Small-scale Vertical Axis Wind Turbine Research Articles

Direct wind-powered vertical axis brackish water desalination system

The supply of freshwater based on wind-powered desalination is technically feasible, but energetic losses associated with conventional systems necessitate new approaches. This study explores a direct wind-powered desalination (D-WPD) system using a small-scale vertical axis wind turbine (VAWT) for reverse osmosis via a high-pressure pump without electricity generation or a system controller. A comprehensive parametric study examined the effects of feed water salinity, loading, and wind speed on the system's performance, demonstrating high efficiency under various operating conditions. A stand-alone system demonstrated operation at effectively constant system efficiency, approximately 13.5 %, and low specific energy consumption for a wide range of wind speeds and salinities. Despite the turbine's small projected area of 0.8 m2, the D-WPD system yielded a daily permeate production of up to 0.6 m3/day at an average wind speed of 6 m/s. The D-WPD system surpassed previous wind-powered desalination studies in terms of specific energy consumption, relative efficiency, and relative desalination capacity. Leveraging the environmental benefits of the slow-spinning VAWT, this D-WPD offers a cost-effective off-grid solution for small-scale desalination.

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.

Use of Small-Scale Wind Turbines in Road Lighting

In this research, it has been studied energy consumption by luminaires, used in road lighting, which is providing by small-scale wind turbines. As the application area, the Bitlis-Rahva region, which is the new settlement of the city centre of Bitlis, was chosen. For the study, the wind data at a height of 10 m representing the road lighting poles were recorded with a data logger every 10 minutes (for 1 year). In many studies in the literature, the Weibull distribution has been used in the analysis of wind data and determination of wind energy potential. It has been seen that the accuracy of this method is high and therefore the Weibull distribution is chosen for the power generation capacity of the small-scale wind turbine to be used in road lighting. The maximum likelihood method was used to determine the parameters of the Weibull density function. Considering the dimensions of the lighting poles and the loads they can carry, it was concluded that it would be appropriate to use small-scale vertical-axis wind turbines for energy generation on these poles. It has been determined that the amount of energy produced by the wind turbine on the road lighting pole is much more than the luminaire on a lighting pole will consume.

Systematic investigation of effect of rotor solidity on vertical-axis wind turbines: Power performance and aerodynamics analysis

Small-scale vertical-axis wind turbines (VAWTs) are receiving growing interest for applications in urban areas. However, the unsatisfactory power performance, mainly induced by the complex blade aerodynamics, restricts their development. Optimizing the turbine geometry is expected to improve the blade aerodynamics. In the present study, the effect of rotor solidity on the power performance and aerodynamics of VAWTs is systematically investigated using high-fidelity improved delayed detached-eddy simulations. A wide range of rotor solidity from 0.12 to 0.6 is studied for VAWTs with different numbers of blades, i.e., two- and three-bladed VAWTs. Also, different rotor diameters (0.5 m–2 m), covering VAWTs from domestic to building integration, are compared to explore the scale effect. In addition, the Reynolds number effect induced by the change of turbine geometry is considered and its impact on the solidity effect is elucidated. The results show that a low to moderate rotor solidity (e.g., lower than 0.3) allows the VAWT to achieve appreciable peak power performance. When the inflow velocity is fixed, for a given relatively low rotor solidity (e.g., 0.12), the two-bladed design is expected to achieve higher peak turbine power, while the three-bladed design is more advantageous when the rotor solidity is relatively high (e.g., 0.36). For a given rotor solidity, VAWTs with smaller rotor diameters perform relatively better due to the diminished tip loss effect. The effects of number of blades and rotor diameter are strongly affected by the variation of the chord-based Reynolds number. This study would support the optimal design of urban VAWTs.

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.

Screening analysis and unconstrained optimization of a small-scale vertical axis wind turbine

The demand for alternative and renewable energy sources has been substantially growing in recent years, mainly steered by economic and environmental inconveniences of conventional energy sources, such as oil and its derivatives. In this context, wind energy has emerged as an attractive renewable source, envisioning possibilities of developing more efficient equipment to meet the ever-growing energy demand. In this work, we coupled Computational Fluid Dynamics (CFD) with an optimization based on response surface (RS) methodologies to find an optimal design for a small-scale NACA 0021 Darrieus vertical axis wind turbine (VAWT) operating at a tip speed ratio of 2.63. For that, we investigated four geometric parameters: number of blades (N), rotor diameter (D), chord length (c), and pitch angle (β). For the numerical model, we considered a two-dimensional, incompressible, turbulent, and unsteady flow regime. A sensitivity analysis (SA) via Morris’ method was performed to identify the influence of the four geometric parameters on the turbine aerodynamic performance. Our results reveal that the pitch angle (β) contributes the most (58%) to the turbine performance. The resulting optimized turbine design increased the conversion efficiency by 40%. Additionally, we also present a detailed discussion on the flow phenomenology considering the impact of each one of the four geometric parameters on the power coefficient. Finally, the strategy adopted here, in which a qualitative sensitivity analysis combined to the response surface and unconstrained optimization, was shown to be robust and can be applied to high-dimensional and computational-expensive CFD models to reduce costs with adequate results regarding fluid flow phenomena.

