No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Wind tunnel experiments of a newly developed two-bladed Savonius-style wind turbine
Abstract
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.
... It was demonstrated that the modified Bachtype rotor with a power coefficient of 0.304 had more efficiency than the conventional and Benesh types. Roy and Saha (2015) introduced a new shape for blades of the Savonius rotor. They showed that the proposed rotor produced 31.6% more torque than the model with conventional blades. ...
... Therefore, this study has been formed to improve such existing gaps in previous studies. Some previous studies regarding the Savonius wind turbines (Alom and Saha 2019;Kumar et al. 2020;Roy and Saha 2015) revealed that the Bach-type rotor had better efficiency than the conventional Savonius rotor made by semicircle blades, which has been the main motivation of this investigation. In this way, the effects of several variables such as the attachment angle, TSR, and wind speed are examined and discussed in detail to present the optimum case among the under consideration models. ...
... The external Darrieus rotor is made with two symmetrical airfoils of NACA0018, which has been applied in several studies (Mohamed 2012;Mohamed, Dessoky, and Alqurashi 2019;Song et al. 2020). On the other hand, the Bach-type blades, which have better performance than conventional semicircle ones (Alom and Saha 2019;Kumar et al. 2020;Roy and Saha 2015) have been considered for internal rotor. The diameter ratio (D 2 /D 1 ), is set as 0.2, based on the available data (Saini and Saini 2018) at which "D 1 " and "D 2 " are the diameters of external and internal rotors, respectively. ...
... Roy et al. [13] conducted wind tunnel experiments on a newly developed blade profile for a Savonius wind turbine as shown in Fig. 4. They also studied a variety of blade profiles (conventional semi-circular ( Fig. 5 (a)), semi-elliptic ( Fig. 5 (b)), Benesh (Fig. 5 (c)), and Bach ( Fig. 5 (d)) shapes as displayed in Fig. 5. Comparing the results, the newly developed type, shown in Fig. 4, was reported to have an improvement in the maximum power coefficient by 3.3% over the modified Bach; 6.9% over the Benesh; 19.2% over the semi-elliptical; and 34.8% over the conventional Savonius wind turbine. ...
... They also reported that the newly developed blade profile of the wind turbine has an improvement in the starting performance as well as overcoming the negative torque effects. As for the static torque coefficient, it was shown to have increased by 31.6%, 22.0%, 11.1%, and 4.2% for the newly developed design when compared to the conventional, semi-elliptical, Benesh, and modified Bach type blade profile [13]. Numerically, Gad et al. [14] studied different blade shapes, in addition to V-shape blade curvatures expressed, in Table 1, as polynomials. ...
... Second, increasing the angle of twist beyond the optimal one will cause a decrease in the energy captured by the lower part of the blade which correspondingly causes a decrease in the net positive moment [16]. [13]. ...
Wind turbines are devices that convert the kinetic energy present in the wind into clean, sustainable, and effectively renewable energy that could be used to generate electricity. A Savonius wind turbine is a drag-based vertical axis wind turbine (VAWT) that is known to have low noise levels and good starting characteristics even at low wind speeds. Its disadvantage lies in its low efficiency or low coefficient of performance. Exploring ways to increase the coefficient of performance, numerical investigations were carried out on different modified Savonius VAWT configurations, having different curvatures, different overlap percentages, added mini blades, and fitted out with extended surfaces. These investigations were computationally executed on Ansys Fluent™ using the sliding mesh technique. Two-dimensional simulations, on a Bach blade curvature with zero overlap as well as a half-circle and a polynomial curvature with overlap, showed that for a wind speed of 5 m/s and a tip speed ratio of 0.8, the half-circle blade curvature having an overlap of 20% performs best, yielding the highest net (average) coefficient of moment, equal to 0.3065. Results also show that the addition of mini blades to this optimal configuration produces a slight improvement in the coefficient of moment. However, the addition of extended surfaces onto the blades caused the minimum coefficient of moment to be a substantial negative value and thus resulting in a much lower value for the turbine's average coefficient of moment.
... A. Eltayesh et al. Experimental data at different Reynolds numbers, based on the free stream velocity and the diameter of the rotor, for the selected Savonius turbine at zero attachment angle are available in Roy and Saha (2015). Their results for the torque coefficients versus TSR at different Reynolds numbers are shown in Fig. 5. Above 0.6 TSR, the relation between the torque coefficient, , versus TSR is almost linear for all the plotted Reynolds numbers, and all the -TSR curves are almost parallel to each other. ...
... The two datasets by Roy and Saha (2015) corresponding to the upper and lower limits of Reynolds number are used to derive the correlation between and TSR as a function of Re, using the following equation where the -axis intercept is derived as a function of Re: ...
... The correlation is further validated at Re = 1.0 × 10 5 for the torque and power coefficients in Fig. 6, which shows as the function above reliably match the experimental data (Roy & Saha, 2015). ...
Wind energy conversion is contributing significantly to the new clean energy transition but, up to now, such contribution is mainly driven by large multi-MW windfarms. On the other hand, the recent needs in terms of distributed energy production are revealing a new interest in small-scale wind energy conversion technologies for residential and urban applications. In this context, vertical axis wind turbines (VAWT) are often the most valid choice from the point of view of building integrating possibilities, but it is well known that they suffer a considerable gap in performance when compared to horizontal axis technologies. Based on these premises, in the present work some innovative solutions for improving the performance of a Darrieus vertical axis wind turbine are investigated through numerical and engineering approaches. The investigated interventions include
rotor hybridization by the use of an inner Savonius section for improving the machine’s start-up and the possible application of dimples for improving the NACA 0021 airfoil performances on the outer rotor section. Results demonstrate the effectiveness of the interventions in obtaining a rotor with stable performances in a
very wide range of wind regimes.
... As a result, many novel blade shapes are developed, such as Bach-type, Benesh type, modified Bach-type, elliptical, arc elliptical blades, and others, which have shown varying degrees of performance superiority over the conventional semicircular blade shape [6]. Among them, Bach-type blade exhibits a high C P values only in the range of lower λ [7], while the other blades like arc elliptical and modified Bach have demonstrated consistent improvement of C P over the entire range of λ [8,9]. Further, in the pursuit of finding a superior blade shape, researchers have also explored new directions by using (a) shape optimization with the help of numerical optimization techniques, (b) different aerodynamic shapes that are already prevalent, and (c) new bio-inspired/ biomimetic shapes. ...
... Since the present investigation is aimed toward the performance of sea pen blade, the resulting corrugated shape due to polyps is not considered. The set of xy coordinates is then curve fitted with polynomial (R 2 = 0.9988) as expressed by Eq. (9). It is important to note that the overlapped edges of leaves cannot be detected, i.e., edges between points 2 and 3 for the selected leaf; however, the polynomial fitting can approximately interpolate in this region. ...
... Once the xy coordinates of the sea pen curve are estimated, it can also be scaled up or down as per the need of rotor fabrication. A sea pen curve is compared with other reported blade shapes, e.g., Bach, arc elliptical, and semicircular, in Fig. 6 with a 1:1 scale [9,22]. It is observed that the curvature of the sea pen blade falls in between Bach-type and arc elliptical blades. ...
Inspired by the polyp leaf of the Orange sea-pen (Ptilosarcus gurneyi), a novel blade shape of the Savonius vertical-axis wind rotor is developed. The similarities between the aerodynamic and the hydrodynamic aspects of the Savonius rotor blade profile and the sea-pen leaf are reviewed, and an appropriate analogy is thereby established. The shape of the sea-pen leaf is then extracted to fabricate the rotor blades. The performance of this sea-pen bladed rotor is evaluated in a low-speed subsonic wind tunnel at different wind velocities. The two-dimensional (2D) numerical analysis is also performed to support the experimental findings and to study the influence of blade shape on the pressure and the torque distributions of the rotor. The novel sea-pen bladed rotor, having lesser material requirements, is seen to demonstrate higher performance than that of the conventional semicircular bladed rotor in the tested range of low tip-speed ratio.
... However, above TSR 1.0, the incoming free stream velocity dominates the rotor's rotational speed, resulting in a lifting effect. Hence, the reported optimal operational TSR range for the SSWT is in the range of TSR 0.72 to TSR 0.82 [3][4][5][6]. ...
... In the second stage, an SSWT was constructed in Solidworks by adopting the blade coordinates obtained from the work of Roy and Saha [3]. The blade profile was restructured to a diameter of 0.21m (D). ...
... TSR 0.2, TSR 0.4, TSR 0.6, TSR 0.8, TSR 1.2) were likewise validated using the minimum number of elements allowed. The outcome of the numerical analysis was plotted in figure 3, where the present simulation results were verified against previous numerical and experimental works conducted by Roy and Saha [3] and Roy and Ducoin [13]. The result of the present study agrees with the values reported in the previous studies. ...
With the uprise in global population and rapid industrialisation in developing nations, increasing energy demand to compensate for societal and industrial needs is inevitable. However, popular energy resources such as gas, petroleum, and coal, on which the global energy mix is heavily reliant, induce environmental pollution and global warming. Thus, clean energy sources, such as wind and solar, are increasingly sought to mitigate these adverse environmental effects and identify alternative sustainable and renewable energy technologies. The existing literature suggests minimal research has been conducted on the turbine component of the solar chimney power plant (SCPP). The present research proposes the study of a vertical axis wind turbine (VAWT), namely the Savonius-style wind turbine (SSWT), for power augmentation in the SCPP under the influence of guide vanes and shields that are installed in the solar collector area. A two-dimensional numerical analysis is performed using the ANSYS Fluent software. The SSWT and SCPP models used in the simulations were validated using numerical and experimental results from previous literature data. The angle of the guide vanes was varied while the dimensions of the SCPP model and the energy extractor considered were kept constant. The optimum turbine performance was identified based on the flow analysis and the power output of the rotary component from different guide vane configurations. The present study shows an overall improvement in the turbine’s performance coefficient and power output under the influence of the guide vane and shield in the SCPP. The turbine with the guide vane and shield at an angle of 45° enhanced the performance by 22.22% and power output by 22.25% compared to the turbine without the guide vane and shield.
... Various techniques have been proposed for increasing the rotor performance by either using blockage (Mohamed, Faris, and Thévenin 2021;Ramadan et al. 2021;Salleh et al. 2021;Storti et al. 2019) or modifying the blade profile (Bach 1931;Blackwell, Sheldahl, and Feltz 1978;Kamoji, Kedare, and Prabhu 2009;Kacprzak, Grzegorz, and Krzysztof 2013;Al Faruk and Sharifian 2014;Roy and Saha 2015;Tartuferi et al. 2015;Sharma and Sharma 2016;Lee, Lee, and Lim 2016;Zhang et al. 2017;Chan, Bai, and He 2018;Tian et al. 2018;Saeed, Elmekawy, and Kassab 2019;Kerikous and Thevenin 2019;Elmekawy, Saeed, and Kassab 2021;Anh et al. 2022a and b). Among these, the latter technique is a promising solution with a huge performance improvement but still keeps the omnidirectional and compact features of the conventional Savonius turbine. ...
