Hybrid Vertical Axis Wind Turbine Research Articles

Multi-objective optimization study on the performance of double Darrieus hybrid vertical axis wind turbine based on DOE-RSM and MOPSO-MODM

The Double Darrieus Vertical Axis Wind Turbine (DD-VAWT) effectively enhances wind energy efficiency at low tip speed ratios. In this study, the multi-objective optimization method is constructed for DD-VAWT. The optimization objective is to enhance the power coefficient as well as reduce the maximum instantaneous torque coefficient, while decision variables include the inner ring wind turbine diameter, inner ring wind turbine height, inner ring wind turbine blade airfoil chord length and inner and outer ring wind turbine phase angle. Firstly, the computational fluid hydrodynamics model of DD-VAWT is established and validated by experimental data from the literature. Then, the regression model between critical structural parameters and power coefficients, maximum instantaneous torque coefficients is constructed using response surface analysis. Finally, the multi-objective particle swarm optimization algorithm is used to optimize the objective and the optimal solution is selected from the Pareto frontier solution. This work provides a direction to improve the operating performance of DD-VAWT at low tip speed ratios as well as contributes to energy saving and emission reduction.

Enhancing vertical axis wind turbine efficiency through leading edge tubercles: A multifaceted analysis

This research paper aims to investigate the impact of leading edge tubercles (LET) on the performance of hybrid vertical axis wind turbine (VAWT). The study involves both experimental and computational analysis of a novel hybrid VAWT configuration. The proposed VAWT design is characterized by a high power coefficient and self-starting capability. To provide a basis for comparison, an existing hybrid VAWT without tubercles and a conventional H-Rotor Darrieus design were also examined. The findings indicate that the proposed hybrid VAWT achieved the highest power coefficient (Cp) of 0.475 at a tip speed ratio (TSR) of 3. Furthermore, the proposed wind turbine demonstrated superior Cp values at both low TSRs (1 to 2.1) and high TSRs (4.1 to 5) compared to the existing hybrid VAWT and the H-Rotor Darrieus turbine. The positive static torque coefficient (Cts) values observed at all azimuths, with a maximum value of 0.319, highlight the self-starting capability of the proposed hybrid wind turbine. The enhanced power coefficient and the ability to harness wind energy even at low wind speeds make the proposed hybrid wind turbine suitable for a wide range of power projects, from small to large-scale. This approach offers a means to determine the optimal design configuration for a hybrid VAWT and facilitates a detailed analysis during the early design stages, along with its high-fidelity characteristics.

VAWT support structure mass sensitivity due to aerodynamic load scaling

The X-rotor wind turbine is an X-shaped hybrid vertical axis wind turbine whose power take-off is done by horizontal axis rotors located at the tip of the lower blades. Based on an initial basic study, the present study developed a preliminary jacket design as the turbine support structure. Steady aerodynamic loads were obtained from an actuator cylinder model and dynamic load simulations including wave loads were performed. The structure was checked according to fatigue damage and maximum yielding for representative site-specific load cases for fatigue and ultimate limit states. Even though the use of a conventional jacket was shown to be feasible for the new turbine concept, the overall mass of the support structure obtained by the higher fidelity model was higher than the initial prediction. The design was driven by the fatigue damage, caused by large cyclical loads on every rotor rotation. The effect of a hypothetical aerodynamic load reduction on the jacket mass was investigated. The developed design methodology was also applied to the design of equivalent jackets after a load reduction of 75% and 50% and the mass of the structure was shown to be sensible, with a respective reduction of 25% and 48%. This result demonstrates that different design strategies that influence the magnitude of the aerodynamic loads (e.g. the control strategy) could lead to a more cost-efficient jacket design.

Characterization of a novel lift-drag-driven air-activated hybrid vertical axis wind turbine

Increasing electricity demand, concern about the environment, and scarcity of fossil fuels are propelling the present world towards renewable energy sources. Wind energy is one of the sustainable resources that have the potential to meet the escalating demand for power. The existing wind turbines come with many limitations which are affecting power generation. In this context, a new eccentric vertical axis wind turbine is proposed that has the attributes of both drag and lift-based turbines. The design aspects and detailed functioning of the turbine are discussed and the characteristics of the machine are predicted in the current study. It is observed that the proposed turbine is devoid of negative torque and its simulation demonstrates improved performance. The lift and drag coefficients of 0.529 and 0.0112 are obtained with the lift-to-drag ratio of 47.2. At a wind speed of 12 m/s, the proposed turbine produces 15.57 % more power than the H-bladed Darrieus rotor.

