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Integration of Chemical Looping Combustion in the Graz Power Cycle
Get PDFEffective decarbonization of the power generation sector requires a multi-pronged approach, including the implementation of CO2 capture and storage (CCS) technologies. The Graz cycle features oxy-combustion CO2 capture in a power production scheme which can result in higher thermal efficiencies than that of a combined cycle. However, the auxiliary consumption required by the air separation unit to provide pure O2 results in a significant energy penalty relative to an unabated plant. In order to mitigate this penalty, the present study explores the possibility of chemical looping combustion (CLC) as an alternative means to supply oxygen for conversion of the fuel. For a midscale power plant, despite reducing the levelized cost of electricity (LCOE) by approximately 12.6% at a CO2 tax of EUR 100/ton and a natural gas price of EUR 6.5/GJ and eliminating the energy penalty of CCS relative to an unabated combined cycle, the cost reductions of CLC in the Graz cycle were not compelling relative to commercially available post-combustion CO2 capture with amines. Although the central assumptions yielded a 3% lower cost for the Graz-CLC cycle, an uncertainty quantification study revealed an 85.3% overlap in the interquartile LCOE range with that of the amine benchmark, indicating that the potential economic benefit is small compared to the uncertainty of the assessment. Thus, this study indicates that the potential of CLC in gas-fired power production is limited, even when considering highly efficient advanced configurations like the Graz cycle.publishedVersio
Complementarity-constrained predictive control for efficient gas-balanced hybrid power systems
Get PDFControlling gas turbines (GTs) efficiently is vital as GTs are used to balance power in onshore/offshore hybrid power systems with variable renewable energy and energy storage. However, predictive control of GTs is non-trivial when formulated as a dynamic optimisation problem due to the semi-continuous operating regions of GTs, which must be included to ensure complete combustion and high fuel efficiency. This paper studies two approaches for handling the semi-continuous operating regions of GTs in hybrid power systems through predictive control, dynamic optimisation, and complementarity constraints. The proposed solutions are qualitatively investigated and compared with baseline controllers in a case study involving GTs, offshore wind, and batteries. While one of the baseline controllers considers fuel efficiency, it employs a continuous formulation, which results in lower efficiency than the two proposed approaches as it does not account for the semi-continuous operating regions of each GT.publishedVersio
Integrating Process Simulation and Life Cycle Assessment for Enhanced Process Efficiency and Reduced Environmental Impact in Ferromanganese Production
Get PDFProcess simulation was integrated with life cycle assessment to evaluate process efficiency and environmental impact of the production of manganese ferroalloys for various production modes and different ore mineralogies. Utilizing HSC Sim, the model was designed to evaluate the production process with or without a pretreatment step, where results for simulated cases using a four-zone ferromanganese furnace model were exported to openLCA for a complete life cycle assessment. Two main production scenarios were simulated: a closed ferromanganese furnace running on the duplex method and an open furnace running on the discard slag approach. The closed furnace scenario achieved a 17.5% reduction in energy consumption and a 16.2% decrease in direct CO2 emissions with CO-rich off-gas pretreatment. The open furnace scenario showed an 11.2% reduction in energy consumption with thermal solar energy pretreatment but no change in CO2 emissions.publishedVersio
Intelligent Ship Transport System - Onboard Maritime ICT Architecture and Standards
No full textThis report defines an ICT architecture for the onboard computer-based systems on a ship. It gives an overview of the protocol standards and data models that are commonly in use on ships. The emphasis is on system connectivity and the ability to get information from the different systems and how to transfer information between ship and shore Cyber security is an important issue in all aspects related to information transfers between protected and unprotected networks. Physical security is part of this, but not a central aspect in this report. The report is fairly exhaustive with regards to protocols described but it is also clear that very few ships have full connectivity between all equipment onboard. There is also a lack of uptake of already available standards that to some degree hinders data collection from ships.Intelligent Ship Transport System - Onboard Maritime ICT Architecture and StandardspublishedVersio