... Among these, the latter technique is a promising solution with a huge performance improvement but still keeps the omnidirectional and compact features of the conventional Savonius turbine. Several blade configurations have been proposed either by experiment or computational approaches, including multiple blades (Sharma and Sharma 2016), overlapping blades (Al Faruk and Sharifian 2014;Blackwell, Sheldahl, and Feltz 1978), Bach-type blades (Bach 1931;Kacprzak, Grzegorz, and Krzysztof 2013;Kamoji, Kedare, and Prabhu 2009), Benesh type blade (Roy and Saha 2015), multicurve and elliptic blades (Banerjee et al. 2014;Chan, Bai, and He 2018;Elmekawy, Saeed, and Kassab 2021;Kaya and Acir 2022;Zhang et al. 2017), multi-thickness blade (Kerikous and Thevenin 2019;Saeed, Elmekawy, and Kassab 2019;Tian et al. 2018), twisted blade (Lee, Lee, and Lim 2016), and the blade with airfoils shape (Tartuferi et al. 2015) or with auxiliary profile (Anh et al. 2022a, b). Depending on the optimization profile, the power coefficient C p of the rotor can increase by several to a hundred percent. ...
This study proposes a novel blade configuration, made with a multicurve profile, to further maximize the advanced benefits and the performance of a Savonius turbine for energy harvesting applications. The advantages of the presently designed blade are proved by a detailed analysis of the flow mechanism and the performance through a sequence of two-dimensional (2D) unsteady computational fluid dynamics simulation. The remarkable finding states that the main blade section with a length ratio of 0.9 combined with an elliptical auxiliary section effectively enhances the positive wind flow phenomena around the blade, especially for the returning position, which either smooths the flow or reduces the pressure on the blade’s convex side. As a result, greater torque is obtained by the present configuration, responding to the improvement of the power generation to 0.24 – about 5.5% at the low TSR = 0.8 and up to 0.28 - about 185% at the high TSR = 1.5 over the conventional configurations. The effectiveness of the presently designed blade is further proved with more than 20% improvement in self-staring speed through six degrees of freedom analysis. The results above state a high potential application of the turbine with the presently designed blade for renewable energy applications and for supporting vulnerable communities without access to electricity.
... The elliptical Savonius rotor performed better than the Bach-type and the classical Savonius rotor in the range of tip speed ratio between 0.2 and o.4 [7]. Roy and Saha et al. [8] studied different types of blades including semi-circular, semi-elliptic, Benesh, and Bach types. It was found that the torque and power coefficients and are higher for their newly developed blade profiles. ...
... Four ball bearings (SKF)(6) are mounted in the steel housing in order to make rotating smoothly of the Savonius rotor. The bearing is fixed with the structure housing, weighing pan(7), torque meter(8), and nylon string(9)of 1 mm diameter. The mechanical torque in (N. ...
... Various works have also been done on performance improvement of the Savonius turbine by modifying its blade profile, for example using elliptical blades, helical shape blades, twisted blades, hybrid blade sections for both wind and water applications [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. For generating more thrust, maximum blade surface area should be in contact with the working fluid as the case with helical and twist bladed Savonius wind turbines [33] investigated on a modified Bach-type Savonius turbine and found improvement in performance and other characteristics like lift and drag as compared to conventional Savonius turbine. ...
... Various works have also been done on performance improvement of the Savonius turbine by modifying its blade profile, for example using elliptical blades, helical shape blades, twisted blades, hybrid blade sections for both wind and water applications [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. For generating more thrust, maximum blade surface area should be in contact with the working fluid as the case with helical and twist bladed Savonius wind turbines [33] investigated on a modified Bach-type Savonius turbine and found improvement in performance and other characteristics like lift and drag as compared to conventional Savonius turbine. Study based on height effect of water on Savonius turbine has been done by [41] who obtained maximum coefficient of power ( C p ) of 0.19 at a tip speed ratio (TSR) of 3. Further, performance improvement has been done by modifying the aspect ratio, overlap ratio, gap width ratio and solidity of this turbine [42] and [43]. ...
The objective of the present study is harnessing hydropower by combining lift and drag-based blades in a proposed Savonius vertical axis water turbine design and analyzing its hydrodynamic performance. It is a two-bladed design with each blade having two different blade sections—an airfoil blade section for harnessing lift force and a straight blade section for harnessing drag force. The detailed hydrodynamic performance of the proposed turbine has been investigated through flow physics study for various water speeds and azimuthal angles. For more exploration of the turbine performance, the effect of the overlap ratio in the straight blade section has been studied. The performance of the proposed combined lift and drag (CLD) turbine is optimal at overlap ratio 19.21%, water velocity 0.7 m/s, in which a maximum \({C}_{p}\) of 0.139 is obtained at a tip speed ratio 0.6 with a maximum hydrodynamic torque of 0.832 N m, obtained at 135° azimuthal position.
... The present work adopts a two-dimensional numerical analysis approach using SOLIDWORKS and ANSYS R3 for the SSWT validation, SCPP validation and combined investigations. The SSWT and SCPP validations were verified using previous numerical work and experimental data [13][14][15]. The fluid flow characteristics, such as pressure and velocity data, were extracted from the verified SCPP model and applied on the SSWT domain to analyse the performance of the SSWT in the SCPP at various turbine rotational speeds. ...
... The novel turbine geometry is adopted from the work of Roy and Saha [13], where the coordinates of the blade profile are reconstructed to a diameter of 0.25 m using SOLIDWORKS. A two-dimensional approach is taken to study the performance of the SSWT using ANSYS Fluent, where the SST k-omega turbulence model is adopted for a more accurate prediction of the flow separation and adverse pressure gradient. ...
The increase in global population has caused a higher demand for energy be it for the upsurge in industrialization or daily consumption. Nevertheless, the high levels of carbon emissions from major energy resources such as coal, petroleum and gas are alarming as repercussions through rising sea levels are posing a threat to modern civilization. Thus, renewable energy sources such as wind energy and solar energy are being ventured into as these natural resources cause minimal to no harm to the environment. Previous literature suggests that minimal studies are performed on the enhancement of the turbine component of the solar chimney power plant (SCPP) for power augmentation. This work proposes the study of the performance of the Savonius-style wind turbine (SSWT) in the SCPP. The sliding mesh approach is adopted for the SSWT model, whereas the radiation model is used for the SCPP model in ANSYS Fluent. The SSWT was validated against previous numerical and experimental results, while the SCPP model is validated using the outcomes obtained from the Manzanares plant. The numerical study is carried out at a tip speed ratio (TSR) of 1.0, where the velocity and pressure fluid flow profiles are examined at four different azimuth angles for its performance capabilities. The outcome of the study suggests that SSWT performs well in the SCPP, but is hindered by negative torque at certain azimuthal angles which reduces it overall power producing capacity. It is suggested that TSRs lower than TSR 1.0 may exhibit better drag formation which may lead to an improved turbine performance. Also, flow optimization solution is encouraged for an improved overall torque output, performance and power production by the SSWT in the SCPP.KeywordsVertical axis wind turbineSolar chimney power plantSavonius-style wind turbineNumerical simulation
... For maximize the output power coefficient, the enhancement ratio was 27% at wind speed 10 m/s and tip speed ratio TSR=0.7 [10]. To develop and enhance the performance of SWT design newly, a two-blade SWT was experimented by wind tunnel [11]. Many experimental applications like lighting street system were studies [12]. ...
... .……… (11) The whole SWT moment of inertia is: ...
Many improvements have been researched for conventional Savonius wind turbines in the blade shape to amend the power efficiency. In the present study, the artificial neural network was used to predict the optimum blade shape design for an enhanced power coefficient value for Savonius wind turbine at low wind speed condition numerically with commercial code software ANSYS-CFX and MATLAB. The numerical and experimental work was done with a comparison between two models; conventional and an optimized blade shape. The simulations included the analysis of many models used to learn the artificial neural network to predict the optimum blade shape of Savonius wind turbine at a wind speed of (3 m/s) and a tip speed ratio (TSR) of (0.8). Two aspect ratios (1 and 0.77) were used depending on two and three blades numerically modelled at 3 m/s and TSR range (0.2-1.2) to select best performance model for manufacturing and experimental test. From the experimental work, the torque and power coefficient were calculated based on a range of wind speed of (2.5-4 m/s) and an angular velocity range of (130-280 RPM) based on the meteorological statistics in Baghdad. The numerical results were compared with the experimental ones obtained from the wind tunnel test. The results manifested that the best model is the modified with two blades with AR =1, and the enhancement ratio of power coefficient is 46% numerically and 31% experimentally.
... The C p is calculated from the value C t as per equation 2. The C t is highest at the lowest TSR of 0.7 and it is lowest at the highest TSR of 1.1 and this identical behavior is also observed in the previous investigations [3,7,8,10,12,15]. As the TSR is increasing, the gradual load applied to the turbine is decreasing so the angular velocity of the turbine is also decreasing [18]. The highest value of C t is achieved at 0.7 TSR for all the turbines and the C t = 0.304 of SHKT is the highest among all three turbines. ...
Recently, hydrokinetic energy is playing an important role in the production of green energy. It boasts a minimal ecological footprint and holds significant promise for generating energy on a small scale. Savonius Hydrokinetic Turbine (SHKT) acquires the hydrokinetic energy and converts it into useful energy. It has some specific advantages over other hydrokinetic turbines. Two unique thick blade designs have been utilized to replace the traditional semi-circular blades of the Savonius hydrokinetic turbine, resulting in the creation of two novel variants known as SHKT Design-1 and SHKT Design-2. Numerical investigations are carried out to assess and contrast the performance of SHKT Design-1 and SHKT Design-2 with conventional SHKT, with inlet velocity 0.9 m/s at various tip speed ratios between 0.7 to 1.1. The current study demonstrates that, the performance of SHKT is greater compared to SHKT Design-1 and SHKT Design-2. Savonius hydrokinetic turbine has a 10.5% and 7.5% higher maximum coefficient of power compared to SHKT Design-1 and SHKT Design-2 respectively. The flow field generated about the SHKT, SHKT Design-1 and SHKT Design-2 are examined and deliberated upon to evaluate performance across different facets.
... Technically, horizontal rotation works on a horizontal axis wind turbine (HWAT) while vertical rotation takes on a vertical axis wind turbine (VAWT). Research shows that HWAT can be categorized as significantly close to VAWT [15][16][17][18]. However, VAWT has high efficiency compared to HAWT because the tighter spacing of the counter-rotating turbine allows it to have or produce higher power densities. ...
Drag-type vertical axis wind turbine (VAWT) is well known as a potential and reliable in the development of a wind energy system. Its advantages attract world attention due to its simple geometry design and significantly cheaper to build compared to a horizontal axis wind turbine (HAWT). The present study will consider the essential geometry improvement of the Savonius rotor, where the profile of the blade was made in the form of a half-cylinder. Numerical simulation was conducted to study the effect of geometrical setup on the performance of the rotor in terms of the coefficient of power, coefficient of torque and power output. The model was designed according to the existing tested model by experimental work, except for the inner surface blade which uses an overlap ratio of 0.2. Different wind speeds of 6 m/s, 8 m/s and 10 m/s were used for the simulation to analyze the behaviour of properties of the new design blade. According to the results obtained, it shows that the power coefficient for the new design of the inner blade was increased by 20% compared to the previous design. The power output of the wind turbine reaches the maximum power in the middle of the tip speed ratio for all types of wind speeds. This is because the power coefficient will start to fall off after reaching the maximum electrical power produced. Besides, it is due to the limit of the blade performance which will keep the blade from rotating too fast and avoiding damage due to excessive force.
