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A critical review of vertical axis wind turbines for urban applications
Abstract
Wind energy is one of the most promising renewable energy resources for power generation, and rapid growth has been seen in its acceptance since 2000. The most acceptable classification for wind turbines is by its axis of orientation: Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). HAWTs are used in many countries for medium-to-large scale power projects, and most commercial installations around the globe are solely based on these turbines. On the other hand, HAWTs are not recognized as a viable option to harness the energy of the wind in urban areas, where the wind is less intense, much more chaotic and turbulent. VAWTs are suggested as a better choice for cities and isolated semi-urban areas. Several attributes have been suggested for the large-scale deployment of VAWTs, e.g., good performance under the weak and unstable wind, no noise and safety concerns, and aesthetically sound for integration in urban areas. Significant research has been published on wind turbine technology and resources assessment methodologies, and this review paper is a modest attempt to highlight some of the major developments of VAWTs, with a focus on the integration with urban infrastructure. Several recommendations have been drawn based on the state-of-the-art information on the subject for future studies and acceptance of wind turbines in the urban areas. It was concluded that further research is critical in making VAWTs a viable, dependable, and affordable power generation technology for many low and decentralized power applications.
... While WTs are generally installed offshore, or onshore at rural locations where wind is most intense, consistent and unperturbed (Kumar et al. 2018), recent attention has been drawn to the prospect of installing small wind turbines (SWTs) within urban areas. Small urban wind turbines (SUWTs) can offer several advantages such as clean energy and fewer grid requirements. ...
... To aim for local energy generation in the city, local wind energy harvesting can be used. It can have several advantages, including reduced local emissions, reduced grid load and fewer energy losses (Gagliano et al. 2013;Gil-García et al. 2022;Heagle et al. 2011;Kumar et al. 2018). ...
... LWTs installed in non-urban areas are generally unsuitable for urban areas. SUWTs are most suitable for urban areas given their reduced size, adaptability to turbulent wind flow conditions and less demanding structural implementation requirements (Kumar et al. 2018). ...
Transitioning to renewable energy resources is necessary to address the energy and climate crisis and to be in accordance with UN Sustainable Development Goals (SDGs) 7, 11 and 13. Urban wind energy harvesting is still emerging mainly with the use of small wind turbines. Given their implementation challenges, positive and negative effects need to be weighed to make informed policy decisions and regulations. This systematic review evaluates the macro- and micro-scale environmental effects related to implementing small urban wind turbines (SUWTs). Although publications exist on diverse aspects of SUWTs, a review that addresses the broad range of identified environmental effects of SUWT implementations has been lacking until now. This review shows that while the study of the SUWTs’ environmental effects can build on the effects associated with large wind turbines, there are also significant differences. Given the heterogeneity of urban conditions, the implementation of SUWTs requires detailed local environmental assessment to characterise accurately most environmental effects, notably the net life-cycle primary energy performance and associated GHG emissions, raw materials depletion, recycling, safety, noise, visual and light pollution, and effects on urban wildlife. Effects that require further investigation and which possibly raise regulatory or social acceptance issues are identified and discussed. Policy relevance Harvesting urban wind energy can yield multiple environmental, efficiency and resilience benefits. However, several research and policy gaps remain to be addressed before deploying small wind turbines in urban contexts. These include: the need to quantify the net environmental gains of SUWTs based on their performance and life-cycle assessment; the structural implications of deploying SUWTs on existing buildings; the effect of SUWTs on local air quality and microclimates; the potential health and safety risks to those who may pass by; the effects of SUWTs on ecosystems; and the combined effects of SUWTs on people (e.g. noise or light annoyance). Further research and regulation can help to minimise the negative impacts and ensure social acceptability.
... Small wind turbines can be considered micro (diameters of 1.5 m (or 0.5-1.25 m) and less with annual energy generation of about 1000 kWh, 0.004-0.25 kW), mini (diameters of 1.5-2.6 m (or 1.25-3 m) and annual energy of 1000-2000 kWh, 0.25-1.4 kW), and domestic scale (diameters of 2.7-9 m (or 3-10 m) and annual energy of 2000-20,000 kWh, 1.4-16 kW) [3][4][5]. The application of the micro type is for low-power purposes, such as battery charging, simple lighting, and remote devices, while the domestic type can be used for residential households, farms, and telecommunications [3]. ...
... Higher capacity wind turbines can be considered commercial (diameters of 10-20 m, 16-100 kW), medium (diameters of 20-50 m, 100-1000 kW), and large (diameters of 50-100 m, 1000-3000 kW) [4,5]. As the turbine size and height increase, it is possible to utilize a higher quality wind and work under higher Reynolds numbers, while concerns regarding impacting the environment, structural stress, noise, manufacturing, and maintenance arise. ...
... More friendly with avian wildlife [21]. • Suitable for urban areas, low-quality winds, and severe wind climates [4,22]. • Less susceptible to flow turbulence, which provide more flexibility in integrated layout [23]. ...
While the wind turbine industry has been primarily dominated by horizontal-axis wind turbines, the forefront of knowledge of these turbines has revealed significant challenges in various aspects, including manufacturing, structural design, cost, and maintenance. On the other hand, the advantages associated with Darrieus vertical-axis wind turbines (VAWTs) demonstrate significant potential that can address the existing challenges of the wind turbine industry. Current work aims to investigate the practicality of this potential for the wind energy sector. To this end, the benefits of employing Darrieus turbines for domestic and industrial applications, isolated operation, and on/offshore windfarm applications have been explored. It is apparent that Darrieus VAWTs are better suited to a wide range of environments, whether they are deployed in isolation or integrated systems, and whether they are utilized on a small or large scale. Darrieus VAWTs are adaptable to urban unsteady variable wind, are less expensive on large scales, provide higher power density at the windfarm level, and provide stability for offshore platforms. Nevertheless, challenges remain in fully harnessing VAWT potential rooted in their complex aerodynamics. This serves as a primary challenge for VAWTs to address the challenges of the wind turbine industry in line with the 2050 roadmap.
... The VAWTs are comparatively simpler in design and do not require a Yaw mechanism due to the Wind Turbine (WT) blade orientation. The low cut-in speed, low level of noise and ability to be installed in urban areas, make the VAWTs the preferable choice to be used in urban locations [4]. VAWT are usually categorized into two main categories, Savonius WT and Darrieus WT. ...
... Most of the development was made on a large scale offshore and onshore WT far away from the city where the wind speed is mostly intense, consistent and constant. In contrast, there is a significant wind energy in the urban areas with considerable potential for energy generation in motorways, high-rise buildings, and on the top of the roofs of local houses [4]. Developing an effective clean energy source of power closer to the consumer place of use in the cities minimize the use of hydrocarbon-based electricity generation. ...
... In 1931 Georges Jean Marie Darrieus (a French engineer) developed the Darrieus VAWT [8,9]. The Darrieus wind turbines are lift force type WT and have the ability to provide more energy and a higher coefficient of power when compared to same scale Savonius WT [4]. Darrieus WT blades move in a circular route; a net force will be developed due to the interaction between the airflow and the airfoil, this net force pushes the turbine blades in which create a torque on the shaft of the wind turbine. ...
... The Darrieus rotor, known for its eggbeater shape, provides high efficiency under optimal high wind conditions; while the Savonius rotor, with its semi-cylindrical design, is often used for low-speed, low-torque applications. Advances in materials science and aerodynamics have significantly improved the performance and feasibility of VAWTs in recent years, leading to renewed interest in their potential for urban and offshore applications [7]. ...
... Recent studies have highlighted the advantages of VAWTs in urban environments, where their compact design and capabilities to capture wind from all directions make them suitable for inte-gration into buildings and other structures. This is particularly relevant given the growing trend towards decentralized energy production and the need for innovative solutions to harness wind energy in built environments [7]. Additionally, VAWTs have shown promise in offshore wind farms, where their lower height and reduced sensitivity to turbulent wind conditions can be beneficial [8]. ...
Vertical-axis wind turbines (VAWTs) have garnered increasing attention in the field of renewable energy due to their unique advantages over traditional horizontal-axis wind turbines (HAWTs). However, traditional VAWTs including Darrieus and Savonius types suffer from significant drawbacks -- negative torque regions exist during rotation. In this work, we propose a new design of VAWT, which combines design principles from both Darrieus and Savonius but addresses their inherent defects. The performance of the proposed VAWT is evaluated through numerical simulations and validated by experimental testing. The results demonstrate that its power output is approximately three times greater than that of traditional Savonius VAWTs of comparable size. The performance of the proposed VAWT is further optimized using machine learning techniques, including Gaussian process regression and neural networks, based on extensive supercomputer simulations. This optimization leads to a 30% increase in power output.
... Selfstarting capabilities have been implemented in the Darrieus system to help the turbine to start. 8 Considering the size, efficiency, and design, the turbine can produce around 80-4,100 MWh of energy per year. 7 VAWTs and HAWTs are complementary to each other because they both excel in the disadvantages of the other. ...
... Savonius vs Darrieus rotor blades.8 ...
Magnetic Levitation (MAGLEV) systems are becoming increasingly popular in verticalaxis wind turbines due to their ability to reduce friction and wear. The present research investigates the design, construction and efficiency of a direct drive magnetically levitating Savonius vertical-axis wind turbine. In fabricating the prototypes of these wind turbines, three variations were developed and tested. The three variations of cup blade diameter size were tested with solidities of 0.545 (0.076 m diameter), 0.367 (0.05 m diameter), and 0.285 (0.038 m diameter cups). Tests were performed to determine the most effective approach for medium to high wind applications with and without MAGLEV. It was found that the MAGLEV system, with a solidity of 0.545, achieved the best efficiency and tip speed ratio of 0.56. In scaling the turbine, the research shows a promising design for manufacturing and further testing of these prototypes.
... This type of turbine is well-investigated, and improving its aerodynamic performance is challenging. More and more efforts are concentrated on vertical-axis wind turbines (VAWTs), especially to bridge the aerodynamic performance gap between these two types [1,2]. ...
... The most critical challenge is rotor aerodynamic performance estimation because of the phenomena which are complicated to model, such as dynamic stall and blade-wake interaction [4]. The power performance of VAWTs depends on various operational parameters, among others, an airfoil (shape, chord length), blade pitch angle, the solidity of a turbine, Reynolds numbers, tip speed ratio, shaft diameter, and turbulence intensity [1,5]. ...
The aim of this study was to assess the accuracy of predicting the aerodynamic loads and investigate the aerodynamic wake characteristics of a vertical axis wind turbine (VAWT) rotor using a simplified two-dimensional numerical rotor model and an advanced numerical approach - the Scale Adaptive Simulation (SAS) coupled with the four-equation γ-Re_θ turbulence model. The challenge for this approach lies in the operating conditions of the rotor, the blade pitch angles, and the very small geometric dimensions of the rotor. The rotor, with a diameter of 0.3m, operates at a low tip speed ratio of 2.5 and an extremely low blade Reynolds number of approximately 22,000, whereas the pitch angles, β, are: -10, 0, and 10 degrees. Validation was conducted based on high-fidelity measurements obtained using the PIV technique at TU Delft. The obtained results of rotor loads and velocity profiles are surprisingly reliable for cases of β=0° and β=-10°. However, the 2-D model is too imprecise to estimate both aerodynamic loads and velocity fields accurately.
