No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Aerodynamic models for Darrieus-type straight-bladed vertical axis wind turbines
Abstract
Since ancient past humans have attempted to harness the wind energy through diversified means and vertical axis wind turbines (VAWTs) were one of the major equipment to achieve that. In this modern time, there is resurgence of interests regarding VAWTs as numerous universities and research institutions have carried out extensive research activities and developed numerous designs based on several aerodynamic computational models. These models are crucial for deducing optimum design parameters and also for predicting the performance before fabricating the VAWT. In this review, the authors have attempted to compile the main aerodynamic models that have been used for performance prediction and design of straight-bladed Darrieus-type VAWT. It has been found out that at present the most widely used models are the double-multiple streamtube model, Vortex model and the Cascade model. Each of these three models has its strengths and weaknesses which are discussed in this paper.
... The prominent aerodynamic modeling approaches for VAWTs include the BEM, Cascade, Vortex, ALM, and CFD models. 154 Panel methods also show promise as a viable approach for modeling VAWTs. [155][156][157][158] It is worth mentioning that the basic theory of ALM and CFD of VAWT is similar, the details will be elaborated further in this section. ...
... However, it faces numerical challenges and accuracy issues when dealing with rotors of high solidity, heavy loads, and high tip-speed ratios. 88,109,154,159 Compared with BEM models, cascade models provide more accurate overall values for both low and high-solidity rotors, 154 offering a practical solution. Cascade models were first applied to VAWTs by Hirsch et al. 171 They assumed that the rotor blades lie in a single plane, termed the cascade (as depicted in Fig. 28). ...
... However, it faces numerical challenges and accuracy issues when dealing with rotors of high solidity, heavy loads, and high tip-speed ratios. 88,109,154,159 Compared with BEM models, cascade models provide more accurate overall values for both low and high-solidity rotors, 154 offering a practical solution. Cascade models were first applied to VAWTs by Hirsch et al. 171 They assumed that the rotor blades lie in a single plane, termed the cascade (as depicted in Fig. 28). ...
Amid the escalating global demand for renewable energy sources, wind energy has emerged as a pivotal player, positioning itself as the primary energy solution for many countries and regions. The evolution of wind turbine technology has not only elevated the cost-effectiveness and efficiency of wind power but has also been instrumental in diversifying energy portfolios. From innovative blade designs to cutting-edge data analytics and extending its reach from land-based to deep-sea deployments, the breakthroughs in modern wind turbines are charting new horizons for sustainable development. This paper summarizes the conceptual design and most recent development of three types of novel wind turbines: two-bladed wind turbines, dual-rotor wind turbines, and vertical-axis wind turbines. Additionally, it delves into the aerodynamic research methods behind these three novel wind turbines. Our objective is to give readers a comprehensive insight into these research techniques.
... However, the algorithm behind these models is incapable of providing high-resolution information about fluid flow separation, vortex generation, etc. In addition, the main limitation of these stream tube models was that they were only applicable for symmetrical two-dimensional VAWTs and are insensitive to the curvature of aerofoil [12]. ...
... This model also provided an approach to predict the instantaneous aerodynamic force and the induced velocity for each stream tube experienced by the turbine blades. To increase the accuracy of MST model, Paraschivoiu [12,13] further modified this model by splitting the rotor actuator disc into upstream and downstream regions to estimate the axial induction value more precisely. Paraschivoiu's [18] double multiple stream tube (DMST) model was also capable of predicting the axial induction velocity for each azimuth position of blade inside the steam tube, which was developed based on blade element momentum theory (BEM) [19]. ...
... However, the vortex model was computationally costly to predict the performance more precisely [12]. These numerical models are more economical than the high fidelity computational and experimental (wind tunnels or field experiment) methods. ...
In this thesis, the role of active blade pitching on vertical axis wind turbine (VAWTs) technology is investigated under several turbine design parameters, i.e., geometrical (different number and aerofoil thickness, solidity) and operational conditions like Reynolds number (𝑅𝑒), tip speed ratio (TSR). This research mainly focuses towards identifying the flow-sensitive design parameters that can eliminate the dead band issue of wind turbines operating in low wind speed regions. The performance was evaluated utilizing high fidelity computational and low fidelity numerical approach. An analytical model was developed using the double multiple stream tube (DMST) method by integrating blade element with momentum theories. In addition, a high-fidelity URANS CFD model was set up to study the performance of H-rotor VAWTs. Active blade pitching was integrated in both models. The results were initially compared well with experimental literature data. The results indicate that the local widening of the angle of attack as function of azimuth position was very effective in performance enhancement as it minimizes boundary layer separation and maximizes the lift/torque force during the complete cyclic operation. The dead band issue of wind turbines at low TSR (1-3) can be eliminated by either adding a number of blades, increasing blade chord length, and reducing the rotor radius. Moreover, the investigation also shows that the pitching algorithm was very effective for three and four bladed rotor design to achieve maximum possible torque. The effect of varying aerofoil profiles, aspect ratio, solidity, and the number of aerofoil was also investigated, targeting the improvement in the self-starting of VAWTs for regions with low wind speed. The results obtained from soap film provided high-resolution information of boundary layer formation around variable pitching aerofoil that demonstrated the physics of flow behind the blades of VAWTs experiencing low performance
... This research focuses on a novel conceptual design and modeling of a hybrid nearshore wind-wave energy technology. The novelty lies in the integration of a high-efficiency wave energy converter inspired by [20][21][22] with vertical axis wind turbines (VAWTs) [23][24][25] in a nearshore deployment setting. Folley et al. [20] presented an examination of the nearshore exploitable wave energy resource. ...
... VAWTs have recently gained popularity due to their lower installation costs, ease of maintenance, and ability to run regardless of wind direction. Some typical works involving aerodynamic models and analyses of straight-bladed VAWTs were presented in [23][24][25]. ...
... The flow velocities of the wind turbine are shown in Figure 4. The tangent velocity Vt and the normal velocity Vn can be expressed in the following form [23][24][25]29]: ...
A modeling technique for a nearshore hybrid wind–wave energy converter system (HWWECS) is presented in this research. The model consists of the buoy, wind system, and generator, allowing simulation of the HWWECS’s behavior in response to varied wave circumstances, such as different wave heights and periods. The HWWECS is made up of two buoy units and a wind system that work together to power a generator. The Wave Analysis at Massachusetts Institute of Technology (WAMIT) software is used to calculate the hydrodynamic forces. A variable inertia hydraulic flywheel is used to bring the system into resonance with incident wave frequencies in order to improve power production.
... Por otro lado, la metodología QLLT es un modelo computacional de los conocidos como "Vortex method", el cual se plantea como flujo potencial y con ello se determina el campo de velocidad en el contorno del generador eólico con la influencia de la vorticidad en la estela de los alabes (Jin et al., 2015). Para este último método, las áspas de la turbina eólica se representan mediante componentes nombrados "lifting line" donde la dimensión se determina con los datos polares de los perfiles aerodinámicos (Islam et al., 2008), esta aplicación de la metodología en Qblade está basada en la investigación de van Garrel (Van, 2003), donde se asegura que el mencionado método tiene mejores resultados en cuanto a precisión, comparado con los métodos basados en "Blade element momentum". ...
... En el método QLLT el campo de velocidad se determina a partir de la influencia de vórtices en la estela de los álabes (Islam et al., 2008). La velocidad del viento en un punto determinado ecuación (3) se calcula a partir de la velocidad del flujo de viento sin perturbación más la velocidad inducida por los filamentos de vórtice, la cual, para un punto p se tiene: ...
