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Ivanell, Stefan
Publications (10 of 41) Show all publications
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
Simisiroglou, N., Polatidis, H. & Ivanell, S. (2019). Wind Farm Power Production Assessment: Introduction of a New Actuator Disc Method and Comparison with Existing Models in the Context of a Case Study. Applied Sciences, 9(3), Article ID 431.
Open this publication in new window or tab >>Wind Farm Power Production Assessment: Introduction of a New Actuator Disc Method and Comparison with Existing Models in the Context of a Case Study
2019 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 3, article id 431Article in journal (Refereed) Published
Abstract [en]

The aim of the present study is to perform a comparative analysis of two actuator disc methods (ACD) and two analytical wake models for wind farm power production assessment. To do so, wind turbine power production data from the Lillgrund offshore wind farm in Sweden is used. The measured power production for individual wind turbines is compared with results from simulations, done in the WindSim software, using two ACD methods (ACD (2008) and ACD (2016)) and two analytical wake models widely used within the wind industry (Jensen and Larsen wake models). It was found that the ACD (2016) method and the Larsen model outperform the other method and model in most cases. Furthermore, results from the ACD (2016) method show a clear improvement in the estimated power production in comparison to the ACD (2008) method. The Jensen method seems to overestimate the power deficit for all cases. The ACD (2016) method, despite its simplicity, can capture the power production within the given error margin although it tends to underestimate the power deficit.

Keywords
wind resource assessment, wakes, wind farm layout, actuator disc, computational fluid dynamics
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-379947 (URN)10.3390/app9030431 (DOI)000459976200071 ()
Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-03-25Bibliographically 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
Ivanell, S., Arnqvist, J., Avila, M., Cavar, D., Aurelio Chavez-Arroyo, R., Olivares-Espinosa, H., . . . Witha, B. (2018). Micro-scale model comparison (benchmark) at the moderately complex forested site Ryningsnäs. Wind Energy Science, 3(2), 929-946
Open this publication in new window or tab >>Micro-scale model comparison (benchmark) at the moderately complex forested site Ryningsnäs
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2018 (English)In: Wind Energy Science, ISSN 2213-3968, E-ISSN 2366-7443, Vol. 3, no 2, p. 929-946Article in journal (Refereed) Published
Abstract [en]

This article describes a study in which modellers were challenged to compute the wind field at a forested site with moderately complex topography. The task was to model the wind field in stationary conditions with neutral stratification by using the wind velocity measured at 100 m at a metmast as the only reference. Detailed maps of terrain elevation and forest densities were provided as the only inputs, derived from airborne laser scans (ALSs) with a resolution of 10 m x 10 m covering an area of 50 km x 50 km, that closely match the actual forest and elevation of the site. The participants were free to apply their best practices for the simulation to decide the size of the domain, the value of the geostrophic wind, and every other modelling parameter. The comparison of the results with the measurements is shown for the vertical profiles of wind speed, shear, wind direction, and turbulent kinetic energy. The ALS-based data resulted in reasonable agreement of the wind profile and turbulence magnitude. The best performance was found to be that of large-eddy simulations using a very large domain. For the Reynolds-averaged Navier-Stokes type of models, the constants in the turbulence closure were shown to have a great influence on the yielded turbulence level, but were of much less importance for the wind speed profile. Of the variety of closure constants used by the participating modellers, the closure constants from Sogachev and Panferov (2006) proved to agree best with the measurements. Particularly the use of C-mu approximate to 0.03 in the k-epsilon model obtained better agreement with turbulence level measurements. All except two participating models used the full detailed ground and forest information to model the forest, which is considered significant progress compared to previous conventional approaches. Overall, the article gives an overview of how well different types of models are able to capture the flow physics at a moderately complex forested site.

National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-373232 (URN)10.5194/wes-3-929-2018 (DOI)000453927300001 ()
Funder
Swedish National Infrastructure for Computing (SNIC), SNIC 2017/11-10
Available from: 2019-01-14 Created: 2019-01-14 Last updated: 2019-01-14Bibliographically approved
Simisiroglou, N., Polatidis, H. & Ivanell, S. (2018). Wind farm power production assessment: a comparative analysis of two actuator disc methods and two analytical wake models. Wind Energy Science, 2018, 1-13
Open this publication in new window or tab >>Wind farm power production assessment: a comparative analysis of two actuator disc methods and two analytical wake models
2018 (English)In: Wind Energy Science, ISSN 2213-3968, E-ISSN 2366-7443, Vol. 2018, p. 1-13Article in journal (Refereed) Epub ahead of print
Abstract [en]

