Scale Vertical Axis Wind Turbine Research Articles

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.

Experimental investigation on noise characteristics of small scale vertical axis wind turbines in urban environments

Noise pollution from wind turbines has been receiving significant attention with the rapid increase in global wind power installation, especially in urban environments where population density is high. Several countries tried to quantify the relation between wind turbine design characteristics and noise impact levels. To date, no quantitative results have been presented, while it is believed that the vertical axis wind turbine has advantages compared to horizontal axis wind turbines in certain applications. With the purpose to enhance understanding of noise pollution caused by vertical axis wind turbines in the urban environment, a systematic experimental test campaign in an anechoic wind tunnel was conducted. The results demonstrate that low-frequency noise increasingly affects humans when the wind speed increases. The blade-passing frequency is identified as a major parameter in the generation of low-frequency noise. More importantly, the noise pollution from various designs is discussed to analyze the impacts on humans and various animals. These designs are analyzed according to national standards from different countries. It is found that an optimal design of a vertical axis wind turbine is suitable for the urban environment with minimal noise impact.

Preliminary flow measurements of a small-scale, vertical axis wind turbine for the analysis of blockage influence in wind tunnels

Abstract The development of competitive lift vertical axis wind turbines (VAWTs) is yet a challenge in wind power research. New designs typically require wind tunnel testing before in site implementation. One of the major problems at the laboratory stage is the appearance of a significant flow blockage for small scale models, which affects the performance of the tested wind turbines and prevents the direct extrapolation of results to open field conditions without previous correction. Unfortunately, a suitable blockage correction for lift VAWTs has not been achieved yet, so more studies are needed in this research field to fill the gap. As part of preliminary work with this aim, a small scale VAWT prototype has been designed, constructed, and tested in a 1.15×1 m2 test section wind tunnel with a semi-closed chamber, featuring a blockage ratio of 0.37. Preliminary aerodynamic measurements were performed for different tip speed ratios on the downstream near wake using a special 3-hole pressure probe. Results show that the wake velocity profiles present a velocity increase around the prototype with a low velocity region in the windward quadrant of the turbine, indicating an important influence of the tunnel boundaries. These preliminary measurements have given an initial insight on the aerodynamic relationships between turbine performance and flow patterns. Additionally, they will help to devise an appropriate strategy for the following experiments, with the final objective of developing a blockage correction for small scaled VAWTs.

Numerical Study on the Aerodynamic Characteristics of the NACA 0018 Airfoil at Low Reynolds Number for Darrieus Wind Turbines Using the Transition SST Model

A symmetrical NACA 0018 airfoil is often used in such applications as small-to-medium scale vertical-axis wind turbines and aerial vehicles. A review of the literature indicates a large gap in experimental studies of this airfoil at low and moderate Reynolds numbers in the previous century. This gap has limited the potential development of classical turbulence models, which in this range of Reynolds numbers predict the lift coefficients with insufficiently accurate results in comparison to contemporary experimental studies. Therefore, this paper validates the aerodynamic performance of the NACA 0018 airfoil and the characteristics of the laminar separation bubble formed on its suction side using the standard uncalibrated four-equation Transition SST turbulence model and the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. A numerical study was conducted for the chord Reynolds number of 160,000, angles of attack between 0 and 11 degrees, as well as for the free-stream turbulence intensity of 0.05%. The calculated lift and drag coefficients, aerodynamic derivatives, as well as the location and length of the laminar bubble quite well agree with the results of experimental measurements taken from the literature for validation. A sensitivity study of the numerical model was performed in this paper to examine the effects of the time-step size, geometrical parameters and mesh distribution around the airfoil on the simulation results. The airfoil data sets obtained in this work using the Transition SST and the k-ω SST turbulence models were used in the improved double multiple streamtube (IDMS) to calculate aerodynamic blade loads of a vertical-axis wind turbine. The characteristics of the normal component of the aerodynamic blade load obtained by the Transition SST approach are much better suited to the experimental data compared to the k-ω SST turbulence model.