... However, this turbine has a low power coefficient, leading to numerous studies to improve its aerodynamic performance by either the experimental approach (e.g. Al-Faruk and Sharifian, 2014;Bach, 1931;Blackwell et al., 1977;Kamoji et al., 2009;Roy and Saha, 2015) or the numerical approach (e.g. Abdelaziz et al., 2022;Anh et al., 2022a;Anh et al., 2022b;Chan et al., 2018;Hassan Saeed et al., 2019;Kerikous and Thévenin, 2019;Minh et al., 2023;Mohamed et al., 2021;Ramadan et al., 2021;Storti et al., 2019;Tian et al., 2018). ...
... Chan et al., [38] utilized genetic algorithms to find the ideal blade shape while controlling the geometry of the blade using 3 changeable points. Bach-type rotor profiles were enhanced by Roy and Saha [39]. According to the results, the enhanced Bach-type rotor performed 34.8% better than the conventional SWT. ...
As the best replacement for fossil fuels, green energy resources have established their significance on a worldwide basis. The availability of wind energy makes it the best promising form of green energy. For transforming wind kinetic energy into mechanical energy at low wind speeds, the Savonius wind rotor is regarded as the best choice. The main goal of the current study is to improve the power coefficient (Cp) and torque coefficient (Ct) of the Conventional Savonius wind turbine (SWT) by modifying the inner surface of the blade using a wavy profile. The aerodynamic performance of the wavy turbine is then compared with the conventional turbine in terms of Cp and Ct. The study is conducted using numerical simulation with the assistance of the ANSYS software. The flow characteristics around the turbines are solved utilizing the SST k-ω turbulence model. The simulation outcomes confirmed that the Cp of the wavy rotor increased by about 14.5% at a tip speed ratio of λ= 0.4. Additionally, outcomes showed the peak Cp is 0.18 at λ=0.7 which is 12.5% greater than the conventional SWT.
... In previous studies, it was evidenced that employing multiblade profiles in the blades of this type of rotors can improve their performance by 10,8 % with respect to a profile without the secondary element (split Bach profile), as well as by 51,2 % regarding conventional semicircular profiles ( Fig. 1) (6,(13)(14)(15)(16)(17). ...
Contexto: Este estudio evalúa la estabilidad estructural de un rotor tipo Savonius implementando un perfil multielemento, con el propósito de reducir la resistencia al movimiento y mejorar así el rendimiento aerodinámico. El rotor con el perfil en estudio se comparó con rotores de perfiles semicircular convencional y Bach dividido. Método: Se analizó la interacción fluido-estructura mediante la simulación numérica de los tres rotores, y se determinó el estado de esfuerzos y deformaciones en un régimen normal de operación. A los rotores se les asignó el mismo material de construcción, y estos fueron estudiados bajo los mismos parámetros y modelos de la dinámica de fluidos y mecánica computacional a través del software ANSYS. Resultados: Los resultados obtenidos evidenciaron un mejor comportamiento estructural en el rotor con la configuración multielemento, al reducir el esfuerzo equivalente máximo en 59,10 y 42,87\% y las deformaciones en 47,40 y 33,59\% con respecto a los rotores de perfiles semicircular convencional y Bach dividido respectivamente. Conclusiones: La configuración multielemento permite un mayor rendimiento aerodinámico y estructural, a la vez que se conserva la simplicidad de construcción y operacional que caracterizan al rotor tipo Savonius.
... This research evaluates the implementation of a multi-element geometry in a Savonius rotor without an intermediate shaft and using a split Bach type profile for the main element; since this type of profile is among the best performing ones today [28]. The use of multielement profiles in a Savonius rotor can help energize the concave or intrados side of the blade, avoiding depressurization and reducing the resistance to motion. ...
In the present study, the implementation of multi-blade profiles in a Savonius rotor was evaluated in order to increase the pressure in the blade’s intrados and, thus, decrease motion resistance. The geometric proportions of the secondary element were determined, which maximized the rotor’s performance. For this, the response surface methodology was used through a full factorial experimental design and a face-centered central composite design, consisting of three factors, each with three levels. The response variable that was sought to be maximized was the power coefficient (CP), which was obtained through the numerical simulation of the geometric configurations resulting from the different treatments. All geometries were studied under the same parameters and computational fluid dynamics models through the ANSYS Fluent software. The results obtained through both experimental designs showed a difference of only 1.06% in the performance estimates using the regression model and 3.41% when simulating the optimal proportions geometries. The optimized geometry was characterized by a CP of 0.2948, which constitutes an increase of 10.8% in its performance compared to the profile without secondary elements and of 51.2% compared to the conventional semicircular profile. The numerical results were contrasted with experimental data obtained using a wind tunnel, revealing a good degree of fit.
... In particular, energy generation by wind power plays an important role in this context. The study of small wind turbines, especially the vertical axis wind turbine (VAWT), is always a subject of research, especially in view of the current energy crisis [1][2][3][4][5]. ...
This paper describes the development, design and function of a test rig for the measurement of small wind turbines in a wind tunnel and presents the first exemplary measurements of the performance characteristics of various horizontal and vertical rotors. A central part of this test rig is the developed control system with an electronic load, which enables an automated recording of the measured values for the evaluation of the power coefficients (c p ) and tip-speed ratio (λ) values. Another challenge emerges owing to the known differences in the power spectrum, because the power coefficients of drag rotors (<20%) are different from those of buoyancy rotors (<40%). The system was adapted to the different ranges by means of a stepless switching using various resistors. The entire control and regulation unit was compactly implemented using a programmable logic controller (PLC) and dynamically linked to the operating parameters of the wind tunnel. This enables an automated operation of the wind tunnel during the determination of the performance parameters of the investigated wind turbines.
... It was found that a turbine with a blade fullness of n = 1 yields the highest power coefficient (C p = 0.2573) ( Figure 5(b)) with an increase of about 11% from the convention S-rotor. Roy and Saha [17] compared experimentally the performance of their novel blade design, the conventional S-rotor, Benesh, modified Bach, and semielliptical bladed turbines. The experiment demonstrated the superiority of the novel blade rotor over the other designs. ...
Wind as a renewable energy source is not yet fully exploited despite the permanent availability of this source. Moreover, in countries where renewable energy regulations are still absent, large-scale applications are still not available. The only wind turbines implemented are small-scaled applications owed to individual contributions. In this context, the Savonius wind turbine seems to be the most suitable choice at this scale because of its relatively low noise level, ease of manufacturing and maintenance, and self-starting aspect even at low wind speeds. However, the major drawback of such a turbine is its relatively low efficiency. In this framework, this study aims at assessing the various design parameters (number of
blades, height-to-diameter ratio, and overlap ratio) of a Savonius wind turbine in an attempt to increase its efficiency. This is realised via computational fluid dynamics simulations followed by experimental validation through wind tunnel testing. Results show that the optimum configuration consists of a two-blade S-rotor with around 18% overlap. Future improvements could include shielding the returning blade to increase the torque.
... On the other hand, there is another dimensionless parameter that has a great influence on the efficiency of the [19,20] turbine. The TSR λ (Tip Speed Ratio) indicates the speed of the blade at its tip and the current velocity. ...
Hydropower is an important source of energy in Latin America. Many countries in the region, including Brazil, Peru, Colombia, and Chile, rely heavily on hydropower plants to meet their energy needs. However, there are also challenges related to the use of hydropower in the region, such as the construction of dams that can have negative impacts on ecosystems and local communities. A new alternative is the production of energy through hydrokinetic turbines because they are a clean and renewable energy source that does not emit greenhouse gases. In addition, its production is predictable and can be generated in a variety of environments, from coasts to rivers and canals. Within the hydrokinetic turbines are the H-Darrieus turbines although they are still under development, they are seen as an important opportunity to diversify the energy matrix and reduce dependence on fossil fuels. The main purpose of this study is to determine and compare the efficiency of three Darrieus H-type vertical axis hydrokinetic turbines numerically. The turbines were configured with different solidities. The NACA 0018 profile was used for the turbine design. The study was carried out using the ANSYS® Fluent 2022R2 software, two-dimensional (2D) simulations set up constant operating conditions. Rotation speed variations have been set between 21 and 74 RPM with 10 rpm increments. Furthermore, the General Richardson extrapolation method is used for the analysis of mesh convergence, monitoring the turbine power coefficient as a convergence parameter. The numerical results show that the turbine H-Darrieus with a solidity of 1.0, a wider operating range, and lower power and torque coefficient. At low TRS, the largest solidity provided the best efficiency and the greatest self-starting capability, but it also had the smallest operating range
... 5 Mahrous [31] Enhanced the best C p by 48% compared to the conventional Savonius rotor by changing the blade shape factor. 6 Roy et al. [32] Studied a newly developed profile and compared its performance with common Savonius profiles. Used an optimization library (OPAL) to develop a modified Savonius rotor, where the bucket is divided into two fixed endpoints and three variable points. ...
Wind energy is a vital renewable energy source due to its abundance. The Savonius turbine has proven to be a
promising vertical axis wind turbine for converting wind kinetic energy to mechanical energy. The performance
of two novel Savonius rotor profiles, the sine, and conical profiles, is investigated in the present research. A 3-D
numerical simulation of a Savonius turbine is conducted using ANSYS Fluent software. Unsteady Reynolds
Averaged Navier–Stokes equations (URANS) are used to solve the flow characteristics of the Savonius turbine
using the SST k-ω turbulence model. The conventional Savonius turbine is validated by comparing the present
numerical results with previous numerical and experimental data. The sine profile reduced the maximum power
coefficient by 1.25% compared to the conventional profile. The conical rotor enhanced the maximum power
coefficient by 8.6% compared to the conventional profile.
... They will significantly affect the developed nations in a matter of days [3]. In addition, the decrement in the output of these sources causes an imbalance in the energy market worldwide [4]. The possibility of fossil fuel production will also be diminishing in the future due to their non-renewability and confined availability. ...
Darrieus type straight-bladed vertical axis wind turbines (SB-VAWTs) are more appropriate for generating electricity than other VAWTs mostly suitable for regions having low to medium wind speed. The installation of SB-VAWTs faces start-up problems, which limits its applicability in low wind speed environments. The start-up problem arises mainly due to the cross-sectional blade profile and is the crucial parameter for blade design. To overcome this issue, it is aimed to study the influence of the J-shape airfoil with various opening ratios in the Darrieus type SB-VAWTs in terms of starting torque and aerodynamic performance. The design of a J-shape airfoil is created by removing a portion towards the trailing edge of the conventional NACA 4415 airfoil on its upper or lower surface. This analysis displays a maximum power coefficient of 0.517 when the Darrieus type SB-VAWT utilizes upper cut J-shape airfoils with opening ratio of 0.8, at the tip speed ratio (TSR) of 1.6. These values are higher than the power coefficient (0.486) of conventional NACA 4415 airfoil at the same TSR. The SB-VAWT depicts a lower performance while it employs the lower cut J-shape airfoils. Furthermore, the present study demonstrates that the power and torque coefficient of SB-VAWT improves by about 31% when the opening ratio of upper cut J-shape airfoil is varied from 0.1 to 0.8.
... The difference of the force that the incoming air produces on the convex and concave parts of the blades causes the turbine to rotate.The production of torque takes place by the rotation of the blades caused due to mechanical force of air trapped inside the concave part of the blades pushing against them. More than two blades can be added to because it spin more to produce more drag [18][19][20][21][22][23][24][25][26][27]. ...
