Small Vertical Axis Wind Turbine Research Articles

Numerical model for noise reduction of small vertical-axis wind turbines

Abstract. Small vertical-axis wind turbines are a promising solution for affordable and clean energy, but their noise emissions present a challenge to public acceptance. Numerous blade designs have been aimed at reducing noise but often come with a decrease in wind turbine aerodynamic efficiency. In this study, the acoustic power and torque of a 5 kW vertical-axis wind turbine (VAWT) were simulated by using different mesh sizes and turbulence models. The simulated torque and noise of the turbine have significant sensitivity to the mesh size, so suitable mesh sizes were determined for the near-wall and rotating regions that can be used as a design reference for future turbines with similar operating conditions. The selection of the turbulence model was found to affect the predicted torque by about 10 % and the predicted tip noise by about 2 dB. The selected mesh size and turbulence model were then applied to simulating the effectiveness of three common noise mitigation techniques: a mask, deflector, and wall roughness. The results showed that deflectors are suitable for noise reduction of small VAWTs. This paper provides valuable information on simulating noise propagation from small VAWTs and the optimal noise reduction techniques.

Numerical Investigation of Aerodynamic Performance and Structural Analysis of a 3D J-Shaped Based Small-Scale Vertical Axis Wind Turbine

Small vertical axis wind turbines (VAWTs) are often considered suitable for use in urban areas due to their compact design. However, they are also well known to offer poor performance at low wind speeds, which is a common situation in such environments. An optimised 3D J-shaped VAWT was designed from standard NACA 0015 blades and analysed numerically through computational fluid dynamics (CFD). A finite element analysis (FEA) was also carried out to ensure the model’s structural integrity. Optimal results were obtained with aluminium alloy hollow blades and stainless-steel struts with X-shaped beams, with internal ribs. Numerical results showed that the J-shaped VAWT achieved an 18.34% higher moment coefficient compared to a NACA 0015-based VAWT, indicating better self-starting abilities.

CFD Prediction for Wind Power Generation by a Small Vertical Axis Wind Turbine: A Case Study for a University Campus

The accuracy of wind power generation predicted by computational fluid dynamics (CFD) simulations combined with meteorological wind data was validated based on comparisons with directly measured data for a small vertical axis wind turbine system installed on a university campus. The CFD simulations were performed in accordance with established guidelines and frameworks for the prediction of urban wind environments. At the rooftop location, where small wind turbines are typically installed, the deviations in wind velocity from the measurements are quite large. However, in the present study, the prediction accuracy for the wind turbine site, which was 4 m above the ground, was acceptable. The total power generation estimated using the assumed power curve based on the rated output of the turbine was 56% larger than that directly measured by the power generator. However, using the power curves obtained from the measurements, the total power generation could be predicted with a high degree of accuracy and with an error of approximately 3%. It is suggested that not only the accuracy of the wind velocity but also that of the power curve is very important because they are directly related to that of the predicted power generation.

Experimental and simulation study on a rooftop vertical-axis wind turbine

Abstract In this study, a small vertical-axis wind turbine (VAWT) was successfully designed and tested to produce electrical energy using renewable wind energy after being installed on the roof of buildings. The VAWT was constructed according to the existing wind source in the Tabuk region in Saudi Arabia. The use of VAWT on roofs is a sustainable solution for producing clean electricity and contributing to a portion of the local electricity consumption. A rooftop wind turbine test was performed to determine the behavior and output of a VAWT under non-constant wind speeds under natural conditions. To verify the resistance of the shear stress and pressure, a computational fluid dynamics (CFD) simulation on the airfoil was conducted. The experimental test results showed that the VAWT can reach its rated power at 9 m/s. The minimum wind speed needed for power production was 3 m/s. The maximum power coefficient obtained during testing was approximately 0.45 at a tip speed ratio of around 1.94. The simulation mesh is constructed with Ansys mesh. Two dimensional (2-D) mapped face meshing, fine, high smoothing mesh was constructed with 50 division numbers and a bias factor of about 150. The grid with 15,000 cells generated the same results as the higher number of cell grids. The simulation equivalent force was about 2.8 N for a single blade, such as 8.5 N in total, which presents an error of about 3%. The CFD simulation and experimental tests on existing forces confirm that the VAWT structure’s resistance can be guaranteed at high wind speeds.

