Vertical Axis Wind Turbine Model Research Articles

Model Design of Helical Type Vertical Shaft Wind Turbine with Capacity of 5 W

A vertical axis wind turbine (VAWT) is a power generator that uses wind power to generate torque. The VAWT can be pointed in any direction, meaning it doesn't need to be pointed into the wind to generate power. Thus, there is potential for large power plants using VAWTs as their size can be significantly increased. However, there are also some drawbacks to the VAWT. VAWT has the characteristics of self-starting. But still, an additional power source is needed to start the turbine rotation until a certain rotation speed is reached or it must operate at high wind speeds. The main objective of our work is to create a 5 W VAWT model (helical type) to optimize self-starting of vertical axis wind turbines. The outline of this report is regarding the design of our VAWT model, which will have self-starting characteristics. To increase the self-starting status, our efforts are to optimize the type, dimensions and material of the turbine blades. We also optimized the rotor dimensions. As a result, a model helical three-blade turbine was built and tested. The blade turbine made of composites has been balanced with the rotor prior to testing. The test uses 2 fans with a speed of 3-5m/s, the test is carried out to obtain wind turbine performance data.

Experimental and numerical study of the wake deflections of scaled vertical axis wind turbine models

Wake steering of vertical axis wind turbines (VAWTs) is investigated experimentally and numerically via stereoscopic particle image velocimetry and Reynolds averaged Navier-Stokes simulations. Three different blade pitch angles (-10°, 0°, 10°) of straight H-type VAWTs are adopted to deflect and deform the wake. The experimental results confirm the efficacy of blade pitching on the wake steering, and validate the simulation for both moderate and significant wake deflections. The simulation is then extended to full-scale VAWTs, exploring the wake deflection effects on the power performance of VAWT arrays. The effects of inter-turbine distances and pitching configurations are considered. With the upwind VAWT deflecting the wake, the overall power coefficient is increased by 41%.

Numerical investigation of h-Darrieus wind turbine aerodynamics at different tip speed ratios

PurposeThe purpose of the paper is to predict the aerodynamic performance of a complete scale model H-Darrieus vertical axis wind turbine (VAWT) with end plates at different operating conditions. This paper aims at understanding the flow physics around a model VAWT for three different tip speed ratios corresponding to three different flow regimes.Design/methodology/approachThis study achieves a first three-dimensional hybrid lattice Boltzmann method/very large eddy simulation (LBM-VLES) model for a complete scaled model VAWT with end plates and mast using the solver PowerFLOW. The power curve predicted from the numerical simulations is compared with the experimental data collected at Erlangen University. This study highlights the complexity of the turbulent flow features that are seen at three different operational regimes of the turbine using instantaneous flow structures, mean velocity, pressure iso-contours, blade loading and skin friction plots.FindingsThe power curve predicted using the LBM-VLES approach and setup provides a good overall match with the experimental power curve, with the peak and drop after the operational point being captured. Variable turbulent flow structures are seen over the azimuthal revolution that depends on the tip speed ratio (TSR). Significant dynamic stall structures are seen in the upwind phase and at the end of the downwind phase of rotation in the deep stall regime. Strong blade wake interactions and turbulent flow structures are seen inside the rotor at higher TSRs.Research limitations/implicationsThe computational cost and time for such high-fidelity simulations using the LBM-VLES remains expensive. Each simulation requires around a week using supercomputing facilities. Further studies need to be performed to improve analytical VAWT models using inputs/calibration from high fidelity simulation databases. As a future work, the impact of turbulent and nonuniform inflow conditions that are more representative of a typical urban environment also needs to be investigated.Practical implicationsThe LBM methodology is shown to be a reliable approach for VAWT power prediction. Dynamic stall and blade wake interactions reduce the aerodynamic performance of a VAWT. An ideal operation close to the peak of the power curve should be favored based on the local wind resource, as this point exhibits a smoother variation of forces improving operational performance. The 3D flow features also exhibit a significant wake asymmetry that could impact the optimal layout of VAWT clusters to increase their power density. The present work also highlights the importance of 3D simulations of the complete model including the support structures such as end plates and mast.Social implicationsAccurate predictions of power performance for Darrieus VAWTs could help in better siting of wind turbines thus improving return of investment and reducing levelized cost of energy. It could promote the development of onsite electricity generation, especially for industrial sites/urban areas and renew interest for VAWT wind farms.Originality/valueA first high-fidelity simulation of a complete VAWT with end plates and supporting structures has been performed using the LBM approach and compared with experimental data. The 3D flow physics has been analyzed at different operating regimes of the turbine. These physical insights and prediction capabilities of this approach could be useful for commercial VAWT manufacturers.

