Membrane Water Content Research Articles

State Estimation of Membrane Water Content of PEMFC Based on GA-BP Neural Network

Too high or too low water content in the proton exchange membrane (PEM) will affect the output performance of the proton exchange membrane fuel cell (PEMFC) and shorten its service life. In this paper, the mathematical mechanisms of cathode mass flow, anode mass flow, water content in the PEM and stack voltage of the PEMFC are deeply studied. Furthermore, the dynamic output characteristics of the PEMFC under the conditions of flooding and drying membrane are reported, and the influence of water content in PEM on output performance of the PEMFC is analyzed. To effectively diagnose membrane drying and flooding faults, prolong their lifespan and thus to improve operation performance, this paper proposes the state assessment of water content in the PEM based on BP neural network optimized by genetic algorithm (GA). Simulation results show that compared with LS-SVM, GA-BP neural network has higher estimation accuracy, which lays a foundation for the fault diagnosis, life extension and control scheme design of the PEMFC.

Model-based observer for vehicle proton exchange membrane fuel cell humidity based on adaptive sliding mode estimation technique

Real-time humidity acquisition for vehicle proton exchange membrane fuel cell (PEMFC) facilitates humidity control to avoid membrane flooding or drying, improving its efficiency and stability. However, due to the frequent changes of actual vehicle conditions and expensive as well as unreliable humidity sensors, it is difficult to obtain real-time water content in PEMFC, which brings obstacles to closed-loop control of humidity. To this end, a model-based observer is proposed to obtain real-time humidity. Specifically, a dimensionless third-order model of relative humidity for PEMFC was established, which includes the dynamic of membrane water content. Based on the proposed model, an adaptive sliding mode convergence algorithm was designed to approach real-time humidity using measurable signals (voltage, current, pressure, flow rate, and temperature). The exploration of proposed adaptive sliding mode observer (ASMO) performance was compared with non-adaptive sliding mode observer (SMO) and classical ASMO by using a real 80 kW commercial fuel system experimental data. The experimental results show that compared with second-order humidity model, proposed third-order humidity model reduced recovery time under small step condition, where 250 s for cathode humidity estimation and 200 s for anode humidity estimation. In addition, under the small step condition, the average error of the three observers was less than 3%, which is accurate for engineering application. Moreover, proposed ASMO had the minimum static error, with 4% for cathode humidity estimation and 9% for anode humidity estimation under large step conditions as well as MAE, MSE, RMSE with 4%, 1.90%, 4.39% for cathode relative humidity estimation, 8.19%, 0.89%, 9.44% for anode relative humidity estimation respectively. The comprehensive results indicate that the proposed ASMO with adaptive parameters tuning has better dynamic performance than non-adaptive SMO as well as classical ASMO in terms of robustness and estimated accuracy.

Reaction Gas Pressure, Temperature, and Membrane Water Content Modulate Electrochemical Process of a PEMFC: A Simulation Study

Proton exchange membrane fuel cells (PEMFC) are widely used in transportation systems owing to their desirable characteristics such as high efficacy and low operating temperature. However, the fuel cell systems exhibit load changes as well as voltage and power losses so as to reduce dependence on the battery. The aim of the present study was to explore the composition and basic working principle of PEMFC. A PEMFC electrochemical reaction model was then established according to the electrochemical reaction principle of fuel cell to evaluate the effects of Nernst electromotive force, activation overvoltage, Ohmic overvoltage, concentration overvoltage, and electric double layer. The effects of activation loss, concentration loss, and Ohmic loss on the fuel cell were evaluated through simulation analysis. The effect of various factors on the dynamic output of a 60 kW PEMFC was explored through dynamic simulations. The findings showed that a change in current modulated a change in voltage through the Ohmic loss equivalent resistance. The activation loss equivalent resistance and the concentration loss equivalent resistance decreased the voltage loss owing to the presence of the capacitor. The output voltage of the fuel cell decreased with an increase in load current, whereas the output power increased with an increase in load current. Increase in partial pressure of oxygen caused an increase in output power and output voltage of the cell. The internal chemical reaction rate and the voltage output of the fuel cell increases with an increase in the working temperature. The findings of this study provide a basis for conducting further studies to produce efficient fuel cells for application in various systems.