En el presente trabajo se desarrolló el estudio de un rotor de aerogenerador Darrieus tipo Phi de 2 m de altura (para baja potencia) mediante los métodos Double Multiple Streamtube (DMS) y Qblade lifting line theory (QLLT) con la finalidad obtener los parámetros de configuración adecuados para el posterior diseño de un aerogenerador de eje vertical (VAWT) de dimensiones similares. Se realizó la comparación de ambos métodos con resultados experimentales reportados por otros autores, utilizando como referencia la estimación del coeficiente de potencia (Cp) en función de la relación de velocidad específica (TSR). Se encontró que el método QLLT es una mejor solución en términos de estimación del coeficiente de potencia, con un error absoluto máximo de 35 % y error promedio de 5 %. Sin embargo, dado el alto tiempo de cómputo en comparación con el método DMS es recomendable su uso en etapas avanzadas de diseño. Por otro lado, el método DMS con una capacidad de estimación inferior (error absoluto máximo de alrededor de 60 %, error promedio de 11 %) es adecuado para las primeras etapas de diseño dado su bajo tiempo de Cómputo.
... Hydrogen utilization in SI engines would give zero carbon-based emissions due to high localized incylinder temperature. However, hydrogen utilization in the SI engines is limited due to power de-rating (throttling losses), low thermal efficiency, low volumetric efficiency and high level of NOx emission [4]. ...
... The solar cell is a silicon p-n junction includes impurities atoms, when the sun light falls on the solar cell surface, the electrons have enough energy to be free, then many of electrons holes pairs are generated, so a potential difference is presented at the cell terminals, if the circuit is closed with external load that consumed electrical power, the current will be pass through this circuit [3][4] as shown in Figure 4-25. ...
Green hydrogen is an intriguing and environmentally friendly substitute that can help decarbonize the world economy by lowering reliance on fossil fuels and diversifying the energy system. Despite its extensive industrial applications, hydrogen still faces significant obstacles, such as high costs of production, storage, transportation, and electricity usage. This book investigates Egypt's capacity to generate green hydrogen using its abundant natural renewable resources, specifically to serve islanded electrical and hydrogen loads. The project detailed in this book integrates solar and wind renewable energy systems to ensure a sustainable and uninterrupted power supply to a Polymer Electrolyte Membrane (PEM) electrolyzer. The PEM electrolyzer utilizes the generated renewable energy to produce hydrogen from water through the electrolysis process. This hydrogen can then be used in various applications, including being blended with other fuels to power diesel engines or burners for winter water heating. Such integration ensures adherence to environmental standards while also proving to be economically beneficial. Key components of the system include the Archimedes Wind Turbine and solar panels, which have been meticulously designed and optimized for maximum efficiency. The experimental setup, instrumentation, and procedures are thoroughly described, alongside a detailed analysis of the data collected. The book also covers the theoretical and numerical studies conducted, including Computational Fluid Dynamics (CFD) simulations, to model and validate the performance of the integrated system. ABSTRACT ii Furthermore, the feasibility study section evaluates the economic and environmental impacts of the proposed green hydrogen production system in Egypt. It includes calculations of the Levelized Cost of Electricity (LCOE) and the Levelized Cost of Hydrogen (LCOH), as well as a life-cycle cost analysis and payback period estimation. The study highlights the potential for significant cost savings and reduction in greenhouse gas emissions, making a compelling case for the adoption of green hydrogen technologies in Egypt. In conclusion, this book provides a comprehensive guide to the production of green hydrogen using integrated wind and solar energy systems. It offers practical insights into overcoming current challenges and demonstrates the viability of green hydrogen as a sustainable energy solution for the future.
... 7 Therefore, these are used in small to medium-scale wind farms for several applications 1 such as water pumping, development of electricity, purifying or desalting water by reverse osmosis, cooling and heating using vapor compression heat pump, water bodies aeration and mixing, water heating by fluid turbulency, and offshore wind energy generation. 6,8 The VAWTs are categorized into Darrieus type and Savonius type WTs. 9 All these Darrieus type WTs are lift-based; thus, they use the lift forces acting on their blades for rotor rotation and power generation. 6 The Darrieus type VAWTs are small-scale VAWTs that consist of two or more than two straight or curved blades mounted on their rotational axis. ...
... The relevant parameters (a, k, lift coefficient (C L ), drag coefficient (C D ), torque coefficient (C T ), and C P ) used in Darrieus type SB-VAWT design for numerical analysis are expressed in Eqs. (1)- (8). The dynamic performance parameters of Darrieus type SB-VAWT are determined based on an experimental observation by applying Eqs. ...
Wind energy is one of the most eminent renewable sources for the generation of power. The increasing enthusiasm toward the advancement of small-scale Darrieus type straight-bladed vertical axis wind turbines (SB-VAWTs) can offer a potential remedy for addressing power shortage and the unpredictability of climate conditions. These particular wind turbines provide distinct advantages over their counterparts due to their linear blade design and uncomplicated structure. However, enhancements are required in their aerodynamic efficiency and self-initiation capabilities. These challenges stem from using traditional straight blade configurations and symmetrical airfoils. By substituting these conventional elements with J-shaped straight blades and along with cambered airfoils, these issues can be effectively overcome. The current study aims to investigate the effect of J-shaped straight blades with a series of cambered airfoils to improve the aerodynamic performance and starting torque of small-scale Darrieus type SB-VAWTs. Therefore, experimental and numerical studies are conducted to analyze the J-shaped airfoil impact with various opening ratios systematically. The J-shaped blade profile is designed by eliminating some portion toward the trailing edge of a conventional airfoil. This analysis demonstrated that the J-shaped blade incorporating a cambered NACA 4418 airfoil outperforms its alternative cambered airfoil designs. The performance of SB-VAWT improves by about 25% by the J-shape of the cambered NACA 4418 airfoil with a 70% opening ratio. Moreover, the use of J-shaped airfoils enhances the self-starting torque of SB-VAWT compared to conventional airfoils.
... Once 27 one of the blades stalls, the drag on that blade is significantly increased, which until the flow 28 reattaches to the blade will act to slow the rotation of the turbine. If a VAT has the capability 29 to change the pitch of the blades based on the local flow conditions, a control mechanism 30 can then be devised to mitigate the negative impact that a stalling blade would have on the 31 energy production. However, just reducing the impact that a stall has on the performance 32 of the turbine will not necessarily improve the turbine's performance. ...
... PLEASE CITE THIS ARTICLE AS DOI: 10.1063/5.0178535 AoA is given as follows [31]: ...
In this study, we developed active physics-informed turbine blade pitch control methods to conquer the inconsistent energy harvesting efficiency challenges encountered by the vertical-axis turbines (VATs) technology. Specifically, individual turbine blades were pitched by actuators following commands from the physics-informed controllers, and the turbine performance improvements as a result of the blade pitch control mechanism and the associated flow physics were studied. The aim of the blade pitch control was to maintain constant effective angles of attack (AoAs) experienced by turbine blades through active blade pitch, and the constant AoA function was designed to facilitate control mechanism implementation into real-world VATs. To gain in-depth understanding of the capability of the control, flow physics was studied for different constant AoA control strategies across a wide range of tip speed ratios and wind speeds and was compared with that from the corresponding baselines without control, and that from the sinusoidal AoA control strategy. The comparison between the turbine performance with constant AoA control and that without control showed a consistent increase in the time-averaged net power coefficient, a measure of energy harvesting efficiency taking out of the actuator loss, ranging from 27.4% to 704.0% across a wide spread of wind speeds. The superior turbine performance with constant AoA control was largely attributed to blade dynamic stall management during the blade upstream and downstream cycles and the transition between the two cycles.
... The experimental results obtained in wind tunnels showed that the power factor in the Savonius turbine increased with increasing overlap of the turbine blades. Islam (Islam, 2008;Islam et al., 2008) aerodynamically studied and analyzed different types of turbines. Takao et al. (M. ...