... These turbines can generate electricity for residential use with minimal transmission loss, making them a highly efficient choice. Additionally, their unique design allows them to harness wind power from any direction, ensuring consistent power generation regardless of the wind conditions [1,2]. VAWTs are classified into drag-and lift-type turbines. ...
Vertical axis wind turbines have shown potential for urban energy harvesting but suffer from weak start‐up performance. This study introduces a novel dual‐row turbine that combines J‐shaped and conventional blades to harness both drag and lift forces, achieving enhanced performance over a wide operational range. Through computational fluid dynamics simulations and Taguchi optimization, the turbine demonstrated a higher maximum power coefficient of 0.52 and a superior power performance at low tip speed ratios. This innovative design significantly surpasses conventional hybrid Savonius‐Darrieus, as well as single‐ and dual‐row Darrieus designs. Among the five main parameters analyzed, the tip speed ratio (λ) had the strongest influence on the performance, followed by the type of airfoils (α), radial ratio (δ), solidity ratio (σratio), and angular distance (ϕ), respectively. The optimization results identified the optimal operational point of the turbine at λ = 2, ϕ = 0, δ = 1.4, σratio = 1.5, and α = 21 (utilizing J‐shaped blades in the inner row and conventional blades in the outer row). These findings highlight the potential of the hybrid dual‐row Darrieus design to enhance vertical axis wind turbine efficiency and pave the way for its application in urban wind energy.
... Because of this feature, VAWTs can extract power from all wind directions without orientation control, lending to suitability in locations with a high degree of variability in the wind resource. There are two main types of VAWTs; Savonius and Darrieus, which operate on drag and lift forces, respectively [50]. Darrieus, or lift-based VAWTs, generally have a higher achievable efficiency; however, they are unable to self-start due to their symmetry, thus requiring input energy to initiate rotation. ...
The present work provides a framework for the comprehensive assessment of energy-harvesting resources in buildings, encompassing environmental, anthropogenic, and recyclable sources. A review of resources and state-of-the-art energy-harvesting technologies is presented, including an outlook on the future theoretical limitations of their performance. The assessment framework is applied to a case-study commercial building located in Toronto, Ontario, Canada. The available resources are categorized into three orders of magnitude with respect to achievable power generation, with solar and wind in the first tier, elevator potential and fitness centres in the second tier, and sources including vibrations, occupant traffic, and thermoelectric conversion in the third. Situated in a mid-rise context, the total annual resource magnitude is found to be eight times greater than the building demand. However, only an overall 10% of the available resource is converted with the harvesting applications and efficiencies considered, resulting in a net energy deficit. It is shown that with maximum theoretical efficiencies, the conversion rate can reach 30% resulting in 151% surplus electrical generation for the building in question.
... The VAWT, with its unique design, offers promising solutions in integrated grid systems, while its development has been relatively limited compared to the widely utilized HAWT primarily due to its inferior aerodynamic performance. 6,84,85 In the 1970s, due to the political instability in the Middle East leading to a sharp increase in world oil prices, the oil crisis brought significant attention to renewable energy, resulting in a renaissance period for VAWTs. 7 However, in the 1990s, interest in VAWTs began to wane. ...
Amid the escalating global demand for renewable energy sources, wind energy has emerged as a pivotal player, positioning itself as the primary energy solution for many countries and regions. The evolution of wind turbine technology has not only elevated the cost-effectiveness and efficiency of wind power but has also been instrumental in diversifying energy portfolios. From innovative blade designs to cutting-edge data analytics and extending its reach from land-based to deep-sea deployments, the breakthroughs in modern wind turbines are charting new horizons for sustainable development. This paper summarizes the conceptual design and most recent development of three types of novel wind turbines: two-bladed wind turbines, dual-rotor wind turbines, and vertical-axis wind turbines. Additionally, it delves into the aerodynamic research methods behind these three novel wind turbines. Our objective is to give readers a comprehensive insight into these research techniques.
... Hence, most commercial wind powers use horizontal-axis wind turbines (Hamza et al., 2023). However, VAWT, such as the Savonius wind turbine, has several advantages over the HAWT: omnidirectionality, simple design, good-starting ability, lower noise, and easier maintenance (Al-Gburi et al., 2022;Kumar et al., 2018). These advantages make the Savonius wind turbines suitable for harnessing wind power in remote and urban sites (Le et al., 2022;Ishugah et al., 2014). ...
... A BIWT can be any type of wind turbine that needs to be selected based on the nature and availability of wind speed [53]. Mostly, it is seen that a vertical-axis wind turbine (VAWT) is a better choice in the urban landscape [54]. ...
This study explores the integration of wind power generation into urban infrastructure via a rooftop vertical-axis wind turbine. A rigorous experimental framework was established by installing a small-scale turbine on an urban building for performance assessment under controlled conditions. Simulated environmental conditions were created using a pedestal fan and blower to evaluate mechanical interactions between the components and electrical output efficiency of the turbine. Extensive numerical modeling was conducted to analyze turbine performance, by computational fluid dynamics using ANSYS FLUENT. The results reveal that the turbine operates efficiently even at low to moderate wind speeds (0.5–6 m/s), demonstrating its feasibility for urban deployment. Performance tests indicated that, as the shaft rotational speed increased from 55 rpm to 115 rpm, the output voltage, current and power varied nonlinearly in the ranges of 3–11.9 V, 20–130 mA and 0.05–2.7 W, respectively. Vibration measurement at specified turbine locations revealed nonlinear variation in displacement, velocity, acceleration and frequency without fixed patterns. Good agreement was observed between the experimental and numerical results. The numerical model yielded interesting profiles related to velocity and turbulence distributions, apart from torque, mechanical power and electrical voltage. Important conclusions were drawn from the entire work.
... As a result, for this type of setting, alternative technologies as Vertical Axis Wind Turbines (VAWT) are better suited than the traditional Horizontal Axis Wind Turbines (HAWT), offering lower starting wind speeds, intrinsic omnidirectionality, better behavior with tilted and irregular winds and gusts, and less noise due to the lower tip-speeds [18]. Despite their lack of industrial support because of their lower efficiency, two decades of intense research have yielded more efficient turbine designs, featuring straight blades, lower solidity and a better upscaling capacity [19]. ...
Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies. In this work, bioinspired Trailing Edge Serrations (TES) were evaluated on a typical Vertical Axis Wind Turbine (VAWT) airfoil, the DU06-W200. As noise reduction benefits of these mechanisms are already well-established, this study focuses on their impact on airfoil and VAWT performance. A saw-tooth geometry was chosen based on VAWT specifications and existing research, followed by a detailed assessment through wind tunnel tests using a newly developed aerodynamic balance. For a broad spectrum of attack angles and Reynolds numbers, lift, drag, and pitching moments were carefully measured. The results show that TES enhance the lift-to-drag ratio, especially in stalled conditions, and postpone stall at negative angles, expanding the effective performance range. A notable increase in pitching moment also is also observed, relevant for blade-strut joint design. Additionally, the impact on turbine performance was estimated using an analytical model, demonstrating excellent accuracy when compared against previous experimental results. TES offer a modest 2% improvement in peak performance, though they slightly narrow the optimal tip-speed ratio zone. Despite this, the potential noise reduction and performance gains make TES a valuable addition to VAWT designs, especially in urban settings.
... The practical deployment of Wind-Powered Cars (WPC) in remote locations necessitates the resolution of several substantial challenges, including energy efficiency, wind availability, and the establishment of an appropriate infrastructure. In order to maximize the production of power during periods of low wind speed, it is necessary for automobiles to be equipped with high-efficiency VAWTs [46,47]. Authors in [48] have observed, that enhancing energy conversion without compromising vehicle performance necessitates the integration of aerodynamic designs and lightweight materials. ...
It is imperative that a sustainable transportation system, powered by renewable energy resources, be implemented in order to mitigate the impacts of climate change and enhance living standards. A Wind-Powered Car (WPC) is a vehicle that employs a connection between the vehicle and wind turbine blades, thereby leveraging the advantages of wind kinetic energy. The energy is then conveyed directly to the car's wheels via a system of mechanical connections and gears, enabling the vehicle to move without the use of fossil fuels. The absence of an internal combustion engine results in the generation of negligible emissions. The primary objective of this study is to examine the static aerodynamic drag of nine WPC designs with diverse blade configurations of Vertical Axis Wind Turbines (VAWT). To achieve this objective, Autodesk Computational Fluid Dynamics (CFD) was employed to model the aerodynamic drag of WPC designs at varying wind speeds of 4 m/s, 6 m/s, and 8 m/s. The comparative analysis revealed that model 8, featuring a 3-blade Savonius wind turbine without a circular end plate, demonstrated superior efficiency among all car models. This is evident in its ability to generate the highest mechanical power compared to other blade designs. These findings contribute to the understanding of aerodynamic performance in VAWT cars, offering valuable insights for further design optimization. Furthermore, the results highlight model 8 as a promising solution for sustainable transportation, aligned with SDG 7 and SDG 11, through the development of clean and efficient wind-powered vehicles.
... 11,12 Among VAWTs, the Savonius turbine is regarded as the quietest wind energy conversion device since it operates at low tip-speed ratios. This enables the Savonius turbine to turn both at street level and at the top of tall buildings in cities. 13,14 The Savonius turbine for power generation can easily be made on-site using local resources because the blade material is not subject to any significant restrictions. 15 However, the coefficient of power of an isolated Savonius rotor (S-rotor) is typically around 20% which is very low compared to other wind rotors. ...
Savonius vertical axis wind turbine (VAWT) arrays are being studied for urban and semi-urban wind energy harvesting. With limited ground space in these areas, optimizing energy extraction through various array configurations is crucial. This study presents a computational fluid dynamics (CFD) analysis of a four-rotor Savonius VAWT array. Various unit array configurations, based on wake analysis of an isolated Savonius rotors, are evaluated through detailed CFD study. The parameters of interest in this study are the coefficient of power, Cpi ( i= 1, 2, 3, or 4 is the rotor number) at different typical values of the tip-speed ratio, λ=ΩD/2U∞ (where Ω is the angular speed of the rotor, D is the diameter of the rotor, and U∞ is the free stream air velocity) of the constituent rotors of the unit array, rotational orientation as well as the average value of the coefficient of power, Cpa=(∑i=14Cpi)/4. It is observed that at certain configurations of the four-unit array, it is possible to have a power enhancement, Ψ=Cpa/Cp0>1 up to 1.34 (34% gain), where Cp0 is the coefficient of power of an isolated Savonius rotor at the same λ. The observed enhancement is explained using velocity and pressure fields around the unit array. Comparative analysis with previous studies highlights new approaches for designing high-performance Savonius arrays and suggests directions for CFD-based optimization of larger arrays.
... The unique attributes of vertical axis wind turbines render them appropriate for urban settings 11) . In the past few years, there has been rapid development in kilowatt-level VAWTs within urban areas 12) . However, the location of urban installation which have different geometric conditions affect turbine production 13) . ...
