Single Rotor Wind Turbine Research Articles

The influence of the rotor spacing distance and rotating speed ratio on the power production of dual rotor wind turbines using a modified two-way interaction blade element momentum method

The present study aims to develop an accurate and fast improved blade element method (BEM) with two-way rotor-rotor interaction model which can account for two-way rotor-rotor interaction and the influence of rotor spacing while most previous BEM models for co-axis dual rotor wind turbines (DRWT) ignore the rear to front rotor interaction effect. A modified BEM model distinct from computationally intensive Computation Fluids Dynamics (CFD) model, is proposed for DRWTs. Validation of the present model is conducted by comparing it with experimental data from referenced literature for both co- and counter-rotating configuration. In our case study, for both co- and counter-rotating configurations, the power coefficient (CP) maps exhibit a double-hump shape instead of a single peak on the power output -λ curve observed in a single rotor wind turbine system. This characteristic may lead the DRWT to a local CPmax condition rather than the global CPmax while pursing the optimum operational condition. Although the counter-rotating DRWT can achieve a higher CPmax for most rotor spacing ratio (S/R) cases, it exhibits inferior power output than the single rotor for the S/R = 0.1 case. The present model can serve as a rapid and accurate model for configuring and control strategy evaluating DRWTs.

About control of bi-wind turbine single-point-moored floating offshore wind turbines

In the last years, several novel floating offshore wind energy concepts have appeared in the market, whose goal is the reduction of floating offshore wind energy costs. Among them, bi-wind turbine floating offshore wind turbines, which use a single floating platform to place two wind turbines, are one of the most promising ones. However, they face some challenges in their full deployment. For example, depending on the wind direction, one of the rotors could be found downstream of the other one and hence be affected by its wake. To avoid this, the turbines of this type of systems do not use a conventional active yaw mechanism, but a single-point-mooring configuration, to allow the platform rotation around the vertical axis. This way, the alignment of the rotors with the wind can be achieved, avoiding wake issues. However, as stated in the literature, at least for single-rotor wind turbines, this alignment is not straightforward and some yaw drift could appear in the platform. Therefore, the main goal of this paper is to confirm that this platform yaw drift could also arise in bi-wind turbine single-point-moored floating wind energy systems, and analyse its impact in terms of performance, while shedding some light on the performance improvements when applying new advanced control strategies.

Technical, Economical, and Marketing Analyses of Corotating Dual‐Rotor Wind Turbines

In this study, a comprehensive analysis is done on a dual rotor wind turbine (DRWT) in co‐rotating arrangement. First, a co‐rotating dual rotor is designed and its performance is analyzed by blade element momentum theory simulation. Later, the designed co‐rotating DRWT is manufactured and then tested in the field by mounting the wind turbine on a truck. Running the truck steadily at different speeds while logging the performance parameters of the wind turbine, the power curve of the DRWT is obtained. Then, using the power curve of the co‐rotating DRWT and the actual wind measurement data from Çatalca Istanbul, the annual electricity generation of the designed turbine is calculated. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to single rotor wind turbines (SRWTs), in accordance with the literature. Analyses show that with DRWT, around 22% higher power generation can be achieved. Additionally, the payback period for DRWT was found to be less than 1 year. The marketing strategy for introducing the product emphasizes identifying and targeting early adopters and influencers within the market. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to SRWTs, in accordance with the literature.

Investigation of the performance of a horizontal-axis dual rotor wind turbine

Recent years have seen a rise in interest in wind energy as a useful alternative to harmful energies like fossil fuels. The dual rotor wind turbine (DRWT) offers more rapid rates of wind energy extraction. The current study intends to compare the performance of the turbine with and without the addition of a second rotor. Additionally, it examines how tip speed ratio and phase shift angle will affect DRWT performance. Realizable k-shear stress transport turbulence models are used to solve the three-dimensional, turbulent, stable, and incompressible flow equations for the performance of dual-rotor wind turbines. Domain-independence tests and an impartial mesh test are run to assess the results and ensure their accuracy. The researcher relies on previous studies while constructing the single rotor wind turbine model. This model uses an S826 airfoil. The front and rear rotors are given streamlined representations using ANSYS, according to the researcher. The independent mesh test indicates that the mesh density has 11.5 million elements. The experiment's results show that the DRWT has a significant effect on the efficiency of wind energy.