Improving the self-starting and operating characteristics of vertical axis wind turbine by changing center distance in part of blades

Compared with the horizontal axis wind turbine (HAWT), the vertical axis wind turbine (VAWT) has the advantages of low noise operation and no wind yaw device. However, the poor self-starting performance of VAWT is one of key problems restricting its development. In order to improve the self-starting capability of VAWTs in urban wind areas, this paper proposed a VAWT model with multi-blade local variable radius. The main object of this study is to research the effect of reducing the partial blade radius on the self-starting performance and power coefficient of the VAWT. In this study, the partial blade radius of the VAWT models was reduced to 0.375, 0.5, and 0.625 times of the outer layer. The dynamic torques and velocity contours of the different models were researched by experiments and numerical simulations to analyze the reason why reducing the partial blade radius affects the power coefficient of the VAWT. The static torque and static pressure contours of different models were researched to compare the self-starting capability of the models. According to the results, the minimum static torque values of the three innovative VAWT models were increased by 0.1, 1.8, and 2.8 times, respectively, compared to the traditional VAWT with only the outer layer. Furthermore, the power coefficients of three models were increased for tip speed ratios (TSR) less than 2.2. Therefore, the new models can improve the self-starting capability of VAWTs, and the higher power coefficients at low TSRs make them more advantageous for applications in urban buildings and low wind speed areas.

The Impact of Ice Formation on Vertical Axis Wind Turbine Performance and Aerodynamics

This study investigated the impact of ice formation on the performance and aerodynamics of a vertical axis wind turbine (VAWT). This is an area that is becoming more prevalent as VAWTs are installed alongside horizontal axis wind turbines (HAWTs) in high altitude areas with cold and wet climates where ice is likely to form. Computational fluid dynamics (CFD) simulations were performed on a VAWT without icing in Ansys to understand its performance before introducing ice shapes obtained through the LewInt ice accretion software and repeating simulations in Ansys. These simulations were verified by performing a wind tunnel experiment on a scale VAWT model with and without 3D printed ice shapes attached to the blades. The clean blade simulations found that wind speed had little impact on the performance, while reducing the blade scale severely reduced performance. The ice formation simulations found that increasing the icing time or liquid water content (LWC) led to increased ice thickness. Additionally, glaze ice and rime ice conditions were investigated, and it was found that rime ice conditions that occur in lower temperatures caused more ice to form. The simulations with the attached ice shapes found a maximum reduction in performance of 40%, and the experiments found that the ice shapes made the VAWT unable to produce power.

Unscented Kalman filter-based blade-effective wind speed estimation for a vertical-axis wind turbine

On-shore horizontal-axis wind turbines (HAWTs) provide a cost-effective solution for low carbon electricity generation. However, public acceptance is still a problem. A possible alternative to a HAWT is a vertical-axis wind turbine (VAWT), which is more visually appealing and less noisy. Furthermore, the inherent omni-directionality of VAWTs makes them suitable for installation in urban environments where the turbulence levels are high, and the wind direction variations are significant. However, the variation with the azimuth angle of the blade-effective wind speed and the angle of attack makes VAWT performance difficult to predict. This study proposes a wind speed estimator for a VAWT to address this challenge and to exploit knowledge of the blade-effective wind speed for load reduction control strategies. An Unscented Kalman Filter is used to solve the blade-effective wind speed estimation problem and is applied to a realistic 1.5 m two-bladed H-Darrieus VAWT model, for which the aerodynamic characteristics are determined using an actuator cylinder model. The system performance is evaluated using different wind speed variation scenarios. Overall, good agreement between the reference and estimated blade-effective wind speed is found both in terms of trend and absolute values.

