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As an efficient energy converter, the proton exchange membrane fuel cell (PEMFC) is developed to couple various applications, including portable applications, transportation, stationary power generation, unmanned underwater vehicles, and air independent propulsion. PEMFC is a complex system consisting of different components that can be influenced by many factors, such as material properties, geometric designs operating conditions, and control strategies. The interaction between components and subsystems could affect the performance, durability, and lifespan of PEMFC system. To design a high performance, long lifespan, high durability PEMFC, it's essential to comprehensively understand the coupling effect of different factors on the overall performance and durability of PEMFCs. This review will present existing research on basis of four aspects, involving fuel cell stack design, subsystems design and management, mass transfer enhancement, and system integration. Firstly, the multi-physics intergradation and component design of PEMFC are reviewed with the designing mechanisms and recent progress. Besides, mass transfer enhancement methods are discussed by bipolar plate design and membrane electrode assembly optimization. Then, water management, thermal management, and fuel management are summarized to provide design guidance for PEMFC. The specifications design and system management for various engineering applications are briefly presented. • The key components, systems, control strategy of PEMFC were reviewed in terms of theory and model. • The guideline for designing a high performance, long lifespan, high durability PEMFC was provided. • Different applications and system of PEMFCs were expressed by drawing extension. [ABSTRACT FROM AUTHOR]

Summary: Proton exchange membrane fuel cell (PEMFC) generates a lot of heat during power generation. It is necessary to control PEMFC to operate at proper temperature through effective thermal management. CFD model of flow field plates with different structures is established; the heat transfer performance of different flow fields was analyzed by numerical simulation. The index of uniformity temperature (IUT) was introduced to further evaluate the heat transfer effect. The results showed that the parallel flow field was not suitable for cooling due to its poor performance at high coolant flow rate. The pressure difference of serpentine flow field was more than 10 times that of other flow fields, which lead to the highest cost in practical cooling application. The wave flow field with the best comprehensive cooling effect at high flow velocity, and the average temperature and IUT were 2.22% and 37.97% lower than the parallel flow field, respectively. The cooling effect of point flow field followed the second, and its average temperature and IUT were 1.65% and 29.71% lower than those of parallel flow field, respectively. In practice application, the wavy flow field showed better heat transfer performance within the required coolant flow range. [ABSTRACT FROM AUTHOR]

Summary: The lumped parameter model of the hydrogen system based on exhaust hydrogen recirculation and the CFD model of PEMFC stack were established in this paper. The system simulation results were used as the input of the stack model. The purge characteristics of the stack were studied and the purge strategy was formulated considering the hydrogen utilization and performance characteristics. The results show that during anode purging, the anode pressure fluctuated significantly and the nitrogen concentration decreased rapidly. The output voltage of the stack fluctuates greatly, and the fluctuation of voltage intensifies with the extension of emission duration. In addition, the voltage fluctuation range of unit cell decreases gradually from inlet to outlet. After the system stabilizes, the component distribution of anode was improved and the stack performance was recovered to the initial state. During the purge interval, the performance of the stack degrades due to the increase of anode nitrogen concentration. The hydrogen utilization rate of the hydrogen system was directly related to the purge strategy, and the purge strategy of short period‐short duration was beneficial to reduce the fluctuation of the stack performance in the purging process, and reduce the differences of performance and component distribution of different single cell. [ABSTRACT FROM AUTHOR]

Summary: Experimental and numerical studies are the main methods to obtain the polarization curves of proton exchange membrane fuel cell (PEMFC) stack for the application of balance of plant (BOP) selection, system matching, and controller design. A novel methodology of polarization curve fitting for PEMFC is proposed based on genetic algorithm, and a rated power of 62 kW fuel cell stack is used for identification experiments. The exchange current density and charge transfer coefficient are selected as optimization variables. The results show that the two optimization variables can effectively replace the four empirical parameters in the calculation of activation overpotential and demonstrate good agreement between the proposed model and experimental data within 3% error. In addition, a group of polarization curves is obtained by considering the relationship between the exchange current density and reactant concentration, activation energy, and temperature, which is of great significance in the engineering application of PEMFC for quick and accurate control. Furthermore, a dynamic model is also used to investigate the transient response of PEMFC, and the simulation results show a transition region of voltage drop at step current densities, coinciding with the experimental data and indicating the reliability of the method for polarization curve fitting. [ABSTRACT FROM AUTHOR]

Summary: Carbon corrosion in the catalyst is an important factor limiting the lifetime of proton exchange membrane fuel cells (PEMFCs). The water distribution inside the PEMFC directly determines the carbon support's corrosion rate in the catalyst. This study first investigates the water mole fraction distribution in the catalyst under different operating conditions, such as relative humidity (RH), temperature, pressure. It then divides the catalyst into different flooded areas according to the relationship between the water vapor partial pressure and saturated vapor pressure. Finally, it investigates the carbon corrosion characteristic of each region. The carbon corrosion of the catalyst is mainly divided into the corrosion in the non‐flooded area and the corrosion in the flooded area. The results show that the decay rate of carbon support is around 4% after 5000 hours of operation in the non‐flooding area. However, the degradation of the carbon support in the flooded area after 100 hours is as high as around 97.76%. Therefore, how to avoid flooding is the important issue that needs to be considered in the PEMFC. Moreover, increasing the pressure and RH promote the carbon corrosion in both cases, while increasing the temperature increases the carbon corrosion reaction rate, but it is beneficial to alleviate water flooding. Highlights: Water distribution and carbon corrosion under different working conditions.Divide the catalyst into varying levels of flooded areas.The carbon corrosion degree in the flooded area is as high as 97.76% after 100 hours.Increasing temperature increases the corrosion rate, but alleviates water flooding. [ABSTRACT FROM AUTHOR]

