RISE – Research Institutes of Sweden
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Development of large lab-scale fire dynamics experiment relevant for Scandinavian wildfire conditions (TREEADS)
No full textWildfires in Scandinavia are predicted to become more frequent and severe [1,2], necessitating a deeper understanding of the fire behaviour in scenarios unique to local conditions. Therefore, the Norwegian Pilot in the EU-funded wildfire project TREEADS focuses on understanding fire dynamics and fire spread mechanisms inherent for Norwegian wildfires and develop a relevant and scalable lab test method to document the fire resilience of materials against wildfires.TREEADS has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036926.</p
Rapid aerodynamic method for predicting the performance of interacting wing sails
No full textRapid performance prediction tools are required for the evaluation, optimization, and comparison of different wind propulsion systems (WPSs). These tools should capture viscous aerodynamic flow effects in 3D, particularly the maximum propulsion force, stall angles, and interaction effects between the lift-generating units. This paper presents a rapid aerodynamic calculation method for wing sails that combines a semi-empirical lifting line model with a potential flow-based interaction model to account for 3D interaction effects. The method was applied to a WPS that consisted of several wing sails with considerable interaction effects. The results were compared to CFD RANS simulations in 2D and in 3D. For the evaluated validation cases, the interaction model improved the prediction considerably compared to when the interaction was not accounted for. The method provided acceptable driving force, moments, and stall predictions, with negligible computational cost compared to 3D CFD simulations. This research was funded by the Swedish Energy Agency , grant number 2022/P2021-00275 . The 3D CFD simulations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) and the Swedish National Infrastructure for Computing (SNIC) at the Chalmers Centre for Computational Science and Engineering (C3SE), High Performance Computing Center North (HPC2N) and Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) partially funded by the Swedish Research Council through grant agreements no. 2022-06725 and 2018-05973</p
Randomized study of two different consent procedures on recall : a study within a digital alcohol intervention trial
No full textIntroduction: Individuals’ comprehension of the information provided in consent forms should fundamentally influence whether to participate initially in a study and later whether to remain a participant. Existing evidence, however, suggests that participants do not thoroughly read, comprehend, or recall the information in consent forms. This study aimed to better understand how well participants recalled trial procedure information in the consent materials they received prior to taking part in a trial of a digital alcohol intervention. Method: This study was nested within an online effectiveness trial. The study included a contrast between two layout approaches to present the trial procedure information: one where all materials were shown on the same page (One page) and one where participants had to click on links to get materials for certain parts of the study information (Active request). Recall of trial procedures was measured 2 months post-randomization with four questions. Participants were also asked to leave a comment after each question. Result: Of the 2437 individuals who registered interest in the parent trial, 1197 were randomized to One page and 1240 were randomized to Active request. Approximately 90% consented to participate and 53% of the participants responded to the recall questionnaire. Contrasting the consent layout showed no marked differences between groups in three out of the four questions on recall of trial procedures. There was, however, evidence that recall of aspects of how personal data would be handled during the trial did differ between the two groups, with the Active request group reporting less recall than the One page group. Free-text comments were used to give nuance to the quantitative analysis. Conclusion: Participants exposed to different layouts of trial procedure information exhibited varying levels of information recall 2 months after consenting. The findings highlight the influence of the presentation of consent forms, which should be given attention when designing trials. Trial registration: ISRCTN ISRCTN48317451. Registered 6 December 2018, https://www.isrctn.com/ISRCTN48317451. This study was conducted under the auspices of the Alcohol Research Council of the Swedish Alcohol Retailing Monopoly (grant numbers 2019-0056 and 2020-0043) and the Swedish Research Council for Health, Working Life, and Welfare (grant number 2022-00193)</p
In-vitro method and model to estimate methane emissions from liquid manure management on pig and dairy farms in four countries
No full textMethane (CH4) emissions from manure management on livestock farms are a key source of greenhouse gas emissions in some regions and for some production systems, and the opportunities for mitigation may be significant if emissions can be adequately documented. We investigated a method for estimating CH4 emissions from liquid manure (slurry) that is based on anaerobic incubation of slurry collected from commercial farms. Methane production rates were used to derive a parameter of the Arrhenius temperature response function, lnA', representing the CH4 production potential of the slurry at the time of sampling. Results were used for parameterization of an empirical model to estimate annual emissions with daily time steps, where CH4 emissions from individual sources (barns, outside storage tanks) can be calculated separately. A monitoring program was conducted in four countries, i.e., Denmark, Sweden, Germany and the Netherlands, during a 12-month period where slurry was sampled to represent barn and outside storage on finishing pig and dairy farms. Across the four countries, lnA' was higher in pig slurry compared to cattle slurry (p < 0.01), and higher in slurry from barns compared to outside storage (p < 0.01). In a separate evaluation of the incubation method, in-vitro CH4 production rates were comparable with in-situ emissions. The results