Study on 3D Simulation Performance of Large‐Scale Proton Exchange Membrane Fuel Cell with Distribution Region

The majority of the current research examines fuel cell performance metrics using single channels or small‐area flow fields, but fails to take into consideration the actual shape of the flow field of modern proton exchange membrane fuel cell (PEMFC). The homogeneous distribution of reaction gas concentration and liquid water distribution is examined using 3D computational fluid dynamics simulation on a commercial large‐scale PEMFC with 113.92 cm2 reaction area and distribution region as the object. The results show that the gas distribution in the fluid flow is effectively optimized under the action of the distribution zone, and the maximum concentration error of anode is 4.87%, which is far less than that of cathode, and the higher the flow rate in the flow channel, the stronger the water removal ability; the effects of different working pressure and flow direction of reactant gas on gas concentration in catalytic layer and water content in proton exchange membrane are also studied. The results show that higher working pressure is beneficial to improve the performance of fuel cell, and countercurrent mode is better; finally, the influence of coolant is analyzed, and the results show that coolant can effectively reduce the internal temperature of the fuel cell, which is beneficial to improve the life of the fuel cell.

Whale optimization algorithm based MPPT control of a fuel cell system

Renewable energy sources have provided a great contribution to global energy demand; However, their intermittent characteristics can cause sustainability and efficiency problems. To handle these, alternative systems are utilized. Among these, proton exchange membrane fuel cells (PEMFCs) stand out with their longer lifecycle, efficient, and cost-effective features. However, their performance depends on operating conditions such as temperature, gas pressure, and membrane water content. These nonlinear features require instant and proper control for maximizing efficiency and longer working life. In this study, a whale optimization algorithm (WOA) based maximum power point tracking (MPPT) controller is utilized for a PEMFC system. To validate the proposed controller, the PEMFC system has been analyzed under changing conditions in the MATLAB/Simulink environment. The proposed method has been compared with the other MPPT methods. The results indicate that the proposed controller can provide accurate and fast MPPT performance, less power fluctuations, and higher production efficiency.

Sensitivity analysis of structural parameters for PEMFCs based on 1D transient model and elementary effect method

ABSTRACT To investigate the influences of structural parameters on output performances and further quantify the degree of influences, a one-dimensional transient multiphase proton exchange membrane fuel cell (PEMFC) model and a global sensitivity analysis model were established. After rigorous model validation, structural parameters such as the thickness of proton exchange membrane (MEM), catalytic layer (CL), micro-porous layer (MPL), and gas diffusion layer (GDL) as well as the porosity of CL, MPL, and GDL were studied. The ionomer volume fraction of cathode and anode were also studied. Increasing the thickness of MEM and CL decreases the membrane water content and increases the ohmic voltage loss. The increase of thickness leads to longer reaction gas transfer path and increase of transfer resistance. The increase of porosity increases the concentration of the reaction gas . However, too high porosity will reduce the effective ion conductivity . The increase of ionomer volume fraction is beneficial to electrochemical reaction. Based on quantitative sensitivity analysis, the MEM thickness and the anode ionomer volume fraction are defined as highly sensitive parameters. The MPL thickness and the GDL porosity are defined as insensitive parameters. The sensitivity of MEM thickness, CL thickness, and anode ionomer volume fraction become more prominent in large current density regions.

Influence of water transport characteristics on membrane internal conductive structure in forward osmosis microbial fuel cell

As the characteristic of forward osmosis microbial fuel cells (OsMFCs), water flux is crucial for improving electricity generation, and the ohmic resistance of the membrane itself directly influences the performance of OsMFCs. This paper was aimed at analyzing the relevance between water content and resistance of membrane on the basis of electro-osmotic and osmotic water flux which were measured respectively under the electric field and osmotic pressure in OsMFCs and explained the phase transition of intramembrane environment from non-conductive zone to the conductive zone was an important reason leading to the reduction of membrane impedance. In the meantime, the changes inner membrane structure and membrane resistance under the influence of membrane water content were also analyzed.

