Application of open pore cellular foam for air breathing PEM fuel cell

This is an accepted manuscript of an article published by Elsevier in International Journal of Hydrogen Energy on 07/06/2017, available online: https://doi.org/10.1016/j.ijhydene.2017.05.114 The accepted version of the publication may differ from the final published version.Open Pore Cellular Foam (OPCF) has received increased attention for use in Proton Exchange Membrane (PEM) fuel cells as a flow plate due to some advantages offered by the material, including better gas flow, lower pressure drop and low electrical resistance. In the present study, a novel design for an air-breathing PEM (ABPEM) fuel cell, which allows air convection from the surrounding atmosphere, using OPCF as a flow distributor has been developed. The developed fuel cell has been compared with one that uses a normal serpentine flow plate, demonstrating better performance. A comparative analysis of the performance of an ABPEM and pressurised air PEM (PAPEM) fuel cell is conducted and poor water management behaviour was observed for the ABPEM design. Thereafter, a PTFE coating has been applied to the OPCF with contact angle and electrochemical polarisation tests conducted to assess the capability of the coating to enhance the hydrophobicity and corrosion protection of metallic OPCF in the PEM fuel cell environment. The results showed that the ABPEM fuel cell with PTFE coated OPCF had a better performance than that with uncoated OPCF. Finally, OPCF was employed to build an ABPEM fuel cell stack where the performance, advantages and limitations of this stack are discussed in this paper

Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment

Metallic-based bipolar plates exhibit several advantages over graphite-based plates, including higher strength, lower manufacturing cost and better electrical conductivity. However, poor corrosion resistance and high interfacial contact resistance (ICR) are major challenges for metallic bipolar plates used in proton exchange membrane (PEM) fuel cells. Corrosion of metallic parts in PEM fuel cells not only increases the interfacial contact resistance but it can also decrease the proton conductivity of the Membrane Electrode Assembly (MEA), due to catalyst poisoning phenomena caused by corrosive products. In this paper, a composite coating of polytetrafluoroethylene (PTFE) was deposited on stainless steel alloys (SS304, SS316L) and Titanium (G-T2) via a CoBlast™ process. Corrosion resistance of the coated and uncoated metals in a simulated PEM fuel cell environment of 0.5 M H2SO4 + 2 ppm HF at 70 °C was evaluated using potentiodynamic polarisation. ICR between the selected metals and carbon paper was measured and used as an indicator of surface conductivity. Scanning Electron Microscopy (SEM), 3D microscopy, Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and contact angle measurements were used to characterise the samples. The results showed that the PTFE coating improved the hydrophobicity and corrosion resistance but increased the ICR of the coated metals due to the unconductive nature of such coating. Thus, it was concluded that it is not fully feasible to use the PTFE alone for coating metals for fuel cell applications and a hybrid coating consisting of PTFE and a conductive material is needed to improve surface conductivity.Enterprise Irelan

Developments in fuel cell technologies in the transport sector

The demand for clean power source which can be used to run the various types of vehicles on the road is increasing on a daily basis due to the fact that high emissions released from internal combustion engine play a significant role in air pollution and climate change. Fuel cell devices, particularly Proton Exchange Membrane (PEM) type, are strong candidates to replace the internal combustion engines in the transport industry. The PEMFC technology still has many challenges including high cost, low durability and hydrogen storage problems which limit the wide-world commercialization of this technology. In this paper, the fuel cell cost, durability and performances challenges which are associated with using of fuel cell technology for transport applications are detailed and reviewed. Recent developments that deal with the proposed challenges are reported. Furthermore, problems of hydrogen infrastructure and hydrogen storage in the fuel cell vehicle are discussed

Water droplet accumulation and motion in PEM (Proton Exchange Membrane) fuel cell mini-channels

Effective water management is one of the key strategies for improving low temperature Proton Exchange Membrane (PEM) fuel cell performance and durability. Phenomena such as membrane dehydration, catalyst layer flooding, mass transport and fluid flow regimes can be affected by the interaction, distribution and movement of water in flow plate channels. In this paper a literature review is completed in relation to PEM fuel cell water flooding. It is clear that droplet formation, movement and interaction with the Gas Diffusion Layer (GDL) have been studied extensively. However slug formation and droplet accumulation in the flow channels has not been analysed in detail. In this study, a Computational Fluid Dynamic (CFD) model and Volume of Fluid (VOF) method is used to simulate water droplet movement and slug formation in PEM fuel cell mini-channels. In addition, water slug visualisation is recorded in ex situ PEM fuel cell mini-channels. Observation and simulation results are discussed with relation to slug formation and the implications to PEM fuel cell performance

Wind/hydrogen hybrid systems: opportunity for Ireland’s wind resource to provide consistent sustainable energy supply