Experimental investigation and analysis of proposed hybrid vertical axis wind turbine design

In this research, an experimental and computational analysis of a novel hybrid vertical axis wind turbine (VAWT) arrangement has been performed. We suggest an innovative VAWT design that has a high power coefficient and self-starting capability. The inner side of the proposed hybrid system has been integrated with the H-rotor turbine with cambered blades, which demonstrates strong self-starting capabilities at various azimuths. Three NACA0018 airfoil blades are mounted on the outside of the proposed hybrid wind turbine, while three DU 06-W-200 airfoil blades are installed on the inside. Based on a similarity analysis, a scaled-down model was developed, and performance characteristics such as the output power, power coefficient ([Formula: see text]), dynamic torque coefficient ([Formula: see text]), and static torque coefficient ([Formula: see text]) were determined. An existing hybrid VAWT and a typical H-rotor Darrieus design were also examined for comparison. The highest [Formula: see text] for the proposed hybrid design was found to be 0.486 at a tip speed ratio (TSR) of 3, while the H-rotor Darrieus’ maximum value was 0.42 at a TSR of 2.62 and the existing hybrid VAWT’s value was 0.41 at a TSR of 2.5. Positive [Formula: see text] values at all azimuths demonstrate that the proposed hybrid wind turbine can start entirely on its own. In comparison to the existing H-rotor and hybrid VAWT, this novel hybrid system has shown enhanced performance parameters ([Formula: see text], [Formula: see text], [Formula: see text], output power) by around 11%–13% over a wide range of wind speeds.

Optimization of the Energy Capture Performance of the Lift-Drag Hybrid Vertical-Axis Wind Turbine Based on the Taguchi Experimental Method and CFD Simulation

In order to improve the energy capture performance of vertical axis lift wind turbines in a low wind speed environment, the drag wind turbine is employed to couple with the design of existing vertical axis lift wind turbines. In contrast to the existing literature, in this work, a computational model is proposed that can simulate the interaction between the turbine and the fluid. The effects of pitch angle (β), installation angle (θ), overlap ratio (ε) and diameter ratio (DL) on the energy capture performance of hybrid vertical axis wind turbines are systematically analyzed based on Taguchi and CFD methods. The results show that under the optimized parameter combination, the peak energy capture coefficient of the lift-drag hybrid wind turbine can be increased to 0.2328, compared with 0.0309 and 0.0287 of the pure lift and drag turbine, respectively. In addition, the result of the prototype test show that the optimized hybrid wind turbine not only has a better-starting performance but also has 2.0 times the output power of that of the lift wind turbine.

Experimental analysis of hybrid VAWT and the effect of semi-cylindrical attachment to the trailing edge

Vertical axis wind turbines (VAWTs) work efficiently in low wind speed regions and varying wind directions like urban environments due to their omnidirectional capability. The current study examines experimentally the performance of the H-Darrieus VAWT having NACA 0018 airfoil by use of semi-cylindrical attachments at the trailing edge and hybridization using two bladed S-Savonius rotor with zero overlap conditions. The rotor's static torque and dynamic performances are investigated at a low wind speed of 4 m/s. The results show that the semi-cylindrical attachment increases the range of positive static torque. The static torque of Darrieus with attachment at 90° inside is more consistent, which enhances the starting capability of the Darrieus turbine with a static torque coefficient of 0.031, which is 29.7 % higher than a simple Darrieus turbine. The hybrid configuration shows maximum dynamic torque only at the 90° azimuthal position. The power coefficient of all configurations with attachments is lower than simple Darrieus due to drag created by attachments. The power coefficient value of 0.03 for hybrid configuration is the highest, with a wide range of tip speed ratio (TSR).

