The status of research and development of polymer electrolyte membranes (PEMs) for direct methanol fuel cells (DMFCs) is described. Perfluorosulfonic acid membranes, e.g. Nafion, are widely used in ...fuel cell technology; but, despite their success, they show some drawbacks such as high cost, limited operating temperature range and high methanol crossover. These limit their widespread commercial application in DMFCs. Such disadvantages are inspiring worldwide research activities for developing new PEM materials based on non-perfluorinated polymers as alternative to Nafion for DMFCs. A review of membrane properties is carried out on the basis of thermal stability, methanol crossover and proton conductivity. The analysis of DMFC performance covers perfluorosulfonic acid membranes (PFSA), sulfonated aromatic polymers (SAPs) and composite membranes. PFSA membranes are suitable materials in terms of power density, SAPs are more advantageous regarding the low methanol permeability and cost, whereas composite membranes are more appropriate for operation above 100 °C. DMFC power density values reported in literature show that, although there are remarkable research efforts on this subject, the achieved results are not yet satisfying. Further work is especially necessary on non-perfluorinated polymers to improve performance and durability for an effective application in practical DMFC devices.
•This review discusses recent advances in polymer electrolyte membranes for DMFCs.•The PFSA and SAP membranes show remarkable performances at temperatures up to 90 °C.•The composite membranes appear more suitable for DMFC applications above 100 °C.
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•New Power-to-Gas system with thermal integration of co-electrolysis and methanation.•Different configurations modelled and analyzed in ASPEN Hysys™ environment.•Performance indexes for efficiency ...and quality of produced synthetic natural gas.•Effects of heat recovery and pressurization on system performance evaluation.•Thermal integration feasibility demonstration.
Performance of an innovative storage system for renewable energy, based on the Power-to-Gas concept are numerically predicted. The investigated system is composed by a high temperature co-electrolyzer of Solid Oxide Electrolyte Cell technology and an experimental methanation section, based on structured catalyst, suitable for high temperature operation. With the aim to thermally integrate high temperature co-electrolysis and methanation, a parametric thermodynamic analysis of the Power-to-Gas system is carried-out with a lumped-parameters approach, including all the thermal and electric energy consumptions. In particular, in order to optimize the system thermal balance of plant, various configurations involving internal heat recovery and pressurization of components are also considered. Numerical results are provided in terms of different performance indicators, such as electric-to-fuel conversion index, first law efficiency and second law efficiency and output-fuel quality indicators. The study demonstrates the possibility to thermally integrate the co-electrolyzer and the high-temperature methanation section achieving significant energy savings. Moreover, the calculated results show that the system set-up providing higher quality of the produced synthetic natural gas do not always lead to larger values in energy conversion efficiency. Eventually, advanced configurations of the Power-to-Gas system including heat recovery allow to achieve first-law efficiency up to values around 80–85% and second-law efficiency around 70–78%; a second methanation section based on conventional low-temperature reactors is included in the system and pressurization of the methanation section, or pressurization of the co-electrolysis section, is mandatory, in order to achieve large fraction of methane (up to 95–99%) in the produced synthetic fuel.
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Schematic illustration of a SOFC operating with direct utilization of dry fuels. Display omitted
► Ni was mainly present as highly dispersed La2NiO4 particles on the perovskite. ► The advantage of ...this new anode consists in the direct utilization of dry fuels. ► A reasonable steady-state performance was reached under all reaction conditions. ► No carbon and good performance were detected for the SOFC anode. ► Mixed conductivity of the CGO electrolyte affected the electrical efficiency.
This study deals with an investigation of the direct oxidation of organic fuels with different molecular weights in Solid Oxide Fuel Cells (SOFCs). It aims to demonstrate that the final products of the oxidation process are essentially CO2 and water with a very low amount of secondary products. An anodic catalyst formulation characterized by mixed electronic–ionic conductivity (MIEC) in combination with ceria electrolyte was used for this purpose. The anodic catalyst consisted in a composite Ni-modified perovskite mixed with Ce0.9Gd0.1O2. It provided reasonable fuel flexibility in SOFCs. To get insight into the reaction mechanism, the same anode formulation was investigated in an ex-situ autothermal reforming test. The performances achieved with the direct utilization of both gaseous and liquid fuels appear promising for SOFC applications in remote and micro-distributed energy generation as well as for portable power sources. The anode layer demonstrated stable performance with very low amount of carbon deposition during more than 130h testing under a direct utilization mode of dry organic fuels.
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Technological improvements in direct methanol fuel cells (DMFCs) are fuelled by their exciting possibilities in portable, transportation and stationary applications. In this paper, a synopsis of the ...worldwide efforts resulting in inventions of a plethora of DMFC prototypes with low, medium and high power capacities by a number of Companies, Research Institutions and Universities is presented. The most promising short term application of DMFCs appears to involve the field of portable power sources. Recent advances in the miniaturization technology of DMFCs devices make these systems attractive to replace the current Li-ion batteries. In the field of electrotraction recent demonstration of DMFC stacks with specific power densities and efficiencies approaching those of the combined system methanol reformer-polymer electrolyte fuel cell (PEMFC) have stimulated further investigation on the development of materials with higher performance and lower cost. The most appropriate range of operation temperatures for applications in transportation appears to lie between 100 and 150
°C. These operating conditions may be sustained by using new high temperature electrolyte membranes or composite perfluorosulfonic membranes containing inorganic materials with water retention properties at high temperature. The most challenging problem for the development of DMFCs is the enhancement of methanol oxidation kinetics. At present, there are no practical alternatives to Pt-based catalysts. High noble metal loading on the electrodes and the use of perfluorosulfonic membranes significantly contribute to the cost of these devices. Critical areas include the design of appropriate membrane electrode assemblies for specific DMFC applications and the reduction of methanol cross-over. This latter aspect is strictly related to the use of membrane alternatives to Nafion, but it may also be conveniently addressed by the development of methanol-tolerant oxygen reduction catalysts.