This paper investigates the effects on the torque performance caused by deflectors of
the Darrieus turbine. Various deflectors were placed in front of the turbine and disrupted the wind
flow before it came into contact with the turbine blades. Using numerical method, this study aims to
find the deflector’s optimum geometric shape, offset distance, and dimension required for the turbine
to produce the highest torque. This study utilizes flow simulation analysis to simulate the deflector
effect on Darrieus turbine. The result of this study is the optimum deflector geometry and offset
distance for producing highest turbine torque output. From the data gathered it is shown that a
deflector with triangular cross-section with the size of turbine diameter placed 400 mm offset to the
right of the turbine produces the best result. Turbine with this deflector configuration produces 1.24
Nm of torque, eight times higher than its non-deflector counterpart yields 0.14 Nm.
Keywords: deflector; Darrieus turbine; geometry; offset
... In addition, VAWTs do not make too much noise and therefore do not cause noise pollution. Lastly, these wind turbines have a low cut-in speed so they can operate at low speeds, for example in urban areas [5]. Given these advantages, VAWTs are a promising technology when the demand for renewable energy is high. ...
... A thorough comparison of VAWTs and HAWTs was presented by Liu et al. [18], with an emphasis on wind farm aerodynamic efficiency, effectiveness, and energy density. Some of the research on the incorporation of VAWTs with urban infrastructure was highlighted by Kumar et al. [19]. With an emphasis on aerodynamics [20], structural behavior [21], and hydrodynamics [22] offered a thorough overview of floating VAWTs. ...
This study covers the structural optimization of vertical axis wind turbines (VAWTs) that can operate reliably for long periods of time in marine environments, as well as simulation analysis to evaluate their fatigue and strain resistance. Due to the nature of the marine environment, strong wind speeds and constant wave loads are applied, and VAWTs are likely to suffer from fatigue build-up and deformation problems in the long term. In this study, detailed numerical simulations were performed using ANSYS software (2024 R2) to analyze the effects of different airfoil shapes, material choices, tip speed ratios (TSRs), and foundation types on the turbine’s stress distribution and fatigue resistance. The results showed that NACA 0030 airfoil, composite steel, and single-pile foundation performed best under TSR 1.8 conditions, with the potential to reduce strain by approximately 30% and fatigue damage by approximately 25% compared to conventional structures. With this optimized combination, it was found that maintenance costs could be significantly reduced while maintaining structural stability at sea. These results could make an important contribution to the economical and durable design of VAWTs in the future.
... However, it has several intrinsic advantages over the HAWT, such as simpler design, good starting ability, omnidirectional, lower noise, and easier to maintain (Kumar, Raahemifar, and Fung, 2018). These advantages make the rotor more suitable for harnessing wind power in urban sites, building rooftops, and remote areas (Mao et al., 2020;Ishugah et al., 2014;Cho, Jeong, and Sari, 2011). ...
... This type of turbine has been extensively studied, and enhancing the rotor power coefficient characteristics across a broad range of tip speed ratios presents a significant challenge. Increasing attention is now being directed toward improving the aerodynamic performance of vertical-axis wind turbines (VAWT) to narrow the efficiency gap between these two turbine types [1,2]. ...
... Moreover, their smaller physical footprint and lower noise emissions render them suitable for residential and distributed energy systems. However, these turbines face notable challenges, including limited self-starting capability and reduced aerodynamic efficiency at lower Reynolds numbers, which hinder their broader adoption [6,7]. ...
This study investigates the aerodynamic performance and flow dynamics of an H-type Darrieus vertical axis wind turbine (VAWT) using combined numerical and experimental methods. The analysis examines the effects of operational parameters, such as rotor solidity and pitch angle, on aerodynamic loads and flow characteristics, using a 2-D URANS simulation with the Transition SST model to capture transient effects. Validation was conducted in a low-turbulence wind tunnel to observe the impact of variable flow conditions. The LineAverage method for determining the angle of attack demonstrated strong correlations between rotor configuration and load variations, particularly highlighting the influence of blade number and pitch angle on aerodynamic efficiency. This research supports optimization strategies for Darrieus VAWTs in urban environments, where turbulent, low-speed conditions challenge conventional wind turbine designs.
... Salah satu solusi yang paling tepat untuk kondisi kecepatan angin rendah ini adalah penggunaan turbin angin sumbu vertikal (Vertical Axis Wind Turbine, VAWT) (Afidah et al., 2023;Johari et al., 2018;Kumar et al., 2018). Berbeda dengan turbin angin sumbu horizontal yang memerlukan pengaturan untuk mengikuti arah angin, VAWT mampu beroperasi tanpa perlu pengaturan arah angin, sehingga lebih fleksibel dalam menghadapi variasi kecepatan dan arah angin yang sering terjadi di daerah terpencil. ...
Penelitian ini bertujuan untuk mengembangkan turbin angin skala kecil yang efisien dan ekonomis untuk daerah terpencil dengan kecepatan angin rendah di Indonesia. Dalam penelitian ini menggunakan pendekatan kualitatif untuk menganalisis literatur terkait pengembangan turbin angin skala kecil dan penggunaannya dalam konteks energi terbarukan di daerah terpencil. Literatur yang relevan diperoleh dari berbagai basis data akademik seperti Google Scholar, ScienceDirect, dan IEEE Xplore, dengan fokus pada penelitian tentang turbin angin sumbu vertikal (VAWT) dan integrasi energi terbarukan. Analisis kritis dilakukan untuk mengidentifikasi tren, teori, metodologi, serta kesenjangan dalam penelitian sebelumnya, guna memahami perkembangan teknologi dan peluang aplikasinya di daerah terpencil. Hasil karya ini yaitu pengembangan turbin angin skala kecil di daerah terpencil merupakan solusi berkelanjutan untuk memenuhi kebutuhan energi terbarukan, terutama di wilayah pesisir dan perbukitan. Meskipun biaya awal instalasi cukup tinggi, penggunaan bahan lokal dapat mengurangi biaya dan melibatkan masyarakat dalam perawatan sistem. Tantangan utama adalah memastikan turbin berfungsi optimal pada kecepatan angin rendah. Dengan penelitian dan dukungan pemerintah, teknologi ini memiliki potensi besar untuk meningkatkan akses listrik dan mendukung transisi energi terbarukan.
... Wind turbines are classified into vertical axis and horizontal axis types (Tummala et al., 2016;Mendonça & Azevedo, 2017). Horizontal-axis wind turbines (HAWT) typically exhibit higher power coefficients compared to vertical-axis turbines (Kumar et al., 2018;Nabil et al., 2018), *Corresponding Author's Email: muldiy@ft.unp.ac.id (M. Yuhendri) URL: https://www.jree.ir/article_202303.html ...
One method to reduce power loss in wind power plants is by using a low-speed generator that can connect directly to a wind turbine without a gearbox. Low-speed generators require significant mechanical torque, necessitating the wind turbine to produce substantial mechanical torque at low speeds. This requirement can be met by increasing the number and size of blades. This paper proposes a low-speed horizontal-axis wind turbine (HAWT) designed to generate substantial mechanical torque, thus suitable for low-speed generators without gearboxes. The HAWT features six fiberglass blades shaped in a NACA 6412 airfoil. Performance evaluation of the HAWT is based on tip speed ratio (TSR) and power coefficient. The turbine's characteristics were experimentally investigated using a low-speed permanent magnet generator (PMG), a boost converter, and an Arduino Uno controller. Parameter values were observed by testing, the HAWT under varying wind speeds and rotor rotation speeds. Wind speed variation was achievedis varied using a blower, while rotor speed was controlled via a boost converter controlled by an Arduino. Experimental results demonstrate the suitability of the HAWT for its intended purpose, achieving. a maximum power coefficient of 0.34 and an optimum TSR of 5.2.
... Li et al. [21] also performed a study on two vertical axis wind turbines placed side-by-side and showed that the counter-rotating turbine pair with high solidity ratio is suitable in low wind density urban areas, whereas the pair with low solidity ratio is suitable in high wind density regions. In this context, a review of vertical axis wind turbines in urban environments was performed by Kumar et al. [22]. ...
... Their study showed wind energy's capability to generate power; however, the blades must be carefully selected to minimize losses. Rakesh Kumar et al. [29] reviewed the different types of wind turbines; it was concluded that to make VAWT reliable, there is a need for further research. Shukla et al. [30] discussed energy extraction techniques and the stages of design of VAWT. ...
Renewable energy has provided a stable electricity supply with a guaranteed reduction in CO2 production. There are various types of renewable energy, but wind energy appears to be the least expensive option compared to other renewable energy sources. The current study involves the performance investigation of an H Darrius wind turbine in Ilorin Kwara State, Nigeria. Using Ilorin wind data obtained from the Nigeria Meteorological Agency (NIMET), a 2-dimensional CFD analysis was performed on a two- bladed NACA 0018 airfoil profile with the aid of Ansys (Fluent) to unravel the implications of tip-speed ratio(TSR) and azimuthal increments on the instantaneous moment and power coefficients. The study shows that the accuracy of the results depends on the azimuthal increment used. An acceptable azimuthal increment is required for a low TSR, while an increment of 0.5 is a good choice for a high TSR, and the maximum power coefficient was obtained at a TSR of 4.5.
... They are designed to operate at lower wind speeds and can be installed on rooftops or other small areas, making them ideal for urban environments. The small vertical axis wind turbines are generally preferred in an urban environment as they have a unique design that allows them to capture wind from any direction, which is particularly useful in urban environments where wind direction can change quickly and unpredictably due to buildings and other structures [58,59]. They are also quieter than horizontal axis wind turbines, making them more acceptable to the neighbourhood [60,61]. ...
Wind energy being a free source of energy is becoming popular over the past decades and is being studied extensively. Integration of wind turbines is now being expanded to urban and offshore settings in contrast to the conventional wind farms in relatively open areas. The direct installation of wind turbines poses a potential risk, as it may result in financial losses in scenarios characterized by inadequate wind resource availability. Therefore, wind energy availability analysis in such urban environments is a necessity. This research paper presents an in‐depth investigation conducted to predict the exploitable wind energy at four distinct locations within Nottingham, United Kingdom. Subsequently, the most suitable location, Clifton Campus at Nottingham Trent University, is identified where a comprehensive comparative analysis of power generation from eleven different wind turbine models is performed. The findings derived from this analysis suggest that the QR6 wind turbine emerges as the optimal choice for subsequent experimental investigations to be conducted in partnership with Nottingham Trent University. Furthermore, this study explores the selection of an appropriate probability density function for assessing wind potential considering seven different distributions namely, Gamma, Weibull, Rayleigh, Log‐normal, Genextreme, Gumbel, and Normal. Ultimately, the Weibull probability distribution is selected, and various methodologies are employed to estimate its parameters, which are then ranked using statistical assessments.
... Consequently, wind energy is currently receiving increasing attention due to its effectiveness in reducing fossil energy consumption and greenhouse gas emissions. 1 Vertical axis wind turbines (VAWTs) are primarily installed near the ground and are low-altitude wind turbines. Compared to other types of wind turbines, VAWTs can capture wind energy from all directions, can be started at lower wind speeds, are easier and safer to maintain because the generator and main drive are located at the turbine bottom, and produce less noise during operation, which makes them suitable for use in noise-sensitive areas. 2 VAWTs primarily employ straight and helical blades. ...