3D CFD Modelling of Performance of a Vertical Axis Turbine

Recently, wind turbine research has switched focus to vertical axis wind turbines due to the extensive research that has been performed on horizontal axis wind turbines and the potential of vertical axis wind turbines in built-up areas. This study aims to analyse the performance of a small-scale hybrid vertical axis wind turbine that can switch from functioning as a Darrieus (lift) turbine to a Savonius (drag) turbine by rotating the blades. The turbine was analysed using 3D computational fluid dynamics (CFD) simulations in ANSYS Fluent as the primary method, and the findings were verified using wind tunnel experiments. During the analysis, design parameters such as the blade length, diameter, and number of blades were varied to determine if the design had room for improvement. It was found that the current design of the turbine has an optimal efficiency of 12.5% in the Darrieus configuration, which was found to increase when the diameter or blade length was increased. The Savonius configuration was found to be more efficient at low tip-speed ratios (<0.14), and its efficiency could be increased by adding more blades. The experiments found similar trends to the simulations; however, the efficiencies obtained were on average a tenfold increase from the simulation. Implementing the changes that increased efficiency leads to an increased wake recovery distance, making it less suitable for use in a wind farm.

The Effect of Rotor Radius Ratio on The Performance of Hybrid Vertical Axis Wind Turbine Savonius-Darrieus NREL S809

This research aims to know the effect of the Rotor Radius Ratio on the performance of the hybrid Vertical Axis Wind Turbine Savonius-Darrieus NREL S809 model using the Computational Fluid Dynamics method. Two-bladed Savonius is used as an internal rotor, and three-bladed Darrieus NREL S809 as an external rotor. Turbine model performance is analyzed through the value of the Moment Coefficient and Power Coefficient. The result shows that the increase in the Rotor Radius Ratio value causes an increase in the initial Moment Coefficient but a decrease in the maximum Power Coefficient value. At the initial TSR, the Rotor Radius Ratio 0.5 model has the best Moment Coefficient value among all variations but has the lowest maximum Power Coefficient value.

The effect of steering tail fin on performance on double pillars hybrid vertical axis wind turbine (Sultan Wind Turbine V-4.5)

One of the methods to increase the efficiency of wind turbines is to add directional fins so that the wind turbine faces and is in the same direction as the wind. The use of triangular fins will slightly increase the performance of wind turbines compared to rectangular and trapezoidal shapes. The most crucial factor is that the fin area is not less than 5% of the swept area on the turbine blades. And according to calculations and simulation data, the convex pentagonal shape generates the greatest power. While the tests conducted by P.R. Ebert et al, that a twin wing with a high wing angle shows a greater damping response than a single wing. The aim of this research is to optimize the performance of the Sultan V-4.5 wind turbine by adding guide fins. Simulation methods and design of directional fins were carried out to obtain the most suitable fin shape and size. By using an aspect ratio of 1.4, the distance from the center of gravity to the center axis of the turbine is reduced. Performance tests were carried out using fins with areas of 0.06 m 2 , 0.12 m 2 and 0.22 m 2 . Twin fins are used, with a 30 o angle between them, to reduce the oscillatory forces resulting from wind motion. Fin profiles with maximum force when exposed to wind at angles of 0°, 5°, 10°, 15°, 20°, 25°, and 30° were selected from the available profiles using Computer Fluid Dynamic analysis. To determine the most suitable structure and material for fins, simulate the topology optimization and material selection used. According to his findings, the isosceles and right-angled triangles, which produce forces of 0.91 N and 0.77 N respectively, are the strongest. PVC plates are the materials used. The results of this study indicate that 2 m/s wind speeds frequency, the type 3b fin designs are the best design according to performance tests. The end result, coefficient of power increases and power generates increases respectively 5 and 3.8 times the previous research.

