Novel bio-inspired winglets for wind turbine blades

Abstract

A winglet system suitable for wind turbine blades wherein the winglets are structured to resemble bird wingtip feathers. The winglet system comprising protrusions that decrease in size from the leadin

Description

Field of Application This invention applies to the renewable energy sector, particularly wind energy, enhancing the aerodynamic performance of wind turbine blades. Background Wind turbines are a critical component of the global renewable energy infrastructure, playing a key role in the transition to a more sustainable energy future. However, wind turbines face several aerodynamic challenges that limit their efficiency and increase their operating costs. One of the most significant challenges is the formation of tip vortices, which are generated at the tips of turbine blades due to the pressure differences between the upper and lower surfaces of the blades. These vortices create drag, which reduces lift and leads to a decrease in the overall energy capture efficiency of the turbine. The problem of tip vortices is not unique to wind turbines; it is also encountered in aviation, where similar aerodynamic inefficiencies occur at the wingtips of aircraft. To mitigate this, various winglet designs have been developed and applied to airplanes to reduce drag and improve fuel efficiency. However, while these winglets have proven effective in aviation, they have not been fully optimized for the specific aerodynamic challenges posed by wind turbines, particularly in offshore environments where wind speeds are higher and the effects of tip vortices are more pronounced. The present invention seeks to address these limitations by introducing bio-inspired winglets that are specifically designed for wind turbine applications. These winglets draw inspiration from the wingtip feathers of birds, such as barn owls, which have evolved to minimize drag and optimize lift during flight. By mimicking the structure of these feathers, the winglets effectively disrupt vortex formation and reduce drag, leading to significant improvements in the aerodynamic performance of wind turbine blades. The bio-inspired design offers a novel and highly effective solution to the problem of tip vortices, making it a valuable addition to the wind energy sector. The introduction of bio-inspired designs in engineering has a long history of success, particularly in the field of aerodynamics. Nature, through millions of years of evolution, has perfected the art of flight, with birds such as barn owls exhibiting remarkable efficiency in controlling airflow and minimizing drag. By studying and replicating these natural mechanisms, engineers have been able to develop innovative solutions that address modem engineering challenges. The bio-inspired winglets presented in this invention are a prime example of how natural designs can be adapted to improve the performance of wind turbines, ultimately contributing to more efficient and sustainable energy production. Summary of the invention The invention provides a set of bio-inspired winglets designed to enhance the aerodynamic performance of wind turbine blades by reducing tip vortex formation. Tip vortices are a major source of energy loss in wind turbines, creating drag that reduces lift and decreases the overall efficiency of the turbine. By introducing winglets that mimic the cascading structure of barn owl feathers, the invention effectively mitigates vortex formation, leading to significant improvements in both lift and drag characteristics. The bio-inspired winglets offer several key advantages over traditional winglet designs. Firstly, the winglets improve the lift-to-drag ratio by 28%, as demonstrated through rigorous wind tunnel testing and CFD simulations. This improvement translates into a 5-7% increase in the annual energy output of wind turbines, depending on the specific wind conditions and turbine size. Secondly, the winglets reduce vortex strength by 44%, which directly contributes to a reduction in drag and an increase in energy conversion efficiency. Finally, the winglets are designed to be retrofittable, allowing them to be easily installed on existing turbines without the need for significant structural modifications. This retrofit capability makes the invention both scalable and cost-effective, enabling wind farm operators to upgrade their turbines and maximize energy output without incurring substantial costs. The invention is also highly versatile, with multiple configuration options available to suit different turbine designs and operating conditions. The winglets can be arranged in straight, curved, or stacked configurations, depending on the specific needs of the wind turbine. Each configuration offers unique advantages in terms of aerodynamic performance, allowing the winglets to be customized for a wide range of applications. Description of the drawings Figure 1: An example of Barn Owl Figure 2: Base blade (without winglet) Figure 3: Blade with bio-inspired winglet Figure 4: Wind tunnel model of the blade with bio-inspired winglet Figure 5: Winglet configurations: (a) straight, (b) stacked, (c) curved Detailed Description of Embodiments The bio-inspired winglets (see an example in Fig. 3) consist of multiple feather-like structures designed to be attached to the tips of wind turbine blades. These winglets draw inspiration from the wingtip feathers of birds, such as barn owls (see Fig. 1), which are known for their exceptional ability to reduce drag and improve flight efficiency by manipulating airflow. The winglets are designed to mimic the cascading structure of these feathers, with each feather-like component decreasing in size from the leading edge to the trailing edge of the blade, which plays a crucial role in breaking up the vortices that form at the blade tips. This design reduces drag and improves the aerodynamic efficiency of the turbine, thereby increasing energy output and reducing mechanical stress on the turbine blades. Configurations Three primary configurations of the bio-inspired winglets have been developed and rigorously tested: straight, curved, and stacked. Each configuration is designed to optimize the performance of the turbine under different operational conditions, allowing for flexibility based on specific environmental factors, such as wind speed, direction, and turbulence. a. Straight Configuration: The straight configuration (see Fig. 5a) provides consistent performance across a range of wind speeds. It is the simplest and most direct application of the bio-inspired design, with the winglets aligned along the blade tip in a linear fashion. The straight configuration is particularly effective in steady, low to moderate wind conditions, where minimal variations in wind direction are observed. Its simplicity ensures that the winglets maintain consistent airflow separation, reducing vortex formation without complicating the aerodynamic profile. b. Stacked Configuration: The stacked configuration (see Fig. 5b) represents the most advanced and high-performance option, with multiple layers of winglets arranged in a stacked, feather-like manner along the blade tip. This arrangement closely mimics the structure of bam owl feathers, providing maximum disruption of vortex formation and allowing for significant improvements in aerodynamic performance. The stacked winglets are particularly well-suited for turbines operating in offshore environments, where wind speeds are consistently high and vortex formation is more pronounced. In