Polymer Electrolyte Membrane Fuel Cell System Research Articles

Coordinated management of oxygen excess ratio and cathode pressure for PEMFC based on synthesis variable-gain robust predictive control

In this research endeavor, a novel synthesis variable-gain robust model predictive control (SVGRPC) method using the min-max technique with parameter dependent Lyapunov functions is introduced to achieve the desired trajectory tracking of oxygen excess ratio (OER) and cathode pressure in the polymer electrolyte membrane fuel cells (PEMFCs) system. Initially, a simplified control-oriented model of the air supply system is developed and then transformed into a polytopic form to accommodate the inherent uncertainties in the PEMFC. Subsequently, the polytopic model is integrated with the reference trajectory to construct an augmented state-space model for deriving an error state representation. In the framework of robust model predictive control (RPC) utilizing a parameter-dependent Lyapunov function, a series of variable feedback gains are employed to mitigate conservatism. Additionally, the online solution process imposes a significant computational burden, presenting challenges for the real-time implementation of RPC-based control strategy. Therefore, the offline computing is introduced to significantly reduce the computational burden, resulting in the development of the SVGRPC strategy proposed in this paper. Subsequently, the SVGRPC strategy computes explicit linear state-feedback control laws by solving linear matrix inequalities (LMIs) using an offline control algorithm. The effectiveness of the proposed controller is then validated through assessments conducted under three distinct operating conditions of the PEMFC system. The outcomes of this study affirm that the proposed controller improves the requirements of control performance when compared to the online RPC with a quadratic Lyapunov function while significantly alleviating the computational workload.

Common cause analysis of the air supply system of fuel cell-powered propulsion systems in electrified aviation

By means of a Common Cause Analysis (CCA), potential safety challenges of the air supply system for polymer electrolyte membrane fuel cell systems (PEMFCSs) as the primary energy provider in electric aero engines are identified and mitigated. The design of an exemplary hydrogen-fuelled PEMFCS-powered aero engine is described, focusing on the air supply system. The safety assessment method CCA, consisting of a Zonal Safety Analysis (ZSA), a Particular Risk Analysis (PRA) and a Common Mode Analysis (CMA), is described and conducted on the PEMFCS aero engine’s air supply system. Failure modes and external events, which can have safety effects are identified, and potential design adaptations for mitigation are presented.

Hierarchical multi-objective optimization of proton exchange membrane fuel cell with parameter uncertainty

It is important to improve the performance indexes including the net power and system efficiency for polymer electrolyte membrane fuel cell (PEMFC), especially considering the parameter uncertainty. To this end, this paper proposes a hierarchical multi-objective optimization framework including the off-line and on-line optimization. Firstly, a steadystate non-linear PEMFC system model is established as the base model. Secondly, an adaptive multi-objective particle swarm optimization (AMPSO) algorithm scheme is proposed in the off-line optimization procedure for the exact optimization of operation parameters. Meanwhile, an adaptive flight parameter strategy based on the particle dispersity (PD) information is proposed to balance the convergence and diversity of Pareto solutions. Finally, to decrease the influence caused by parameter uncertainty, the interval optimization method is proposed in the on-line optimization layer based on the results of AMPSO. The convergence condition of the proposed optimization scheme is verified by theory analysis. The proposed AMPSO is compared with different algorithms in the numerical simulation and hardware-in-loop (HIL) experiments. Meanwhile, the performance of the proposed method is tested on four representative benchmark problems. These results demonstrate that the PEMFC system with the proposed optimization scheme performs better than the base model and classical optimization algorithms in terms of the net power and system efficiency indexes, revealing the success of this hierarchical optimization approach in solving the accurate optimization and parameter uncertainty problems. By using statistical test methods, the proposed algorithm performs better hypervolume (HV) metric from the Pareto solution distribution.

Redesign of Anode Catalyst for Sustainable Survival of Fuel Cells.