Kesan Kepaduan Rotor Terhadap Prestasi Kuasa Turbin Angin Paksi Menegak

Wind energy is one of the potential renewable energy sources and a great alternative to replace conventional power generation using coal and fossil fuel that heavily contribute to climate change. Recently, small scale vertical axis wind turbine (VAWT) has received growing interest as wind energy converter due to its suitability to be used in low wind speed area. Hence, this paper is intended to evaluate numerically the effect of solidity, by varying turbine diameter, on power performance of VAWT using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations was performed on a three-bladed H-type Darrieus rotor equipped with symmetrical NACA0018 blades. Performance evaluation on 3 turbine configurations with different diameter; i.e. 1.0 m, 0.6 m and 0.43 m was performed over a range of tip speed ratio, λ with an incoming velocity of 8.0 m/s. The simulation results clearly show that low solidity turbine performed better at high values of λ and has wider operating range while turbine with low solidity performed better at low λ and has better self-starting capability. The results lend ubstantially to our understanding of solidity effect on performance of VAWT in order to develop an ideal design of VAWT that can operate optimally in complex wind condition.

Kesan Kepaduan Rotor Terhadap Prestasi Kuasa Turbin Angin Paksi Menegak

Wind energy is one of the potential renewable energy sources and a great alternative to replace conventional power generation using coal and fossil fuel that heavily contribute to climate change. Recently, small scale vertical axis wind turbine (VAWT) has received growing interest as wind energy converter due to its suitability to be used in low wind speed area. Hence, this paper is intended to evaluate numerically the effect of solidity, by varying turbine diameter, on power performance of VAWT using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations was performed on a three-bladed H-type Darrieus rotor equipped with symmetrical NACA0018 blades. Performance evaluation on 3 turbine configurations with different diameter; i.e. 1.0 m, 0.6 m and 0.43 m were performed over a range of tip speed ratio, λ with an incoming velocity of 8.0 m/s. The simulation results clearly show that low solidity turbine performed better at high values of λ and has wider operating range while turbine with low solidity performed better at low λ and has better self-starting capability. The results lend substantially to our understanding of solidity effect on performance of VAWT in order to develop an ideal design of VAWT that can operate optimally in complex wind condition.

Performance and life cycle assessment of a small scale vertical axis wind turbine

Wind energy is one of the most popular renewable energy technologies that is considered indispensable in any low carbon energy mix. Small scale wind technologies that occupy less space and can supply electricity directly to their owners are thought to be more environmental friendly than the large turbines and therefore attract less criticism. Based on these, smaller scale renewables especially micro wind turbines should be the ideal solution but this might be just a leap of logic. The aim of this paper is to investigate whether it is worth developing smaller scale vertical axis wind turbines (VAWT) as a solution towards mitigating climate change. A real case of a H-Rotor 5 kW Darrieus vertical axis wind turbine in Poland is investigated for its performance using actual generation data. More importantly, a life cycle assessment (LCA) is undertaken, by compiling a very detailed life cycle inventory based on primary data and two scenarios were examined for the end-of-life treatment, including recycling and incineration . The performance assessment results show that the actual performance is very poor mainly due to the low wind speed. For this reason a series of hypothetical capacity factors were used to facilitate comparison with other studies. Using the CML impact assessment methodology, eleven environmental impact categories are assessed. The results show that the majority of the impacts are accredited to the supporting infrastructure - especially the mast and the foundations - rather than the turbine itself, which in the case of the Global Warming Potential (GWP) accounts for only 30%. Although the specific VAWT cannot achieve a generation that could reduce the environmental impacts to the level of the existing wind energy in Poland, a feasible capacity factor of 1.4% could make the GWP lower than the average low voltage electricity mix in Poland. The environmental performance is very sensitive to the fluctuations of the capacity factor and recommendations are given for appropriate siting, recycling of the metals and integration of the turbine on existing building structure.

Review on the Evolution of Darrieus Vertical Axis Wind Turbine: Large Wind Turbines

The objective of the current review is to present the development of a large vertical axis wind turbine (VAWT) since its naissance to its current applications. The turbines are critically reviewed in terms of performance, blade configuration, tower design, and mode of failure. The early VAWTs mostly failed due to metal fatigue since the composites were not developed. Revisiting those configurations could yield insight into the future development of VAWT. The challenges faced by horizontal axis wind turbine (HAWT), especially in the megawatt capacity, renewed interest in large scale VAWT. VAWT provides a solution for some of the immediate challenges faced by HAWT in the offshore environment in terms of reliability, maintenance, and cost. The current rate of research and development on VAWT could lead to potential and economical alternatives for HAWT. The current summary on VAWT is envisioned to be an information hub about the growth of the Darrieus turbine from the kW capacity to megawatt scale.