Within the framework of the global attempt towards reducing greenhouse gases and providing sustainable renewable energy to meet the growing energy demand, the research on the development of new renewable energy systems as well as on improving the efficiency of existing systems has gained great momentum over the recent decades. The applications and use of wind energy, a clean energy known and used since ancient times, have evolved in recent years. On the focus of several studies, either experimental or numerical, was developing novel wind turbines that offer greater efficiency. This research, in this respect, presents a numerical aerodynamic analysis of a helical blade vertical-axis wind turbine (VAWT) modeled in a wind tunnel in SOLIDWORKS and analyzed for its aerodynamic performance in ANSYS Fluent using the SST k-ω method. The stationary and rotary parts were meshed separately, and velocity and pressure contours were obtained and examined. The results of the numerical model suggested better performance of the hybrid helical blade turbine compared to Savonius or Darrieus turbines. The aerodynamic performance of a hybrid Savonius-Darrieus VAWT using numerical simulations in a three-dimensional wind tunnel revealed that the proposed design achieved a maximum torque of 2.05 Nm at a tip speed ratio (TSR) of 2.0, with a power coefficient (Cp) of 0.42, representing a 10% improvement over traditional Darrieus turbines. The hybrid design combines the high starting torque of the Savonius turbine with the efficiency of the Darrieus turbine, demonstrating superior performance in low-wind conditions. Numerical results were validated against experimental data from Castelli et al. (2011), showing good agreement with a maximum deviation of 10%. The findings highlight the potential of hybrid VAWTs for urban and low-wind environments, offering a sustainable and efficient energy solution. Öz Sera gazlarını azaltma ve artan enerji talebini karşılamak için sürdürülebilir yenilenebilir enerji sağlama yönündeki küresel çabalar çerçevesinde, yeni yenilenebilir enerji sistemlerinin geliştirilmesi ve mevcut sistemlerin verimliliğinin artırılması üzerine yapılan araştırmalar son yıllarda büyük bir ivme kazanmıştır. Antik çağlardan beri bilinen ve kullanılan temiz bir enerji olan rüzgar enerjisinin uygulamaları ve kullanımı da son yıllarda gelişmiştir. Deneysel veya sayısal olmak üzere birçok çalışmanın odak noktasında, daha fazla verimlilik sunan yeni rüzgar türbinleri geliştirmek yer almıştır. Bu araştırma, bu bağlamda, SOLIDWORKS'te bir rüzgar tünelinde modellenen ve k-ω yöntemi kullanılarak ANSYS Fluent'te aerodinamik performansı analiz edilen helisel kanatlı dikey eksenli rotorlu rüzgar türbininin (VAWT) sayısal aerodinamik analizini sunmaktadır. Sabit ve döner parçalar ayrı ayrı ağa bağlanarak hız ve basınç konturları elde edilmiş ve incelenmiştir. Sayısal modelin sonuçları, hibrit helisel kanatlı türbinin Savonius veya Darrieus türbinlerine kıyasla daha iyi performans gösterdiğini ortaya koymuştur. Üç boyutlu bir rüzgar tünelinde sayısal simülasyonlar kullanılarak hibrit Savonius-Darrieus VAWT'nin aerodinamik performansı, önerilen tasarımın TSR 2 değerinde ve 0,42 güç katsayısında 2,05 Nm maksimum torka ulaştığını göstermiştir; bu da geleneksel Darrieus türbinlerine göre %10'luk bir iyileştirme sağlandığını göstermektedir. Hibrit tasarım, Savonius türbininin yüksek başlangıç torkunu Darrieus türbininin verimliliğiyle birleştirerek düşük rüzgar koşullarında üstün performans gösteriyor. Sayısal sonuçlar, literatürde elde edilen deneysel verilerle doğrulanmış ve %10'luk maksimum sapma ile iyi bir uyum göstermiştir. Bulgular, hibrit VAWT'lerin kentsel ve düşük rüzgarlı ortamlar için potansiyelini vurgulayarak sürdürülebilir ve verimli bir enerji çözümü sunduğunu göstermektedir.
... The development of vertical-axis wind turbines took shape in the 1970s, wherein the Darrieus model patented by Georges Darrieus in 1926 emerged as one of the important designs. These turbines are characterized by their curved blades with a vertical axis of rotation and are thus independent of the direction of the wind; however, they were prone to mechanical stresses and low efficiencies at lower wind speeds [9]. Advanced material use, such as carbon fiber composites, has been employed to reduce blade weight without any reduction in the structural integrity of the blades, increasing rotational dynamics and turbine lifespan. ...
The global demand for sustainable energy sources has intensified the exploration of wind energy, especially for rural and off-grid communities. This study focuses on the development of a small-scale H-Type vertical-axis wind turbine (VAWT) as a viable solution for decentralized power generation in Biu, Nigeria. The H-Type turbine was selected for its simple design, low maintenance requirements, and ability to operate efficiently in varying wind directions. Materials used for the turbine included aluminum alloy blades, a steel tower, a permanent magnet generator, and reinforced concrete foundations. The construction involved fabricating and assembling key components—rotor blades, hub, shaft, tower, and generator—followed by installation and structural testing. Performance evaluation was conducted using standard formulas for power output, tip speed ratio, and efficiency, across varying wind speeds from 3 to 7 m/s. Results indicated that the turbine operated efficiently within the target wind speed range, achieving a maximum power output of 91.5 W at 7 m/s, with the nominal design output at 46.3 W. Efficiency peaked at 150% at moderate wind speeds (4.5 m/s), showing robust performance for small-scale applications. Structural analysis confirmed that stresses on components remained well within safe operational limits, ensuring turbine durability. The study concludes that H-Type VAWTs present a promising, low-cost solution for rural electrification, with further optimization recommended to enhance performance across broader environmental conditions.
... Two more publications on the practical applications of the Darrieus turbine can be cited here. These are the study by Islam et al. [9] and the work by Gharib-Yosry et al. [10], where the authors presented the operation of the Darrieus turbine rotor as a wind or hydro microgenerator. The Darrieus rotor is not provided with a wind orientation system, but due to its propelling torque of practically zero, it is necessary to use an auxiliary drive designed for start-up [11,12]. ...
This article presents the results of experimental and numerical studies on a single coherent rotor blade. The blade was designed for a vertical-axis wind turbine rotor with a self-adjusting system and planetary blade rotation. The experimental tests of the full-scale blade model were conducted in a wind tunnel. A computational fluid dynamics (CFD) analysis of the blade’s cross section was then carried out, including the boundary conditions corresponding to those adopted in the wind tunnel. The main objective of the study was to determine the aerodynamic forces and aerodynamic moment for the proposed single coherent cross-section of the blade for the carousel wind rotor. Based on the obtained results and under some additional assumptions, the driving torque of the wind rotor was determined. The obtained results indicated the possibility of using the proposed blade cross-section in the construction of a carousel wind rotor.
... The Darrieus VAWT's rotor comprises of aerodynamically designed turbine blades to extract kinetic energy from wind based on lift principles. To investigate the intricate aerodynamic characteristics and performance of Darrieus VAWT, various models have been developed, including Multiple Stream Tube (MST), Double Multiple Stream Tube (DMST), cascade, vortex, and panel methods [44]. Each model offers its own pros and cons that vary based on the wind conditions, wind turbine configuration, and the computational runtime. ...
This research delves into the performance enhancement of Vertical Axis Wind Turbines (VAWTs) through the innovative
approach of variable blade pitching based on Double Multiple Stream Tube theory principles. VAWTs, known for their
potential in urban and low-wind environment, often face efficiency and energy yield challenges. This study addresses
these challenges by proposing a novel variable blade pitching mechanism that dynamically adapts to changing wind
conditions, optimizing the aerodynamic performance, and enhancing the torque and overall performance of VAWT rotor.