In the steps to save our earth from global warming every nation focused on their own way to promote green energy among which the Savonius vertical axis wind turbine is one of the excellent viable solutions for scavenging wind energy in a downtown background, due to distinctive characteristics such as compactness, self-starting ability at light wind, minimum noise level, with relatively reasonable price and simple assembly. However, the traditional Savonius Wind Turbines with semicircular blades has a proportionately low power coefficient together with a high negative torque produced by the returning blade is a crucial disadvantage of this rotor. This work focuses on reviewing and giving an overview on the form of the wings of Savonius Vertical Axis Wind Turbine. This paper also aims to give a run through of the several augmentation approaches used in Savonius rotor over the last four decades. In this paper, a brief on all possible segments and parts of the machine is given after a brief analysis and research on each topic.
... The results of these measurements are a benchmark for many researchers [12][13][14][32][33][34][35][36][37]. Roy and Ducoin [16] compared the results of the average torque coefficient for three experiments by D'Alessandro et al. [38], Roy and Saha [39], and Blackwell et al. [10]. Although the experimental conditions for each reference were different, these compared characteristics are very similar. ...
The geometry of a conventional two-bladed Savonius rotor was used in this study based on a report available in the literature. A two-dimensional rotor model consisting of two buckets and an overlap ratio of 0.1 was prepared. The unsteady Reynolds averaged Navier-Stokes (URANS) equations and the eddy-viscosity turbulence model SST k-ω were employed in order to solve the fluid motion equations numerically. Instantaneous velocities and pressures were calculated at defined points around the rotor and then averaged. The research shows that the operating rotor significantly modifies the flow on the downwind part of the rotor and in the wake, but the impact of the tip speed ratio on the average velocity distribution is small. This parameter has a much greater influence on the characteristics of the aerodynamic moment and the distribution of static pressure in the wake. In the upwind part of the rotor, the average velocity parallel to the direction of undisturbed flow is 29% lower than in the downwind part.
... For this reason, in recent years, many studies have been and are being carried out in order to increase the low performance of Savonius wind turbines. For this purpose, various interior design parameters such as blade type design, overlap ratio between blades, separation ratio and turbine end plate were investigated numerically and/or experimentally (Al-Faruk Sharifian 2016; Kacprzak et al. 2013;Jaohindy et al. 2013;Jeon et al. 2015;Roy and Saha 2015;Akwa et al. 2012;Alom and Saha 2018;Kamoji et al. 2009;Irabu and Roy 2011;Saha and Rajkumar2006). Driss et al. (2014) carried out numerical simulation and experimental validation to study the turbulent flow around a small incurved Savonius wind rotor. ...
In this study, a square and a rectangular inlet cross-sectional wind router were designed as a performance enhancing mechanism in order to reduce or eliminate the flow on the convex blade rotating against the wind, which causes the low performance of Savonius wind turbines and analyzed numerically using the Ansys Fluent program. With this design, it was attempted to increase the turbine performance by reducing or eliminating the negative torque, which is created in the opposite direction, on the convex side of the blade. For this purpose, the optimum design was attempted to be achieved by changing the positions at certain ratios of the right, left, bottom, and top plates of the wind router assembly placed in front of the turbine. By comparing the numerical data with the experimental data, the accuracy of the numerical analysis method was provided with an average deviation of 5%. It was determined that the power coefficient of 0.15 obtained with the conventional Savonius wind turbine increased to about 0.39 when the inlet cross section of the wind router was square and to about 0.45 when it was rectangular. With the optimum design ratio obtained as a result of this study, the power coefficient of the Savonius wind turbine with wind router was increased by approximately three times compared to the conventional Savonius wind turbine without wind router.
... The application of endplates may increase the rotor efficiency, but research was conducted without endplate application to decrease the manufacturing cost and improve safety. The semi-circular type blade, which is the basic geometry, can be classified under the Bach and elliptical types according to the blade curvature [24,25]. The common design parameters (AR and OR) of each Savonius blade were determined by conducting CFD analysis of the semi-circular type. ...
Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the construction of a decentralized power system. Savonius wind turbines are operated by drag force, with the blades moving in the same direction as the flow current providing the thrust force and those moving in the opposite direction of the wind being rotated by the drag force. In this study, the Savonius wind turbine design was examined to develop a stable wind turbine for use in urban centers at low wind speeds. The Savonius rotor design variables (aspect and overlap ratios) and blade forms (semi-circular, Bach, and elliptical type) were examined using computational fluid dynamics analysis. Moreover, a rotor capable of providing the target output was designed and maximum rotor efficiency of 18% was realized. Further, changes to the flow corresponding with various turbine layouts were analyzed to determine the arrangement that would maximize turbine performance. The results showed that the maximum efficiency of the turbines was in the 17–19% range and without significant variation.
... Unfortunately, it has a low efficiency, which explains many experimental and simulation studies which are carried out aiming to improve this drawback [12][13][14][15][16][17][18][19]. On the modification of the blade profile of Savonius turbines, [20] propose an optimized Bach type blade geometry. This new blade profile was generated from a series of experimental studies on Bach and Benesh type turbines by modifying the geometric arcs, the overlap distances and the dimensions of the blade profiles [21]. ...
This paper presents a numerical study of the airflow characteristics in the wake of a compact SUV vehicle on which two models of Savonius optimized wind turbines (Bach optimized and conventional with a ratio overlap of 0.2) are mounted in the "bull bars." The turbines consist of two blades placed horizontally at the end of which are two generators capable of converting wind energy into electrical energy necessary for the operation of vehicle accessories. The Fluent solver was used to perform the steady-state incompressible 3D numerical simulations of the RANS equations, and the realizable k-ε turbulence model with the Menter-Lechner wall functions was used to solve the problem mathematically. The numerical results obtained show, respectively, 0.403 of the drag coefficient for the vehicle alone and 0.404 of the drag coefficient for the vehicle equipped with "bull bars." By integrating the wind turbines in the "bull bars" located at the front of the vehicle, we were able to obtain 0.404 as the maximum values of the drag coefficient for the optimized Bach wind turbine when the angle of attack of the blade was 120° and 0.408 for the conventional turbine with 80° as the angle of attack. The position and optimized profile of the turbines had no impact on the aerodynamic characteristics of the base vehicle and only contributed 0% for the first model and 0.99% increase in drag for the second model. The optimized Bach model is therefore the most favorable.
... Jiang et al. [34] numerically investigated the effects of blade tip shape and supporting strut on a large turbine model with the aim to reduce blade tip vortex and to optimise the structure of the turbine for enhanced performance. Roy and Saha [35] developed a new blade profile for a drag-based turbine from a series of experimental studies on Bach and Benesh type turbines by modifying geometric arcs, overlapping distances and dimensions of blade profiles. Their design show improved performance as compared to other blade profile shapes such as semi-circular and semi-elliptical. ...
Vertical Axis Wind Turbines (VAWTs) are omni-directional, low-cost, low-efficiency wind power extractors. A conventional drag-based VAWT consists of multiple thin rotor blades with a typical peak Tip Speed Ratio (λ) of < 1. Their lower cut-in speed and maintenance cost make them ideal for power generation in urban environments. Numerous studies have been carried out analysing steady operation of VAWTs and quantifying their performance characteristics, however, minimal attention has been paid to their start-up dynamics. There are a few recent studies in which start-up dynamics of lift-based VAWTs have been analysed but such studies for drag-based VAWTs are severely limited. In this study, start-up dynamics of a conventional multi-blade drag-based VAWT have been numerically investigated using a time-dependant Computational Fluid Dynamics (CFD) solver. In order to enhance the start-up characteristics of the drag-based VAWT, a stator has been integrated in the design assembly. The numerical results obtained in this study indicate that an appropriately designed stator can significantly enhance the start-up of a VAWT by directing the flow towards the rotor blades, leading to higher rotational velocity (ω) and λ. With the addition of a stator, the flow fields downstream the VAWT becomes more uniform.
... Contrarily, a semicircular Savonius rotor rendered a maximum C p of 0.143 only. Roy and Saha [31] proposed an innovative Savonius blade profile design using computational analysis. Their findings indicated that the proposed blade profile outperformed the power coefficients showed by other documented profiles, viz. the modified Bach type, Benesh type, semi-elliptical type, and Savonius-style wind turbine by 3.3%, 6.9%, 19.2%, and 34.8%, respectively. ...
The Savonius Hydro-Kinetic Turbine (SHKT) has a frugal design with the possibility of easy local manufacturing. Therefore, SHKT is a suitable proposition for off-grid power generation in standalone mode across the remote and hilly locations. In this work, an optimized geometry of a semicircular SHKT was proposed through 3D CFD based simulations, artificial neural network (ANN) augmented optimization and experiments. Firstly, CFD investigations of SHKT were performed to identify the parameters affecting the power coefficient (Cp). Results of CFD simulations were used to train ANN which was further used to optimize the blade parameters. Finally, experiments were conducted on the optimized blade to validate its performance. The results showed that aspect ratio between 1.4 and 2.0 and overlap ratio between 0.15 and 0.2 indicate better performance. Blade arc angle of 166° produced a maximum Cp of 0.194 at a TSR of 0.8. The study concluded that ANN is a time saving yet accurate tool for optimization of turbine blades, and the results provide a good agreement with the computational results with difference of 1.57% only. The optimized blade is found to be 8% more efficient than semicircular blades and is recommended for its applications in hydro farms and turbine clusters.
... Since its initiation in 1920, numerous efforts have been made to enhance its performance. The influence of geometric parameters such as AR, OR (Vimal Patel et al., 2016), varying blade arc angles (Kamoji et al., 2009a;Roy and Saha, 2015;Zhou and Rempfer, 2013), the effect of inner blade position (Al-Ghriybaha and, Mohd Fadhli Zulkafli, Djamal Hissein Didane, 2019), the influence of taper (Shashikumar C M et al., 2020), different blade profiles (Hassan Saeed et al., 2019), changing the semi-circular blade profile to modified V-shaped blade profile , varying the V-angles of modified V-shaped blade profile and studies on helical blade profiles (Kamoji et al., 2009b), were carried out by various investigators to enhance the turbine efficiency (Roy and Saha, 2013a). reviewed experimental studies carried out by various researchers on Savonius rotors based on design, performance, and optimization techniques. ...
In the present paper, three-dimensional numerical simulations were carried out to examine the influence of the overlap ratio between the two straight edges on the advancing and returning blades of the novel V-shaped rotor blade profiles using the sliding mesh technique. The performance parameters were computed with respect to the tip speed ratio. The findings show that the coefficient of torque and power for the novel V-shaped turbine blade is maximum for the zero-overlap ratio compared to the turbine blade, with an overlap ratio ranging from 0.05 to 0.3. The blade profiles' flow field was visualized at different angular positions, and various significant zones developed during the turbine blade rotation were captured and analyzed. The new overlapping jet developed between the two straight edges of the advancing and returning blade profiles as the overlap ratio varies from 0.05 to 0.3. Therefore, the turbine's performance is reduced due to the development of an overlap jet as it travels parallel to the straight edges of the blade profile and does not impact the rear side of the returning blade profile.
... According to Nawar et al. [18] and Kamal et al. [21], the model is placed 400 mm from the wind tunnel exit, with a blockage ratio of almost 30%. As a result, the computed blockage ratio of this research is lower than that of recent studies [24,25]. J o u r n a l P r e -p r o o f ...
