Hidden Markov Models for Bounded, Inflated Time Series: Forecasting Icing on Wind Turbine Blades

The interaction between fluids and structures play an important role in number of fields. Important applications can be found in wind turbine blades, airplane wings, tall buildings, suspension bridges and biomechanics. The flow induced vibration (FIV) may affect negatively the operation and the response of the system. Flow induced vibrations in wind turbine blades is one of main considerations for the design of wind turbine, because aerodynamic loading causes blade to bend mostly in flap wise direction, and causes blade section to twist to create new fluid fields surrounding the blade. This interaction between aerodynamics and deformation of wind turbine blade may lead to flow induced vibrations. The aim of this research is to analyze the problem of FIV in wind turbine blade, due to the pressure field caused by a fluid flow. For this purpose, vertical axis wind turbine is analyzed using computational fluid dynamics and finite element analysis for the computation of vibratory stresses. Three dimensional flow analysis of vertical axis wind turbine (VAWT) blade is performed at different TSR ranges from 2.5 to 4.5. The aerodynamics results of CFD analysis shows that the maximum torque of 75 Nm is obtained at TSR 3.5. Finite element analysis (FEA) is then used for the computation of vibratory stresses. Carbon epoxy composite material with orthotropic properties is used as the blade material for FEA analysis. First one-way Fluid Structure Interaction (FSI) is conducted to determine stress field due to the torque on wind turbine blade. Next Modal analysis is performed to obtain the natural frequencies and corresponding mode shapes. Finally, the force response analysis of the structure is performed using ANSYS transient structural module under maximum unsteady wind torques which were computed using ANSYS Fluent. The outcome of the analysis showed that the three bending modes are the most critical modes for blade failure.

Prediction of ice shapes on a wind turbine blade makes it possible to estimate the power production losses due to icing. Ice accretion on wind turbine blades is responsible for a significant increase in aerodynamic drag and decrease in aerodynamic lift and may even cause premature flow separation. All these events create power losses and the amount of power loss depends on the severity of icing and the turbine blade profile. The role of critical parameters such as wind speed, temperature, liquid water content on the ice shape, and size is analyzed using an ice accretion prediction methodology coupled with a blade element momentum tool. The predicted ice shapes on various airfoil profiles are validated against the available experimental and numerical data in the literature. The error in predicted rime and glime ice volumes and the maximum ice thicknesses varies between 3% and 25% in comparison with the experimental data depending on the ice type. The current study presents an efficient and accurate numerical methodology to perform an investigation for ice‐induced power losses under various icing conditions on horizontal axis wind turbines. The novelty of the present work resides in a unified and coupled approach that deals with the ice accretion prediction and performance analysis of iced wind turbines. Sectional ice profiles are first predicted along the blade span, where the concurrence of both rime and glaze ice formations may be observed. The power loss is then evaluated under the varying ice profiles along the blade. It is shown that the tool developed may effectively be used in the prediction of power production losses of wind turbines at representative atmospheric icing conditions.

An influences of iced airfoils on aerodynamic and aeroacoustic properties were studied to predict of the wind turbine noise on icing state. In order to validate the aerodynamic performance, the experimental results and iced airfoils, which were studied by Jasinski et al. [“Wind turbine performance under icing state conditions,” AIAA Paper No. 97-0977, 1997], were used. Ice accretions on the two S809 wind turbine airfoils were predicted using the NASA LEWICE code. For analysis of boundary layer properties, the computational fluid dynamics was used when the Reynolds number is 1 × 106. To validate aerodynamic performances, lift coefficients were compared to the experimental result. The aeroacoustic analysis is estimated by summating the Turbulent inflow (TI) noise and the airfoil self-noise. The airfoil self-noise is obtained using aerodynamics data such as a boundary layer thickness. Semi-empirical method proposed by Brooks et al. [Airfoil Self-Noise and Prediction (NASA reference publication 1218, 1989)] was used. The TI noise is a dominant noise source because of a complicated shape of leading edge on the iced airfoil. For considering leading edge shapes, therefore, TI noise modeling proposed by Moriarty et al. [“Recent improvement of a semi-empirical aeroacoustic prediction code for wind turbines,” AIAA Paper 2004–3041, 2004; “Prediction of turbulent inflow and trailing-edge noise for wind turbines,” AIAA Paper 2005–2881, 2005] was used. As a result, lift coefficients of the iced airfoils matched well experimental data by Jasinski et al. The sound pressure level was increased 2–4 dB from the clean airfoils. The analysis of wind turbine blades on icing state was conducted using the same method. The NREL Phase VI rotor was used as the baseline. Ice accretions on the two wind turbine blades were predicted using the LEWICE code. The overall sound pressure level was increased up to 2.6 dB from the clean wind turbine blade.