For aerodynamic performance improvement, a helical blade vertical axis wind turbine (VAWT) with a symmetric structure is proposed. Using NACA0018 as the base airfoil, three-dimensional numerical simulations of the symmetric helical blade VAWT and a helical blade VAWT are performed using the shear–stress transport k–ω model. The aims is to comprehensively explore the correlation and influence between their wind energy utilization coefficients, single-bladed transient moment coefficients, and flow field characteristics under different wind field conditions. Furthermore, the blade cross sections at positions of 0.3H, 0.5H, and 0.7H are symmetrized and subsequently numerically simulated in terms of both global and local symmetries. The symmetrical blades provide smooth and significant average moment coefficients under low tip speed ratios (TSRs) and similar average moment coefficients under high TSRs. The global symmetry helical blade VAWT (GS-helical blade VAWT) exhibited the best performance. Compared to the helical blade VAWT, the average value of the total moment coefficient afforded by the proposed GS-helical blade VAWT is 19.13% higher at TSR = 1 and similar at TSR > 1.9. In conclusion, the proposed symmetric helical blade VAWT exhibits improved aerodynamic performance and can be practically employed.
... Urban environments, which account for over 70% of global energy consumption, present unique challenges and opportunities for renewable energy integration [2]. In this context, Vertical Axis Wind Turbines (VAWTs) have emerged as a promising technology for harnessing wind energy in urban settings, where traditional Horizontal Axis Wind Turbines (HAWTs) are often impractical due to space constraints and turbulent wind conditions [3]. ...
Vertical Axis Wind Turbines (VAWTs) present a promising solution for renewable energy generation in urban environments, where traditional horizontal axis turbines are often impractical. This review paper examines recent advancements in VAWT design optimization for urban settings, focusing on overcoming challenges associated with low-wind conditions and complex urban wind patterns. We analyze innovative aerodynamic designs, including helical and Savonius-Darrieus hybrid models, that enhance performance in turbulent and multidirectional wind flows. The paper also explores materials and manufacturing techniques that balance durability, noise reduction, and cost-effectiveness. Additionally, we review cutting-edge control systems and power electronics that maximize energy capture in variable wind conditions. The integration of VAWTs with building structures and urban planning is discussed, highlighting potential for widespread adoption. Our findings suggest that recent innovations in VAWT technology have significantly improved their viability for urban applications, with some designs achieving efficiency increases of up to 30% in low-wind conditions. However, challenges remain in optimizing start-up performance, reducing production costs, and mitigating environmental impacts in densely populated areas. This review underscores the potential of VAWTs as a key component in sustainable urban energy systems and identifies critical areas for future research and development, including advanced materials, AI-driven control systems, and comprehensive urban wind energy mapping tools.
... One of these is the downscaling of the main horizontal-axis wind turbine (HAWT) [13]. The other two are vertical-axis wind turbines (VAWT), either lift-operated, such as the Darrieus or H-rotor, or drag-operated VAWT, such as the Savonius rotor [14]. Of these, the HAWT has the potential to be the most efficient under suitable conditions but the fact that they need to be yawed into the wind in an environment where the wind direction varies much more significantly at short time scales than higher up in the atmosphere causes the rotor to be frequently not in design conditions. ...
This analysis aims to identify appropriate technology options for wind energy converters across all sizes by matching the sizes of the primary mover and the time scales of the extraction and conversion processes to the wind conditions as quantified by mean winds and turbulence intensity. The approach was to set out the options in a process tree and then group technology options according to common characteristics which can be used to estimate productivity in wind scenarios characterised by the wind speed, wind direction and turbulence statistics.
... [30][31][32] Hence, they are more suitable for urban environments. 33,34 Taking advantage of the ability of VAWT to collect wind energy, we aim to install VAWT at the leading corners of tall buildings to reduce wind loading as well. Wind turbines at the corners of tall buildings have the potential of not only reducing wind loading of the building but also harnessing wind energy. ...
This study experimentally investigates the impact of a pair of vertical-axis wind turbines at the leading corners of a tall building on its aerodynamic characteristics. These wind turbines have the potential to serve dual purposes: harnessing wind energy under normal wind conditions and mitigating wind loading of the building under strong wind conditions. The wind tunnel testing results in this study indicate when the tip speed ratio of the turbines is 0.34, with the wind turbines rotating toward downstream, the standard deviation of lift coefficient of the building decreases by 30.9%. Meanwhile, the mean pressure coefficient and the standard deviation of pressure coefficient on both the side face and leeward face of the building also exhibit a certain degree of reduction. The peak value of the power spectral density of lift coefficient of the building is also significantly decreased. This study clearly demonstrates that the wind turbines at the leading corners of tall buildings have the potential to effectively reduce wind loading of the buildings.
... Wind turbines are divided into two types: horizontal-axis wind turbine (HAWT) and vertical-axis wind turbine (VAWT) [148,149]. Based on the rotor diameter and generation capacity, HAWT can be divided into six categories (micro, mini, small household, small commercial, medium commercial, and large commercial). ...
... This unsteadiness is inherent and persists even if the wind speed is constant or the rotor speed is constant. Due to such complexities, accurate simulation of VAT performance is a challenging task and requires accurate meshing techniques [5,6,7,8] and [9,10,11]. ...
Vertical Axis Turbines (VATs) are gaining traction as decentralized energy sources due to their simple design and suitability for various wind conditions. However, understanding VAT aerodynamics requires robust computational methods. This study compares the accuracy and efficiency of two meshing techniques (sliding mesh and overset mesh) for VAT simulations using OpenFOAM. Validation against experimental data confirms the capability of both methods to capture flow physics and predict turbine performance. The results suggest both techniques offer efficient and accurate VAT simulations, providing valuable tools for future VAT optimization and experimental validation.
The initial design phase of wind turbines utilizes low-fidelity models to predict wind turbine performance. These models require accurate and reliable airfoil polars to estimate the aerodynamic performance. The dynamic behavior is vital for Vertical Axis Wind Turbines (VAWTs), since the blades continuously experience cyclic stall conditions. Recently, the NACA 0022 airfoil is utilized within Vertical Axis Wind Turbines (VAWTs) for its high lift-to-drag ratio and structural strength, which can significantly enhance performance and efficiency of VAWTs under diverse wind conditions. Nevertheless, a comprehensive set of experimental polar for the NACA 0022 airfoil, under both steady-state and dynamic conditions, remains challenging. Hence, the main objective of the study is to experimentally evaluate the aerodynamic performance of a NACA 0022 airfoil under both steady and dynamic pitch oscillations at low Reynolds numbers (75k, 100k, and 150k). An open-type low-speed wind tunnel is used for static and dynamic testing at three reduced frequencies of 0.1, 0.05, and 0.025. Moreover, the performance coefficients of static lift, drag, and moment of the NACA 0022 airfoil is thoroughly analyzed at different Angles of Attacks (AOAs) ranging from 0⁰ to 180⁰. The experiments show that significant hysteresis in the aerodynamic coefficient curves is observed due to hysteresis in the separation-reattachment flow phenomenon, indicating unsteady flow conditions. Additionally, the shape of the hysteresis loop near the stall region was found to be dependent on the reduced frequency of oscillation. Moreover, it is also observed that the onset of the stall is delayed during the up-stroke. In contrast, the flow is reattached earlier during the down stroke in dynamic conditions compared to static and quasi-steady conditions. The results reveal a stall angle shift from 11° at low to 12° at intermediate and 14° at high Reynolds numbers, as well as show an increase in maximum lift coefficient prior to stall, with fluctuations in aerodynamic forces and moment coefficients between 135° and 165. Overall, the proposed approach is applicable to the evaluation of such NACA-0022 airfoil variants that can be parameterized at a broader range of flow conditions.
Vertical-axis wind turbines (VAWTs) offer key advantages such as independence from wind direction, low manufacturing costs, and reduced noise levels, making them highly suitable for urban and offshore wind energy applications. Among various VAWT designs, the J-shaped VAWT demonstrates improved energy capture at low and medium tip speed ratios (TSRs) compared to symmetrical blade VAWTs, which has garnered increased interest in recent years. However, the mechanisms by which J-shaped blades enhance VAWT performance remain insufficiently explored. In this paper, the high-resolution three-dimensional Improved Delayed Detached Eddy Simulation was employed to investigate the evolution and interaction of complex vortex systems in J-shaped and symmetrical blade VAWTs at varying TSRs, aiming to deepen the understanding of J-shaped blade effects on wind turbine aerodynamic performance. The results indicate that the tip vortex plays a role in inhibiting flow separation, while the J-shaped blade generates a stronger tip vortex, conferring upon it an advantage in suppressing flow separation and delaying dynamic stall. Additionally, the smaller pressure differential between the root and tip of the J-shaped blade reduces cross-flow on the blade surface, thereby reducing susceptibility to flow separation. Therefore, as the blade enters the dynamic stall region at low and medium TSRs, the J-shaped blade achieves a higher lift coefficient than the symmetrical blade, yielding greater torque, and enhancing wind energy utilization.
Vertical-axis wind turbines (VAWTs) have garnered increasing attention in the field of renewable energy due to their unique advantages over traditional horizontal-axis wind turbines (HAWTs). However, traditional VAWTs including Darrieus and Savonius types suffer from significant drawbacks -- negative torque regions exist during rotation. In this work, we propose a new design of VAWT, which combines design principles from both Darrieus and Savonius but addresses their inherent defects. The performance of the proposed VAWT is evaluated through numerical simulations and validated by experimental testing. The results demonstrate that its power output is approximately three times greater than that of traditional Savonius VAWTs of comparable size. The performance of the proposed VAWT is further optimized using machine learning techniques, including Gaussian process regression and neural networks, based on extensive supercomputer simulations. This optimization leads to a 30% increase in power output.
Purpose
This study aims to understand the aero-acoustic performance of H-type vertical axis wind turbine (VAWT) with different cavity configurations through numerical simulation, improving its overall performance and making it suitable for urban applications.
Design/methodology/approach
Numerical simulation of VAWT was carried out in ANSYS FLUENT software with turbine modelled through SOLIDWORKS. Unsteady Naiver–Stokes equation coupled with SST k - ω turbulence model was used to model the flow field around VAWT. Ffowcs Williams–Hawkings analogy was used for acoustic prediction from VAWT. Two cavity positions, i.e. at 0.25c from the leading edge and at 0.75c from the trailing edge were fixed with five different layouts considered. The cavity layouts are trailing edge single cavity (TESC), trailing edge double cavity (TEDC), leading edge single cavity (LESC), leading edge double cavity (LEDC) and BASE models. The power curve for five different VAWT configurations was evaluated and validated with experimental, computational fluid dynamics works. The qualitative aspect of wake length and wake recovery rate was evaluated for each configuration. Acoustic readings were carried out through receivers placed in circumferential directions as well as downstream directions.
