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This study introduces a multi-scale convolutional neural network (MCNN) for diagnosing various faults in proton exchange membrane fuel cell (PEMFC) systems. Using simulated fault data from a 240 kW PEMFC stack, the MCNN method is validated. Compared to traditional methods like backpropagation neural network (BP), support vector machine (SVM), and temporal convolutional neural network (TCNN), MCNN achieves an average accuracy of 96.31%, outperforming BP (88.88%), SVM (90.67%), and TCNN (93.80%). The study demonstrates MCNN's effectiveness in diagnosing recoverable faults, fatal faults, and multiple faults in PEMFC systems, achieving fault diagnosis accuracies of over 97%. By leveraging its inherent advantages such as multi-channel processing, automatic feature learning, and parameter sharing, MCNN provides an effective solution for accurately diagnosing faults in PEMFC. The utilization of these advantages has enabled MCNN to perform efficient and accurate fault diagnosis in PEMFC systems. • MCNN achieves 96.31% accuracy, surpassing BP, SVM, and TCNN in diagnosing faults. • MCNN achieves over 97% accuracy in categorizing recoverable, fatal, and multiple faults. • MCNN provides swift and accurate fault diagnosis in PEMFC systems. [ABSTRACT FROM AUTHOR]

Working temperature is a critical parameter that influences the performance of proton exchange membrane fuel cells (PEMFCs). Appropriate thermal management can improve the efficiency of PEMFCs and prevent irreversible internal damage such as membrane degradation. To solve the slow response and poor dynamic performance of traditional temperature control strategies, the dynamic temperature mode of PEMFCs is established and a temperature control strategy based on the sparrow search algorithm-proportional integral differential (SSA-PID) is proposed in this study. The performance of the SSA-PID temperature control is verified by the simulations of current step change, vehicle dynamic load, and working parameter variation. The results show that the proposed method has the advantages of fast convergence, better dynamic performance, and anti-disturbance ability. The maximum power density of the SSA-PID temperature controller is 6.58% and 12.94% higher than GA (genetic algorithm)-PID and traditional PID controllers, respectively. Moreover, the proposed method can ensure temperature fluctuations within 0.5 K under dynamic disturbance. • The PEMFC temperature control strategy based on sparrow search algorithm is proposed. • The performance of the temperature control strategy under external disturbance is discussed. • The proposed control method is compared with the GA-PID and traditional PID controllers. • The proposed method can ensure temperature fluctuations within 0.5 K. [ABSTRACT FROM AUTHOR]

This study presents a hybrid power generation system that combines a proton exchange membrane fuel cell (PEMFC) and an internal combustion engine (ICE), utilizing ammonia decomposition as the primary fuel source. The system comprises various components, including an ammonia decomposition subsystem, PEMFC, ICE, heat exchanger, solenoid valve, and power electronic converter. The research focuses on evaluating the system's performance by analyzing the impact of key thermodynamic parameters, such as decomposition temperature and separation ratio, as well as economic factors like ammonia and hydrogen prices, and service life. The findings reveal that the hybrid power generation system achieves a maximum output power of 16.23 kW and an efficiency of 50.28 %. Furthermore, it is observed that when the power ratio (α) between PEMFC and ICE is set to 1.2, the system achieves optimal electric power output. The levelized cost of energy (LCOE) for the system is calculated to be 0.0774 $ kWh−1 when the ammonia price is 0.35 $ kg−1. Additionally, the system exhibits a significant reduction in greenhouse gas (GHG) emissions, with an estimated decrease of 4.39 × 107 g. The hybrid power generation system has excellent thermodynamic, economic, and environmental performance, which lays a foundation for promoting the spread of high efficiency and zero pollution distributed hybrid power generation system. • A novel hybrid power system of PEMFC and ICE based on ammonia decomposition is presented. • The effects of thermodynamic and economic factors on the system performance are investigated. • The maximum power and efficiency of the system are 16.23 kW and 50.28 % respectively. [ABSTRACT FROM AUTHOR]