This study presents to investigate the mechanical properties and thermal properties of horizontal and vertical axis wind turbine (VAWT) blade using finite element analysis (FEA) Ansys software. The efficiency of the wind turbine is based on the design of wind turbine blade (WTB) and material used. The fiber-reinforced plastics (composite materials) such as glass fiber, carbon fiber and epoxy are used for model of wind turbine blade. After modeling of wind turbine blade using standard software CATIA, imported into software ANSYS for determining the structural and thermal strength of the wind turbine blades. The stress distributions observed on the horizontal axis wind turbine blade due to the applied structural load and thermal load. The maximum stress occurs on the surfaces (near the fixed end of hub) of the horizontal axis wind turbine blade (HAWT), and the minimum stress occurs near the tip end of the blade. Due to the applied thermal condition (temperature) on the blades, the heat flux generated almost equal to both the HAWT blade and VAWT blade. Based on the FEA Ansys results, horizontal wind turbine blade produces better structural strength and thermal strength than vertical wind turbine blade.KeywordsWind turbine bladeFinite element analysis (ANSYS)Composite materialsStrength propertiesThermal properties

Wind turbines are susceptible to severe meteorological conditions, which can result in power loss. Several methods have been proposed to estimate the extent of power loss in wind turbines. This chapter aims to establish a foundation for new research and investigations into the impact of icing on wind turbine power output. It provides an overview of various methodologies available for estimating power loss in wind turbines under icing conditions. One of the prominent methods utilized in the past decade is computational fluid dynamics (CFD), enabling three-dimensional numerical simulations of wind turbines. When combined with the blade element momentum theory (BEM), CFD can also facilitate two-dimensional simulations. By analyzing these methodologies, researchers can gain insights into the estimation techniques suitable for studying icing effects on wind turbine performance. Understanding the magnitude of power loss under icing conditions is crucial for optimizing wind turbine design, operation, and maintenance strategies. Overall, this chapter contributes to the body of knowledge by consolidating various methods employed for power loss estimation in wind turbines subjected to icing.

Effects of deflection onto the performance of small wind turbines with flexible rotor-blades have been studied and analysed. The goal of the study has been the evaluation of the wind turbine output power loss due to angular deflection because of bending effects caused by gravity. Wind turbine blades have been deformed under constant load at the tip of the blade for periods up to 40 days. Deformation process has been accelerated using a very heavy load and the corresponding angular deflection has been obtained. Wind turbine performance has been characterized through the P-V curve for different wind speed operation conditions. Tests have been run for different deformation states to compare the evolution of the power loss with angular deflection. Results from experimental tests have shown there is a constant power loss with deformation increase. Power reduction for angular deflection of 2.3o is between 35% and 45% for blade tip wind speed from 27.6 m/s to 42 m/s. Power coefficient, C p , has also been analyzed and determined for the angular deflection of 2.3o and 4.3o; the reduction of the power coefficient value has been computed through a power loss factor, f P , that shows a reduction in the range of 25% to 50% for the 2.3o angular deflection, and between 45% and 55% for the angular deflection of 4.3o.

Design of optimized wind turbine airfoils and blades at high Reynolds number

To study the influence of blade rotation on the lightning attracting ability of wind turbine, the circular arc high voltage electrode with different radius is designed in this paper. Two 1:30 scaling wind turbines are symmetrical under the circular arc high voltage electrode. The blades of the wind turbine #2 remain upright and static, while the blades of wind turbine # 1 are at static with different angle and rotation with different speeds. The negative polarity 250/2500$\mu$s standard operating wave is applied to the high voltage electrode and the condition of lightning striking is observed by camera. The test results shew that in the 1m gap condition, the probability of lighting striking to the wind turbine #1 in rotation is smaller than that of when the wind turbine #1 is static, indicating that the rotation of blades reduced the lighting attracting ability of wind turbine. In the 2m and 4m gap, the probability of lighting striking to the wind turbine #1 under the rotation is smaller than that of when the wind turbine #1 is static, indicating that the rotation of blades strengthened the lighting attracting ability of wind turbine. According to the principle of discharge, the rotation of blades will strengthen the electric field of region of blade tip and reduce the electric field of outer region of blade tip, which will change the lightning discharge process. The results can be used as reference for wind protection.