An overview of aerodynamic performance analysis of vertical axis wind turbines

In this paper, an attempt has been made to highlight major developments of vertical axis wind turbines (VAWTs) in the last few decades. The effects of various design parameters such as airfoil, number of blades, solidity, aspect ratio, blade helicity, and overlap ratio have been critically analyzed. Wind energy is the most promising renewable, cost-effective, efficient, and accessible source for both domestic and commercial applications. Horizontal axis wind turbines are highly developed and are being used for medium-to-large scale power projects. VAWT are considered viable options for urban and semi-urban areas. These turbines have several characteristics, such as omnidirectional, power generation in weak and unstable winds, esthetically sound, safety, and low noise. Darrieus turbines with a fixed blade-type have starting problems at low wind speeds. Savonius turbines have good starting capability; however, their power coefficients are lower than other types of VAWT. To overcome the shortcomings of conventional wind turbines, an innovative engineering solution was sought in the design of hybrid VAWT. The analysis revealed that hybrid wind turbines have addressed the deficiencies to an extent; however, the overall performance is still less than that of conventional wind turbines. Several recommendations have been made based on state-of-the-art information from the perspective of future studies and acceptability. It was concluded that vast opportunities for wind turbine applications are available in urban areas; however, further academic research is required on critical aspects such as self-starting at low wind speeds, efficiency, structural reliability, design improvement for aerodynamic performance, and wind resource assessment.

Design optimization of Double-Darrieus hybrid vertical axis wind turbine

This research emphasizes designing a straight-bladed Double-Darrieus hybrid vertical axis wind turbine (VAWT) with a high power coefficient as well as self-starting capability. Computational fluid dynamics analysis was performed using the sliding and dynamic meshing techniques. Various datasets were employed in the design of experiments to determine optimal configurations. A quadratic equation based on a regression model was established, and response surface methodology was applied to determine the accuracy of the model by analysis of variance, goodness of fit, investigation of residuals, and R-squared values. The optimized chord length, number of blades, pitch angle, distance of blades from the central rotating shaft, and rotor height were obtained as 0.547 m, 03, -3.41 deg, 0.789 m, and 1.605 m, respectively. A standard H-rotor Darrieus configuration, comprising symmetric airfoils and existing Darrieus-Savonius hybrid VAWTs were also analyzed for comparison. The positive static torque coefficient at all azimuth angles indicates that the proposed hybrid wind turbine is completely self-starting. The output power of the standard Darrieus configuration is substantially zero below a wind speed of 3.65 m/s, indicating that it is not capable of converting the kinetic energy of the airflow into electrical power below this specified value. On the contrary, the self-starting speed of the proposed hybrid wind turbine is as low as 2.81 m/s with a rated power of 1.522 kW at a wind speed of 7.5 m/s. The capability of the proposed hybrid wind turbine with a better power coefficient and transforming wind energy, even at low wind speeds, extends its utilization for various small to large-scale power projects. The proposed approach enables the determination of the optimum design configuration of a hybrid vertical axis wind turbine, along with a high-fidelity analysis in the early design phase.

On the application of semicircular and Bach-type blades in the internal Savonius rotor of a hybrid wind turbine system

In the present study, a comparison has been performed numerically to explore the impact of internal rotor type on power characteristics of a two-bladed hybrid vertical axis wind turbine (VAWT). For this purpose, the internal rotor of a hybrid wind turbine built with the conventional semicircle and Bach-type blades is considered under two free-wind speeds (U∞) of 5 and 10 m/s. Computations are conducted at three tip speed ratios (TSRs) of 1.5, 2.5, and 3.5. Effects of different relative positions between the external and internal rotors, called attachment angle, (φ) such as 0°, 45°, and 90° are studied in detail and the obtained results are validated against the available data for Darrieus and Savonius rotors, separately. The results illustrate that the internal rotor type, attachment angle, and TSR have considerable impacts on the hybrid rotor performance. Moreover, it is demonstrated that the Bach-type Savonius rotor has better performance than the conventional semicircle one in a two-bladed hybrid wind turbine regardless of φ, TSR, and U∞. The maximum improvement of 20% is reported for hybrid wind turbine equipped with Bach-type rotor under φ = 90°, TSR = 1.5, and U∞ = 5 m/s.