The efficiency of two pitching models is investigated on 3-bladed NACA0015 rotors, where the blade's local angle of
attack is cyclically adjusted below the stall angle to maximize the lift force and torque throughout full revolution. In
Model 1, the angle of attack experiences cyclic variation as a sinusoidal function providing smooth pitching, whereas in
Model 2, the peak value of angle of attack was fixed below the stall condition forming linear function. The investigation
showed substantial improvement in the VAWT performance using both pitching models. The variable blade pitching
strategy significantly enhances the lift-to-drag ratio and thus improving the torque output across diverse wind scenarios/tip
speed ratios, demonstrating its effectiveness in maximizing the operational efficiency of VAWTs. Blade pitching model
1 and 2 were found to be effective across all lower Tip Speed Ratio (TSR) values, suggesting its robustness in variable
wind conditions. A peak average coefficient of performance (Cp) of 0.568 was achieved at TSR = 5 using pitching Model
1 with a maximum angle of attack of 8.5 degrees, compared to a Cp of 0.48 for the fixed blade configuration, near to
Betz’s limit (Cp = 0.593). The findings confirm that integrating variable blade pitching would substantially improve
VAWT performance and offer a clear direction for revolutionary future wind turbine aerodynamic design enhancements.
... Despite the simple structure of a straight three-blade H-Darrieus VAWT, as shown in Fig. 1, its aerodynamic analysis is quite complex. 29 The aerodynamic performance can be analyzed using the general mathematical expressions presented in this section. ...
This work investigates the interactions between time-harmonic gusts and a H-Darrieus vertical axis wind turbine (VAWT) using computational fluid dynamics. The motivation is to characterize the aerodynamic behavior of VAWTs in gusty urban environments. A systematic study on the gust response in torque, power output, and aerodynamic behaviors of the VAWT is conducted. Results show that gusts significantly impact VAWT performance by altering flow field perturbations and the blade angle of attack. Variations in gust amplitude and frequency lead to changes in aerodynamic efficiency and structural loads. When the gust amplitude reaches 55.6% of the steady wind, instantaneous torque fluctuations increase by approximately 20%, while the average power increased by no more than 2%. However, when the gust generation frequency is below the rotational frequency of the VAWT, it causes an angular shift in the instantaneous power peak and reduces power output by 2.5%. Finally, the instantaneous power coefficient of the blade in a asymmetric oblique gust reaches 0.79, contributing an additional 4% to the VAWT's power output.
... Jin et al. [7] and Islam et al. [8] evaluated research methodologies and applications of Darrieus VAWTs from various angles. Barnes et al. [9] provided a detailed summary of testing methods, including CFD, wind tunnels, and direct testing. ...
This study covers the structural optimization of vertical axis wind turbines (VAWTs) that can operate reliably for long periods of time in marine environments, as well as simulation analysis to evaluate their fatigue and strain resistance. Due to the nature of the marine environment, strong wind speeds and constant wave loads are applied, and VAWTs are likely to suffer from fatigue build-up and deformation problems in the long term. In this study, detailed numerical simulations were performed using ANSYS software (2024 R2) to analyze the effects of different airfoil shapes, material choices, tip speed ratios (TSRs), and foundation types on the turbine’s stress distribution and fatigue resistance. The results showed that NACA 0030 airfoil, composite steel, and single-pile foundation performed best under TSR 1.8 conditions, with the potential to reduce strain by approximately 30% and fatigue damage by approximately 25% compared to conventional structures. With this optimized combination, it was found that maintenance costs could be significantly reduced while maintaining structural stability at sea. These results could make an important contribution to the economical and durable design of VAWTs in the future.
... Whilst CFD simulations have been successfully applied, they are extremely computationally expensive; consequently most numerical studies perform only 2D analysis, e.g., [21], and it is currently infeasible to perform accurate 3D simulations of a large array. Moreover, various assumptions must be made, and accurately modelling the complex inter-turbine wake interactions is an extremely challenging task where different turbulence models can have a dramatic effect on turbine performance [33]. CFD studies have also presented significant differences between results even with identical geometric and flow conditions due to the complexity of performing accurate numerical analysis [1]. ...
Design mining is the use of computational intelligence techniques to iteratively search and model the attribute space of physical objects evaluated directly through rapid prototyping to meet given objectives. It enables the exploitation of novel materials and processes without formal models or complex simulation. In this paper, we focus upon the coevolutionary nature of the design process when it is decomposed into concurrent sub-design threads due to the overall complexity of the task. Using an abstract, tuneable model of coevolution we consider strategies to sample sub-thread designs for whole system testing and how best to construct and use surrogate models within the coevolutionary scenario. Drawing on our findings, the paper then describes the effective design of an array of six heterogeneous vertical-axis wind turbines.
... In the DMST methodology, instead of dividing the rotor blade into fixed sections, the rotor's perimeter is divided into a finite number of stream tubes. This approach, explained by Islam et al. [138] and Paraschivoiu [129], is illustrated in a new DMST code, as shown in the flowchart (Fig. 2). The process begins with defining the geometric parameters of the DVAWT, such as C, D, and blade configuration. ...
Self-starting torque (T_Self-starting) presents a significant challenge for Darrieus vertical axis wind turbines (DVAWTs), often necessitating external assistance to initiate rotation. This study addresses the issue by optimizing airfoil design, employing embossed blades (EBs), and adjusting blade height (H) to reduce T_Self-starting. From an analysis of 43 rotors at a chord-based Reynolds number (Rec) of 45,192, national advisory committee for aeronautics (NACA) 0015, NACA4412, and NACA4415 rotors were selected for their superior power coefficients (Cp). These rotors were optimized using double-multiple streamtube theory (DMST) and particle swarm optimization (PSO), focusing on the thickness-to-chord ratio (TCR). Among them, the NACA0015-Opt rotor achieved the highest Cp, demonstrating its effectiveness in enhancing DVAWT efficiency. This study also investigates the effect of H on the performance of EBs, comparing H of 35 cm and 75 cm. Experimental findings reveal that combining airfoil optimization with EBs, along with an increased H, leads to a substantial decrease in T_self-starting. Specifically, higher H enhance the aerodynamic performance of EBs by improving airflow over the blade surface, further reducing drag and contributing to a significant reduction in T_self-starting. At a H of 75 cm, the embossed blade Darrieus vertical axis wind turbine (EB-DVAWT) equipped with the optimized NACA0015-Opt rotor required 15.92 %, 17.04 %, 18.12 %, 21.23 %, 52.06 %, 49.23 %, 51.25 %, 35.20 %, 14.12 %, and 9.09 % less T_self-starting at wind velocities (U∞) of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 9.5 m/s, respectively, compared to the baseline smooth blade Darrieus vertical axis wind turbine (SB-DVAWT) with the original NACA0015 rotor.
... Bošnjaković et al., [1] explored minor design modifications, including rotor blade aerodynamics, active rotor blade rotation control, and aerodynamic brakes. Li [2], Kumar et al., [3], and Ghasemian et al., [4] respectively scrutinized the development of Darrieus turbines, while Islam et al., [5] compiled primary aerodynamic models for predicting the performance and design of straight-bladed Darrieus-type VAWTs. Bangga et al., [6] extensively evaluated different assessment methods, from DMST to fully resolved CFD approaches. ...
This research paper presents a comprehensive investigation of the performance and aerodynamic characteristics of a double-blade Darrieus wind turbine utilizing a NACA 0018 airfoil. The study combines wind tunnel testing and numerical simulations using Ansys software to analyze the turbine's behavior under varying wind conditions. Experimental measurements of torque, power output, and blade forces were obtained, while computational fluid dynamics simulations provided insights into flow patterns and pressure distribution. The results demonstrated close agreement between experimental and numerical approaches, validating the accuracy of the computational model. The analysis highlighted the influence of wind speed on turbine performance and the favorable aerodynamic characteristics of the NACA 0018 airfoil. The findings contribute to wind turbine design optimization and offer valuable insights for future research in renewable energy. Furthermore, the research identified the optimum case in the experimental method for the double-blade Darrieus vertical axis wind turbine. The results revealed that the most efficient position is situated at a distance of 4 cm and 3 cm from the rotor, which corresponded to 40% to 30% in terms of the distance ratio. Notably, a 6.7% improvement is observed when comparing single blade and double blade numerical results.
