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The performance benefits of using tip devices on wind turbines has been well-documented. However, previous studies show that adding blade tip devices such as winglets leads to a significant increase in blade root bending moment, potentially requiring structural reinforcement with cost and weight drawbacks. A new and unique design philosophy for retrofit blade tip devices for wind turbines is presented. By balancing generated aerodynamic and centrifugal loads, these devices offer an increase in power production without the need for structural reinforcement. Predicted performance and cost benefits of using retrofit blade tip devices on the National Renewable Energy Laboratory 5 MW reference wind turbine are shown. The addition of blade tip devices resulted in significant improvements in the coefficient of power (Cp) and annual energy production (AEP). [ABSTRACT FROM AUTHOR]

[Introduction] With the development of wind power generation technology, the unit capacity of permanent magnet wind generator is increasing, and the heating power is also increasing. The heat dissipation of generator is facing unprecedented challenges. How to effectively solve the problem of generator temperature rise and heat dissipation difficulty has been the focus of our study. [Method] Based on the STAR-CCM+ software platform, an integrated numerical simulation method for generator heat dissipation and cooling was proposed in this paper. The reliability of the numerical calculation method was verified by comparing the calculated values with the experimental values. On this basis, a study was conducted on the internal temperature distribution law and the factors influencing the cooling system heat dissipation performance of the high power permanent magnet wind generator. [Result] Under the rated power, the highest temperature of the winding and stator core appear in the middle area. If the process conditions allow, the cooling water pipe should be as close to the winding as possible to take away more heat. The stator core temperature and winding temperature can be reduced significantly by increasing the total intake air volume of the generator. The intake air temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake air temperature, the maximum temperature will be reduced by about 1.4℃. Reducing the intake air temperature can improve the heat dissipation performance of the generator to a certain extent. The intake water temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake water temperature, the maximum temperature will be reduced by about 3.3℃. Reducing the intake water temperature can greatly improve the heat dissipation performance of the generator. In addition, the gap between the cooling water pipe and the stator core greatly hinders the heat transfer of the cooling water pipe. Filling the gap with materials with good thermal conductivity can effectively improve the heat dissipation performance of the generator. [Conclusion] The conclusions drawn in this paper can effectively guide the heat dissipation design of permanent magnet wind generator and ensure the safe operation of wind turbines in normal work.

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The noise emission of wind turbines and farms can be an important and limiting factor for future cost reductions and growth of wind energy. Closing scientific and technological gaps on wind turbine noise is thus directly supporting the further development of renewable energy while reducing adverse reactions toward wind farms. The present article is providing guidance on the most relevant research directions from an engineering perspective, namely: simulation methods, wind tunnel testing, and wind turbine design. Each topic is addressed separately and specific scientific challenges are identified. Future research directions that may improve our physical understanding of wind turbine noise, as well as facilitate the deployment of wind energy, are outlined. It is concluded that future scientific research on the topic of wind turbine noise should be conducted in a multidisciplinary context to maximize its impact. The suggested topics shall be seen as a collection of what is seen as the most relevant topics across research and product development but shall not be seen as exclusive or interlinked with specific development plans. This article is categorized under:Sustainable Energy > Wind EnergyHuman and Social Dimensions > Social Acceptance [ABSTRACT FROM AUTHOR]