Method using singular value decomposition and whale optimization algorithm to quantitatively detect multiple damages in turbine blades

Wind turbines are important for global energy production because of their low greenhouse gas emissions. However, for unknown reasons, many migratory bats are colliding with the wind turbine blades, leading to mass die-offs. As vision plays an important role for bats as they fly, often allowing them to avoid obstacles, one thought is that bats are visually attracted to wind turbines, causing them to mistakenly fly towards and fatally collide with the fast-moving blades. This idea led independent researcher Kristin Jonasson (USA) and researchers from the University of Colorado Colorado Springs, the National Renewable Energy Laboratory and the USDA Forest Service Pacific Southwest Research Station (all in the USA) to determine whether two of the most common migratory bat species affected by wind turbines in North America – hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) – were visually attracted to light reflecting off wind turbine blades.Between 15 September and 13 October 2024, the team caught 242 hoary and 154 silver-haired bats in Humboldt Redwoods State Park (CA, USA). They then transported the bats in cloth bags a short distance to a location where they had built a large Y-shaped structure, known as a Y-maze, for the bats to fly through. At the end of one of the two arms, the researchers placed an industry standard, glossy, white-painted decommissioned wind turbine blade illuminated by a light replicating moonlight. At the end of the other arm, the researchers placed a matte black-painted decommissioned wind turbine blade illuminated with replicated moonlight or an unlit matte black-painted decommissioned wind turbine blade, or they removed the wind turbine blade entirely and left the arm dark and empty. The researchers then released the bats individually into the maze, filming the animals as they flew through the structure and selected one arm of the maze or the other, while also recording their echolocation clicks, to find out whether the bats are attracted to the simulated moonlight reflecting off the white or the black wind turbine blades.The researchers found that both species flew through the arm of the Y-maze with the illuminated white-painted wind turbine blade twice as often as the arm with the matte black-painted wind turbine blade (lit or unlit) or with no wind turbine blade. From this, they concluded that bats are likely attracted to the simulated moonlight reflected from the wind turbine blade. Additionally, the bats chose the white-painted wind turbine arm more often than the dark empty maze arm (97% of hoary bats and 74% of silver-haired bats), suggesting that these bats prioritize vision over echolocation as they navigate through the air, even though all of the bats were confirmed to be echolocating while they were flying.Overall, Jonasson and colleagues have successfully shown that two North American migratory species of bats are visually attracted to moonlight that reflects off wind turbine blades. A future step in protecting these bats is to make sustainable changes to wind turbines, so they can continue generating electricity while ensuring that bats are not in peril from their fast-moving blades.

An in-house aero-elastic vortex code, called MIRAS, is used to investigate the aerodynamic performance of winglets and sweep on horizontal-axis wind turbine (HAWT) blades in simple and complex inflow conditions. Previous studies using vortex codes applied to study winglets and blade sweep on HAWTs have typically not considered complex inflow conditions such as turbulent wind and shear. The reasons may include the absence of modeling capability, the computational cost associated with simulating long turbulent time series, and/or the computational cost associated with resolving the blade tips to a very fine level. A preliminary study is performed here, where the MIRAS code is applied on the NREL 5MW wind turbine with an arbitrary winglet shape and blade sweep. Results indicate that wind turbine blades with sweep or winglets might be better in performance compared to their straight blade counterparts.

The roughness increase on horizontal axis wind turbine (HAWT) blade surface, especially on the leading edge, can lead to an aerodynamic performance degradation of blade and power output loss of HAWT, so roughness sensitivity is an important factor for the HAWT blade design. However, there is no criterion for evaluating roughness sensitivity of blade currently. In this paper, the performance influences of airfoil aerodynamic parameters were analyzed by the blade element momentum (BEM) method and 1.5 MW wind turbine blade. It showed that airfoil lift coefficient was the key parameter to the power output and axial thrust of HAWT. Moreover, the evaluation indicators of roughness sensitivity for the different spanwise airfoils of the pitch-regulated HAWT blade were proposed. Those respectively were the lift-to-drag ratio and lift coefficient without feedback system, the maximum lift-to-drag ratio and design lift coefficient with feedback system for the airfoils at outboard section of blade, and lift coefficient without feedback, maximum lift coefficient with feedback for the airfoils at other sections under the pitch-fixed and variable-speed operation. It is not necessary to consider the roughness when HWAT can be regulated to the rated power output by the pitch-regulated and invariable-speed operation.

