Wind Turbine Configurations Research Articles

A Numerical Study on the Effect of Wind Turbine Wake Meandering on the Power Production of Hywind Tampen

The purpose of the study is to show the importance of wake meandering effect with regard to power production, in terms of annual energy production (AEP), and velocity deficit for wind turbines affected by wake meandering. A simplified economical and environmental analysis is also presented. A replica of Equinor’s layout for Hywind Tampen wind farm, referred to as the original layout, is made and used as a basis for comparison. An alternative configuration is produced through a pragmatical optimization process, applying the SIMA-DIWA software, which reduces the effect of wake meandering on the downstream wind turbines, when the wind approaches from the most frequent direction. To show the aerodynamic effects of applying greater spacing between turbines, an enhanced version of Hywind Tampen is also presented. The main findings of the project correlate greater wake effect meandering for wind turbine configurations spread over a smaller area. The estimated annual energy production for the three configurations is 488.5 GWh for the original, 497.6 GWh for the up-scaled and 486.2 GWh for the alternative configuration, respectively. Furthermore, the optimization process revealed that a reduction in turbine distance can contribute to reduced wake effect in particular cases.

Structural analysis of an offshore vertical axis wind turbine composite blade experiencing an extreme wind load

The vertical axis wind turbine (VAWT) configuration has many advantages for an offshore wind turbine installation. The VAWT is omnidirectional and its rotating mechanical components can be placed close to sea level. In this paper, the structural analysis of a VAWT blade structure subject to a critical load case was investigated with two methods, an analytical model and a finite element (FE) model. It was shown that the utilisation of a composite blade topology can resist the induced flapwise loading and the material strains were contained within their allowable limits. The analytical approach was demonstrated to be a quick and accurate technique to compute the composite blade strain distribution when compared to the FE model results.

Joint Optimization of Wind Turbine Micrositing and Cabling in an Offshore Wind Farm

Wind farms (WFs) are important components of smart grid. The modeling and optimal planning of the WF is preliminary before its construction. In this article, a bi-level multi-objective optimization framework is presented, with the aim of simultaneously designing the configuration of wind turbines (WTs) as well as the topology of electrical collector system in an offshore WF. The installation capacity of the WF, the positioning of the WTs and the planning scheme of the electrical system are balanced to achieve a better performance of the WF. In this proposal, there is an outer layer along with two inner layers. The objectives of the outer-layer model are the maximization of the WF’s daily profit rate, the daily average capacity factor, and power quality. It is tackled by the Non-dominated Sorting Genetic Algorithm-III (NSGA-III). The objectives of the two inner layer models are to determine the topology of the electrical system and the generation schedule of other generators, and are solved by means of the Binary Particle Swarm Optimization (BPSO) algorithm and the quadratic programming (QP) method respectively. The WF is assumed to be connected to the IEEE-24 bus test system. The simulation results validate the adaptability and effectiveness of the proposed approach with the main factors that affect the WF layout being analyzed.

A Computational Fluid Dynamics Study of an Integrating Savonius-Darrieus Vertical Axis Wind Turbine

To combine the advantages of performance of both Savonius and Darrieus wind turbines, this paper aims to study computationally a novel design configuration of a Vertical Axis Wind Turbine (VAWT). The new design would help cover a broad range of performance parameters between both types of wind turbines as well as overcome drawbacks of the Savonius type at higher rotational speed. The proposed design is to integrate both of Savonius and straight blade Darrieus wind turbines in a single VAWT design configuration. In this design, the turbine rotor consists of a number of similar NACA0015 airfoil blades set in a particular arrangement. By regulating individual angles of rotor blades, the turbine would work as either Savonius or H-Darrieus VAWT. The turbine could also be set to work at different configurations between those for the Savonius and H-Darrieus ones. The computational results revealed that the performance of the proposed integrating wind turbine would be controlled and optimized to cover the operating range of both of Savonius and Darrieus wind turbines. Besides, the performance of Savonius VAWT would be modified when applying this design. When the proposed design is practically implemented, characteristics of both of Savonius and H-Darrieus based wind turbines would be found in a single design.