... Although vertical axis wind turbines have existed for centuries, they are not as common as their horizontal counterparts. The main reason for this is that they do not take advantage of the higher wind speeds at higher elevations above the ground as well as horizontal axis turbines [17,18]. A horizontal Axis Wind Turbine is the most common wind turbine design. ...
Renewable energies constitute an excellent solution for both the increasing of energy consumption and environment problems. Among these energies, wind energy is very interesting, caring and attentiveness. Whereas, the wind energy is the subject of advanced research. In the development of wind turbine, the design of its different structures is very important. It will ensure: the robustness of the system, the energy efficiency, the optimal cost and the high reliability. In this research, descriptive method was used for wind energy assessment in south Darfur state, where the wind speeds, atmospheric pressure and temperature were taken from Sudanese 1 statistically analyzed using statistical program as well as the seasonal distribution of wind speeds in the region. The results showed that the wind energy according to the analyzed data is too promised. The study confirmed that south Darfur state can be established wind energy farms in nowadays or in the future to generate electricity in order to solve the energy problems that the region has suffered throughout history of Sudan.
... The AOA was increased manually for each TSR. The study found that more accurate results will be found at high TSR; conversely Islam et al. [49] stated that the DMST model validity normally reduced at high TSR. Increasing the results manually could result in better performance within the rotor, however these changes are not always mechanically feasible and at some point, it might create high vibration rate as mentioned by Zhao et al. [21]. ...
... Contemporary variable pitch blade configuration has the potential to overcome the starting torque problem but it is overly complicated, rendering it impractical for smaller capacity applications (Islam et al., 2008). Tunio et al. (2020) recently investigated the pitch angle and blade profile effect on Darrieus hydrokinetic turbine performance. ...
This paper presents an investigation on the performance of a lucid spherical turbine. To verify the numerical predictions the experimental results of Bachant and Wosnik have been used. Drag and power coefficients have been used to compare with the data for the water inlet velocity 1 m/s and different non-dimensional tip-speed-ratio. Two airfoil sections, NACA 2412 and NACA 64(3)418, have been selected to design the turbine blades. The impact of four effective blade parameters, inclusive of profile section, chord length, number of blades, and blade twist angels, on turbine performance, is investigated. It can deduce that the power coefficient has increased up to 22% for NACA 2412 compared to the experimental test. Also, the three-bladed turbine possesses the best results among all models. The twist of the blades caused to increase in the power coefficient by 19% and 31% for NACA 2412 and NACA 64(3)418 sections inside the channel respectively. Reference to this paper should be made as follows: Zarei, H-r. and Pasandidehfard, M. (2024) 'Numerical investigation of lucid spherical cross-axis flow turbine concerning changeover on its geometrical parameters in a pipeline compared to a channel'
... Tip speed ratio (TSR, λ) is expressed in Eq. 6 (Islam et al., 2008b;Carrigan et al., 2012;Mohammed et al., 2019;Zhao FIGURE 2 Principles of VAWT (A) Free-body diagram of a 2-bladed H-Darrieus turbine. (B) Aerodynamics of a single aerofoil. ...
Omnidirectionality and simple design make VAWTs more attractive compared to HAWTs in highly turbulent and harsh operational environments including low wind speed conditions where this technology shines more. However, the performance of VAWTs is lacking compared to HAWTs due to low turbine efficiency at downstream caused by large wake vortices generated by advancing blades in the upstream position. Introducing variable design methods on VAWT provides better adaptability to the various oncoming wind conditions. This paper presents state-of-the-art variable methods for performance enhancement of VAWTs to provide better direction for the wind industry. The variable VAWT design can increase the lift and torque, especially at the downstream regions by managing the blade-to-wake interaction and blade angle of attack (AoA) well, hence contributing to the performance enhancement of VAWTs. In addition, the self-starting capabilities have also been found to improve by employing variable methods with a better angle of attack on the turbine blades. Nevertheless, the complexity of varying mechanisms and structural rigidity are the main challenges in adopting this idea. Yet, it possesses great potential to develop higher-efficiency VAWT systems that can operate in a wide range of wind speeds.
... The VP technique can adjust the blade to a pitching angle that maximizes the torque generated during the initial rotation [19]. This ability is a preferable advantage for residential and urban settings where inconsistent wind conditions might occur [20]. Moreover, the dynamic adjustment of the blade pitch angle provides better load management during high wind events. ...
Blade pitch angle regulation is an effective approach to enhance the performance of H-type Darrieus Vertical Axis Wind Turbines (VAWTs). Improving the blade interaction with the wind for this type of rotor is a challenging task, especially in unsteady wind conditions. This paper presents a novel hybrid approach that integrates fixed and variable blade pitch angle regulation techniques, aiming to enhance the wind turbine efficiency across various operational stages and wind speeds. The proposed blade pitch angle regulation method targets a less complicated, mechanically feasible, and cost-effective pitching technique. This study uses the Double Multiple Streamtube (DMST) model to analyze the aerodynamic performance and calculate the power output generated at different pitch angles. MATLAB Simulink was utilized to implement the DMST model, and experimental validation was conducted to confirm the results. The findings indicate that the blade pitch angle regulation has significantly enhanced the self-starting ability of H-type Darrieus VAWT by 80%. Additionally, the maximum rotational speed and power coefficient are achieved at a zero pitch angle. Furthermore, regulating the blade pitch angle allows for the effective control of excessive rotational speeds during high wind conditions.
... Moreover, it has been suggested that VAWTs are more appropriate in large scale (10 MW+) wind energy generation [35]. Very recently there has been a revivification regarding VAWTs and many researches have been carried out due to its aerodynamic efficiency and performance regarding flow separation and alleviating adverse effects on energy production [36][37][38]. It is observed that wind is always changing its speed, and direction is rarely uniform. ...
Wind energy has emerged as a prominent renewable energy source, offering a sustainable alternative to fossil fuels. This review article provides a comprehensive overview of the current state of wind energy technology, its environmental and social impacts, and future prospects. The historical development of wind energy is discussed, highlighting key milestones and technological advancements. Various wind turbine technologies are examined, including horizontal-axis and vertical-axis designs, as well as recent innovations such as offshore wind farms and floating turbines. The environmental benefits of wind energy, such as reduced greenhouse gas emissions, are contrasted with potential drawbacks, such as wildlife impacts and noise pollution. Integration challenges, such as intermittency and grid stability, are also explored, along with strategies to mitigate these challenges. The review concludes with a discussion of current trends and future prospects for wind energy, emphasizing its role in a sustainable energy future.
... Additionally, it has a slightly superior performance compared to the NACA0015 and the NACA0021 blade airfoils under moderate Tip Speed Ratio (TSR) conditions of around 2 (Islam et al., 2008;Mazarbhuiya et al., 2020;Zhang et al., 2020). (2) The H-Darrieus turbine has its blades attached to the support struts using either a fixed-pitch or a variablepitch systems. ...
A Vertical Axis Wind Turbine (VAWT) comprises multiple parts constructed from different materials. This complexity presents challenges in designing the blade structure. In this study, we investigated a structural optimization of a small-scale blade for a VAWT, with Finite Element Analysis (FEA) model. The purpose is to minimize the blade mass while adhering to a suite of critical wind conditions according to the IEC 61400-2 Standard. The structure made from Aluminum material simulates structure’s global behavior to determine maximum stress and deflection levels. The same structure is modeled using Glass/Epoxy composite for optimizing its design. Twenty combinations of Glass/Epoxy layers, varying in ply thickness and orientation, are simulated to find the most suitable combination. Results demonstrated that the optimization case [45°/90°/0°/−45°] obtained the minimum values of stress and deflection, is 59% lighter than Aluminum blade (initial design). The designed Glass/Epoxy composite blade is acceptable and recommended for structural safety.
