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Nilsson, Karl
Publications (10 of 15) Show all publications
Sopher, D., Juhlin, C., Levendal, T., Erlstrom, M., Nilsson, K. & Da Silva Soares, J. P. (2019). Evaluation of the subsurface compressed air energy storage (CAES) potential on Gotland, Sweden. Environmental Earth Sciences, 78(6), Article ID 197.
Open this publication in new window or tab >>Evaluation of the subsurface compressed air energy storage (CAES) potential on Gotland, Sweden
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2019 (English)In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 78, no 6, article id 197Article in journal (Refereed) Published
Abstract [en]

Wind energy is an important field of development for the island of Gotland, Sweden, especially since the island has set targets to generate 100% of its energy from renewable sources by 2025. Due to the variability of wind conditions, energy storage will be an important technology to facilitate the continued development of wind energy on Gotland and ensure a stable and secure supply of electricity. In this study, the feasibility of utilizing the Middle Cambrian Faludden sandstone reservoir on Gotland for Compressed Air Energy Storage (CAES) is assessed. Firstly, a characterization of the sandstone beneath Gotland is presented, which includes detailed maps of reservoir thickness and top reservoir structure. Analysis of this information shows that the properties of the Faludden sandstone and associated cap rock appear favorable for the application of CAES. Seven structural closures are identified below the eastern and southern parts of Gotland, which could potentially be utilized for CAES. Scoping estimates of the energy storage capacity and flow rate for these closures within the Faludden sandstone show that industrial scale CAES could be possible on Gotland.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Faludden reservoir, OPAB data set, Gas storage, Baltic Basin, Baltic Sea, Wind power
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-380480 (URN)10.1007/s12665-019-8196-1 (DOI)000460829600006 ()
Funder
Swedish Research Council, 2010-3657
Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-04-15Bibliographically approved
Eriksson, O., Breton, S.-P., Nilsson, K. & Ivanell, S. (2019). Impact of Wind Veer and the Coriolis Force for an Idealized Farm to Farm Interaction Case. Applied Sciences, 9(5), Article ID 922.
Open this publication in new window or tab >>Impact of Wind Veer and the Coriolis Force for an Idealized Farm to Farm Interaction Case
2019 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 5, article id 922Article in journal (Refereed) Published
Abstract [en]

The impact of the Coriolis force on the long distance wake behind wind farms is investigated using Large Eddy Simulations (LES) combined with a Forced Boundary Layer (FBL) technique. When using the FBL technique any mean wind shear and turbulent fluctuations can be added with body forces. The wind shear can also include the mean wind veer due to the Coriolis force. The variation of the Coriolis force due to local deviations from the mean profile, e.g., from wakes, is not taken into account in the FBL. This can be corrected for with an extra source term in the equations, hereon defined as the Coriolis correction. For a row of 4 turbines it is shown that the inclusion of the wind veer turns the wake to the right, while including the Coriolis correction turns it to the left. When including both wind veer and Coriolis correction the impact of wind veer dominates. For an idealized farm to farm interaction case, two farms of 4 * 4 turbines with 6 km in between, it can be seen that when including wind veer and the Coriolis correction a approximately 3% increase in the relative production for a full wake direction can be seen and only a slightly smaller increase can be seen when including only wind veer. The results indicate that FBL can be used for studies of long distance wakes without including a Coriolis correction but efforts need to be taken to use a wind shear with a correct mean wind veer.

Keywords
long distance wake, farm to farm interaction, wind farm cluster, large Eddy simulations, LES, actuator disc, ACD, forced boundary layer, FBL, coriolis, wind veer
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-379116 (URN)10.3390/app9050922 (DOI)000462504400109 ()
Funder
Swedish National Infrastructure for Computing (SNIC)
Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-04-25Bibliographically approved
Olivares-Espinosa, H., Breton, S.-P., Nilsson, K., Masson, C., Dufresne, L. & Ivanell, S. (2018). Assessment of Turbulence Modelling in the Wake of an Actuator Disk with a Decaying Turbulence Inflow. Applied Sciences, 8(9), Article ID 1530.
Open this publication in new window or tab >>Assessment of Turbulence Modelling in the Wake of an Actuator Disk with a Decaying Turbulence Inflow
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2018 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 8, no 9, article id 1530Article in journal (Refereed) Published
Abstract [en]