Wind power is one of the most quickly expanding forms of clean energy. A novel horizontal axis wind turbine type, the Archimedes Spiral Wind Turbine (ASWT), is built for residential applications. The influence of the rotor pitch to diameter ratio (2s/D) and the aerofoil blade profile on the productivity of ASWT is investigated using experimentation and computer simulation. To fulfill the validation of the experimental work, the ANSYS Fluent solver provides the numerical solution. The tests are performed on a modified ASWT with a nominal blade thickness and blade angles of α1 = 25°, α2 = 50°, and α3 = 60° for the first, middle, and third blades. Wind speeds of 8 and 10 m/s were used. The NACA4401 ASWT with (2s/D) = 0.30 is the best-studied design. At a wind speed of 10 m/s, the maximum CP of the conventional, modified, and aerofoiled ASWTs is 0.243, 0.286, and 0.3045, respectively, at tip speed ratios (λ) of 1.5, 2, and 2. Compared to the conventional and modified ASWT, the aerofoiled ASWT exhibits a 26.88% and 6.47% improvement in the peak CP.
Conventional hydroelectric turbines use the potential energy of the water as a primary source of energy. However, the hydrokinetic turbines use the kinetic energy of the flowing water to generate power output. It is also one of the best clean energy generation technologies. Out of many hydrokinetic turbines, the Savonius hydrokinetic turbine is very simple in design and easy to manufacture. The ratio of the gap between the two vanes to the turbine diameter is known as the overlap ratio. The effect of the positive overlap has been extensively investigated for the Savonius turbine. However, for the first time in the present investigation, the effect of the negative overlap ratio on the hydrodynamic performance of the Savonius turbine is investigated. The highest value of negative overlap ratios is obtained for two, three, and four numbers of blades of Savonius hydrokinetic turbines. With the present investigation, the best-suited range of the negative overlap ratio is obtained for each case. The present investigation also concludes that the Savonius turbine with three and four vanes, with a negative overlap ratio, maintains its good performance for a wide variation in the turbine load. Also, the best-obtained design through numerical analysis was cross-verified by experiments.
The eminent energy crisis and high emission of fossil fuels provide thrust for developing renewable energy-based technologies. Wind and hydrokinetic energies are the most promising renewable energy resources for electric power generation to meet the growing energy demand. The vertical-axis hybrid turbine, which combines the features of good starting characteristics of the Savonius turbine and the operational efficiency of the Darrieus turbine, can serve as a viable option for power generation. A variety of configurations of the hybrid turbine are possible based on several design parameters such as the relative position of the Darrieus and Savonius rotors, overlap ratio, solidity ratio, blade or buckets shape and radius ratio, attachment angle and others. To some extent, the influence of these parameters on the hybrid turbine performance has been investigated through experimental and numerical studies by considering a number of physical and computational models. In most of the findings, the range of maximum power coefficient values is recorded between 0.08 and 0.51. Though individual vertical axis turbines have been widely studied and reviewed, similar review papers on hybrid turbines are scarce. This paper brings out significant developments that have taken place in the area of hybrid turbines, identifies the operating parameters, highlights the challenges related to rotor/turbine aerodynamics, modelling, simulation, testing methodologies. Based on these discussions, the strategies for future hybrid turbine designs are presented.
Wind energy is crucial for meeting climate and energy sustainability targets. Small wind turbines (SWTs) have gained significant attention due to their size and adaptability. These turbines have potential for Internet of Things (IoT) applications, particularly in powering large areas and low-power devices. This review examines SWTs for IoT applications, providing an extensive overview of their development, including wind energy rectifiers, power generation mechanisms, and IoT applications. The paper summarizes and compares different types of wind energy rectifiers, explores recent advancements and representative work, and discusses applicable generator systems such as electromagnetic, piezoelectric, and triboelectric nanogenerators. In addition, it thoroughly reviews the latest research on IoT application scenarios, including transportation, urban environments, intelligent agriculture, and self-powered wind sensing. Lastly, the paper identifies future research directions and emphasizes the potential of interdisciplinary technologies in driving SWT development.
This study examines the literature on improving the low performance of Savonius wind turbines, which are a type of vertical axis wind turbine. The literature studies on improving the performance of Savonius turbines have been summarized into two categories: interior structural design and exterior additional design. Due to the extensive nature of studies focusing on interior design changes, this research primarily focuses on performance studies related to exterior design modifications of Savonius wind turbines, particularly in recent years. This study aimed to provide a comprehensive examination of these performance studies and contribute to the existing literature by presenting a systematic reference on this issue. To achieve this objective, a thorough review of turbine exterior design studies has been conducted. The focus was on determining the percentage increase in power coefficient achieved by turbines with exterior design modifications compared to the classical turbine versions. Here, it has been determined that the power coefficient values of Savonius wind turbines can reach approximately 0.400 through interior design changes. However, with the implementation of additional exterior design modifications, these power coefficient values can be further increased to around 0.520. Thus, within the scope of this study, it has been determined that the turbine power coefficients show a fairly good increase with exterior design techniques compared to interior design techniques.
In this study, a 3D-CFD simulation on the effect of various design and operating parameters, namely the number of blades, overlap ratio, spacing size, arc angle, shape factor, presence of curtain, wind velocity, and multi-bucket rotor, on the aerodynamic performance of a Savonius vertical axis wind turbine (VAWT) is conducted. In order to evaluate the effect of each parameter, the rotor’s power coefficient (Cp) for different tip speed ratio (TSR) values and overall torque as a function of the azimuth angle are investigated. The results show that the generated power of a solid rotor with more buckets is less than that of the two-bladed rotor, and by decreasing the overlap ratio and spacing size, Cp values are enhanced. Moreover, a rotor with a larger bucket arc angle has less Cp value and total torque, in addition to shape factor, which changes the configuration of the rotor by adding arms, thus enhancing the aerodynamic performance of the prototype. Furthermore, it is shown that installing a curtain in the upstream section of the rotor improves Cp value by directing airflow. Moreover, it is observed that by increasing inlet wind velocity and, subsequently, the Reynolds number, generated power is boosted. In addition, it is noted that a suitable multi-bucket rotor configuration can boost generated power. Finally, the optimum design is achieved by using the Kriging method. Based on the optimization results, a 2-bladed Savonius VAWT with an overlap ratio of 0, spacing size of 0 (m), arc angle of 170°, shape factor of 0.5, and inlet wind velocity of 12 (m/s) at TSR = 0.37 introduces the highest efficiency.
For over two decades, the quest for decentralized electric power generation has stimulated much research interest into the Savonius (or S-type) wind turbine rotors. To enhance their efficiency, the operating parameters have already been examined by various numerical and experimental techniques. While most researchers have focused on using selected turbulence models to arrive at some meaningful conclusions and recommendations, no study analyzing a range of turbulence models in a systematic and comprehensive manner is reported. This study thus aims at conducting 2-D unsteady numerical simulations of a conventional semicircular-bladed Savonius rotor using six different turbulence models, viz., standard k–ε, realizable k–ε, RNG k–ε models, standard k–ω and shear stress transport (SST) k–ω, and transition SST (TSST) turbulence models. The simulations are performed by commercial finite-volume method solver ANSYS Fluent 17.1 at a fixed Reynolds number (Re) of 1.23 × 10⁵ based on the rotor overall diameter. This study demonstrates the prediction capabilities of realizable k–ε, RNG k–ε, SST k–ω, and TSST models more accurately than those of other models. However, due to higher computational cost associated with TSST model, the use of realizable k–ε, RNG k–ε, and SST k–ω models for predicting the aerodynamic performance of other developed and to-be-developed profiles of Savonius rotor is recommended.
p>Savonius wind turbines have advantages of self-rotating at low speed wind, high starting torque, and less noise generation. However, they have low electric power generation capacity. This paper presents electric power generation improvement for small Savonius wind turbines when operating at low-speed wind of 1-6 m/s by using optimal Bach-type blades, twist blades and a wind tunnel. The turbine prototypes with the optimum diameter and height of 32 cm were developed with 3 different blade types: conventional semicircular blades, Bach-type blades and twisted 15° blades and a wind tunnel. The experimental results showed that the Savonius wind turbine with Bach-type generated highest electric voltage, which was 19.3% and 7.6% higher compared to conventional blades and twisted 15° blades. The additional wind tunnel could improve electric power generation efficiency by approximately 21.4% compared to the turbines without the tunnels.</p
Hydrokinetic energy has the least environmental impact and a high potential for small-scale energy production. Savonius hydrokinetic turbine extracts the hydrokinetic energy from the water current. It has a simple design and is inexpensive and quiet. The NACA6409 blades are implemented in place of conventional semi-circular blades of the Savonius hydrokinetic turbine and the newly Airfoil Bladed Savonius Hydrokinetic Turbine (ABSHKT) is developed. The deflector plate is implemented to enhance the performance of ABSHKT. A Computational Fluid Dynamics (CFD) simulation is conducted to analyze and compare the performance of ABSHKT with deflector to the conventional Savonius hydrokinetic turbine with deflector, with inlet velocity 1m/s at various TSR range between 0.7 to 1.1. The present investigation shows that, the maximum power coefficient for ABSHKT and SHKT with deflector is 0.227 at 0.8 TSR and 0.25 at 0.8 TSR respectively. The ABSHKT with deflector has lower performance compared to SHKT with deflector. Implementing the enhanced augmentation technique is advisable to improve the performance of ABSHKT. The flow field spreading around the ABSHKT and SHKT with deflector is analyzed and discussed to compare the performance of both turbines with various aspects.
This study numerically investigates the effect of multi-curve blade configuration on the performance of the optimized Savonius wind turbine. The simulation is performed utilizing a sequence of unsteady 2D computational fluid dynamics in the commercial software ANSYS Fluent 2021R2. The results state a high influence of the turbine performance on the multi-curve shape. The highest performance of the rotor is recognized on the blade configuration with the main profile made by a quarter circular R3* = 0.5 and a quarter elliptical section. For which, the power coefficient Cp is improved by 185.1% at the tip speed ratio (TSR) higher than 1.0 and up to 5.5% at TSR of less than 0.8, making this design better suited for wide working conditions over the previous configurations.KeywordsSavoniusRenewable energyMulti-curve bladeRealizable k-εTip speed ratio
In this study, the turbine performances of Savonius wind turbines were investigated in the case of dual usage. While implementing the dual use of the Savonius wind turbine, a flat plate deflector was placed in front of the turbines to increase the turbine performance. The effects of design parameters such as the geometric dimensions of this flat plate placed in front of the turbines and the geometrical placement position on the turbine performance were investigated. In this direction, the flat plate prevented the negative torque that occurs during the operation of the turbines. Hence, the plate guided the wind to the turbine blade, which generated positive torque. The numerical analyses made in this study were confirmed by the previous literature study. The performance values of single, dual, and flat plate dual Savonius wind turbines were analyzed using the numerical analysis method, the accuracy of which was proven by the experimental data. It was determined that the similarity between the experimental result and the numerical result was approximately 0.3%, especially in the maximum power coefficient values. The computational fluid dynamics (CFD) program ANSYS Fluent was used for turbine performance analysis. With this design study, the maximum power coefficient ( C p ) was obtained around 0.17 with a single Savonius wind turbine, while the maximum power coefficient ( C p ) was obtained around 0.24 with a flat plate dual Savonius wind turbine. As a result, the power coefficient obtained with a single Savonius wind turbine increased by 42% in the flat plate dual Savonius turbine system when compared to the power coefficient of the single Savonius wind turbine. Thus, it was determined that the power coefficient obtained with a single Savonius wind turbine in the flat plate dual Savonius turbine system increased by 42% compared to the power coefficient of the single Savonius wind turbine.