Buildings account for most of the greenhouse gas (GHG) emissions causing global warming. The development of eco-neighborhood can improve the energy efficiency of buildings and reduce GHG emissions. A combined heat and power (CHP) system based on proton exchange membrane fuel cells (PEMFCs) is designed to supply electricity and thermal for eco-neighborhood in North China with low GHG emissions. Effects of different inlet parameters, such as PEMFC inlet pressure and current density, on multi-stack CHP system performance are discussed. Coupled with a dynamic load scenario, the adaptability of the designed PEMFC-CHP system is studied through PI control with an electricity-led strategy and a thermal-led strategy. Both strategies can effectively reduce GHG emissions and the eco-neighborhood with PEMFC-CHP system is more environmental friendly compared to conventional energy supply. The electricity-led strategy can satisfy the energy consumption of the eco-neighborhood but with thermal waste. The energy consumption for most of the time during a year can be satisfied by the PEMFC-CHP system under the thermal-led strategy, but the electricity gap exists as the thermal demand is lower. Under the electricity-led strategy, the GHG emission reduction of the eco-neighborhood under electricity-led strategy and thermal-led strategy are around 7000 ton and 5000 ton per year, respectively. [Display omitted] • MW PEMFC-based combined heat and power system is developed for an eco-neighborhood. • Electricity-led and thermal-led strategy are discussed to couple energy consumptions. • The GHG reduction of the eco-zone under electricity-led is around 800 ton per year. [ABSTRACT FROM AUTHOR]

Summary: Water management is an important issue to be addressed to maintain the stable and efficient operation of a proton exchange membrane fuel cell (PEMFC). Gas purging is commonly performed to remove accumulated water in a PEMFC, especially in a dead‐ended fuel cell system. A 3D dynamic model with a user‐defined inlet boundary condition is proposed to study the effect of gas purging with different purge durations in an H2/O2 PEMFC. The results show that the performance immediately deteriorates and then recovers to the original level during gas purging. Purging has a significant effect on the flow and mass transfer in the flow channel, and it leads to efficient removal of water from the PEMFC. The voltage variation tendency is consistent with the water content of the membrane. Membrane dehydration is the main reason for the performance degradation. Notable variations could be observed with increments in the purge duration. Water in a PEMFC is more sensitive and responsive to changes of operating conditions than the reactants. In addition, the performance is significantly deteriorated at a higher operating temperature. A large amount of water is removed during the gas purging, resulting in low water content in the membrane and low water saturation at the interface between the flow channel and the gas diffusion layer. [ABSTRACT FROM AUTHOR]

In this study, a three-dimension (3D) computational model was proposed to investigate the flow and heat transfer characteristics of the intake grilles of two different fuel cell vehicles. The models of the intake grilles were constructed according to the actual sizes of two vehicles, namely, Roewe 950 and Toyota Mirai, considering the heat dissipation unit to simplify the heat transfer model of the vehicle. The results showed that relative to Roewe 950, Mirai intake air flow rate was approximately 10% higher, the heat transfer capacity was approximately 7% higher, and the intake grille area was larger. The coolant outlet temperature of Mirai was lower than that of Roewe 950, which was beneficial for the long term and stable operation of a fuel cell. This comparative study provided guidance for the intake grille and radiator design of fuel cell vehicles. The only difference between fuel cell vehicles on the market and conventional vehicles was that in the former, the internal combustion engine was replaced with a fuel cell stack, which had insufficient heat transfer capacity because of the reducing temperature difference. Increasing the intake grille area and the heat exchange capacity of the radiator were the key issues for the development of fuel cell vehicles. In this study, an optimal window opening angle of the radiator fin of 23° provided a maximal heat transfer coefficient. [ABSTRACT FROM AUTHOR]

In this study, we investigate the temperature characteristics of a proton exchange membrane fuel cell (PEMFC) stack applied to a combined cooling, heating and power (CCHP) system for achieve a suitable operating temperature range of PEMFCs and meeting the requirements associated with the heat source temperature of the CCHP system. The functional relationships between the current density, cooling water flow rate, number of single cells, PEMFC temperature, and the cooling water outlet temperature in stacks composed of 5–30 single cells are analyzed. There is a current density interval for each cooling water flow rate that meets the requirements of both the PEMFC and cooling water outlet temperature, which decreases with an increase in the cooling water flow rate. The coefficients of determination (R2) of the equations are all greater than 0.997. The reliability of the equations is verified on a stack composed of 50 single cells, and the error between the predicted and actual results is less than 0.5%. Based on empirical equations, the recommended cooling water flow rate interval is obtained at each current density, and the recommended operating current density should be less than or equal to 1.1 A·m−2. • The empirical equations of the PEMFC stack temperature characteristic are derived. • The error between the predicted and actual results is less than 0.5%. • The cooling water flow rate interval is obtained at each current density. • The recommended operating current density should be less than or equal to 1.1 A·m−2. [ABSTRACT FROM AUTHOR]

Understanding the internal water distribution in proton exchange membrane fuel cell (PEMFC) is critical to the development of high-performance PEMFCs. In this study, the cathode flow field is divided into 9 areas, and the relative humidity under different conditions is measured in-situ by using microsensors embedded in the cathode flow field plate. Polarization curves are measured and electrochemical impedance spectroscopy is carried out under different conditions. The results show that the relative humidity has a significant effect on the internal resistance of PEMFCs. When the inlet gas is not humidified, too high of a temperature will lead to low relative humidity and membrane dehydration. Increasing pressure and cathode humidification can alleviate this problem. However, the relative humidity of the outlet area is close to 100% when the cathode back pressure is 100 kPa, and a too high relative humidity will result in flooding in the cathode channel. Moreover, the degree of corrosion of the carbon support in the catalyst is closely related to the water concentration in the cathode, and the water management downstream of the flow field is particularly important. • The cathode water distribution was measured in-situ by using microsensors. • The relative humidity has a significant effect on the internal resistance of PEMFCs. • The catalyst carbon corrosion is closely related to the cathode water concentration. • Special attention should be given to water management downstream of the flow field. [ABSTRACT FROM AUTHOR]

