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Thermochemically Stable Novel Oxygen Carriers Based on CaMn1–x–yTixFeyO3−δ for Chemical Looping
Get PDFThe understanding and development of stable redox materials based on cheap and abundant elements, forming Ca–Mn–Ti–Fe–O-based perovskites, have been in focus for applications in renewable technologies such as chemical looping combustion and thermal energy storage. The present research focuses on developing stable materials to be utilized up to 1050 °C in a CLC process and has shown that the structure stability and oxygen transfer capacity can be achieved by tuning the content of different elements on B-sites of the perovskites. Various experiments, such as redox cycling under various fuels, temperatures, and pO2, were carried out to evaluate the oxygen transfer capacity, reaction rates under various fuels, etc. The redox stability at high temperatures was evaluated by redox cycles at 1050 °C followed by post SEM analyses on surface and depth profiling. The three developed materials can avoid phase change during redox due to the moderate oxygen transfer capacity of up to 5.6 wt % O2 for CaMn0.5Ti0.375Fe0.125O3−δ at 1050 °C, which is important for having stable particles. Cation diffusion was also investigated during redox cycling in the development of stable redox materials, and only a minor diffusion of Mn to the grain boundaries is seen in the least stable material. The findings show that perovskites with high stability can be obtained with more Ti on B-sites, termed as CaMn0.375Ti0.5Fe0.125O3−δ. The developed stable oxides, to some extent, have a reduced activity compared to the less stable composition with less Ti and more Mn, termed as CaMn0.5Ti0.375Fe0.125O3−δ, which possesses a higher oxygen release to inert ca. 1.1 wt % O2 compared to more stable CaMn0.375Ti0.5Fe0.125O3−δ that can release up to 0.8 wt % O2. Two of the materials have faster kinetics than ilmenite by a factor of 2 in H2.publishedVersio
Failure Consequence Cost Analysis of Wave Energy Converters—Component Failures, Site Impacts, and Maintenance Interval Scenarios
Get PDFIn the early stages of developing wave energy converter (WEC) projects, a quantitative assessment of component failure consequence costs is essential. The WEC types, deployment site features, and accessibility should all be carefully considered. This study introduces an operation and maintenance failure consequence cost (O&M-FC) model, distinct from conventional O&M models. The model is illustrated with case studies at three energetic Atlantic sites, each of which considers two types of generic floating WECs: a 300 kW point absorber (PA) with a hydraulic power-take-off (PTO) and a 1000 kW oscillating water column (OWC) with an air-wells-turbine PTO. This study compares 39 failure modes for PA and 27 for OWC in terms of direct repair costs and indirect lost production costs, examining the impact of location accessibility, capacity factors, and the mean annual energy production. The discussion revolves around the sensitive parameters. Recommendations for failure mitigations are presented, and the impact of planned maintenance (PM) during the operational phase is examined for 20 MW PA and OWC WEC projects. For a given WEC type, the method thoroughly evaluates how the location affects performance metrics. It offers a decision-making tool for determining optimal PM intervals to meet targets such as O&M costs, operating profit, or availability. Keywords: wave energy converter; failure mode; component criticality; O&M and FMECA metrics; maintenance mitigation; AtlanticFailure Consequence Cost Analysis of Wave Energy Converters—Component Failures, Site Impacts, and Maintenance Interval ScenariospublishedVersio
Calypso – Weathering properties and behaviour at sea - In relation to oil spill response
Get PDFA standardized bench-scale and meso-scale flume testing weathering study has been conducted on Calypso crude oil. The dispersibility testing was included to estimate the viscosity limits and the time window for dispersant use. The laboratory data were used as input to the SINTEF Oil Weathering Model (OWM) for weathering predictions from a surface release of Calypso at sea at 5 and 15 °C, reflecting winter and summer conditions. The weathering properties of Calypso are also discussed in relation to oil spill response.Calypso – Weathering properties and behaviour at sea - In relation to oil spill responsepublishedVersio
Analysing a grid-forming storage hub for an offshore platform cluster supplied by wind energy
