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A particular challenge related to low temperature polymer electrolyte fuel cells (PEMFC) is to maintain high performance and long-term durability concurrently with the further reduction of Pt loading. These are conflicting goals because of a direct correlation of Pt surface with activity and Pt amount with durability. Moreover the lack of common procedures to reliably determine voltage loss rates leads to severe difficulties in the comparison of results obtained by different institutions or projects. Accordingly, special attention is devoted to the discrimination between irreversible and reversible voltage losses. Regarding the influence of Pt loading on PEMFC performance and durability our recent rainbow stack study performed in dynamic operation shows that for Pt/C based cathodes a sudden drop of performance is observed for loadings 1 Acm-2. A similar threshold value is found for the increase of irreversible voltage losses which lead to a reduction of PEMFC durability for cathodes with <=0.2-0.3 mgPt/cm2. Another durability issue at cathodic loadings <0.4 mgPt/cm2 is the acceleration of reversible degradation leading to a significant voltage drop at continuous fuel cell operation. The results show that the Pt loading of Pt/C based electrodes cannot be reduced below 0.2-0.3 mgPtcm-2 by just varying the thickness of the catalyst layers without suffering durability issue. To go below 0.2 mgPtcm-2 new electrode designs are needed. A special combination of coating techniques is also considered as promising approach to solve this issue. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for Fuel Cell and Hydrogen Joint Technology Initiative under Grant No. 303452 (Impact).

Presentado al II Iberian Syposium on Hydrogen, Fuel Cells and Advanced Batteries celebrado en Vila Real (Portugal) del 13 al 17 de septiembre de 2009. ; This work was supported by the project 'Avances en el modelo y diseño de controladores para sistemas basados en pila de combustible PEM' (4800). This work has been funded by the project CICYT DPI2007-62966 of the Spanish Government. ; Peer Reviewed

This paper presents a stationary and dynamic study of the advantages of using a regulating valve for the cathode outlet flow in combination with the compressor motor voltage as manipulated variables in a fuel cell system. At a given load current, the cathode input and output flowrate determine the cathode pressure and stoichiometry, and consequently determine the oxygen partial pressure, the generated voltage and the compressor power consumption. In order to maintain a high efficiency during operation, the cathode output regulating valve has to be adjusted to the operating conditions, specially marked by the current drawn from the stack. Besides, the appropriate valve manipulation produces an improvement in the transient response of the system. The influence of this input variable is exploited by implementing a predictive control strategy based on dynamic matrix control (DMC), using the compressor voltage and the cathode output regulating valve as manipulated variables. The objectives of this control strategy are to regulate both the fuel cell voltage and oxygen excess ratio in the cathode, and thus, to improve the system performance. All the simulation results have been obtained using the MATLAB-Simulink environment. ; This work was supported by the project 'Diseño de controladores para el proceso electroquímico en pilas de combustible de tipo PEM' (4796). This work has been funded partially by the project CICYT DPI2004-06871-C02-01 of the Spanish Government, and the support of the Department of Universities, Investigation and Society of Information of the Generalitat de Catalunya. ; Peer Reviewed

