SINTEF Open
Not a member yet
11374 research outputs found
Sort by
Environmentally Acceptable Lubricants for Stern Tube Application: Shear Stability and Friction Factor
Get PDFStern tube lubricants are essential in maritime operations, safeguarding ship propeller shafts from wear and corrosion while ensuring efficient propulsion. Their role in reducing friction and maintaining system integrity is critical. With growing environmental concerns, the adoption of environmentally acceptable lubricants (EALs) for stern tubes has gained importance, balancing operational performance with environmental protection. This study investigates the rheological and tribological properties of EALs formulated for ship propeller stern tube applications. The primary focus is on comparing these EALs with conventional mineral oils to assess their suitability in marine environments. EALs are increasingly favored due to their biodegradability and reduced environmental impact. Key parameters such as shear stability, friction factor, and temperature dependency were evaluated using a range of experimental methods including rotational viscometry and tribological analysis. The results indicate that the newly formulated EALs based on synthetic esters exhibit the highest viscosity index, a higher range of shear stability, and lower friction factors, compared to commercially available mineral oils, especially under varying operational conditions. These findings contribute to the ongoing efforts to promote eco-friendly lubricants in maritime industries, aligning with global environmental protection initiatives.publishedVersio
An Adaptive Special Protection Scheme Coordinating Multiple Generation Units for Damping Power System Natural Oscillations
Get PDFThis paper presents a special protection scheme (SPS) that mitigates natural oscillations in the power system by enabling selected adaptive power oscillation damping (APOD) controllers in wind farms or synchronous generators. The SPS activation is triggered by an online power oscillation detection algorithm. Furthermore, to tackle the intricacies of time delays within the control system, an adaptive time delay compensator (ATDC) has been integrated into the SPS control scheme. The SPS is tested on the New England 39 bus system by numerical simulations and in the Nordic 44 system by experimental testing with a hardware-in-the-loop approach. The numerical results show that the proposed SPS can increase the damping of lowfrequency natural oscillations (LFOs) significantly and even avoid unstable situations with growing oscillations. Moreover, the laboratory validation demonstrates that the system is able to run in real-time and that the time delays caused by PMU measurements, communication, and computation can be handled correctly. Thus, the proposed SPS concept can possibly be implemented to serve as an additional and automatic tool for the system operators to damp natural power oscillations by coordinated control of multiple sourcesAn Adaptive Special Protection Scheme Coordinating Multiple Generation Units for Damping Power System Natural OscillationsacceptedVersio
Low-Cost Sensor Technologies for Underwater Vehicle Navigation in Aquaculture Net Pens
Get PDFThis work presents a setup comprised of an underwater vehicle and various sensors that can be used for underwater navigation. The complete system is tested in an aquaculture fish farm, which features an environment that includes fish, deforming and flexible structures and highly variable environmental disturbances. The proposed approach integrates and provides software-based time-synchronization of data from external and on-board sensors to enable development and testing of multi-modal underwater navigation methods. All system components are low-cost, small-size and available of-the-shelf, motivated by the desire to collectively develop suitable underwater navigation methods that may be used in complex environments such as aquaculture fish farms, large tanks and underwater caves. Data captured through field trials in a fish farm show the potential of the proposed integrated system and the challenges related to underwater navigation in a complex underwater environment.publishedVersio
ERG-AI: enhancing occupational ergonomics with uncertainty-aware ML and LLM feedback
Get PDFWorkers, especially those involved in jobs requiring extended standing or repetitive movements, often face significant health challenges due to Musculoskeletal Disorders (MSDs). To mitigate MSD risks, enhancing workplace ergonomics is vital, which includes forecasting long-term employee postures, educating workers about related occupational health risks, and offering relevant recommendations. However, research gaps remain, such as the lack of a sustainable AI/ML pipeline that combines sensor-based, uncertainty-aware posture prediction with large language models for natural language communication of occupational health risks and recommendations. We introduce ERG-AI, a machine learning pipeline designed to predict extended worker postures using data from multiple wearable sensors. Alongside providing posture prediction and uncertainty estimates, ERG-AI also provides personalized health risk assessments and recommendations by generating prompts based on its performance and prompting Large Language Model (LLM) APIs, like GPT-4, to obtain user-friendly output. We used the Digital Worker Goldicare dataset to assess ERG-AI, which includes data from 114 home care workers who wore five tri-axial accelerometers in various bodily positions for a cumulative 2913 hours. The evaluation focused on the quality of posture prediction under uncertainty, energy consumption and carbon footprint of ERG-AI and the effectiveness of personalized recommendations rendered in easy-to-understand language.publishedVersio
CALiSol-23: Experimental electrolyte conductivity data for various Li-salts and solvent combinations