The design of a wind turbine blade is a typical complex multi-objective optimization problem, mostly solved by evolutionary algorithms. However, these methods are not effective due to limitations such as inaccurate solutions on Pareto fronts for high-dimensional problems, numerous iterations and low adaptability to problems with similar conditions. To address these issues, two multi-objective deep reinforcement learning models are introduced in this paper from an entirely different perspective. The first model, namely the multi-objective deep deterministic policy gradient (MO-DDPG), extends the existing popular reinforcement learning algorithm DDPG to multi-objective optimization problems by integrating various techniques including modeling of constraints on high-dimensional spaces and generation of Pareto solutions. The second model, namely the multi-objective deep stochastic policy gradient (MO-DSPG), further improves the MO-DDPG by incorporating a random neural network called restricted Boltzmann machine (RBM). An adaptive random agent is trained to transform multiple deterministic policies into an optimal stochastic policy. In addition, neighborhood-based parameter transfer strategy is applied to MO-DSPG in the model training phase to reduce the computation time. Experiments showed that the aerodynamic performance of the blades is improved by both the MO-DDPG and the MO-DSPG models with the hypervolume increasing an average of 6.67% and 9.25% respectively, compared with the state-of-art models. The computational efficiency of MO-DSPG is improved by using the parameter transfer strategy, with its runtime reduced to 72.52% compared with state-of-art models. [Display omitted] [ABSTRACT FROM AUTHOR]

We review the development of wind turbines for generating electricity from the late 19th century to the present, summarizing some key characteristics. We trace the move from two and four blade wind turbines to the three blades common today. We establish that it was not the governmental-funded wind programs with its large-scale prototypes of the 1970–80s that developed into the commercial turbines of today. Instead, it was the small-scale Danish wind turbines, developed for an agricultural market, that developed into the commercial turbines of today. And we show that much of what we know today about wind turbine design was known by the 1930s and certainly well known by the late 1950s. This work is divided into two parts: the first part takes up the development from the first electricity producing wind turbines through to the 1960s and a second part on development from the 1970s onward. [ABSTRACT FROM AUTHOR]

We review the development of wind turbines for generating electricity from the late 19th century to the present, summarizing some key characteristics. We trace the move from two to four blade wind turbines to the three blades common today. We establish that it was not the governmental-funded wind programs with its large-scale prototypes of the 1970–80s that developed into the commercial turbines of today. Instead it was the small-scale Danish wind turbines, developed for an agricultural market, that developed into the commercial turbines of today. And we show that much of what we know today about wind turbine design was known by the 1930s and certainly well known by the late 1950s. This work is divided into two parts: the first part takes up the development from the first electricity producing wind turbines through to the 1960s and a second part on development from the 1970s onward. [ABSTRACT FROM AUTHOR]

This paper aims to propose a practical decision support model for the optimal design of future wind turbines based on available wind potential on the site of interest. A developed decision support model based a comprehensive wind turbine modeling and a constrained techno-economic optimization framework is presented. Optimization was subject to the Net Present Value (NPV) maximization of the net incomes from wind energy generation, under the constraints on wind turbine nominal power restriction and the maximum ratio permitted between the rotor diameter and tower hub height. Optimizations of rotor diameter and tower height sizing have direct impacts on energy and cost production, those parameters have been considered as the design variables. The optimal design selection considers: the nominal power, rotor diameter, and tower hub height, which led to the maximum NPV in a specific site. Furthermore, an analysis of the Levelized Cost of Energy production (LCOE) has been performed. The developed decision support model has been tested and applied to a case study to validate its application and performance. The developed model was verified and significant results were achieved using three different wind sites: Dakhla, Casablanca, and Tanger. Results showed that the optimal design of the wind turbine technologies is given by the limit conditions cited, conducting to the maximum NPV with low LCOE and more exploitation of available wind potential in Dakhla and Tanger; however Casablanca was found as no profitable site for wind projects presenting negative NPV.