Polymer electrolyte membrane fuel cells (PEMFCs) suffer from severe performance degradation when operating under harsh conditions such as fuel starvation, shut-down/start-up, and open circuit voltage. A fundamental solution to these technical issues requires an integrated approach rather than condition-specific solutions. In this study, an anode catalyst based on Pt nanoparticles encapsulated in a multifunctional carbon layer (MCL), acting as a molecular sieve layer and protective layer is designed. The MCL enabled selective hydrogen oxidation reaction on the surface of the Pt nanoparticles while preventing their dissolution and agglomeration. Thus, the structural deterioration of a membrane electrode assembly can be effectively suppressed under various harsh operating conditions. The results demonstrated that redesigning the anode catalyst structure can serve as a promising strategy to maximize the service life of the current PEMFC system.

Air Mass Flow and Pressure Optimization of a PEM Fuel Cell Hybrid System for a Forklift Application

The air compressor holds paramount importance due to its significant energy consumption when compared to other Balance of Plant components of polymer electrolyte membrane (PEM) fuel cells. The air supply system, in turn, plays a critical role in ensuring the stable and efficient operation of the entire fuel cell system. To enhance system efficiency, the impact of varying the stoichiometric ratio of air and air pressure was observed. This investigation was carried out under real loading conditions, replicating the conditions experienced by the power module when fuel cells are in use within a forklift. The air compressor can be operated at different pressure and excess air ratios, which in turn influence both the fuel cell’s performance and the overall efficiency of the power module system. Our research focused on assessing the performance of PEM fuel cells under different load cycles, adhering to the VDI60 requirements for forklift applications. This comprehensive examination encompassed the system’s minimum and maximum load scenarios, with the primary goal of optimizing excess air and pressure ratio parameters, especially under dynamic load conditions. The results revealed that higher air pressures and lower excess air ratios were conducive to increasing system efficiency, shedding light on potential avenues for enhancing the performance of PEM fuel cell systems in forklift applications.

Electrode Coating Process Impact on the Performance of Pt and PtCo Fuel Cell Cathode Catalysts

The polymer electrolyte membrane fuel cell (PEMFC) is one of the most promising energy sources for replacing fossil fuels in vehicles, as it does not produce greenhouse gas emissions during operation. As a key player in hydrogen mobility, SYMBIO is developing and producing PEMFC systems for a large field of applications. SYMBIO masters the electrochemical core (the Membrane Electrode Assembly - MEA), the complete stack (bipolar plate, stacking and housing) and the fuel cell system (Balance of Plant, operating conditions, control-command, packaging) [1].The widespread use of fuel cell vehicles is strongly linked to the price of the PEMFC system, in which the MEA as a high share. Decreasing the total PGM content, as well as moving to high-speed roll-to-roll production methods are important levers in the cost roadmap of MEAs. And from a performance point of view, systems for the heavy-duty market will need to show high efficiencies at low current densities (<1 A/cm2). Exploring the potential of highly active cathode catalyst is therefore mandatory for these applications.State of the art cathode catalyst layers consists in either Pt or PtCo-alloy supported on carbon material, the latter being more active for the ORR but also less resistant towards potential cycling. Regarding the ink formulation, the use of PtCo poses the challenge that Co atoms could dissolve, even if the catalyst has been previously acid leached, leading to the release of free Co2 +. These free ions will latter lower the catalytic activity and the transport of reactants (H+ and O2) to the active sites in the catalytic layer [2-3].The manufacturing of a catalyst coated membrane (CCM) can be done with different printing processes involving a catalytic ink and a substrate. Each coating process has different constraints (ink rheological behaviour, particle size) leading to optimisation of ink recipe (solvent matrix, solid content ...). The ink must also be compatible with the substrate that can be directly an MEA component such as the membrane (direct coating) or the GDL, or a decal-carrier substrate. All these parameters lead to catalyst layer structure differences that impact the MEA performance.In this study, the impact of three coating processes, hence three solvent systems for a same catalyst, ionomer, and I/C ratio, on the MEA performance is explored for commercial Pt and PtCo catalysts. The coating processes compared are direct coating on membrane via bar coater and spray coater and non-direct coating using decal method.The inks properties including the granulometry and the viscosity of different prepared inks were characterized before coating. Ex-situ techniques (SEM-EDX, TEM, N2 adsorption/desorption) were used to figure-out the impact of the coating process on the morphology and porosity of the cathodic catalyst layer. The influence of these parameters on the electrochemical performance was studied using H2-Air polarization curves, electrochemical impedance spectroscopy and the electrochemical surface area (ECSA).It will be highlighted how important the final PEMFC performance must be understood by taking into account the used ink system and coating process, as well as the intrinsic stability of catalyst, ionomer and membrane during these stages.