Tower shadow excitation of a downwind rotor blade of a turbine with a tubular tower

The downwind configuration of wind turbines offers benefits regarding the blade-tower clearance, as during operation the blade primarily bends away from the tower. Consequently, the blades can be designed with lower stiffness. For tubular towers, however, a significant deficit of the wind speed in the tower wake occurs, resulting in fatigue-inducing vibrations. For this reason, full-height lattice towers are considered the preferred support structures for wind turbines with a downwind rotor. This work estimates the tower shadow excitation of a downwind rotor blade from a tubular tower. To this end, the blade of a commercial 6 MW downwind turbine is modelled with finite-elements. The tower wake is described on the basis of Madsen’s model and for the unsteady aerodynamic interaction Küssner’s function is adopted. At below- and above-rated wind conditions, the tower wake-induced vibrations are compared with the response of a blade of an equivalent upwind rotor, considering both the tip deflections and the root moments, the latter on the basis of damage-equivalent moments, to obtain an indication of the expected difference in fatigue damage. The downwind blade experiences vibrations with considerable larger amplitudes, especially in the out-of-plane direction. From the damage-equivalent moments it can be inferred that the blades of the downwind rotor encounter a much faster accumulation of fatigue damage.

Validation Study of Multi-Rotor Systems Using Two Shrouded Wind Turbines

Multi rotor systems (MRS) have shown a great potential as a future application of wind energy. In this study, the aim is simulating the aerodynamic performance of a an MRS using fully-resolved shrouded wind turbine blades then validating with experimental data. MRS for wind turbine configurations have been studied using both numerical and experimental approaches. Different case studies have been studied and the power output comparison have been reported. The wind lens turbine (WLT) obviously shows a large increase in power output compared to the bare rotor case. Besides, the twin side-by-side (SBS) WLTs shows even larger power increase compared to the case of single WLT by around 20% for computational fluid dynamics (CFD) calculations at the optimum tip speed ratio s/D of around 0.2. The increase in power coefficient in close proximity can be explained by flow interference and gap flow behaviors. Previously, we used simplified models for blade modeling like actuator line method (ALM) and actuator disk method (ADM). However, currently we are improving the accuracy using CFD with full-scale blades with higher grid resolutions. As the number of units for an MRS is increased, the increase in power output becomes larger and larger. This is because that the gap flows between brimmed diffuser-augmented wind turbines (B-DAWT) in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, an MRS with more B-DAWTs can draw more wind into turbines showing higher power output.

A comparative study of wake interactions between wind-aligned and yawed wind turbines using LES and actuator line models

An LES based OpenFOAM solver is coupled with the actuator line model for the simulation of wind farms and the prediction of power production. The tool developed is validated for wind aligned and yawed tandem wind turbines. Two NREL 5MW turbines in a tandem configuration are considered. The solution parameters are first studied in detail. The development of vortical wakes behind the upstream and the downstream turbines are simulated under uniform and atmospheric boundary layer inflow conditions, and the power productions of the turbines are predicted. The impact of a yawed upstream rotor on its wake deflection and the resulting power production of the tandem configuration are assessed. It is shown that the coupled solver developed is quite successful in capturing the wake deficits and wake deflections, and predicting the power production of tandem wind turbine configurations.

Life cycle greenhouse gas emission from wind farms in reference to turbine sizes and capacity factors

This study analyzes the global warming potential (GWP) of wind power plants within an LCA framework. Therefore, secondary data from studies on wind turbines, which were published in the past 20 years were assessed. The data was categorized into three configurations, i.e. onshore single turbines, onshore wind farms and offshore wind farms. Within a multivariate analysis, featuring a linear regression model approach, the datasets retrieved from the literature were evaluated. The effect variable was the specific GWP, normalized to the function unit gCO2-equ/kWh electricity. Cause variables were (i) the capacity factor, (ii) the rated power and (iii) the annual energy yield (AEY), (iv) the hub height and (v) the rotor diameter. In a secondary part this study showed the quantity of uncertainty, which is present in LCA studies on wind turbines by evaluating generic wind turbine configurations, which were present in the ecoinvent database. Conclusively, a sensitivity analysis on the influence of the capacity factor on the GWP was conducted.For onshore single turbines and wind farms a negative correlation was observed between the turbine size and the GWP. A highly significant negative correlation was found between the AEY and the GWP. However, the AEY needed to be log-transformed first. Other cause variables were either collinear to the AEY or showed a weak correlation. For offshore wind turbines similar results could not be presented and none of the cause variable could explain the effect variable. The sample size was however low, as only few studies were conducted for offshore plants.The uncertainty analysis showed that generally low uncertainties are present during the modelling phase of the LCA of wind turbines, which suggests that the processes are well understood and documented. The sensitivity analysis on the capacity factor resulted in a non-linear, hyperbolic progression with respect to the GWP.