Numerical Investigation of the Power Performance of the Vertical-Axis Wind Turbine with Endplates

An H-rotor vertical axis wind turbine (VAWTs) can operate independently in any wind direction, making it aerodynamically efficient and suitable to harness wind energy in low wind speed areas. The aerodynamic efficiency of VAWTs is highly dependent on the blade geometry, especially the blade tip. Tip vortices produced at the blade tips can negatively affect the VAWT’s aerodynamic efficiency. Adding endplates to the blade tips can minimize the effects of tip vortices on VAWTs. In this paper, several endplate designs are used to evaluate the effectiveness in improving the power coefficient, Cp of a VAWT at three different tip speed ratios (TSRs) using three-dimensional computational fluid dynamics (3D CFD) simulation. The power coefficients of VAWTs with endplates are compared with the baseline model with the same geometrical parameters where the baseline VAWT model is based on the experimental model from the literature. Since the focus of this study is on the blade tip design, a simplified 3D VAWT model is used where the supporting shaft and arms of the VAWT are excluded to reduce the needed computational capacity. Among the various endplate designs used in this study, the semi-circular inward endplate (ED3) with a diameter equivalent to 1.2 blade chord length showed the best improvement in the Cp which is by 7.45%, and 5.79% for at the TSRs of 2.19 and 2.58, respectively. The pressure difference on both sides of the blade was also examined. The results revealed that the endplate can prevent the flow from bypassing the blade tip, hence, preventing the occurrence of tip vortices while improving the aerodynamic efficiency near the blade tip, ultimately, improving the overall Cp of a VAWT.

Univariate analysis of scaling effects on the aerodynamics of vertical axis wind turbines based on high-resolution numerical simulations: The Reynolds number effects

The scale effect on aerodynamics determines, to some extent, the development trend and limitation of large vertical axis wind turbines (VAWTs). Among many factors, Reynolds number is an important one affected by such effects and is therefore often used as a criterion to distinguish between small-scale and large-scale wind turbines. In this paper, a dimensionless analysis was first conducted, and the results showed that scaling the wind turbine as a whole only led to a change in Reynolds number, while other key factors remained constant. Based on such understanding, a univariate analysis was then carried out to investigate the effect of Reynolds number variation due to scaling effects on the aerodynamic performance of VAWTs. In the study, a series of high-resolution numerical simulations were performed on a simplified single-bladed VAWT model. By directly scaling the model size, the operating Reynolds number of the wind turbine was made to vary in the range of 1×104 to 5×106 at a specific solidity and reduced frequency. The analysis shows that over the range of Reynolds number investigated, as the size of the wind turbine model increases, the flow separation nearby the blade decreases, the strength of the dynamic stall vortex becomes weaker, and the power coefficient of wind energy extraction generally tends to increase, thus indicating that large-scale wind turbine is generally beneficial aerodynamically. Specifically, when VAWTs operate in a Reynolds number ranging from 5×104 to 5×105, the power coefficient increases significantly as the size of wind turbine increases, while when operating in the range of 5×105∼5×106, the power coefficient still tends to increase, but in a decreasing increment ratio.