Design and comparative analysis of dual rotor wound field excited flux switching generator for household DC microgrid system with rooftop wind turbine

In this paper, two variants of the magnetless dual rotor wound field excited flux switching generator (DRWFEFSG) are comparatively analyzed for single rotor wind turbine (termed as machine I (MI)) and counter rotating wind turbine applications (termed as machine II (MII)) for household direct current (DC) microgrid system. First, design concept and integration to wind turbine system are discussed. Secondly, comprehensively performance analysis i.e., static analysis, dynamic load/speed analysis and electromagnetic performance analysis are executed. Finite element analysis (FEA) based static analysis evident that MI offers 7.6% higher torque in inner rotor whereas MII exhibits 18% higher torque in outer rotor. Dynamic respond unveils that in comparison to MII, MI suffers from the issue of voltage regulation. Additionally, electromagnetic analysis reveals that both MI and MII exhibits excellent response under variable field Magneto-motive force (MMF). Comparative analysis unveils that MII requires lower field MMF to achieve same response to counterpart MI. Quantitative analysis divulge efficiency of 88.49% and power factor of 0.93 in MI whereas MII at rated operating point demonstrates 85.9% efficiency and 0.96 power factor. Finally, effectiveness of the study and validity of DRWFEFSG for wind turbine applications are tested with hardware prototypes of both MI and MII that fairly matched with FEA results.

Analysis of Contra-Rotating Brushless Integrated Flux-Modulation Machine With Open-Slot Structure for Wind Power Generation

This paper presents a contra-rotating (CR) brushless integrated flux-modulation (BIFM) machine with open-slot structure for wind power generation, termed CR-BIFM machine. The presented machine employs two contra-rotating rotors coupled with two sets of wind turbine blades, thus being able to capture more wind energy than conventional single-rotor wind turbines. Due to the dual flux-modulation effect and flux-bridge effect, the presented machine exhibits high torque/power density, making it suitable for direct-drive wind power generation without issues related to mechanical gearboxes. As two sets of windings share the same stator slots in the presented machine, the decoupling design of windings is systematically investigated from the perspective of air-gap modulated magnetic field, considering the influence of both stator and rotors. The advantages of the presented machine are comprehensively evaluated compared to the baseline machine, showing that the presented machine exhibits higher torque/power density, higher efficiency, higher power factor, higher PM utilization, and better vibration performance. Finally, a prototype is fabricated and tested to validate the analysis.

Yaw control strategies for 20 MW multi-rotor systems

In this paper, the control of an active yaw system for a 20 MW multi-rotor wind turbine system (MRS) is considered. The MRS under investigation consists of five 4 MW turbines in two rows, which are connected to the tower via a space frame. A central yaw bearing at the height of the lower rotors is provided for active yaw. The paper aims to show that active aerodynamic yaw is possible by changing the thrust of certain rotors and should be considered for further research in the field of yawing of an MRS. Two different simulation environments are used in the paper. The MRS is modeled and simulated in Matlab/Simulink. Simulink’s own control modules are used as controllers. In the other simulation approach, the same MRS is modeled and simulated in Bladed and controlled with an external controller based on C++. The use of Bladed and Matlab/Simulink enables the plausibility and verification of the results. Matlab/Simulink is faster based of its simpler models but Bladed is more sophisticated. This paper also briefly presents the state of the art for yaw systems and yaw control of conventional single rotor wind turbines and initial research literature on yaw control of MRS.

