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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 membrane electrode assembly (MEA) of a proton exchange membrane fuel cell (PEMFC) would deform when there is a pressure difference between the cathode and anode. In this study, a three-dimensional PEMFC model that incorporates a two-dimensional MEA deformation model is employed to investigate the effects of the curved MEA on oxygen transport, liquid water removal, pressure drops across cells, and resulting overall cell performances. The results show that the MEA deformation generates a gap between the rib and gas diffusion layer (GDL), thereby enhancing the oxygen transport into and liquid water removal from the cathode porous electrode. At an operating voltage of 0.4 V, the output current density is enhanced by 4.83%, 6.67%, and 8.61%, respectively, for the pressure differences of 10, 20, and 30 kPa between the cathode and anode, as compared with that without a pressure difference. An efficiency evaluation criterion (EEC) that represents a tradeoff between mass transfer enhancement and pressure drop penalty is introduced to evaluate the overall cell performance enhancement. The result shows that the EEC value increases with increasing the pressure difference between the cathode and anode, confirming the performance enhancement by the deformed MEA. In addition, the effects of MEA deformation are also examined at two sets of channel heights (H) and widths (W), i.e., W H =0.5 mm and W H =1.5 mm. At an operating voltage of 0.4 V, the output current density is enhanced by 20.18% at a pressure difference of 30 kPa for the cell with W H =0.5 mm, whereas it is improved only by 2.91% for the cell with W H =1.5 mm. Therefore, increasing the pressure difference between the cathode and anode is a more effective approach to performance enhancement for the cell with a small channel height and width. • The MEA deformation caused by cathode and anode pressure differences is studied. • A gap is generated between the bipolar plate and deformed MEA. • Oxygen transport and liquid water removal are enhanced by the gap. • Cell performances are improved by the deformed MEA. [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]