Computational design & analysis of vertical axis wind turbine

India's energy demand is rising in order to meet the country's current economic development ambitions. The provision of growing amounts of energy is a necessary condition for a country's economic growth. India is heading toward a trend of generating power from renewable resources, owing to the maturity of technological innovations and the pressing need to preserve a healthy environment at a fair cost. Wind energy sector has increased from a fringe activity to a huge multinational business thanks to its safer and environmentally friendly properties. This project aims at utilizing wind energy in an effective approach to get the maximum electric output, which can be implemented in urban areas on the ground, on highways etc. In the present work, vertical axis wind turbine is designed numerically. The blades used are twisted and are connected to the shaft. Analyses are carried out on two vertical axis wind turbine profiles at different wind speeds. Velocity, pressure, and torque characteristics are obtained and compared between the two vertical axis wind turbine models.

Modal dynamics and flutter analysis of floating offshore vertical axis wind turbines

Floating platforms provide vertical axis wind turbines (VAWTs) significant advantages over offshore horizontal axis wind turbines, which has led to increased research interest in offshore VAWT technology. This paper examines dynamic stability of floating VAWTs and presents structural dynamic and aero-elastic flutter analysis of utility-scale 5 MW floating VAWTs by coupling a rotor finite element model with a linearized model for the floating system. The coupled floating VAWT model is utilized to study the effects of tower height, number of blades, blade tapering scheme, and impacts of the floating platform on modal properties and flutter. The study provides important new results and guidance to floating VAWT designers: (1) tower height increase leads to lower tower frequencies more prone to resonance, (2) by moving from land-based foundations to a floating TLP foundation, tower-mode frequency is increased significantly (by 49%–68%) which mitigates resonance and increases the flutter RPM (154% increase), (3) increasing the number of blades reduces the tower mode frequencies for both land-based and floating configuration, and (4) blade chord tapering can have a significant impact on increasing the tower mode flutter RPM. Further, analysis of low-frequency rigid body modes shows a safe, higher flutter RPM relative to the operating RPM.

Effects of Damaged Rotor on Wake Dynamics of Vertical Axis Wind Turbines

Vertical Axis Wind Turbines (VAWTs) are omnidirectional turbomachines commonly used in rural areas for small-to-medium-scale power generation. The complex flow observed in the wake region of VAWTs is affected by a number of factors, such as rotor blades design. A damaged rotor significantly alters the flow field in the wake region of the VAWT, degrading its power generation capability. Published literature on damaged wind turbine blades is severely limited to torque signal analysis and basic flow field description in the wake region. In this study, detailed numerical investigations have been carried out to establish and quantify the relationship between damaged rotor and the wake dynamics of a VAWT. Time-based Computational Fluid Dynamics analyses have been performed on two VAWT models, one undamaged and the other with a missing rotor blade. Proper Orthogonal Decomposition has been used to extract the energy content and temporal coefficients of the various flow patterns associated with the wake region. The results indicate that the first pressure-based flow mode contains 99% of the energy and provides a functional basis for accurate reconstruction of the wake. It is envisaged that this study will aid the development of novel machine learning algorithms for rotor damage detection in wind farms.

CFD modelling and prototype testing of a Vertical Axis Wind Turbines in planetary cluster formation

This study aims to improve the applicability of Vertical Axis Wind Turbines (VAWTs) by investigating their feasibility in a novel planetary cluster configuration by observing its effect on efficiency and overall power density. Computational Fluid Dynamics (CFD) simulations were carried out using a two-dimensional vertical axis wind turbine model in ANSYS Fluent 2020 R1. This software was used to solve the transient k-omega (SST) turbulence model. For the isolated VAWT the wind velocity, rotor radius and tip speed ratio were varied to find the optimum turbine performance at a given parameter. A peak efficiency of 34.05% was attained and equivalent configuration used as the “sun” turbine in the novel planetary design. The parametric study of the novel set up was conducted with the PCD (Pitch Circle Diameter) and oblique angular (ϕ) position of the smaller “planet” turbines being varied in relation to the “sun” turbine. The planetary system was then evaluated in terms of efficiency improvements against the isolated VAWT model. Use of the “planet” turbines resulted in power extraction from the free stream which in turn creates varying wind velocities and improved the efficiency of the central “sun” turbine. The optimal PCD was found to be 5D (3.75 m) and the optimum angular position of the “planets” was discovered at 30°. Ultimately this gave a percentage increase of 1.01% from 33.04% to 34.05% when comparing the “sun” turbine of the planetary arrangement to the optimum isolated respectively. An average improvement of 4% over the range of tip speed ratios (TSR) was found. Lastly, a scale model of the isolated VAWT was constructed and tested through wind tunnel experiments. The characteristic curve correlation was found between the CFD and experimental results which allowed validation of the CFD models.