Design and development of integrated savonius and darrieus small scale vertical axis wind turbine for power generation

The study focuses on the integration of the darrieus and savonius wind turbine to a vertical axis wind turbine for power generation. The material used for darrieus was fiber glass with three blades and diameter of 350 mm, and polyvinyl chloride (PVC) for the savonius with four blades and diameter of 100 mm. The evaluation was conducted using a controlled wind source to vary its linear wind velocity. The actual power generated was compared to the theoretical power generated to identify the efficiency of the system. With the lowest linear wind velocity of 2.63 meters per second, the actual power output of the system (combination of the darrieus and savonius power output) was 3.79 watts and the theoretical power output is 6.03 watt. This made the system to be 62.85% efficient with low wind velocity. With the highest wind velocity of 12.52 meters per second, the output of the system was 408.80 watts and the theoretical output is 650.61 watts. This made the system to be 62.83% efficient. In an overall performance of the system with varying linear wind velocity, the efficiency of the system is close to 63%.

Airfoil selection and computational study on the torque performance of 4-blade vertical axis wind turbine

This paper contains numerically simulated data for a 4-blade Darrieus rotor type vertical axis wind turbine (VAWT). NACA0012, NACA0015, NACA0018 and NACA0021 airfoil types were analysed for the tangential force they create at different angle of attack. Based on the maximum tangential force generated by the airfoil for one full revolution, an airfoil series is selected for designing the 4-blade VAWT in simulation bed using Solid Works and then it is meshed, and cell zones are created over it in ANSYS tool. Then CFD analysis is carried out for different rotational speeds. Considering the overall torque produced during one full revolution, optimal rotational speed is arrived at. Finally, this study is aimed to study the torque performance of 4-blade Darrieus rotor type VAWT. This study is useful for designing the small scale VAWT for meeting the low energy demands at the load centres itself.

A Computational and Experimental Study of a Small-Scale Flat-Shaped Vertical Axis Wind Turbine

This paper focuses on a computational and experimental study of flat-shaped turbine blades for a small scale Vertical Axis Wind Turbine (VAWT). In the computational analysis, a 2-Dimensional (2D) wind turbine model with three flat blades was designed using Ansys Flu-ent, which is computational fluid dynamics (CFD) software. The wind speed around the blades was simulated in a range of 3 m/s to 8 m/s. Velocity and pressure distributions of the airflow around the blades were then observed. Pressures acting on the blades surface were then averaged and used to estimate the angular speed of the wind turbine model using the principles of torque and moment of inertia. A small-scale prototype was designed, fabricated and tested to validate the simulation result. Testing results show that the wind turbine prototype can rotate with an average speed of 148.8 rpm when having a 3.27 m/s wind speed. At the similar wind speed, the simulation result has estimated the angular speed to be 119 rpm. The percentage difference of the angular speed is about 20%. .

