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![Free fall terminal velocity of water droplets through stagnant air for a range of stable droplet diameters. Data source: [44].](profile/Mark-Keegan/publication/258261403/figure/fig12/AS:11431281211334596@1702388585800/Free-fall-terminal-velocity-of-water-droplets-through-stagnant-air-for-a-range-of-stable.jpg)
Free fall terminal velocity of water droplets through stagnant air for a range of stable droplet diameters. Data source: [44].
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![Blade length and rated power trends for wind turbines. Source: [3].](profile/Mark-Keegan/publication/258261403/figure/fig1/AS:11431281211298427@1702388584055/Blade-length-and-rated-power-trends-for-wind-turbines-Source-3_Q320.jpg)
![Example of leading edge erosion. Source: [14].](profile/Mark-Keegan/publication/258261403/figure/fig3/AS:11431281211327571@1702388584383/Example-of-leading-edge-erosion-Source-14_Q320.jpg)
The increasing developments in wind turbine technology, coupled with an unpredictable operating environment, present significant challenges regarding erosion issues on the leading edge of the blade tips. This review examines the potential degradation posed by the different environmental variables, with specific emphasis on both rain droplet and hai...
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A dynamic model of gear transmission system of wind turbine is built with consideration of randomness of loads and parameters. The dynamic response of the system is obtained using the theory of random sampling and the Runge-Kutta method. According to rain flow counting principle, the dynamic meshing forces are converted into a series of luffing fat...
Citations
... Wind turbines are getting larger and are expected to operate at still more extreme weather conditions during their service life [1]. Leading edge erosion (LEE) is the phenomenon of airborne particles such as rain, hail and sand, hitting the blade at very high impact velocities, thereby causing a deterioration of the surface material on the leading edge of the blade [2]. ...
Leading edge erosion on wind turbine blades can reduce aerodynamic efficiency and cause increased maintenance costs, potentially impacting the overall economic viability. Erosion-safe operation is the concept of reducing the blade tip speed during periods of heavy rain, thereby significantly reducing the erosion development and progression. This study explores the application of reinforcement learning, namely using a double deep Q-network, to implement erosion-safe operation. The proposed methodology involves learning a policy for tip speed control that maximizes revenue over a specific period of time. We demonstrate the concept based on 5 years of simulation of the DTU 10MW reference turbine and mesoscale weather simulation from Horns Rev. The trained model was found to increase the cumulative revenue by 1.6 % compared to not using erosion-safe operation. The model was able to effectively adapt to varying weather conditions and stochastic damage progression. Based on 10,000 random simulations, the trained model outperforms two baseline models in more than 98 % of the simulations.
... When contemplating the selection of blade materials, meticulous attention should be devoted to the properties of the operating medium and its power density. The focus on associated issues should be concentrated as follows: Firstly, the heightened thrust and shear forces resulting from increased medium density necessitate shorter and thicker blade profiles [112]. Therefore, a reasonable consideration of material selection and structural layout is imperative to meet the strength requirements. ...
Over the past few decades, marine current energy utilization has transitioned from conceptual demonstrations to industrial-scale prototypes. This progression now approaches a crucial phase emphasizing the need for industrialization and commercialization. This paper provides an in-depth examination of the developmental status of large-scale marine current turbines and arrays, underscoring the promising prospects for marine current energy systems. Despite the significant advancements, the deployment of these systems has revealed several challenges, including blade design optimization, transmission system selection, and the establishment of appropriate test sites. Addressing these issues is essential for technological maturity and economic feasibility, which will foster the next wave of innovation in marine energy systems. Furthermore, the paper offers various perspectives for future applications.
... A typical tip wind speed is chosen to be around v tip = 80 . . . 90 m s −1 to limit the impact of leading edge erosion [238] or acoustic noise emission [239]. To reduce the torque on the shaft and thus its mass, design tip speeds have been increased to 104 m s −1 for rotor diameters from 164. . . ...
Tunneling cracks in the adhesive layer of the trailing-edge (TE) joint can be initiated early in the lifetime of a wind turbine blade. Two major types of loads affect the crack initiation: thermal residual stresses that develop during manufacture, and mechanical stresses due to operating loads. Although giving consideration solely to the longitudinal stress component, which contributes mainly to the fatigue, is state-of-the-art, the current design guideline encourages designers to also take account of other stress components, i.e., peel and shear stresses.
