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Development of a Wake Model for Wind Farms Based on an Open Source CFD Solver

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Development of a Wake Model for Wind Farms Based on an Open Source CFD Solver Development of a wake model for wind farms based on an open source CFD solver. Strategies on parabolization and turbulence modeling PhD Thesis Daniel Cabezón Martínez Departamento de Ingeniería Energética y Fluidomecánica, Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid (UPM), Madrid, Spain Abstract Wake effect represents one of the most important aspects to be analyzed at the engineering phase of every wind farm since it supposes an important power deficit and an increase of turbulence levels with the consequent decrease of the lifetime. It depends on the wind farm design, wind turbine type and the atmospheric conditions prevailing at the site. Traditionally industry has used analytical models, quick and robust, which allow carry out at the preliminary stages wind farm engineering in a flexible way. However, new models based on Computational Fluid Dynamics (CFD) are needed. These models must increase the accuracy of the output variables avoiding at the same time an increase in the computational time. Among them, the elliptic models based on the actuator disk technique have reached an extended use during the last years. These models present three important problems in case of being used by default for the solution of large wind farms: the estimation of the reference wind speed upstream of each rotor disk, turbulence modeling and computational time. In order to minimize the consequence of these problems, this PhD Thesis proposes solutions implemented under the open source CFD solver OpenFOAM and adapted for each type of site: a correction on the reference wind speed for the general elliptic models, the semi-parabollic model for large offshore wind farms and the hybrid model for wind farms in complex terrain. All the models are validated in terms of power ratios by means of experimental data derived from real operating wind farms. i Acknowledgements First of all, I would like to thank sincerely to Professor Antonio Crespo and Emilio Migoya for their kind support and their nice advices along the last years during my regular visits to the laboratory. It has been a tremendous pleasure to work together and I hope we can continue doing so during the next years on the countless areas in wind energy that still remain open. Also thanks indeed to Kurt Hansen (DTU, Denmark) and Gerard Schepers (ECN, The Netherlands), two of my closest colleagues at the UPWIND project, for their unforgettable support during those 5 years and for sharing their experience to get accurate data bases to validate all the wake models that we analyzed. This project represented one my most satisfying and delighting personal and professional experiences of my late career. I’d also like to show my gratitude to my big friend Jonathon Sumner (ETS, Canada) for his useful and productive advices on the use of OpenFOAM during his stay in Spain and also to Professor Christian Masson (ETS, Canada) for having given me the opportunity to collaborate with ETS during the last years. And lastly I’d like to say Thank You to my parents, my wife Laura and my little boy Mario for their patience and understanding especially during the last months. They have been my source of inspiration during all these years. This PhD Thesis is especially dedicated to them. ii Publications during the PhD period 2005 Cabezón, D., Iniesta, A., Ferrer E., et. al., "Comparing linear and non linear wind flow models". Proceedings of the EUROMECH Colloquium 464b: Wind Energy. 4-7 Oct 2005, Oldenburg (Germany). 2006 Cabezón, D., Iniesta, A., Ferrer E., et. al., "Comparing linear and non linear wind flow models". Proceedings of the European Wind Energy Conference EWEC 2006, 27 Feb-2 Mar 2006, Athens (Greece) Cabezón D., Ferrer E., "Modelling wake effects using two CFD techniques". Proceedings of the European Wind Energy Conference EWEC 2006, 27 Feb-2 Mar 2006, Athens (Greece) Cabezón D., Ferrer E., "Modelling wake effects using two CFD techniques". Workshop on Wake Modelling and Benchmarking of Models, 6-7 Sep 2006, Billund / Høvsøre (Denmark) 2007 Cabezón D., Sanz J., Van Beeck J., "Sensitivity analysis on turbulence models for the ABL in complex terrain", Proceedings of the European Wind Energy Conference EWEC 2007, 7-10 May 2007, Milan (Italy) Cabezón D., Martí I.,"A methodology for estimating wind farm production through CFD codes: description and validation", Proceedings of the European Wind Energy Conference EWEC 2007, 7-10 May 2007, Milan (Italy) Barthelmie R., Schepers G., Frandsen, S.T., Hansen, K., Politis, E., Cabezón D., et.al. “Flow and Wakes in complex terrain and offshore. Model development and verification in UPWIND”, Proceedings of the European Wind Energy Conference EWEC 2007, 7-10 May 2007, Milan (Italy) Barthelmie, R.J., Rathmann, O., Frandsen, S.T., Hansen, K., Politis, E., Prospathopoulos, J., Rados, K., Cabezon, D., Schlez, W., Phillips, J., Neubert, A., Schepers, J.G. and van der Piljl, S., Rados 2007: Modelling and measurements of wakes in large offshore wind farms, Conference on the science of making torque from wind, Danish Technical University, August 2007. 