Performance of Axial Generator for a Small Vertical Axis Wind Turbine

Performance of Axial Generator for a Small Vertical Axis Wind Turbine

Electric vehicle battery charging framework using artificial intelligence modeling of a small wind turbine based on experimental characterization

The objective of this paper is to develop a generic electric vehicle battery charging framework using wind energy as the direct energy source. A robust model for a small vertical axis wind turbine based on an artificial neural network algorithm is used for predicting its performance over a wide range of operating conditions. The proposed framework can be implemented at any location worldwide where full prediction of the wind signature is perfectly obtained. In this paper, a small vertical axis wind turbine has been experimentally characterized at different operating conditions, where measured data, output power, and torque have been used to build the model. Once the model has been developed, the model is inserted into the MATLAB/Simulink software tool to predict the charging performance of a battery for an electric vehicle. An rpm controller has been used to achieve the maximum generated power from the wind turbine across the day with various wind speeds. Hence, the generated power is fed to the EV battery charger to implement the constant current constant voltage charging protocol. The charging current reached the desired value in a settling time of 4.5 s, whatever the intermittency of the wind energy. The proposed application of wind energy to EV provides sufficient constant power supported by the utility grid.Graphical

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.

Fast online reinforcement learning control of small lift-driven vertical axis wind turbines with an active programmable four bar linkage mechanism

Maintaining high power generation for small lift-driven vertical axis wind turbines in a changing wind environment has not been well studied yet, due to the challenges inherited from the unpredictable turbulent flow-blade interaction and complex blade interferences. Herein, a fast online reinforcement learning pitch control using an active programmable four bar linkage mechanism is proposed, making it possible for turbines to quickly adapt to wind changes and maintain high power output in operation. We formulate the pitching mechanism using a drag-link configuration with a variable frame link length into an optimization problem and further solve it by the interior point algorithm under a wide range of tip speed ratios. Then, a parameter explorative policy gradient reinforcement learning method is designed for the turbine to adaptively tune the frame link length. Since the design significantly reduces the number of parameters needed to depict a whole pitch trajectory, the proposed online learning process can converge quickly, making it capable of handling complex wind conditions in an urban environment. The transient behavior overlooked in much of the literature is also studied. Comparisons to two benchmarks have demonstrated that our proposed system has a superior performance.

Wind energy potential assessment of selected locations at two major cities in the Dominican Republic, toward energy matrix decarbonization, with resilience approach

Climate changes pose big challenges to scientists, engineers, and decision makers to provide sustainable energy services to cities. Innovative energy solutions are required to fulfill the growing energy demand in a sustainable and resilient way, especially in developing countries. The implementation of small-scale energy systems integrated in urban sites such as wind and solar are a promising technological approach, in this direction urban wind energy can be a suitable resource. A preliminary assessment of urban wind energy is needed by turbine developers, investors, and decision makers. The present work aims to present an assessment of wind energy potential of selected locations at two major cities in the Dominican Republic, for this purpose was developed a robust framework to provide an assessment of the wind energy potential in a tropical area for roof-mounted turbines. The framework is based on six main steps: (1) site selection, (2) resource prospecting/analysis, (3) turbine selection, (4) estimation of currently produced energy, (5) environmental evaluation and (6) resilience assessment. The resilience metrics have been adopted to novel assess three scenarios of resilience in tropical areas. The methodology was applied in San Cristóbal and Santo Domingo, two major cities in the Dominican Republic. The urban wind energy potential was assessed considering the installation of 1,075 small two-blade Darrieus H-type Vertical Axis Wind Turbines (VAWTs) on the roofs of 275 high-rise buildings, with annual energy production of 317 MWh, represented a potential CO2 emissions reduction of 197 Ton/yr.

