• Energy Research

A polymer electrolyte fuel cell stack of 2 kW of peak power has been designed, manufactured and tested. Such a fuel cell stack has been envisaged to be applied for manned lunar exploration missions, as secondary energy source for both mobile vehicles and fixed power plants. The stack has been bread-boarded in order to test and demonstrate the technology. The following constraints have been considered during the study: (i) operation with pure hydrogen and oxygen (ii) low humidification levels (iii) use of commercial Membrane Electrode Assemblies. The breadboard has been made consisting of two modules, each of 500 W of nominal power. Specific tests have been conducted to prove the effect of gravity on the breadboard performance and verify its ability to follow variable load profiles over time, representative of different lunar surface exploration missions. The breadboard has shown a good performance during the test campaign, even if some failures of the Membrane Electrode Assemblies have been observed. The study has demonstrated the high performance of the developed stack and the potential of fuel cell technology for use in future human lunar exploration missions. At the same time, it has highlighted serious criticalities related to the reliability and robustness of the commercially available Membrane Electrode Assemblies, which need to be investigated further, before the use of this technology in a real space exploration mission can be possible.

Reactants distribution over the active area plays a key role in the performance of PEM fuel cell. The flow path that is designed to uniformly distribute fuel and oxidant over the active area, has also to respect some geometrical constraints such as the active area shape. Serpentine layout has been proven as efficient design especially at cathode, due to the fluid motion established in the flow field. A convective flow through the gas diffusion layer, also called cross flow, has been demonstrated to be responsible for a better PEM fuel cell performance using serpentine flow channels. As highlighted in previous studies the intensity of the cross flow is affected by several parameters, such as the thickness and permeability of the gas diffusion layer and the serpentine path length, even though the correlation between the cross flow intensity and the fuel cell active area shape factor (MEA width/height) has never explored before. In this work a numerical and experimental study has been carried out to investigate the effect of the active area shape factor on the cross flow intensity and its effect on the fuel cell performance. Three-dimensional CFD simulation, including electrochemical aspects, has been performed for two different serpentine flow paths extending over the same active area but different in shape factor. The effect of reactants stoichiometry and humidification on the fuel cell performance have been also envisaged. Numerical computations has shown that cross over flow intensity is higher in the flow field with the lowest area shape factor. In terms of electrochemical performance, this flow field operates better at higher current density because the high intensity of cross flow enhances reactants concentration and improves water removal from the gas diffusion layer. Experimental tests have also been performed for a comparison with numerical results.

The operative conditions influence the performance of a polymer electrolyte fuel cell (PEFC). In particular, when a multi-cell (stack) instead of a single cell is investigated, a proper water management and flow stoichiometric ratio are essential for obtaining high electrical conversion efficiency. In this paper, a five cell air cooled PEM fuel cell stack was designed and realized, and systematic studies on the influence of the reactants humidification have been carried out to optimize the operative conditions. Polarization curves and time test at a fixed current have been conducted for various cathode (RHC) and anode (RHA) inlet humidity conditions. In particular, a small decay and low performance were obtained for RHA and RHCo70% and a considerable decay and low performance for RHA and RHC470%. A good compromise for water management, in terms of decay and performance, is obtained when a symmetrical RH of 70% was used, because in this case an optimal water balance was probably reached considering that high flow of gases was used. In fact, insufficient water content implies a lower ion conductivity of the membrane whereas excess of water yields to flooding of the electrodes and parasitic losses due to the presence of water in the gas channels. Consequently, these effects lead to a lowering of voltages during lifetime tests. In any case, the cathode RH has a stronger influence on the stack decay compared to the anode one. In the optimal selected conditions of RH a constant and stable power of about 55W (at 20 A) was obtained during the 15 h of operation.

Report tecnico sul prototipo di stack PEM di taglia 2-5 kW alimentato ad idrogeno ed ossigeno puro realizzato nell'ambito del progetto TecBIA coordinato da Fincantieri

In a green future, Fuel cells will probably become the suitable environmental friendly technology to generate power for several applications. They, in fact, generate electricity by an electrochemical process; in particular, Polymer Electrolyte fuel cells (PEMFC) use hydrogen and air as reactants, in combination with a solid, proton conductor electrolyte. Due to the complexity of the phenomena that take place inside a PEM fuel cell, scientists have focused their attention on different points, from the electrochemistry towards the fluid dynamics to mechanics. As well as the electrochemical components play a key role in the performance of a fuel cell, the distribution of the reactants over the electrode surfaces is fundamental for an optimal operation of the device. To understand PEMFC systems, a detailed analysis of the influence of main parameters on its performance and the development of different in situ analytical methods is fundamental. Segmented current collector (SCC) have proven to be an excellent in situ diagnostic tool, to a deep understanding on how a fuel cell works and to study the factors influencing the uneven electrochemical response of the Membrane Electrode Assembly (MEA). A SCC is similar to an ordinary fuel cell current collector with the exception that it is divided into smaller ones that can be individually interrogated for current, voltage and temperature.