The design of bipolar plates is critical for improving the performance of proton exchange membrane fuel cells (PEMFCs). In this research, a new additional outlet based on a PEMFC's parallel flow field was proposed, and three different positions of outlet were designed on the target side of gas flowing in parallel channels. The results revealed that the additional outlets are able to increase the gas speed through channels near the additional outlets, which results in a lower water saturation and a more uniform distribution of oxygen concentration at the interface between the catalyst layer (CL) and gas diffusion layer (GDL). With the variation of the outlet position in the target side, it was found that the additional outlet set in the middle of the target side exhibits the highest increase of peak power density, namely, 13%. Furthermore, the optimal position of the additional outlet was proved to be suitable for PEMFCs with various active surface areas, indicating the universality of the present results in the study. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the causes and consequences of the carbon corrosion mechanism and summarizes the corresponding mitigation strategies for various operating conditions. The high potential at the cathode caused by the anode hydrogen-oxygen interface leads to the occurrence of carbon corrosion reactions during the startup and shutdown process. System strategies, including gas purge and auxiliary load, have been developed to alleviate the performance decay during startup and shutdown processes. Improper water management will cause local flooding to accelerate the carbon corrosion. Many novel flow fields have been proposed to solve water management problems, such as an optimized 3D flow field, baffle flow field and porous media flow field. The carbon corrosion under normal operation is not as serious as that under start-up and flooding, but it is serious enough to affect the later performance of the PEMFC after long-term operation. Varieties of new supports, such as mesoporous carbon, graphitized carbon, carbon nanotubes (CNTs), carbon nanofibers (CNF), and metal oxides, have been developed to improve the durability of the catalyst support. This review aims to provide a clear understanding of the carbon corrosion mechanisms, thereby helping researchers to prolong the lifetime of PEMFCs. Carbon corrosion in three operating conditions. Image 1 • An overview of carbon corrosion mechanism under three conditions was addressed. • Corresponding mitigation strategies for carbon corrosion were presented. • Future goals of mitigation strategies about carbon corrosion were suggested. [ABSTRACT FROM AUTHOR]

• Synergetic regulation related to mass transfer is necessary for PEMFC design. • Sherwood and Euler number was proposed to evaluate the superiority of flow field. • Pressured parallel flow field presents better performance and uniform water and gas distribution. Flow field plays an important role in the design and application of proton exchange membrane fuel cell (PEMFC). The superiority of flow field is commonly evaluated by comparing the performance improvement of PEMFC. However, it's necessary to decrease the flow resistance to reduce the parasitic power and to obtain more uniform water and gas distributions during operation. As a consequence, the combined effect of performance and resistance should be considered during the optimal design of flow channel in PEMFC. A new criterion of efficiency evaluation criterion (EEC) using Sherwood number and Euler number has been proposed to evaluate the relationship between the mass transfer and the pressure drop in this study. The performances of PEMFCs with parallel, single-serpentine, and pressured parallel flow fields are investigated in detail. The results show that PEMFC with single-serpentine flow field has a better performance under normal atmospheric pressure, while the pressure drop in cathode is much larger than that in the parallel flow field. The pressured parallel flow field presents better performance and uniform gas distribution and it is thus proposed as the flow channel in the application of PEMFC. [ABSTRACT FROM AUTHOR]

Air-cooled fuel cells used in portable stacks are required to reduce the size and weight while ensuring a high-power output. In this study, the 0.1 mm stainless steel sheet was used to form the ultrathin bipolar plates (BPs), by the reasonable flow field design and material selection, the mass of single bipolar plate is as low as 44.6 g and the thickness is only 1.9 mm with 180 cm2 active area. The 2.8 kW air-cooled stack has efficient heat dissipation, small voltage over/undershoot, rapid temperature dynamic response, and compact structure, moreover, the mass of the stack core is 3203 g and the volume of the stack is 3.36 L. The designed stack has an excellent voltage consistency, fast temperature response, and high power density. The maximum voltage overshoot is 0.035 V with a current step/drop of 10 A. The maximum temperature drop rate reaches 0.12 K s−1 in a 10% fan duty cycle step when the load current is 72 A. At 50% fan duty cycle, the temperature increase rate reaches its peak of 0.27 K s−1 when the load current steps from 70 A to 80 A. The mass power density of the designed air-cooled 56-cell stack is 0.885 kW kg−1 and the volumetric power density is 0.751 kW L−1. • Single cell thickness is 2.05 mm using ultra-thin gold coating BPs. • Mass power density of the designed stack is 0.885 kW kg−1 • Volumetric power density of the designed stack is 0.751 kW L−1 • The maximum temperature increase rate reaches 0.27 k s−1. [ABSTRACT FROM AUTHOR]

Flow channel optimization is an important method to improve the water-gas transport capacity and enhance the performance of proton exchange membrane fuel cells. In this study, the size ratio of the opposite sinusoidal wave flow channel (OSWFC) is optimized, and three-dimensional numerical models are developed to evaluate the comprehensive performance. The results show that OSWFCs obtain performance enhancement compared to the parallel flow channel. 1:1 wave channel has a maximum improvement of 19.53% in mass transfer capacity by the most frequent flow disturbance, while 1:3 has a maximum increasement of 37.5% in water removal performance by the virtue of gentle wave structure. Large pressure loss decreases the mass transfer efficiency, although it with the maximum mass transfer capacity, the mass transfer evaluation criterion of 1:1 wave channel is less than that of 1:3. Moreover, a significant correlation between water-gas transport capacity and electrochemical performance is demonstrated by Pearson correlation coefficient. [Display omitted] • The OSWFC has a significant performance enhancement at high current densities. • The wave flow channel with ratio of 1:1 has the best mass transfer capacity. • The wave flow channel with ratio of 1:3 has the best water removal performance. • MTEC is proposed to evaluate the mass transfer efficiency. • PCC is proposed to evaluate the comprehensive performance of PEMFC. [ABSTRACT FROM AUTHOR]