Start-up considerations for a small vertical-axis wind turbine for direct wind-to-heat applications

Renewable production of space and water heating is needed for a sustainable society. The rotating shaft of a vertical-axis wind turbine can be equipped with a paddle wheel-style mixing impeller to directly heat a fluid by agitating or stirring the fluid. A Darrieus vertical-axis wind turbine, operating at or near its nameplate power capacity, is able to perform this function reliably as it is producing significant amounts of power; however, an autonomous wind-to-thermal system presents a challenge due to the difficulties associated with the start-up process of this type of turbine. The start-up difficulty is quantified herein by using a set of well-referenced vertical-axis wind turbine start-up data to derive the turbine’s torque and power values for each rotational velocity data point. It is shown that the turbine produces minimal positive torque during an extended region of operation around tip-speed ratio λ=1. A fluid-agitation thermal generator is considered by employing fluid mixing theory to compute the torque of a conceptual mixing impeller for different impeller diameters and styles. A thermal generator impeller is sized based on the derived experimental values and operational characteristics of the vertical-axis wind turbine data set. Thermodynamic analysis for the conceptual fluid-agitation generator shows that for an enclosed fluid volume ▪ = 1L, a fluid temperature rise of approximately ΔT=5°C can be achieved during one hour of system operation. The results demonstrate the potential of H-Darrieus turbines as renewable heat generating devices, while highlighting the need for careful system design to achieve successful start-up.

Investigating the effects of wind concentrator on power performance improvement of crossflow wind turbine

Small wind turbines are efficient for solving power supply problems in remote off-grid regions. A crossflow wind turbine is a drag-based small vertical axis wind turbine, which is suitable for small-scale power generation in the built environment because of its low aerodynamic noise. However, the power performance of a crossflow wind turbine is generally lower than that of a Savonius wind turbine. Aiming at improving the performance of a crossflow wind turbine, this study develops a wind concentrator by adding two parallel plates with flanges, which is based on the “wind lens” concept, to an arc-shaped windshield, which is based on an existing concept of a flow deflection device for a crossflow wind turbine. The effects of adding two parallel plates with flanges to the windshield (i.e., the effects of the wind concentrator) on the performance of the crossflow wind turbine are quantified with wind tunnel experiments and analyzed based on the flow field characteristics obtained by computational fluid dynamics simulations. The experimental results show that the wind concentrator enhances the maximum power coefficient of the crossflow wind turbine by 108% from 0.12 (without wind concentrator/windshield) to 0.25 (with the wind concentrator), whereas the arc-shaped windshield improves it by 48% from 0.12 to 0.17 (with the windshield). The numerical simulations reveal that the main cause for the power performance enhancement is a downward deflection of the approaching flow to the upper part of the rotor because of a significant increase in the pressure level on the upwind side of the upper flange and an overall decrease in the pressure level in the wake of the wind concentrator. In conclusion, adding two parallel plates with flanges to an arc-shaped windshield is effective for significantly enhancing the power performance of a crossflow wind turbine.

Centrifugal controller of rotation frequency for vertical axis wind turbines

The market for small vertical axis wind turbines (VAWTs) continues to grow rapidly, filling up especially the low wind potential locations. Since the Saudi Government has announced to install 9 GW of wind power by 2032, this ambitious plan could be at least partially improved by the small wind turbines, taking into account the low annual mean wind speed on the most Kingdom of Saudi Arabia territory.However, the safety and durability of most commercially available VAWTs have not been adequately addressed with respect to the turbine over speed in high wind speed conditions.The presented research gives a methodology for calculating a cost-effective dynamic braking controller, based on a centrifugal mechanical activation spring-load mechanism with a pendulum. The analysis is focused on a small two-tier 3 kW Darrieus VAWT, where a mechanically activated friction brake is deployed as the turbine rotational speed approaches a red line. The proposed method makes a small turbine absolutely safe on any available wind speed and/or during accidental electric load switch off. The analysis was made for a typically high continental wind speed of 25 m/s.The paper presents the calculation model in VisSim software. Controller parameters were developed as the result of the research conducted on a functional turbine of the specific size in the model. The experiments covered two different cases: with a relatively low spring stiffness coefficient (400 N/m), showing the periodical oscillations of a controller pendulum on the cut-out speed and a high spring stiffness coefficient (4000 N/m), which the VAWT rotor can be surely braked at.The paper is intended to provide the mathematical basis for the scientific analysis, as well as providing practical implementation information to engineers building similar turbines, including Savonius, Darrieus, H-Darrieus, helix shape, V-type, and any other types of rotating rotors. The estimated capacity utilization factor (CUF) of any VAWTs, when using the proposed centrifugal mechanical controller, can be increased twice to 82% for on-land small VAWTs.