indicate that lnA' in barns increases with slurry age, probably due to growth or adaptation of the methanogenic microbial community. Using lnA' values determined experimentally, empirical models with daily time steps were constructed for finishing pig and dairy farms and used for scenario analyses. Annual emissions from pig slurry were predicted to be 2.5 times higher than those from cattle slurry. Changing the frequency of slurry export from the barn on the model pig farm from 40 to 7 d intervals reduced total annual CH4 emissions by 46 %; this effect would be much less on cattle farms with natural ventilation. In a scenario with cattle slurry, the empirical model was compared with the current IPCC methodology. The seasonal dynamics were less pronounced, and annual CH4 emissions were lower than with the current methodology, which calls for further investigations. Country-specific models for individual animal categories and point sources could be a tool for assessing CH4 emissions and mitigation potentials at farm level. The project was funded under the 2018 Joint Call of the ERA-NETs FACCE ERA- GAS , SusAn and ICT-AGRI on “Novel technologies, solutions and systems to reduce greenhouse gas emissions in animal production systems”. The Danish contributions to this project were supported by the Ministry of Food, Agriculture and Fisheries through the Green Development and Demonstration Program (contract No. 34009-19-1491). In the Netherlands, the project was supported by the Dutch Research Council ( NWO ) and co-funded by the Ministry of Agriculture, Nature and Food Quality . The Swedish governmental research council Formas supported the Swedish part of the study. In Germany, the project was supported by the German Federal Ministry of Food and Agriculture ( BMEL ) through the Office for Agriculture and Food ( BLE ), Grant No. 2819ERA07A (“M4Models”).</p
Roadmap towards the redefinition of the second
No full textThis paper outlines the roadmap towards the redefinition of the second, which was recently updated by the CCTF Task Force created by the CCTF in 2020. The main achievements of optical frequency standards (OFS) call for reflection on the redefinition of the second, but open new challenges related to the performance of the OFS, their contribution to time scales and UTC, the possibility of their comparison, and the knowledge of the Earth’s gravitational potential to ensure a robust and accurate capacity to realize a new definition at the level of 10−18 uncertainty. The mandatory criteria to be achieved before redefinition have been defined and their current fulfilment level is estimated showing the fields that still needed improvement. The possibility to base the redefinition on a single or on a set of transitions has also been evaluated. The roadmap indicates the steps to be followed in the next years to be ready for a sound and successful redefinition
Characterization of airborne dust emissions from three types of crushed multi-walled carbon nanotube-enhanced concretes
No full textDispersing Multi-Walled Carbon Nanotubes (MWCNTs) into concrete at low (<1 wt% in cement) concentrations may improve concrete performance and properties and provide enhanced functionalities. When MWCNT-enhanced concrete is fragmented during remodelling or demolition, the stiff, fibrous and carcinogenic MWCNTs will, however, also be part of the respirable particulate matter released in the process. Consequently, systematic aerosolizing of crushed MWCNT-enhanced concretes in a controlled environment and measuring the properties of this aerosol can give valuable insights into the characteristics of the emissions such as concentrations, size range and morphology. These properties impact to which extent the emissions can be inhaled as well as where they are expected to deposit in the lung, which is critical to assess whether these materials might constitute a future health risk for construction and demolition workers. In this work, the impact from MWCNTs on aerosol characteristics was assessed for samples of three concrete types with various amounts of MWCNT, using a novel methodology based on the continuous drop method. MWCNT-enhanced concretes were crushed, aerosolized and the emitted particles were characterized with online and offline techniques. For light-weight porous concrete, the addition of MWCNT significantly reduced the respirable mass fraction (RESP) and particle number concentrations (PNC) across all size ranges (7 nm – 20 μm), indicating that MWCNTs dampened the fragmentation process by possibly reinforcing the microstructure of brittle concrete. For normal concrete, the opposite could be seen, where MWCNTs resulted in drastic increases in RESP and PNC, suggesting that the MWCNTs may be acting as defects in the concrete matrix, thus enhancing the fragmentation process. For the high strength concrete, the fragmentation decreased at the lowest MWCNT concentration, but increased again for the highest MWCNT concentration. All tested concrete types emitted <100 nm particles, regardless of CNT content. SEM imaging displayed CNTs protruding from concrete fragments, but no free fibres were detected. This study was supported by AFA Insurance ( dnr 20010 ); the European Union's Horizon 2020 research and innovation programme LightCoce (grant agreement No 814632 ); and the Swedish Foundation for Strategic Environmental Research through the research program Mistra Environmental Nanosafety Phase II.</p
The Development of Automatic Sprinkler System Concepts for Maritime Vehicle Carriers
No full textClosed ro-ro spaces on maritime vehicle carriers are usually protected by a total-flooding carbon dioxide system. Such systems have many benefits, for example that there are no residues that can adversely affect the protected objects (in this case thousands of vehicles) and the agent is electrically non-conductive. However, there could be a considerable time delay from the start of a fire until the carbon dioxide system is discharged. Experience has shown that this delay time can cause significant fire damage and jeopardize the performance of the system. Within the EU funded LASH FIRE project, design and installation guidelines for supplementary automatic water-based fire sprinkler systems were developed. An important design feature is that the system automatically activates at an early stage of a fire. This would allow more time to fight the fire manually or to safely evacuate the space and discharge the CO2 system when the fire is controlled to one or a few vehicles instead of at a time when it has escalated in size. The work was partly based on a comprehensive literature review that identified relevant standards and information applicable to the design of automatic fire sprinkler and deluge water spray systems. Large-scale fire tests verified that the suggested system designs were able to provide control of realistic vehicle fires, including fires in passenger cars and a freight truck.Open access funding was provided by RISE Research Institutes of Sweden. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 814975.</p