PEMEC performance evaluation through experimental analysis of operating conditions by response surface methodology (RSM)

The optimum current value of the proton exchange membrane electrolysis cell (PEM-EC) mainly depends on various operational factors, such as temperature, operating pressure, water flow rate, and membrane water content. Therefore, this study aims to maximize performance related to the current of PEM-EC by determining the optimal operating conditions of the PEM electrolysis cell having a 9 cm² active layer. In this regard, response surface methodology (RSM) and central composite design (CCD) were applied using Design-Expert (trial version) software to identify the optimal combination of operating variables such as temperature, pump speed, and cell voltage. Temperature, pump speed, and cell voltage were the independent variables to have ranged from 40-80 °C, 1-8, and 1.8-2.3 V, respectively. Also, the individual and combined effects of operational parameters on cell performance will be included in this study by ANOVA (analysis of variance). The optimal parameters are 80 °C, 1, and 2.3 V, respectively, temperature, pump speed, and cell voltage corresponding to the maximum current output of PEM-EC. This RSM tool found that the maximum current was 16.778 A. In addition, it was concluded that the most influential parameter on cell performance was the cell voltage, followed by the temperature.

Swelling dynamics and chain structure of ultrathin PEG membranes in seawater

Polyethylene glycol (PEG) is widely utilized in marine antifouling materials; thus, the fundamental understanding of PEG characteristics in seawater is indispensable. Herein, a “membrane-seawater” separation chamber model is designed, and the molecular dynamics (MD) method is used to simulate the swelling process of PEG membranes in seawater; two characteristic lengths are developed from the concept of Gibbs surface to illustrate the relationship between seawater ions and PEG membranes; the amount of bound water in the hydration shell of PEG is calculated by experimental method. It is concluded that the water content of the PEG membrane in seawater is not much different from that of swelling in water; only the swelling rate changes; the seawater ions accelerate the swelling of the PEG membrane, but most gathered in the outer layer of PEG membrane; Ions change the distribution structure of the hydration layer, and the bound water of PEG decreases under the action of seawater ions. Moreover, the structure of the PEG chain in seawater has a change of “helix-ring”. The study of PEG in seawater will provide an effective supplement and theoretical basis for the modification design of PEG coating.

A new maximum power point tracking method for PEM fuel cell power system based on ANFIS with modified manta ray foraging algorithm

The proton exchange membrane fuel cell (PEMFC), which is accounted as a reliable fuel cell (FC) technology, is mainly famous for its low operating temperature and expanded lifespan while also being highly efficient. Such merits have turned the PEMFC into an interesting option to be employed in a wide range of applications, comprising those for backup power, portable power, and vehicle power sources. Due to the output power’s dependence on temperature and membrane water content, the PEMFC, however, faces a number of difficulties. The FC system’s maximum output power can only be achieved at one specific operating point under varying operating circumstances. Therefore, maximizing the power obtained from the PEMFC is essential for improved operation and effective exploitation. It is noteworthy that a combinatorial technique using the developed modified manta ray foraging optimization (DMRFO) method and enhanced adaptive neuro-fuzzy inference system (ANFIS)-based incremental conductance (INC) has been deployed in this paper for the maximum power point tracking (MPPT) to optimally increase the power extraction capacity of an FC-resourced energy system. This method consists of two steps. In the first stage, the DMRFO algorithm is used to specify the best power levels while taking temperature and membrane water content fluctuations into account. This information would be utilized as the input–output training dataset in the ANFIS. The INC approach would initialize at this value in the second stage and seek the highest maximum power point (MPP). The dataset with the shrunk size given by the proposed DMRFO method for training the ANFIS in contrast to prevalent ANFIS is one of the benefits of adopting the ANFIS-based INC technique. This approach is also very quick, stable, and efficient. By taking into account a PMFC with a capacity of 7,000 W, the recommended technique is simulated and the results are compared with other methods to validate the performance.