Hence, this research investigates the impact of the multi-axial stress state due to cyclic loading on the tunneling crack initiation in the TE adhesive joint in order to develop an engineering approach for predicting the number of load cycles toward crack initiation. First, this research analyzes the stress-life of a polymeric neat adhesive material. Second, this research analyzes the crack initiation in the thick adhesive sandwich joint. To this end, a two-dimensional (2D) finite element (FE) model of the adhesive joint to approximate the asymptotic stress field at the bi-material corner is introduced. Third, this research analyzes the crack initiation in the TE adhesive joint of a full-scale rotor blade. To this end, the 2D FE model of the joint is extended to take account of the adhesive layer’s free-edge geometry, as well as the boundary conditions, and the multi-axial thermal and mechanical internal loads in a blade. Fourth, this research analyzes the crack initiation in the TE joint of a rotor blade subjected to field loads.
The Stüssi-Boerstra stress-life (S-N) model derived was found to reliably predict the fatigue life in the high-cycle fatigue regime with the lowest standard deviation. The present 2D FE model together with a calibration approach with an S-N model gave a better prediction of the crack initiation than classical laminated plate theory in a test campaign of a structural detail, namely a generic thick adhesive sandwich joint. The validity of the approach was proved in a cyclic full-scale test through the good agreement between the prediction of the approach parametrized with simulated test loads and observations on crack initiation made during the cyclic test. The thermal residual stress at the inner adhesive edge dominated the crack initiation. The stress level at the bi-material corner reacted very sensitively to fillet angle and adhesive thickness.
... Leading edge erosion (LEE) at wind turbine blades is the damage of the surface of the blades due to environmental impacts [1,2], where rain is one of the dominant contributors. The cost for repair of blades due to erosion is considerable [3] and therefore there is a focus on understanding blade erosion, prevention, protection [4], and mapping the environmental factors leading to erosion and areas that have heightened risk of erosion [5] and damage progression. ...
Empirical damage model Impingement to end of incubation Offshore conditions Leading edge erosion on wind turbine blades is a common issue, particularly for wind turbines placed in regions characterized by high wind speeds and precipitation. This study presents the development of a rain erosion atlas for Scandinavia and Finland, based on ERA5 reanalysis and NORA3 mesoscale model data on rainfall intensity and wind speed over five years. The IEA 15 MW reference wind turbine is used as an example to evaluate impingement water impact and erosion onset time for a commercial coating material. The damage progression is modeled by combining the wind speed and rainfall data with an empirical damage model that relates impinged water (H) as a function of impact velocity to the time of erosion onset. Comparative analyses at two weather station locations show that NORA3 data more accurately aligns with measurements in terms of power spectral density, mean wind speed, rainfall, and erosion prediction than ERA5. NORA3-based atlas layers offer finer spatial detail and predict shorter erosion onset times over land compared to ERA5, particularly in complex terrain. Conversely, the ERA5-based atlas suggests a shorter onset of erosion offshore. Based on NORA3 data, erosion onset time is estimated at 5 years on average for Baltic Sea wind farm sites and 3.2 years for sites in the North Sea.
... Day by day wind turbine (WT) blade size is also increasing consistently to boost power capacity [2]. Keegan et al. [3] investigated the rain erosion issue of coating on WT blades. Rain erosion of wind turbine blade Leading Edge Protection (LEP) is a serious worry that increases maintenance and downtime and reduces continuous power generation. ...
... where, P is water hammer pressure and ρ o , c o and v o are the fluid density, speed of sound and impact velocity respectively [3]. ...
During operation, wind turbine blades are subjected to a wide range of environmental and loading conditions
and blade erosion can have a negative impact on performance and power production. The layer-wise thickness of
a leading edge coating system can have a substantial effect on erosion rate due to rain droplet impact, which can
result in a variety of complex failure modes, such as delamination of the coating-substrate interface. The
objective of this work to develop single droplet numerical models to investigate the influence of elastic stress
wave developments generated during impact. Following that, a single rain droplet FE parametric research was
performed with different coating materials, coating and filler putty thicknesses. It is shown that stiffer coatings
lead to higher stresses. Furthermore, thicker coatings can result in lower stress transfer to the filler material. The
empirical equations developed for coating thickness and filler putty thickness were found to be in good agreement
with each other. This detailed baseline investigation can help in understanding the effect of coating and
filler putty thickness on rain erosion rate, as well as analysing different coating designs using empirical equations
for the development of more durable leading edge protection coatings for wind turbine blade applications.
... To protect against environmental exposure, coating materials are applied to the outer surface of the blades. Blade manufacturers use two types of coating: epoxy/polyester-based gelcoat applied during manufacturing [63,64] or flexible polyurethane coating/leading edge protection tape applied afterward [64,65]. Delamination or debonding between the coating and substrate can accelerate leading edge erosion. ...
