Clean energy and the hydrogen economy Brandon, N. P.; Kurban, Z.
Philosophical transactions - Royal Society. Mathematical, Physical and engineering sciences/Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences,
07/2017, Letnik:
375, Številka:
2098
Journal Article
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In recent years, new-found interest in the hydrogen economy from both industry and academia has helped to shed light on its potential. Hydrogen can enable an energy revolution by providing much ...needed flexibility in renewable energy systems. As a clean energy carrier, hydrogen offers a range of benefits for simultaneously decarbonizing the transport, residential, commercial and industrial sectors. Hydrogen is shown here to have synergies with other low-carbon alternatives, and can enable a more cost-effective transition to de-carbonized and cleaner energy systems. This paper presents the opportunities for the use of hydrogen in key sectors of the economy and identifies the benefits and challenges within the hydrogen supply chain for power-to-gas, power-to-power and gas-to-gas supply pathways. While industry players have already started the market introduction of hydrogen fuel cell systems, including fuel cell electric vehicles and micro-combined heat and power devices, the use of hydrogen at grid scale requires the challenges of clean hydrogen production, bulk storage and distribution to be resolved. Ultimately, greater government support, in partnership with industry and academia, is still needed to realize hydrogen's potential across all economic sectors.
This article is part of the themed issue ‘The challenges of hydrogen and metals’.
This paper compares battery electric vehicles (BEV) to hydrogen fuel cell electric vehicles (FCEV) and hydrogen fuel cell plug-in hybrid vehicles (FCHEV). Qualitative comparisons of technologies and ...infrastructural requirements, and quantitative comparisons of the lifecycle cost of the powertrain over 100,000
mile are undertaken, accounting for capital and fuel costs. A common vehicle platform is assumed. The 2030 scenario is discussed and compared to a conventional gasoline-fuelled internal combustion engine (ICE) powertrain. A comprehensive sensitivity analysis shows that in 2030 FCEVs could achieve lifecycle cost parity with conventional gasoline vehicles. However, both the BEV and FCHEV have significantly lower lifecycle costs. In the 2030 scenario, powertrain lifecycle costs of FCEVs range from $7360 to $22,580, whereas those for BEVs range from $6460 to $11,420 and FCHEVs, from $4310 to $12,540. All vehicle platforms exhibit significant cost sensitivity to powertrain capital cost. The BEV and FCHEV are relatively insensitive to electricity costs but the FCHEV and FCV are sensitive to hydrogen cost. The BEV and FCHEV are reasonably similar in lifecycle cost and one may offer an advantage over the other depending on driving patterns. A key conclusion is that the best path for future development of FCEVs is the FCHEV.
Mathematical modelling is an essential tool for the design of solid oxide fuel cells (SOFCs). The present paper aims to report on the development of a dynamic anode-supported intermediate temperature ...direct internal reforming planar solid oxide fuel cell stack model, that allows for both co-flow and counter-flow operation. The developed model consists of mass and energy balances, and an electrochemical model that relates the fuel and air gas composition and temperature to voltage, current density, and other relevant fuel cell variables. The electrochemical performance of the cell is analysed for several temperatures and fuel utilisations, by means of the voltage and power density versus current density curves. The steady-state performance of the cell and the impact of changes in fuel and air inlet temperatures, fuel utilisation, average current density, and flow configuration are studied. For a co-flow SOFC operating on a 10% pre-reformed methane fuel mixture with 75% fuel utilisation, inlet fuel and air temperatures of 1023
K, average current density of 0.5
A
cm
−2, and an air ratio of 8.5, an output voltage of 0.66
V with a power density of 0.33
W
cm
−2 and a fuel efficiency of 47%, are predicted. It was found that cathode activation overpotentials represent the major source of voltage loss, followed by anode activation overpotentials and ohmic losses. For the same operating conditions, SOFC operation under counter-flow of the fuel and air gas streams has been shown to lead to steep temperature gradients and uneven current density distributions.
The redox flow battery (RFB) has been the subject of state-of-the-art research by several groups around the world. Most work commonly involves the application of various low-cost carbon-polymer ...composites, carbon felts, cloth, paper and their different variations for the electrode materials of the RFB. Usually, the carbon-polymer composite electrode has relatively high bulk resistivity and can be easily corroded when the polarised potential on the anode is more positive than that of oxygen evolution and this kind of heterogeneous corrosion may lead to battery failure due to electrolyte leakage. Therefore, carbon electrodes with high electrical conductivity, acid-resistance and electrochemical stability are highly desirable. This review discusses such issues in depth and presents an overview on future research directions that may help commercialise RFB technology. A comprehensive discussion is provided on the advances made using nanotechnology and it is envisaged that if this is combined with ionic liquid technology, major advantages could be realised. In addition the identification of RFB failure mechanisms by means of X-ray computed nano tomography is expected to bring added benefits to the technology.
•A comprehensive coverage on carbon materials used in redox flow batteries is given.•The influence of nanotechnology and graphene is discussed in detail.•The importance of studying RFB degradation mechanisms is emphasised.