Health Monitoring and Diagnosis System for a Small H-Type Darrieus Vertical-Axis Wind Turbine

As the wind power market grows rapidly, the importance of technology for real-time monitoring and diagnosis of wind turbines is increasing. However, most of the developed technologies and research mainly focus on large horizontal-axis wind turbines, and research conducted on small- and medium-sized wind turbines is rare. In this study, a novel low-cost and real-time health monitoring and diagnosis system for the small H-type Darrieus vertical axis wind turbine is proposed. Turbine operating conditions were classified into parked/idle and power production. In the case of the power production condition, abnormality diagnosis was performed using key monitoring parameters, including vibration, fundamental frequency, the bending stress of the tower and generator vibration. The turbine abnormalities were diagnosed in two stages by applying the alert and alarm limits, determined by referring to international standards and material properties and the long-term measurement data together.

Research on Matching Characteristics of Wind Turbine and Generator for Small H-shaped Vertical Axis Wind Turbine

Based on the small H-shaped vertical axis wind wheel model (NACA0016),a CFD wind wheel model was constructed. Based on the principle of movinggrid, the grid division of the CFD wind wheel model is completed by usingGAMBIT software, and the boundary conditions such as the inlet boundaryand the outlet boundary are set reasonably. Then, the turbulence model andthe couple algorithm are used to carry out transient simulation calculations,and finally the aerodynamic parameter curves of the two-dimensional CFDwind wheel model are obtained. Based on this, the matching characteristicsof the wind turbine and generator of the small H-shaped vertical axis windturbine are studied. The research results show as follows: when the incomingwind speeds change in range of (2 m/s, 12 m/s), and the power character-istic curve and torque characteristic curve of the generator wind wheel arerespectively overlap the best power curve and best torque of the generator,the matching characteristics of the small H-shaped vertical axis wind turbinerotor and generator are optimal, which provides reference for carrying outrelated research.

Structural and Aerodynamic Characteristics Analysis of a Small V-shaped Vertical Axis Wind Turbine Rotor

ABSTRACT A detailed comprehensive study of a proposed V-shaped turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The structural analysis section of this work determined the most structurally sound blade geometry from 3 different blade geometries. Using the chosen blade profile, 8 rotor models are developed and are tested numerically. These rotor models are of different configurations, focusing on an inclination angle of 45 and 60 degrees, blade twist angle of 0 and 5 degrees and number of blades. Four rotor models are taken from the initial tests for further study, 3B45D which is a three-bladed rotor with a 45 degree inclination angle, 5B45D which is a five-bladed rotor with a 45 degree inclination angle, 5B45D (5deg) which is a five-bladed rotor with a 45 degree inclination angle and a 5 degree blade twist angle, and 5B60D which is a five-bladed rotor with a 60 degree inclination angle. From the structural study, blade design 2 held the best structural characteristics. The design showed an excellent Von-Mises at 8.8 MPa for static structural and 22.2 MPa for fatigue stress response which is well below the yield strength of ABS Plastic. Both experimental and numerical data have relatively good agreement that is within 15% difference. Overall, maximum power coefficient achieved in this study is about 0.259 numerically and 0.213 experimentally. The best performance is seen by the 3B45D rotor in both static and dynamic study considering experimental and numerical corroboration of results.

Experimental Study of Vertical Axis Wind Turbine Performance under Vibration

An experimental study was conducted to study the effects of flow uniformity on vibration and power generation of a small vertical axis wind turbine (VAWT). Previous studies have confirmed that one of the sources of vibration in the turbine is due to aerodynamic forces, which are due to incident wind. Firstly, understanding vibration is essential before proceeding to the measurements. In this experiment, further understand the vibrations of the turbine in operation, the operating deflection shape (ODS) technique was used. A wind tunnel and flow conditioner were fabricated. Experimental modal analysis (EMA) was conducted, and the dynamic characteristics are gathered. The ODS was conducted for operating the turbine at different speeds, with and without the flow conditioner. Results from EMA and ODS are correlated to explain the behavior of structures. In conclusion, the flow conditioner tested did have a big impact on the response of the structure in terms of vibration up to 30% indifference, but not so much in power generated about 2% indifference.