The aim of the present study is to perform a comparative analysis of two actuator disc methods (ACD) and two analytical wake models for wind farm power production assessment. To do so wind turbine power production data from the Lillgrund offshore wind farm in Sweden is used. The measured power production for individual wind turbines is compared with results from simulations, done in the WindSim software, using two ACD methods (old and new) and two analytical wake models widely used within the wind industry (Jensen and Larsen wake models). It was found that the new ACD method and the Larsen model outperform the other method and model in most cases. Furthermore, results from the new ACD method show a clear improvement in the estimated power production in comparison to the old ACD method. The Jensen method seems to overestimate the power deficit for all cases. The new ACD method, despite it's simplicity, is capable of capturing the power production within the given error margin although it tends to underestimate the power deficit.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-350026 (URN)10.5194/wes-2018-8 (DOI)
Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-05-07Bibliographically approved
Breton, S.-P., Sumner, J., Sörensen, J. N., Hansen, K. S., Sarmast, S. & Ivanell, S. (2017). A survey of modelling methods for high-fidelity wind farm simulations using large eddy simulation. Philosophical Transactions. Series A: Mathematical, physical, and engineering science, 375(2091), Article ID 20160097.
Open this publication in new window or tab >>A survey of modelling methods for high-fidelity wind farm simulations using large eddy simulation
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2017 (English)In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, no 2091, article id 20160097Article, review/survey (Refereed) Published
Abstract [en]

Large eddy simulations (LES) of wind farms have the capability to provide valuable and detailed information about the dynamics of wind turbine wakes. For this reason, their use within the wind energy research community is on the rise, spurring the development of new models and methods. This review surveys the most common schemes available to model the rotor, atmospheric conditions and terrain effects within current state-of-the-art LES codes, of which an overview is provided. A summary of the experimental research data available for validation of LES codes within the context of single and multiple wake situations is also supplied. Some typical results for wind turbine and wind farm flows are presented to illustrate best practices for carrying out high-fidelity LES of wind farms under various atmospheric and terrain conditions. This article is part of the themed issue 'Wind energy in complex terrains'.

Place, publisher, year, edition, pages
ROYAL SOC, 2017
Keywords
large eddy simulation, wind turbine wakes, wind farm wakes, rotor modelling, atmospheric modelling, complex terrain
National Category
Environmental Engineering
Identifiers
urn:nbn:se:uu:diva-321549 (URN)10.1098/rsta.2016.0097 (DOI)000397879700002 ()
Funder
Swedish Energy Agency
Available from: 2017-05-11 Created: 2017-05-11 Last updated: 2017-05-11Bibliographically approved
Mann, J., Angelou, N., Arnqvist, J., Callies, D., Cantero, E., Arroyo, R. C., . . . Rodrigues, C. V. (2017). Complex terrain experiments in the New European Wind Atlas. Philosophical Transactions. Series A: Mathematical, physical, and engineering science, 375(2091), 1-23, Article ID 20160101.
Open this publication in new window or tab >>Complex terrain experiments in the New European Wind Atlas
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2017 (English)In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, no 2091, p. 1-23, article id 20160101Article in journal (Refereed) Published
Abstract [en]

The New European Wind Atlas project will create a freely accessible wind atlas covering Europe and Turkey, develop the model chain to create the atlas and perform a series of experiments on flow in many different kinds of complex terrain to validate the models. This paper describes the experiments of which some are nearly completed while others are in the planning stage. All experiments focus on the flow properties that are relevant for wind turbines, so the main focus is the mean flow and the turbulence at heights between 40 and 300 m. Also extreme winds, wind shear and veer, and diurnal and seasonal variations of the wind are of interest. Common to all the experiments is the use of Doppler lidar systems to supplement and in some cases replace completely meteorological towers. Many of the lidars will be equipped with scan heads that will allow for arbitrary scan patterns by several synchronized systems. Two pilot experiments, one in Portugal and one in Germany, show the value of using multiple synchronized, scanning lidar, both in terms of the accuracy of the measurements and the atmospheric physical processes that can be studied. The experimental data will be used for validation of atmospheric flow models and will by the end of the project be freely available. This article is part of the themed issue 'Wind energy in complex terrains'.