Highly Robust Fuel Cell Electrodes Using Pt Thin Film Catalysts As Reversal Tolerant Anodes

Recent years have seen a rise in interest in polymer electrolyte membrane fuel cells (PEMFCs) because of its high power density, high energy efficiency, and zero-emission characteristics. PEMFC-powered fuel cell electric vehicles (FCEVs) have the potential to significantly lower the transportation sector's carbon dioxide emissions, paving the way for the global adoption of the hydrogen economy. However, the durability and robustness of fuel cell systems must be increased before a wider commercialization of FCEVs is possible. The hydrogen starvation in anode, occurring during start-up/shutdown or cold start, can cause rapid and significant deterioration of the performance and durability of a PEMFC system through cell reversal. In hydrogen-starved conditions, the cell's performance can deteriorate in just a few minutes, leading to sudden cell failure. Prior studies have been conducted to understand the degradation caused by hydrogen starvation and cell reversal in PEMFCs, with the aim of identifying mitigation solutions that could minimize deterioration of membrane electrode assembly (MEA) components. In this work, we present a novel materials strategy to mitigate cell damage using a thin film Pt anode catalyst supported on Nafion nanowires in a co-axial configuration. Due to the high roughness of Nafion nanowire, the coaxial nanowire electrode (CANE) negates the needs for conventional carbon support and displays exceptional robustness to reversal tolerance. This work will present a systematic evaluation of CANE as reversal tolerant anodes compared to conventional supported catalyst (Pt/C). Further enhancement in durability by integration of iridium with CANE anode will also be presented. Acknowledgement This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (2020200DR).

Design and analysis of liquid hydrogen-fueled hybrid ship propulsion system with dynamic simulation

In this study, we examine a liquid hydrogen (LH2)-fueled hybrid ship propulsion system (HSPS) consisting of an LH2 fuel gas supply system (FGSS), a polymer electrolyte membrane fuel cell (PEMFC), and battery systems. The LH2-HSPS is analyzed through three dynamic simulations, representing different PEMFC outputs, for a 2-MW-class tugboat. During transient states of LH2 FGSS, hydrogen temperature changes from 11 to 41 °C at the LH2 vaporizer outlet. Dynamic simulations considering hydrogen temperature tolerance in the PEMFC system show interruptions of power generation during 1–5 s. In Case 3, where the PEMFC system provides all propulsive power, an energy capacity of 310–1860 kWh is calculated with maximum C-rates of 1C–6C. The average power consumption of the balance of plant in the PEMFC system is 43.64, 27.51, and 44.06 kW for Cases 1–3, respectively. Finally, the battery system's thermal management is well performed for all cases.