Numerical study of the effect of turbulence intensity on VAWT performance

This paper demonstrates the capability of CFD to accurately simulate the effect of the flow turbulence intensity on the performance of vertical-axis wind turbines (VAWT). This effect is quite important as it increases the performance of small VAWTs. For this study, two and three dimensional CFD analysis has been performed on different straight-bladed Darrieus-type rotors. Both a small and a large H-Darrieus VAWT with diameters of 0.5 m and 35 m respectively are investigated using NACA0018 blades. Computational results based on a commercial CFD code (Star CCM+) are compared with experimental measurements. Several simulations based on full URANS calculations are proposed. Firstly, the sensitivity of time step, the number of iterations by time step, and discretization schemes are studied. Secondly, the effect of turbulence intensity on the VAWT performance is simulated and compared with experimental data. Finally, results reveal that the power coefficient of a small turbine is increasing for higher turbulence intensity, up to 20%, but stops increasing afterward. For a small turbine H-Darrieus turbine, the power coefficient is increased by 22% when the turbulence intensity is changed from 0.7% to 20%, however, there is no increase detected in the case of a large H-Darrieus wind turbine. The impact of the turbulence intensity was assessed and a range of behaviors was identified.

Design of small wind turbines to produce electricity for low wind speed in Thailand

This work studied the design of small Vertical Axis Wind Turbine (VAWT) S Shape and Leaf Shape which are appropriate for low wind speed in Thailand. The theory of Overlaps Ratio (β), End Plates and Blade Areas which effect to wind turbines operation were analysed. The turbines were tested in a wind tunnel and connected to permanent magnet generator under wind speed conditions close to the real wind speed. The starting up wind speed and Power Coefficient of Leaf Shape were 0.81 m/s and 0.011 and the starting up wind speed and Power Coefficient of S Shape were 0.63 m/s and 0.038, respectively. The results showed that the S-Shape performance was better than Leaf Shape. The results from this study can be applied for developing and improving the small turbine for the application at the low wind speed area in Thailand

Numerical Analysis of the Dynamic Interaction between Two Closely Spaced Vertical-Axis Wind Turbines

To investigate the optimum layouts of small vertical-axis wind turbines, a two-dimensional analysis of dynamic fluid body interaction is performed via computational fluid dynamics for a rotor pair in various configurations. The rotational speed of each turbine rotor (diameter: D = 50 mm) varies based on the equation of motion. First, the dependence of rotor performance on the gap distance (gap) between two rotors is investigated. For parallel layouts, counter-down (CD) layouts with blades moving downwind in the gap region yield a higher mean power than counter-up (CU) layouts with blades moving upwind in the gap region. CD layouts with gap/D = 0.5–1.0 yield a maximum average power that is 23% higher than that of an isolated single rotor. Assuming isotropic bidirectional wind speed, co-rotating (CO) layouts with the same rotational direction are superior to the combination of CD and CU layouts regardless of the gap distance. For tandem layouts, the inverse-rotation (IR) configuration shows an earlier wake recovery than the CO configuration. For 16-wind-direction layouts, both the IR and CO configurations indicate similar power distribution at gap/D = 2.0. For the first time, this study demonstrates the phase synchronization of two rotors via numerical simulation.

Dynamic Analysis of the Optimized Savonius Vertical Axis Wind Turbine Composite Blades

Abstract This article presents a comprehensive study of the dynamic behavior of small vertical-axis wind turbines (VAWTs) based on local fabricated Savonius VAWTs, which is suitable for countries that have a moderate wind speed. The merits of this design are cleanliness, silent, start-up under low wind speed, independent wind directions, adaptability, and ease of manufacturing. Also, this article presents an experimental validation study for the optimized Savonius VAWT. Four verification test configurations of the optimized VAWT composite blades are designed, simulated, and fabricated of Glass—Polyester with different stacking sequence layout for each. Modified mechanical parameters are introduced to improve the scalability, reliability, and accuracy of the developed models. Based on wind energy conversion system basics, aerodynamic characteristics (tip speed ratio (λ) and coefficient of power (Cp)) and dynamic characteristics (natural frequencies and mode shapes) of Savonius rotor models are presented and simulated within solidworks simulation 2020 software. The dynamic characteristics such as frequency, mode shape, and damping factor are extensively investigated using fast Fourier transform (FFT) analyzer. The results show that the role of composite material blades in improving the dynamic performance of a wind turbine is significant.