Biomass estimations of cultivated kelp using underwater RGB images from a mini-ROV and computer vision approaches
Get PDFSeaweed farming is the fastest-growing aquaculture sector worldwide. As farms continue to expand, automated methods for monitoring growth and biomass become increasingly important. Imaging techniques, such as Computer Vision (CV), which allow automatic object detection and segmentation can be used for rapid estimation of underwater kelp size. Here, we segmented in situ underwater RGB images of cultivated Saccharina latissima using CV techniques and explored pixel area as a tool for biomass estimations. Sampling consisted of underwater imaging of S. latissima hanging vertically from a cultivation line using a mini-ROV. In situ chlorophyll a concentrations and turbidity (proxies for phytoplankton and particle concentrations) were monitored for water visibility. We first compared manual length estimations of kelp individuals obtained from the images (through manual annotation using ImageJ software). Then, we applied CV methods to segment and calculate kelp area and investigated these measurements as a robust proxy for wet weight biomass. A strong positive linear correlation (r2 = 0.959) between length estimates from underwater image frames and manual measurements from the harvested kelp was observed. Using unsupervised learning algorithms, such as mean shift clustering, colour segmentation and adaptive thresholding from the OpenCV package in Python, kelp area was segmented and the number of individual pixels in the contour area was counted. A positive power relationship was found between length from manual measurements with CV-derived area (r2 = 0.808) estimated from underwater images. Likewise, CV-derived area had a positive power relationship with wet weight biomass (r² = 0.887). When removing data where visibility was poor due to high turbidity levels (mid-June), the power relationship was stronger between CV-derived area estimates and the field measurements (r² = 0.976 for wet weight biomass and r² = 0.979 for length). These results show that robust estimates of cultivated kelp biomass in situ are possible through kelp colour segmentation. However, we demonstrate that the quality of CV post-processing and accuracy of the model are highly dependent of environmental conditions (e.g. turbidity and chlorophyll a concentrations). The establishment of these technologies has the potential to offer scalability of production, efficient real-time monitoring of sea cultivation and improved yield predictions.publishedVersio
CFD of a Flow Conditioning Unit
Get PDFAn open challenge related to subsea well compression is avoiding surges and slugs into a wet gas compressor station. A Flow Conditioning Unit (FCU) helps to dampen the sudden changes that are caused by variations in multiphase flow patterns. Computational Fluid Dynamics (CFD) transient simulations are performed on a high-performance computing cloud to verify and improve the design of the FCU in terms of sizing and liquid handling capacity. The simulations are performed using the Volume of Fluid (VOF) method, employing adaptive meshing approach to simulate complex gas liquid dynamics under various flow conditions. Ultimately, these simulations lead to optimized design of the FCU unit and its test facility. Furthermore, multiphase CFD simulations are further utilized during large scale experiments for better understanding of observed flow behavior. Some of the phenomena to be shown are large liquid entrainment in gas harp and the presence of gas in liquid draining lines. This work shares details on the CFD simulations performed, including the mesh size development, wall-time required, and post-processing tools utilized. However, the focus is to show how an industrial actor leverages CFD tools to iterate on expensive testing infrastructure, thereby reducing risk and cost.publishedVersio
Experiences from the introduction of a hybrid energy and capacity-based distribution grid tariff in Norway
Get PDFThe electrification of society increases the strain on the existing electricity infrastructure. Grid tariffs can be used to incentivize lowered customer peak electricity demand and more efficient usage of existing energy infrastructure, thus mitigating costly upgrades of the electricity grid. A public consultation on new tariffs was performed in Norway 2015, and in 2019 the research project ForTa was established with the aim of realizing demand response and reduced investments through an improved introduction of new capacity-based tariffs. On the 1stof July 2022, a new distribution grid tariff was introduced in Norway. This paper presents some of the analyses and findings from the ForTa project – a point of collaboration between grid operators, industry- and research partners – particularly analyses prior to the introduction of the new tariff, surveys of customer behavior and perception related to the new tariff, and analyses of metered demand data after the introduction of the new tariff. Findings suggest a trend of continued electrification which could lead to increased load peaks and grid challenges but also opportunities for management of such challenges. There are observed redistributional effects of the new tariff, although no clear evidence that the new grid tariff has contributed to household demand response.Experiences from the introduction of a hybrid energy and capacity-based distribution grid tariff in NorwayacceptedVersio