With the rapid growth in the number of data centers, energy consumption has increased exponentially, and energy conservation has become a focus of data center applications. Owing to the different ambient conditions in different regions, this study proposed novel integrated power and hybrid cooling systems driven by PEMFC. Multiple cooling methods were investigated to make full use of the waste heat generated by PEMFC and natural cold sources. Three types integrated systems, including a basic combined cooling and power (BCCP) supply system, a heat pipe combined cooling and power (HPCCP) supply system, and an outdoor air combined cooling and power (OACCP) supply system were constructed. Five cities representing five climatic regions were selected to compare and analyze the operation characteristics and energy efficiency of the three systems. It is concluded that the values of power usage effectiveness (PUE) in the three systems are 1.16–1.32, and the theoretical energy efficiency is 87.80%–91.08%, which is 11.27%–12.42% higher than the reported value of a commercially used data center in Changping. The energy efficiency of the OACCP system is generally higher than that of the HPCCP system. The HPCCP system is suitable for cold and severely cold climate regions, and the OACCP system is suitable for temperate climate regions. Such findings may provide theoretical basis for the selection of the integrated power and cooling system designed for data centers in different climate regions. However, the theoretical results may need further improvement by including the energy loss during transportation and the efficiency of the converter during power conversion. • PEMFC-CCP systems with multiple hybrid cooling methods for data centers are proposed. • Collaboratively control strategies are designed for fully use natural cold sources. • Annual operation performances are systematically analyzed in five typical climate regions. • The optimal PEMFC-CCP system is selected in different climate regions. [ABSTRACT FROM AUTHOR]

Aiming at the power fluctuation and mismatch of the combined cooling, heating, and power (CCHP) system based on proton exchange membrane fuel cells (PEMFCs) and adsorption chiller, this study proposes a multi-stack coupled power supply strategy. The PEMFC stacks are divided into types Ⅰ, Ⅱ, and Ⅲ to meet the electric load and cooling load of the data center, and the heat requirements of the system. Meanwhile, economic analysis is conducted on the single-stack energy supply strategy and the multi-stack coupled energy supply strategy. The results show that with the multi-stack coupling power supply strategy, the cooling power and electric power almost completely match the load of the data center, without power fluctuations and overshoot. By smoothing the PID control results of the current of the stacks-Ⅲ, the heating power fluctuation is significantly reduced, and the maximum overshoot does not exceed 0.5 kW. Therefore, the strategy is conducive to the stable operation of the PEMFC stack and improves the lifetime of the system. Considering investment costs, maintenance costs, hydrogen costs, and electricity benefits, the multi-stack coupled energy supply strategy can save about 6.1 × 105 $ per year. In summary, the multi-stack coupled energy supply strategy has advantages in system lifetime, operational stability, and economy. • Multi-stack coupled power supply strategy is proposed. • The PEMFC are divided into types Ⅰ, Ⅱ, and Ⅲ to meet different power requirements. • The cooling and electric power completely matches the load with the strategy. • The heating power fluctuation is reduced by smoothing the current of stacks-Ⅲ. • The multi-stack coupled energy supply strategy can save about 6.1 × 105 $ per year. [ABSTRACT FROM AUTHOR]

For data centers with high humidity requirements, a novel combined cooling, heating and power (CCHP) system with dehumidification is proposed, which can provide cooling, heating, electricity and dehumidification simultaneously. The dynamic responses and economic characteristics of three different dehumidification methods with integrated dehumidification wheel, desiccant or parabolic trough solar collector (PTSC) as an auxiliary heat source are analyzed. The results show that the use of desiccant instead of the dehumidification wheel is beneficial to the stability of system power and temperature, and reduces the installed capacity of proton exchange membrane fuel cell (PEMFC) stacks by about 78%, thereby reducing the cost of the stacks and hydrogen. With the assistance of PTSC as an auxiliary heat source, the PEMFC stacks can reduce about 110 kW of electricity and save about 62 kg of hydrogen per day. Taking the average annual cost as an economic evaluation index, when hydrogen price is higher than $0.16 kg−1, using PTSC to assist the PEMFC stacks to provide the heat source is a better choice than using the PEMFC stacks alone. • PEMFC-based CCHP systems with different dehumidification methods are proposed. • The dynamic response and economic characteristics are comparatively analyzed. • Replacing the dehumidification wheel with desiccant can reduce power fluctuations. • When the price of hydrogen is higher than $0.16 kg−1, it is better to add PTSC. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) has been used in supplying power for Unmanned Underwater Vehicle which operate in a closed environment and dead-ended anode and cathode (DEAC) mode is deemed as an effective way to enhance the fuel utilization rate. Catalyst is an important factor that influences the performance and durability of PEMFC, especially in DEAC mode. In this paper, the degradation characteristics of PEMFCs with Pt black and Pt/C catalyst after 100 h operation have been investigated by electrochemical techniques and morphological characterization methods. It's shown that the degradation of Pt black catalyst layer (CL) was more severe than that of Pt/C CL. The difference of performance degradation is due to the dominant decay mechanism of these two catalysts is different. According to SEM, TEM and XPS results, the decay of Pt black catalyst is mainly caused by Pt agglomeration and oxidation, causing a higher ohmic resistance, higher mass transfer resistance and severer degradation of performance. The degradation of Pt/C catalyst is mainly due to the reduction of electrochemical surface area and carbon corrosion because the larger carbon corrosion makes micropores and the thicker supporting structure, resulting in the performance degradation. [Display omitted] • Pt/C catalyst shows better durability than that of Pt black under dead-ended anode and cathode mode. • Severe catalyst degradation occurs at the outlet of cathode. • The decay of Pt/C catalyst was mainly resulted from carbon corrosion. • The decay of Pt black catalyst was mainly caused by the migration and dissolution of Pt particles. [ABSTRACT FROM AUTHOR]