Mechanistic investigation on the voltage collapse of polymer electrolyte membrane fuel cell under high-temperature and low-humidity conditions

Polymer electrolyte membrane fuel cell (PEMFC) operating under high-temperature and low-humidity (HTLH) conditions enables more efficient and compact fuel cell system through smaller radiators (less parasitic power) and smaller humidifier, but exerts negative influence on conductivity of perfluorosulfonic acid (PFSA) membrane, which is the most commercial proton conductor for PEMFC at current state. Although great progress has been made on the R&D of advanced PFSA-based material, a huge gap from material to PEMFC still exists due to its complicated physico-chemical processes. In this work, after a slight rise of operation temperature, we observe the unexpected voltage collapse of PEMFC under HTLH conditions and non-active zone (nearly zero local current density) is found to fast propagate from air inlet to the rest area during this period. For the first time, temporal–spatial numerical reconstruction of this dynamic process reveals that the current in-plane redistribution raises the local mass transfer losses but make limited contribution. Instead, the water being transferred from anode to cathode due to proton's dragging effect leads to severe anode ionomer dehydration, dominating such process. Finally, suggestions are provided as following: (a) raising membrane conductivity under dry condition or reducing proton's dragging coefficient could significantly improve PEMFC's performance under HTLH condition; (b) particular attention should be paid to the water content of anode ionomer for PEMFC design and system control.

Development of an ejector for passive hydrogen recirculation in PEM fuel cell systems by applying 2D CFD simulation

The anode subsystem is a major energy consumer of polymer-electrolyte-membrane (PEM) fuel cell systems. A passive hydrogen recirculation system, like an ejector, is an excellent solution to maximize hydrogen utilization while maintaining low parasitic losses. However, high development efforts are necessary to maximize the performance of the ejector for the entire operating range. This research paper provides part of a toolchain for ejector development, consisting in particular of a multi-parameter simulation based on rotational symmetric 2D CFD. The 2D CFD greatly helps optimize the design of the ejector, reducing development effort, and increasing accuracy. In addition, the main correlations between thermodynamic states and geometry on the entrainment ratio are evaluated. Subsequently, an ejector is designed for a PEM fuel cell application using 2D CFD and the results show in which operating range a single ejector can be applied. This toolchain enables rapid design and optimization of ejector geometry, saving development time and cost while increasing accuracy and extending the operating range.

Functional and Safety Challenges of Hydrogen Fuel Cell Systems for Application in Electrified Regional Aircraft

This paper identifies potential weaknesses and challenges of hydrogen fuel cell systems as main energy provider for electrified aircraft propulsion and presents potential solutions. The general design, operating principles and main characteristics of hydrogen-fuelled low-temperature polymer electrolyte membrane fuel cell systems (PEMFCSs) are described. The safety assessment process in aviation according to Aerospace Recommended Practices ARP4754A and selected methods according to ARP4761 are introduced. The functions of fuel cell systems in electrified aircraft powertrains are analysed in functional structure trees on aircraft, powertrain and fuel cell system level. By means of a Functional Hazard Analysis (FHA), potential malfunctions and their effects are investigated and their severity is evaluated. Critical failure modes are identified and requirements for acceptable failure probabilities are stipulated. Solution options to mitigate failure effects are stated. The results of the mentioned analyses reveal design challenges associated with the application of fuel cell systems in electrified aircraft propulsion, for instance, concerning functional independence as well as solutions for cold start conditions, heat transfer and lightweight design. Furthermore, safety challenges arise due to the utilisation of cryogenic hydrogen as fuel and the high amount of electric energy.

Power Output Optimisation via Arranging Gas Flow Channels for Low-Temperature Polymer Electrolyte Membrane Fuel Cell (PEMFC) for Hydrogen-Powered Vehicles

As we move away from internal combustion engines to tackle climate change, the importance of hydrogen-powered vehicles and polymer electrolyte membrane fuel cell (PEMFC) technology has dramatically increased. In the present study, we aimed to determine the optimal configuration for the power output of a PEMFC system using computational fluid dynamics (CFD) modelling to analyse variations of the primary serpentine design of gas flow channels. This helps improve efficiency and save on valuable materials used, reducing potential carbon emissions from the production of hydrogen vehicles. Different numbers of serpentine gas channels were represented with various spacing between them, within the defined CFD model, to optimise the gas channel geometry. The results show that the optimum configuration was found to have 11 serpentine channels with a spacing of 3.25 mm. In this optimum configuration, the ratio between the channel width, channel spacing, and serpentine channel length was found to be 1:2.6:38 for PEMFCs. Furthermore, the inclusion of fillets to the bends of the serpentine gas channels was found to have a negative effect on the overall power output of the fuel cell. Moreover, the optimisation procedures with respect to the number of gas channels and the spacing revealed an optimal power density exceeding 0.65 W/cm2.