Data on long-term tenofovir alafenamide (TAF) therapy for pregnant women with active chronic hepatitis B (CHB) (immune clearance and reactivation phases, currently and previously diagnosed) and their infants are lacking. Pregnant women with active CHB treated with TAF and tenofovir disoproxil fumarate (TDF) were enrolled in this multicenter prospective study, and infants received immunoprophylaxis. The primary outcomes were rates of adverse (safety) events in pregnant women and defects in infants and fetuses. The secondary outcomes were virologic responses in pregnant women, infants' safety, hepatitis B surface antigen (HBsAg) status, and growth conditions. One hundred three and 104 pregnant women were enrolled and 102 and 104 infants were born in the TAF and TDF groups, respectively. In the TAF group, the mean age, gestational age, alanine aminotransferase level, and viral loads at treatment initiation were 29.3 years, 1.3 weeks, 122.2 U/L, and 5.1 log 10 IU/mL, respectively. TAF was well-tolerated, and the most common adverse event was nausea (29.1%) during a mean of 2 years of treatment. Notably, 1 (1.0%) TAF-treated pregnant woman underwent induced abortion due to noncausal fetal cleft lip and palate. No infants in either group had birth defects. In the TAF group, the hepatitis B e antigen seroconversion rate was 20.7% at postpartum month 6, infants had normal growth parameters, and no infants were positive for HBsAg at 7 months. The TDF group had comparable safety and effectiveness profiles. TAF administered throughout or beginning in early pregnancy is generally safe and effective for pregnant women with active CHB and their infants. [Display omitted] [ABSTRACT FROM AUTHOR]

Two geometrical parameters, amplitude and wavelength, of the structure of the wavy-flow field in a proton exchange membrane fuel cell (PEMFC) were investigated on their impacts on cell performances via a three-dimensional, multiphase, and non-isothermal model. Amplitude and wavelength significantly influence oxygen transport, friction resistance, and current densities in PEMFC operations. The enhancement of current density peaks at an amplitude of 0.4 mm and a wavelength of 2 mm, increased by 10.40% compared to the non-wavy design. The wavy channels would increase the oxygen concentration gradient and the viscous friction, increasing entropy generation. The entropy generation rates increase more significantly at small wavelengths and large amplitudes. The entropy generation ratio (EGR) evaluates the performances of different wavy channels based on the accurate description of oxygen transport in PEMFC without calculating the associated pumping power consumption rates. The EGR decreases with decreasing wavelength or increasing amplitude. • Entropy generation by mass transport and friction is greatly influenced by flow field types. • The entropy generation analysis is introduced to verify the superiority of flow fields. • EGR is proposed for the evaluation of oxygen transport under unequal pumping power consumptions. [ABSTRACT FROM AUTHOR]

In this study, a kW-grade air-cooled proton exchange membrane fuel cell (PEMFC) stack with a dead-end anode (DEA) operation is designed and manufactured. The gravity-assisted drainage principle is applied for the stack to design the wettability of gas diffusion layers (GDLs) and the anode channel geometry, which can help the liquid water that diffuses to the anode to drain out of the anode porous electrode and move down the anode channel outlets. As a result, the stack can stably operate in a long purge interval of 268 s and in a short purge time of 2 s. In addition, using this design, only four small-power fans are employed to pump air to the cathode to provide oxygen for the electrochemical reaction and cool the stack. With a constant load current of 30, 45, or 60 A, the stack output voltage is experimentally tested at various cathode air flow rates (CAFRs). The local temperatures (60 measurement points) inside the stack and the pressure differences across anode channels are also monitored to understand heat dissipation and the back diffusion of liquid water. In a wide range of operating conditions, the designed stack possesses superior and stable voltage output characteristics with relatively uniform temperature distributions. The measured maximum output power is 3.83 kW, and the parasitic powers of fans are only 80∼112 W. • A kW-grade air-cooled PEMFC system under dead-ended anode operation is designed. • The effect of cathode air flow rate on dynamic temperature evolution is studied. • Modified anode channels based on gravity drainage are applied to the cell system. • A stringing fan arrangement is used to improve cooling efficiency. [ABSTRACT FROM AUTHOR]