Benchmark of a Novel Aero-Elastic Simulation Code for Small Scale VAWT Analysis

After almost 20 years of absence from research agendas, interest in the vertical axis wind turbine (VAWT) technology is presently increasing again, after the research stalled in the mid 90's in favor of horizontal axis wind turbines (HAWTs). However, due to the lack of research in past years, there are a significantly lower number of design and certification tools available, many of which are underdeveloped if compared to the corresponding tools for HAWTs. To partially fulfill this gap, a structural finite element analysis (FEA) model, based on the Open Source multiphysics library PROJECT::CHRONO, was recently integrated with the lifting line free vortex wake (LLFVW) method inside the Open Source wind turbine simulation code QBlade and validated against numerical and experimental data of the SANDIA 34 m rotor. In this work, some details about the newly implemented nonlinear structural model and its coupling to the aerodynamic solver are first given. Then, in a continuous effort to assess its accuracy, the code capabilities were here tested on a small-scale, fast-spinning (up to 450 rpm) VAWT. The study turbine is a helix shaped, 1 kW Darrieus turbine, for which other numerical analyses were available from a previous study, including the results coming from both a one-dimensional beam element model and a more sophisticated shell element model. The resulting data represented an excellent basis for comparison and validation of the new aero-elastic coupling in QBlade. Based on the structural and aerodynamic data of the study turbine, an aero-elastic model was then constructed. A purely aerodynamic comparison to experimental data and a blade element momentum (BEM) simulation represented the benchmark for QBlade aerodynamic performance. Then, a purely structural analysis was carried out and compared to the numerical results from the former. After the code validation, an aero-elastically coupled simulation of a rotor self-start has been performed to demonstrate the capabilities of the newly developed model to predict the highly nonlinear transient aerodynamic and structural rotor response.

Numerical investigations of the effect of rotating and non-rotating shaft on aerodynamic performance of small scale urban vertical axis wind turbines

The shaft is a very important part of small scale vertical axis wind turbines (VAWTs) being used in urban environments. The shedding vortices will be formed as wind passes around the shaft, the shedding vortices released by the shaft have a negative effect on the aerodynamic performance of the blades passing the wake of the wind shaft, and this will lead to lower power output of the wind turbine. The objective of this study is to explore the differences of the effect of the rotating and non-rotating shafts of VAWTs on the aerodynamic performance of small scale urban VAWTs. In addition, the effect of surface roughness on the performance of the rotating and non-rotating shaft wind turbines is also investigated. The dynamic analysis of the VAWT is carried out by the method of Computational Fluid Dynamics. The aerodynamic loads in the study are obtained by solving the two-dimensional (2D) unsteady Navier-Stokes equations with the Transition SST turbulence model. The results are validated with experimental results. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 3.9%, the power coefficient (Cp) of the rotating shaft wind turbine is 2.2% higher than that of the non-rotating shaft wind turbine. Increasing the shaft diameter-based Reynolds number (Res) will increase the Cp of rotating and non-rotating shaft wind turbines, when Res is 2.6 × 104 and the Cp of the non-rotating shaft wind turbine is 5.7% higher than that of the rotating shaft wind turbine. The Cp of the non-rotating and rotating shaft wind turbines is reduced by 6.9% and 6.3%, respectively, by increasing the turbulence intensity from 4% to 16%. The optimal power output occurs under the condition of the non-rotating shaft wind turbine, and the relative surface roughness (ks/ds) is 0.005, where it is observed that Cp increased by 2.1% in comparison to that of the smooth shaft wind turbine.

Investigations on the Effect of Radius Rotor in Combined Darrieus-Savonius Wind Turbine

Renewable sources of energy, abundant in availability, are needed to be exploited with adaptable technology. For wind energy, the wind turbine is very well adapted to generate electricity. Among the different typologies, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off-grid power generation at low wind speeds. The combined Darrieus-Savonius wind turbine is intended to enhance the performance of the Darrieus rotor in low speed. In combined turbine, the Savonius buckets are always attached at the rotor shaft and the Darrieus blades are installed far from the shaft which have arm attaching to the shaft. A simple combined turbine offers two rotors on the same shaft. The combined turbine that consists of two Darrieus and Savonius blades was tested in wind tunnel test section with constant wind velocity and its performance was assessed in terms of power and torque coefficients. The study gives the effect of the radius ratio between Savonius and Darrieus rotor on the performance of the turbine. The results show that there is a significant influence on the turbine performance if the radius ratio was changed.

CFD simulations of power coefficients for an innovative Darrieus style vertical axis wind turbine with auxiliary straight blades

The increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in renewable energy sources such as wind energy. Amongst the different typologies of wind generators, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, Computational Fluid Dynamic (CFD) simulations were performed in order to investigate the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds. The micro turbine under investigation is composed of three pairs of airfoils, consisting of a main and auxiliary blades with different chord lengths. The simulations were made using the open source finite volume based CFD toolbox OpenFOAM, considering different turbulence models and adopting a moving mesh approach for the turbine rotor. The simulated data were reported in terms of dimensionless power coefficients for dynamic performance analysis. The results from the simulations were compared to the data obtained from experiments on a scaled model of the same VAWT configuration, conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). From the proposed analysis, it was observed that the most suitable model for the simulation of the performances of the micro turbine under investigation is the one-equation Spalart-Allmaras, even if under the conditions analysed in the present work and for TSR values higher than 1.1, some discrepancies between numerical and experimental data can be observed.