• A novel pressure-based purging PEMFC system in DEAC mode is developed. • The hydrogen and oxygen utilization rates both reach 100%. • The water generated has been collected in this system. Proton exchange membrane fuel cells (PEMFCs) have been wildly used for marine and aerospace applications as energy devices, where pure hydrogen and oxygen are fed into the two sides of the membrane electrode assembly (MEA). The release of unreacted hydrogen and oxygen not only reduces the efficiency of the system but also causes the serious problem of hydrogen starvation. For this reason, fuel flow driving devices and methods such as pumps, ejectors, and solenoid valves are designed to recycle this unused gas. However, even with these devices, the release of gas into the environment is still inevitable. Therefore, this paper introduces a novel method that solves these problems and mitigates gas emissions using a dead-ended anode and cathode (DEAC) system. Pressure difference is formed between the inlet and outlet of PEMFC by controlling the purge valve to remove water and recycle hydrogen during purging. The dynamic response characteristics of this system under different current densities, pressure differences, and purging intervals are experimentally investigated in detail. The results show that both the hydrogen and oxygen utilizations can reach 100% and the collection of generated water during gas purging can be achieved in the DEAC mode. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional multi-phase proton exchange membrane fuel cell (PEMFC) electrochemical model coupled with a cooling channel (CC) was developed, to comprehensively analyze the heat transfer characteristics. The membrane temperature, index of uniform temperature (IUT), net power, and the Nusselt number were applied to evaluate the heat transfer performance. The results indicate that a smaller IUT value achieves better PEMFC performance at close temperatures, and the best performance is achieved with a coolant inlet temperature of 343.15 K. Although increasing the coolant flow velocity improves the cooling effect, thereby enhancing PEMFC performance. However, it inevitably leads to an increase in parasitic power, resulting in a decrease in the output power of the PEMFC system. Moreover, with the coolant temperature difference less than 6K, PEMFC shows better performance when the coolant flow direction is the same as O 2. On the contrary, with the coolant temperature difference greater than 6K, the coolant flow direction should be the same as H 2 to ensure good performance. In addition, with the temperature difference between the coolant inlet and outlet of 10K, 6K, and 3K, respectively, the surface Nusselt number of wavy CC is 5.46%, 8.92%, and 18.71% higher than the straight CC, respectively. • A three-dimensional multi-phase PEMFC electrochemical model coupled with cooling channel is developed. • IUT, net power and Nusselt number are applied to evaluate the heat transfer performance. • The effect of coolant flow direction on performance depends on the flow velocity. • Performance of PEMFC with wave cooling channel is slightly better than that of straight cooling channel. [ABSTRACT FROM AUTHOR]

• Performance of a PEMFC with different anodic/cathodic temperatures was investigated. • Lower anode temperature was better for the performance enhancement of PEMFC. • Performance increased with the increasing of the cathode/anode temperature difference. Thermal management is critical for improving the performance of a proton exchange membrane fuel cell (PEMFC). Operation temperature can directly affect the saturated water vapour pressure and thus the water transport between the anode and cathode in PEMFCs. However, current researches on the effect of operation temperature on the performance are based on convenient design of a joint coolant flow channel for the anode and cathode. Consequently, the independent effect of the temperature on the anode or cathode is ignored. In this study, a single PEMFC with separated coolant flow channels in the anode and cathode is fabricated to investigate the effects of different anode and cathode operation temperatures on the performance. The results show that different anode and cathode operation temperatures could affect the performance of PEMFCs. A lower anode temperature improved the electro-osmotic drag role of water transport from anode to cathode. Hence, the PEMFC performance increased both with the increasing cathode operation temperature and the temperature differences between the cathode and anode. Higher operation temperature improves the activity of the catalyst, and water management and elevated operation pressure affect the kinetics of the electrochemical reaction. Peak performance is obtained through the balance of operation temperature, pressure and water management, particularly for different anode and cathode operation temperatures of PEMFCs. [ABSTRACT FROM AUTHOR]

The rise in cloud computing has promoted the rapid development of the data center industry. Proton exchange membrane fuel cells have high energy conversion efficiency and the potential to be applied in data center applications. In this study, by considering different energy storage devices and multienergy complementarity, four types of proton exchange membrane fuel cell-driven cooling-power systems were designed for data center applications. The effects of different types of energy storage devices and combination of solar energy on the operation characteristics were systematically analyzed. The results indicate that among the four cooling-power systems, the one with heat storage and solar thermal collector provides the best matching between cooling/power supplies and demands. The systems with a heat storage device consumed more hydrogen (3.6%) than those with a power storage device because of the larger requirement of heat (3.8%) and higher current density in the proton exchange membrane fuel cell. Results of emergy analysis show that the cooling-power system with power storage and solar thermal collector reached a maximum environmental sustainability index of 57.610 and a minimum environmental load ratio of 0.018, which imply strong sustainability potential while releasing the lowest pressure to the environment compared to the other systems. • Four types of PEM fuel cell-driven cooling-power systems are designed for data center applications. • Various energy regulation strategies are established for different types of cooling-power systems. • The impacts of different storage devices and multienergy complementary are systematically analyzed. • The emergy analysis is applied to evaluate sustainability related potentials and select optimal system. [ABSTRACT FROM AUTHOR]