Autonomous Fuzzy Controller Design for the Utilization of Hybrid PV-Wind Energy Resources in Demand Side Management Environment

This work describes an optimum utilization of hybrid photovoltaic (PV)—wind energy for residential buildings on its occurrence with a newly proposed autonomous fuzzy controller (AuFuCo). In this regard, a virtual model of a vertical axis wind turbine (VAWT) and PV system (each rated at 2 kW) are constructed in a MATLAB Simulink environment. An autonomous fuzzy inference system is applied to model primary units of the controller such as load forecasting (LF), grid power selection (GPS) switch, renewable energy management system (REMS), and fuzzy load switch (FLS). The residential load consumption pattern (4 kW of connected load) is allowed to consume energy from the grid and hybrid resources located at the demand side and classified as base, priority, short-term, and schedulable loads. The simulation results identify that the proposed controller manages the demand side management (DSM) techniques for peak load shifting and valley filling effectively with renewable sources. Also, energy costs and savings for the home environment are evaluated using the proposed controller. Further, the energy conservation technique is studied by increasing renewable conversion efficiency (18% to 23% for PV and 35% to 45% for the VAWT model), which reduces the spending of 0.5% in energy cost and a 1.25% reduction in grid demand for 24-time units/day of the simulation study. Additionally, the proposed controller is adapted for computing energy cost (considering the same load pattern) for future demand, and it is exposed that the PV-wind energy cost reduced to 6.9% but 30.6% increase of coal energy cost due to its rise in the Indian energy market by 2030.

Formulation, Validation, and Application of a Novel 3D BEM Tool for Vertical Axis Wind Turbines of General Shape and Size

Low order models based on the Blade Element Momentum (BEM) theory exhibit modeling issues in the performance prediction of Vertical Axis Wind Turbines (VAWT) compared to Computational Fluid Dynamics, despite the widespread engineering practice of such methods. The present study shows that the capability of BEM codes applied to VAWTs can be greatly improved by implementing a novel three-dimensional set of high-order corrections and demonstrates this by comparing the BEM predictions against wind-tunnel experiments conducted on three small-scale VAWT models featuring different rotor design (H-shaped and Troposkein), blade profile (NACA0021 and DU-06-W200), and Reynolds number (from 0.8×105 to 2.5×105). Though based on the conventional Double Multiple Stream Tube (DMST) model, the here-presented in-house BEM code incorporates several two-dimensional and three-dimensional corrections including: accurate extended polar data, flow curvature, dynamic stall, a spanwise-distributed formulation of the tip losses, a fully 3D approach in the modeling of rotors featuring general shape (such as but not only, the Troposkein one), and accounting for the passive effects of supporting struts and pole. The detailed comparison with experimental data of the same models, tested in the large-scale wind tunnel of the Politecnico di Milano, suggests the very good predictive capability of the code in terms of power exchange, torque coefficient, and loads, on both time-mean and time-resolved basis. The peculiar formulation of the code allows including in a straightforward way the usual spanwise non-uniformity of the incoming wind and the effects of skew, thus allowing predicting the turbine operation in a realistic open-field in presence of the environmental boundary layer. A systematic study on the operation of VAWTs in multiple environments, such as in coastal regions or off-shore, and highlighting the sensitivity of VAWT performance to blade profile selection, rotor shape and size, wind shear, and rotor tilt concludes the paper.