... In this section, parametric revision and its effect on the turbine's efficiency are carried out by selecting twelve azimuthal blade positions and a velocity triangle at these positions is shown in Fig. 1. The various aerodynamic parameters required for the performance analysis of the turbine, FL and FD, and their perpendicular and peripheral components are presented in Fig. 2. [26][27][28] As discussed in the Introduction, 27,28 aerodynamic parameters are calculated using equations and formulas. ...
Small-scale Darrieus wind turbines have a wide scope in areas that are isolated from the power grid for such small-scale household applications. Applications of wind turbines on house roofs are one potential way to generate electricity from wind energy harvesting in low-wind urban locations. This work studies the aerodynamic behavior of a vertical axis wind turbine based on a MATLAB programming mathematical model. The NACA0021 airfoil profile blade was used in this present research investigation. The turbine was fabricated with dimensions such as chord length, c = 95 mm, blade height, h = 600 mm, and turbine diameter, D = 600 mm. The experimental results of the turbine for air velocity from 1 to 12 ms⁻¹ were used in this paper and compared with analytical results. It has been observed that the fixed-pitch turbine does not start by itself at a low air velocity of 1 to 5 m/s due to a minimum and negative torque.
... Despite the fact that typical maximum power coefficient values for other types of wind turbines range between 30% and 45%. The majority of researchers assert that the Savonius turbines are normally no greater than 25% [4]. ...
Due to its strategic location and ocean currents, the Sunda Strait has the potential to produce energy that might be used as a source of electricity. As a result, this strait area urgently needs a suitable turbine design. This strait's most significant sea current speed is 1 (one) m/s. The Savonius rotor is one of the rotor kinds of turbines that can operate in the slow sea current—modifying the rotor from semi-circular to use the Bezier curve for the shape to optimize the performance. This paper will discuss the design of the Savonius rotor using the Bezier curve, that have improved performance. The rotor with double stacking will also enhance the performance of the rotor. This design is a novelty for vertical marine current turbine applications in ocean renewable energy.
... Contemporary variable pitch blade configuration has the potential to overcome the starting torque problem but it is overly complicated, rendering it impractical for smaller capacity applications (Islam et al., 2008). Tunio et al. (2020) recently investigated the pitch angle and blade profile effect on Darrieus hydrokinetic turbine performance. ...
... A single streamtube model can be used for a turbine at low wind speed, however, in most cases the computed power is greater than for experimental results. [25][26][27] In another study, Strickland introduced multiple streamtube method 28 which contained a series of parallel independent streamtubes in the rotor domain and the momentum theory for each streamtube was used for each blade element. This model can be used for turbines with high tip speed ratios. ...
The attractive specifications of vertical axis wind turbine (VAWT) are its operating with low noise and wind in various directions. To achieve a higher performance of these turbines, modeling of a curved‐blade VAWT by the modified double multiple streamtube (DMST) method and optimizing this wind turbine are performed. The power coefficient and the total normal force acting on blades were selected as two objective functions. Minimizing the normal force acting on turbine blades as the second objective function was not observed in the open literature. The amount of normal force is crucial in the structural design of VAWT because it generates both the bending moment on blades and forces on supporting arms of VAWT. Another innovation of this study is to consider the shape coefficient parameter that determines the shape of the rotor geometry as a design variable in optimization procedure. A 3 m height curved‐blade VAWT type was optimized by this multi‐objective optimization technique. The optimum values of the design variables obtained by the Genetic Algorithm were selecting an elliptical rotor geometry, pitch angle −1.4°, diameter/height 1.3, blade aspect ratio 19.8, tip speed ratio 4.3 and selecting three blades which could provide a power coefficient of 0.49 and a normal force of 158.7 N.
... To analyze the performance and flow characteristics around turbines, low-fidelity models based on momentum, such as the double multiple-streamtube model, are employed Paraschivoiu (2002). Additionally, potential flow models, cascade models, vorticity models, and vortex transport models are used as moderate-fidelity methods Wang and Yeung (2016); Ferreira et al. (2014); Islam et al. (2008). However, Computational Fluid Dynamics (CFD) simulation, a high-fidelity method, has become widely adopted in wind energy research. ...
... These distinctive features characterise VAWTs as large-scale, unsteady, three-dimensional structures (Tjiu et al. 2015;Zhang and Hu 2020). However, the lack of fundamental theories and the complexity of aerodynamic behavior pose numerous challenges in the research process, resulting in a prolonged stagnation in the study and practical application of VAWTs (Islam, Ting, and Fartaj 2008). Despite these challenges, VAWTs have several advantages, including the ability to operate without yawing into the wind, low center of gravity, simple structure, low cost, low aerodynamic noise, easy installation and maintenance, high safety, and adaptability to complex environments (Guevara, Rochester, and Vijayaraghavan 2021;Guo, Chen, and Tian 2022;Ni, Miao, and Li 2022). ...
To investigate the effect of structural parameters on the aerodynamic characteristics of a Straight-Bladed Vertical Axis Wind Turbine (SB-VAWT), a 4-bladed SB-VAWT without an intermediate support shaft was designed to allow flexibility in changing structural parameters. Wind tunnel tests were conducted to measure the rotational speed, total lift, drag and torque of the wind turbine with different structural parameters at varying wind speeds. Based on the experimental design and optimisation, the wind turbine achieved the highest rotational speed and optimal power generation when the blades were installed in the forward direction at an installation angle of 10°, an installation radius of 160 mm, and a length of 600 mm. Under these optimal conditions, the speed and power generation characteristics of the wind turbine were tested at different wind speeds These results provide valuable insights for the design and application of similar wind turbines.
Vertical axis wind turbines (VAWTs) are suitable for urban installations due to their low noise and operational independence from wind direction and speed. In this paper, novel explicit dynamical modeling of a rigid-flexible vertical axis wind turbine (VAWT) with three degrees of freedom (DOFs)—including fore-aft and side-side bending of the tower and rigid rotor rotation—is introduced for the first time. Another significant novelty is the development of generalized aerodynamic lift coefficients applicable across a wide range of Reynolds numbers, overcoming limitations found in previous aerodynamic models. To enhance rotor speed regulation and power output optimization, model predictive control (MPC) and fuzzy-sliding mode control (FSMC) strategies are proposed and evaluated under both normal and disturbed operating conditions. Simulation results demonstrate that the FSMC strategy significantly outperforms conventional MPC in robustness, reduced computational complexity, and precise rotor speed tracking.
We improve the aerodynamic performance of a simplified vertical-axis wind turbine (VAWT) using a biomimetic flap, inspired by the movement of secondary feathers of a bird’s wing at landing (Liebe 1979 Aerokurier 12 54). The VAWT considered has three NACA0018 straight blades at the Reynolds number of 80000 based on the turbine diameter and free-stream velocity. The biomimetic flap is made of a rigid rectangular curved plate, and its streamwise length is 0.2c and axial (spanwise) length is the same as that of blade, where c is the blade chord length. This device is installed on the inner surface of each blade. Its one side is attached near the blade leading edge (pivot point), and the other side automatically rotates around the pivot point (without external power input) in response to the surrounding flow field during blade rotation. The flap increases the time-averaged power coefficient by 88% at the tip-speed ratio of 0.8, when its pivot point is at 0.1c downstream from the blade leading edge. While the torque on the blade itself does not change even in the presence of the flap, the flap itself generates additional torque, thus increasing the overall power coefficient. The phase analysis indicates that the power coefficient of VAWT significantly increases during flap opening to full deployment through the interaction with vortices separated from the blade leading edge. When the pivot point of flap is farther downstream from the leading edge or the flap operates at a high tip-speed ratio, the performance of the flap diminishes due to its weaker interaction with the separating vortices.
The marine environment is an abundant source of organisms which are rich in functional/bioactive compounds. Many of these compounds exhibit a remarkable potential for medical, industrial and biotechnological applications. Handled appropriately, with a focus on sustainability, these organisms and compounds can offer new and renewable feedstocks for a variety of industries. The biomass from marine organisms also offers opportunities for clean and sustainable fuel generation, carbon sequestration and wastewater remediation.