Findings
The power curve of VAWT shows that TESC tends to be the optimum for urban applications, as it provides maximum power performance compared to other models investigated. TESC delivers a maximum power enhancement of 72.5% compared to BASE models. The cavity in the trailing edge reduces the negative torque and provides enhanced self-starting capability. Cavity-configured VAWT shows better wake recovery than BASE models at near and far fields, enabling them ideal for wind farm applications. In the acoustic case, TESC and TEDC models tend to be quieter at low tip speed ratio (TSR), while at higher TSR, LESC and LEDC prove to be silent. LESC and LEDC tend to reduce sound pressure level value at blade passing frequency compared to BASE models.
Originality/value
Since the rotor performance of VAWT with different cavity configurations has been explored over the past few years, this is the first research work that deals with wake dynamics and acoustic dynamics of VAWT with cavities. This work identifies the acoustic nature of VAWT with cavity depends upon cavity position which in turn depends on operating TSR as well as the direction in which noise is perceived. The application of a cavity in VAWT will be an ideal solution for urban applications with enhanced power performance and lower operating noise.
Aeroacoustic analysis of a small vertical-axis Darrieus wind turbine suitable for urban area applications is performed using numerical simulation and acoustic analogy. The analysis is performed for two helical wind turbine models with three- and four-blade configurations and under different operating conditions. Numerical simulations are performed using the unsteady Reynolds averaged Navier-Stokes method, along with the Ffowcs-Williams and Hawkings aeroacoustic analogy. Validation of the performance of the computational model against experimental data demonstrates its ability to accurately predict the aerodynamic and aeroacoustic behavior of the turbine. The influence of the number of turbine blades and their distance from the center of the turbine on the generated noise is analyzed. The analysis is further focused on the highest power coefficient, obtained at the tip speed ratio of 1.8, and the sound pressure level (SPL) curves recorded by the receivers are analyzed. Predictions show that while the four-blade turbine has a higher SPL than the three-blade one at a downstream position of about four turbine diameters, the situation is reversed at farther downstream positions. The aeroacoustic findings of this research have direct implications for the proper installation of small vertical-axis Darrieus wind turbines in urban areas, where wind turbine generated noise is important.
Purpose
This paper aims to develop an optimal maintenance and spare parts policy for an urban micro wind power system, focusing on two urban micro wind farms (UMWF). The reliability and efficiency of these systems are sought to be enhanced by considering the relationship between urban wind parameters and wind turbine degradation.
Design/methodology/approach
A proportional hazards (PH) model is utilized to describe how urban wind conditions impact turbine degradation. The maintenance strategy includes preventive maintenance (PM), corrective maintenance (CM) and opportunistic maintenance (OM). A multi-objective optimization algorithm is developed to optimize the joint policy of OM plans and spare parts resource allocation.
Findings
The proposed maintenance and spare parts policy effectively balances the trade-offs between PM, CM and OM strategies. Numerical experiments demonstrate that the policy improves the reliability of UMWF, reducing downtime and maintenance costs while ensuring the availability of spare parts when needed. The results show a significant enhancement in system performance compared to traditional maintenance approaches.
Originality/value
A novel maintenance policy and spare parts management approach for urban micro wind power systems is proposed. A multi-objective optimization algorithm is developed to optimize the OM schedule and maintenance spare parts resource management strategy for wind farms in urban wind environments.
The efficiency of twin Savonius vertical axis wind turbines (VAWTs) is studied by optimizing specific configuration parameters: distance between the turbines (S), their configuration angle (φ), and their combination of rotational directions (RD). The Taguchi method is utilized to systematically refine these parameters for optimal performance. The 3D unsteady and incompressible flow model of the system is solved numerically and validated. An orthogonal array (OA) L16 (4 ³ ) is constructed for these factors and their four levels, presenting 16 arrangements. The best arrangement in OA increases the average power coefficient by 11.18% at a rated TSR of 0.8. The findings suggest that the power efficiency is primarily influenced by the configuration angle, with the rotation direction and turbine spacing following suit. The optimum arrangement increases the coefficient of power by 11.58% in comparison to the single turbine. Further analysis is conducted on the flow fields, pressure, and TKE distribution of the best and optimum arrangements.
The Φ-shaped Darrieus wind turbines offer promising applications owing to their omnidirectionality and structural advantages. However, their poor performance at low tip-speed ratios remains a challenge. To address this issue, this study proposes a hybrid rotor consisting of a Φ-shaped and straight-bladed Darrieus rotor. The computational fluid dynamics simulation is employed to investigate the effects of diameter ratio, height ratio, chord length ratio, and inner rotor blade pitch angle on the aerodynamic performance of the hybrid rotor. The findings reveal that the power coefficient reaches a maximum of 0.02531 and the lateral force coefficient is minimized at 0.10588 when the diameter ratio is 0.6. With the height ratio of 0.5, the power coefficient peaks, increasing by 77% compared to the single Φ-shaped rotor. The power coefficient is highly sensitive to the chord length ratio, increasing by 114% compared to the single Φ-shaped rotor when chord length ratio is 1.4. The lateral force coefficient increased significantly when the chord length ratio exceeded 1. In addition, changes in the pitch angle have minimal effects on the thrust and lateral force coefficients, which are beneficial for operational stability. This study provides a theoretical basis for the design of efficient and stable double Darrieus vertical-axis wind turbines, which have promising applications in distributed power generation.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t This study examines the effect of different wind turbine classes on the electricity production of wind farms in three areas of Australia, which present low, low to medium, and medium to high wind potential: Gingin, Armidale, and Gold Coast Seaway. Wind turbine classes determine the suitability of installing a wind turbine in a particulate site. Wind turbine data from six different manufacturers have been used. For each manufacturer, at lest two wind turbines with identical rated power (in the range of 1.5 MW e3 MW) and different wind turbine classes (IEC I, IEC II and/or IEC III) are compared. The results show the superiority of wind turbines that are designed for lower wind speeds (higher IEC class) in all three locations, in terms of energy production. This improvement is higher for the locations with lower and medium wind potential (Gingin and Armidale), and varies from 5% to 55%. Moreover, this study investigates the economical feasibility of a 30 MW wind farm, for all combinations of site locations and wind turbine models.
Compared with a drag-type vertical axis wind turbines, one of the greatest advantages for a lift-type vertical axis wind turbines is its higher power coefficient (Cp). However, the lift-type vertical axis wind turbines is not a self-starting turbine as its starting torque is very low. In order to combine the advantage of both the drag-type and the lift-type vertical axis wind turbines, a lift drag hybrid vertical axis wind turbines was designed in this article and its aerodynamics and starting performance was studied in detail with the aid of computational fluid dynamics simulations. Numerical results indicate that the power coefficient of this lift drag hybrid vertical axis wind turbines declines when the distance between its drag-type blades and the center of rotation of the turbine rotor increases, whereas its starting torque can be significantly improved. Studies also show that unlike the lift-type vertical axis wind turbines, this lift drag hybrid-type vertical axis wind turbines could be able to solve the problem of low start-up torque. However, the installation position of the drag blade is very important. If the drag blade is mounted very close to the spindle, the starting torque of the lift drag hybrid-type vertical axis wind turbines may not be improved at all. In addition, it has been found that the power coefficient of the studied vertical axis wind turbines is not as good as expected and possible reasons have been provided in this article after the pressure distribution along the surfaces of the airfoil-shaped blades of the hybrid turbine was analyzed.
This study aimed to understand the performance and shape characteristics of a helical Savonius wind turbine at various helical angles. The power coefficient (Cp) at different tip speed ratios (TSRs) and torque coefficient (CT) at different azimuths for helical blade angles of 0°, 45°, 90°, and 135° were observed under the conditions of a constant projection area and aspect ratio. The numerical results discussed in this paper were obtained using an incompressible unsteady Reynolds average Navier-Stokes (k-ε RNG) model. A numerical analysis in the unsteady state was used to examine the flow characteristics in 1° steps from 0° to 360°. In addition, an experiment was performed at a large-scale wind tunnel, and the results were compared with those of the numerical analysis. Wind speed correction was also employed because of the blockage effect between the wind turbine and wind tunnel. Our results showed that the maximum power coefficient (Cp,max) values in both cases had similar tendencies for the TSR range considered in this study, i.e. from 0.4 to 0.8, except for the twist angle of 45°. The Cp,max occurred at the twist angle of 45°, whereas it decreased by 25.5% at 90° and 135°. Regarding the CT values at various azimuths, the results showed that the peak-to-peak values in the profiles for 90° and 135° were less than those for 0° and 45°.
Meeting future world energy needs while addressing climatic changes has led to greater strain on conventional power sources. One of the viable sustainable energy sources is wind. But the installation large scale wind farms has a potential impact on the climatic conditions, hence a decentralized small scale wind turbines is a sustainable option. This paper presents review of on different types of small scale wind turbines i.e., horizontal axis and vertical axis wind turbines. The performance, blade design, control and manufacturing of horizontal axis wind turbines were reviewed. Vertical axis wind turbines were categorized based on experimental and numerical studies. Also, the positioning of wind turbines and aero-acoustic aspects were presented. Additionally, lessons learnt from various studies/countries on actual installation of small wind turbines were presented.
In this paper, a novel Darrieus vertical axis wind turbine was designed whose blade can be deformed
automatically into a desired geometry and thus achieve a better aerodynamic performance. A series of
numerical simulations were conducted by utilizing the United Computational Fluid Dynamics code.
Firstly, analysis and comparison of the performance of undeformed and deformed blades for the rotors
having different blades were conducted. Then, the power characteristics of each simulated turbine were summarized and a universal tendency was found. Secondly, investigation on the effect of blade number and solidity on the power performance of Darrieus vertical axis wind turbine with deformable and undeformable blades was carried out. The results indicated that compared to conventional turbines with same solidity, the maximum percentage increase in power coefficient that the low solidity turbine with three deformable blades can achieve is about 14.56%. When solidity is high and also turbine operates at low tip speed ratio of less than the optimum value, the maximum power coefficient increase for the turbines with two and four deformable blades are 7.51% and 8.07%, respectively. However, beyond the optimal
tip speed ratio, the power improvement of the turbine using the deformable blades seems not significant
and even slightly worse than the conventional turbines. The last section studied the transient behavior of
vortex and turbulent flow structures around the deformable rotor blade to explore the physical
mechanism of improving aerodynamic performance. The adaptive blades could obviously suppress the
separation of flow from the blade surfaces.
In this study, a three-dimensional VAWT with a spanwise passively deformable flexible blade has been modelled. The study mainly focuses on the analysis of blade structure characteristics associated with the bending and twist deflection. Two types of flexible blade material and two strut locations supporting H-type blades are being investigated. The unsteady external loads and energy efficiency of VAWT with such designed flexible blade are also being analysed. The simulation results show that the bending and twist deflection peak is positively correlated with the turbine tip speed ratio λ. For a flexible blade, an unevenly distributed structural stress along the blade with a high stress regime in the vicinity of strut location has also been observed. Due to the rotational motion of a VAWT, the centrifugal force acting on VAWT blade plays an important role on the blade structure characteristics. Reduction of the blade stiffness results in an increase of the blade stress. Changing the strut location from middle to tip will cause a large area under high stress. The results also indicate that the VAWT with a highly flexible blade is not an efficient energy extraction device when it is compared to a less flexible or a rigid blade.