In this work, a new family of zeolite coatings and an innovative heat exchanger concept are presented. Zeolite SAPO-34 coatings have been prepared and deposited on high-density graphite plates to investigate the feasibility of a new concept of adsorber for adsorption chillers. Different coating formulations have been prepared and characterized. Results demonstrated that SAPO-34 coatings maintain the characteristic adsorption properties of the native zeolite, develop an optimum bonding to the graphite plates and make it possible to improve the coating process for a better control of the layer thickness, in order to obtain different values of the final zeolite/support mass ratio. Finally, the schematic of an innovative graphite exchanger for heat pumps and chillers is provided. A bonded plate configuration have been adopted to remove bulky and heavy components such as the clamping plates. To this end experimental work have been conducted to address the suitable adhesive foe bonding the heat exchanger plates. The external shapes have been designed on the basis of the characterizations performed on small-scale samples, whereas inner fluid paths (heat transfer fluid side) have been developed by using Computational Fluid Dynamics in order to enhance heat transfer rate and temperature uniformity on the plate surface. Further, the main components of a full scale advanced exchanger has been showed and described. © 2014 Elsevier Ltd. All rights reserved.

The focus of this chapter is the design of a direct methanol fuel cell (FC) (DMFC) stack. In particular, the design of bipolar plates will be addressed and the reader will be able to build his own FC stack and design bipolar plates based on the desired performance. The discussion will be intentionally inspired by simplicity and intends to provide immediately usable tools and solutions, which are based on the direct experience of the authors [110]. The trip into the word of DMFC stack design starts from some recalls of thermodynamics and electrochemical, which are fundamental for choosing the operation point of the FC stack and the calculation of the flow rate of the reactants. Once the flow rates are known, the architecture of the FC stack can be defined, on the basis on the application, and the rest of FC stack components can be designed. This chapter covers the DMFC stack design principles, including stack architecture, reactants distribution, heat management, and stack clamping. The chapter aims to provide some useful guidelines to optimize the DMFC stack design and performance, a topic less covered in FC literature. In the following discussion, if not explicitly indicated, the sign of all numerical values is to be considered positive.

Hydrogen leakage in Proton Exchange Membrane (PEM) fuel cells poses critical safety, efficiency, and operational reliability risks. This study introduces an innovative infrared (IR) thermography-based methodology for detecting and quantifying hydrogen leaks towards the outside of PEM fuel cells. The proposed method leverages the catalytic properties of a membrane electrode assembly (MEA) as an active thermal tracer, facilitating real-time visualisation and assessment of hydrogen leaks. Experimental tests were conducted on a single-cell PEM fuel cell equipped with intact and defective gaskets to evaluate the method’s effectiveness. Results indicate that the active tracer generates distinct thermal signatures proportional to the leakage rate, overcoming the limitations of hydrogen’s low IR emissivity. Comparative analysis with passive tracers and baseline configurations highlights the active tracer-based approach’s superior positional accuracy and sensitivity. Additionally, the method aligns detected thermal anomalies with defect locations, validated through pressure distribution maps. This novel, non-invasive technique offers precise, reliable, and scalable solutions for hydrogen leak detection, making it suitable for dynamic operational environments and industrial applications. The findings significantly advance hydrogen’s safety diagnostics, supporting the broader adoption of hydrogen-based energy systems.

Fuel cells are very promising technologies for efficient electrical energy generation. The development of enhanced system components and new engineering solutions is fundamental for the large-scale deployment of these devices. Besides automotive and stationary applications, fuel cells can be widely used as auxiliary power units (APUs). The concept of a direct methanol fuel cell (DMFC) is based on the direct feed of a methanol solution to the fuel cell anode, thus simplifying safety, delivery, and fuel distribution issues typical of conventional hydrogen-fed polymer electrolyte fuel cells (PEMFCs). In order to evaluate the feasibility of concrete application of DMFC devices, a cost analysis study was carried out in the present work. A 200 W-prototype developed in the framework of a European Project (DURAMET) was selected as the model system. The DMFC stack had a modular structure allowing for a detailed evaluation of cost characteristics related to the specific components. A scale-down approach, focusing on the model device and projected to a mass production, was used. The data used in this analysis were obtained both from research laboratories and industry suppliers specialising in the manufacturing/production of specific stack components. This study demonstrates that mass production can give a concrete perspective for the large-scale diffusion of DMFCs as APUs. The results show that the cost derived for the DMFC stack is relatively close to that of competing technologies and that the introduction of innovative approaches can result in further cost savings.