Get PDFThis paper performs an analysis of the electrification of an of-the-grid offshore oil and gas cluster of six platforms by means of a wind farm combined with a hydrogen energy hub. The latter, whose model is made publicly available, contains a grid-forming battery system and grid-following electrolysis and fuel cells units. State-of-the-art aerodynamic simulations are used for representing the wind farm power output, which encompasses wake losses and correlated wind fuctuations between turbines arising from farm-scale turbulence. One of the offshore platforms is represented by a detailed publicly available model named LEOGO. The other five platforms are represented as aggregated mixes of constant power and constant impedance loads. The computer simulations presented in the paper provide valuable insights into furthering the design and optimization of the hub concept. These insights include, among others, sizing of batteries depending on maximum ramp rates of fuel cells and electrolysers, identifying and mitigating instabilities induced by interactions among power electronic converters, and evaluating the consequences for the converters when those contribute with voltage support at the hub.Analysing a grid-forming storage hub for an offshore platform cluster supplied by wind energypublishedVersio
A Volume-of-Fluid method for multicomponent droplet evaporation with Robin boundary conditions
Get PDFWe propose a numerical method tailored to perform interface-resolved simulations of evaporating multicomponent two-phase flows. The novelty of the method lies in the use of Robin boundary conditions to couple the transport equations for the vaporized species in the gas phase and the transport equations of the same species in the liquid phase. The Robin boundary condition is implemented with the cost-effective procedure proposed by Chai et al. [1] and consists of two steps: (1) calculating the normal derivative of the mass fraction fields in cells adjacent to the interface through the reconstruction of a linear polynomial system, and (2) extrapolating the normal derivative and the ghost value in the normal direction using a linear partial differential equation. This methodology yields a second-order accurate solution for the Poisson equation with a Robin boundary condition and a first-order accurate solution for the Stefan problem. The overall methodology is implemented in an efficient two-fluid solver, which includes a Volume-of-Fluid (VoF) approach for the interface representation, a divergence-free extension of the liquid velocity field onto the entire domain to transport the VoF, and the temperature equation to include thermal effects. We demonstrate the convergence of the numerical method to the analytical solution for multicomponent isothermal evaporation and observe good overall computational performance for simulating non-isothermal evaporating two-fluid flows in two and three dimensions.publishedVersio
Embrittlement, degradation, and loss prevention of hydrogen pipelines
Get PDFThe detrimental effects induced by hydrogen on different materials—including steels—are a well-known and studied phenomenon. In the last century, several research papers focusing on hydrogen damages were published, including investigations concerning the hydrogen impact on the crack growth rate in steels subjected to cyclic loading. However, the past studies focused on material behavior and the role of external factors (e.g., pressure, temperature, stress field, microstructure, inhibitors, etc.), while the consequences of these findings on safety procedures and guidelines remain unspoken. The present work aims at investigating how the manifestation of the hydrogen degradation effect on equipment subjected to fatigue loadings may reflect on conventional safety practices. More accurately, a review of the parameters governing pipeline fatigue life is undertaken to analyze how such variables may lead to undesirable events and ultimately promoting a loss of containment scenario. In this sense, this work appeals for an evolution of the existing inspection methodologies for components that may experience fatigue failures (i.e., piping and pipeline systems), since the time-dependency of the detrimental effects induced by hydrogen should be considered in the operations of accident prevention and risk mitigation. Hence, the development of a preventive inspection and maintenance strategy specifically conceived for hydrogen technologies is essential to avoid the loss prevention of hydrogen systems. This will not only contribute to a quicker and larger scale spread of a hydrogen infrastructure, but it will also foster the energy-transition challenge that our society is facing today.publishedVersio
Effect of Ni/SiO2 catalyst preparation method on methane decomposition and CO2 gasification cycles
Get PDFCatalytic methane decomposition is a promising reaction to produce CO2-free hydrogen from methane-rich feedstock with solid carbon as a by-product. Significant research conducted on this reaction to find ways to manage and utilize this solid carbon. In this work, the methane decomposition reaction is followed by Reverse Boudouard Reaction using CO2 feedstock to convert the solid carbon to carbon monoxide, which is a valuable starting component for many chemical applications. Realizing this promising concept would require a catalyst that is efficient for both reactions. Herein, we explored the potential of using solution combustion synthesis (SCS) to make a 5 wt% of Ni supported SiO2 catalyst and benchmarked it versus the conventional impregnation method. The catalyst prepared by SCS showed an improved performance at different temperatures, space velocities, and catalyst pellet sizes. The SCS catalyst successfully completed five repeated cycles reaching up to 38.1 h of stable time on stream operation, whereas the impregnated catalyst was not able to complete the second testing cycle with only 14 h of time on stream operation. A thorough characterization using XRD, H2 and O2 TPR, TEM, SEM, XPS, and Raman spectroscopy were conducted to provide an adequate explanation for the observed performances for both catalysts. The Ni nanoparticles size and distribution, the strength of the metal support interaction, and the nature of graphitic carbon were the key factors affecting the catalytic performance. Insights on how to make an optimal catalyst for this promising process is identified which is a step forward toward making separated H2 and CO streams from methane feedstock and CO2, respectively.publishedVersio