Small-scale power plants injected into the existing distribution systems are commonly called as embedded or dispersed generation. The continuously increasing penetration of distributed generation becomes a challenge for conventional power systems. Recently developed distributed generation systems are mostly categorized into small scale plants in terms of power output. However, they are expected to be massive in terms of number. The power plants injection as well as their spread in the whole distribution systems will influence the power flow and losses in the network. Some researches have been undertaken recently to relate the embedded plants with the power losses and voltage profile of the networks. This paper presents a study on the influence of penetration level and concentration of distributed generation on power losses in the network. Steady-state power flow analysis is used to examine the power losses variation for a variety of distributed generation penetration. Based on the power flow analysis, voltage profile and power losses due to the power plants injection can be determined. The influence of various technologies used is also considered, including the use of wind power, photovoltaic and micro-hydro power plants. Four different scenarios to determine the effect of dispersed generation injection are proposed, starting from the original grid in the first scenario, being added with photovoltaic plant (0.5MVA) in the second scenario, the addition of wind power plant (0.5MVA) to the grid in the third scenario, and the fourth is the addition of microhydro power plant (1x2.5MVA) to the grid. The considered scenarios are based on the existing potential of the plants in the network system under concern, i.e. the Sengkaling Substation of the Pujon Feeder in Malang, Indonesia. Based on the analysis results, the injection of microhydro power plant (Scenario 4) presents the best influence being compared to the three other scenarios. The microhydro power potential is greater than that of the PV and wind power plants. Besides, it is well located in the middle of distribution system. From the point of view of power loss analysis, Scenario 4 also results in the smallest loss compared to the other scenarios. The least favorable losses reduction is given by Scenario 3 using the wind power plant injection, although the injection of renewable energy power plants in this study in general is proven to improve the voltage profile and reduction of power losses in the system.

Blade icing often occurs on wind turbines in cold climates. Blade icing has many adverse effects on wind turbines, and the loss of output power is one of the most important effects. With the increasing emphasis on clean energy around the world, the design and production of wind turbines tend to be large-scale. So this paper selected the 15 MW wind turbine provided by NREL (American Renewable Energy Laboratory) to study the influence of blade icing on output power. In this paper, a multi-program coupled analysis method named CFD-WTIC-ILM (CFD: Computational fluid dynamics; WTIC: Wind Turbine Integrated Calculation; ILM: Ice loss method) was proposed to analyze the whole machine wind turbine. Firstly, Fensap-ice was used to simulate the icing of the wind turbine blades, and then the icing results were input into WTIC for the integrated calculation and analysis of the wind turbine. Then, the WTIC calculation results were used to simulate SCADA (supervisory control and data acquisition) data and input into ILM to calculate the power loss. Finally, this paper analyzed the comprehensive influence of icing on output power. The calculation results show that the ice mainly accumulates on the windward side of the blade. Icing has a great influence on the aerodynamic characteristics of the airfoil, leading to a significant decrease in the power curve. The rated wind speed is pushed from 10.59 m/s to 13 m/s. The power loss of the wind turbine in the wind speed optimization stage is as high as 37.48%, and the annual power loss rate caused by icing can reach at least 22%.

In this research, the blade element momentum (BEM) theory of a horizontal axis wind turbine (HAWT) blade with 1 kW power output has been analysed for one station across the six geopolitical zones. Twenty years wind speed data (2000 – 2020) obtained from Nigeria meteorological Agency (NIMET) Head quarter, Abuja. In an effort to optimally explore and utilize wind energy, an optimal design of wind turbine blade needs to be obtained. Therefore, a computational method to analysed and optimize the performance of the wind turbine blades needs to be developed. For that purpose, a computational method based on the Blade Element Momentum (BEM) theory is developed in this study. In this method, the blade of a wind turbine is divided into several elements and it is assumed that there is no aerodynamic interaction amongst the elements. Furthermore, this (BEM) method incorporated with equations from momentum and blade element theories to obtain equations which are useful in wind turbine blades design process. In this research a computed result for aerodynamic characteristics based on BEM theory shows that, Maiduguri Metropolis is suitable for surface wind electrification among the selected stations with an estimated maximum wind power of 1.774𝑘𝑊 at total lift to drag ratio (𝐹𝐿/𝐹𝐷) of 27.2674 and a mean relative velocity of 14.99m/s. There is an agreement with my findings and that of other researchers.