8 pp. Journal of Physics Conference Series, Vol. 75, 012049. 2008 Sanz Rodrigo J., Cabezón D., Martí I., Patilla P., van Beeck J., “Numerical CFD modelling of non-neutral atmospheric boundary layers for offshore wind resource assessment based on Monin-Obukhov theory”, EWEC 2008 scientific proceedings, Brussels, Belgium, April 2008. Barthelmie, R.J., Frandsen, S.T., Rathmann, O., Politis, E., Prospathpoulos, J., Rados, K., Hansen K., Cabezón D., Schlez W., Phillips, J., Neubert, A., van der Pijl, S. and Schepers, G., “Flow and wakes in large wind farms in complex terrain and offshore”. European Wind Energy Conference, Brussels, March 2008 (Scientific track) iii Cabezón D., Sanz Rodrigo J., Martí I., Crespo A., Validation of a CFD wake model based on the actuator disk technique and the thrust coefficient. Preliminary results. Proceedings of the European Academy of Wind Energy (EAWE), Magdeburg (Germany), 1-2 Oct 2008 Barthelmie, R.J., Frandsen, S.T., Rathmann, O., Politis, E., Propspathpoulos, J., Rados, K., Hansen, K., Cabezón, D., Schlez, W., Phillips, J., Neubert, A., van der Pijl, S. and Schepers, G. 2008: Flow and wakes in large wind farms in complex terrain and offshore. American Wind Energy Association Conference, Houston, Texas, June 2008. Barthelmie, R.J. Politis, E., Prospathopoulos, J., Frandsen, S.T., Rathmann, O., Hansen, K., van der Pijl, S., Schepers, G., Rados, K., Cabezón, D., Schlez, W., Phillips, J., Neubert, A. 2008: Power losses due to wakes in large wind farms, World Renewable Energy Congress X, Glasgow, July 2008 2009 Cabezón D., Sanz J., Martí I., Crespo A., “CFD modelling of the interaction between the Surface Boundary Layer and rotor wake. Comparison of results obtained with different turbulence models and mesh strategies”, EWEC 2009 scientific proceedings, Marseille, France, March 2009 Sanz J., Cabezón D., Lozano S., Martí I., “Parameterization of the atmospheric boundary layer for offshore wind resource assessment with a limited length-scale k-ε model”, EWEC 2009 scientific proceedings, Marseille, France, March 2009 2010 Cabezón D., Hansen K., Barthelmie, R.J., “Analysis and validation of CFD wind farm models in complex terrain. Effects induced by topography and wind turbines”, EWEC 2010 scientific proceedings, Warsaw, Poland, April 2010 Sanz Rodrigo J., García B., Cabezón D., Lozano S., Martí I., “Downscaling mesoscale simulations with CFD for high resolution regional wind mapping”, EWEC 2010 technical track proceedings, Warsaw, Poland, April 2010 Prospathopoulos, J., Politis, E.P., Chaviaropoulos, P.K., Rados, Schepers, G.S. Cabezón D., Hansen, K.S. and Barthelmie, R.J. 2010: CFD modelling of wind farms in complex terrain. European Wind Energy Conference, Warsaw, April 2010, 9 pp. Cabezón D., Hansen, K. and Barthelmie, R.J 2010: Linearity analysis of wake effects induced by complex terrain and wind turbines through CFD wind farm models. Fifth European Conference on Computational Fluid Dynamics, ECCOMAS CFD 2010, Lisbon, June 2010 Prospathopoulos, J., Cabezón D., Politis, E.P., Chaviaropoulos, P.K., Rados, K.G., Schepers, G.S., Hansen, K.S. and Barthelmie, R.J. 2010: Simulation of wind farms in flat and complex terrain using CFD, The Science of Making Torque from Wind, Crete, June 2010. 12 pp Barthelmie, R.J., Frandsen, S.T., Hansen, K., Politis, E., Cabezón D., Schepers, J.G., Rados, K.and Schlez, W. 2010: Power losses due to wind turbine wakes in large wind farms offshore and in complex terrain. World Renewable Energy Congress, Abu Dhabi, September 2010. iv 2011 Cabezón D., Sumner J., García B., Sanz Rodrigo J., Masson C., “RANS simulations of wind flow at the Bolund experiment”, EWEC 2011 scientific proceedings, Brussels, Belgium, March 2011 Politis, E., Prospathopoulos, J., Cabezón D., Hansen, K.S., Chaviaropoulos P.K., Barthelmie, R.J., 2011, “Modelling wake effects in large wind farms in complex terrain: the problem, the methods and the issues”, Journal of Wind Energy, DOI 10.1002/we.481 Cabezón D., Migoya E., Crespo A., “Comparison of turbulence models for the computational fluid dynamics simulation of wind turbine wakes in the atmospheric boundary layer”, Journal of Wind Energy, DOI: 10.1002/we.516 2013 Cabezón D., Migoya E., Crespo A., “A semi-parabolized wake model for big offshore wind farms based on the open source CFD solver OpenFOAM”, Journal of Informatics and Mathematics, accepted for publication v Nomenclature Symbol Description A Axial
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