Multi Rotor Wind Turbine Systems: An Exploration of Failure Rates and Failure Classification

The Multi-Rotor System (MRS) is a proposed solution to the increasing costs associated with the manufacture and maintenance of large single-rotor wind turbines. The MRS consists of many small rotors that can capture the same amount of energy as a large turbine but with the added benefits of standardization, reduced system loads, and improved reliability due to the redundancy of components and smaller size. However, modelling the operation and maintenance (O&M) of the MRS presents several challenges, including a lack of available failure data. This work aims to determine, what failure rate reduction, can MRS be competitive with equivalent single-rotor wind farms, using existing single-rotor turbine data as a baseline. The key failure components are identified through the use of a cost-based comparison parameter. Statistical and theoretical approaches are then used to analyse the impact of fatigue on failure rates for downscaled turbines, to determine if the required reduction in failure rate is feasible. Using a case study, the sensitivity of availability, operational expenditure, and lost revenue to failure rates is also determined.

Numerical study of aerodynamic performance of horizontal axis dual-rotor wind turbine under atmospheric boundary layers

The use of horizontal axis dual-rotor wind turbine (DRWT) is a new strategy to enhance the capture rate of wind energy and increase the performance of wind farms. An actuator line model (ALM) and large eddy simulation(LES) are introduced to investigate the aerodynamic performance of DRWT, and its effects on downstream turbines under convective atmospheric boundary layer (CBL) and neutral atmospheric boundary layer (NBL). The results conclude that the dominant vibration frequencies of the power production for the front rotor of DRWT are nearly the same as those of the single-rotor wind turbine (SRWT) under both NBL and CBL, but the vibration amplitude is slightly higher. The strength and dominant frequencies of yaw moment (Myaw) for the front rotor of DRWT are almost the same as those of the SRWT in both NBL and CBL flows, while the results of blade-root out-of-plane bending moment (Moop) are different. There are obvious differences in wake development and wake meandering between the DRWT and the SRWT. For three turbines cases, the total power production is increased respectively by 3.3% and 3% under NBL and CBL at a tandem spacing of 5D when the DRWT is placed in the first row, while the results increase to 5.5% and 4.4% at a tandem spacing of 9D. The stability of Myaw and Moop of second-row turbine located 5D downstream behind the DRWT under both NBL and CBL and Moop of all turbines located behind the DRWT in three tandem spacings (5D, 7D, 9D) under CBL are deteriorated compared with those located behind the SRWT.

OPTIMALISASI METODE BLADE TURBIN ANGIN SUMBU HORIZONTAL

The utilization of wind turbines is able to convert wind energy into electrical energy. It is recorded from the DG of NREEC source that Indonesia has a wind energy potential of 60.6 Giga Watt (GW) with a total renewable energy potential of 442GW. One of the most common types of wind turbines is the horizontal axis wind turbine. This study uses a literature study method that aims to compare and summarize data optimizing variations in the number of blades and wind speed on horizontal axis wind turbines from various sources. The results of the study are known that the pinwheel power generated by the rotation of the pinwheel blade produces energy that is converted into electrical energy. The wind speed and blade rotation yield are directly proportional to the energy produced. The greater the wind speed given to the turbine, the higher the rotation. Variations in the number of blades result in variations in rotational properties, since the effect of the ratio of tip speed is inversely proportional to wind speed. The performance of horizontal axis wind turbines can be optimized by applying blade design using chord and twist linearization methods. The greatest efficiency of the counter-rotational horizontal shaft wind turbine is achieved at a blade angle of 10° and a wind speed of 4.03m/s, resulting in a maximum efficiency of up to 71.8%, which is higher than the optimal single-rotor power coefficient of 59%. This means dual-rotor wind turbines are more efficient at converting energy than single-rotor wind turbines.