Effect of airfoil and solidity on performance of small scale vertical axis wind turbine using three dimensional CFD model

This paper presents a study on the effect of solidity and airfoil profile on the performance of Vertical Axis Wind Turbines (VAWTs). A 1.1 kW commercially viable Darrieus VAWT was studied using ANSYS Fluent. Four different airfoils – NACA 0012, NACA 0015, NACA 0030 and AIR 001 – were considered in the analysis. The tip speed ratios (λ) were varied from 1 to 2.5 with an incoming wind velocity of 10 m/s. It was observed that NACA 0030 performed better at lower values of λ due to long duration of attached flow; while NACA 0012 performed better at λ > 1.8 with a wider range of λ. The shed vortex dissipates much faster for thinner airfoils than for thicker airfoils at higher values of λ. Two bladed VAWTs generated more power than the three bladed turbines. This indicated that turbines with lower solidity perform better at high λ.

Characterization of a new open jet wind tunnel to optimize and test vertical axis wind turbines

Based on the increasing interest in urban environmental technologies, the study of small scale vertical axis wind turbines shows motivating challenges. In this paper, we present the characteristics and potentials of a new open jet wind tunnel. It has a nozzle exit area of 1.5 × 1.5 m2, and it can be operated with exit velocities from 3 m/s to 17 m/s. The characterization of the flow has been carried out with calibrated pitot tubes, cup anemometers, and hot wire anemometers. Two different configurations of the test area, with and without a ceiling, are considered. Measurements in the range of available exit velocities show that the cross section, where the velocity and turbulence intensities show an acceptable level of uniformity, has an area of 0.8 × 0.8 m2 and a streamwise dimension of 2 m from the nozzle exit of the tunnel. In this working section, the maximum turbulence intensity is 4%. The detailed characterization of the flow carried out indicates that the wind tunnel can be used to test small scale models of wind turbines.

Design, construction and study of small scale vertical axis wind turbine based on a magnetically levitated axial flux permanent magnet generator

A small scale vertical axis wind turbine (VAWT) with axial flux permanent magnet (AFPM) generator is designed and the magnetic levitation method is used to increase the efficiency of this type of wind turbine. Magnetic levitation is inserted by using rare earth permanent magnets, the repelling force of magnets are used to suspend the rotating part of both the turbine and generator. Moreover, this design of simple generator which can easily drive without a geared mechanism, lessen cost and the complexity of the system by reducing the quantity of driving components. Three phase output is obtained from the designed generator which is converted into direct current through a three-phase rectifier to charge the batteries. The performance of proposed prototype is also tested experimentally. From the results it is found that the designed wind turbine performs optimally and efficiently as predicted by the developed design process.

Wind tunnel testing of scaled models of a newly developed Darrieus-style vertical axis wind turbine with auxiliary straight blades

Renewable sources of energy, needed because of the increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in wind energy. Among the different typologies, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, wind tunnel investigations about the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds, has been made on scaled models. The micro turbine under investigation consists of three pairs of airfoils. Each pair consists of a main and auxiliary airfoil with different chord lengths. A standard Darrieus configuration, consisting of three single airfoils, was also tested for comparison. The experiments were conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). Measured data were reported in terms of dimensionless power and torque coefficients for dynamic performance analysis and static torque coefficient for static performance analysis. The adoption of auxiliary airfoils has demonstrated to give more dynamic torque at the lower wind speeds with respect to a standard Darrieus rotor, resulting in better performance for all the wind speeds considered. In terms of dynamic power coefficient, the standard Darrieus configuration presented slightly better performance for the highest wind speed analyzed. The proposed configuration showed also an higher value of static torque coefficient with respect to the standard Darrieus micro turbine, resulting in a better self-starting ability.

A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University

This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future.