Vetle Kjær Risinggård

• Sparta, Manuel & Risinggård, Vetle Kjær (2024). A finite-element method model for a ferromanganese and silicomanganese pilot furnace. The Southern African Journal of Mining and Metallurgy. ISSN 2225-6253. 123(3), s. 85–92. doi: 10.17159/2411-9717/2737/2024.
• Halvorsen, Svenn Anton; Herland, Egil Vålandsmyr; Sparta, Manuel & Risinggård, Vetle Kjær (2023). Understanding Scale-Up of High-Current Electrodes. Metallurgical and Materials Transactions B. ISSN 1073-5615. 54, s. 1985–1997. doi: 10.1007/s11663-023-02811-7. Vis sammendrag

  A simple and generic model for the heat distribution in electrodes for primary metal production has been investigated. The equations have been analyzed focusing on understanding the scale-up of electrodes under both direct current (DC) and alternating current (AC) conditions. The analysis provides a theoretical foundation for Westly’s empirical scale-up rule. For graphite and small carbon electrodes, the current-carrying capacity is limited by the ohmic heating, which controls the lateral heat flux and the temperature at the electrode periphery. For these electrodes, the current capacity is higher for DC than for AC. For large carbon or Søderberg electrodes, the electrode current must be limited to avoid large thermal stresses and subsequent breakages, especially in connection with shutdowns or considerable current fluctuations. Thermally, the current capacity is then limited by the maximum temperature difference between the center and the periphery. For this case, AC electrodes can carry more current than DC.

• Halvorsen, Svenn Anton; Fromreide, Mads; Sparta, Manuel & Risinggård, Vetle Kjær (2022). Mathematical models for electromagnetic conditions in submerged arc furnaces. I Ehrhardt, Matthias J. & Günther, Michael (Red.), Progress in Industrial Mathematics at ECMI 2021. Springer Nature. ISSN 978-3-031-11817-3. s. 389–395. doi: 10.1007/978-3-031-11818-0_51. Vis sammendrag

  The competence project, “Electrical Conditions and their Process Interactions in High Temperature Metallurgical Reactors (ElMet)”, has involved close cooperation between NORCE Norwegian Research Centre, Norwegian University of Science and Technology (NTNU), the universities of Oxford and Santiago de Compostela, and the industrial companies Elkem and Eramet Norway. Various mathematical modelling has been applied to get improved insight into the inner conditions in submerged arc furnaces. Equation analysis, non-dimensionalized equations, toy models and other simplified models have been utilized to acquire sound fundamental insight. The paper describes some important results based on analysis and simple models.

• Risinggård, Vetle Kjær; Sparta, Manuel; Fromreide, Mads & Halvorsen, Svenn Anton (2022). Large Electrode Movements: Realistic Electrical Crater Models . Proceedings of the Silicon for the Chemical & Solar Industry XVI. doi: 10.2139/ssrn.4117701.
• Sparta, Manuel; Fromreide, Mads; Risinggård, Vetle Kjær & Halvorsen, Svenn Anton (2022). Electrical Conditions in Submerged Arc Furnaces: A Web-Based Simulator. Proceedings of the Silicon for the Chemical & Solar Industry XVI. doi: 10.2139/ssrn.4118651.
• Risinggård, Vetle Kjær; Sivertsen, Ove; Thisted, Ulrik & Midttømme, Kirsti (2022). Performance study and life-cycle cost analysis of a ground-source heat-pump system in a commercial building in Norway. Science and Technology for the Built Environment. ISSN 2374-4731. 0. doi: 10.1080/23744731.2022.2097819. Vis sammendrag

  High-performance systems are a prerequisite for profitable borehole thermal-energy storage. This paper presents performance measures for a system operating at a seasonal performance factor of 4.5 and evaluates the life-cycle costs of the actual and alternative system configurations. Compared to systems using dry cooling and electric or district heating the as-built system represents a profitable investment with internal rates of return of respectively 4.9% and 5.9% over a 50-year life cycle. Consequently, ambient-temperature borehole thermal-energy storage is economically competitive in North-European climates at current prices.