A design and optimization procedure of simplified wind turbine rotors for small-scale applications is presented. The need for this research has arisen from the recent national initiative of the government of Sri Lanka titled 'Battle for Wind Energy' in promoting small scale grid connected wind plants for electricity customers under Net Metering scheme. The main objective of this research is to assist local developers to design optimum rotors for given electrical generators (as determined by customer requirements), suitable for wind characteristics at specific locations. Another objective is to enhance local manufacturing capabilities by providing a design option of a simplified rotor blade geometry. A study on the correlation between population density of electricity customers and wind energy potentials was carried out to categorize the demand centres based on wind energy potentials in proposing series of small-scale wind turbine designs. A unique and improved rotor design procedure is presented which attempts to match the point of maximum performance of a rotor (design tip speed ratio) with the design wind speed of a given location by considering generator performance. The new design procedure showed successful convergence on a unique blade diameter for each rotor configuration that allowed the design tip speed ratio to match the design wind speed. The performance evaluation of rotor designs showed that high solidity rotors work better on the low wind potential region while low solidity rotors dominate medium and high wind potential regions. The performance reductions of simplified rotor designs are not significant and therefore would be an effective way to enhance value addition through local manufacture. • Lack of a rotor design procedure that considers generator performance. • Lack of a rotor design procedure for blades with an optimum simplified geometry. • Geographical mismatch between high resource sites and location of electricity consumers in Sri Lanka. • Lack of optimized small-scale wind turbine designs for sites with different wind potentials in Sri Lanka. • Limited opportunities for local manufacture in Sri Lanka. • Identification of geographical locations most suitable for promoting small-scale wind turbines. • Creation of rotor design procedures for optimized and simplified blade geometries considering generator performance. • Creation of optimized and simplified wind turbine rotor designs for different wind potential regions in Sri Lanka. • Suitable geographical locations for promoting small-scale wind turbines in Sri Lanka • Improved rotor design procedure considering generator performance • Design procedure for rotors with simplified blade geometry. • Optimized rotor designs for different wind potential regions in Sri Lanka • Simplified rotor designs for different wind potential regions in Sri Lanka [ABSTRACT FROM AUTHOR]

This paper presents a method for multi-objective optimization design of wind turbines at the system level through a coupled blade-tower model, aiming at finding the coupling effects between blade and tower and improving the wind turbines' performances. The formulation and implementation that enable the aerodynamic and structural integrated design of the blade and tower simultaneously are detailed. The maximum annual energy production (AEP) and the minimum wind turbine mass are taken as two conflicted objectives. Main aerodynamic and structural parameters of the blade and tower are employed as design variables. Various design requirements including stress, strain, deflection, vibration and buckling limits are considered as constraints. The blade element momentum (BEM) theory combined with the finite element method (FEM) are applied to evaluate the aerodynamic performances and structural behaviors of the turbine. Moreover, the non-dominated sorting genetic algorithm (NSGA) II is used to achieve the best trade-off solutions between the objectives. To show the efficiency and reliability of the method, a commercial 1.5 MW wind turbine is used as a case study. Satisfactory results that can both increase the AEP and decrease the mass are obtained, which are superior to the results achieved by optimizing the blade and tower separately. • Wind turbine is optimized at the system level through a coupled blade-tower model. • Two conflicted objective functions are selected to achieve the best trade-off solutions. • The effects between the blade and tower are found under a specific wind condition. • Optimal results both increasing the AEP and decreasing the turbine mass are obtained. [ABSTRACT FROM AUTHOR]

Large scale wind turbines have been extensively examined for decades, but a very few studies have been conducted on small-scale wind turbines especially for the applications where artificial wind speed is of the order of 15 m per second. This study provides systematic effort towards design and development of small scale wind turbine aimed to operate at high wind speeds. The drag-based wind turbine has an enormous potential for small-scale power generation in cement manufacturing plant. It uses bag filter to prevent environmental pollution so as to let out the clean high velocity exhaust air through the duct. The work reported here presents to utilize exhaust air for electrical power generation. Exhaust air flow has been analysed in Ansys Fluent Software. Ansys Computational Fluid Dynamics (CFD) technology was adopted to evaluate the performance of the wind turbine. The results of torque assessment of the wind turbine in its static as well as dynamic condition have been presented. Experimental setup consisting turbine, generator, battery and load has been tested and validated. • The authors aim to develop wind turbine to operate at high speeds. • It uses exhaust air for power generation. • The ANSYS software is used for analysis. • The experimental and simulation results have been validated. [ABSTRACT FROM AUTHOR]