Ireland with its resource of wind has the potential to use this natural resource and sustain the country’s power needs for the future. However, one of the biggest drawbacks to renewable energy generation, particularly wind generated electricity is that it is an intermittent and a variable source of power. Even at the "best" sites wind varies dramatically from hour to hour and minute to minute. This leads to two main problems: 1) When the wind drops below a lower limit or goes above a higher limit the turbine can shut down and electricity is not produced. 2) Energy is not stored when there is an excess of electricity generated on site. Because of these problems wind power has a very low capacity credit and backup power is needed to handle the large fluctuation of production. This paper introduces the energy system of Ireland and the targets that Irish operators are to achieve in the next decade. A review of energy storage options for Ireland is outlined including the use of hydrogen and fuel cell technology. It is concluded that a project similar to the Norwegian Utsira wind / hydrogen project could be piloted in Ireland and a site similar to Dundalk Institute of Technology could be used to demonstrate and test the system. Going forward to achieve high levels of renewable energy generation, similar distributed wind / hydrogen hybrid systems could reduce the need for curtailment of wind farms, save wasted energy, reduce backup power, reduce transmission losses, generate large revenue by selling power at peak times, ensure security of supply and reduce the need for costly interconnects to Europe

Gaia focused product release: radial velocity time series of long-period variables

Stars and planetary system

Evidence of a rheotactic component in the odour search behaviour of freshwater eels

The detection of food odour by the freshwater eels, Anguilla australis and Anguilla dieffenbachii released a behavioural response to flow that resulted in direct upstream movement toward the odour source. Changes in various orientation parameters were observed as eels neared the source. Eels had substantially lower swimming velocities and considerably more variable heading and course angles close to the odour source (!0"9 m) than further away (>0"9 m). Observed changes in orientation parameters were primarily due to changes in the behaviour of a searcher following odour loss. Cross-stream movements were initiated when the eel moved beyond the lateral margins of the odour plume. The behavioural switch from odour-conditioned rheotaxis to cross-stream casting following odour loss occurred more frequently close to the odour source where the plume was most narrow. Odour-conditioned rheotaxis enables the searcher to move quickly and efficiently toward the odour source without the need to extract directional information from a highly intermittent and complex chemical signal

Earthy-muddy tainting of cultured barramundi linked to geosmin in tropical northern Australia

Tainting of outdoor pond-reared barramundi Lates calcarifer by muddy-earthy off-flavours is frequently reported across tropical Australia. To investigate the possible causes and effects of off-flavour tainting, we analysed water samples from outdoor rearing ponds for the presence of geosmin (GSM) and 2-methylisoborneol (2-MIB), 2 microbial metabolites often associated with tainting episodes. We then conducted controlled dose−effect experiments which measured the accumulation of tainting metabolites in the flesh, and the impact tainting had on taste and flavour attributes. GSM was deemed to be the compound most likely responsible for off-flavour tainting, persisting at moderate (~1.00 µg l⁻¹) to extreme levels (~14.36 µg l⁻¹), while 2-MIB was never detected during the study. Controlled experiments revealed that the accumulation of GSM in the flesh of market-sized barramundi was directly related to GSM levels of the holding water (0 to ~4 µg l⁻¹), with higher levels resulting in significant increases in undesirable taste and flavour attributes, particularly muddy-earthy flavour and weedy aftertaste. We identified the sensory detection threshold for GSM in farmed barramundi to be ≤0.74 µg kg⁻¹, similar to estimates for GSM detection in rainbow trout Oncorhynchus mykiss (~0.9 µg kg⁻¹) and for 2-MIB in channel catfish Ictalurus punctatus (0.7 µg kg⁻¹). Quantitative estimation of flesh-bound GSM using gas chromatography-mass spectrometry (GC-MS) agreed well with human sensory assessment scores and highlights the reliability of chemical analysis of GSM in barramundi flesh while also indicating the value of GC-MS analysis in predicting the impact of GSM on the sensory properties of farmed barramundi

Saltatory search in a lateral line predator

The dwarf scorpionfish Scorpaena papillosa detected the hydrodynamic signals produced by prey with the mechanosensory lateral line. This species displayed a pause and move search pattern that is consistent with a saltatory search. The pause phase of the search cycle was probably used to detect prey because pauses often ended early in order to initiate an approach at prey and prey were detected throughout the search space. The move phase of the search cycle repositioned the fish so that it moved approximately a third of the reactive distance. Move\ud distance was found to be the most important factor in gaining novel search space. Turning was shown to be relatively unimportant in gaining novel search space with a high frequency of low turn angles made by the fish. The dwarf scorpionfish, however, exhibited a spiralling or looping pattern over a search path exhibiting a turn bias towards either the left or right. The dwarf scorpionfish adopted a search behaviour that is consistent with a saltatory search and efficient for lateral line predation