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TiO2 nanometric powders were prepared via a sol-gel procedure and calcined at various temperatures to obtain different surface and bulk properties. The calcined powders were used as fillers in ...composite Nafion membranes for application in high temperature direct methanol fuel cells (DMFCs). The powder physico-chemical properties were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and pH measurements. The observed characteristics were correlated to the DMFC electrochemical behaviour. Analysis of the high temperature conductivity and DMFC performance reveals a significant influence of the surface characteristics of the ceramic oxide, such as oxygen functional groups and surface area, on the membrane electrochemical behaviour. A maximum DMFC power density of 350 mW cm -2 was achieved under oxygen feed at 145 DGC in a pressurized DMFC (2.5 bar, anode and cathode) equipped with TiO2 nano-particles based composite membranes.
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•A novel design methodology for NZEBs design.•A coherent framework for the implementation of NZEBs into the existent power grids.•Use of batteries at building scale largely decreases ...the reliance on power grid.•SOFC fed by natural gas allows a good load match at high energy efficiency.
The concept of Net Zero Energy Building (NZEB), as a grid-connected building that generates as much energy as it uses over a given period, has been developing through policies and research agendas during the last decade as a contribution towards the decarbonization of the building sector. However, since the most applicable and widely used renewable energy supply options are non-programmable, the large-scale NZEBs diffusion into the existing power grids can seriously affect their stability having a relapse on operation costs and environmental impacts.
In this context, the study aims at performing the design of the energy systems to be used in the case-study through a wide numbers of point of views, including the grid interaction, global warming potential, and different design alternatives such as using fuel cells and renewable energy generation systems and drawing lessons learned to be saved for similar buildings.
A novel approach for developing for NZEBs, combining load match and grid interaction indicators with an environmental impact indicator, is proposed. The proposed design approach allows for the quantification of the power grid interaction and environmental impact (in terms of Global Warming Potential) aiming to find trade-offs between the opposing tendencies of building energy performances and the need to limit the embodied carbon within building envelope and systems.
The design approach has been used to investigate the performances of a NZEB prototype with the aim to explore the effectiveness of the solution sets used in the current design (only Photovoltaic system) and plan different solutions (batteries and fuel cells system) for the future ones.
For the base case, even though the overall PV energy generation (8069 kWhe) in a year surpasses the electricity consumption (5290 kWhe), on a yearly base only the 29% of the PV generation is used on-site. Hence, the assessed indicators show clearly how installing a PV system merely able to cover the energy uses on a yearly net base (or even slightly oversized) will have stress implications on the power grid.
On the other hand, the use of batteries at the building scale largely decreases the reliance on power grid when not programmable renewable sources are present. Moreover, if coupled to the right size of the on-site generation systems, the storage system could increases the environmental benefits arising from the renewable energy technologies (the GHG emission reaches its minimum value of 0.92·103 kg CO2eq/year, with a reduction of the 50.4% if compared to the base case) for a storage capacity of 20 kWh and a PV system nominal power of 4.56 kW).
Fuel cells guarantee a good load match at high energy efficiency, furthermore, a high installed power of fuel cells is not required to obtain high load cover factor values. On the other hand, since the specific CO2eq emission per unit of energy of the fuel cells are high, the CO2eq emissions are always greater than those of the base case if the system is equipped with a fuel cell system. Therefore, future research will have to focus on the eco-design of fuel cells with to reduce environmental impacts of these systems in a life cycle perspective.
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The potentiality of carbon nanotubes as reinforcement material is not only due to their exceptional high modulus, but also to their high aspect ratio. Indeed, the nanotubes contribution to the ...mechanical reinforcement in a polymer is strongly dependent on their distribution within the hosting matrix. In fact, the clustering of carbon nanotubes does limit the theoretical enhancement of the composite mechanical properties by a reduction of their effective aspect ratio.
In this work, the reinforcement efficiency of carbon nanotubes having different aspect ratios has been experimentally investigated at low filler contents in an epoxy system. From a theoretical point of view, the classical theory (Cox, 1952
25) concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube Random Contact Model (Philipse, 1996
33) which explicitly accounts for the progressive reduction of the tubes effective aspect ratio as the filler content increases. The validity of the proposed model was assessed by a comparison with available literature data, providing a good agreement.
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The purpose of hybridization is to obtain a new material preserving advantages from all of its constituents. Hybridization offers intermediate properties respect to the original materials, by ...creating a balance effect within the fibres incorporated in the composite materials and leading to a composite with more tailored behaviour The increasing need to mitigate the environmental impact of synthetic fibres and polymers is promoting the use and application of natural materials orienting the research toward the development of biodegradable systems.
In this framework, hybrid reinforced laminates with flax and basalt twill layers alternatively stacked, were manufactured by resin infusion fabrication technology and impacted at low velocity to investigate their dynamic behaviour, in an attempt to couple the impact resistance of basalt fibres with the environmentally friendly nature of flax fibres. For comparison purposes, the same experimental characterization has been performed on laminates reinforced with only basalt or flax fibres. The experimental results confirmed the positive role played by fibre hybridization in terms of damage.
The Electronic Speckle Pattern Interferometry technique was adopted to analyze the internal damage and to provide information on the shape and the extent of the delamination, that was found concentrated under the impactor-material contact point for the basalt and flax/basalt laminates.
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