The characteristics of the turbulence field in the wake produced by a wind turbine model are studied. To this aim, a methodology is developed and applied to replicate wake measurements obtained in a decaying homogeneous turbulence inflow produced by a wind tunnel. In this method, a synthetic turbulence field is generated to be employed as an inflow of Large-Eddy Simulations performed to model the flow development of the decaying turbulence as well as the wake flow behind an actuator disk. The implementation is carried out on the OpenFOAM platform, resembling a well-documented procedure used for wake flow simulations. The proposed methodology is validated by comparing with experimental results, for two levels of turbulence at inflow and disks with two different porosities. It is found that mean velocities and turbulent kinetic energy behind the disk are well estimated. The development of turbulence lengthscales behind the disk resembles what is observed in the free flow, predicting the ambient turbulence lengthscales to dominate across the wake, with little effect of shear from the wake envelope. However, observations of the power spectra confirm that shear yields a boost to the turbulence energy within the wake noticeable only in the low turbulence case. The results obtained show that the present implementation can successfully be used in the modelling and analysis of turbulence in wake flows.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
wind turbine wakes, turbulence, actuator disk, LES, wind tunnel, OpenFOAM
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-368765 (URN)10.3390/app8091530 (DOI)000445760200119 ()
Funder
Swedish Energy Agency
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2018-12-07Bibliographically approved
Nilsson, K., Soares, J. & Ivanell, S. (2018). Energy transition Gotland: Renewable resources and system effects.
Open this publication in new window or tab >>Energy transition Gotland: Renewable resources and system effects
2018 (English)Report (Other academic)
Publisher
p. 19
Keywords
Energy transition, Gotland, renewables, modeling, electrical system effects
National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-376672 (URN)
Note

Gotlands Energi AB (GEAB) is acknowledged for providing data of electricity production and consumption. Energimyndigheten is acknowledged for funding this study.

Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-02-08Bibliographically approved
Simisiroglou, N., Karatsioris, M., Nilsson, K., Breton, S.-P. & Ivanell, S. (2016). The actuator disc concept in PHOENICS. In: Tande, JOG; Kvamsdal, T; Muskulus, M (Ed.), Energy Procedia: . Paper presented at 13th Deep Sea Offshore Wind R&D Conference, EERA DeepWind’ JAN 20-22, 2016, Trondheim, Norway (pp. 269-277). , 94
Open this publication in new window or tab >>The actuator disc concept in PHOENICS
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2016 (English)In: Energy Procedia / [ed] Tande, JOG; Kvamsdal, T; Muskulus, M, 2016, Vol. 94, p. 269-277Conference paper, Published paper (Refereed)
Abstract [en]

This study presents two models to simulate a wind turbine. This is done by employing the 1D momentum actuator disc theory in PHOENICS, a general purpose computational fluid dynamics software. To test the general applicability of these models, single wind turbine simulations are conducted using eight different wind turbine models from two manufacturers. The simulations are performed by imposing sheared inflow with hub height wind speeds ranging from 3 m/s up to 25 m/s. A range of computational parameters are investigated, including the resolution of the domain, the thickness of the actuator disc and the iterative convergence criteria. To investigate the wake development produced by these methods, a comparison study is performed with the more complex large-eddy simulation software EllipSys3D using an actuator disc approach for validation purposes. The resulting wind turbine thrust and power outputs from PHOENICS are compared with the experimental power curves and thrust values provided by the manufacturers for each wind turbine. The results show that actuator disc methods are able to provide a reasonable estimation of the conventional wind turbine power and thrust output with low computational effort. Moreover, the results from the preliminary comparison of the wake produced from these two rotor models compare well with the wake produced by the actuator disc in EllipSys3D.

Series
Energy Procedia, ISSN 1876-6102 ; 94
Keywords
Wind energy, Computational Fluid Dynamics (CFD), Reynolds averaged Navier-Stokes (RANS), Actuator Disc (ACD), Large-eddy simulation (LES)
National Category
Earth and Related Environmental Sciences Environmental Engineering
Identifiers
urn:nbn:se:uu:diva-306640 (URN)10.1016/j.egypro.2016.09.182 (DOI)000387586600028 ()
Conference
13th Deep Sea Offshore Wind R&D Conference, EERA DeepWind’ JAN 20-22, 2016, Trondheim, Norway
Funder
StandUp for Wind
Available from: 2016-10-31 Created: 2016-10-31 Last updated: 2018-05-03Bibliographically approved
Nilsson, K., Ivanell, S., Mikkelsen, R., Hansen, K., Sørensen, J. N., Breton, S.-P. & Henningson, D. (2015). Large-eddy simulations of the Lillgrund wind farm. Wind Energy, 18(3), 449-467
Open this publication in new window or tab >>Large-eddy simulations of the Lillgrund wind farm
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2015 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 18, no 3, p. 449-467Article in journal (Refereed) Published
Abstract [en]

The power production of the Lillgrund wind farm is determined numerically using large-eddy simulations and compared with measurements. In order to simulate realistic atmospheric conditions, pre-generated turbulence and wind shear are imposed in the computational domain. The atmospheric conditions are determined from data extracted from a met mast, which was erected prior to the establishment of the farm. In order to allocate most of the computational power to the simulations of the wake flow, the turbines are modeled using an actuator disc method where the discs are imposed in the computational domain as body forces which for every time step are calculated from tabulated airfoil data. A study of the influence of imposed upstream ambient turbulence is performed and shows that higher levels of turbulence results in slightly increased total power production and that it is of great importance to include ambient turbulence in the simulations. By introducing ambient atmospheric turbulence, the simulations compare very well with measurements at the studied inflow angles. A final study aiming at increasing the farm production by curtailing the power output of the front row turbines and thus letting more kinetic energy pass downstream is performed. The results, however, show that manipulating only the front row turbines has no positive effect on the farm production, and therefore, more complex curtailment strategies are needed to be tested.