• Cathode flow fields of PEMFCs with great water–gas transfer capacity are optimized. • PEMFC obtains 9.30% performance enhancement with the optimal cathode flow field. • Visualization experiment verify water removal advantage and performance benefits. • PCC is firstly proposed to evaluate the correlation of PEMFC performance indexes. Flow field design plays a key role in enhancing the performance of proton exchange membrane fuel cell (PEMFC). In this work, the cathode flow field is optimized to enhance the performance of PEMFC by improving the capacity of mass transfer and water removal, and a three-dimensional, two-phase, isothermal numerical model is established to evaluate its performance. Additionally, visualization experiment is carried out to verify the simulation results. It shows that the opposite sinusoidal wave flow fields (OSWFFs) with single-inlet, dual-inlet and the block provide 6.86%, 1.26%, and 2.31% performance enhancement, respectively, compared with the parallel flow fields (PFFs), which positively affects the mass transfer capacity and water removal performance. Among them, the dual-inlet OSWFF with block is the most helpful for performance enhancement, with an enhancement of 9.30% at 2.2 A cm−2 compared to the PFF. Moreover, Pearson correlation coefficient (PCC) is proposed for the first time to evaluate the correlation between each index and PEMFC performance. The comparison of stoichiometric ratios shows that the more significantly correlated indexes contribute to the dual-inlet OSWFF outperforming the single-inlet OSWFF at high inlet velocities, verifying the applicability of PCC in PEMFC. [ABSTRACT FROM AUTHOR]

A residential combined cooling heating and power (CCHP) system based on proton exchange membrane fuel cell (PEMFC) and solar energy is proposed. This system mainly consists of a PEMFC subsystem, an organic Rankine cycle/domestic hot water (ORC/DHW) subsystem and a vapor compression cycle (VCC) subsystem. The electric power of the system is about 8 kW, and the cooling/heating capacity is 14.5 kW under rated operating conditions. Mathematical models are developed for each subsystem, and their associated costs and CCHP efficiency are estimated based on assumptions made. The effects of current density, operating temperature, solar radiation and ambient temperature are analyzed. The results show that current density, solar radiation and ambient temperature have a significant impact on CCHP efficiency, while the impact of operating temperature is relatively small. CCHP efficiency increases with current density both in summer and in winter, reaching 75.4% and 85.0%, respectively. The efficiency decreases with the increase of ambient temperature in summer, while in the winter it increases. In addition, the CCHP system can reduce to a combined cooling and heating (CCH) system if the PEMFC subsystem is shutdown or reduce to a combined heating and power (CHP) system when the solar radiation intensity is close to zero. [ABSTRACT FROM AUTHOR]

The optimized design of the flow field structure helps to enhance the mass transfer and water removal capacity of the proton exchange membrane fuel cell (PEMFC). A novel opposite sinusoidal wave flow channel is proposed in this study, and the influence of amplitudes and periods of the sinusoidal function on performance of PEMFC is explored by numerical simulation. The research results show that the mass transfer capacity of the opposite sinusoidal wave channel is better than that of the straight channel. By increasing the amplitude, combined with decreasing the period, the mass transfer capacity and the performance of the PEMFC can be effectively enhanced. Compared with the straight channel, for an amplitude of 0.8 mm and a period of 0.5Π mm at 2.0 A cm−2, the net power density is increased by 16.61% and 12.01% respectively. Moreover, based on the volume of fluid model, the transport process and distribution characteristics of liquid water in the straight channel and the opposite sinusoidal wave channel are compared and analyzed. The results show the drainage period of the opposite sinusoidal wave channel is half shorter compared to the straight channel. Therefore, the proposed opposite sinusoidal wave channel has better water removal capacity. • A novel opposite sinusoidal wave flow channel is proposed for performance enhancement. • The influence of amplitudes and periods of the sine function on performance of PEMFC is explored. • The proposed sinusoidal wave channel shows excellent mass transfer and water removal capacity. [ABSTRACT FROM AUTHOR]

• A vehicle PEMFC power system model is established. • The influence of auxiliary equipment energy consumption on fuel cell power system efficiency and total system cost under dynamic conditions is studied. • Thermodynamics-Economy-Environment feasibility under different operating conditions are discussed. Proton exchange membrane fuel cell (PEMFC) has the merits of fast starting speed, zero pollution, high efficiency and high reliability, which is gradually applied to new energy vehicles. In this paper, a vehicle PEMFC power system model is established, which is mainly consisted of PEMFC stack, air compressor, hydrogen circulation pump, cooling water pump and humidifier. The influence of auxiliary equipment energy consumption on fuel cell power system efficiency and total system cost under dynamic conditions is studied. Moreover, the mapping relationship between operating parameters (operating temperature, inlet humidity of anode and cathode) and thermodynamic system performance (electrical power, electrical efficiency, thermal efficiency) is analyzed. The auxiliary equipment energy consumption and system thermal performance output of the vehicle PEMFC system model at the 180-300A step current is obtained. Furthermore, total system cost and pollutant emissions quality under transient response and dynamic operation are estimated. The results show that in a 30 kW vehicle PEMFC system model, the net output power of the system can reach 22.5 kW. The maximum electrical efficiency and thermal efficiency of the system reach 41 % and 52.1 %, respectively. After 2400 h operation, the total system cost reaches 62616$. Wind energy hydrogen production shows the lowest pollutant emission. [ABSTRACT FROM AUTHOR]

