Installing offshore wind farm can be challenging. Horizontal-axis wind turbines (HAWTs) have maintenance difficulty due to the location of its rotor and drive-train which are to be installed at the top of very tall towers. To improve the use of wind turbine, vertical-axis wind turbines (VAWTs) were introduced which overcame the disadvantages of HAWTs by locating their main components at the base of the wind turbine and made both installation and maintenance easier. It is possible to further improve the performance of wind turbine by optimizing the blades of the wind turbine. Wind turbine blades are made of composite materials due to their high strength-to-weight ratio and good fatigue performance. Additionally, wind turbine blades generally have complex structural layout including one or more shear webs and a number of composite plies placed at different ply angles, making their structural design quite challenging.
Dr. Lin Wang and colleagues from Cranfield University in the UK combined finite element analysis (FEA) and genetic algorithm (GA) to develop a structural optimization model of wind turbine composite blades. The research work is now published in peer-reviewed journal, Composite Structures.
The research team categorized the structural models used for wind turbine blades into two groups, that is one dimensional (1D) beam model and three dimensional (3D) FEA model. Due to the complexity of wind turbine blades structural layout, the team suggested combining FEA and GA to develop a structural optimization model of wind turbine composite blades. They applied the structural optimization model to ELECTRA 30 kW wind turbine blade, which is a novel VAWT blade, to optimize the structural layout of the blades. The optimization model took into consideration stress constraint, deformation constraint, vibration constraint, buckling constraint, and manufacturing maneuverability and continuity of laminate layups constraint.
The optimal blade design leads to a mass reduction of 17.4% in comparison with the initial design, the maximum total deformation is about 0.593 m and observed at the tip of the upper sail. The deformation value obtained is 15.3% lower than the allowable value of 0.7 m, the shows the new blade design is quite stiff and is not likely to experience large deformations. The team pointed out that the blade will not suffer from buckling, due to its load multiplier being 2.15 that is 43.33% higher than the minimum allowable value of 1.5. From the stress distribution, the research team observed the maximum positive normal stress to be 151.72 MPa, which is 52.90% lower when compared with the allowable value of 322.1 MPa. And the maximum negative normal stress (i.e. maximum compressive stress) to be very close to the allowable value.
This study demonstrated that the structural optimization model presented is capable of improving the efficiency of blade structural optimization and effectively and accurately determining the optimal structural layups of composite blades.
Lin Wang1, Athanasios Kolios1, Takafumi Nishino1, Pierre-Luc Delafin, Theodore Bird2, Structural optimization of vertical-axis wind turbine composite blades based on finite element analysis and genetic algorithm, Composite Structures 153 (2016) 123–138.Show Affiliations
- Centre for Offshore Renewable Energy Engineering, School of Energy, Environment and Agrifood, Cranfield University, Cranfield MK43 0AL, UK.
- Aerogenerator Project Limited, Ballingdon Mill, Sudbury CO10 7EZ, UK.
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