The performance of a wind turbine is directly affected by the site wind condition. In urban-built locality, the wind is typified by fluctuating velocity and direction, and high turbulence intensity (TI). This paper investigates the impact of turbulence intensity on micro wind turbine efficiency in converting the wind energy to power. The performance of bare micro wind turbine (MWT) and diffuser-augmented micro wind turbine (DAMWT) models subject to different level of turbulence intensities is reported. Turbulence intensities ranging from ≈2% to 29% were generated by means of turbulence grids. The turbine performance is assessed in terms of the relationship between the coefficient of performance, CP and tip speed ratio, λ. Computational fluid dynamics (CFD) simulations and wind tunnel tests show that shrouding the turbine with diffuser increases the peak CP by approximately two times. Beyond a certain tip speed ratio, the performance of both MWT and DAMWT is shown to decrease with turbulence intensity, however the Cp of the DAMWT is still greater than bare MWT wind indicating the diffuser augmentation is still achievable even at high level of freestream turbulence.
This paper is about a design of an urban area Darrieus VAWT, having self-start ability due to an innovative profile design named EN0005, avoiding the need of extra components or external electricity feed-in. An approach is presented to study the ability of a blade profile to offer self-start ability. Methodologies applied for the blade body and for profile development are reported. Field tests and main conclusions are presented to persuade for the arrangement of this design.
Combination of Savonius and Darrieus type Vertical Axis Wind Turbine (VAWT) rotors possess many advantages over their individual designs, like low starting torque, high power coefficient, low cut-in wind speed etc. However, there is still a need to do more research on such combination of rotors for their viability in the built environment where wind speed is low. In this paper, an attempt is made to measure the performance of a three-bladed combined Darrieus-Savonius rotor, with Darrieus mounted on top of Savonius rotor, for overlap variations from 10.8% to 25.8%. Power coefficients (Cp) and torque coefficients (Ct) were calculated in a low range of Tip Speed Ratio for each overlap condition. It is found that Cp increases with the increase of overlap. However, there is an optimum value of overlap for which, Cp is maximum, beyond this, Cp starts decreasing. The similar trend is observed for Ct as well. The maximum Cp of 0.53 is obtained at 0.604 Tip Speed Ratio (TSR) for an optimum 16.8% overlap. The performance of the rotor is also compared with another version of this hybrid design with Savonius mounted on top of Darrieus rotor. The present Darrieus-Savonius rotor can be suitably placed in the built environment where it can harness more power from wind and, at the same time, would self-start in low wind condition prevalent in such environment.
A 3D unsteady computational Fluid Dynamics (CFD) model is utilized to investigate the aerodynamics of a combined three-bladed Darrieus Savonius wind rotor. Unsteady Reynolds-averaged Navier–Stokes (RANS) equations of the CFD software are modelled to obtain the fluid flow distributions. In this, initial unsteady effects of the flow interactions are covered to reach to the steady state condition at which the flow physics is analysed. The fluid zone has a large stationary domain and rotating sub-domain connected by a sliding mesh interface. The 3D wake structure of the combined rotor is analysed to understand the physical processes responsible for its power production in low wind speed regime. Steep Coanda like vortices are observed in the rotor wake that migrates from the downstream of Savonius rotor on to the downstream of Darrieus rotor. This effect results into compression of vortices on the downstream of Darrieus rotor thereby pushing the rotor in its rotation, hence augment power production. Presence of attached stall vortices on the Darrieus blades and increased concentration of vortices on the downstream of Darrieus rotor justifies the design of Darrieus rotor on top of Savonius rotor, which could be reflected in high value of power coefficient of the rotor. The outcome of this research would improve the viability of such combined rotor for its use in the built environment.
Wind energy is the most abundantly available clean form of renewable energy in the earth crust. Wind turbines produce electricity by using the power of wind to drive an electric generator. There are two kinds of wind turbines according to the axis of rotation to the ground, horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). VAWTs include both a drag type configuration like Savonius wind turbine and a lift-type configuration like Darrieus wind turbine. Savonius wind rotor has many advantages over others in that its construction is simpler and cheaper. It is independent of the wind direction and has a good starting torque at lower wind speeds. The experimental study conducted in this paper aims to investigate the effect of number of blades on the performance of the model of Savonius type wind turbine. The experiments used to compare 2, 3, and 4 blades wind turbines to show tip speed ratio, torque and power coefficient related with wind speed. A simulation using ANSYS 13.0 software will show pressure distribution of wind turbine. The results of study showed that number of blades influence the performance of wind turbine. Savonius model with three blades has the best performance at high tip speed ratio. The highest tip speed ratio is 0.555 for wind speed of 7 m/s.
To invest the effects of blade surface icing on the aerodynamics performance of the straight-bladed vertical-axis wind turbine (SB-VAWT), wind tunnel tests were carried out on a static straight blade using a simple icing wind tunnel. Firstly, the icing situations on blade surface at some kinds of typical attack angle were observed and recorded under different cold water flow fluxes. Then the iced blade airfoils were combined into a SB-VAWT model with two blades. Numerical simulations were carried out on this model, and the static and dynamic torque coefficients of the model with and without icing were computed. Both the static and dynamic torque coefficients were decreased for the icing effects.
The paper provides an analysis of small wind turbines with less than 10 kW of installed power. Power curves are compared and analyzed for a number of different wind turbines. Furthermore, the possible electricity production is assessed for all of them with their different power curves, same pole heights and wind characteristics using a multiannual array of data measured at a location in Croatia. The impact of the shape of the power curve, together with the turbine rated power relative to its swept area, on the total electricity production and generated income is analyzed and discussed. Results indicate much larger ranges of both potential electricity production and the cost of electricity than expected.
The growth of the world energy demand, the limited fossil fuel reserves and the increasing greenhouse gas emissions require improvements in energy-generation technologies. Specifically, urban wind energy is a source with great potential that is currently being wasted.
The characteristics of urban wind and perspectives and proposals to exploit it have been researched and analysed in the literature. The results show that urban winds have a strong multidirectional component that requires analysing the wind turbine behaviour. To explain the influence of the multidirectional wind on the turbine, a simulation of the air flow around a building section was performed, the sections of various wind turbines were superimposed on the velocity fields, and their aerodynamic behaviour was qualitatively studied.
The results show that horizontal-axis wind turbines have better performance in flat-terrain applications, whereas in high-density building environments, the superiority of vertical-axis wind turbines is demonstrated.
The main benefits of urban wind power development are: distributed power generation, the use of a renewable energy source, and the technological and economic exploitation of building roofs.
Considerable progress has been made, since 1973, in the development of cost-effective wind energy conversion systems, for use in a wide variety of applications in both developed and developing countries. Reviews the current status of the technology, and highlights some representative applications.-from Author
Wind turbine development in Ontario, Canada has been met with opposition yet will likely continue given broader environmental and economic forces. Ontario has ceased the use of coal for electricity generation and the populace has indicated that increased nuclear capacity is undesirable; renewables are a viable alternative. This paper captures experiences with and opinions of wind turbines in politicians and community members to determine which characteristics of development led to acceptance or opposition towards wind turbines, and which changes to policy and decision-making processes may address opposition. A constant-comparison case study, based largely on in-depth interviewing, was conducted with 24 participants who were MPPs, members of local government, and community members. The findings centre on two emergent themes: concerns with current decision-making processes, and options for addressing these concerns though changes to policy and development processes. Key findings were that perceived inequalities (between neighbours, within communities, and within the province) were the main source of opposition related to wind turbines and that future development may be more amenable if partnered with increased compensation or community ownership. Community members were absolutist in their opposition compared to politicians who identified advantages and disadvantages of wind turbines.
The suitability of vertical axis wind turbines (VAWTs) in harnessing energy within a complex wind environment has increased their renewed interest. However, there still exists a huge knowledge gap about the aerodynamic performance of VAWTs operating in a turbulent flow regime. In this paper, an experimental method is presented for a deeper understanding of unsteady rotor aerodynamics under turbulent flow operating conditions. To carry out the investigation, we developed and tested a small-scale Savonius turbine in a wind tunnel. A systematic analysis of torque and power coefficients, including their variations at uniform flow, was also presented to predict the power performance. A mechanism to generate a turbulent flow was then created to analyze the effect of induced turbulence intensity on the aerodynamics and performance of the VAWT. Results revealed that the turbulence of the inflow impacted fluctuating aerodynamic loads on the turbine blade and, ultimately, its aerodynamic performance. In addition, simulations using a CFD code were performed to compare numerical data with experimental measurements. This analysis shows the effect of turbulence intensity on performance of small wind turbines, and the aerodynamics that causes the behavior.
Building augmented wind turbine (BAWT) has been studied numerically. BAWT is a new technology trend to combine wind turbine with building and it has several advantages compared with the conventional stand-alone wind turbine such as minimization of electrical transmission loss and construction cost for the distributed power source and by using existing building. In this paper, a 110 kW horizontal axis wind turbine blade is designed and CFD analysis is carried out with various reference wind speed and flow angle for the 110 kW BAWT. The results show that aerodynamic power output of 110 kW BAWT is higher than that of 110 kW stand-alone wind turbine due to the concentration effect caused by the wind speed acceleration between buildings. Also this kind of advantage appeared in flow angle between −30 ° and 15 °. Due to the fixed rotational direction of the wind turbine, the effect of flow angle shows asymmetric nature. It is also shown that to exceed Betz limit of 0.593 is possible by the effect of buildings similar to the ducts and shrouds. The results of this study can be applied to the research and development of various BAWT and enhancement of energy efficiency of wind turbine.
National targets for increased renewable energy are common-place internationally and small/micro-generation may help achieve such goals. Energy yields from such technologies however, are very location and site specific. In rural environments, the average wind speed is relatively high and the homogeneous landscape promotes laminar air flow and stable (relatively) wind direction. In urban environments however, the wind resource has lower mean wind speeds and increased levels of atmospheric turbulence due to heterogeneous surface forms. This paper discusses the associated costs per unit of electricity generated by micro wind energy conversion systems from the perspective of both urban and rural locations, with three case studies that consider the potential and financial viability for such systems. The case studies ascertain the cost of energy associated with a standard HAWT (horizontal axis wind turbine), in terms of exemplar rural and urban locations. Sri Lanka, Ireland and the UK, are prioritised as countries that have progressive, conservative and ambitious goals respectively towards the integration of micro-generation. LCOE (Levelized cost of energy) analyses in this regard, offers a contextualised viability assessment that is applicable in decision making relating to economic incentive application or in the determination of suitable feed-in tariff rates.