• Nordgård-Hansen, Ellen Marie; Kishor, Nand; Midttømme, Kirsti; Risinggård, Vetle Kjær & Kocbach, Jan (2021). Case study on optimal design and operation of detached house energy system: Solar, battery, and ground source heat pump. Applied Energy. ISSN 0306-2619. 308. doi: 10.1016/j.apenergy.2021.118370. Fulltekst i vitenarkiv Vis sammendrag

  Government policy impacts the level of sustainability for which houseowners design and operate their energy system. Consequently, there is a need to consider the sustainability level resulting from different policies, assuming optimal design and operation. The present work focuses on detached residential houses, where the energy system consists of photovoltaic systems for energy generation and batteries and optional ground-source heat pump systems for energy storage. A mixed-integer linear programming model is presented, which takes policies and other constraints into account when optimizing system size and operation. The results allow overall sustainability validation through parameters like self-sufficiency and self-sustainability, as well as a detailed drill-down of the optimal operation. From the analysis, two modes of ground-source heat pump usage are seen. With a feed-in tariff present, its main use is as an energy source, while without this tariff the optimal use is for seasonal energy storage. It is also found that ground-source heat pump systems contribute to increased sustainability, but they may not be economically beneficial for single-family homes having low or medium heating requirements. Demands for heating and cooling change with time and place, as do available area for photovoltaic energy generation and externally available energy sources. Therefore, a detailed analysis of the kind presented here is recommended before new energy policies are implemented. For each specific house or project, this kind of analysis will also be useful to evaluate the sensitivity of an energy system’s performance towards changing policies.

• Halvorsen, Svenn Anton; Sparta, Manuel; Risinggård, Vetle Kjær & Fromreide, Mads (2021). Electrical conditions in 3-phase submerged arc furnaces: learning from the ElMet project. Social Science Research Network (SSRN). ISSN 1556-5068. doi: 10.2139/ssrn.3926712.
• Fromreide, Mads; Halvorsen, Svenn Anton; Sparta, Manuel; Risinggård, Vetle Kjær; Salgado, Pilar & Gomez, Dolores [Vis alle 7 forfattere av denne artikkelen] (2021). Effects of alternating currents in the hearth of submerged arc furnaces. Social Science Research Network (SSRN). ISSN 1556-5068. doi: 10.2139/ssrn.3926716. Vis sammendrag

  It is well known that alternating currents (AC) differ significantly from direct currents (DC) in large electrodes for Submerged Arc Furnaces (SAFs). The skin effect concentrates AC to the periphery of each electrode, while the proximity effect causes higher current concentration towards the leading electrode. In a presentation at INFACON XV it was further shown that there is also a significant proximity effect between electrode currents and induced currents in the furnace steel shell. Here, we will focus on differences and similarities between AC and DC below the electrodes. In many processes the current runs primarily vertically in a coke bed from each electrode to a metal bath, where it distributes to the other electrodes. In such coke beds we find no significant difference between AC and DC. In the highly conductive metal, there will be horizontal currents and a significant AC skin effect. Horizontal currents will also be present in the materials above the metal, depending on the electrical conductivity in this region. A simple model shows that there is a strong proximity effect between such adjacent currents, “pushing” the currents upwards within the slag/coke bed region. A simple estimate, based on furnace dimensions and assumed conductivities, will show whether this effect is significant, in which case DC computations are inadequate to estimate the current paths. The same proximity effect will significantly enhance induced currents in an electrically conductive lining. Finally, since the underlying Maxwell’s equations are linear, the fundamental current paths in 3-phase AC SAFs can be studied by computing two independent single-phase cases for a given geometry and distribution of electrical conductivities. Any other current distribution will be a linear combination of these two solutions.

• Sparta, Manuel; Risinggård, Vetle Kjær; Einarsrud, Kristian Etienne & Halvorsen, Svenn Anton (2021). An Overall Furnace Model for the Silicomanganese Process. JOM. ISSN 1047-4838. 73, s. 2672–2681. doi: 10.1007/s11837-021-04791-y. Fulltekst i vitenarkiv Vis sammendrag

  An overall model for a pilot-scale silicomanganese furnace that simultaneously considers electrical and thermal conditions, process chemistry, and flow of solid and liquid substances.

