A Flexible Folding Morphing Blades Wind Turbine Inspired by the Borneo Camphor Seed


Student thesis: Doctoral Thesis

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Awarding Institution
Award date8 Aug 2023


The flexibility and sheet-like properties of the wings of the Borneo camphor seed inspired a new flexible folding morphing blades wind turbine design. The flat and flexible blades are proposed to be made of plastic sheet material with high elastic limit and strain tolerance. Strip heaters, which are expected to be cheaper than injection molding or casting, are recommended to bend plastic sheets into blades. This flexible turbine design was proposed to exhibit all-round abilities that may be absent in conventional rigid blades wind turbines such as the ability to utilize large blade bending deformation to improve torque, fast wind tracking ability, and fast self-start. This study is significant as it introduces a new alternative, low-cost, flexible wind turbine blade design, which is expected to be competitive against the existing conventional rigid blades wind turbines. The objectives of this study include solving the science challenges, engineering challenges and cost and performance metrics of the propose flexible folding morphing blades wind turbine design inspired by the Borneo camphor seed with the consideration of performances and manufacturing cost. Parametric manipulation was proposed to deduce the performances of various configured flexible folding morphing blades wind turbine by using the computational fluid dynamics simulation. The performance of the proposed wind turbine design can be determined by comparative study against existing conventional wind turbine design. The fluid-structure interaction model was adopted to investigate the proposed wind turbine blades aeroelastic behavior under wind load. Wind tunnel and field tests were adopted to measure the performance of the proposed wind turbine blade designs. The scope of this study includes the investigation of mechanical, material and fluid dynamics, the investigation of fluid-structure interaction and the investigation of the cost and performance metrics of the proposed flexible folding morphing blades wind turbine. The limitation of this study is governed by the size of the wind tunnel as well as the computational power available. Thus, the proposed wind turbine sizes were to be confined to a small scale of wind turbines less than 1.5 m in diameter.

The investigation of the behavior and performance of a novel flexible-bladed wind turbine was discussed. The performance of the flexible-bladed wind turbine was compared with that of a rigid-bladed wind turbine on four main aspects: electrical power output, start-up, blade coning, and yawing. The results showed that the flexible-bladed wind turbine had a higher power, faster start-up, flexible blade coning and faster yaw. A proposal of oblique folding mechanism design inspired by the wings of Borneo camphor seeds to enable the blades of wind turbines to pitch and cone was discussed. Numerical predictions of the power and self-start performance of a downwind folding-blade horizontal axis wind turbine were conducted. For comparison, a benchmark wind turbine with a constant chord blade section with an SD8000 airfoil and zero blade twist was also modeled. This finding confirms that a folding blade can increase the power output, start-up capability and passive yaw capability of a wind turbine. The study which utilized computational fluid dynamics and the response surface methodology to investigate the performance of the proposed double-fold blade horizontal axis wind turbine was discussed. The performance of the blades is controlled by the two folds, which are characterized by the root fold-axis angle, the tip fold-axis angle, the root fold angle, and the tip fold angle. The results indicated that the double-fold design outperforms the single-fold one. The investigation on the effect of four parameters which include the fold angle, blade thickness, taper ratio, and solidity on the performance of the flat plate two-fold blade wind turbine was discussed. Computational fluid dynamics was used to simulate the cases of two-fold blade wind turbine models. The response surface methodology was adopted to analyze the main effect and interaction effect among the four parameters. The analysis shows that the single factor coefficient has dominant effect over the interaction terms for response variables of power coefficient, starting torque and thrust coefficient. The implementation of 3D scanned Borneo camphor wings geometry into the wind turbine blade design was discussed. In phase one, five different geometries of Borneo camphor seed wings were modelled separately as wind turbine blades under different fold axis and fold angles configurations. The best wing geometry was chosen as the reference for phase two, which involved designing its flat-plates blades counterparts with single or multiple fold numbers. The phase two results showed that the peak power coefficients of two-fold configuration is comparable with that of the four-fold configuration, thus can be a practical choice as a cheap and powerful wind turbine design since lowering the fold numbers will result in cheap fabrication cost. The investigation of the aeroelastic properties and performance comparison of bioinspired single-folded and double-folded flat-plate flexible blades wind turbine by using a two-way partitioned approach fluid-structure interaction model was discussed. The extra tip fold of the double-folded blades caused it to exhibit significant difference in aeroelastic properties and performances when compared with the single-folded blades. The fluid-structure interaction simulation results show that the double-folded blades are suitable for quick self-start, fast rotational speeds, and high-power output applications while the single-folded blades are suitable for high torque and low-cost applications. The field test that was conducted to observe the behavior and the performances of a proposed low-cost recyclable folded flat-plate blades wind turbine design inspired by the Borneo camphor seed wings was discussed. Four configurations of the blades were tested in the open field of Shek Kip Mei Service Reservoir Playground, Hong Kong. The results demonstrated the advantages of using the proposed folded flat-plate blades wind turbine design include cost-efficiency, a wide range of customizations, portable and space efficiency, quick and easy fabrication, easy maintenance, fool-proof, and recyclable.