Special Issue "Wind Energy 2011"

Guest Editor
Prof. Dr. Simon J. Watson
Centre for Renewable Energy Systems Technology, Department of Electronic and Electrical Engineering, Holywell Park, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
Website: http://www.lboro.ac.uk/departments/el/people/Watson-Simon-Professor.html
E-Mail: s.j.watson@lboro.ac.uk
Phone: +44 1509 635348
Fax: +44 1509 635341
Interests: wind power; wind resource assessment; wind turbine wake modeling; climate change impacts on wind energy; integration of renewable energy into networks; wind turbine condition monitoring

Dear Colleagues,

This special issue entitled “Wind Energy 2011” will be devoted to new developments in the field of wind energy. Articles related to the state of the art for wind turbines, supporting technology and wind energy in general will be considered, however, articles are particularly encouraged in the areas listed below. Articles are sought which relate to novel wind turbine concepts particularly with regard to very large (>5MW) machines and supporting infrastructure. This includes areas such as novel concepts in the design of drive trains, generators, controllers, blades and grid connections. Wind turbine reliability and availability is an area of particular concern to the wind energy industry and articles which relate to novel concepts in wind turbine health monitoring, fault detection and wind turbine reliability are encouraged. The use of numerical models in the design, siting and operation of wind turbines is increasing with advances in computing technology. Articles which deal with use of such models in areas such as advanced wind turbine control, loading, aeroelastics, aeroacoustics, wake modelling, wind resource assessment, wind power forecasting and general turbine design would be of significant interest. Accurate measurement of the wind is critical to wind farm planning. The use of advanced measurement techniques such as LIDAR and SODAR has attracted much attention recently. Articles which deal with the application of more advanced wind measurement methods including remote sensing is encouraged. The impact of climate change on regional wind resources is far from certain. Articles which deal with the use of historical and model predicted data to infer potential changes in regional wind climates would be of particular interest.

Simon J. Watson
Guest Editor

Submission

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• wind energy
• wind turbine
• wind resource
• wind turbine design
• condition monitoring
• reliability
• measurement and methods
• numerical modelling
• climate change

Type of Paper: Article
Title: Modeling the Influence of the Wind Characteristics and the Atmospheric Stability on the Wind Turbine Performances
Authors: Radian Belu ^1,2 and Darko Koracin ¹
Affiliation: ¹ Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA;  E-Mail: Darko.Koracin@DRI.edu
² Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA; E-Mail: rb544@drexel.edu
Abstract: The uncertainty of power performance measurements is closely related to the uncertainty of the wind velocity and other meteorological parameters and their effects on the wind turbine performances.  For example, there is an inherent uncertainty in the method of measuring the power curve is by using the wind speed measured at the hub height.  The assumption behind this is that these wind speeds are representative of the wind over the whole rotor area.  While this assumption was adequate for smaller wind turbines, this is essentially not true for modern multi-MW ones.  As a consequence, considerable deviations often occur between the expected and produced power.  Wind shear, direction changes, turbulence and atmospheric stability vary with height as a result of either meteorological and/or terrain conditions.  This calls for an adoption of new measurement and power estimation methods.  The size of the rotor combined with the turbine hub height implies that wind turbines are often exposed to highly varying wind conditions with large wind shear, turbulence and atmospheric stability variations and direction shear within the rotor span.  These parameters will affect both the production as well as the structural safety of the turbine. Consequently, better predictions of power or loads require a more representative set of wind measurements and power computations over the turbine’s rotor.
The impacts of atmospheric stability, turbulence and wind shear on the wind turbine output power and site evaluation are reviewed.  Velocity, temperature, and turbulence intensity are generated using a model developed from Monin-Obukov similarity theory and turbulence equation derived from the k-ε turbulence model to resolve the atmospheric parameters, such as the friction velocity, the Monin-Obukov length, the temperature scale, and the roughness length.  The resulting system of nonlinear equations was solved numerically and tested against field observations.  The experimental data from sonic anemometers used in this study were collected during 14 months on an 80 m instrumented meteorological tower at four levels (10 m, 40 m, 60 m, and 80 m).  The rotor averaged wind speed is then evaluated by numerically integrating the resulting velocity profile over the swept area of the rotor.  Power output estimates were compared with data found in literature and the available manufacturer data for multi-MW wind turbines.