Keywords
complex terrain, meteorological experiment, Doppler lidar
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-321181 (URN)10.1098/rsta.2016.0101 (DOI)000397879700006 ()
Funder
Swedish Energy Agency
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2017-05-12
Kleusberg, E., Mikkelsen, R. F., Schlatter, P., Ivanell, S. & Henningson, D. S. (2017). High-Order Numerical Simulations of Wind Turbine Wakes. In: WAKE CONFERENCE 2017: . Paper presented at Wake Conference, MAY 30-JUN 01, 2017, Uppsala Univ Gotland Campus, Visby, SWEDEN. IOP PUBLISHING LTD, Article ID 012025.
Open this publication in new window or tab >>High-Order Numerical Simulations of Wind Turbine Wakes
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2017 (English)In: WAKE CONFERENCE 2017, IOP PUBLISHING LTD , 2017, article id 012025Conference paper, Published paper (Refereed)
Abstract [en]

Previous attempts to describe the structure of wind turbine wakes and their mutual interaction were mostly limited to large-eddy and Reynolds-averaged Navier Stokes simulations using finite volume solvers. We employ the higher-order spectral-element code Nek5000 to study the influence of numerical aspects on the prediction of the wind turbine wake structure and the wake interaction between two turbines. The spectral-element method enables an accurate representation of the vortical structures, with lower numerical dissipation than the more commonly used finite-volume codes. The wind-turbine blades are modeled as body forces using the actuator-line method (ACL) in the incompressible Navier Stokes equations. Both tower and nacelle are represented with appropriate body forces. An inflow boundary condition is used which emulates homogeneous isotropic turbulence of wind-tunnel flows. We validate the implementation with results from experimental campaigns undertaken at the Norwegian University of Science and Technology (NTNU Blind Tests), investigate parametric influences and compare computational aspects with existing numerical simulations. In general the results show good agreement between the experiments and the numerical simulations both for a single turbine setup as well as a two-turbine setup where the turbines are offset in the spanwise direction. A shift in the wake center caused by the tower wake is detected similar to experiments. The additional velocity deficit caused by the tower agrees well with the experimental data. The wake is captured well by Nek5000 in comparison with experiments both for the single wind turbine and in the two-turbine setup. The blade loading however shows large discrepancies for the high-turbulence, two-turbine case. While the experiments predicted higher thrust for the downstream turbine than for the upstream turbine, the opposite case was observed in Nek5000.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Series
Journal of Physics Conference Series, ISSN 1742-6588, E-ISSN 1742-6596 ; 854
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-365892 (URN)10.1088/1742-6596/854/1/012025 (DOI)000435276400025 ()
Conference
Wake Conference, MAY 30-JUN 01, 2017, Uppsala Univ Gotland Campus, Visby, SWEDEN
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-11-19Bibliographically approved
Eriksson, O., Baltscheffsky, M., Breton, S.-P., Söderberg, S. & Ivanell, S. (2017). The Long distance wake behind Horns Rev I studied using large eddy simulations and a wind turbine parameterization in WRF. Paper presented at Wake Conference 2017, 30 May to 1 June 2017, Visby, Sweden. Journal of Physics, Conference Series, 854, Article ID 012012.
Open this publication in new window or tab >>The Long distance wake behind Horns Rev I studied using large eddy simulations and a wind turbine parameterization in WRF
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2017 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 854, article id 012012Article in journal (Refereed) Published
Abstract [en]

The aim of the present paper is to obtain a better understanding of long distance wakes generated by wind farms as a first step towards a better understanding of farm to farm interaction. The Horns Rev I (HR) wind farm is considered for this purpose, where comparisons are performed between microscale Large Eddy Simulations (LES) using an Actuator Disc model (ACD), mesoscale simulations in the Weather Research and Forecasting Model (WRF) using a wind turbine parameterization, production data as well as wind measurements in the wind farm wake. The LES is manually set up according to the wind conditions obtained from the mesoscale simulation as a first step towards a meso/microscale coupling.

The LES using an ACD are performed in the EllipSys3D code. A forced boundary layer (FBL) approach is used to introduce the desired wind shear and the atmospheric turbulence field from the Mann model. The WRF uses a wind turbine parameterization based on momentum sink. To make comparisons with the LESs and the site data possible an idealized setup of WRF is used in this study.

The case studied here considers a westerly wind direction sector (at hub height) of 270 ± 2.5 degrees and a wind speed of 8 ± 0.5 m/s. For both the simulations and the site data a neutral atmosphere is considered. The simulation results for the relative production as well as the wind speed 2 km and 6 km downstream from the wind farm are compared to site data. Further comparisons between LES and WRF are also performed regarding the wake recovery and expansion.

The results are also compared to an earlier study of HR using LES as well as an earlier comparison of LES and WRF. Overall the results in this study show a better agreement between LES and WRF as well as better agreement between simulations and site data.

The procedure of using the profile from WRF as inlet to LES can be seen as a simplified coupling of the models that could be developed further to combine the methods for cases of farm to farm interaction.

National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-362564 (URN)10.1088/1742-6596/854/1/012012 (DOI)000435276400012 ()
Conference
Wake Conference 2017, 30 May to 1 June 2017, Visby, Sweden
Available from: 2018-10-07 Created: 2018-10-07 Last updated: 2019-03-18Bibliographically approved
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