Maximum Power Point Tracking of a Grid Connected PV Based Fuel Cell System Using Optimal Control Technique

The efficiency of renewable energy sources like PV and fuel cells is improving with advancements in technology. However, maximum power point (MPP) tracking remains the most important factor for a PV-based fuel cell power system to perform at its best. The MPP of a PV system mainly depends on irradiance and temperature, while the MPP of a fuel cell depends upon factors such as the temperature of a cell, membrane water content, and oxygen and hydrogen partial pressure. With a change in any of these factors, the output is changed, which is highly undesirable in real-life applications. Thus, an efficient tracking method is required to achieve MPP. In this research, an optimal salp swarm algorithm tuned fractional order PID technique is proposed, which tracks the MPP in both steady and dynamic environments. To put that technique to the test, a system was designed comprised of a grid-connected proton exchange membrane fuel cell together with PV system and a DC-DC boost converter along with the resistive load. The output from the controller was further tuned and PWM was generated which was fed to the switch of the converter. MATLAB/SIMULINK was used to simulate this model to study the results. The response of the system under different steady and dynamic conditions was compared with those of the conventionally used techniques to validate the competency of the proposed approach in terms of fast response with minimum oscillation.

Effect of assembly pressure on the performance of proton exchange membrane fuel cell

The assembly force is a crucial factor in the process of proton exchange membrane fuel cell (PEMFC) stacking, and has significant effects on the fluid flow, mass transfer, and water and thermal management, which affect the fuel cell performance. In this study, from the most deformable component, the gas diffusion layer (GDL), combining with a finite-element analysis, and computational fluid dynamic method, the impact of the assembly force on a single-channel PEMFC is analyzed. A nonlinear stress–strain curve obtained from a microanalysis is creatively introduced into the two-dimensional compression model. The gas diffusion coefficient in the three-dimensional model is also obtained from the microscopic simulation. The simulated effective oxygen diffusion coefficient of the compressed GDL is approximately 0.86 times the Bruggemann estimated value. When the contact resistance is ignored, the output voltage at 2.5 MPa is decreased by approximately 15.4% at 1.7 A·cm−2 compared with that at 0.5 MPa. After the contact resistance is considered, the effects of the assembly pressure on the cell performance (V–I curve) are qualitatively different. The pressure drop of the 2.5 MPa case is 20% higher than that of the 1.4 MPa case at 1.7 A cm−2. O2 is hard to flow into the region under the rib where the porosity and permeability are lower. The results indicate that both liquid water and membrane water contents increase when the assembly force increases. The effect of the assembly force on the temperature is also analyzed.

Effect of cathode channel structure on the performance of open-cathode proton exchange membrane fuel cell in dry environments

The open-cathode proton exchange membrane fuel cell (OC-PEMFC) is a promising power supply for mobile equipment and the design of the cathode channel structure has a significant effect on its water and thermal management. In this study, a three-dimensional multifield coupled OC-PEMFC single-cell model based on a graphite bipolar plate was used to investigate the performance of three types of cathode channel designs, namely, straight, divergent, and convergent channels, under dry ambient conditions. Under ambient conditions of 10 °C and 35% relative humidity, the divergent channel design exhibits the best performance, with the highest membrane water content and uniformity, even when the ambient temperature is increased. The performance of OC-PEMFCs can be improved by increasing the cathode stoichiometric ratio (CSR) under high-temperature and dry conditions. The divergent channel design has the best output performance under various CSRs. The growth percentage of the water content in the membrane ranges from 5.3 to 8.0%, and the average temperature in the membrane is reduced by 2.78–3.47 °C. Although the performance of the convergent channel design is improved, the uniformity of the water and electricity is significantly reduced. This study also provides guidance for the design of OC-PEMFC graphite bipolar plates.

Modeling transport of membrane water in PEMFC and energy loss analysis at −20 °C based on mathematical boundedness

This work analyzes why the classic cold start-up model cannot match experimental data well in high initial membrane water content due to the unboundedness of membrane water content conservation equation, and a mathematical framework to ensure the boundedness of membrane water content is developed to solve these issues. Based on vehicle mechanism and Grotthuss mechanism, a “traffic jam” model is applied to describe the transport of membrane water reaching its maximum content. To keep the membrane water content within the upper bound, a new governing equation is proposed and the corresponding boundary conditions and discretization schemes are set. This model has been proved in eleven cases by comparing with experimental data including different initial membrane water content and different current density. Some of these cases are considered impossible to exist in classical cold start-up theory. The results illustrate that the boundedness model can show a clearer physical process and obtain more accurate and reasonable calculation results.