Get PDFIon transport in non-aqueous electrolytes is crucial for high performance lithium-ion battery (LIB) development. The design of superior electrolytes requires extensive experimentation across the compositional space. To support data driven accelerated electrolyte discovery efforts, we curated and analyzed a large dataset covering a wide range of experimentally recorded ionic conductivities for various combinations of lithium salts, solvents, concentrations, and temperatures. The dataset is named as ’Conductivity Atlas for Lithium salts and Solvents’ (CALiSol-23). Comprehensive datasets are lacking but are critical to building chemistry agnostic machine learning models for conductivity as well as data driven electrolyte optimization tasks. CALiSol-23 was derived from an exhaustive review of literature concerning experimental non-aqueous electrolyte conductivity measurement. The final dataset consists of 13,825 individual data points from 27 different experimental articles, in total covering 38 solvents, a broad temperature range, and 14 lithium salts. CALiSol-23 can help expedite machine learning model development that can help in understanding the complexities of ion transport and streamlining the optimization of non-aqueous electrolyte mixtures.publishedVersio
Environmental impacts of carbon capture, transport, and storage supply chains: Status and the way forward
Get PDFpublishedVersio
Balancing the Norwegian regulated power market anno 2016 to 2022
Get PDFThe balancing market for power is designed to account for the difference between predicted supply/demand of electricity and the realised supply/demand. However, increased electrification of society changes the consumption patterns, and increased production from renewable sources leads to larger un-predicted fluctuations in production, both effects potentially leading to increased balancing. We analyse public market data for the balancing market (manual Frequency Restoration Reserve) for Norway from 2016 to 2022 to investigate and document these effects. The data is newer than for similar analyses and the eight years of data is more than double the time span previously covered. The main findings are: (a) The balancing volumes are dominated by hours of zero regulation but for non-zero hours, the balancing volumes are increasing during the eight-year period. (b) The balancing prices are primarily correlated with day-ahead prices and secondary with balancing volumes. The latter correlation is found to be increasingly non-linear with time. (c) The balancing volumes and the price difference between balancing price and day-ahead price are strongly correlated with the previous hour. (d) The increasing share of wind power has not impacted the frequency of balancing, which has remained stable during the 8 years studied. However, the volumes and share of balancing power compared to overall production have increased, suggesting that the hours which are inherently difficult to predict remain the same. (e) Market data alone cannot predict balancing volumes. If attempting, the auto-correlation becomes the main source of information.publishedVersio
Renewable Energy Complementarity (RECom) maps - a comprehensive visualisation tool to support spatial diversification
Get PDFMaps showing the mean wind speed only give an inaccurate indication of the quality of locations for future wind power developments. Calculating the capacity factor and plotting that on a map gives a better indication of the expected mean power output, but the outcome depends on the turbine choice. In this article, we introduce a general step-by-step method for improved visualisation of potential wind power locations. First, the mentioned dependency on turbine choice is compensated for by putting the expected mean power output in relation to the expected mean power output of all other wind parks of the region. This relative capacity factor results in comprehensive wind resource maps and can be plotted for the situation today and also for a future scenario. Since the expected income of a potential wind park is the product of mean power output and mean market value, looking at the relative capacity factor only does not give the full picture. The mean market value is influenced by the merit order effect that is mainly driven by covariance with other wind parks and the capacity factor's relation to production at low-wind moments. A market value factor is introduced that captures the expected mean market value relative to other wind parks, based on a simplified power market model. Finally the Renewable Energy Complementarity (RECom) index is defined, combining the relative capacity factor and market value factor into a single index, resulting in RECom maps. This map can comprehensively show the revenue potential of different locations for potential future wind power developments. © Author(s) 2024.Renewable Energy Complementarity (RECom) maps - a comprehensive visualisation tool to support spatial diversificationpublishedVersio
Intra-arm Balancing Control for Modular Multilevel Converter with Cell Loading Operated under High Power Imbalances
Get PDFMultiport converters with a large number of ports have been explored for integrated generation units or batteries. An attractive candidate multiport converter has been developed based on the modular multilevel converter (MMC) with cell loading. Accordingly, this study proposes a control strategy for a multiport converter based on the MMC operated under high power imbalances among cells. Owing to this power imbalance, the multiport converter requires an additional circulating current (intra-arm balancing current) to provide balanced three-phase grid currents and balanced capacitor voltages in all cells. In a previous study, the minimum required intra-arm balancing current was calculated offline and applied according to the loading condition. This method may require a high-capacity memory for the controller. In contract, this study proposes an active control method for minimizing the intra-arm balancing current online. Experimental results reveal that the multiport converter achieves balanced three-phase currents with a total harmonic distortion of 3.13% and balanced capacitor voltages with an error of 0.1% under maximum power imbalance among cells. © 2024 The Institute of Electrical Engineers of Japan.Intra-arm Balancing Control for Modular Multilevel Converter with Cell Loading Operated under High Power ImbalancesacceptedVersio