A Novel 10 kW Vertical Axis Wind Tree Design: Economic Feasibility Assessment

A novel, small-scale vertical axis wind turbine tree was designed using turbines combining both Darrieus and Savonius blades. We tested for economic viability using wind data collected at a site in Surat Thani, Thailand. The Weibull distribution and Monte Carlo modeling with financial indices (Levelized Cost of Electricity (LCOE), Net Present Value (NPV), Internal Rate of Return (IRR), and Simple Payback Period (SPP)) were used to analyze data. We found that monthly mean wind speeds varied from 2.35 m/s in October to 2.84 m/s in February, corresponding to a wind power of 28.43 W/m2 and 42.68 W/m2. The average annual power output was 1446.1 kWh for May 2019 to April 2021. Results show that for turbine cut-in to cut-out speeds (2 m/s to 15 m/s), the prototype has potential economic feasibility (NPV > 0 for 64.93%), although the small capacity of the wind tree, in combination with the low average wind speed at the Surat Thani test site, showed a lack of economic viability at this specific location (NPV = USD − 20,946.29). A higher-wind-speed location (Chiang Mai) showed viability, especially at a 10 m height (NPV > 0 for 84.83%). We discuss potential conditions that would make broader use of the prototype feasible.

A Visual Analytics Web Platform for Detecting High Wind Energy Potential in Urban Environments by Employing OGC Standards

Moving into the third decade of the 21st century, smart cities are becoming a vital concept of advancement of the quality of life. Without any doubt, cities today can generate data of high velocity which can be used in plethora of applications. The wind flow inside a city is an area of several studies which span from pedestrian comfort and natural ventilation to wind energy yield. We propose a Visual Analytics platform based on a server-client web architecture capable of identifying areas with high wind energy potential by employing 3D technologies and Open Geospatial Consortium (OGC) standards. The assessment of a whole city or sub-regions will be supported by integrating Computational Fluid Dynamics (CFD) outcomes with historical wind sensor readings. The results, in 3D space, of such analysis could be used by a wide audience, including city planners and citizens, for locating installation points of small-scale horizontal or vertical axis wind turbines in an urban area. A case study in an urban quarter of Stuttgart is used to evaluate the interactiveness of the proposed workflow. The results show an adequate performance, although there is a lot of room for improvement in future work.

Design of optimal flow concentrator for vertical-axis wind turbines using computational fluid dynamics, artificial neural networks and genetic algorithm

Wind energy extraction is one of the fastest developing engineering branches today. Number of installed wind turbines is constantly increasing. Appropriate solutions for urban environments are quiet, structurally simple and affordable small-scale vertical-axis wind turbines (VAWTs). Due to small efficiency, particularly in low and variable winds, main topic here is development of optimal flow concentrator that locally augments wind velocity, facilitates turbine start and increases generated power. Conceptual design was performed by combining finite volume method and artificial intelligence (AI). Smaller set of computational results (velocity profiles induced by existence of different concentrators in flow field) was used for creation, training and validation of several artificial neural networks. Multi-objective optimization of concentrator geometric parameters was realized through coupling of generated neural networks with genetic algorithm. Final solution from the acquired Pareto set is studied in more detail. Resulting computed velocity field is illustrated. Aerodynamic performances of small-scale VAWT with and without optimal flow concentrator are estimated and compared. The performed research demonstrates that, with use of flow concentrator, average increase in wind speed of 20%–25% can be expected. It also proves that contemporary AI techniques can significantly facilitate and accelerate design processes in the field of wind engineering.

VISUAL ANALYTICS WEB PLATFORM FOR DETECTING HIGH WIND ENERGY POTENTIAL IN URBAN ENVIRONMENTS BY EMPLOYING OGC STANDARDS

Abstract. We propose a server-client web architecture identifying areas with high wind energy potential by employing 3D technologies and OGC standards. The assessment of a whole city or sub-regions will be supported by integrating Computational Fluid Dynamics (CFD) with historical wind sensor readings. The results, in 3D space, of such analysis could be used for locating installation points of small-scale vertical axis wind turbines in an urban area.

