results showed that the effects of the different components' degradation on the different performance and distribution indexes were different. Considering the nine indexes comprehensively, the influence of component degradation on performance degradation was as follows: GDL > PEM = CL > BP. [ABSTRACT FROM AUTHOR]

Multistack fuel cell systems (MFCS) are promising developments of fuel cell technology. For MFCS, faults affect durability and stability, and appropriate fault diagnosis methods and control strategies need to be proposed for different multistack structures. Herein, the integrated MFCS thermal management subsystem (TMS), which is based on the optimized split‐stack approach, is first studied, and its possible sensor and actuator faults are analyzed. The sensor fault signal is corrected based on the unscented Kalman filter (UKF), the controller design under the hardware in the loop platform is carried out, and an active fault‐tolerant control (FTC) strategy based on sliding mode control is deployed for the TMS to enable it to recover its performance quickly and effectively in case of faults. The results show that the estimated values are closer to the true values after using the UKF on the sensor signals, avoiding the impact of sensor faults on the system performance. Under New European Driving Cycle dynamic conditions, the FTC controller also exhibits better control compared to the conventional proportional–integral controller, with smaller maximum overshoot and shorter system recovery and stabilization time in the event of a TMS fault, mitigating the impact of system fault on performance. [ABSTRACT FROM AUTHOR]

To examine the effects of the inlet temperature on a proton exchange membrane fuel cell (PEMFC), this study proposes a dynamic temperature (DT) model by considering the dynamic variation in temperature that influences the water content of the cell and its performance. A three-dimensional model featuring the geometry and nonconformal mesh of the PEMFC is first formulated. An experiment was then conducted featuring a 34-cm2 single-cell and test system. Following this, a simulation and another experiment were carried out at a working temperature of 333 K with 100% relative humidity (RH) at inlet temperatures of 316 K, 323 K, and 328 K (at 50%, 60%, and 80% RH, respectively). The contours, which included hydrogen in the channels and water in the membrane, were then described. The results show that the proposed DT model can more accurately predict the performance of the PEMFC than the FLUENT model. In particular, when the inlet temperature was 328 K (80% RH), the maximum relative difference between the DT model and FLUENT was 13.8% compared to the results of the experiment. The hydrogen content in the channels decreased and the water content in the membrane increased as the reaction continued. The proposed model provides a new means for studying the effects of dynamic temperature on the PEMFC. [ABSTRACT FROM AUTHOR]

A three-dimensional and isothermal anode relative humidity (ARH) model is presented and used to study the anode inlet humidity effects on the fastest power attenuation single cell in a vehicle fuel cell stack. The ARH model is based on the phenomenon that the anode is more sensitive than the cathode to water flooding. The pressure drop is considered in the ARH model, and saturation pressure is established by a pressure drop. Based on the pressure drop and relative humidity, simulations and tests are completed. First, the geometric model and computational grids are established, based on real structure of the proton exchange membrane fuel cell (PEMFC). Second, single cell distribution in the stack, test schematic and experimental conditions are demonstrated. Finally, polarization curves with 10 cells are displayed and discussed under these conditions that working temperature 70 °C, and diverse relative humidity (40%, 55%, 70%, 85%, and 100%). The test results of 34 cm2 fuel cell stack are compared against simulation results. The results show that C10 (the single cell with the farthest distance from the gas inlet) power attenuation is the fastest and that its performance is the poorest under the experimental conditions. The polarization curves predicted by the ARH model indicate fairly good coherence with the experimental results, compared against the Fluent original model. The ARH model calculation deviation is 28% less than the Fluent model at 360 mA·cm−2 for a relative humidity of 85%. The current density distribution is almost uniform, and membrane water content is negatively affected by high humidity. [ABSTRACT FROM AUTHOR]

• The detailed advances in the multi-stack fuel cell system (MFCS) are reviewed. • The advantages of MFCS are presented compared with single fuel cell stack. • The scientific challenges and prospects for MFCS are suggested. • The synergy between ICEs and MFCSs is the core idea to develop the MFCS. To achieve carbon emission reduction and energy structure upgrading, the proton exchange membrane (PEM) multi-stack fuel cell system (MFCS) is an option to meet high-power demands in application scenarios. However, several barriers of the PEM MFCS have not been solved. This paper is aimed to summarize existing information and propose future R&D potentials. Firstly, detailed R&D activities and advances related to PEM MFCSs are reviewed including applications and design principle, architectures (fluidic, electrical, and thermal), power management strategy (PMS), water and thermal management, degraded mode operation, lifetime, efficiency, and hydrogen consumption. Among them, applications and design principle include application scenarios and influencing factors. Moreover, the architecture determination for MFCSs is the core issue, directly affecting the PMS, water and thermal management, degraded mode operation, lifetime, efficiency, and hydrogen consumption. It is noted that a MFCS is better than a single fuel cell system (SFCS) in fields of the lifetime, efficiency, and hydrogen consumption. Furthermore, the synergy between internal combustion engines (ICEs) and MFCSs is proposed to be applied for the MFCS R&D. Secondly, scientific challenges and prospects are presented, including effects of the load power-sharing on the lifetime and efficiency, comparisons of the performance, efficiency and lifetime, and control issues. Finally, the difference of several aspects is discussed, including the architecture, redundancy, lifetime, and PMS between a PEM MFCS and a PEM SFCS. [ABSTRACT FROM AUTHOR]