Changes in cement paste during accelerated mortar bar testing for pyrrhotite containing aggregate
Get PDFThe accelerated mortar bar test (AMBT) for pyrrhotite (Fe1-xS) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe1-xS oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe1-xS are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe1-xS, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observedpublishedVersio
Bioaccumulation of pharmaceuticals and stimulants in macrobenthic food web in the European Arctic as determined using stable isotope approach
Get PDFAlthough pharmaceuticals are increasingly detected in abiotic matrices in the Arctic, the accumulation of drugs in the resident biota and trophic transfer have not been yet examined. This study investigated the behaviour of several pharmaceuticals in the rocky-bottom, macrobenthic food web in the coastal zone of Isfjorden (western Spitsbergen) using stable isotope analyses (SIA) coupled with liquid chromatography-mass spectrometry (LC-MS/MS). Across 16 macroalgal and invertebrate species the highest average concentration was measured for ciprofloxacin (CIP) (on average 60.3 ng g−1 dw) followed by paracetamol (PCT) (51.3 ng g−1 dw) and nicotine (NIC) (37.8 ng g−1 dw). The biomagnification potential was assessed for six target compounds of 13 analytes detected that were quantified with a frequency > 50 % in biological samples. The trophic magnification factor (TMF) ranged between 0.3 and 2.8, and was significant for NIC and CIP. TMF < 1.0 for NIC (0.3; confidence interval, CI 0.1–0.5) indicated that the compound does not accumulate with trophic position. The dilution of pharmaceutical residues in the food web may result from limited intake with dietary route, poor assimilation efficiency and high biotransformation rates in benthic invertebrates. TMF for CIP (2.8, CI 1.2–6.4) suggests trophic magnification, a phenomenon observed previously for several antibiotics in freshwater food webs. Trophic transfer therefore plays a role in controlling concentration of CIP in the Arctic benthic communities and should be considered in environmental risk assessment. Biomagnification potential of diclofenac (DIC; 0.9, CI 0.5–1.7), carbamazepine (CBZ; 0.4, CI 0.1–2.1), caffeine (CAF; 0.9, CI 0.5–1.9) and PCT (1.3, CI 0.7–2.7) was not evident due to large 95 % confidence of their TMFs. This study provides the first evidence of drug bioaccumulation in the Arctic food web and indicates that behaviour of pharmaceuticals varies among target compounds.publishedVersio
A Lagrangian Model-Based Analysis of Protist Plankton Variability and Its Impact on Organic Matter Dynamics Along Transit Pathways Through the Fram Strait
Get PDFThe Arctic Ocean is characterized by substantial seasonal and inter-annual variability, of which the sources and impacts are not yet fully understood. Here, we analyze how much of the variability found in in situ observations of biogeochemical and ecological variables collected at the Long-Term Ecological Research Observatory HAUSGARTEN can be explained by differences in the physical conditions in the water masses passing through the Fram Strait (FS). Employing a size-based plankton ecosystem model with nine distinct size classes of protist phyto- and zooplankton, we simulate standing stocks and fluxes within the nutrient, phytoplankton, zooplankton, and detritus pools in water parcels that follow trajectories tracing the opposing East-Greenland and West-Spitsbergen currents through the FS. Our model results agree with in situ observations of biogeochemical tracers, plankton size measurements, climatological data, and remote sensing observations. They show distinct temporal developments in plankton size composition, growth, and export in trajectory ensembles, highlighting how variable physical conditions affect the communities' specific growth histories. Our study indicates that 10%–72% of the variability in upper water column tracer concentrations observed in the FS can be attributed to differences in water parcel trajectories. The maxima of net primary production and vertical export along the trajectories occurred in some (spatial and temporal) distance upstream of the sites of in situ sampling. This study shows that Lagrangian modeling helps clarify complex biogeochemical-ecological relationships in highly dynamic systems such as the FS, which is urgently needed to understand the role of climate change in the Arctic carbon cycle.publishedVersio