Designing a novel poly (methyl vinyl ether maleic anhydride) based polymeric membrane with enhanced antifouling performance for removal of pentachlorophenol from aqueous solution

In this current study, poly (methyl vinyl ether maleic anhydride) (PMVEAMA), a sustainable additive, was incorporated into poly (ether-ether sulfone) (PEES) polymer to design a novel polymeric hybrid membrane for the efficient filtration of toxic pentachlorophenol (PCP) from an aqueous medium. Hydrophilic additives significantly altered the membrane's morphology, structure, porosity, water content, and flux performance compared to the bare PEES membrane. The influence of PMVEAMA on the structural modification of the synthesized polymer membrane was confirmed by SEM, ATR-FTIR, XRD, AFM, zeta potential and contact angle. Findings revealed that the addition of PMVEAMA to the PEES polymer enhances the porosity (17.7%–28.9%), water content (29.8%–39.8%), and pure water flux (186 Lm−2h−1 to 349 Lm−2h−1). The effect of PMVEAMA concentration on the PEES membrane exhibited more finger like pores, better porosity and hydrophilicity, reduced surface roughness, fouling and increased permeability. The fouling studies exhibit an improved 57% PCP rejection and permeation flux of 22.3 Lm−2h−1 due to the addition of the hydrophilic additive. Surprisingly, the incorporation of PMVEAMA into the bare PEES membrane resulted in a high flux recovery ratio of 73.7%. The antifouling properties and enhanced permeability of the PEES/PMVEAMA membrane indicates its potential application in water purification sectors for the efficient separation of contaminants.

An extreme gradient boosting-based thermal management strategy for proton exchange membrane fuel cell stacks

The working temperature is one of the critical factors for proton exchange membrane fuel cell (PEMFC) stacks, as it directly influences the performance and working life of PEMFCs. Due to the inherent nonlinearity of the PEMFC stack thermal management system model, current thermal management strategies (TMSs) generally face with the drawbacks of lower accuracy and robustness. In this research, a novel machine learning (ML) algorithm, i.e. the extreme gradient boosting (Xgboost) algorithm is applied to the TMS of a PEMFC stack to control the inlet and outlet temperatures of the PEMFC stack, where the proton exchange membrane (PEM) water content is also considered and kept at a reasonable level. In order to evaluate the effectiveness of the proposed strategy, a fuel cell hybrid vehicle (FCHV) model from Autonomie software is selected and the proposed TMS is tested and compared to other strategies under a mixed driving cycle for the PEMFC stack. Results show that the proposed Xgboost-based TMS presents the best control performance, which reduces the maximum deviation of the PEMFC stack temperature and the variation range of the PEM water content compared to other ML-based TMSs and the fuzzy logic-based TMS.

Comprehensive investigation of membrane sorption and CFD modeling of a tube membrane humidifier with experimental validation

The humidification of PEM fuel cells is critical for their performance and efficiency and for ensuring a long durability. In most PEM fuel cell systems for mobile applications membrane humidifiers are used to humidify the fresh air. In this process, the water contained in the cathode exhaust gas is used to increase the humidity of the supply air. Despite the simple design of membrane humidifiers, the simulation of the water transfer is difficult and so far there exist hardly any precise models to calculate the absorption and desorption processes. Common approaches that use the Sherwood number to determine the sorption rates cannot account for the influence of the local water content of the membrane. This ultimately leads to an inaccurate simulation of humidifier behavior, as these models cannot consider the fact that desorption is nearly ten times faster than absorption.In this study, an empirical formula for an accurate determination of the sorption rate is derived based on experimental data. This function accounts for the different absorption and desorption rates by finding a sorption rate coefficient as a function of the local membrane water content, temperature, pressure and flow velocity.Furthermore, a CFD model is derived from the geometry of a commercially available membrane humidifier, which is also investigated on a test bench. Using the experimental data, the CFD model is validated and it is shown that the developed sorption rate formula leads to good agreements between simulations and experiments at steady-state operating points of the humidifier.