Energy harvesting via co-locating horizontal- and vertical-axis wind turbines

Co-locating horizontal- and vertical-axis wind turbines has been recently proposed as a possible approach to enhance the land-area power density of wind farms. In this work, we aim to study the benefits associated with such a co-location using large-eddy simulation (LES) and analytical wake models. In this regard, small-scale vertical-axis wind turbines (VAWTs) in triangular clusters are deployed within a finite-size wind farm consisting of horizontal-axis wind turbines (HAWTs). Wake flow within the wind farm and the effect of VAWTs on the overall wind-farm efficiency are investigated and quantified. The results show that the optimal deployment of small-scale VAWTs has a negligible impact on the performance of HAWT arrays while increasing the total power production. For the particular cases considered here, the power output of the co-located wind farm increases up to 21% compared to the baseline case in which only the HAWTs are present. Also, by comparing to the LES results, it is shown that the analytical framework proposed here is able to accurately predict the power production of wind farms including both HAWTs and VAWTs. Finally, as a real-world application, potential benefits of deploying small-scale VAWTs inside the Horns Rev 1 wind farm are explored for various wind directions using the calibrated wake model. The results show potential for about an 18% increase in the wind-farm power production, averaged over all wind directions, for a particular VAWT layout investigated in this study. The levelized cost of energy (LCoE) for the co-located wind farm is also assessed. The simulations finds that meanwhile the installation of VAWTs increases the annual energy production (AEP) of the wind farm, it also increases the LCoE, which is caused by a) lack of operational data, and b) a low TRL (Technology Readiness Levels) for VAWTs and floating foundations.

Performance and Aeroacoustic Noise Prediction for an Array of Small-Scale Vertical Axis Wind Turbines

Small-scale vertical axis wind turbines are good candidates for urban area use where, due to various obstacles, the airflow is turbulent. In urban areas, air velocity is mostly low and site specific, so just in a few places, like tall buildings, there are suitable airflow situation in order to use turbine, so it is a good idea to install more than one turbine in such locations. On the other hand, acoustic noise that is emitted from turbines may bother people living in that area. In the current study, power performance of small-scale vertical axis wind turbines in a V-form array configuration is investigated using detached eddy simulation method. Also, Ffowcs Williams and Hawkings acoustic analogy formulation is conducted in order to predict the noise radiation level of turbines. Results showed that power performance of most of the turbines increased due to venturi effect that is made by low speed regions behind turbines. Acoustic noise analysis showed that there is a strong enhancement in sound pressure level in receivers compared with the isolated turbine.

Experimental study on novel curved blade vertical axis wind turbines

This paper presents the experimental study into the design and the electrical performance of a few novel curved blade vertical axis wind turbines. In the wind turbines, blade shape and quantity are crucial. In this study, curved wind blades are designed, fabricated, and used in developing the small-scale vertical axis wind turbines. Wind tunnel tests were carried out, and Results were presented for cases of vertical axis wind turbines with 2-blade, 3-blade, 4-blade configurations. Electrical parameters were monitored and compared for three different configurations. Results show that the curved blade wind turbine with a 3-blade configuration performs better when compared to the other two configurations.

Computational fluid dynamics study of Savonius rotors using OpenFOAM

In this work, two-dimensional models of Savonius rotors are simulated using OpenFOAM® in order to predict the aerodynamic performance of small-scale vertical-axis wind turbines. The results are reported analyzing the aerodynamic performance and forces acting on the rotors. Power coefficient, [Formula: see text], is compared with experimental data for each operation point, and for three different geometries. Simulations with first- and second-order discretization schemes are carried out and compared, both quantitative and qualitative. Since usual grid dimensions result not to be suitable for simulations of Savonius rotors, an analysis of different domains is performed and compared. Finally, a set up for computational fluid dynamics simulation of two-dimensional Savonius rotors is proposed. The fluid–rotor interaction is analyzed and the vortex shedding is correlated with [Formula: see text] values and wake description.

Development of a Small-Scale Vertical Axis Wind Turbine for Generation of Compressed Air for Pneumatic Systems

This work presents the development of a cost effective vertical axis wind turbine for generation of compressed air using locally sourced materials. The design of the wind turbine takes into consideration the reduction in the weight and size of the turbine thereby lowering production and installation costs. This increases the efficiency by increasing the resistance from dynamic loads and reduction of acoustic noise discharge. The following locally sourced materials were employed for the development of the wind turbine compressed air system: acrylonitrile butadiene styrene, teflon, polyethylene terephthalate, mild steel, rubber and wood filings. The blade design is of the form airfoil shape of NACA 2412 type typical of air crafts wings with a chord of 50 mm and utmost camber of 2% sited 40% (0.4 chords) from the leading edge and utmost thickness of 12% of the chord. The aerodynamic properties include angle of attack which is 2.2° and the utmost twist angle which is 25.66°. From the performance evaluation, maximum tip speed ratio of 0.9 was achieved as well as power output generation of approximately 14 watt at 10.2 m/s wind speed. The findings of this project identify compressed air energy storage as a viable alternative to chemical energy storage generated from wind turbines. The developed turbine will contribute significantly to the effective conversion of wind kinetic energy into pressure energy as opposed to electrical.