Recovery of Li, Co, Cu and Ni by Molten Salt Chlorination
Get PDFThe recent exponential growth in the Li ion batteries (LIB) market, is largely driven by the demand for electric vehicles and the general transition to a green and digital economy. It is therefore imperative to develop more effective and economic processes for recovering battery raw materials such as Li, Co, Cu and Ni. Moreover, these materials are all classified as critical or strategic (Cu, Ni) raw materials by the European Commission, and for Europe, it is of great importance to build a sustainable European supply chain for Li and other battery raw materials to decrease its dependency on import. In this work, we have studied the possibility to recover Li, Ni, Cu and Co from secondary raw materials like black mass (cathode and anode fraction from shredded end- of-life Li ion batteries), as well as Li from spodumene concentrate, spodumene being an important and available Li mineral. The approach has been to convert the metals in the raw materials to metal chlorides, by chlorination in LiCl-KCl (58 : 42) melts at 470 °C and CaCl2-NaCl-KCl (35 : 30 : 30) at 727 °C. With this method, the metals could potentially be reduced from the chloride matrix by subsequent sequential electrodeposition, utilizing their difference in nobility. Regarding black mass, the highest chlorination yields were obtained from uncalcined material (Li 64 %, Co and Ni 22–24 %, Cu 83 %, and Mn 49 %) in LiCl-KCl at 470 °C, the carbon in the black mass probably enhancing the chlorination rate. For spodumene concentrate, a high yield for Li (100 %) was obtained with Cl2 in CaCl2-NaCl-KCl at 727 °C, this melt composition being more oxoacidic and the higher temperature helping the chlorination kinetics.publishedVersio
Electrochemical Characterization of Silver and Iron Ions in Choline Chloride-Ethylene Glycol DES Electrolyte
Get PDFSolar energy is growing to be an important source of renewable energy in the world, and the need of recycling processes to recover the strategic materials used for this technology are necessary. Ag may be recovered from photovoltaic cells using a Deep Eutectic Solvent (DES), by selectively dissolving Ag from the waste to Ag(I) by use of an Fe(III)/Fe(II) redox couple before the recovery of Ag metal by electrowinning. Electrochemical characterization of Ag and Fe ions in ethaline DES showed that Ag, Ag(I), Fe(II) and Fe(III) ions are stable, and the standard potentials of the relevant reactions are sufficiently far from one another for the electrochemical recovery of Ag. Diffusion coefficient were estimated to be 1.77-4.16 ·10-7 cm2/s and 2.02-3.19 ·10-7 cm2/s for Ag(I) and Fe(II) ions, respectively. High quality Ag deposits were obtained with Fe ions in the solution, and with water content up to 10 wt% in the DES electrolyte.acceptedVersio
Observing fish behavior in towed fishing gear—is there an influence of artificial light?
Get PDFFish behavior is important to consider when developing selective fishing gear. In studies designed to investigate the size selective properties of towed fishing gears such as trawls, fish behavior is mainly documented by underwater video recordings. Because fishing gear can be operated at great depths or in other low light environments, artificial light is often required for underwater recordings. However, artificial light can influence fish behavior, which casts doubt on the validity of behavioral observations obtained in the presence of artificial light. However, removing artificial light disables video recordings and the possibility to study fish behavior in relation to selectivity devices towed fishing gears in low light environments. To date, little is known about the extent to which artificial light used for video observations affects fish behavior with respect to fishing gear. Therefore, we conducted fishing trials in the Barents Sea demersal trawl fishery to assess the effect of light sources on fish behavior by using size selectivity results in towed fishing gears. We found that the behavior of cod (Gadus morhua) was unaffected by the light sources, whereas the behavior of haddock (Melanogrammus aeglefinus), saithe (Pollachius virens) and redfish (Sebastes spp.) significantly changed when red light and white light were employed. Our results also demonstrated significant differences in fish behavior between white and red light.publishedVersio