This paper addresses the critical issue of leading edge erosion (LEE) on modern wind turbine blades (WTBs) caused by solid particle impacts. LEE can harm the structural integrity and aerodynamic performance of WTBs, leading to reduced efficiency and increased maintenance costs. This study employs a novel particle-based approach called hybrid peridynamics–discrete element method (PD–DEM) to model the impact of solid particles on WTB leading edges and target material failure accurately. It effectively captures the through-thickness force absorption and the propagation of stresses within the leading edge coating system composed of composite laminates. The amount of mass removed and the mean displacement of the target material points can be reliably calculated using the current method. Through a series of tests, the research demonstrates the method’s ability to predict impact force changes with varying particle size, velocity, impact angles and positions. Moreover, this study offers a significant improvement in erosion prediction capability and the development of design specifications. This work contributes to the advancement of WTB design and maintenance practices to mitigate LEE effectively.
... Droplet erosion indicates continuous impacts of rain droplets or high-speed airborne droplets [45]. For a representative case of a working offshore wind turbine coated with SHS as an anti-icing coating, rain droplets or sea spray droplets would impinge onto the exposed surface at a high relative velocity of around 80 m/s [46]. Some impinged water droplets may penetrate the micro-scale surface textures of superhydrophobic coatings, which refers to the wetting transition from the non-wetted Cassie-Baxter state to the Wenzel state, thereby, eliminating the hydrophobicity and icephobicity of the SHS. ...
Icing is a severe hazard to the flight safety of unmanned aerial vehicles (UAV) in cold climates. Great efforts have been put into developing a reliable and practical anti-/de-icing system for icing mitigation. Compared to the conventional thermal-based deicing systems, applying superhydrophobic coatings with excellent ice-repellent performance is a promising anti-icing technique with low weight and low energy input. However, the application of superhydrophobic coatings on UAV is hindered by the substandard durability. This chapter comprehensively reviews advances in durability tests of superhydrophobic coatings pertinent to UAV anti-/de-icing. This chapter specifically introduces the mechanism of degrading superhydrophobic coatings by droplet erosion, which is rarely discussed in previous studies but can cause severe damage to the surface topology by applying “water hammer pressure.” Consequently, recommendations are provided to facilitate a more systematic approach to conducting durability tests for superhydrophobic coatings.
... A common example are the rigid protective layers called gel-coats (similar to those used in the marine industry) that are applied in-mould at the start of the manufacturing process. More recently there has been an increase in the use of coatings that are applied post-mould that possess a low modulus, and are made from durable PU/PUR materials that are thought to reduce the impact energy of a droplet impact [122]. ...
... Many studies document the impact of UV degradation on polymeric coating materials, with most showing that mechanical properties begin to deteriorate with extended exposure [122,144]. An Exposure to moisture from rain, humidity or sea spray can also exacerbate damage to the blade [18,70]. ...
Offshore wind turbine blades are expected to remain in operation with minimal maintenance for 35 years. However, it is now estimated that up to £1.3 million is spent on each turbine during its lifetime due to leading edge erosion from the impact of rain droplets. Erosion can be reduced by limiting blade tip speeds, but with reduced restrictions offshore, the current trend is to increase the blade length and tip speeds to maximise the potential of wind turbine technology as a source of clean and renewable energy helping to tackle climate change.
Current polyurethane/polyurea based coating solutions for offshore wind turbines typically fail prematurely, reducing the aerodynamic efficiency of blades and significantly decreasing energy capture. While lifetime prediction models are available, they are commonly only suitable for homogeneous materials that undergo brittle failure. However, state-of-the-art models cannot accurately predict the effect of rain erosion on the lifetime of highly viscoelastic materials that are currently being developed at industrial levels. This limitation is thought to be due to a lack of understanding of the failure mechanisms and an inability to measure key material properties using standard methods that have been shown to vary due to loading and environmental conditions.
This project aimed to address the challenge of capturing the viscoelastic behaviour of several commercial coating systems relating the results with measured rain erosion performance. This was achieved through the down selection and adaptation of a set of quasi-static and dynamic physiomechanical tests which were used to study the effect of strain rates, load, and temperature, on key material properties. In parallel, accelerated rain erosion testing was used to determine each materials' erosion performance, allowing for correlations to be made to the measured material parameters. The work included utilising a design of experiment approach, which allowed for the influence of individual and combinations of test parameters to be quantified and detailed the preliminary results of a bespoke thin film testing approach.