The State-of-the-Art Technology of H-Type Darrieus Wind Turbine Rotors

AbstractThere has been a resurgence of interest in the development of small-scale vertical-axis wind turbines (VAWTs) in the past few decades as is evident from the plethora of published scientific work. This attention may be attributed to the desperate need for cheaper, cleaner, and off-grid mechanisms for generating electric power. In such hasty scenario, VAWTs are being considered as one of the potential solution for small-scale power generation. Among the VAWTs, H-type Darrieus rotors have undergone extensive exploration. In this review work, an attempt has been made to assemble all the major areas of research done in the field of H-type Darrieus rotor development. These areas include the aerodynamic models, computational fluid dynamics (CFD) methods and turbulence models, self-starting and dynamic stalling behavior, blade-vortex interaction and wake studies, and blade designs and optimization studies, besides topics of special interest like blade curvature effects and skewed flows. Overall, the work gives a comprehensive review of the state-of-the-art technology of the H-type Darrieus rotor. Finally, recommendations have been made for each of the areas keeping in view of the technological development.

Three-Dimensional CFD Simulation and Experimental Assessment of the Performance of a H-Shape Vertical-Axis Wind Turbine at Design and Off-Design Conditions

The paper presents the results of a computational study on the aerodynamics and the performance of a small-scale Vertical-Axis Wind Turbine (VAWT) for distributed micro-generation. The complexity of VAWT aerodynamics, which are inherently unsteady and three-dimensional, makes high-fidelity flow models extremely demanding in terms of computational cost, limiting the analysis to mainly 2D or 2.5D Computational Fluid-Dynamics (CFD) approaches. This paper discusses how a proper setting of the computational model opens the way for carrying out fully 3D unsteady CFD simulations of a VAWT. Key aspects of the flow model and of the numerical solution are discussed, in view of limiting the computational cost while maintaining the reliability of the predictions. A set of operating conditions is considered, in terms of tip-speed-ratio (TSR), covering both peak efficiency condition as well as off-design operation. The fidelity of the numerical predictions is assessed via a systematic comparison with the experimental benchmark data available for this turbine, consisting of both performance and wake measurements carried out in the large-scale wind tunnel of the Politecnico di Milano. The analysis of the flow field on the equatorial plane allows highlighting its time-dependent evolution, with the aim of identifying both the periodic flow structures and the onset of dynamic stall. The full three-dimensional character of the computations allows investigating the aerodynamics of the struts and the evolution of the trailing vorticity at the tip of the blades, eventually resulting in periodic large-scale vortices.

Effect of blade pitching on power coefficient of small-scale vertical axis wind turbine at different tip speed ratios

This article analyses the effect of best blade pitching positions on the power coefficient of vertical axis wind turbine at different tip speed ratios. Analysis of the power coefficient of the vertical axis wind turbine is carried out for optimized six blade pitching curves. The first three pitching curves are designed for the tip speed ratios below 1.5 (0 < λ < 1.5) and other three are for the tip speed ratios in the range of 0 < λ < 3. The double multiple stream tube model is used for the present analysis. The results are compared between the optimized and sinusoidal pitching curves. It is concluded that the best optimized pitch position blade method improves the power coefficient than the typical sinusoidal blade pitching in the range of tip speed ratios 0 < λ < 3.

Effects of Offset Blade on Aerodynamic Characteristics of Small-Scale Vertical Axis Wind Turbine

A new way of connecting blade to rotor shaft named offset blade method was proposed for straight-bladed vertical axis wind turbine (SB-VAWT) in this study. In order to invest the efficiency of this method and effects of main parameters including offset length and blade airfoil on improving the output power performance and static starting characteristics, numerical simulations and wind tunnel tests were carried out. Four kinds of blade airfoil including NACA0012, NACA0018, NACA0024 and S809 were selected to analyze the influence of blade thickness and symmetry on SB-VAWT with offset blade. Numerical simulations were firstly carried out on output power for the rotor with 6 kinds of offset length for each airfoil. Wind tunnel tests were also carried out to compare with the results of simulations. The flow fields of rotor with different offset lengths were simulated and the effects of offset blade were analyzed. The optimum offset length among all studied for output power performance was found. Furthermore, the static starting torque and aerodynamic force characteristics of the rotor with optimum offset length were researched. According to the results, appropriate offset length can improve the output power characteristics and smooth the fluctuations of the static torque during one rotational period. The best offset length varies with the airfoil.

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.