A hybrid, self-adapting drag-lift conversion wind energy harvesting system for railway turnout monitoring on the Tibetan Plateau

Increasing numbers of turnouts are being laid, with the rapid development of high-speed railways on the Tibetan Plateau. Ensuring the proper operation of turnouts has received considerable critical attention. In this paper, a hybrid wind energy harvesting system (WEHS) based on self-adapting drag-lift conversion is designed to power high-speed railway turnout monitoring on the Tibetan Plateau. The system contains three parts: a hybrid vertical axis wind turbine (VAWT), a power generation module, and an energy storage module. Equipped with variable pitch blades, the proposed VAWT can be adaptively converted between lift mode and drag mode in upwind areas and downwind areas, respectively. A maglev generator and supercapacitor are adopted as power generation and energy storage modules. Numerical simulation indicates that the maximum power coefficient of the VAWT is 0.381. According to experiments, the maximum output power of the prototype is 2.46 W, and the maximum average power is 1.08 W. The Sichuan-Tibet Railway was adopted as a case study to investigate the feasibility and the annual power generation of the proposed system is 57.651 MWh. Results illustrate that the proposed WEHS is feasible and practical for powering high-speed railway turnout monitoring on the Tibetan Plateau.

Effects of internal rotor parameters on the performance of a two bladed Darrieus-two bladed Savonius hybrid wind turbine

The hybrid vertical axis wind turbines (VAWTs), which are constructed by a combination of the Savonius and Darrieus rotors, have recently been proposed to improve the wind energy extraction from the free-wind flow. This study focuses on the impact of internal rotor parameters on the aerodynamic performance of the resultant hybrid rotor. For this goal, a two-blade Savonius rotor constructed by conventional semicircle blades with a constant overlap ratio of 0.2 is attached to a two-blade Darrieus rotor constructed by straight NACA 0018 blades. The resultant hybrid rotor has a constant diameter ratio of 0.2. To assess the Savonius wind turbine parameters, three various attachment angles of 0°, 45°, and 90° are examined under various wind potentials having average wind speeds of 5 and 10 m/s. A set of computations is performed at different tip speed ratios (TSR) of 1.5, 2.5, and 3.5. The obtained results have been validated against the available data for both Savonius and Darrieus rotors and good agreements are obtained from these comparisons. It is revealed that selecting an appropriate attachment angle is strongly dependent on the free-wind speed and TSR. Additionally, regardless of the free-wind speed, the hybrid rotor with an attachment angle of 45° presents the maximum power coefficient among the hybrid and non-hybrid rotors for TSR = 1.5 and 2.5. However, at TSR = 3.5, the hybrid rotor with ϕ = 0° and Darrieus rotor exhibit optimal performances among the considered cases at U∞ = 5 m/s and 10 m/s, respectively.

Design and Testing of Building Integrated Hybrid Vertical Axis Wind Turbine

Building integrated wind turbine are considered as part of a group of technologies that are suitable for domestic micro-energy generation. Darrieus and Savonius turbines work efficiently in the urban environment at low wind speed, the Savonius rotor is self-starting and creates high torque but has low efficiency, while the Darrieus rotor is very efficient but does not self-start easily. Thus, the combination of these rotors as hybrid system would help to improve the overall efficiency of the wind turbines. The aim of this paper was to design, fabricate and experimentally investigate the performance of hybrid Vertical Axis Wind Turbine (VAWT) on residential buildings. A building model with gable rooftop was design and fabricated for use in testing of the hybrid VAWT. The height of the hybrid VAWT was paced at <I>Y</I> = 150 mm above the rooftop. The results obtained from the studies showed that the hybrid VAWT mounted on the building rooftop yield up to 63% more energy compared to the bare-hybrid VAWT (without building). Similar improvement in performance of the hybrid VAWT is also observed in the rotational speed, mechanical power and the coefficient of torque, where the building integrated hybrid VAWT outperformed the bare-hybrid VAWT. Thus the results indicate that urban buildings are suitable for the mounting of the hybrid VAWT.