improvements in fuel economy and emissions of these vehicles directly depend on the type and operating point of the APU. These improvements should not only concern reducing operating and maintenance costs, but also emissions and noise. Improving an APU is, therefore, an important issue for all those directly or indirectly associated with an airport. This work deals with a High-Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) APU system used as a case study and suggested as a more sustainable alternative for the Airbus A320. Consequently, there are three main goals for this work, where the study and implementation of operational measures in a software tool using MATLAB is the key to accomplishing them. The first objective is to analyze several parameters of a HT-PEMFC, in order to predict the behavior of the fuel cell as a stack. In addition, since the operation of the stack depends on the fuel supplied to the system, which in this case is methane, and that methane cannot be directly fed to the HT-PEMFC, a previous fuel process is necessary. Therefore, Methane Steam Reforming and Water Gas Shifting processes are implemented to produce a hydrogen-rich gas with a low percentage of carbon monoxide. The maximum output power of this methane-supplied system is estimated at 250 kW for an operating temperature of 180ºC under 1.5 atm of pressure. The overall energy and exergy efficiencies achieved for this system are 41.29 % and 39.95 %, respectively. The second objective is to perform the thermodynamic analysis of HT-PEMFC APU based on the first and second laws of thermodynamics. The mass, energy, entropy, and exergy balance equations are written and applied to the system and its components. The irreversibilities occurring in different devices of the integrated system are investigated through the exergy destruction analysis in those units. The units with the most significant exergy destruction are associated with the chemical reactions that occur in them. The ultimate goal is to find the breakeven weight between the additional weight of the HT-PEMF proposed system and the fuel saved due to higher efficiency of the system. Moreover, it compares the emissions of the conventional APU and the HT-PEMFC systems, during a flight from Porto to Frankfurt carried out by an Airbus A320. Finally, the results of this research are very encouraging, and even though its fuel consumption saving potential is unlikely to be achieved in a real-world scenario due to the nature and unpredictability of air traffic, it is an attractive solution for countries facing ever stronger legislation to ensure cleaner air and a more sustainable future. ; Uma Unidade Auxiliar de Energia (APU) é um sistema bastante utilizado na produção de energia elétrica em aeronaves. Alcançar melhorias na economia de combustível desses veículos depende diretamente do tipo e do ponto de operação da APU. Essas melhorias devem estar focadas não só na redução dos custos de operação e manutenção, mas também na redução ou até mesmo eliminação de emissões e ruídos. A evolução de uma APU é, portanto, uma questão importante para todos aqueles que direta ou indiretamente estão associados a um aeroporto. Este trabalho aborda um sistema APU de uma célula de combustível de membrana polimérica de troca protónica de alta temperatura (HT-PEMFC) usado como caso de estudo e sugerido como uma alternativa mais sustentável para o Airbus A320. Por conseguinte, existem três objetivos principais para este trabalho, onde o estudo e a implementação de medidas operacionais de uma ferramenta de software através do MATLAB é a chave para realizá-las. O primeiro objetivo é analisar vários parâmetros de um HT-PEMFC, a fim de prever o comportamento da célula. Além disso, uma vez que a operação da pilha depende do combustível fornecido ao sistema, que neste caso é o metano, e que este não pode ser diretamente alimentado ao HT-PEMFC, é necessário o processamento do combustível. Para isso é feita uma Reforma de Metano a Vapor e uma Reação de Deslocamento de Água a fim de produzir um gás rico em hidrogénio e com uma baixa percentagem de monóxido de carbono. A máxima potência de saída deste sistema fornecido com metano é estimado em 250 kW para uma temperatura de operação da célula de 180? e sob uma pressão de 1.5 atm. As eficiências globais de energia e exergia alcançadas para este sistema são de 41.29 % e 39.95 %, respetivamente. O segundo objetivo é realizar a análise termodinâmica do sistema HT-PEMFC APU baseada na primeira e segunda leis da termodinâmica. As equações de balanço de massa, energia, entropia e exergia são escritas e aplicadas ao sistema e a cada um dos seus componentes. As irreversibilidades ocorridas nas diferentes unidades do sistema integrado são investigadas através da análise de exergia destruída nessa unidade. Deste modo, as unidades com maior destruição exergética estão associadas às reações químicas que nelas sucedem. O último objetivo tem como função encontrar o ponto de equilíbrio entre o aumento de peso do sistema proposto (HT-PEMFC APU) e o combustível economizado devido à sua maior eficiência. Visa ainda comparar as emissões de gases de escape entre os dois sistemas, para um mesmo voo realizado por um Airbus A320 entre Porto e Frankfurt. Finalmente, os resultados desta pesquisa são muito encorajadores, e mesmo que o seu potencial de economia seja improvável de ser alcançado num cenário real devido à natureza e imprevisibilidade do tráfego aéreo, é uma solução atraente para países que enfrentam uma legislação cada vez mais forte e, deste modo, garantir um ar mais limpo e um futuro mais sustentável.

The durability of polymer electrolyte membrane fuel cells (PEMFC) is governed by a nonlinear coupling between system demand, component behavior, and physicochemical degradation mechanisms, occurring on timescales from the sub-second to the thousand-hour. We present a simulation methodology for assessing performance and durability of a PEMFC under automotive driving cycles. The simulation framework consists of (a) a fuel cell car model converting velocity to cell power demand, (b) a 2D multiphysics cell model, (c) a flexible degradation library template that can accommodate physically-based component-wise degradation mechanisms, and (d) a time-upscaling methodology for extrapolating degradation during a representative load cycle to multiple cycles. The computational framework describes three different time scales, (1) sub-second timescale of electrochemistry, (2) minute-timescale of driving cycles, and (3) thousand-hour-timescale of cell ageing. We demonstrate an exemplary PEMFC durability analysis due to membrane degradation under a highly transient loading of the New European Driving Cycle (NEDC). ; The research leading to this work has been supported by the European Union's Seventh Framework Program for the Fuel Cells and Hydrogen Joint Technology Initiative under the project PUMA MIND (grant agreement no 303419). ; Peer Reviewed

FDFC 2017, 7th International Conference on Fundamentals & Development of Fuel Cells,, STUTTGART, ALLEMAGNE, 31-/01/2017 - 02/02/2017 ; Proton exchange membrane fuel cells (PEMFCs) appear nowadays to be a promising solution to face energy transition challenges in automotive applications. In this scenario, PEMFCs lifespan and their remaining Useful Life (RUL) under dynamic operations is currently object of main interest. This work introduces the fundamentals to design a generic strategy to support PEMFC durability enhancement in case of bus transportation applications. To this purpose, the energetic macroscopic formalism (EMR) is used to represent and model both the stack and the balance of plant (BoP) interactions. Based on power exchanges, each element will be related to another according to the action-reaction principle. The expected model will be able to simulate the system' response under a given load mission profile. Ageing behavior will be also considered in the model development. The model is expected to predict the voltage degradation profile with respect to the operating time and/or the produced energy. The voltage trend will be subsequently exploited by prognostic techniques to evaluate the PEMFC and BOP RUL and support their maintenance. This kind of approach is useful to integrate the existing diagnostic algorithms and support PEMFC makers in control decisions and maintenance scheduling as illustrated below. The research leading to these results has received funding from the European Union's Horizon2020 Programme (H2020-JTI-FCH-2015-1) for the Fuel Cells and Hydrogen Joint Undertaking, under grant agreement n° 700101 - Project : GIANTLEAP (Giantleap Improves Automation of Non-polluting Transportation with Lifetime Extension of Automotive PEM fuel cells).