In recent years, the use of wind energy has become increasingly attractive for the successful and economic development. Wind energy is one of the fastest-growing renewable energy technologies of electricity generation. Wind energy has proved its potential in combating environmental degradation while ensuring a renewable, efficient and clean energy source. Good wind sites can even be competitive with traditional energy sources. In this paper, we used statistical methods namely Weibull probability density function for evaluating the wind energy potential as a power source in Morocco's regions, in particular Taza and Dakhla cities. Various methods were explored as wind variability, power density, standard deviation, Moroccan and WAsP methods for calculating the Weibull parameters using mean wind speed data measured at one-hour intervals. The wind data have been extracted at the height of 50 m and over a three-year period 2015–2017. Furthermore, the variations of monthly and annual wind speed are studied and the power and energy densities are evaluated. The monthly values of the Weibull shape parameter are on average 5.01 m/s at Taza and 9.04 m/s at Dakhla. The results obtained showed that the highest values of wind potential occur during March, July, September and December in Dakhla and during the December to March in Taza.

The present work considers the application to a medium‐size onshore wind turbine of passive load mitigation technologies, first individually and then integrated together. The study is conducted with the help of a comprehensive automated design optimization procedure, which eases the generation and comparison of consistent solutions, each satisfying the same overall requirements. Passive load mitigation is here obtained by inducing bend‐twist coupling to the blades. The coupling is generated by rotating the fibers of anisotropic laminates, by the aerodynamic sweeping of the blade and by offsetting the spar caps in opposite directions on the pressure and suction sides. The first two solutions yield significant benefits, while the third, for this particular wind turbine, is ineffective. In addition, the typical power losses associated with bend‐twist coupled blades are reduced by a novel regulation strategy that varies the fine pitch setting in the partial load region. After having considered each load mitigation technology by itself, fiber rotation and sweeping are combined together and used to design a rotor with a larger swept area. The final design generates cost of energy savings thanks to a large‐diameter, highly coned, soft‐in‐bending rotor that results in lower turbine costs and a higher energy capture compared with the baseline design. [ABSTRACT FROM AUTHOR]

Highlights • A mathematical approach to minimizing the turbine cost of energy based on wind statistics is developed. • The turbine cost of energy model includes the turbine rated power and the turbine rated wind speed. • A general procedure to minimize the turbine cost of energy is presented. • Wind sites with higher mean wind speed require higher turbine rated wind speed. • Turbine rated wind speed has a larger influence on turbine cost of energy than turbine rated power. Abstract With the aim of reducing green gas emission, wind turbine installations worldwide have grown rapidly in recent years. Wind energy itself is free, but has costs due to the wind turbine infrastructure and maintenance. The installation size of the wind turbine at a specific location is not only determined by the wind statistics at that location, but also by the turbine infrastructure and the maintenance cost. The payback time of the turbine is determined by the turbine cost of energy (COE). In this paper, a mathematical approach is proposed to minimize the turbine cost of energy based on wind statistics. Turbine annual energy production (AEP) is calculated based on turbine output power and annual wind speed distribution. A wind turbine cost model developed by U.S. National Renewable Energy Laboratory (NREL) is used for turbine cost analysis. The turbine cost of energy model includes the turbine rated power and the turbine rated wind speed. Finally a general guideline to minimize the turbine COE is presented. Three case studies are conducted to show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This article presents a framework to integrate and optimize the design of large-scale wind turbines. Annual energy production, load analysis, the structural design of components and the wind farm operation model are coupled to perform a system-level nonlinear optimization. As well as the commonly used design objective levelized cost of energy (LCoE), key metrics of engineering economics such as net present value (NPV), internal rate of return (IRR) and the discounted payback time (DPT) are calculated and used as design objectives, respectively. The results show that IRR and DPT have the same effect as LCoE since they all lead to minimization of the ratio of the capital expenditure to the energy production. Meanwhile, the optimization for NPV tends to maximize the margin between incomes and costs. These two types of economic metrics provide the minimal blade length and maximal blade length of an optimal blade for a target wind turbine at a given wind farm. The turbine properties with respect to the blade length and tower height are also examined. The blade obtained with economic optimization objectives has a much larger relative thickness and smaller chord distributions than that obtained for high aerodynamic performance design. Furthermore, the use of cost control objectives in optimization is crucial in improving the economic efficiency of wind turbines and sacrificing some aerodynamic performance can bring significant reductions in design loads and turbine costs. [ABSTRACT FROM AUTHOR]