testing, the stacked configuration demonstrated the best aerodynamic performance, with a 28% improvement in the lift-to-drag ratio and a 44% reduction in vortex strength. This configuration provides the most substantial improvements in energy capture, making it ideal for large-scale wind farms looking to maximize efficiency. c. Curved Configuration: The curved configuration (see Fig. 5c) features winglets that follow a slight arc along the blade tip, allowing for better adaptation to varying wind conditions. This design enhances the winglets' ability to handle fluctuating wind speeds and directions, making it ideal for wind turbines located in areas with highly variable weather patterns. The curvature allows the winglets to smoothly guide airflow over the blade surface, further reducing vortex strength and drag. This configuration is particularly effective in higher wind speeds, where the curvature helps to manage turbulent airflow. Performance and Testing The aerodynamic performance of the bio-inspired winglets was validated through a series of wind tunnel tests and CFD simulations. These tests were conducted across a range of operational wind speeds, from 5 m / s to 20 m / s, and with varying angles of attack from 0° to 25°. The wind tunnel model of the blade with bio-inspired winglet is illustrated in Fig. 4. The wind tunnel tests were performed in a controlled environment that simulated real-world wind conditions, allowing for precise measurements of lift, drag, and vortex formation. Meanwhile, the CFD simulations provided detailed insights into the flow dynamics around the winglets, enabling a thorough analysis of how the bio-inspired designs influenced airflow and vortex formation. Both wind tunnel testing results and CFD simulations results for the blade with bioinspired winglets are compared against those for the base blade without winglets (as illustrated in Fig. 2). The testing results confirmed that the bio-inspired winglets significantly improved the aerodynamic efficiency of the turbine blades. Across all three configurations, the winglets reduced vortex strength, resulting in less drag and improved lift-to-drag ratios. The stacked configuration, in particular, outperformed the other designs, offering the greatest gains in energy efficiency. These improvements were consistent across different turbine models and blade geometries, demonstrating the adaptability of the winglets to various operational scenarios. In addition to improving aerodynamic performance, the winglets also contributed to a reduction in mechanical wear on the turbine blades. By minimizing vortex-induced drag, the winglets reduced the mechanical stresses experienced by the blades during operation. This not only extended the operational lifespan of the blades but also reduced the frequency of maintenance required, further enhancing the overall cost-effectiveness of the system. Impact on Power Output and Efficiency The introduction of the bio-inspired winglets resulted in a significant increase in the total energy output of the wind turbines. Depending on the specific wind conditions and turbine size, the winglets provided a 5-7% increase in annual energy production. This improvement was particularly pronounced in offshore environments, where wind speeds are consistently higher, and the effects of vortex formation are more detrimental to turbine efficiency. The increased efficiency was largely attributed to the winglets’ ability to reduce drag and increase lift, resulting in more effective energy conversion from wind to electricity. This boost in energy output translates directly to financial savings for wind farm operators, as the turbines are able to generate more electricity without any additional input costs. Over the lifespan of a wind farm, the energy savings provided by the winglets can significantly improve the return 5 on investment, making the adoption of the technology highly advantageous for large-scale renewable energy projects. Retrofit Capability One of the most critical features of the bio-inspired winglets is their retrofit capability, which allows them to be easily attached to existing wind turbine blades without the need for significant structural modifications. This retrofit capability is a key factor in the scalability of the invention, as it enables wind farm operators to upgrade their existing turbines without having to invest in entirely new systems. The retrofit process is straightforward and cost-effective. The winglets are designed to be compatible with a wide range of turbine models and blade geometries, making them highly adaptable to different turbine designs. Installation can be completed during routine maintenance cycles, minimizing downtime and disruption to the operation of the wind farm. This retrofit capability makes the winglets an attractive solution for wind farm operators looking to maximize the performance of their existing assets. Scalability and Versatility The bio-inspired winglets are designed to be highly scalable, meaning they can be applied to turbines of all sizes, from small onshore turbines to large offshore systems. The scalability of the winglets is achieved through their modular design, which allows for easy customization to fit different turbine blade lengths and shapes. Whether the turbine is part of a small communitylevel wind farm or a large-scale offshore installation, the winglets can be adapted to meet the specific requirements of the turbine. In addition to their scalability, the winglets are also highly versatile, capable of being applied to both horizontal and vertical-axis wind turbines. This versatility ensures that the winglets can be used in a wide range of turbine models and configurations, making them a valuable solution for wind energy projects worldwide. The adaptability of the winglets to different operational environments, from calm onshore winds to turbulent offshore conditions, further enhances their appeal as a universal solution for improving wind turbine performance. Prototype Manufacturing and Scaling The physical prototype of the bio-inspired winglets was produced using advanced 3D printing techniques, which allowed for precise control over the shape and size of the winglets. The 3D printing process utilized polylactic acid (PLA) material, which offered a balance between precision and cost-efficiency. The prototype was scaled to match the operational parameters of small to medium-sized wind turbines, but the design can easily be scaled up for larger offshore wind turbines. The materials used in the production of the winglets were carefully selected to ensure durability and performance in extreme environmental conditions. For offshore turbines, in particular, the winglets must be able to withstand high winds, saltwater exposure, and temperature fluctuations. The use of advanced materials such as carbon fiber composites ensures that the winglets maintain their structural integrity under these conditions, while still providing the lightweight characteristics necessary for optimal aerodynamic performance. By utilizing 3D printing, the winglets can be customized to fit the specific geometries of different turbine blades. This ensures compatibility with a wide range of turbine models and allows for rapid prototyping and iteration during the design and testing phases. The ability to quickly produce and test prototypes using 3D printing technology has been instrumental in optimizing the performance of the winglets, ensuring that they meet the highest standards of aerodynamic efficiency.