In order to overcome the problems of low efficiency and poor results of classical optimization methods, an efficient, intelligent, and reliable method for optimizing the shape of the blades of the Savonius wind turbine is proposed in this paper. Firstly, the shape of the blade is parameterized by the third-order Bezier curve, and then a certain number of design schemes in the design space are obtained by the Latin hypercube sampling method and the torque coefficient of each design scheme is evaluated based on CFD simulation, and next a radial basis function surrogate model is constructed based on these design schemes and their torque coefficients, and finally the optimal design scheme is obtained by solving the surrogate model using the marine predator algorithm, and is verified using the CFD simulation. The results show that when the tip speed ratio is 1, the average torque coefficient of the optimized blade obtained by the above method is about 7% higher than that of the classical semicircular blade, and under other tip speed ratios, the average torque coefficients of the optimized blade is also significantly higher than that of the classical blade. Furthermore, compared with the classical semicircular blade, about 11% materials can be saved in the manufacturing of the optimized blade.
Blade shape has a significant effect on the wind-capturing ability of the Savonius wind turbine. This paper proposes an intelligent optimization method for optimizing the shape of the blade of the Savonius wind turbine. This method firstly uses the cubic Bezier curve with four design parameters (x1, y1, x2, y2) to characterize the complex blade shape, and then uses the Latin hypercube sampling method to sample some design schemes throughout the design space, and uses computational fluid dynamics simulation to evaluate the response value, i.e. the moment coefficient, of each scheme, and then uses the support vector regression surrogate model to describe the relationship between the design parameters and their response values, finally uses modified flower pollination algorithm to solve the surrogate model to obtain the optimal blade shape. After comparing and analyzing the optimized blade and the classical semicircular blade, it is found that compared with the classical semicircular blade, the optimized blade has a better wind-capturing ability. When the wind speed is 7 m/s and the tip speed ratio is 1, its average power coefficient Cp is significantly increased from 0.260027 to 0.277902 (about 6.87% higher). In addition, the aerodynamic performance of the optimized blade is also better than the classical semicircular blade at other tip speed ratios (TSRs = 0.6–1.2). It is shown that the wind turbine with the optimized blade has great potential in a practical application environment.
Maintaining high power generation for small lift-driven vertical axis wind turbines in a changing wind environment has not been well studied yet, due to the challenges inherited from the unpredictable turbulent flow-blade interaction and complex blade interferences. Herein, a fast online reinforcement learning pitch control using an active programmable 4 bar linkage mechanism is proposed, making it possible for turbines to quickly adapt to wind changes and maintain high power output in operation. We formulate the pitching mechanism using a drag-link configuration with a variable frame link length into an optimization problem and further solve it by the interior point algorithm under a wide range of tip speed ratios. Then, a parameter explorative policy gradient reinforcement learning method is designed for the turbine to adaptively tune the frame link length. Since the design significantly reduces the number of parameters needed to depict a whole pitch trajectory, the proposed online learning process can converge quickly, making it capable of handling complex wind conditions in an urban environment. The transient behavior overlooked in much of the literature is also studied. Comparisons to two benchmarks have demonstrated that our proposed system has a superior performance.
The recent increase in cellular communication coverage and usage has been remarkable. The increase has occurred throughout the globe, in both developed and developing regions. In fact, in some regions of the world, land-line communications are being avoided altogether as countries move into primarily mobile communication technologies. In order for cellular communication to function adequately, communication towers must be built with sufficient density to provide coverage. These towers have electrical requirements which are often not met with grid-based power. This study presents a novel design of a wind turbine which is designed to be positioned atop existing communication towers in order to provide local power for the tower. These turbines have vertical axes of rotation and other features which suit them for this highly specialized application. The study carried out here shows that these turbines are able to provide the required electrical power to fully satisfy the communication-tower electronics.
A novel, vertical-axis wind turbine has been developed for the use in powering cellular communication towers. The new turbine takes advantage of the elevated heights of existing towers to access relatively high-speed winds. The new turbine is designed to provide local power to the cellular communication system, the electronics are designed so that the turbine stores power in a battery system when excess power is generated. This stored power is utilized at times when the wind-speed is insufficient to power the communication system. A major opportunity exists for communication towers which are located away from grid-connected electricity. In these cases, the towers are often powered by diesel generators. Through the use of turbines, it is possible to greatly reduce the diesel-fuel consumption.
Wind-tunnel tests have evaluated the potential for vented blades and blade capping for the improvement of power generation. It was found that while venting provides only marginal improvement, capping greatly increases power generation. The results also show that further improvements can be obtained through modification of the electrical system.
A numerical simulation has been performed to assist in evaluating vertical-axis Savonius-style wind turbines. The simulation was fully three-dimensional and unsteady. Through the simulation, it was possible to assess the performance of a wind turbine that possessed novel features such as wing venting and blade caps. Results from the simulation were compared with experimental data and it was found that they were in general agreement. The simulations provide continuous information regarding air-flow patterns and velocity distributions during the rotation. Representative patterns of flow are shown.
Wind turbine use is expanding throughout the world as a means to provide electricity without contributing to the increase in global-warming gases. Most commonly, very large, horizontal-axis turbines are constructed in fleets that are connected to national-level electrical grid systems. More recently, there has been a desire for more local, small-scale power production that can be used to power very specific pieces of equipment or buildings. Some of the small-scale turbines are designed differently from their larger counterparts—they are driven by drag forces rather than by lift. Drag-driven turbines are typically called Savonius turbines. This paper, which presents a historical perspective on Savonius turbines, will illustrate their potential for providing local power. Finally, we will discuss recent developments in analysis methods which intend to optimize Savonius turbines for powering cellular communication towers in developing parts of the world.
A novel, vertical-axis turbine has been designed to meet a specific power-generation need. It is intended that the turbine will provide local electricity to off-grid cellular communication towers. It is intended that the turbine will reduce or eliminate the use of diesel-power generation for these towers and result in a reduction of operating costs and greenhouse gas emissions. The design effort has had two main stages. First, a prototype turbine blade was designed and tested in a large-scale wind tunnel. The initial design was based on available literature information. Subsequently, numerical simulations of the fluid flow patterns around the turbine blade were used to create improvements to the design. These improvements include the use of venting apertures in the turbine blade to reduce negative drag and thrust loading and the use of caps to improve power-generation efficiency. Through numerical modeling, significant improvements in performance were achieved resulting in a viable turbine design.
Savonius vertical axis wind turbines (VAWT) have advantages over horizontal axis wind turbines (HAWT) such as simple construction, acceptance. of wind from any direction without orientation, self-starting, inexpensive etc. These advantages make it a viable proposition for small-scale applications i n developing countries. In spite of the above advantages, VAWT are not gaining popularity mainly because of their poor efficiency. Hence, a three-bucket Savonius model rotor, having 8 cm bucket diameter and 20 cm height. was designed, fabricated, and tested in a sub-sonic wind tunnel. Provisions for variations of 'blade' ovelap were included. Experiments were conducted for overlap conditions in the range of 16% to 35%. From the experimental investigations, power coefficient (Cp) were calculated with and without blokage correction factors for tunnel interference. In both analyses, the power-coefficient increased if there was overlap, with an optimum value at 20% ovelrap of 47% without bockage correction, and 38% with blockage correction.
The present investigation is aimed at exploring the feasibility of Savonius wind turbine blades for power generation, which has hitherto been limited to water pumping and grain grinding work. In this project, an attempt has been made to develop a twisted blade for its use in Savonius wind turbine rotors. The objective is to reduce the negative torque and the self-starting characteristics of a single stacked rotor system while maintaining a high rotational speed so that such a rotor system can be used for electricity generation. Tests have been carried out of semicircular (curved) and twisted blades both in a three bladed rotor system. Aerodynamic performance of these blades have been evaluated in a low speed wind tunnel on the basis of starting torque, power output and rotational speed at various setting angles and gap widths. Experimental investigation shows the potential of the twisted bladed rotor in terms of smooth running, higher coefficient of performance and self-starting capability as compared to that of the semicircular bladed rotor.
Background: Modular endoprostheses can be used to reconstruct large osseous defects resulting from tumor resection, trauma, revision arthroplasty, or other causes. They historically have used polymethylmethacrylate cement for fixation to host bone. Newer designs incorporating stems that use cementless bone-ingrowth surfaces have become available, but it is not clear how these compare with cemented designs. Methods: We performed a retrospective review of all patients treated at our institutions who have had endoprosthetic reconstruction of the proximal femur, distal femur, or proximal tibia using cementless fixation and a single-stem type. The primary outcome was considered to be loosening or reoperation. Thirty-seven cementless modular endoprostheses were implanted in as a subset of endoprostheses used for reconstruction from 2002 through 2007. The decision to use cementless implants and particular stem choice was made by the primary surgeon based upon patient age, diagnosis, prognosis, bone quality, and surgeon experience. Results: Twenty-two distal femoral, 12 proximal tibial, and two proximal femoral prostheses were implanted, as well as one combined distal femoral and proximal tibial prosthesis, all with the same stem and technique. Kaplan Meier estimated implant survival was 89% at 4 years. Three patients developed loosening of their prosthesis that required revision. There were no periprosthetic fractures or implant breakage in our study. Conclusions: We demonstrated good short-term outcome of cementless fixation for modular endoprostheses with straight 127-mm stem. The complication rate was relatively low similar to previously reported results of cemented implants.
Rapid depletion rate of fossil fuels with an increasing energy demand and their high emission are imposing the evolution activities in the arena of renewable energy. To meet the future demands of renewable energy sources, wind energy is a very promising concept. In this feature, the drag based vertical axis wind turbines (VAWTs) are suitable for small scale wind energy generation for decentralized locations. However, these turbines have low power and torque coefficients as compared to other wind turbines. Numerous blade shapes have been proposed till now to improve the performance of these turbines. In the present paper, a computational study has been performed to simulate the air-flow over different blade profiles using shear stress transport (SST) k–ω turbulence model. The results obtained are validated with the available experimental data. In the dynamic simulations, the power and torque coefficients are calculated considering the blade arc angle as the variable shape parameter. The effects of drag and lift forces on the variable blade shapes are also studied in static simulations at various angular positions. The present paper tries to demonstrate an effective computational methodology to predict the flow behavior around a drag based VAWT. Through this study, it has been found possible to select an optimal blade shape from the point of its aerodynamic performance.