This paper presents an innovative, hybrid residential CCHP system based on fuel cell and solar technologies that can provide electric power, heating and cooling. The CCHP system consists of a proton exchange membrane fuel cell (PEMFC) stack, parabolic trough solar collector (PTSC), double-effect absorption chiller and their relevant accessories. The effects of key operating parameters for PEMFC and PTSC systems (e.g.: current density, operating temperature and solar radiation) on the system thermodynamic performance are analyzed and discussed. The results show that the PEMFC operation temperature has a significant influence on the PTSC output performance in a hybrid CCHP system and that the PTSC also plays an important role as a bridge between the PEMFC stack and absorption chiller. The maximum efficiency of a hybrid system can reach 80.5%, which is higher than conventional CCHP systems, due to the high efficiency of PEMFC, PTSC and double-effect absorption chiller. The economic and environmental analysis of CCHP system are also performed, the results indicate the project is practicable, meanwhile, high current density and solar radiation and low operating temperature can improve pollutant emissions reduction of the system. [ABSTRACT FROM AUTHOR]

During the proton exchange membrane fuel cell (PEMFC) operation, liquid water accumulates in the PEMFC, causing water flooding and performance degradation, especially at high current densities. Moisture dehumidification has been used to remove excess water in PEMFCs by forming a high water vapor concentration gradient between the inside and outlet of PEMFCs. In this study, the cathode outlet gas was condensed by adding thermoelectric refrigeration equipment to the cathode outlet of a single cell, and the influence of gas condensation on PEMFC performance under different working conditions was studied. The results showed that the effect of moisture dehumidification on PEMFC performance depended on the water content in the PEMFC, and the positive effect was more evident under high current density, high relative humidity, and high pressure. Moreover, moisture dehumidification is beneficial to alleviate the degradation of the catalyst layer. When there was no exhaust gas condensation, large-area fractures and loss occurred in the catalyst layer after 100 h of operation, and the electrochemically active area (ECSA) was reduced by 22.28%. There was only a slight reduction in the thickness of the catalyst layer with moisture dehumidification, and the ECSA was only reduced by 1.82%. Therefore, the degree of moisture dehumidification should be adjusted according to the water content inside the PEMFC in actual operation. • The effects of moisture dehumidification on the PEMFC performance is studied. • The effect of moisture dehumidification depended on the water content. • Moisture dehumidification can effectively alleviate water flooding. • The more water content in the PEMFC, the more obvious the positive effect. • The degree of moisture dehumidification should be adjusted according to the water content. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) vehicles (PEMFCV) have drawn tremendous attention owing to the advantages of low or zero emissions. Effective integrated thermal management systems (ITMS) considering thermal loops coupling and interaction and with a rational strategy are crucial for the efficient and secure operation of PEMFCV. Therefore, ITMS in PEMFCV are worthy to be reviewed comprehensively. This paper aims to provide the general and current ideas of ITMS design in PEMFCV from part-level to system-level, along with control strategies. The factors that affect the thermal performance of heat-generating components and systems are deeply analysed, and the key findings, challenges, and future work are presented. It is found that liquid cooling is more appropriate for ITMS because of the high specific heat and the convenience of integrating other thermal systems, and that heat pumps tend to be a more suitable choice for air conditioning systems. The future work mainly includes the improvement of cooling and cold start of PEMFC, perfection and verification of waste heat recovery system, exploration of new air conditioning systems, integration of systems, coupling of ITMS and energy management systems, and enhancement of model accuracy. The provided information is useful to guide the system layout and control strategies for ITMS at the early design stage. [Display omitted] • The state of art for thermal management of the main components and systems in PEMFCV was reviewed. • ITMS in HEV were summarized for comparison with those in PEMFCV. • The current progress, challenges and future work of ITMS in PEMFCV were presented. [ABSTRACT FROM AUTHOR]

• A PEMFC-based CCHP system integrated with methanol reforming and dehumidification. • Realize the cooling and dehumidification of the data center simultaneously. • The dynamic performance under the cooling-led strategy is studied. • The temperature and humidity of the data center are controlled at 25 °C and 55–63%. For data centers with strict requirements on temperature and humidity, this study proposes a combined cooling, heating and power (CCHP) system integrated with methanol-reforming and dehumidification based on proton exchange membrane fuel cells (PEMFCs). The system consists of a methanol-reformer, preferential oxidation (PROX) reactor, PEMFC stack, adsorption chiller, desiccant air conditioning (DAC), and phase change material (PCM) heat storage tank. Taking a data center in Harbin as the research object, the dynamic response characteristics of the system are studied, and the system has good dynamic response characteristics. The CO concentration in the reformed gas is controlled by controlling the O 2 /CO ratio in the PROX. The CO concentration in the transformation gas can be controlled below 4 ppm. The cooling and dehumidification requirements of the data center are met by controlling the cooling power of the system and the air intake conditions of the data center. The results show that the cooling power of the system rises for 400 s at the beginning of the operation, and stabilizes after about 2 h, and the temperature and relative humidity of the data center can be controlled at 25 °C and 55–63%. The novel system develops an efficient way to recover low-grade waste heat of PEMFC stacks for cooling and dehumidification in data centers. [ABSTRACT FROM AUTHOR]

• PEMFC is stable when compression ratio of nickel metal foam on cathode is beyond 0.69. • The performance of PEMFC increases with the rise of compression ratio on cathode. • There is optimal compression ratio of nickel metal foam on anode, namely 0.38. • There is optimal PPI of nickel metal foam on cathode, namely 75. • Compared with the CMF, maximum power density of the OMF increases by 9.8%. In order to tackle the water flooding issue in proton exchange membrane fuel cell (PEMFC), the effects of structure parameters of nickel metal foam on water management and the performance of PEMFC were experimentally investigated. Experimental results indicated that when compression ratio of nickel metal foam on cathode is beyond 0.69, the voltage of PEMFC is completely stable in a 3-hour constant current density test. Furthermore, the performance of PEMFC enhances with the rise of compression ratio on cathode. However, there is an optimal compression ratio of nickel metal foam on anode, namely 0.38. Regarding PPI (pores per inch) of nickel metal foam, it has been found that there is an optimal PPI on cathode, namely 75, due to the synergic effect between the distribution of reactant gas and water management in nickel metal foam flow fields with different PPIs. In contrast with cathode, a higher PPI of nickel metal foam results in better performance on anode. Compared with the case that uncompressed nickel metal foam with 110 PPI for anode and cathode, the maximum power density and energy conversion efficiency of the optimized metal foam fuel cell, namely 110 PPI and compression ratio of 0.38 for anode and 75 PPI and compression ratio of 0.75 for cathode, increase by 9.8% and 4.6%, respectively. In order to further intensify the performance of PEMFC, the effect of assembly force was considered. Since nickel metal foam could protect the MEA, a higher assembly force can be tolerated to obtain better performance. [ABSTRACT FROM AUTHOR]