A new approach has been developed for the optimization of Vertical Axis Wind Turbines (VAWTs). The approach is derived from double multiple streamtube theory (DMST) and adopts the concept of “Representative streamtube” wherein the entire aerodynamic property of the VAWT is assumed to be represented by a single streamtube occupying a specific azimuthal location. Five input parameters namely; power, wind velocity, aspect ratio, air viscosity and air density and six output parameters that are minimally required for the construction of a straight bladed, constant pitch VAWT are considered in the study. The discrete data of lift and drag coefficients pertaining to specific values of Reynolds number and angle of attack are arranged in the order of decreasing lift to drag ratio and starting with the first set of coefficients, a check is made if it is eligible to become Representative streamtube for the particular problem. The check is done through a tri-directional “Demand Factor” test that seeks the compatibility of Reynolds number and angle of attack values of the aerofoil data under consideration. The first set which gains the eligibility to become “Representative streamtube” marks the solution for the particular problem.
There is great potential in the use of urban wind energy to form electricity generation modules over a distribution network to maximize wind power production in densely urbanized areas. The objective of this study is to therefore develop computational fluid dynamics (CFD)-based evaluation procedures to determine potential mounting sites of wind turbines and obtain estimates of wind power by taking into consideration the details of the local urban topography and boundary conditions of micro-environments. The predictions, including those of the wind velocity and direction as well as turbulence intensity, are compared with field measurements via ultrasonic anemometers and thermal flow velocity probes at 10 monitored sites over five different floors inside an objective building to validate the computational model as well as attain a better understanding of the interaction of the wind with buildings in a complex terrain. The predicted power density and turbulence intensity profiles are then used to analyze the power density, turbulence intensity and lowest mounting height for optimizing the potential mounting sites and estimates of wind power. The suggested deployment solution of using CFD for wind turbines on the studied site is clearly different from those suggested in the literature and their deficiency in providing optimum mounting sites in micro-environments. Moreover, an improved roof design with a rounded shape is proposed for the enhancement of wind power density with relatively lower turbulence intensity.
This paper provides a comprehensive, critical review of turbulence observations over cities. More than fifty studies are analysed with their experimental conditions summarized in an appendix. The main results are based on 14 high-quality experiments which met criteria based on stringent experimental requirements. The observations are presented as nan-dimensional statistics to facilitate comparison between urban studies and work conducted over other rough, inhomogeneous surfaces. Wake production associated with bluff bodies, and the inhomogeneous distribution of sources and sinks of scalars, result in a roughness sub-layer which for the studies reviewed extends to about 2.5 to 3 times the height of the buildings. It is shown that within this region the basis of several traditional micrometeorological approaches to describe the turbulent exchange is in doubt. There are strong similarities to flow over plant canopies, and many of the turbulence characteristics can be interpreted in the framework of a plane mixing layer. Future field observations should concentrate on the turbulent exchange near the top and within the urban canopy as well as within the urban boundary layer.
Global warming, fossil fuel diminishing, climate change disaster and along with more energy demand underscore the increasing value of renewable energy implementation. Energy is an important factor for countries to achieve sustainable development. Therefore, government need to actively seek renewable energy technology innovations, assess for optimization of resource inputs and strategize to proceed with effective energy strategic planning. Wind is an alternative clean source of energy compared to fossil fuel. Taiwan is highly vulnerable in energy security, but geographic conditions for the development of wind energy applications have created a considerable advantage. However, the total installed small wind energy capacity is far less than might be expected. Consequently, this study proceeds to explore the main resistance and key factors that affect small wind energy systems application in Taiwan. Through the evaluation decision-making system model and expert groups giving evaluation values and feedback, the study found the main influences factors, and propose strategies for energy development in future to improve the quality and quantity of renewable energy applications and energy competitiveness, also provides countries access to applications of wind energy technology assessment and forecasts in the future.
In this paper, the power performance of straight-bladed VAWT is experimentally investigated by wind tunnel experiment and field test. The test rotor is two-bladed with NACA0021 airfoil profile. A survey of varying unsteady wind parameters is conducted to examine the effects of blade pitch angle, Reynolds number and wind velocity on the power performance of VAWT. Moreover, the flow field characteristics are obtained through measuring the wind velocity by Laser Doppler Velocimeter (LDV) system in the wind tunnel experiment and three-cup type anemometers in field test. Power and torque performance are obtained through a torque meter installed in rotor shaft of the wind turbine. Experimental results estimated from the measured values from field test and wind tunnel experiment are compared. In this research, power performance and flow field characteristics are discussed and the relationship between operating conditions and wind velocity are verified. These results provided a theoretical guiding significance to the development of VAWT simplified.
In response to the gradual degradation of the natural environment, there is a growing interest to advance the development of sustainable buildings, in which renewable energy technologies are often incorporated to strategically minimize the carbon footprint of buildings. Pearl River Tower, a 71-storey tall building in Guangzhou, China, was designed to be the most energy efficient tall building in the world. In addition to a series of energy-efficient measures, the most eye-catching innovation in the design of Pearl River Tower is the deployment of four wind turbines installed in four openings in the tall building for power generation. This study aims to provide a performance assessment of these tall building-integrated wind turbines. At the first step, a 1:150 scaled wind tunnel testing is carried out to experimentally assess the wind speed amplification effects inside the four openings. Comparative analysis and discussions corresponding to four different cases are presented. At the second step, the results from the wind tunnel testing, in conjunction with the statistical analysis results of long-term meteorological wind data recorded in Guangzhou, are applied for the performance assessment of these wind turbines for power generation. The outcomes of this study are expected to provide useful information for architects and engineers involved in the design of sustainable tall buildings.
In highly urbanized and energy intensive countries like Singapore all possible avenues for power generation need attention. In this context, rooftop installations of both solar and wind energy are of particular interest for Singapore, especially because of Singapore's condition of land limitation. Decentralized and distributed energy sources such as rooftop wind and solar installations have numerous advantages. However, the potential for wind energy is not fully understood in built-up areas and thus not fully exploited. Hence it is important to study wind flow patterns in built-up areas and also develop technologies tuned for these conditions. The demand for technologies that deliver energy for low flow wind conditions is of paramount importance to Southeast Asia region and especially to Singapore. In this paper, two measurement systems, namely stationary rooftop wind mast and mobile Light Detection and Ranging (LiDAR) profiler, have been discussed. Measured wind data from various sites across Singapore using have also been presented. Wind roses, Weibull distribution, roughness lengths and other statistical analyses were carried out to understand the prevailing wind characteristic, which is used for evolving the basic criteria for economic viability of roof top wind turbines in the tropical conditions of Singapore.
Increasingly, there is a focus on utilising renewable energy resources in a bid to fulfil increasing energy requirements and mitigate the climate change impacts of fossil fuels. While most renewable resources are free, the technology used to usefully convert such resources is not and there is an increasing focus on improving the conversion economy and efficiency. To this end, advanced control technology can have a significant impact and is already a relatively mature technology for wind turbines. Though wave energy systems are still in their infancy, significant benefits have been shown to accrue from the appropriate use of control technology. To date, the application communities connected with wind and wave energy have had little communication, resulting in little cross fertilisation of control ideas and experience, particularly from the more mature wind area to wave. This paper examines the application of control technology across both domains, both from a comparative and contrasting point of view, with the aim of identifying commonalities in control objectives and potential solutions. Key comparative reference points include the articulation of the stochastic resource models, specification of control objectives, development of realistic device models, and development of solution concepts. Not least, in terms of realistic system requirements are the set of physical and legislative constraints under which such renewable energy systems must operate, and the need to provide reliable and fault-tolerant control solutions, which respect the often remote and relatively inaccessible location of many offshore deployments.
A transition towards low-carbon energy sources, such as wind, requires higher levels of public interaction; as such, the ultimate contribution of wind energy relies as much on technological advancements and policies as on societal sentiments. This study evaluates the influence of region, community involvement, and several IEA-recommended practices on social acceptance of wind energy projects among residents (n = 350) surveyed from cities in four OECD and three non-OECD countries. The results indicate interurban variations among the generally high levels of acceptance reported, especially among residents of cities in developing countries with lower domestic CO2 emissions. The level of community involvement in a hypothetical wind energy project had a positive effect on acceptance, and respondents from cities in countries with the highest installed wind capacity reported the greatest sensitivity towards involvement. Moreover, the results revealed that although the IEA-recommended practices collectively predicted acceptance across all cities, fair distribution of earnings and costs was the only significant individual predictor. These economic considerations, combined with increased community involvement, appear to be paramount to facilitating future development of wind energy. Through its broad geographical coverage, this research provides valuable groundwork for future cross-cultural studies on social acceptance of wind energy.
Energy is an essential ingredient for socio-economic development and economic growth of a country. Energy is available in two different forms, fast depleting or non-renewable (coal, fuel, natural gas) and renewable (solar, wind, hydro etc). Wind is one of the potential renewable energy sources due to its abundance in the atmosphere in different scales of high, medium and low ranges. Vertical axis wind turbine (VAWT) can be installed in low wind speed regime for performing various small-scale functions ranging from electrifying a built environment to pumping water especially in remote places where grid-connected electricity is a scarce. Amongst various VAWT rotors, H-type Darrieus rotor has become more popular in the built environment for their straight blade designs and simpler construction features. However, the major problem facing such VAWT rotor is their non-self-starting characteristics due to symmetrical blade designs. Replacing VAWT's conventional blades with unsymmetrical blades and increasing rotor solidity could make potential solution to the above problem. However, there is still hardly any quantitative measure of the self-starting, torque, power coefficient etc. with increased rotor solidity so as to obtain some performance insights of high solidity unsymmetrical blade H-Darrieus rotor in low wind speed condition. In this paper a three-bladed H-type Darrieus rotor equipped with unsymmetrical S1210 blades is investigated first for its self-starting characteristics with different rotor solidities (from 0.8 to 1.2) at various azimuthal positions. Then the power coefficients (Cp) are evaluated for these solidities at various wind speeds. It will be shown that high blade solidity is in fact desirable for overall better performance of the rotor. There is an optimum rotor solidity at which power coefficient is the highest. And the maximum Cp of 0.32 is obtained for rotor solidity 1.0 and wind speed 5.7 m/s. The results are compared with some other symmetrical/unsymmetrical blade H-Darrieus rotors. Though the operating range is reduced but, for higher static and dynamic torque and comparable power coefficient with respect to existing rotors, the present rotor could be used for various small-scale applications especially that require high torque like pumping, grinding etc.
To help design wind turbines around numerous high-rise buildings with promising wind in Hong Kong, this paper presents an integrated method of both macro (weather data and domain topography) and micro aspect (Computational Fluid Dynamics, CFD) analysis. Long-term wind data are compared at dense urban and small island stations. The prevailing wind is found to be from the East, and the average wind speed for the urban location is much lower, say 2.93 m/s at 25 m above ground level. The need to integrate wind turbines into high-rise buildings is necessary. This research demonstrates that the wind power density at 4 m above the building roof is enhanced numerously by 1.3-5.4 times with 5-7 m/s inlet velocity. Wind power utilization around the windward top roof is the most promising under the dominant wind direction. The thickness of wind speed below 8 m/s is only 3.6 m at these areas. Due to high-rise building height and concentration effects, the wind power enhancement for 7 m/s inlet velocity is around 4 times of that for 5 m/s, which is even larger than the cube of these two velocity ratio 7/5, i.e. 2.7 times determined from the general model between wind power and velocity.