The renewed interest that is being paid by architects, project developers and local governments to small-size wind turbines is mainly connected to the attractive prospects of future applications in the urban environment; the delocalized power production of these systems could indeed provide an effective answer to both the growing demand for renewable energy and the increased attention in buildings with a sustainable and low-energy design. In particular, Darrieus vertical-axis wind turbines (VAWTs) are being considered as one of the most attractive solutions due to their low visual impact, the reduced acoustic emissions and their better response to a turbulent and skewed oncoming flow. The feasibility of this scenario has, however, to be proved yet; in particular, doubts are still connected to the real producibility in a complex terrain like the urban one and to the compatibility of microeolic machines with a densely populated area. On these assumptions, the aim of this work is to critically evaluate th
Many recent patents worldwide address the concept of harvesting wind energy from aerodynamic losses in motorways, however the mechanics of a specific device dedicated to the task has never been described. The lack of a characterization of the energy resource likely explains why the international market is still to acknowledge any technology related to the concept. Here, an experimental activity is presented to investigate the flow field generated by traffic in motorways and eventually develop an innovative technology that complies with emerging energy policies. In the case of traffic source, the energetic rationale seems to have a double motivation: there will always be an optimal energy supply associated with an increment in transport demand and, contrary to other renewables, the transport aerodynamic losses belong to a source of costs, making them a remarkably sustainable energy source. After a thorough analysis of the correlation between truck flow and wind speed classes, the characterization of a resource indicator for time of wind above a cut-in speed is given, with an account for the effects of traffic clusters and traffic related wind-drops. We demonstrate how during weekdays daytime hours the traffic-generated resource can allow an energy conversion beyond a threshold possibly permitting a positive energetic balance of the system. A study on the effect of traffic related wind-drops is also carried out to investigate how the issue could be relevant in the transient behavior and ultimately in the performance of a mini wind turbine in the kW-range. While many findings relate to the motorway site where the campaign was sited, fitting of the experimental data to the generic motorway case permits to explore a complete range of traffic flows.
An investigation into the blockage correction effects in wind tunnel experiments of a small-scale wind energy conversion system in an open type test section is carried out. The energy conversion system includes a Savonius-style wind turbine (SSWT) and a power measurement assembly. As the available correlations for the closed type test sections may not be appropriate for the open test section under dynamic loading conditions, new correlations are adapted for the blockage correction factors with free stream wind speed, turbine rotational speed and variable load applied to the turbine to quantify the energy conversion coefficients more precisely. These are obtained for a blockage ratio of 21.16% through a comparison of present experimental data with those of established experimental data under dynamic loading conditions. Further, the accuracy of the adapted correlations is substantiated into the experiments with smaller blockage ratios of 16% and 12.25%. The relationships of the tip speed ratios and blockage ratios with the blockage correction factor are also discussed. Using these correlations, this study provides evidence of increase of blockage correction in the range 1–10% with the increase of both tip speed ratio and blockage ratio. The results also indicate that for blockage ratios approaching 10 and tip speed ratios below 0.5, the blockage effects are almost negligible in the open type test sections.
An innovative idea on extracting clean energy from man-made wind resources with micro wind turbine system for power generation is introduced in this paper. This system generates on-site clean energy using a micro wind generation system. A vertical axis wind turbine (VAWT) with an enclosure is mounted above a cooling tower's exhaust fan to harness the wind energy for producing electricity. The VAWT is positioned at a specific position at the cooling tower outlet to avoid a negative impact on the performance of the cooling tower. The enclosure can act as a safety cover and also enhance the performance of the VAWT. It is designed with several guide-vanes positioned at the up-stream side of the wind turbine to create a venturi effect and guide the wind before it interacts with the turbine blades. Moreover, the enclosure design is comprised of diffuser-plates that can draw more wind and accelerate the flow. Laboratory test conducted on a scaled model shows no measurable difference in the air intake speed and current consumption of the power-driven fan when the turbine was spinning above the cooling tower. Field test on an actual induced-draft cooling tower shows no significant difference on the outlet air speed of the cooling tower. A small difference was observed on the power consumption by the fan motor which is 0.39% higher with the presence of the VAWT. This system is retrofit-able to existing cooling towers and has very high market potential due to abundant cooling towers and other unnatural exhaust air resources globally.
A novel omni-direction-guide-vane (ODGV) that surrounds a vertical axis wind turbine (VAWT) is designed to improve the wind turbine performance. Wind tunnel testing was performed to evaluate the performance of a 5-bladed (Wortmann FX63-137 airfoil) H-rotor wind turbine, with and without the integration of the ODGV. The test was conducted using a scaled model turbine which was constructed to simulate the VAWT enclosed by the ODGV placed on a building. The VAWT shows an improvement on its self-starting behavior where the cut-in speed was reduced with the integration of the ODGV. Since the VAWT is able to self-start at a lower wind speed, the working hour of the wind turbine would increase. At a wind speed of 6 m/s and under free-running condition (only rotor inertia and bearing friction were applied), the ODGV helps to increase the rotor rotational speed by 182%. With extra load application at the same wind speed (6 m/s), the wind turbine power output was increased by 3.48 times at its peak torque with the aid of the ODGV. The working concept of the ODGV is to minimize the negative torque zone of a lift-type VAWT and to reduce turbulence and rotational speed fluctuation. It was verified by re-simulating the torque coefficient data of a single bladed (NACA 0015 airfoil) VAWT published by the Sandia National Laboratories. From the simulation results, with the presence of the ODGV, it was shown that the torque output of the NACA 0015 airfoil, single bladed VAWT has been increased by 58% and 39% at TSR = 2.5 and TSR = 5.1 respectively. The negative torque zone has been minimized thus the positive torque that provides higher power can be obtained. As a conclusion, the ODGV integrated wind power
This paper presents a review on the performance of Savonius wind turbines. This type of turbine is unusual and its application for obtaining useful energy from air stream is an alternative to the use of conventional wind turbines. Simple construction, high start up and full operation moment, wind acceptance from any direction, low noise and angular velocity in operation, reducing wear on moving parts, are some advantages of using this type of machine. Over the years, numerous adaptations for this device were proposed. The variety of possible configurations of the rotor is another advantage in using such machine. Each different arrangement of Savonius rotor affects its performance. Savonius rotor performance is affected by operational conditions, geometric and air flow parameters. The range of reported values for maximum averaged power coefficient includes values around 0.05–0.30 for most settings. Performance gains of up to 50% for tip speed ratio of maximum averaged power coefficient are also reported with the use of stators. Present article aims to gather relevant information about Savonius turbines, bringing a discussion about their performance. It is intended to provide useful knowledge for future studies.
The rapid tidal current near a lake inlet is transformed into electrical energy with Darius-type hydraulic turbine generators. When the tidal power generation is insufficient, the stored excess electric power generated from midnight to early morning of a representative day is used. The balance of energy supply and demand for all sampling events in a representative day must be predicted very accurately in a system with energy storage. In this study, electric power and heat demand are forecasted on the basis of weather data obtained from the Internet, and the corresponding values are used to plan the storage of electricity and heat from midnight to early morning. The results of the case analysis show the influence of the economic efficiency of the heating system, the capacity of the tidal power generator, the prediction error of the tidal power generator, and the insulation efficiency (Q-value) on the energy cost. Optimization of the introduced simulation model was considered. The objective functions of optimization were minimization of operation cost and facilities cost of the simulation model.
An experimental investigation was carried out on a wind tunnel scale vertical axis wind turbine with unsteady wind conditions. The wind speed at which testing was conducted was 7 m/s (giving a Reynolds number of around 50,000) with both 7% and 12% fluctuations in wind velocity at a frequency of 0.5 Hz. Rotational speed fluctuations in the VAWT were induced by the unsteady wind and these were used to derive instantaneous turbine rotor power. The results show the unsteady power coefficient (CP) fluctuates following the changes in wind speed. The time average of the unsteady CP with a 7% fluctuation in wind velocity was very close to that with steady wind conditions while 12% fluctuations in wind speed resulted in a drop in the mean CP, meaning unsteady winds of such amplitudes are detrimental to the energy yields from these wind turbines. At mean rotational speeds corresponding to tip speed ratios (λ) beyond peak CP, no significant hysteresis was observed for both 7% and 12% fluctuations. However, substantial hysteresis is seen for conditions where mean λ is below peak CP.
In recent era, research and development activities in the field of renewable energy, especially wind and solar, have been considerably increased, due to the worldwide energy crisis and high global emission. However, the available technical designs are not yet adequate to develop a reliable distributed wind energy converter for low wind speed conditions. The Savonius rotor appears to be particularly promising for such conditions, but suffers from a low efficiency. Till now, a number of experimentations have been carried out in the area of Savonius rotor to increase its efficiency. These large-scale experimentations involve massive costs and hazards. In this context, computational studies have shown a significant importance to carry out the research with large number of physical designs and parameters. Over the past four decades, investigations have been carried out with various computational methodologies and turbulence models to optimize the different parameters and hence the efficiency of these rotors. In the present paper, a detailed review of various computational methods addressing the influence of various operating parameters and augmentation techniques has been reported. From this review study, it is observed that with the selection of a proper computational methodology, the design, performance, and efficiency of a Savonius rotor can be enhanced significantly.
The Savonius rotor is a drag-based vertical axis wind turbine and is used as an alternative source in small-scale energy generation. Design simplicity, low-cost, easy installation, good starting ability, relatively low operating speed and independent to wind directions are the main advantages of this rotor. However, because of its low efficiency and high negative torque produced by the returning blade, this rotor concept rarely gained popularity. Over the last few decades, although a number of investigations around the world have reported performance gains of the Savonius rotor, the available technical design is still not able to fulfill the demand of efficient small-scale wind energy converter at low wind speeds. Until now, various design changes have been proposed to meet a growth in power output through optimization of influencing variables like aspect ratio, overlap ratio, blade material, and so forth. Investigations have also been carried out by installing additional devices like curtain design, deflector plate, nozzle and ducts, multi-staging, guide-box tunnel and windshields. Installation of these devices considerably reduced the negative torque as well as improved the starting performance of the rotor. As a result, the power output of the rotor is also improved. Several researchers have reported increased power coefficients for various rotor designs based on their different testing parameters. Power coefficients for the conventional Savonius rotors have been mostly reported in the range of 0.12–0.18 and by optimizing its design, it can reach as high as 0.38. This article attempts to discuss the various influencing parameters as well as the augmentation techniques. This would offer an overall idea on the progress that has taken place to improve the design and performance of the Savonius rotor.
Savonius rotor is simple in design and easy to fabricate at a lower cost. The basic driving force of Savonius rotor is drag. The drag coefficient of a concave surface is more than the convex surface. Hence, the advancing blade with concave side facing the water flow would experience more drag force than the returning blade, thus forcing the rotor to rotate. Net driving force can be increased by reducing the reverse force on the returning blade. This can be realized by providing flow obstacle to the returning blade. The objective of the present work is to find out the optimal position of the deflector plate upstream to the flow which would result in maximum power generated by the rotor. Experimental investigations are carried out to study the influence of the location of the deflector plate on the performance of a modified Savonius rotor with water as the working medium at a Reynolds number of 1.32×105. Eight different positions of the deflector plate are attempted in this study. Results conclude that deflector plate placed at its optimal position increases the coefficient of power by 50%. Maximum coefficient of power is found to be 0.21 at a tip speed ratio of 0.82 in the presence of deflector plate. Two stage and three stage modified Savonius rotors are tested to study the influence of deflector plate at the optimal position. Maximum coefficient of power improves by 42%, 31% and 17% with deflector plate for two stage 0° phase shift, 90° phase shift and three stage modified Savonius rotor respectively.