Numerical study of PEMFC heat and mass transfer characteristics based on roughness interface thermal resistance model

The thermal contact resistance (TCR) is the main component of proton exchange membrane fuel cell (PEMFC) thermal resistance due to the existence of surface roughness between the components of PEMFC, and the influence of TCR is often ignored in traditional three dimensional PEMFC simulations. In this paper, the heat and mass transfer characteristics including polarization curve, power density curve, temperature distribution, membrane water content distribution, membrane current density are studied under different component surface roughness conditions, and finally the effect of each TCR on the PEMFC performance is studied. It is found that under the same operating conditions, the TCR makes the radial heat transfer of the PEMFC decrease, and the temperature of the membrane electrode and the temperature difference of each component of the PEMFC is higher than that of the model without TCR. When the surface roughness of components in the PEMFC equals 1 μm, 2 μm, 3 μm, the cell current density decreases by 6.56%, 12.46% and 17.17% respectively when the output cell voltage equals 0.3 V, and the cell power density decreases by 3.64%, 7.54%, 13.14% respectively when the cell current density equals 1.2 A·cm−2. When the TCR between the CL and PEM equals 0.003 K·m2·W−1, 0.005 K·m2·W−1, 0.01 K·m2·W−1, the cell current density is increased by 2.30%, 3.65%, 6.74% respectively under the condition that the output cell voltage equals 0.3 V, and the cell power density is increased by 1.24%, 1.85%, 3.10% respectively when the cell current density equals 1.2 A·cm−2. The results show that the numerical simulation of PEMFC cannot ignore the effect of TCR.

The potential of Bacillus subtilis and phosphorus in improving the growth of wheat under chromium stress.

Hexavalent chromium (Cr+6 ) is one of the most toxic heavy metals that have deteriorating effects on the growth and quality of the end product of wheat. Consequently, this research was designed to evaluate the role of Bacillus subtilis and phosphorus fertilizer on wheat facing Cr+6 stress. The soil was incubated with Bacillus subtilis and phosphorus fertilizer before sowing. The statistical analysis of the data showed that the co-application of B. subtilis and phosphorus yielded considerably more significant (p < 0.05) results compared with an individual application of the respective treatments. The co-treatment improved the morphological, physiological and biochemical parameters of plants compared with untreated controls. The increase in shoot length, root length, shoot fresh weight and root fresh weight was 38.17%, 29.31%, 47.89% and 45.85%, respectively, compared with untreated stress-facing plants. The application of B. subtilis and phosphorus enhanced osmolytes content (proline 39.98% and sugar 41.30%), relative water content and stability maintenance of proteins (86.65%) and cell membranes (66.66%). Furthermore, augmented production of antioxidants by 67.71% (superoxide dismutase), 95.39% (ascorbate peroxidase) and 60.88% (catalase), respectively, were observed in the Cr+6 - stressed plants after co-application of B. subtilis and phosphorus. It was observed that the accumulation of Cr+6 was reduced by 54.24%, 59.19% and 90.26% in the shoot, root and wheat grains, respectively. Thus, the combined application of B. subtilis and phosphorus has the potential to reduce the heavy metal toxicity in crops. This study explored the usefulness of Bacillus subtilis and phosphorus application on wheat in heavy metal stress. It is a step toward the combinatorial use of plant growth-promoting rhizobacteria with nutrients to improve the ecosystems' health.

Schroeder's paradox in proton exchange membrane fuel cells: A review

Schroeder's paradox discovered by Schroeder in 1905 refers to the phenomenon that polymers have different maximum water uptake in the liquid and saturated vapor phases. For more than a hundred years, people have often debated whether this phenomenon conforms to thermodynamics. As proton exchange membrane fuel cell (PEMFC) gradually becomes a promising renewable energy utilization device, its impact on the physical properties of the proton exchange membrane has been studied widely. This paper reviews the theory and experiments on Schroeder's paradox over more than 100 years, especially the exploration of perfluorosulfonic acid membranes and PEMFCs in recent decades. Since membrane water content determines the operational performance of the PEMFC, this paper discusses and analyzes the effect of Schroeder's paradox on the PEMFC performance, including mechanical properties, electrical conductivity, and water transport mechanism. The effect of this phenomenon on the non-equilibrium operation of PEMFC has been highlighted, such as cold start-up, because of the different properties of membranes in contact with liquid water and air. This review gives an introduction to critical aspects of Schroeder's paradox to serve governments and organizations to promote the application of PEMFC in different regions.