• Novel structure of Windward-Louvered fin radiator is numerically and experimentally studied. • The thermal and flow performance of real size traditional and optimized radiators are compared. • The optimized radiator exhibits better performance since the flow directs towards the tube wall. Proton exchange membrane fuel cells are an ideal power source for modern energy vehicles owing to their high efficiency, fast response, and zero emission. Because of the low heat exchange temperature difference and high power load, the cooling system in internal combustion engine vehicles can no longer satisfy the heat dissipation demand of fuel cell vehicles (FCVs). Thus, the thermal management of FCVs must be improved, for which the compact radiator is a crucial component that discharges most of the waste heat outside the FCV. By inserting metal elbows into the airside of a compact radiator, we propose a novel structure aimed at promoting the thermal performance of a traditional compact radiator. The thermal and flow characteristics of the two types of radiators (traditional and optimised radiator) are compared, and the effect of the inserted windward bend structure is investigated numerically and experimentally. The Colburn j-factor and Fanning friction f-factor are calculated to evaluate the airside performance of the two radiators. The results indicate that the heat exchange is improved by 17.1%, 19.6%, 19.3%, and 22.5% accompanied with a modest increase in the pressure drop of 0.1%, 18%, 21%, and 18%, respectively, under four different operating conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a novel PEMFC-based combined cooling, heating and power (CCHP) system with independent control of refrigeration and dehumidification, which is used in data centers with strict requirements on temperature and humidity. The effects of operating parameters of PEMFC (current density, hydrogen and oxygen pressure) and refrigeration system (hot water distribution ratio, mass flow of cooling water and chilled water) on the 4E (energy, exergy, economy and environment) are investigated. Meanwhile, multiobjective optimization of the above parameters is carried out. The results show that a high inlet pressure is beneficial to improve system efficiency and reduce annual greenhouse gas (GHG) emissions. An increase in the chilled water mass flow increases system efficiency and reduces annual GHG emissions, while an increase in the cooling water mass flow yields the opposite results. Moreover, an increase in the proportion of hot water entering the adsorption chiller causes system efficiency and the annual GHG reduction to initially decrease and then increase. Compared with the unoptimized system, the energy efficiency, exergy efficiency, system cost, GHG emission reduction, electric power, cooling power, heating power and dehumidification rate of the system increase by 5.5%, 0.77%, 10%, 21.27%, 12.87%, 5.37%, 45.73% and 1.53%, respectively. [ABSTRACT FROM AUTHOR]

• A novel structure of Windward-Louvered fin is proposed to be used in the radiator. • The heat exchange ability on the tube wall can be greatly enhanced by the flow deflection. • Heat exchange performance increased with decreasing synergy angle at high air flow rate. Fuel cell vehicle (FCV) is regarded as a worldwide promising technology due to its high efficiency and zero emission. Heat management is very important during the operation of FCV, especially under high power output and environment temperature. As a consequence, development of a high heat dissipation ability radiator is necessary for the state-of-the-art FCV. In this paper, heat exchange characteristics of four different radiators are investigated in detail. A special air flow deflection phenomenon in the Windward bend structure is found to be beneficial for heat dissipation. A novel structure of Windward-Louvered fin (WLF) is proposed to be used in the radiator. The result shows that its Nusselt number is 1.2-1.3 times higher than that in Windward bend structure. In addition, field synergy theory is used for the evaluation of the heat transfer ability among the four structures. The synergy angles between velocity vector and temperature gradient are 82.1°, 82.5°, 87.0°, 81.8° at the air flow rate of 12 m•s−1, respectively. The WLF structure has the smallest synergy angle, thus the heat exchange amount is over 1.25 times higher than that of Windward bend structure. [ABSTRACT FROM AUTHOR]

• Partial flooding model has been developed by modifying the porosity near the outlet. • Partial flooding induces uneven distributions of water, reactant and current density. • Enhance water management is very important in the outlet of a PEMFC. Water management is one of the key issues for efficient and stable operation of proton exchange membrane fuel cells (PEMFCs). Water flooding easily occurs at the elevated operation current density, especially at the downstreaming of the flow channel where the generated water should flow out. Proper water management should meet the needs of adequate membrane hydration and the avoidance of flooding in the catalyst and gas diffusion layers. Flooding will not only lead to performance losses due to the hindered reactant supply, but also the safety issue because of the cell reversal. A partial flooding model is proposed to investigate the effect of the porosity on the performance of a PEMFC. The results show that high temperature is conducive to the suppression of flooding at low relative humidity, and flooding would lead to the deterioration of mass transfer due to the porosity decrease of gas diffusion layer, especially at high current densities. Partial flooding won't significantly affect the power generation capacity of the fuel cell, but will cause uneven distribution of current density, resulting in an adverse influence on long-term operation. Moreover, the performance would suffer serious degradation with completely flooding. Once the area inside the PEMFC is seriously flooded, the current density in non-flooded area is up to 4.7 times higher than that in the flooded area, and the performance is difficult to recover even if increasing the stoichiometry of reactants. The study illustrates the importance of the water management at the downstreaming of the fuel cell. [ABSTRACT FROM AUTHOR]