The techno-economic performance of a small wind turbine is very sensitive to the available wind resource. However, due to financial and practical constraints installers rely on low resolution wind speed databases to assess a potential site. This study investigates whether the two site assessment tools currently used in the UK, NOABL or the Energy Saving Trust wind speed estimator, are accurate enough to estimate the techno-economic performance of a small wind turbine. Both the tools tend to overestimate the wind speed, with a mean error of 23% and 18% for the NOABL and Energy Saving Trust tool respectively. A techno-economic assessment of 33 small wind turbines at each site has shown that these errors can have a significant impact on the estimated load factor of an installation. Consequently, site/turbine combinations which are not economically viable can be predicted to be viable. Furthermore, both models tend to underestimate the wind resource at relatively high wind speed sites, this can lead to missed opportunities as economically viable turbine/site combinations are predicted to be non-viable. These results show that a better understanding of the local wind resource is a required to make small wind turbines a viable technology in the UK.
In this paper we investigate the location-specific attractiveness of small wind turbines (SWT) for private households. In order to assess the economic viability of an investment in SWT, we analyze a set of scenarios that incorporate different types of SWT, various storage system options, support schemes, and specific urban surroundings for the case of Germany. As urban structures substantially influence local wind speeds, and hence the potential energy yield of a turbine, the location of SWT in the urban area is crucial for their economic feasibility. We find that SWT today are only profitable under very favorable conditions, the most important parameters being prevailing wind speeds and the location's degree of urbanization. In most cases, the coupling of the SWT to a storage system is crucial for cost-effectiveness. A feed-in tariff system specifically adapted to SWT technology is found to be an important driver of diffusion. Further research needs are identified in the field of long-term performance and yield projections for SWT. Based on the findings from our study, significant SWT diffusion can only be expected, if at all, in coastal suburban and rural areas.
Decentralised energy sources, such as small-scale-wind energy, have a number of well-known advantages. However, within urban areas, the potential for energy generation from the wind is not currently fully utilised. One of the most significant reasons for this is that the complexity of air flows within the urban boundary layer makes accurate predictions of the wind resource difficult to achieve. Without sufficiently accurate methods of predicting this resource, there is a danger that wind turbines will either be installed at unsuitable locations or that many viable sites will be overlooked. In this paper, we compare the accuracy of three different analytical methodologies for predicting above-roof mean wind speeds across a number of UK cities. The first is based upon a methodology developed by the UK Meteorological Office. We then implement two more complex methods which utilise maps of surface aerodynamic parameters derived from detailed building data. The predictions are compared with measured mean wind speeds from a wide variety of UK urban locations. The results show that the methodologies are generally more accurate when more complexity is used in the approach, particularly for the sites which are well exposed to the wind. The best agreement with measured data is achieved when the influence of wind direction is thoroughly considered and aerodynamic parameters are derived from detailed building data. However, some uncertainties in the building data add to the errors inherent within the methodologies. Consequently, it is suggested that a detailed description of both the shapes and heights of the local building roofs is required to maximise the accuracy of wind speed predictions.
In this work three methods of controlling the wind direction were aiming at improving the performance of Savonius rotor. The idea behind the new designs was to harvest the incoming wind to generate a wind jet to the concave side of the advanced blade and prevent the convex side of return blade from coming upwind stream. The prevented wind was guided in different designs to impinge the concave side of the return blade and hence to eliminate the negative torque and increase the exerted positive torque. The study could be numerically introduced using commercial Fluent-software. The SST k-ω turbulence model was used to simulate the turbulence behavior. The results showed that the suggested designs improve the performance of Savonius rotor in view of the power coefficient and the operation range. One of them enhanced the performance to reach a power-coefficient peak of 0.52 with operation range of tip speed ratio. However, the new designs generated large wakes behind the rotor that must be considered in the turbines farm arrangement.
Horizontal axis wind turbines (HAWTs) are the mainstream of wind power industry in the world; however, as turbines are becoming bigger, the maintenance of equipments grows more complex and costs much higher. Compared with HAWTs, Darrieus vertical axis wind turbines (VAWTs) have more technological advantages, providing an alternative for the wind power technology; hence Darrieus VAWTs are catching more eyes. Nevertheless, the majority of wind turbine design currently focuses on HAWTs, researches on Darrieus VAWTs have lagged significantly behind those on HAWTs, which have greatly hindered the development of VAWTs. Accordingly, this paper reviews the main basic research methods and their corresponding applications in Darrieus VAWTs, aiming to let more experts know the current research status and also provide some guidance for relevant researches.
Wind tunnel experiments have been conducted with a newly developed two-bladed Savonius-style wind turbine specifically meant for a small-scale energy conversion. This novel shape of the turbine blade is evolved from a series of experiments with different types of blades in the recent past. The developed two-bladed turbine is tested in an open type test section and its performance is assessed in terms of power and torque coefficients. Experiments have also been conducted with other standard blades such as semi-circular, semi-elliptic, Benesh and Bach types in order to have a direct comparison. In this study, all the reported experimental data are inclusive of wind tunnel blockage corrections. Further, the effects of Reynolds number on the dynamic and static characteristics are also discussed. The present investigation demonstrates a gain of 34.8% in maximum power coefficient with the newly developed two-bladed turbine.
Abstract The urban terrain and the associated morphological complexities therein, present significant challenges for the deployment of small wind turbines. In particular, a considerable amount of uncertainty is attributable to the lack of understanding concerning how turbulence within urban environments affects turbine productivity. Current wind turbine power output measurements (particularly for small/micro wind turbines) are based on an average wind speed over an observation period; with limited accountability of the variability of wind speed within the observation time frame. This paper however, presents two models that can instead accurately consider such wind speed variation and how it affects the turbine, based solely on the observed mean wind speed and standard deviation within successive (10 min) time intervals. These models are predicated on an appreciation of the industry standard metric, turbulence intensity (TI), in conjunction with the power curve of a 2.5 kW wind turbine. Simple ‘look-up’ tables collating how the turbine's power curve is affected by varying TI are used so that a novel methodology for estimating the turbine's electrical performance is achievable. Ultimately, the two models presented afford an opportunity to provide an indicative real-world wind speed distribution based on the two standard measurements. The first approach is an adaptation of a model originally derived to quantify the degradation of power performance of wind farm turbines, using a Gaussian probability distribution to simulate turbulence (and more specifically, turbulence intensity (TI)). Such Gaussian modelling has potential however, for disproportionately high and asymptotic TI, associated, for example, with gusting within low mean wind speed observation windows. Furthermore, the approach requires an accurate turbine power curve. The second approach overcomes these limitations through the novel application of the Weibull Distribution, a widely accepted means to probabilistically describe wind speed. Both models are tested at an urban and suburban location in Dublin City, Ireland, where sonic anemometry is positioned at approximately 1.5 times the average height of buildings at the respective locations. Both observation sites represent two distinct urban landscapes. The instrumentation is positioned specific to their surrounding locations and, record the three dimensional wind vectors at a temporal resolution of 10 Hz. The hypotheses presented here consider an idealised electrical performance of the turbine, with results suggesting that both approaches can replicate very accurately this idealised basis.
A review on a wide number of different aerodynamic coefficient databases to be used for vertical axis wind turbine simulations is conducted in this work. The databases are adopted in conjunction with a Blade Element-Momentum algorithm, a commonly used tool to design and verify the aerodynamic behaviour of these machines. Experimental data derived from field test available in the literature for a wide range of rotor sizes are considered and compared to the simulation results. The aerodynamic databases provide strongly different estimations due to the different working conditions: in each case suggestions on their use are provided based on their reliability. Finally, resuming all the conducted validations, practical general considerations are proposed to the wind turbine designer to conduct reliable simulations.
This paper presents a review of existing and emerging wind power technologies in light of the evident trends of the industry, and describes the challenges these technologies will face if wind turbines were to become a significant and reliable source of clean energy of the future. Apart from withstanding both the cost pressures against other forms of renewable and non-renewable technologies and the technical and design challenges for efficient and enhanced performance under all weather conditions, a major hurdle that must be overcome is to make the wind farms acceptable to the general public. Although there is now a greater awareness amongst world population about the perils of climate change, the issue of wind turbine generated noise, land use, fauna deaths and visual impacts have to be adequately addressed to ensure continued political and public support for the technology to flourish. These are the viewpoints against which emerging technologies are reviewed and the capacity of some of them to address these issues explored.
This study investigates the effects of parameters such as a blade profile (changing the digit of the 4-digit NACA00xx airfoil), the Reynolds number, and the solidity on the performance characteristics of a straight bladed vertical axis wind turbine (VAWT). A numerical analysis, adopting the multiple stream tube (MST) method, is carried out to evaluate the performance depending on the parameters. The numerical result shows that the variation of a blade profile directly influences the power production, i.e., the high-digit NACA00xx airfoil provides higher power in a low speed zone (BSR < 3; BSR: blade speed ratio (ΩR/U
f
), Ω: angular velocity of blade, R: radius of a straight Darrieus wind turbine, U
f
: free stream velocity) than the low-digit NACA00xx profile. On the contrary, the low-digit NACA00xx airfoil produces higher power in a high speed range (BSR > 5) than the high-digit NACA00xx profile. An enhancement of the power production is observed with increasing the Reynolds number on the whole tested blade speed ratio range (1 < BSR < 12). In particular, the rate of the enhancement of the power is rapidly decreased with the increases of the Reynolds number (Re = {{\rho \bar U_r c} \mathord{\left/ {\vphantom {{\rho \bar U_r c} \mu }} \right. \kern-\nulldelimiterspace} \mu }, ρ: air density, : mean resultant velocity acting on a blade with variable rotating speeds in a uniform free stream velocity (U
f
), c: blade chord length, µ: air viscosity). For the effect of the solidity on the power production, a marked reduction of the range of the blade speed ratio that can provide the power is observed with increasing the solidity. A pattern of very steep variation of the power around the peak in the low speed zone (BSR < 3) is found in a high solidity range (σ > 0.3; σ: solidity (N
c
/R), N: number of blade, c: chord length of an airfoil), and this tendency is conspicuously different from that of the eggbeater-type Darrieus VAWT, which is interpreted as a gradual variation of the power around the peak.
To maximize uptake of micro renewable-energy generation, specifically small wind-turbines, it is crucial to permit for tower heights which allow maximum utilization of the available wind resource. Within New Zealand, municipal governments have authority to place limitations on the height of built structures in rural areas, including wind turbines.
Numerical simulations using Computational Fluid Dynamics (CFD) are used to examine the effects of simple house shapes and heights on the characteristics of the air flow reaching wind turbines. Within New Zealand, municipal governments have authority to place limitations on the height of built structures in rural areas, including wind turbines. However at present they have insufficient information to understand which height limitations may decrease wind-resource utilisation by small wind-turbines installed in these areas. This research finds that current permitted structure heights are not sufficiently high, necessitating either lengthy planning consent processes or acceptance of sub-optimal turbine output. Municipal councils in New Zealand could reduce barriers to small wind-turbine installations by considering taller towers, in the 15–20 m range, acceptable. This 15–20 m range is transferrable to all rural areas, in other developed or developing countries, where a lone small turbine or small number of small wind-turbines are being considered for installation near dwellings.