Keywords
large-eddy simulation, actuator disc, wind farms, power estimation, wakes
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-238263 (URN)10.1002/we.1707 (DOI)000348899700005 ()
Funder
Swedish National Infrastructure for Computing (SNIC)StandUp for Wind
Note

Article first published online: 18 FEB 2014

Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2017-12-05Bibliographically approved
Eriksson, O., Nilsson, K., Breton, S.-P. & Ivanell, S. (2015). Large-eddy simulations of wind farm production and long distance wakes. In: Wake Conference 2015: . Paper presented at Wake Conference, JUN 09-11, 2015, Visby, SWEDEN (pp. 012022). , Article ID 012022.
Open this publication in new window or tab >>Large-eddy simulations of wind farm production and long distance wakes
2015 (English)In: Wake Conference 2015, 2015, p. 012022-, article id 012022Conference paper, Published paper (Refereed)
Abstract [en]

The future development of offshore wind power will include many wind farms built in the same areas. It is known that wind farms produce long distance wakes, which means that we will see more occasions of farm to farm interaction, namely one wind farm operating in the wake of another wind farm. This study investigates how to perform accurate power predictions on large wind farms and how to assess the long distance wakes generated by these farms. The focus of this paper is the production's and wake's sensitivity to the extension of the grid as well as the turbulence when using Large-eddy simulations (LES) with pregenerated Mann turbulence. The aim is to determine an optimal grid which minimizes blockage effects and ensures constant resolution in the entire wake region at the lowest computational cost. The simulations are first performed in the absence of wind turbines in order to assess how the atmospheric turbulence and wind profile are evolving downstream (up to 12,000 m behind the position where the turbulence is imposed). In the second step, 10 turbines are added in the domain (using an actuator disc method) and their production is analyzed alongside the mean velocities in the domain. The blockage effects are tested using grids with different vertical extents. An equidistant region is used in order to ensure high resolution in the wake region. The importance of covering the entire wake structure inside the equidistant region is analyzed by decreasing the size of this region. In this step, the importance of the lateral size of the Mann turbulence box is also analyzed. In the results it can be seen that the flow is acceptably preserved through the empty domain if a larger turbulence box is used. The relative production is increased (due to blockage effects) for the last turbines using a smaller vertical domain, increased for a lower or narrower equidistant region (due to the smearing of the wake in the stretched area) and decreased when using a smaller turbulence box (due to decreased inmixing) The long distance wake behind the row is most impacted by the use of a smaller turbulence box, while the other simulation setups have less influence on these results. In summary, the results show the importance of having relatively large extensions of the domain, large extensions of the equidistant region and especially large extensions of the turbulence box.

Series
Journal of Physics Conference Series, ISSN 1742-6588 ; 625
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-261143 (URN)10.1088/1742-6596/625/1/012022 (DOI)000358047700022 ()
Conference
Wake Conference, JUN 09-11, 2015, Visby, SWEDEN
Funder
Swedish National Infrastructure for Computing (SNIC)StandUp for Wind
Available from: 2015-08-31 Created: 2015-08-31 Last updated: 2019-03-18Bibliographically approved
Nilsson, K., Shen, W. Z., Sorensen, J. N., Breton, S.-P. & Ivanell, S. (2015). Validation of the actuator line method using near wake measurements of the MEXICO rotor. Wind Energy, 18(3), 499-514
Open this publication in new window or tab >>Validation of the actuator line method using near wake measurements of the MEXICO rotor
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2015 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 18, no 3, p. 499-514Article in journal (Refereed) Published
Abstract [en]

The purpose of the present work is to validate the capability of the actuator line method to compute vortex structures in the near wake behind the MEXICO experimental wind turbine rotor. In the MEXICO project/MexNext Annex, particle image velocimetry measurements have made it possible to determine the exact position of each tip vortex core in a plane parallel to the flow direction. Determining center positions of the vortex cores makes it possible to determine the trajectory of the tip vortices, and thus the wake expansion in space, for the analyzed tip speed ratios. The corresponding cases, in terms of tip speed ratios, have been simulated by large-eddy simulations using a Navier-Stokes code combined with the actuator line method. The flow field is analyzed in terms of wake expansion, vortex core radius, circulation and axial and radial velocity distributions. Generally, the actuator line method generates significantly larger vortex cores than in the experimental cases, but predicts the expansion, the circulation and the velocity distributions with satisfying results. Additionally, the simulation and experimental data are used to test three different techniques to compute the average axial induction in the wake flow. These techniques are based on the helical pitch of the tip vortex structure, 1D momentum theory and wake expansion combined with mass conservation. The results from the different methods vary quite much, especially at high values of . Copyright (c) 2014 John Wiley & Sons, Ltd.