• Ghanbari Birgani, Atousa; Risinggård, Vetle Kjær & Linder, Jacob (2021). Self-consistent solution for the magnetic exchange interaction mediated by a superconductor. Scientific Reports. ISSN 2045-2322. 11. doi: 10.1038/s41598-021-83620-3. Fulltekst i vitenarkiv
• Li, Yang; Amado, Mario; Hyart, Timo; Mazur, Grzegorz P; Risinggård, Vetle Kjær & Wagner, Thomas [Vis alle 11 forfattere av denne artikkelen] (2020). Transition between canted antiferromagnetic and spin-polarized ferromagnetic quantum Hall states in graphene on a ferrimagnetic insulator. Physical review B (PRB). ISSN 2469-9950. 101(24). doi: 10.1103/PhysRevB.101.241405. Fulltekst i vitenarkiv
• Risinggård, Vetle Kjær & Linder, Jacob (2019). Direct and inverse superspin Hall effect in two-dimensional systems: Electrical detection of spin supercurrents. Physical review B (PRB). ISSN 2469-9950. 99(17). doi: 10.1103/PhysRevB.99.174505. Fulltekst i vitenarkiv
• Johansen, Øyvind; Risinggård, Vetle Kjær; Sudbø, Asle; Linder, Jacob & Brataas, Arne (2019). Current Control of Magnetism in Two-Dimensional Fe3GeTe2. Physical Review Letters. ISSN 0031-9007. 122(21). doi: 10.1103/PhysRevLett.122.217203. Fulltekst i vitenarkiv Vis sammendrag

  The recent discovery of magnetism in two-dimensional van der Waals systems opens the door to discovering exciting physics. We investigate how a current can control the ferromagnetic properties of such materials. Using symmetry arguments, we identify a recently realized system in which the current-induced spin torque is particularly simple and powerful. In Fe3GeTe2, a single parameter determines the strength of the spin-orbit torque for a uniform magnetization. The spin-orbit torque acts as an effective out-of-equilibrium free energy. The contribution of the spin-orbit torque to the effective free energy introduces new in-plane magnetic anisotropies to the system. Therefore, we can tune the system from an easy-axis ferromagnet via an easy-plane ferromagnet to another easy-axis ferromagnet with increasing current density. This finding enables unprecedented control and provides the possibility to study the Berezinskii-Kosterlitz-Thouless phase transition in the 2D XY model and its associated critical exponents

• Risinggård, Vetle Kjær; Tveten, Erlend Grytli; Brataas, Arne & Linder, Jacob (2017). Equations of motion and frequency dependence of magnon-induced domain wall motion. Physical review B (PRB). ISSN 2469-9950. 96(17). doi: 10.1103/PhysRevB.96.174441. Fulltekst i vitenarkiv
• Linder, Jacob; Amundsen, Morten & Risinggård, Vetle Kjær (2017). Intrinsic superspin Hall current. Physical review B (PRB). ISSN 2469-9950. 96(9). doi: 10.1103/PhysRevB.96.094512.
• Risinggård, Vetle Kjær & Linder, Jacob (2017). Universal absence of Walker breakdown and linear current-velocity relation via spin-orbit torques in coupled and single domain wall motion. Physical review B (PRB). ISSN 2469-9950. 95(13). doi: 10.1103/PhysRevB.95.134423. Fulltekst i vitenarkiv
• Risinggård, Vetle Meland; Kulagina, Iryna & Linder, Jacob (2016). Electric field control of magnon-induced magnetization dynamics in multiferroics. Scientific Reports. ISSN 2045-2322. 6. doi: 10.1038/srep31800. Fulltekst i vitenarkiv
• Lesaint, Cedric Michel; Risinggård, Vetle Meland; Hestad, Øystein; Hvidsten, Sverre & Glomm, Wilhelm (2016). Self-healing composites for high voltage electrical insulation, Jicable'15 - 9th International Conference on Power Insulated Cables : proceedings. SEE. ISSN 978-2-912328-62-5. doi: 10.1109/eic.2014.6869384. Vis sammendrag

  A self-healing electrical insulation material for high voltage apparatuses has yet not been developed. Such a material would have been very attractive for electrical components installed in conditions were service failures cause time consuming and very expensive replacements. This paper reports results from electrical characterization of a candidate self-healing high voltage composite. The composite includes a bisphenol A epoxy resin filled with microcapsules with a monomer (healing agent).The results show e.g. that microcapsules rupture when reached by an electrical tree, likely preventing further tree propagation