A Study of CFD Analysis with OpenFOAM of a Hybrid Vertical Axis Wind Turbine Combining Straight Blade Darrieus-type and Cross-flow-type Wind Turbines

A Study of CFD Analysis with OpenFOAM of a Hybrid Vertical Axis Wind Turbine Combining Straight Blade Darrieus-type and Cross-flow-type Wind Turbines

Free and Forced Vibration Analysis of H-type and Hybrid Vertical-Axis Wind Turbines

Vertical-axis wind turbines (VAWTs) are compact and efficient and have become increasingly popular for wind energy harvesting. This paper mainly focuses on free and forced vibration analysis of two different types of VAWTs, i.e., an H-type VAWT and a new hybrid VAWT. The H-type VAWT has a lower cost, while the hybrid VAWT has a better self-starting capability at a low wind velocity. Both of them can be used for wind energy harvesting. By using the assumed modes method, the two VAWTs are simplified by a single degree-of-freedom (SDOF) model. By utilizing the method of structural mechanics, a multi-degree-of-freedom (MDOF) model is developed for the two VAWTs and the turbines in them are reasonably simplified. Natural frequency analyses for the SDOF and MDOF models of the two VAWTs are conducted. A beam element model (BEM) of the two VAWTs is created to calculate their natural frequencies and mode shapes and to verify natural frequency results from the SDOF and MDOF models. By using the BEM of the two VAWTs, their amplitude-frequency responses are obtained from harmonic response analysis. To analyze forced vibrations of the two VAWTs, aerodynamic loads on the two VAWTs are obtained from computational fluid dynamics (CFD) simulation. By using solid element models of the two VAWTs, forced transient responses of the two VAWTs are calculated by using the aerodynamic loads from CFD simulation. Steady-state forced response amplitudes of the 1 m-mast hybrid VAWT are 23.8% and 20.5% smaller in X- and Y-directions than those of the 1 m-mast H-type VAWT, respectively. Frequency contents of the aerodynamic loads from CFD simulation are calculated, which confirm that they are periodic, and the power efficiency of the H-type VAWT is about 2.6% higher that of the hybrid VAWT.

Performance analysis of a hybrid vertical axis wind turbine through CFD for distributed generation in rural areas of Peru

Currently, in the developing countries of Latin America there is a great deficiency in the transmission of energy. In Peru, being a developing country, there are many rural areas and indigenous and peasant communities that do not yet have access to electricity due to the difficult access or cost of installing transmission lines in their location. Therefore, the present work will briefly evaluate the current situation of the country and, from that, will formulate a solution based on the development of distributed generation systems using small wind turbines. For this purpose, this paper will develop the preliminary performance analysis of a hybrid vertical axis wind turbine (VAWT) by using the computational fluid dynamics (CFD), for this, the data of the wind resource of Cajamarca, a province in Peru, will be used for this analysis because in this province there is a great wind resource. Even a short aerodynamic and efficiency study was carried out in order to characterize its behaviour with different air flows as they are found in many rural sectors of Peru.

Design, Fabrication and Performance Evaluation of Hybrid Vertical Axis Wind Turbine

Vertical axis wind turbines (VAWT) have attracted a lot of attention recently as an efficient tool in harnessing wind energy; however these types of wind turbine are faced with some challenges which affect their overall performance. The Darrieus rotor has difficulty to self-start by itself while the Savonius rotor has low efficiency. The performance of these turbines can be improved by combining the two VAWTs as one system. This paper presents the design of a hybrid VAWTs turbine. The Hybrid VAWTs combines the Darrieus rotor and the Savonius rotor as a single system to produce a high starting torque and enhanced efficiency. The Savonius rotor is placed at the centre of the three vertical blades of the Darrieus H-rotor to form the hybrid VAWTs. The hybrid VAWT was tested at four different wind speed i.e. V = 4.80 m/s, 4.50 m/s, 4.30 m/s and 3.90 m/s respectively. The performance of the hybrid VAWT was compared with the conventional straight bladed VAWT under similar experimental conditions. The obtained results showed that there is substantial improvement in the self-starting ability and coefficient of power (Cp). At V = 4.80 m/s, the Cp values for hybrid VAWT increased by 92% compared to straight bladed H-rotor VAWT. Similar improvement was also observed at wind speed of V = 4.50 m/s, 4.30 m/s, and 3.90 m/s where the Cp values increases by 71%, 10%, and 67% respectively compared to the straight bladed H-rotor.