• The performances of parallel and interdigitated flow field PEMFCs with wavelike GCs are discussed. • The effect of curved MEAs on output current densities is investigated. • The oxygen transport and liquid water removal are greatly influenced by curved MEAs. • The normalized oxygen distribution uniformity and oxygen transport resistance are analyzed. The effect of curved membrane electrode assemblies (MEAs) on performances of parallel and interdigitated flow field PEMFCs with wavelike gas channels (GCs) are for the first time investigated at various curved MEA deformation levels, where the curved MEA is triggered by the pressure difference between anodes and cathodes. The results show that on the cathode side of parallel flow field PEMFCs with wavelike GCs, the oxygen consumption and liquid water generation are small with the increased MEA deformation level at the high operation voltage being larger than 0.8 V, leading to the constant cell performance, that is, leading to the constant output current density. However, the current density is first increased and then decreased with the increased MEA deformation level at the low operation voltage being less than 0.8 V. Because at the low operation voltage, the oxygen consumption and liquid water generation are significantly increased and affected by the increased MEA deformation level. When the MEA deformation level is increased at the high operation voltage being larger than 0.8 V, the current density of interdigitated flow PEMFCs with wavelike GCs is also constant because of small oxygen consumptions and liquid water generations. However the oxygen consumption and liquid water generation are large enough and depend on the oxygen transport and liquid water removal at the low operation voltage being less than 0.8 V. At the low voltage, the oxygen transport and liquid water removal are modified by the increased MEA deformation level. Consequently the current density is first decreased and then increased at the low operation voltage. [ABSTRACT FROM AUTHOR]

• The effects of cathode GDL thickness on cell performances are studied numerically. • The steady-state and load-varying conditions are both considered. • A principle of selecting the optimal GDL thickness is proposed. This work proposes a design principle of the optimal thickness for cathode gas diffusion layers (GDLs) of proton exchange membrane fuel cells (PEMFCs) based on a balance of cell performances under both steady-state and load-varying conditions. Using a three-dimensional and two-phase model, the effects of cathode GDL thickness (50, 100, 200, and 400 μm) on steady-state performances and transient response characteristics are studied. The results show that under steady-state conditions, an extremely thin cathode GDL would lead to non-uniform oxygen and liquid water distributions, whereas an especially thick cathode GDL would increase oxygen transport resistance. Thus, there is an optimal cathode GDL thickness, yielding the best steady-state performance. A current overshoot phenomenon, arising from high local oxygen concentrations at cathode catalyst layers (CLs), is observed when the load voltage decreases abruptly. Thinner cathode GDLs would weaken the overshoot and shorten the recovery time of current density. Conversely, low local oxygen concentrations at cathode CLs caused by high liquid water saturation levels lead to a current undershoot phenomenon when the load voltage increases abruptly. Thinner cathode GDLs would strengthen the undershoot but shorten the recovery time of current density. The optimal choice of cathode GDL thickness should weigh up the steady-state and the transient performance. Based on this principle, the optimal cathode GDL thickness is selected as 100 µm. [ABSTRACT FROM AUTHOR]

In this study, a novel cathode flow field plate with additional tapered oblique fin (OF) channels is proposed for air-cooled proton exchange membrane fuel cells (PEMFCs) to promote their heat dissipation and output power. Air-cooled PEMFC stacks with conventional (parallel configuration) and novel flow fields are respectively manufactured and experimentally tested under various load currents. The performance and temperature distributions of the stacks are comparatively studied in detail. Besides, a three-dimensional and two-phase numerical model is established and validated by the experiment data to further comparative investigate the heat and mass transport mechanism of the two studied flow field designs. The results show that the stack with the novel flow field has higher output power, which is 4.87% higher than that with a conventional design at a load current density of 0.55 A cm−2. Due to the forced convection and secondary vortex phenomena in the OF channels, the local overheating in the porous electrode is relieved. Moreover, the entropy generations due to heat transfer of the cathode CL and cooling channels are significantly increased. The oxygen transport under cathode ribs is also noteworthily enhanced when the OF channels are adopted. • An air-cooled PEMFC stack with tapered oblique fin channels is designed and fabricated. • Tapered oblique fin channel design enhances stack performance and heat dissipation. • Local multi-physics fields inside the PEMFC are studied by numerical methods. • Mass transport and thermal behaviors inside the air-cooled PEMFC are optimized. • Entropy generation due to mass transport and heat transfer is studied for the PEMFC. [ABSTRACT FROM AUTHOR]