Multiple inputs multi-phase interleaved boost converter for fuel cell systems applications

In this paper, a three inputs six-phase Interleaved Boost Converter (IBC) is proposed and designed for Fuel Cell (FC) systems, where the different Polymer Electrolyte Membrane Fuel Cells (PEMFC) systems are employed to validate. Considering that the selected converter is composed of three two-phase IBCs connecting in parallel, it shows many superiorities in topology, such as simple structure, high scalability/flexibility, easy maintenance and good fault-tolerant ability. The whole design process containing the selection of phase numbers, parameters design of the converter's components and steady-state operations analysis is focused in this paper. To further validate the correctness of the designed converter, a test bench is established based on dSPACE1104, where the issue of the implementation of six-PWM signals from dSPACE1104 is analyzed and a feasible solution is proposed. Last, experimental results are shown by performing the load disturbance rejection, the variable reference voltage and the PEMFC system's failure based on the designed Double-Loop Super-Twisting Sliding Mode (DL-STSM) controller.

Startup optimization of an automotive polymer electrolyte membrane fuel cell system with dynamic hydrogen reference electrodes

Efficient polymer electrolyte membrane fuel cell (PEM-FC) systems with minimal degradation are indispensable for automotive applications. A decisive measure to achieve this goal is the optimization of the startup procedure as part of the system operating strategy. This applies in particular to startups where the anode is partly or completely filled with ambient air after long downtimes. When displacing the air in the anode with hydrogen, damage to the cathode is inevitable and should be minimized. Basic approaches for this optimization are known from literature but are mainly derived from single cell and short stack experiments. In this paper, we optimize a full PEM-FC system by utilizing Dynamic Hydrogen Electrodes and show how gas replacement speed and half cell voltage evolution can be improved to mitigate degradation. The experimental results show that a homogeneous flow of the hydrogen/air front across the stack is to prioritize over its speed as only this enables additional upper voltage control in large stacks. The system optimum is achieved by maximizing startup pressure and purge valve flow, adapting the anode recirculation rate and precise voltage clipping. This study thus forms a procedural template for the optimization of the SUSD procedure in automotive fuel cell systems.

Fuel cell system production cost modeling and analysis

Fuel cell technology is seen as a promising option for decarbonizing global mobility. The costs of fuel cell systems are currently too high for increasing market penetration. The Chair of Production Engineering of E-Mobility Components at RWTH Aachen University has developed a cost calculation model for Polymer Electrolyte Membrane (PEM) fuel cell systems based on the method of Process Based Cost Modeling (PBCM) and is investigating possibilities for reducing manufacturing costs through economies of scale in production. The aim of this publication is therefore to present the results of cost modeling of PEM fuel cell systems and to derive design areas for technical innovations in terms of cost reduction through economies of scale in production. To this end, technical production parameters with the greatest influence on the cost structure of PEM fuel cell systems are identified and ranked by applying a sensitivity analysis. Finally, this work provides a recommendation for strategic investments and formulates the need for further research to reduce PEM fuel cell system costs by economies of scale.

A kW-level integrated propulsion system for UAV powered by PEMFC with inclined cathode flow structure design

Open-cathode air-cooling polymer electrolyte membrane fuel cells (PEMFCs) with the lightweight and simple structure are widely used in state-of-the-art UAVs. In this work, a 1 kW-level PEMFC powered propulsion system with an inclined cathode flow structure is developed. The inclined cathode flow structure uses the airflow behind the blade root of the propeller to meet the reaction and cooling requirements of the PEMFC cathode. Such design discards the cathode axial fan in the current commercial PEMFC system and reduces the parasitic power, weight and volume caused by the axial fan. Compared with the current commercial PEMFC powered propulsion system, the specific power of the 1 kW PEMFC system, power-to-weight ratio and thrust-to-weight ratio of the 1 kW integrated propulsion system are increased by 33.0 %, 23.8 %, and 18.3 %, respectively. Besides, the space in the fuselage for the fuel cells and the weight of distribution wiring, as well as the wire loss, is also significantly saved by replacing the axial fan with proposed inclined cathode flow structure.