Hydrogen production via steam electrolysis may involve less electrical energy consumption than conventional low temperature water electrolysis, reflecting the improved thermodynamics and kinetics at ...elevated temperatures. The present paper reports on the development of a one-dimensional dynamic model of a cathode-supported planar intermediate temperature solid oxide electrolysis cell (SOEC) stack. The model, which consists of an electrochemical model, a mass balance, and four energy balances, is here employed to study the steady state behaviour of an SOEC stack at different current densities and temperatures. The simulations found that activation overpotentials provide the largest contributions to irreversible losses while concentration overpotentials remained negligible throughout the stack. For an average current density of 7000
A
m
−2 and an inlet steam temperature of 1023
K, the predicted electrical energy consumption of the stack is around 3
kW
h per normal m
3 of hydrogen, significantly smaller than those of low temperature stacks commercially available today. However, the dependence of the stack temperature distribution on the average current density calls for strict temperature control, especially during dynamic operation.
► Durability of Ni–YSZ conventional anode supports under dry-reforming. ► Direct dry-reforming of methane in SOFCs. ► Carbon formation mechanics and morphology within Ni anodes fed by dry methane. ► ...CO2 mitigation for carbon formation in SOFC anodes.
The present work investigates the performance and degradation mechanisms of a Ni-based anode supported Solid Oxides Fuel Cells (SOFC) operating at ∼800°C on direct internal reforming of dry CH4–CO2 mixtures. The catalytic properties of the anode support were first studied in a micro-reactor configuration to determine safe conditions (i.e., without carbon formation) under which a dry conversion of the methane can occur directly within the fuel cell. A full electrochemical characterization of complete cells followed to preliminarily assess their resistance towards carbon formation when operating on direct dry-reforming. Ageing tests of ∼300h each have been performed in galvanostatic mode, with impedance spectra taken every 50h of continuous operation to monitor the trend over the time of the different polarization contributions. Post-mortem microstructural analysis was carried out after each experiment to verify the morphology and nucleation of carbon deposited in the anode electrode.
This paper gives a technical background to alkaline fuel cells (AFCs), introducing the advantages and drawbacks of the technology. AFCs offer the potential for low cost, mass producible fuel cells, ...without the dependency on platinum based catalysts and (currently) expensive membrane electrolytes. The AFC uses relatively low cost electrolytes based on aqueous bases such as potassium hydroxide. The inherent CO
2 sensitivity of the electrolyte can be addressed by filtering out the CO
2 from the air intake using a simple scrubber and periodically replacing the liquid electrolyte.
A review of the state-of-the-art in gas diffusion cathode development is given. The overall cell performance and stability is dominated by the behaviour of the cathode, leading to a focus of research effort on cathode development. The performance and durability of the gas diffusion electrode is very much dependent on the way in which the layer structures are fabricated from carbon and polytetrafluoroethylene (PTFE). The choice and treatment of the carbon support is of prime importance for the final catalytic activity. Noble metal and non-noble metal catalysts have been investigated and show good performance, however, more work is still needed on cathode durability to ensure the long term success of the alkaline fuel cell.
A major challenge—some would argue,
the major challenge facing our planet today—relates to the problem of anthropogenic-driven climate change and its inextricable link to our global society's present ...and future energy needs King, D.A., 2004. Environment—climate change science: adapt, mitigate, or ignore? Science 303, 176–177. Hydrogen and fuel cells are now widely regarded as one of the key energy solutions for the 21st century. These technologies will contribute significantly to a reduction in environmental impact, enhanced energy security (and diversity) and creation of new energy industries. Hydrogen and fuel cells can be utilised in transportation, distributed heat and power generation, and energy storage systems. However, the transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socioeconomic barriers to the implementation of hydrogen and fuel cells as clean energy technologies of the future. This paper aims to capture, in brief, the current status, key scientific and technical challenges and projection of hydrogen and fuel cells within a sustainable energy vision of the future. We offer no comments here on energy policy and strategy. Rather, we identify challenges facing hydrogen and fuel cell technologies that must be overcome before these technologies can make a significant contribution to cleaner and more efficient energy production processes.
After a brief survey of fuel cell types, attention is focused on material
requirements for SOFC and PEMFC stacks, with an introductory section on
materials technology for reformers. Materials cost ...and processing, together
with durability issues, are emphasized as these now dominate materials
selection processes for prototype stack units. In addition to optimizing the
cell components, increasing attention is being given to the composition and
processing of the bipolar plate component as the weight and volume of the
relevant material has a major influence on the overall power density and cost
of the fuel cell stack. It is concluded that the introduction of alternative
materials/processes that would enable PEMFC stacks to operate at
150-200°C, and IT-SOFC stacks to operate at 500-700°C,
would have a major impact on the successful commercialization of fuel cell
technology.
In order to improve lithium ion batteries it is important to characterise real electrode geometries and understand how their 3D structure may affect performance. In this study, high resolution ...synchrotron nano-CT was used to acquire 3D tomography datasets of mesocarbon microbead (MCMB) based anodes down to a 16 nm voxel size. A specimen labelling methodology was used to produce anodes that enhance the achievable image contrast, and image processing routines were utilised to successfully segment features of interest from a challenging dataset The 3D MCMB based anode structure was analysed revealing a heterogeneous and bi-modally distributed microstructure. The microstructure was quantified through calculations of surface area, volume, connectivity and tortuosity factors. In doing so, two different methods, random walk and diffusion based, were used to determine tortuosity factors of both MCMB and pore/electrolyte microstructures. The tortuosity factors (2-7) confirmed the heterogeneity of the anode microstructure for this field of view and demonstrated small MCMB particles interspersed between large MCMB particles cause an increase in tortuosity factors. The anode microstructure was highly connected, which was also caused by the presence of small MCMB particles. The complexity in microstructure suggests inhomogeneous local lithium ion distribution would occur within the anode during operation.
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