The main findings indicate that modern viscoelastic coating systems show considerable strain rate and temperature-dependent behaviour that affects both the quasi-static and dynamic material properties. As a result, modern prediction models need to be adapted to account for variations resulting from different loading and environmental conditions.
Overall this thesis combines several techniques into an overarching methodology to characterise modern coating materials and compare their viscoelastic characteristics. This allows for rapid, relevant, and cost-effective laboratory test methods for early erosion performance screening, reducing overall development time.
... Some positive influence of rain was also reported such as cleaning of blades (Corten and Veldkamp, 2001) increasing power production. Rain can also have long-term effects as the kinetic energy of impacting raindrops can cause leadingedge erosion (LEE) on turbine blades reducing their aerodynamic performance; this in turn results in lower annual energy and increased downtime (Keegan et al., 2013). ...
Wind power production plays an important role in achieving UN’s (United nations) Sustainable development goal (SDG) 7 – affordable and clean energy for all; and in the increasing global transition towards renewable and carbon neutral energy, understanding the uncertainties associated with wind and turbulence is extremely important. Characterization of wind is not straightforward due to its intrinsic intermittency: activity of the field becomes increasingly concentrated at smaller and smaller supports as the scale decreases. When it comes to power production by wind turbines, another complexity arises from the influence of rainfall, which only a limited number of studies have addressed so far suggesting short term as well as long-term effects. To understand this, the project RWTurb (https://hmco.enpc.fr/portfolio-archive/rw-turb/; supported by the French National Research Agency, ANR-19-CE05-0022) employs multiple 3D sonic anemometers (manufactured by Thies), mini meteorological stations (manufactured by Thies), and disdrometers (Parsivel2, manufactured by OTT) on a meteorological mast in the wind farm of Pays d’Othe (110 km south-east of Paris, France; operated by Boralex). With this simultaneously measured data, it is possible to study wind power and associated atmospheric fields under various rain conditions. Variations of wind velocity, power available at the wind farm, power produced by wind turbines and air density are examined here during rain and dry conditions using the framework of Universal Multifractals (UM). UM is a widely used, physically based, scale invariant framework for characterizing and simulating geophysical fields over wide range of scales which accounts for the intermittency in the field. Since rated power acts like an upper threshold in statistical analysis of empirical wind power, efforts were made to use the theoretical available power as a proxy to see the difference. From an event based analysis, differences in UM parameters were observed between rain and dry conditions for the fields illustrating the influence of rain. This is further explored using joint multifractal analysis and an increase in correlation exponent was observed between various fields with an increase in rain rate. Here we also examine the possibility of differences in power production according to type of rain (convective or stratiform) as well as various regimes of wind velocity. While examining time steps according to wind velocity, power curves showed different regions of departure from state curve according to the rain rate.
... The uneven distribution of weight over the blade due to wind velocity leads to the failure of WECS. The wind blade should be designed with proper chord length, tip ratio, and even surface for avoiding these kinds of failures [13,14]. As the WECS are placed in open environmental conditions, it experiences ice loading like transmission lines [15]. ...
Wind energy conversion systems (WECS) have gained increasing attention in recent years as promising renewable energy sources. Despite their potential, a clear research gap exists: the majority of WECS underperform in low wind speed conditions, limiting their applicability in many regions. To address this problem, this study proposes a novel approach by developing a 100 W micro wind turbine using Polylactic Acid (PLA) to generate efficient power in low wind speed conditions. The proposed wind turbine design employs Blade Element Momentum Theory (BEMT), which is commonly used for modeling wind turbine performance. Geometric design, mechanical analysis, and aerodynamic analysis are the fundamental considerations for designing any machine. In this work, the CREO 3.0 three-dimensional modeling software is used to create the geometric design of the proposed work. The airfoil SD7080 is selected due to its superior aerodynamic performance, and mechanical properties such as Young's modulus, density, and Poisson's ratio are attained to evaluate the wind blade's performance. Additionally, ANSYS 15.0 is used to conduct a detailed analysis of the proposed wind turbine, evaluating properties such as equivalent stress, deformation, and equivalent strain. Both simulation (ANSYS 15.0) and experimental setups are used to investigate the proposed wind turbine's performance, and the corresponding results are presented and discussed in this manuscript. The results indicate a significant performance improvement of the proposed wind blade when compared to conventional and ABS wind blades, demonstrating its potential as a more efficient solution for WECS. This proposed wind turbine design overcomes the problems like underprformance in low wind speed conditions and the wind turbine efficiency in all regions.