Adaptive optimization strategy of air supply for automotive polymer electrolyte membrane fuel cell in life cycle

• Adaptive optimization matching method of the PEMFC system is presented. • The adaptive model of degradation stack can be universally applied in life cycle. • Validation is completed on experimental data of commercialized fuel cell engine. • Effects of air compressor parameters on the system efficiency are investigated. • System efficiency could be improved above 5% by adaptive optimization method. In this study, an adaptive optimization matching method of the air supply is developed to maintain the high-efficiency operation of the automotive polymer electrolyte membrane fuel cell (PEMFC) system in the life cycle. A 1-D non-isothermal model of the PEMFC stack with 150 kW designed power and a centrifugal air compressor model are developed, considering the fuel cell performance degradation. The genetic algorithm (GA) is used to optimize the overall system efficiency under various output powers to achieve adaptive matching. The 1-D stack model is validated with the experimental test results at two states (before and after 800 h degradation), considering the effect of degradation on the matching strategies. Through the optimization method, the centrifugal air compressor is adaptively matched with the stack of the proposed two states to develop the compressor matching strategies under various stack conditions individually. It is found that the efficiency of the system with this optimized method is 3.8% higher than that of the system without an optimized method under the full system power range. In addition, the new matching strategy between the air compressor and the stack after degradation is exploited by the adaptive optimization method. With the help of this method, the efficiencies of the system and the stack are 5.7% and 2.9% higher than that of the matching strategy without adaptive updating. It is shown that this adaptive optimization method not only improves the output efficiency of the stack but also reduces the additional parasitic power consumed by the compressor.

A study into Proton Exchange Membrane Fuel Cell power and voltage prediction using Artificial Neural Network

Polymer Electrolyte Membrane fuel cell (PEMFC) uses hydrogen as fuel to generate electricity and by-product water at relatively low operating temperatures, which is environmentally friendly. Since PEMFC performance characteristics are inherently nonlinear and related, predicting the best performance for the different operating conditions is essential to improve the system’s efficiency. Thus, modeling using artificial neural networks (ANN) to predict its performance can significantly improve the capabilities of handling multi-variable nonlinear performance of the PEMFC. This paper predicts the electrical performance of a PEMFC stack under various operating conditions. The four input terms for the 5 W PEMFC include anode and cathode pressures and flow rates. The model performances are based on ANN using two different learning algorithms to estimate the stack voltage and power. The models have shown consistently to be comparable to the experimental data. All models with at least five hidden neurons have coefficients of determination of 0.95 or higher. Meanwhile, the PEMFC voltage and power models have mean squared errors of less than 1 × 10−3 V and 1 × 10−3 W, respectively. Therefore, the model results demonstrate the potential use of ANN into the implementation of such models to predict the steady state behavior of the PEMFC system (not limited to polarization curves) for different operating conditions and help in the optimization process for achieving the best performance of the system.