Performance analysis of two generations of heaving point absorber WECs in farms of hexagon-shaped array layouts
No full textNumerical analyses are presented for two generations of a floating heaving point absorber wave energy converter (WEC) installed with different farm array layouts. The wave farm configurations are based on WECs developed by Waves4Power. The numerical models are developed in the DNV software package, Sesam. Parametric studies of the isolated WEC configurations and farm array layouts are conducted under typical environmental conditions and various incident wave directions to understand the hydrodynamic power performance and the levelised cost of energy (LCoE). Hexagonal layouts are proposed for deploying the WEC units and compared with a 10-unit layout termed StarBuoy, which has been reported in previous work. The results of the present study confirm that the interactions between arrayed units in a farm can have either positive or negative effects on the LCoE, which is dependent on the array layout and environmental conditions. The hexagonal array layouts lead to lower LCoE owing to constructive interaction effects. This work was performed within the project entitled ‘Control of wave energy converters based on wave measurements, for optimal energy absorption,’ funded by the Swedish Energy Agency through contract agreement no. 50197-1, and ‘INTERACT – Analysis of array systems of wave energy converters with regard to interaction effects in the LCoE and fatigue analyses,’ funded by the Swedish Energy Agency through contract agreement no. 50148-1. This study alsoreceived funding from the Chalmers University of Technology Foundation forthe strategic research project ‘Hydro- and aerodynamics’. </p
Dynamic out-of-plane compression of paperboard — Influence of impact velocity on the surface
No full textProcesses that convert paperboard into finished products include, for example, printing, where the paperboard is subjected to rapid Z-directional (ZD) compression in the print nip. However, measuring and evaluating the relevant properties in the thickness direction of paperboard are not necessarily straightforward or easy. Measuring at relevant, millisecond deformation rates further complicates the problem. The aim of the present work is to elucidate some of the influences on the compressive stiffness. Both the initial material response and the overall compressibility of the paperboard is studied. In this project, the effect on the material response from the surface structure and the millisecond timescale recovery is explored. The method utilized is a machine called the Rapid ZD-tester. The device drops a probe in freefall on the substrate and records the probe position, thus acquiring the deformation of the substrate. The probe is also allowed to bounce several times on the surface for consecutive impacts before being lifted for the next drop. To investigate the time dependent stiffness behavior, the probe is dropped several times at the same XY position on the paperboard from different heights, thus achieving different impact velocities. The material response from drops and bounces combined allows study of the short-term recovery of the material. The material in the study is commercial paperboard. The paperboard samples are compared to material where the surface has been smoothed by grinding it. Our study shows that there is a non-permanent reduction in thickness and a stiffening per bounce of the probe, indicating a compaction that has not recovered in the millisecond timescale. Additionally, a higher impact velocity has an initial stiffening effect on the paperboard, and this is reduced by smoothing the surface
Enhancing structural battery performance : Investigating the role of conductive carbon additives in LiFePO4-Impregnated carbon fiber electrodes
No full textThis study centers on investigating the influence of conductive additives, carbon black (Super P) and graphene, within the context of LiFePO4 (LFP)-impregnated carbon fibers (CFs) produced using the powder impregnation method. The performance of these additives was subject to an electrochemical evaluation. The findings reveal that there are no substantial disparities between the two additives at lower cycling rates, highlighting their adaptability in conventional energy storage scenarios. However, as cycling rates increase, graphene emerges as the better performer. At a rate of 1.5C in a half-cell versus lithium, electrodes containing graphene exhibited a discharge capacity of 83 mAhgLFP−1; those with Super P and without any additional conductive additive showed a capacity of 65 mAhgLFP−1 and 48 mAhgLFP−1, respectively. This distinction is attributed to the structural and conductivity advantages inherent to graphene, showing its potential to enhance the electrochemical performance of structural batteries. Furthermore, LFP-impregnated CFs were evaluated in full cells versus pristine CFs, yielding relatively similar results, though with a slightly improved outcome observed with the graphene additive. These results provide valuable insights into the role of conductive additives in structural batteries and their responsiveness to varying operational conditions, underlining the potential for versatile energy storage solutions. © 2024 The AuthorsThe authors also would like to thank the following sources for funding this research: VINNOVA (Sweden's Innovation Agency) through the Competence Centre BASE- Batteries Sweden, the Swedish Research Council [project number 2020\u201305057], Swedish Energy Agency [project number 50508\u20131], Air Force Office of Scientific Research [grant number FA8655-21-1-7039] and STandUP for Energy. </p