Focusing on the use of biomass from marine algae (both macro and micro), bacteria and yeasts this book looks at opportunities for producing high value chemicals with applications across multiple industries. It is an essential read for researchers interested in innovative, green feedstock sources, sustainability and the circular economy.
The vertical-axis wind turbines (VAWTs) are regarded as the best feasible alternative for small-scale power generation due to their design simplicity, ease of installation, good self-starting ability, and independency from wind direction among others. The dilemma of limited land, low onshore wind speed, and the abundance of high-speed wind near the ocean encouraged the researchers to explore the offshore fields. As a result, the lift-based VAWTs are becoming increasingly popular for large-scale offshore wind power production as well as small-scale urban applications. In the present review article, the historical evolution of lift-based offshore VAWTs from their inception to recent advancement has been discussed. The related geometrical and aerodynamic parameters, various loadings, and numerous models utilized in the design and analysis of offshore VAWTs have also been systematically reviewed. Finally, the challenges and the future scope of numerical research have been highlighted.
Wind energy provides a sustainable solution to the ever-increasing demand for energy. Micro-wind turbines offer a promising solution for low-wind speed, decentralized power generation in urban and remote areas. Earlier researchers have explored the design, development, and performance analysis of a micro-wind turbine system tailored for small-scale renewable energy generation. Researchers have investigated various aspects such as aerodynamic considerations, structural integrity, efficiency optimization to ensure reliable and cost-effective operation, blade design, generator selection, and control strategies to enhance the overall performance of the system. The objective of this paper is to provide a comprehensive design and performance review of horizontal and vertical micro-wind turbines. The study begins with an overview of the current landscape of wind energy across the globe and India in particular, highlighting key challenges and opportunities. Numerical and experimental studies were used to validate the designs. Horizontal Axis Wind Turbines (HAWTs) with ducts or shrouds are suitable for microscale and low-speed applications. Researchers investigated the position and location of the turbines to enhance their performance in urban settings. Airflow and airfoil noise produce aerodynamic noise, which is the most significant disadvantage of wind turbines. The findings provide valuable insights for stakeholders interested in advancing micro-wind turbine technology. The highlighted research opportunities may be pursued further to improve the efficiency, reliability, and overall performance of micro-wind turbines.
This paper describes numerical simulations of an innovative design of close-packed contra-rotating vertical-axis turbines (VATs), which enable assessment of power performance, vorticity distribution, and wake deficit. The design comprises a large diameter rotor without traditional supporting arms, stable in pitch and roll. Close-packing reduces leakage between rotors and yields a high blockage fraction, which significantly enhances the performance of offshore wind and tidal VATs. Rotor rings that support blades at both ends help reduce bending moments, and ease the task of the bearings required to achieve variable-pitch. The contra-rotation concept is based on two opposite-signed vortices cancelling each other out and conditions the flow though the turbine, lowering turbulent kinetic energy in the wake. Flow downstream of the turbines then experiences less stream-wise variation, reducing mixing losses and so enhancing energy extraction. Two types of VATs are considered. The first derives from experimental two-bladed H-type wind turbines, whereby the VATs comprise four close-packed contra-rotating wind turbines. The second is based on a 1:6 scale UNH-RM2 VAT that is extended to an array of ten closely packed 36-bladed hydrokinetic turbines positioned in two rows. It is found that high blockage, contra-rotating, vertical-axis rotors could facilitate higher potential power generation and appear to be a promising near-term technology for sustainable energy. The findings should prove useful in future assessments of the commercial feasibility of multiple cross-flow turbine configurations for both offshore wind and tidal stream power generation.
A new theory is introduced for the performance prediction of vertical axis Darrieus wind turbines. It is based on the concept of the cascade theory, similar to that used in turbomachines. The present cascade model avoids convergence problems found with the momentum theory at high tip speed ratios and for high solidity turbines. In order to apply the cascade concept to performance predictions, additional expressions for wake and induced velocities are introduced. Comparisons between calculated and experimental data indicate good correlations. (A)
A theoretical investigation of the effects of dynamic stall and flow curvature on the aerodynamic performance of vertical-axis straight-bladed Darrieus wind turbines is presented. The dynamic stall and flow curvature effects are added to the cascade model for the analysis. The experimental data and the calculated values of the instantaneous blade forces and the wake velocities show good correlation in most of the cases.
The objective of the present paper is to show the new capabilities of
the double multiple streamtube (DMS) model for predicting the
aerodynamic loads and performance of the Darrieus vertical-axis turbine.
The original DMS model has been improved (DMSV model) by considering the
variation in the upwind and downwind induced velocities as a function of
the azimuthal angle for each streamtube. A comparison is made of the
rotor performance for several blade geometries (parabola, catenary,
troposkien, and Sandia shape). A new formulation is given for an
approximate troposkien shape by considering the effect of the
gravitational field. The effects of three NACA symmetrical profiles,
0012, 0015 and 0018, on the aerodynamic performance of the turbine are
shown. Finally, a semiempirical dynamic-stall model has been
incorporated and a better approximation obtained for modeling the local
aerodynamic forces and performance for a Darrieus rotor.
This work has resulted in the publications of a monograph that summarises the performance areodynamics of a variety of wind actuated, power producing machines. Several areas important to wind power production were identified in which adequate aerodynamics models have not been developed. Under NSF/RANN Grant AER 74-04014 A03 the following topics will be studied: (i) aerodynamics of the Darrieus rotor; (ii) performance and configuration of the optimum horizontal axis rotor; (iii) aerodynamics of low-tip-speed, high-solidity horizontal axis rotors; (iv) aerodynamics of the Savonius rotor. In all these areas, some groundwork for the development of aerodynamic performance models has already been accomplished. (from paper)
A theory suitable for digital computation was developed that accounts for the main features of the performance of the NRC vertical axis wind turbine. The theory takes into account the curved blade shape and the effects of airfoil stalling on performance. A comparison is made between theoretical and experimental power coefficient and rotor drag coefficient. Numerical results are presented to show the theoretical effects of geometric variables such as blade solidity and rotor height-diameter ratio, and of variations in aerofoil aerodynamic characteristics.
The aerodynamic performance of a high-reliability vertical-axis wind turbine is discussed. The turbine has three, straight blades which are cyclically pitched. Due to its unique configuration, aerodynamic performance models used for classical horizontal-axis machines and for the vertical-axis Darrieus wind machines are not applicable. Therefore, an analytical model was formulated for the turbine aerodynamic performance and has been programmed for computer calculation. Both the mathematical model and computer program VAPE (Vertical-axis wind turbine Aerodynamic Performance Evaluation) are discussed. Connections for strut drag, turbulent wake state, and dynamic stall are included.
CONTENTS: GOVERNING EQUATIONS: BASIC CONSERVATION LAWS, FLOW KINEMATICS, SPECIAL FORMS OF THE GOVERNING EQUATIONS.IDEAL-FLUID FLOW: TWO-DIMENSIONAL POTENTIAL FLOWS, THREE-DIMENSIONAL POTENTIAL FLOWS, SURFACE WAVES.VISCOUS FLOWS OF INCOMPRESSIBLE FLUIDS: EXACT SOLUTIONS, LAW-REYNOLDS-NUMBER SOLUTIONS, BOUNDARY LAYERS.COMPRESSIBLE FLOW OF INVISCID FLUIDS: SHOCK WAVES, ONE-DIMENSIONAL FLOWS, MULTI-DIMENSIONAL FLOWS.
The effects of curvilinear flow on Darrieus turbine blade aerodynamics are described. Analysis shows that these effects can have a sizeable impact on performance for blades of large chord. Experimental data are presented which verify this forecast. Unusually large boundary-layer radial pressure gradients and virtually altered camber and incidence are identified as causal phenomena. Conformal mapping techniques are used to transform geometric airfoils in curved flow to their virtual equivalents in rectilinear flow. it is argued that flow curvature is an important determinant of Darrieus turbine blade aerodynamic efficiency and that its proper consideration will yield performance improvements, even for blades of small chord.