Claims

The claims associated with this invention cover:1) A bio-inspired winglet system for wind turbine blades designed to reduce vortex-induced drag and improve aerodynamic efficiency, wherein the winglets are modeled after the structure of bird wingtip feathers.2) A feature of the winglet system is that the winglets decrease in size from the leading edge to the trailing edge, mimicking the cascading structure of barn owl feathers to disrupt vortex formation.3) The winglet system includes multiple configurations, such as straight, curved, and stacked designs, which are adaptable to various turbine blade geometries and operational wind conditions.4) The straight configuration of the winglets provides consistent performance across low to moderate wind speeds, ensuring minimal disruption to the aerodynamic profile of the turbine blades.5) The curved configuration of the winglets enhances performance in fluctuating wind conditions by guiding airflow more effectively over the blade surface, reducing both drag and vortex strength.6) The stacked configuration of the winglets provides superior aerodynamic performance, mimicking the multi-layered feather structure of birds, and offering the most significant reductions in drag and vortex strength in high wind environments.7) Retrofit capability, allowing the winglets to be attached to existing wind turbine blades without requiring significant structural modifications.8) The retrofit installation process can be completed during routine maintenance cycles, minimizing turbine downtime and offering a cost-effective solution for upgrading wind turbines.9) Aerodynamic improvements provided by the winglet system include a 28% increase in the lift-to-drag ratio of the turbine blades, as demonstrated through wind tunnel testing and CFD simulations.10) Reduction of vortex strength by 44%, which leads to decreased mechanical wear on turbine blades and extends their operational lifespan.11) The installation of bio-inspired winglets results in a 5-7% increase in the total energy output of wind turbines, depending on the specific wind conditions and size of the turbine.12) The winglet system is scalable, allowing for customization to meet the requirements of both small onshore turbines and large offshore wind energy systems.13) The versatility of the winglet system enables it to be applied to both horizontal-axis and vertical-axis wind turbines, making it compatible with a wide range of turbine designs.s