Solidity effects on the performance of vertical-axis wind turbines

Abstract The variety of configurations for vertical-axis wind turbines (VAWTs) make the development of universal scaling relationships for even basic performance parameters difficult. Rotor geometry changes can be characterized using the concept of solidity, defined as the ratio of solid rotor area to the swept area. However, few studies have explored the effect of this parameter at full-scale conditions due to the challenge of matching both the non-dimensional rotational rate (or tip speed ratio) and scale (or Reynolds number) in conventional wind tunnels. In this study, experiments were conducted on a VAWT model using a specialized compressed-air wind tunnel where the density can be increased to over 200 times atmospheric air. The number of blades on the model was altered to explore how solidity affects performance while keeping other geometric parameters, such as the ratio of blade chord to rotor radius, the same. These data were collected at conditions relevant to the field-scale VAWT but in the controlled environment of the lab. For the three highest solidity rotors (using the most blades), performance was found to depend similarly on the Reynolds number, despite changes in rotational effects. This result has direct implications for the modelling and design of high-solidity field-scale VAWTs.

A Study on Relationship among Blade Camber Direction and Pitch Angle and Performance of a Small Straight-Blade Darrieus Wind Turbine by Using Scale Test Model and Gurney Flap

Straight-blade Darrieus vertical axis wind turbines are used as medium and small size wind turbine because of higher power output in vertical axis wind turbine (VAWT). In our previous study, the relationship between the performance and Reynolds number based on airfoil chord length had been investigated by using small-scale test models of lift-type VAWT, and the results showed that the performance of tested wind turbine models with small diameter was clearly lower than that of the large-scale field test machine, and its performance also varies significantly with the blade pitch angle. In this study, we focused on the performance of a small-scale straight-blade Darrieus VAWT, the relationship among the blade airfoil camber direction and the pitch angle, and the performance of the small-scale VAWT was examined experimentally by using a small-scale VAWT test model with Gurney flap which was a small flat plate. Gurney flaps with its height h, as a ratio to the blade chord length c, h/c = 0.036 to 0.055, were attached to the blades of the VAWT test model, in addition, the attaching direction of the Gurney flap on the blade was examined for both inward and outward of the rotor, and the pitch angle was also examined for a range of −5 to 10 degrees. These results are discussed comparing with the result of the VAWT without Gurney flap and considering the numerical results for the single blade with/without the Gurney flap. The results showed that the performance of the tested VAWT was reversed between the inward and outward Gurney flaps around a pitch angle of 10 degrees. That is, the inward Gurney flap was superior at a pitch angle of less than 10 degrees, while the outward Gurney flap was effective at a pitch angle of more than 10 degrees. Furthermore, for the tested small-scale VAWT model, the optimum pitch angle was about 5 degrees, and the inward and shorter Gurney flap showed higher power performance of the VAWT under this pitch angle condition.

An experimental investigation into performance characteristics of H-shaped and Savonius-type VAWT rotors

The effects of flow regime and rotor configuration strongly influence the power performance of vertical axis wind turbines (VAWTs). Yet, there exits few experimental investigations from literature that have been carried to explain this effect. This could be attributable to huge wind tunneling cost requirement and an array of design skills required including time constrains. The balance between cost and power performance has limited development of VAWTs towards utility scale type. In this paper therefore, we seek to investigate in detail the performance characteristics of vertical axis wind rotors in a wind tunnel environment. The H-Darrieus and Savonius-type VAWT configurations have been utilized to carry out the investigation. A systematic analysis of effect of blade number, rotor configuration, and flow regime including comparison of the two configurations was presented to predict the power performance using a rotary sensor. Results revealed a significant impact of flow field regime on power performance of the VAWT models, with the Savonius-type rotor attaining lower power coefficient (CP) than the Darrieus-type rotor across all the tested wind speeds. In addition, increase in number of blades for Darrieus-type rotor revealed narrower negative CP band that decreased with increase in wind speeds. In both configurations, the CP decreased at low tip speed ratios while an increase in CP was revealed at high tip speed ratios. The understanding gained from the results could be useful to the VAWT research community, and the findings can be extended to the design of wind turbines for mini-grid and utility scale applications.