• Lesaint, Cedric Michel; Risinggård, Vetle; Hølto, Jorunn; Sæternes, Hans Helmer; Hestad, Øystein Leif & Hvidsten, Sverre [Vis alle 7 forfattere av denne artikkelen] (2014). Self-healing high voltage electrical insulation materials, 2014 IEEE Electrical Insulation Conference - EIC. IEEE conference proceedings. ISSN 978-1-4799-2787-6. s. 241–244. doi: 10.1109/EIC.2014.6869384. Vis sammendrag

  Electrical treeing can be the precursor to catastrophic failure for electrical insulation materials and hence significantly shorten their service lifetime. Considering that damage inside the composites (thermoset insulation materials containing fillers) is difficult to detect and particularly to repair, the ability to self-heal as a direct response to electrical degradation is very attractive, especially in challenging environments. The approach presented in this paper for development of self-healing thermoset electrical insulation materials is derived from a technology developed by White et al. in 2001, intended to halt mechanical degradation of the material: Microcapsules filled with a monomer (healing agent) are added to the insulation materials (epoxy) prior to casting. When cracks propagate in the material the microcapsules will rupture, releasing liquid healing agent into the crack. The final step of the self-healing process is the polymerization of the monomer, which occurs upon contact with a catalyst also added to the epoxy resin. Electrical degradation by electrical treeing has many similarities with mechanical cracking of the material. For a system containing microcapsules, one or more of the branches of the electrical tree will likely break a capsule, filling the electrical tree with the liquid monomer. As the tree structure is interconnected, most of the tree structure is likely to be filled. This depends on the partial pressure and viscosity of the monomer and the surface tension of the hollow tubes, but also on the availability of monomer relative to the dimensions of the hollow tubes. The filling itself should extinguish critical discharges, making further growth less likely. Upon polymerization, further development of the electrical tree should halt, or at least be significantly delayed. A series of tests, where high voltage was applied to metal needles cast in epoxy to induce electrical tree growth, was conducted to study electrical degradation and breakdown of the thermoset insulation with and without microcapsules with monomer (healing agent). The experimental setup used provides the possibility of studying the inception and propagation of the phenomena using an optical microscope. This setup was used to study the interaction between the electrical tree and the micro-capsules in situ, and showed the direct attraction of the electrical trees towards the microcapsules.

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• Risinggård, Vetle Kjær (2023). Analysis of magnetic-field data.
• Cuthbert, Emma & Risinggård, Vetle Kjær (2023). Analysis of magnetic field data from Eramet Kvinesdal.
• Risinggård, Vetle Kjær (2023). A web-based simulator for understanding metallurgical furnaces.
• Thisted, Ulrik & Risinggård, Vetle Kjær (2023). Forsker til lunsj LCA.
• Thisted, Ulrik & Risinggård, Vetle Kjær (2023). Forsker til lunsj LCA.
• Risinggård, Vetle Kjær (2023). Bedre økonomi og bærekraft – hvorfor LCA (Life Cycle Analysis) er viktig for deg.
• Risinggård, Vetle Kjær (2023). Bedre økonomi og bærekraft – hvorfor LCA (Life Cycle Analysis) er viktig for deg.
• Risinggård, Vetle Kjær (2022). New electrical measurements on the secondary side.
• Risinggård, Vetle Kjær (2022). Magnetic saturation: Treatment in COMSOL models.
• Risinggård, Vetle Kjær; Sparta, Manuel; Fromreide, Mads & Halvorsen, Svenn Anton (2022). Large Electrode Movements: Realistic Electrical Crater Models.
• Sparta, Manuel; Fromreide, Mads; Risinggård, Vetle Kjær & Halvorsen, Svenn Anton (2022). Electrical Conditions in Submerged Arc Furnaces: A Web-Based Simulator.
• Midttømme, Kirsti; Nordgård-Hansen, Ellen Marie & Risinggård, Vetle Kjær (2022). Geothermal heat pumps in Norway .
• Risinggård, Vetle Kjær (2021). Livssyklusanalyse av bergvarmeannlegget ved Scandic Flesland.
• Clauß, John; Midttømme, Kirsti; Risinggård, Vetle Kjær & Hetland, Sverre (2021). Scandic Flesland Airport.
• Halvorsen, Svenn Anton; Sparta, Manuel; Risinggård, Vetle Kjær & Fromreide, Mads (2021). Electrical conditions in three-phase submerged-arc furnaces — Learning from the ElMet project.
• Fromreide, Mads; Halvorsen, Svenn Anton; Sparta, Manuel; Risinggård, Vetle Kjær; Gomez, Dolores & Salgado, Pilar [Vis alle 7 forfattere av denne artikkelen] (2021). Effects of alternating currents in the hearth of submerged-arc furnaces.
• Risinggård, Vetle Kjær (2018). Magnetic graphene.
• Risinggård, Vetle Kjær (2018). Intrinsic superspin Hall current.
• Risinggård, Vetle Kjær (2017). Universal absence of Walker breakdown for spin-orbit and spin-Hall-torque-driven domain walls.
• Risinggård, Vetle Kjær (2016). Electric field control of magnetization dynamics in multiferroics.
• Risinggård, Vetle Kjær (2023). Sidestrømmer i trevareindustrien. NORCE Norwegian Research Centre. ISSN 978-82-8408-308-7. Vis sammendrag