Analysis of Electrode Degradation By High-Potential Environment-Using Electrochemical Impedance Spectroscopy in Polymer Electrolyte Membrane Fuel Cells

A Polymer electrolyte membrane fuel cell (PEMFC) is one of the most important applications for decarbonization of energy using hydrogen as an energy source and is considered a promising future power source due to its high efficiency, low operating temperature, fast startup, and low noxious emissions. In particular, improvement in durability of PEMFC is one of the major issues to spur the commercialization of the PEMFC system. Therefore, to improve the durability of PEMFC systems, diagnostic strategies are required to identify faulty conditions of PEMFC systems such as fuel starvation, dehydration, flooding, load cycling, and startup-shutdown (SU/SD). The problematic form of the membrane electrode assembly (MEA) that causes a decrease in the performance of PEMFCs in steady-state and dynamic operating conditions includes Pt dissolution, ionomer degradation, carbon corrosion [1] , and mechanical problems of the membrane in some circumstances. Among them, the undesired corrosion reaction, namely, the electrochemical carbon oxidation reaction, results in a drastic decrease in electrochemical double layer capacitance (EDLC), generation of oxygen functional groups in carbon supports, and severe electrochemical surface area (ECSA) fading [2, 3], followed by deteriorated PEMFC performance. Typically, the high potential inducing carbon corrosion reactions would occur during SU/SD and fuel starvation conditions. In detail, as for fuel starvation, a temporary shortage of H2 supply to one or several cells in a PEMFC stack causes the cell voltage reversal, accompanied by a potential strike over 1.0 V vs. RHE (Figure 1) with significant electrode degradation [4 , 5]. Also, the generation of hydrogen/air boundary at the anode due to the gas crossover through the membrane results in a high potential (~1.4 V vs. RHE), accelerating the decomposition of carbon support [6]. Therefore, in this work, to investigate the effects of high potential inducing electrode degradation on PEMFC performance, we conducted accelerated stress tests (AST), and in particular, we studied the correlation between electrode degradation behaviors as well as structural properties of porous carbon such as ionic resistance, EDLC with PEMFC performance in the systemic point of view. Specially, we could see the contrasting degradation behaviors and various performance decay rates using electrochemical impedance spectroscopy (EIS) analysis. EIS can be used to isolate the contribution of many processes to performance loss, allowing investigation of the effect of carbon corrosion-induced catalyst layer changes on fuel cell performance [ 7]. The measured EIS data is evaluated through the parametric fitting of the transmission line model (TLM) to the EIS spectrum. In addition, relaxation time distribution (DRT) analysis for direct analysis of internal resistance factors by reinforcing the TLM-based impedance analysis results was applied as a diagnostic method to evaluate electrode degradation. During the ASTs, electrochemical measurements (i-V, CV, LSV, and EIS) were performed to estimate the degree of PEMFC degradation, we also conducted ex-situ surface analysis of MEA using SEM, TEM, and XPS to elucidate the specific degradation components.

Robust nonlinear adaptive pressure control of polymer electrolyte membrane fuel cells considering sensor failures based on perturbation compensation

The large deviations between the partial pressure of oxygen and hydrogen can lead to severe membrane damage, which reduces the life of the polymer electrolyte membrane fuel cell (PEMFC). The deviation of pressure can be restrained by effective control of partial pressure. Considering the actual operating environment of PEMFC, its control system is not only affected by load changes, but also affected by some unknown disturbances, such as system parameter variations, failures, etc. Considering the above factors, this paper has proposed a robust nonlinear adaptive pressure control (RNAPC) employing the perturbation estimation technique to suppress the deviations. The proposed controller does not need to identify or estimate the system parameters in real time like the conventional controller based on parameter estimation technology, nor does it need to rely on the fault diagnosis and isolation technology to detect and estimate the failures in real time. It only uses the variations of system state variables caused by failures to provide the required failure information for the controller. In the design of RNAPC, an observer is designed to estimate a perturbation term containing system uncertainties, nonlinearities, and disturbances. The estimation of perturbation is used for the compensation of actual perturbation. Then, an adaptive FLC of PEMFC system can be realized. Therefore, the RNAPC requires only a few state measurements and is independent of an accurate system model. Simulation results show that the RNAPC method has smaller deviations of partial pressure of oxygen and hydrogen and better dynamic performance than traditional PI control under load disturbance, and obtains higher robustness against uncertainties and sensor failures than traditional PI control and FLC. The maximum error of partial pressure can be limited within 0.5% under four different simulation scenarios under the RNAPC.