An analysis is made of the flow in the horizontal plane of symmetry of a fast running vertical-axis wind turbine having a great number of straight, very narrow blades and a high height-diameter ratio. The analysis is rigorously valid for only very lightly loaded turbines in incompressible nonviscous flow, but approximations for heavier loading and corrections for viscous effects are derived. It is found that half of the flow retardation caused by the turbine takes place within the turbine itself. Thus blade incidence and aerodynamic load on the blades are much higher on the windward than on the leeward side of the turbine. The maximum value of the power coefficient in nonviscous flow for this type of turbine is 92% of the theoretical maximum for an ideal wind turbine. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
An aerodynamic analysis is made of two variants of the two-actuator-disk theory for modeling the Darrieus wind turbine. The double-multiple-streamtube model with constant and variable interference factors, including secondary effects, is examined for a Darrieus rotor. The influence of the secondary effects, namely, the blade geometry and profile type, the rotating tower, and the presence of struts and aerodynamic spoilers, is relatively significant, especially at high tip-speed ratios. Variation of the induced velocity as a function of the aximuthal angle allows a more accurate calculation of the aerodynamic loads on the downwind zone of the rotor with respect to the assumed constant interference factors. The theoretical results were compared with available experimental data for the Magdalen Islands wind turbine and Sandia-type machines (straight-line/ circular-arc shape).
An elementary theory is developed for the power extraction capability of
a vertical axis wind turbine comprising a number of blades which operate
either at fixed or at continuously variable incidence. The performance
according to that theory is computed for some examples and applied to
estimate the economic feasibility of a turbine of 10 megawatt rating.
A preliminary aerodynamic performance prediction model has been
constructed for the Darrieus turbine using a vortex lattice method of
analysis. A series of experiments were conducted for the express purpose
of validating the analytical model. These experiments were conducted on
a series of two dimensional rotor configurations which were towed in a
large tank of water. The use of water as a working fluid was intended to
facilitate both flow visualization and the ability to measure
aerodynamic blade forces while allowing operation at sufficiently high
Reynolds numbers. The primary purpose of this research was to allow
reasonable predictions of aerodynamic blade forces and moments to be
made.
An analytical model is proposed for calculating the rotor performance
and aerodynamic blade forces for Darrieus wind turbines with curved
blades. The method of analysis uses a multiple-streamtube model, divided
into two parts: one modeling the upstream half-cycle of the rotor and
the other, the downstream half-cycle. The upwind and downwind components
of the induced velocities at each level of the rotor were obtained using
the principle of two actuator disks in tandem. Variation of the induced
velocities in the two parts of the rotor produces larger forces in the
upstream zone and smaller forces in the downstream zone. Comparisons of
the overall rotor performance with previous methods and field test data
show the important improvement obtained with the present model. The
calculations were made using the computer code CARDAA developed at IREQ.
The double-multiple streamtube model presented has two major advantages:
it requires a much shorter computer time than the three-dimensional
vortex model and is more accurate than multiple-streamtube model in
predicting the aerodynamic blade loads.
The phenomenon of flow curvature has been introduced into the
aerodynamic free-vortex model initially developed by Strickland for
vertical axis wind turbines with straight blades. By comparing the
theoretical results of the modified vortex model with the experimental
ones, it is deduced that the consideration of the flow curvature
improves the prediction of the transient aerodynamic forces but not that
of power coefficients. On the other hand, some modifications in the
application to vertical axis wind turbines of a semiempirical dynamic
stall method are tried, that can improve the prediction of instantaneous
aerodynamic forces as well as of power coefficients.
The aerodynamics of wind turbines is reviewed starting with effects of lift and drag on translating devices and proceeding through the performance aerodynamics of the horizontal-axis and vertical-axis machines currently in service. Horizontal-axis rotor aerodynamics is outlined and the performance limits are presented along with key assumptions and problem areas. The Darrieus rotor multiple streamtube analysis is developed and compared with fixed and free wake analyses for an idealized case.
A performance prediction model for the darrieus turbine. International symposium on wind energy systems
- Jh Strickland
Strickland JH. A performance prediction model for the darrieus turbine. International symposium on wind energy systems, Cambridge, UK, September 7–9, 1976. p. C3-39–54.
A theoretical and experimental investigation into the variable pitch vertical axis wind turbine
- Grylls W B Dale
- Sarre
- Pe
Grylls W, Dale B, Sarre PE. A theoretical and experimental investigation into the variable pitch vertical axis wind turbine. In: Proceedings of 2nd international symposium on wind energy systems, Amsterdam, October 3–6, 1978. p. E9-101–18.
1098 5.1. Momentum model
- Vawt.......................................................... Computational
Computational models for Darrieus-type straight-bladed VAWT................ 1098 5.1. Momentum model............................................. 1098
Wind: a hard-blowing history. The Environmental Magazine
- J Vogel
Vogel J. Wind: a hard-blowing history. The Environmental Magazine, Jan–Feb, 2005.
Wind Electricity Generation
- Itdg
ITDG. Wind Electricity Generation. Available at /http://www.itdg.orgS, 2006.
A theoretical and experimental study of the darrieus vertical axis wind turbine. School of Mechanical, Aeronautical & Production Engineering. Kingston Polytechnic. Research report
- Dj Sharpe
Sharpe DJ. A theoretical and experimental study of the darrieus vertical axis wind turbine. School of Mechanical, Aeronautical & Production Engineering. Kingston Polytechnic. Research report. October, 1977.
Aerodynamics of Cascades. Translated and revised by
- N Scholz
Scholz N. Aerodynamics of Cascades. Translated and revised by A. Kline. AGARD-AG-220, 1965.
Aerodynamics and design analysis of vertical axis darrieus wind turbines
- Ac Mandal
Mandal AC. Aerodynamics and design analysis of vertical axis darrieus wind turbines. PhD dissertation, Vrije Universiteit, Brussel, Belgium, 1986.
Summary of a vortex theory for the cyclogiro
- Hc Larsen
Larsen HC. Summary of a vortex theory for the cyclogiro. Proceedings of the second US national conferences on wind engineering research, Colorado state university, 1975. p. V8-1–3.
Evaluation of self-starting vertical axis wind turbines for stand-alone applications
- Bk Kirke
Kirke BK. Evaluation of self-starting vertical axis wind turbines for stand-alone applications. PhD thesis, Griffith University, Australia, 1998.
Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration
- Rj Muraca
- Stephens Mv
- Dagenhart
- Jr
Muraca RJ, Stephens MV, Dagenhart JR. Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration. NASA TMX-72662, USA, 1975.
Innovative wind machines: the theoretical performance of a vertical-axis wind turbine. In: Proceedings of the vertical-axis wind turbine technology workshop, Sandia laboratories
- Fanucci
- Jb
- Walter
Fanucci JB, Walter RE. Innovative wind machines: the theoretical performance of a vertical-axis wind turbine. In: Proceedings of the vertical-axis wind turbine technology workshop, Sandia laboratories, SAND 76-5586, iii-61-95, USA, 1976.
Development and evaluation of passive variable-pitch vertical axis wind turbines. Doctoral thesis, The University of New South Wales
- Nck Pawsey
Pawsey NCK. Development and evaluation of passive variable-pitch vertical axis wind turbines. Doctoral thesis, The University of New South Wales. November 2002.
Windmills: from Jiddah to Yorkshire
- P Lunde
Lunde P. Windmills: from Jiddah to Yorkshire. January/February. Vol. 31 (1), 1980.
Wind turbine design: with empasis on darrieus concept
- I Paraschivoiu
Paraschivoiu I. Wind turbine design: with empasis on darrieus concept. Montreal: Polytechnic International Press; 2002.