Experimental Study on the Effect of the Blade Tip Distance on the Power and the Wake Recovery with Small Multi-Rotor Wind Turbines

In order to investigate the output power and wake velocity of small multi-rotor wind turbines compared to single-rotor wind turbines, which operate in the same swept area at various blade tip distances, this paper used the wind tunnel test method to examine single-rotor wind turbines with diameter D of 0.4 m and 0.34 m corresponding to the triple-rotor wind turbines and double-rotor wind turbines with a single rotor diameter D of 0.24 m, respectively. The experimental results indicated that, without rotation speed control, the triple-rotor wind turbine produced more power than the single-rotor wind turbine with an equivalent swept area and that the output power tended to rise initially and then fall as the distance between each rotor increased. Moreover, the power increase reached a maximum of 8.4% at the 0.4D blade tip distance. In terms of wake measurement, triple-rotor wind turbines had smaller wake losses and faster recovery rates than single-rotor wind turbines. The smaller the blade tip distance, the earlier the wake merged and fused and the faster the recovery rate. In designing small multi-rotor wind turbines, the above discussion can serve as a guide.

Effect of yaw on aerodynamic performance of co-planar multi-rotor wind turbines

The multi-rotors wind turbine (MRWT) is a promising alternative to the large-scale single-rotor wind turbine for reductions of cost. Noteworthy, yawing in MRWT is a key engineering issue for its significant effect on the output power and structural aerodynamics. In this study, the aerodynamics and near wake dynamics of a co-planar multi-rotor wind turbine with different yaw modes (self-yaw and whole yaw) are investigated through the ALM-LES method. Comparatively, the effects of the blade tip vortex interactions between adjacent rotors on both the torque and thrust of the rotor and the mixing and recovery of the wake are taken into account as well. The numerical results show that the wake vortices of the two rotors attract and approach each other under self-yaw conditions. In the whole yaw conditions, the blade tip vortex in the region between rotors appears to neutralize each other due to the opposite direction of self-rotation of the wake vortex. Moreover, the wake enhancement effect increases the inlet velocity on the blades and has almost no effect on the lift-to-drag ratio. Nevertheless, the direct influence of the blade tip vortex increases the lift-to-drag ratio and decreases the inlet velocity at the location of 0.8∼1R on the front rotor blades in the self-yaw condition; it also decreases both the lift-to-drag ratio and the inlet velocity on the rear rotor blades. Furthermore, under the whole yaw condition, such a direct influence decreases the lift-to-drag ratio on the blades of the two rotors at the location of 0.8∼1R, and increases the average inlet velocity. Conclusively, among the investigated two yaw conditions, a 15°yaw angle shows a more considerable effect on the aerodynamics MRWT than the interaction of blade tip vortex.

Numerical Investigation on Aerodynamic Characteristics of Dual-Rotor Wind Turbines

Improving power output and reducing costs are crucial to the sustainable development of offshore wind power. In the present study, a dual-rotor wind turbine (DRWT) is proposed to improve wind energy capture efficiency by adding an auxiliary rotor behind the main rotor. The two rotors can be the same size or different sizes. This will result in different aerodynamic characteristics for DRWTs. In this paper, the NREL Offshore Baseline-5 MW and the NREL 750 kW single-rotor wind turbines (SRWTs) are used to configure three different types of DRWTs. The power output and wake characteristics of three different DRWTs with co-rotating (CO-DRWT) and counter-rotating (CR-DRWT) configurations on an actual scale are compared. The Reynolds-averaged Navier–Stokes (RANS) model with k-ω SST (shear stress transport model) is used to simulate the unsteady flow generated by the DRWT’s rotation. The present numerical results show that the power coefficient of the 5 MW-5 MW CO-DRWT can reach 1.22 times that of the 5 MW SRWT. Moreover, a faster wake velocity deficit recovery is found in the 5 MW-5 MW DRWTs because the high-velocity flow caused by the merging and mixing of the trailing vortices of the 5 MW-5 MW DRWTs brings an energy supplement to the wake velocity deficit.