Numerical Analysis of Exhaust Air Energy Extractor for Cooling Tower Applications

Over the years, the need of renewable energy has been accelerated to minimise the reliance on using the fast depleting fossil fuel. Research on wind turbines to harness wind power is widely increasing especially with the progression of vertical axis wind turbines (VAWT) for the locations, where conventional horizontal axis wind turbines are not effective. The ability to provide renewable energy by generating efficient power is vital in combatting climate change due to increase in global energy demand thus, leading to this present study of extracting wind energy from a cooling tower. In this paper, a three dimensional numerical investigation has been conducted on the straight bladed Darrieus type VAWTs with S1046 airfoils. The implicit unsteady Reynolds-Averaged Navier-Stokes equations are solved using shear stress transport k-? turbulent model. The VAWT model is placed at the outlet of the cooling tower to calculate power output with an aspect ratio of 0.88. The results show that a maximum power coefficient of 0.36 is obtained at a tip speed ratio of 3.0.

Study of Pivot Panel Mechanism on the Self Start-Ability of a Darrieus Wind Turbine

In South East Asia countries such Malaysia, wind turbine is generally not suitable to be used in large scale to generate electricity due to inconsistent wind speed and suitable land site availability. However, a small scale application is of preference as the wind speed in the region lies within the low speed range of approximately 2-5 ms−1 with intermittent highs up to 8 ms−1. The performance of Vertical Axis Wind Turbines (VAWTs) is known to be better compared to Horizontal Axis Wind Turbines (HAWTs) in urban conditions due to its omnidirectionality, which allows it to operate in fluctuating turbulent wind conditions. However, the major drawback of VAWTs is the inability to self-start under low wind speed conditions. Hence, the objective of this work is to investigate the Pivoting Panel Mechanism (PPM) which aims to assist VAWT models to self-start at low wind speed condition. Three sets of PPM width configurations (70mm, 80mm, 90mm) are used to study the effect of increasing the pivot panel surface area on the VAWT performance. Performance test showed that the PPM model improved the power coefficient values at the tip wind speed range of TSR<0.75 (PPM 70mm>80mm>90mm). Further investigation revealed that the larger PPM surface area (90mm) was able to assist the VAWT model to achieve a shorter RPM response time at wind speed of v = 2.5ms−1 and 2.9ms−1. These findings have considerable implications for future researches for the optimization of PPM design parameters and its adaptations in VAWT turbine design.

A new dynamic inflow model for vertical‐axis wind turbines

AbstractThis paper presents a new dynamic inflow model for vertical‐axis wind turbines (VAWTs). The model uses the principle of Duhamel's integral. The indicial function of the inflow‐ and crossflow‐induction required to apply Duhamel's integral is represented by an exponential function depending on the thrust coefficient and the azimuthal position. The parameters of this approximation are calibrated using a free wake vortex model. The model is compared with the results of a vortex model and higher fidelity computational fluid dynamic (CFD) simulations for the response of an actuator cylinder to a step input of the thrust and to a cyclic thrust. It is found that the discrepancies of the dynamic inflow model increase with increasing reduced frequency and baseline thrust. However, the deviations remain small. Analysing the application of a finite‐bladed floating VAWT with non‐uniform loading and validating it against actuator line CFD results that intrinsically include dynamic inflow shows that the new dynamic inflow model significantly outperforms the Larsen and Madsen model (which is the current standard in fully coupled VAWT models) and enhances the modelling of VAWTs.