This paper presents the development of a comprehensive open-source numerical model to study the dynamic response and load analysis of floating offshore wind turbines. The model accounts for the wind inflow, rotor aerodynamics, multibody structural model of the system, wave and current kinematics, hydrodynamics, and mooring-line dynamics. This coupled simulation tool can be used for analysis, optimization and preliminary design to determine the technical and economic feasibility. Several verification and validation cases are performed to show the correctness of the numerical simulations. The results show that the proposed approach provides an accurate estimate of the wind turbine dynamics and loads. The simulation tool is then applied in the analysis of a 5 MW wind turbine aimed to characterize the dynamic response and to identify potential loads and instabilities resulting from the dynamic couplings between the turbine and the external conditions. This open-source fully coupled aero-hydro-elastic model provides a modular framework to enable investigating a variety of wind turbine configurations, support systems, and mooring lines. Therefore, it is expected that researchers and design engineers worldwide use the model to study, investigate and analyze different aspects of floating offshore wind turbine design, which results is the promotion and advancement of science and technology for floating offshore wind turbines. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a variable ratio gearbox (VRG) used in a small fixed-speed wind turbine with active blades. The major components of the VRG-enabled drivetrain are an automatic-manual gearbox and squirrel cage induction generator that connects directly to the grid. The simplicity of this system may be appealing for applications when cost and reliability are of concern. It is an alternative to variable speed systems, which necessitate a modified generator and power conditioning equipment. During partial load operation the VRG provides a discrete set of rotor speeds. This allows the controller to track the wind speed and to achieve a greater efficiency. This study suggests three VRG ratios are sufficient to improve performance when used with active blades. A case study is presented where the performance is simulated using three different wind data sets. The study suggests that the VRG can improve production between 7 and 8.5% in low wind areas. The design procedure also illustrates a technique for finding the lowest and highest gear ratios needed for VRG design. These ratios allow the system to achieve the lowest cut-in and rated speeds. The approach also has useful implications for the design of a continuously variable transmission. [ABSTRACT FROM AUTHOR]

Mitigating loads on a wind turbine rotor can reduce the cost of energy. Sweeping blades produces a structural coupling between flapwise bending and torsion, which can be used for load alleviation purposes. A multidisciplinary design optimization (MDO) problem is formulated including the blade sweep as a design variable. A multifidelity approach is used to confront the crucial effects of structural coupling on the estimation of the loads. During the MDO, ultimate and damage equivalent loads are estimated using steady-state and frequency-domain-based models, respectively. The final designs are verified against time-domain full design load basis aeroelastic simulations to ensure that they comply with the constraints. A 10-MW wind turbine blade is optimized by minimizing a cost function that includes mass and blade root flapwise fatigue loading. The design space is subjected to constraints that represent all the necessary requirements for standard design of wind turbines. Simultaneous aerodynamic and structural optimization is performed with and without sweep as a design variable. When sweep is included in the MDO process, further minimization of the cost function can be obtained. To show this achievement, a set of optimized straight blade designs is compared to a set of optimized swept blade designs. Relative to the respective optimized straight designs, the blade mass of the swept blades is reduced of an extra 2% to 3% and the blade root flapwise fatigue damage equivalent load by a further 8%. [ABSTRACT FROM AUTHOR]