Low-Cost, Low-W Low-Cost, Low-Weight T eight Test Rig Design for a Labor est Rig Design for a Laboratory-Scale y-Scale Twin Rotor Wind Turbine

Multi-Rotor Wind Turbine (MRWT) has been proven advantageous over Single-Rotor Wind Turbine (SRWT) in many aspects. In order to study the performance of MRWT over SRWT, this work presents a low-cost and low-weight design for a test rig for laboratory-scale wind turbine configurations. The configurations under study are a single-rotor, and a twin-rotor of the same size with a diameter of 30 cm. Aerodynamic loads have been calculated using the Blade Element Momentum (BEM) method, then the loads were used for stress analysis over the test rig proposed. The test rig is designed on Solidworks and the aerodynamic and inertial loads were applied for static structural analysis. The analysis showed that both configurations are safe against failure and the deflections were reasonable to ensure low vibrations which may affect the turbine performance. The single-rotor configuration test-rig is about 16 gm in mass, with a 1.67 factor of safety, while the twin-rotor configuration weighs 360 gm with a factor of safety of 3.7.

Aerodynamic Performance of a 100 W Single-Rotor Wind Turbine in Comparison with Multi-Rotor Wind Turbines of the Same Capacity

Large-scale wind turbines come with great costs and logistic difficulties in transportation and installation. This work presents a solution by using Multi-Rotor Systems (MRS) wind turbines. Four different configurations of wind turbines with one, two, three, and four rotors of the same turbine capacity of 100 W have been studied. An in-house BEM code has been verified and used for the current study. The study has shown that the total mass of the rotor/nacelle assembly is 70%, 57%, and 50% for the twin-rotor, tri-rotor, and quad-rotor respectively as a percentage of the total mass of the single rotor. Torque load has also shown a significant decrease down to 50% of the quad-rotor compared to single-rotor showing the great advantage of MRS compared to single-rotor wind turbines. Based on the rotor/nacelle performance solely, increasing the number of rotors results in better performance with less mass and accordingly cost.

Aeroelastic Stability Analysis of a Quad-Rotor Wind Turbine

This paper presents the aeroelastic stability analysis of a quad-rotor wind turbine and identifies modes with low damping that are otherwise not present on a single-rotor wind turbine. The non-linear dynamics of a wind turbine model in SIMPACK, without considering wind shear and tower shadow, is linearized around a steady-state; followed by MBC transformation resulting in LTI model. Standard eigenvalue analysis of LTI model is carried out to capture the natural frequency and damping of a quad-rotor wind turbine as a function of wind speed. Results show that several modes with low damping (besides the low damping modes observed on a single-rotor wind turbines) are identified where the damping ratio is less than 1% over the entire operation range.

Unsteady aerodynamic modelling for dual-rotor wind turbines with lifting surface method and free wake model

A time-marching aerodynamic model for dual-rotor wind turbines (DRWT) is presented with the lifting surface method and free wake model. The performance of a reference DRWT by two axial connected NREL 5MW wind turbines is calculated to verify the algorithm. The output converges with remarkable oscillation. Free wakes swell under the coupling effect. The accumulated power of DRWT outranges single-rotor wind turbine (SRWT) by a limited extent under certain operating conditions. The front rotor (FR) produces the major portion of the power, especially for low inflow velocity. The unsteadiness of performance and spanwise load is further investigated, and the result shows that the power output of the rear rotor (RR) undergoes greater fluctuation than FR. The rotor-rotor induction strengthens both the rotors’ performance before they align and weakens it when they rotate away. The additional disturbance caused by FR’s tip vortices acts negatively on RR’s torque by upwashing the blade tip.

A Comparative Study of Dual Stator With Novel Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Turbine Applications