  Utnyttelsen av sidestrømmer blant medlemsbedriftene til Tre på Agder er kartlagt ved hjelp av en spørreundersøkelse. Materialrester og avkapp går i dag hovedsakelig til forbrenning. Kvalitet trekkes fram som en viktig grunn for den lave graden av materialgjenvinning. Flertallet av bedriftene vurderer at økt gjenbruk av sidestrømmer er aktuelt i framtiden. Tilgang på materiale, samt riktig pris og kvalitet er de viktigste faktorene for å realisere dette potensialet. Det er også et stort potensial for økt bruk av norske råvarer av videreforedlet tre dersom slike råvarer blir tilgjengelig.

• Risinggård, Vetle Kjær (2022). Treavfall på Agder. NORCE Norwegian Research Centre. ISSN 978-82-8408-309-4. Vis sammendrag

  Mengden treavfall på Agder er kartlagt basert på Statistisk sentralbyrås sektorinndeling. Denne består av husholdningene, byggeaktivitet, industrien og de tjenesteytende næringene. Det er tildels store usikkerheter i tallene. I det innsamlede datagrunnlaget er det husholdningene som står for den største mengden treavfall. 40% av dette avfallet blir i dag materialgjenvunnet. Byggeaktivitet (unntatt næringsbygg), industri og tjenesteytende næringer bidrar med omtrent like mye treavfall. Det meste av avfallet fra byggeaktivitet kommer fra nybygg og riving av små boliger. På grunn av begrensninger i metodikken er det vanskelig å si hvilke næringer som står for det største bidraget innen sektoren tjenesteytende næringer. I industrien er produksjonen av treavfall konsentrert i trelast-, trevare- og møbelindustrien, som står for 54% av treavfallet i sektoren.

• Risinggård, Vetle Kjær & Nordgård-Hansen, Ellen Marie (2020). Utnyttelse av spillvarme i Lista Renewable Energy Park. NORCE Norwegian Research Centre. Vis sammendrag

  I denne rapporten er det sett på utradisjonelle bruksområder for spillvarme fra en battericellefabrikk med temperatur fra 35–40 °C og opp mot 80 °C. Mellomlagring av spillvarme for utjevning av variasjoner i produksjon eller forbruk kan gjøres i industriell skala og bør vurderes. Direkte bruk av varmen til oppvarming eller tørking kan også gjøres med gode virkningsgrader. Spesielt nevnes tørking av tømmer for trekullproduksjon som en relevant anvendelse. Videre er kjøling og renseprosesser spennende områder. Vannrensing kan være aktuelt for landbasert oppdrett eller akvaponi. Absorpsjonskjøling kan blant annet være aktuelt for bruk i et datasenter. Det anbefales også en grundig gjennomgang av mulighetene for å redusere mengden spillvarme ved best mulig varmeintegrasjon internt i battericellefabrikken.

• Risinggård, Vetle Kjær (2019). Spin currents and torques via magnons, electrons, and Cooper pairs. NTNU. ISSN 978-82-326-4044-7. 2019(224).

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