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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Christian Engfer GE Renewable Energy, Spain
Co-authors:
Christian Engfer (1) F Marc Canal Vila (1)
(1) Alstom Wind, Barcelona, Spain

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Mr. Engfer is currently covering the position of the advanced aerodynamics engineer at AGE renewable Energy. He studied aerospace engineering at the University of Stuttgart and has a deep knowledge in aerodynamics and CFD (8 years of professional experience in aerodynamic design).


Poster

Poster Download poster (10.60 MB)

Abstract

Advanced method to optimize wind turbine blade design

Introduction

Nowadays, there are two persistent challenges in conceptual blade design for modern wind turbines: the first one is to find efficiently the geometry of the so-called master airfoils featuring not only a target aerodynamic performance but also being the best compromise between aerodynamics and structural requirements. The second one is then to design a blade geometry providing a maximum annual energy yield (AEY) while keeping loads and hence costs at a low level.

Approach

One way to face the first challenge is for instance to use class-shape-transformation (CST) method to define the airfoil geometry and to couple it with a rapid panel solver and a powerful optimizer capable of minimizing a multi-parameter cost function. In the approach to be presented very smooth airfoil geometries are obtained in terms of curvature by parameterizing the airfoil geometry using Bernstein (for airfoils having maximum thickness >> TE thickness) or Bezier (for flatback airfoils having a maximum thickness in the order magnitude of the TE thickness) polynomials.

Main body of abstract

In the following Bernstein coefficients or Bezier control points are optimized using evolutionary and generic algorithms to find the best compromise between the target performance (efficiency, stall margins and turbulence behavior under clean and rough conditions) and structural requirements (geometry limits, max. thickness, thickness skewness). Flatback airfoils are optimized to provide maximum in-plane forces while respecting structural requirements. During the optimization airfoil performance is evaluated automatically using an improved panel solver (RFoil) incorporating empirical correction factors susceptible to match panel solver results with wind tunnel data.
With the previously obtained master airfoils, the design for the optimum blade geometry is proposed as follows: in a first step the thickness, twist and chord distributions of the blade are defined by using B-splines. Then the control point coordinates of these distributions are varied in order to minimize a cost function considering target values for the power coefficient, optimum tip speed ratio, energy, tower loads and blade weight. In every iteration of the optimization loop, the power curve, loads and mass for different design load cases are evaluated automatically using the aero-elastic code Bladed.

Conclusion

Thanks to the presented approach, engineers are able to provide efficiently a very smooth blade design that is not only the optimum between performance, structural and manufacturing requirements but also satisfying market demands. At the same time, due to the high level of automatization, the method allows studies of parameter variations within a short period of time.


Learning objectives
The proposed method describes one way to design and optimize a 3D wind turbine blade requiring only an available airfoil database and an optimization environment.