FDFC 2017, 7th International Conference on Fundamentals & Development of Fuel Cells,, STUTTGART, ALLEMAGNE, 31-/01/2017 - 02/02/2017 ; Proton exchange membrane fuel cells (PEMFCs) appear nowadays to be a promising solution to face energy transition challenges in automotive applications. In this scenario, PEMFCs lifespan and their remaining Useful Life (RUL) under dynamic operations is currently object of main interest. This work introduces the fundamentals to design a generic strategy to support PEMFC durability enhancement in case of bus transportation applications. To this purpose, the energetic macroscopic formalism (EMR) is used to represent and model both the stack and the balance of plant (BoP) interactions. Based on power exchanges, each element will be related to another according to the action-reaction principle. The expected model will be able to simulate the system' response under a given load mission profile. Ageing behavior will be also considered in the model development. The model is expected to predict the voltage degradation profile with respect to the operating time and/or the produced energy. The voltage trend will be subsequently exploited by prognostic techniques to evaluate the PEMFC and BOP RUL and support their maintenance. This kind of approach is useful to integrate the existing diagnostic algorithms and support PEMFC makers in control decisions and maintenance scheduling as illustrated below. The research leading to these results has received funding from the European Union's Horizon2020 Programme (H2020-JTI-FCH-2015-1) for the Fuel Cells and Hydrogen Joint Undertaking, under grant agreement n° 700101 - Project : GIANTLEAP (Giantleap Improves Automation of Non-polluting Transportation with Lifetime Extension of Automotive PEM fuel cells).

[EN] The current environmental challenges require the implementation of environmentally friendly energy production systems. In this context, proton exchange membrane fuel cell stacks (PEMFC) represent, due to their high electrical efficiency and their low level of CO2 emissions, a promising alternative technology. However, there are still many technical aspects that need to be improved before they become a commercial reality. One of them is the temperature control of the stack, since its electrical efficiency and its lifetime depend on the performance of this control. In this work, we design a multiloop PID control of the temperature of a PEMFC stack and validate it experimentally. The stack is the prime mover of a micro combined heat and power system (micro-CHP). For this task, we use a previously developed nonlinear model and apply a multiobjective optimization methodology. To assess its performance, the PID control is compared to a second PID control designed with a linearized model. The results show, on the one hand, the importance of having a nonlinear model valid in a wide operation range for the correct design of the temperature control of a PEMFC stack and, on the other hand, the advantages of applying a multiobjective optimization methodology to this problem. ; This work was supported in part by the Spanish Ministry of Science, Innovation, and Universities under Grant RTI2018-096904-B-I00, and in part by the Generalitat Valenciana Regional Government under Project AICO/2019/055. ; Navarro-Giménez, S.; Herrero Durá, JM.; Blasco, X.; Simarro Fernández, R. (2020). Design and Experimental Validation of the Temperature Control of a PEMFC Stack by Applying Multiobjective Optimization. IEEE Access. 8:183324-183343. https://doi.org/10.1109/ACCESS.2020.3029321 ; S ; 183324 ; 183343 ; 8

The activity degradation of hydrogen-fed proton exchange membrane fuel cells (H2-PEMFCs) in the presence of even trace amounts of carbon monoxide (CO) in the H2 fuel is among the major drawbacks currently hindering their commercialization. Although significant progress has been made, the development of a practical anode electrocatalyst with both high CO tolerance and stability has still not occurred. Currently, efforts are being devoted to Pt-based electrocatalysts, including (i) alloys developed via novel synthesis methods, (ii) Pt combinations with metal oxides, (iii) core–shell structures, and (iv) surface-modified Pt/C catalysts. Additionally, the prospect of substituting the conventional carbon black support with advanced carbonaceous materials or metal oxides and carbides has been widely explored. In the present review, we provide a brief introduction to the fundamental aspects of CO tolerance, followed by a comprehensive presentation and thorough discussion of the recent strategies applied to enhance the CO tolerance and stability of anode electrocatalysts. The aim is to determine the progress made so far, highlight the most promising state-of-the-art CO-tolerant electrocatalysts, and identify the contributions of the novel strategies and the future challenges. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ; The authors thankfully acknowledge co-financing from the European Union and Greek national funds through the Operational Program for Competitiveness, Entrepreneurship, and Innovation, under the program RESEARCH-CREATE-INNOVATE (Project code: T1EDK-02442).