Compared with the single rotor wind turbine, a counter-rotating (CR) wind turbine with two rotor sets leads to twice power density. In this regard, dual stator CR (DSCR) permanent magnet flux switching generator (DSCR-PMFSG) is employed. However, in DSCR-PMFSG both rotor and armature parts are rotating and require slip rings for power transmission. These slip rings associate demerits of constant maintenance, poor speed regulation, increased cost, and additional slip ring losses, whereas DSCR-PMFSG offer lower flux and lesser power density. To overcome the demerits of DSCR-PMFSG as mentioned earlier, this paper proposed a novel dual rotor counter-rotating permanent magnet flux switching generator (DRCR-PMFSG) for wind turbine applications that eliminate the requirements of slip rings and retain brushless operation. The proposed DRCR-PMFSG share one stator connected back-to-back through a flux bridge that provides an alternate flux path between two mechanical ports associated with the inner rotor and outer rotor, contributing to the cumulative output. A detailed comparative analysis of DSCR-PMFSG and DRCR-PMFSG is performed under static characteristics, overload, and wide speed range to generate output power, voltage, current, power density, and efficiency. Quantitative comparative analysis under static analysis evident that proposed DRCR-PMFSG exhibits 33.29% higher flux, suppressed cogging torque and torque ripples up to 53.48% and 67.45%, respectively. Furthermore, a comprehensive quantitative analysis is performed under coupled overload and over-speed capability. Analysis exposes that in comparison with DSCRP-PMFSG, the proposed DRCR-PMFSG improves voltage regulation factor by 55.88%, output current enhanced by 67.9%, raise output voltage to 2.01 times, and power density to 1.72 times while maintaining the efficiency of 90.195% and achieving stable voltage profile with load variation. Finally, a detailed comparative analysis with conventional designs is performed and comprehensive mathematical modelling based on sub-domain model is developed accounting stator slot and rotor pole combinations, magnetic saturation, and winding configuration to validates finite element analysis (FEA) of JMAG Designer v.20.1.

Performance optimization of a dual-rotor ducted wind turbine by using response surface method

• The effect of different dual-rotor wind turbine operating conditions on ducted wind turbines was studied. • ANOVA was used to model the effect of dual rotor design factors on extracted power. • Response Surface Method applied to experimental data in order to optimize the dual rotor wind turbine performance. • Key parameters were affecting the performance of the turbine investigated by RSM. • A suitable dual rotor wind turbine for ducted wind turbines was designed, and RSM was an excellent method to optimize DWTs. The presented study evaluates and optimizes the performance of dual-rotor wind turbines installed inside a developed duct. The effect of different operating conditions on the extracted power was compared between dual-rotor wind turbines (DRWT) and single rotor wind turbines (SRWT). These operating conditions include the type of dual-rotor wind turbines installed in the throat section of the duct, the distance between the two rotors of a turbine, and the flow velocity through the duct throat that were evaluated by the multivariate statistical method response surface methodology. The central composite design of the response surface method was utilized to fit the designed model based on the least-squares method. Also, the multiple regression method was applied for the empirical data to match variable operating conditions with the developed model by analysis of variance (ANOVA). Afterward, some experiments were carried on to validate this method. The results showed a maximum power ratio of about 55% at the optimized conditions for dual rotor wind turbines. Determined P-values for designed parameters of models were less than 0.05, which makes its effect on the model significant. Furthermore, the power ratio obtained from empirical data was compatible with the considered model.

An intuitive representation and analysis of multi‐rotor wind turbine whirling modes

AbstractA multi‐rotor wind turbine (MRWT) is a concept that can reduce the size of the rotor blades compared to a single‐rotor wind turbine (SRWT). Making a cost‐optimized MRWT requires a detailed understanding of its stability properties. This paper aims to establish a physical and intuitive representation of whirling modes for three‐bladed isotropic SRWT and MRWT. An aeroelastic simulation of a nonlinear SRWT model is presented to empathize the importance of whirling. The whirling concept is introduced by simplifying the complexity of the wind turbine rotor into two models. From the models, edgewise and flapwise whirling modes are analyzed. An analytical model of a two‐rotor wind turbine is examined to present the edgewise whirling modes of MRWT. The flapwise whirling modes for MRWT are introduced by using results from edgewise whirling and findings from previous research. The MRWT whirling analysis shows whirling from multiple rotors creates reaction forces to the supporting structure when the rotors have the same speed. This results in whirling coupling modes at the same natural frequency. One is a rotor symmetric whirling mode where the rotors whirling are in phase and a rotor asymmetric mode where whirling of the rotors are out of phase. The whirling coupling effects are minimized in the case that the rotors have different speeds.