An investigation into wake and solid blockage effects of vertical axis wind turbines (VAWTs) in closed test-section wind tunnel testing is described. Static wall pressures have been used to derive velocity increments along wind tunnel test section which in turn are applied to provide evidence of wake interference characteristics of rotating bodies interacting within this spatially restricted domain. Vertical-axis wind turbines present a unique aerodynamic obstruction in wind tunnel testing, whose blockage effects have not yet extensively investigated. The flowfield surrounding these wind turbines is asymmetric, periodic, unsteady, separated and highly turbulent. Static pressure measurements are taken along a test-section sidewall to provide a pressure signature of the test models under varying rotor tip-speed ratios (freestream conditions and model RPMs). Wake characteristics and VAWT performance produced by the same vertical-axis wind turbine concept tested at different physical scales and in two different wind tunnels are investigated in an attempt to provide some guidance on the scaling of the combined effects on blockage. This investigation provides evidence of the effects of large wall interactions and wake propagation caused by these models at well below generally accepted standard blockage figures.
Driven by the need to verify a CFD model of a novel vertical axis wind turbine (VAWT) device, a 1.6 m diameter prototype was designed, built to a high specification and tolerance and then tested in the industry standard MIRA wind tunnel over the full wind range that might be expected in an urban environment. Although the original intention was simply to provide data to verify a CFD model of the specific device – documented separately – it was realised that given (a) the repeatability and quality of the experimental data, and (b) its utility for the authors in verifying their CFD simulations, the data itself might well form the basis for a requirement for a reliable benchmark for the wind engineering community in assessing CFD simulation technology against a specific VAWT device design with the complexity of a housing. The experiments cover a full range of operational conditions for a specific design including the variation of wind speed, wind direction, tip speed ratio and blade pitch angle, recorded in the experiments as well as the torque output and the pressure levels at a range of specific locations. Over 60 tests were carried out in such a way as to assess the repeatability of the measurements; the results showed an overall remarkable degree of consistency.
Computational fluid dynamics (CFD) simulation tools are developed to analyse the aerodynamic performance of a novel design vertical axis wind turbine (VAWT) and compared against careful data from a 1.6 m diameter device in a wind tunnel. The study investigates the extent to which a CFD model employing the simplest turbulence representation can provide a useful input to evaluate the impact of several key operational parameters: wind speed, rotor speed, yaw angle and blade pitch angle. The results show that simple turbulence modelling techniques are sufficient to evaluate the performance of the turbine in the designed operating conditions and can predict when the turbine will run outside each parameter’s operational range. However, such a simple turbulence representation may need further refinement to quantify more precisely the extent to which performance is affected when running some way outside this range.
The main objective of this work is to determine and design a suitable wind turbine which could be employed for rural homes or other small-scale applications. A variety of horizontal and vertical axis wind turbines exist, each possessing a number of advantages and disadvantages which needed to be taken into account before a basis for the design is selected. A small robust design which is relatively simple and cheap to construct is in essence the main criteria for wind turbine selection. A Savonius type rotor, which is a rotor based on a modification of the ‘S’ rotor, is selected as it best fitted the design criteria. A small prototype 1.5 m tall with a rotor diameter of 0.65 m is designed and built. The finished prototype is used to estimate the power obtainable under normal operating conditions.
An extensive wind tunnel test program is described which assesses the relative influence of system parameters on the Savonius rotor performance. The parametric study leads to an optimum configuration with an increase in efficiency by around 100 percent compared to the reported efficiency of approx. 12-15 percent. Of particular interest is the blockage correction procedure which is vital for application of the wind tunnel results to a prototype design, and facilitates comparison of data obtained by other investigators. Next, using the concept of a central vortex, substantiated by a flow visualization study, a semiempirical approach to predict the rotor performance using measured stationary blade pressure data is developed. The simple approach promises to be quite effective in predicting the rotor performance, even in the presence of blockage, and should prove useful at least in the preliminary design stages.
UNCERTAINTY ANALYSIS IS THE PREDICTION OF THE UNCERTAINTY INTERVAL WHICH SHOULD BE ASSOCIATED WITH AN EXPERIMENTAL RESULT, BASED ON OBSERVATIONS OF THE SCATTER IN THE RAW DATA USED IN CALCULATING THE RESULT. THE PROCESS IS DISCUSSED AS IT APPLIES TO SINGLE-SAMPLE EXPERIMENTS OF THE SORT FREQUENTLY CONDUCTED IN RESEARCH AND DEVELOPMENT WORK. THE PREDICTED UNCERTAINTY IN A RESULT WILL DEPEND UPON THE NUMBER OF TERMS RETAINED IN THE ANALYSIS, AND THIS, IN TURN, IS DEPENDENT ON THE END-USE PROPOSED FOR THE UNCERTAINTY VALUE. THREE CONCEPTUAL LEVELS OF REPLICATION CAN BE DEFINED: ZEROTH, FIRST, AND NTH ORDER. THESE LEVELS OF REPLICATION ADMIT OF DIFFERENT SOURCES OF UNCERTAINTY. THE PROCESS IS EASILY ADAPTED TO COMPUTER-BASED DATA REDUCTION PROGRAMS.
The growing demand for renewable energy with a sustainable and low-energy design is the main topic in many countries. This could indeed influence in utilizing small wind turbines which incorporate innovative designs and new materials of construction which may provide an attractive prospect of future applications of power production in the urban environment. In particular, H-rotor type vertical axis wind turbines (VAWTs) are considered as one of the most attractive solutions due to simplicity and ease of manufacturing. Optimized site-specific designs proved reductions in cost of energy by increasing in
annual energy yield and a reduction in manufacturing costs. The greatest benefits were reported at sites with low mean wind speed and low turbulence. The terrain studied here is a site in Fadashk area in the province of south Khorasan in north east of Iran. The aim of this work is to design and optimize the site specific H-rotor type VAWT using the blade element momentum theory (BEM) and a double multiple stream tube model. The results of these analyses were then combined and synthesized for a 1.5 kW Hrotor VAWT with NACA4415 airfoil sections. The economical feasibility of the designed VAWT is finally
integrated in the design procedure to predict annual production of electricity. Based on current electricity costs that is 12 cent per kW h in Iran for renewable energies, our evaluation shows a profit of 6 cent per each kW h generated power by the designed VAWT.
Conventional Savonius or modified forms of the conventional Savonius rotors are being investigated in an effort to improve the coefficient of power and to obtain uniform coefficient of static torque. To achieve these objectives, the rotors are being studied with and without central shaft between the end plates. Tests in a closed jet wind tunnel on modified form of the conventional Savonius rotor with the central shaft is reported to have a coefficient of power of 0.32. In this study, modified Savonius rotor without central shaft between the two end plates is tested in an open jet wind tunnel. Investigation is undertaken to study the effect of geometrical parameters on the performance of the rotors in terms of coefficient of static torque, coefficient of torque and coefficient of power. The parameters studied are overlap ratio, blade arc angle, aspect ratio and Reynolds number. The modified Savonius rotor with an overlap ratio of 0.0, blade arc angle of 124° and an aspect ratio of 0.7 has a maximum coefficient of power of 0.21 at a Reynolds number of 1,50,000, which is higher than that of conventional Savonius rotor (0.19). Correlation is developed for a single stage modified Savonius rotor for a range of Reynolds numbers studied.
A Savonius rotor can develop a relatively high torque at a low rotational speed. It is cheap to build, but harnesses only a small fraction of the wind energy incident upon it. One proposal for augmenting the energy-harnessing effectiveness was to employ a V-shaped deflector mounted upstream of the rotor, apex into the wind, so that the air-flow resistance encountered by the half of the wind-turbine blade advancing (i.e. moving) into the wind was reduced. By (i) carrying out experimental tests with the deflector in different positions relative to the rotor, and (ii) varying the wedge angle between the deflector blades, an optimal configuration for the particular system tested was determined. With the optimally pitched deflector set at its optimal location, the rotor harnessed about 20% more power, compared with the unblocked (i.e. standard) rotor both for an approximate wind speed of 4 ms-1. Such a significant improvement, achieved by this simple cheap means, suggests that the use of the partially blocking wedge is highly desirable.
Parts of each Bach-type blade of a conventional Savonius rotor have been replaced by four flaps. These flaps open when moving into the wind, so the drag on the blade is then reduced. Thus approximately a 35% increase in average static torque has been achieved relative to that obtained with the original rotor of similar geometry, both experiencing an undisturbed wind of 6·67 m s -1. The torque developed over the whole rotation is positive, which is not the case with the conventional rotor.
This study investigates to improve and adjust the output power of Savonius rotor under various wind power and suggests the method of prevention the rotor from strong wind disaster. In this study, as the appropriate device to achieve the purpose of it, a guide-box tunnel is employed. The guide-box tunnel is like a rectangular box as wind passage in which a test rotor is included. The area ratio between the inlet and exit of it is variable to adjust the inlet mass flow rate or input power. At first, the experiment was conducted to find the adequate configuration which would provide the best relative performance. The present experiment, however, does not include the test to retain the guide-box tunnel from the strong wind.The experiments include the static torque test of the fixed rotor at any phase angle and the dynamic torque test at rotation of them. Consequently, it was found that the maximum rotor rotational speed was achieved in the range of the guide-box area ratio between 0.3 and 0.7 and the value of the output power coefficient of the rotor with guide-box tunnel of the area ratio 0.43 increases about 1.5 times with three blades and 1.23 times with two blades greater than that without guide-box tunnel, respectively. It seemed that the performance of Savonius rotor within the guide-box tunnel is comparable enough with other methods for augmentation and control of the output.
Conventional Savonius rotors have high coefficient of static torque at certain rotor angles and a negative coefficient of static torque from 135° to 165° and from 315° to 345° in one cycle of 360°. In order to decrease this variation in static torque from 0° to 360°, a helical Savonius rotor with a twist of 90° is proposed. In this study, tests on helical Savonius rotors are conducted in an open jet wind tunnel. Coefficient of static torque, coefficient of torque and coefficient of power for each helical Savonius rotor are measured. The performance of helical rotor with shaft between the end plates and helical rotor without shaft between the end plates at different overlap ratios namely 0.0, 0.1 and 0.16 is compared. Helical Savonius rotor without shaft is also compared with the performance of the conventional Savonius rotor. The results indicate that all the helical Savonius rotors have positive coefficient of static torque at all the rotor angles. The helical rotors with shaft have lower coefficient of power than the helical rotors without shaft. Helical rotor without shaft at an overlap ratio of 0.0 and an aspect ratio of 0.88 is found to have almost the same coefficient of power when compared with the conventional Savonius rotor. Correlation for coefficient of torque and power is developed for helical Savonius rotor for a range of Reynolds numbers studied.
The behaviours of the turbines' sails are described and the optimal sail profiles (corresponding to maximum wind harnessing capabilities) are identified. The taut sail system is the preferred design.
The present investigation is aimed at exploring the feasibility of twisted bladed Savonius rotor for power generation. The twisted blade in a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0°). Performance analysis has been made on the basis of starting characteristics, static torque and rotational speed. Experimental evidence shows the potential of the twisted bladed rotor in terms of smooth running, higher efficiency and self-starting capability as compared to that of the conventional bladed rotor. Further experiments have been conducted in the same setup to optimize the twist angle.
This paper describes the design approach to a four-stage Savonius-rotor-based irrigation system suitable for a small farm of ∼ 5 acres. The rotor construction based on an optimum configuration of the blade geometry and aspect ratio, as given by an extensive wind-tunnel test program. The essential features of the full-scale system, including the microprocessor-based braking and load-matching procedures, are described. The prototype, designed specifically for field tests, is provided with appropriate performance and meteorological information-monitoring instrumentation to permit their correlation. Based on the wind-tunnel data, the wind turbine is expected to deliver 10 000 l of water per day to a head of 4 m in a 20 km h−1 wind.