Keywords
MEXICO rotor, MexNext, CFD, ACL method, EllipSys3D
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-247478 (URN)10.1002/we.1714 (DOI)000348899700008 ()
Funder
StandUp for Wind
Available from: 2015-03-18 Created: 2015-03-18 Last updated: 2017-12-04Bibliographically approved
Nilsson, K., Breton, S.-P., Sørensen, J. N. & Ivanell, S. (2014). Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications. In: Science of Making Torque from Wind: . Paper presented at 5th Science of Making Torque from Wind Conference, JUN 18-20, 2014, Tech Univ Denmark, Copenhagen, DENMARK (pp. 012135).
Open this publication in new window or tab >>Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications
2014 (English)In: Science of Making Torque from Wind, 2014, p. 012135-Conference paper, Published paper (Refereed)
Abstract [en]

To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine how the mean characteristics of wake flow, mean power production and thrust depend on the choice of airfoil data and blade geometry. In order to simulate realistic conditions, pre-generated turbulence and wind shear are imposed in the computational domain. Using three different turbulence intensities and varying the spacing between the turbines, the flow around 4-8 aligned turbines is simulated. The analysis is based on normalized mean streamwise velocity, turbulence intensity, relative mean power production and thrust. From the computations it can be concluded that the actual airfoil characteristics and blade geometry only are of importance at very low inflow turbulence. At realistic turbulence conditions for an atmospheric boundary layer the specific blade characteristics play an minor role on power performance and the resulting wake characteristics. The results therefore give a hint that the choice of airfoil data in ACD simulations is not crucial if the intention of the simulations is to compute mean wake characteristics using a turbulent inflow.

Series
Journal of Physics Conference Series, ISSN 1742-6588 ; 524
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-241152 (URN)10.1088/1742-6596/524/1/012135 (DOI)000344193600135 ()
Conference
5th Science of Making Torque from Wind Conference, JUN 18-20, 2014, Tech Univ Denmark, Copenhagen, DENMARK
Funder
Swedish National Infrastructure for Computing (SNIC)StandUp for Wind
Available from: 2015-01-09 Created: 2015-01-08 Last updated: 2017-02-03Bibliographically approved
Eriksson, O., Nilsson, K., Breton, S.-P. & Ivanell, S. (2014). Analysis of long distance wakes behind a row of turbines – a parameter study. In: Science of Making Torque from Wind: . Paper presented at 5th Science of Making Torque from Wind Conference, JUN 18-20, 2014, Tech Univ Denmark, Copenhagen, DENMARK (pp. 012152).
Open this publication in new window or tab >>Analysis of long distance wakes behind a row of turbines – a parameter study
2014 (English)In: Science of Making Torque from Wind, 2014, p. 012152-Conference paper, Published paper (Refereed)
Abstract [en]

Large Eddy Simulations (LES) of the long distance wake behind a row of 10 turbines are conducted to predict wake recovery. The Navier-Stokes solver EllipSys3D is used in combination with the actuator disc concept. Neutral atmospheric conditions are assumed in combination with synthetic turbulence using the Mann method. Both the wind shear profile and turbulence are introduced into the flow field using body forces. Previous simulations using the same simulation method to model the Horns Rev wind farm showed a higher wake recovery at long distances compared to measurements. The current study investigates further the sensitivity to parameters such as the grid resolution, Reynolds number, the turbulence characteristics as well as the impact of using different internal turbine spacings. The clearest impact on the recovery behind the farm could be seen from the background turbulence. The impact of the wind shear on the turbulence level in the domain needs further studies. A lower turbulence level gives lower wake recovery as expected. A lower wake recovery can also be seen for a higher grid resolution. The Reynolds number, apart from when using a very low value, has a small impact on the result. The variation of the internal spacing is seen to have a relatively minor impact on the farm wake recovery.

Series
Journal of Physics Conference Series, ISSN 1742-6588 ; 524
National Category
Physical Sciences Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-237704 (URN)10.1088/1742-6596/524/1/012152 (DOI)000344193600152 ()
Conference
5th Science of Making Torque from Wind Conference, JUN 18-20, 2014, Tech Univ Denmark, Copenhagen, DENMARK
Funder
Swedish National Infrastructure for Computing (SNIC)StandUp for Wind
Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2019-03-18Bibliographically approved
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