Multi-criteria PSO-based optimal design of grid-connected hybrid renewable energy systems

ABSTRACT Human-induced climate change through the over liberation of greenhouse gases, resulting in devastating consequences to the environment, is a concern of considerable global significance which has fuelled the diversification to alternative renewable energy sources. The unpredictable nature of renewable resources is an impediment to developing renewable projects. More reliable, effective, and economically feasible renewable energy systems can be established by consolidating various renewable energy sources such as wind and solar into a hybrid system using batteries or back-up units like conventional energy generators or grids. The precise design of these systems is a critical step toward their effective deployment. An optimal sizing strategy was developed based on a heuristic particle swarm optimization (PSO) technique to determine the optimum number and configuration of PV panels, wind turbines, and battery units by minimizing the total system life-cycle cost while maximizing the reliability of the hybrid renewable energy system (HRES) in matching the electricity supply and demand. In addition, by constraining the amount of conventional electricity purchased from the grid, environmental concerns were also considered in the presented method. Various systems with different reliabilities and potential of reducing consumer’s CO2 emissions were designed and the behavior of the proposed method was comprehensively investigated. An HRES may reduce the annualized cost of energy and carbon footprint significantly.

Performance Analysis of PMSG based Wind Energy Conversion System with Different LVRT Enhancement Methods

Background: Wind energy generation has emerged as the fastest growing renewable energy technology in recent years. Among different wind turbine configurations, Permanent Magnet Synchronous Generator (PMSG) based wind turbines are becoming popular due to several advantageous features associated with this. Introduction: In the events of grid fault, active power delivery to the grid is required to be stopped or reduced as per the grid code specification and due to this mismatch between power generation and power delivery results in a rise in DC link voltage and high stress on converter switches. Modern grid codes suggest Wind Power Plants (WPPs) to remain in operation and such requirements are termed as Fault Ride-Through (FRT) or Low Voltage Ride-Through (LVRT). Method: Several LVRT enhance method have been proposed in the literature in the past having distinct pros and cons. Some of them employ external means and some suggest modification of existing control in order to meet LVRT requirement specified by the grid code. Methods based on external devices may be simple and effective but in some cases, they are not cost effective. Literature suggests the use of a modified controller based method for meeting LVRT requirement economically. Results: This paper presents a review of different LVRT enhancement methods for PMSG based Wind Energy Conversion Systems (WECSs). In order to compare the performance outcomes of LVRT enhancement methods, several simulations are performed for an example WECS based on 2MW PMSG on MATLAB/Simulink platform. Conclusion: Based on the analysis of simulation results, Modified controller based methods and FACT devices are found cost-effective solutions for LVRT enhancement.

Investigation Effects of Different Wind Turbine Designs on Air Flow and Generated Power

This paper describes a study of different designs for the wind turbine. The basic wind turbine configuration with a second smaller rotor mounted in the front of the main rotor to extract as much force as possible from the flow. The wind turbine used in all the simulations was an upwind turbine with a 3 MW horizontal axis. The behaviors of pressures, velocities, and power generated were simulated and discussed. Three different configurations have been designed and simulated in SolidWorks at four different wind velocities ranging from 10 to 40 mph with an increment of 10 mph. The results revealed that the power generated by the rotor of the dual turbine to the rotor of the conventional turbine, the power created by the conventional turbine’s rotor is higher even though the size is the same. Furthermore, adding a diffuser equipped with a plat-type circular frame achieved the best performance. Finally, some numbers and figures are highlighted, and a conclusion is stated to summarize the results.

Extremum‐seeking control for energy‐harvesting enhancement of wind turbines with hydromechanical drivetrains

AbstractEfficiency and reliability enhancement of distributed wind energy systems have been the subject of extensive research effort for the purpose of energy cost reduction and power availability. This work investigates the integration of a hydromechanical power split transmission into the drivetrain of a stall‐regulated wind turbine with a fixed‐speed generator to enhance the overall system efficiency without compromising its reliability. The proposed drivetrain configuration introduces a variable transmission ratio capability, thus enabling the turbine rotor to cope with varying wind speeds independent of the fixed generator speed. An extremum‐seeking control approach is adopted to maximize energy harvesting by controlling a variable geometric volume hydraulic pump without the need for wind speed measurement. Compared with a stall‐regulated fixed‐speed wind turbine, the performance of the proposed wind turbine configuration is evaluated in simulation environment under different wind speed conditions. The results demonstrate the ability of the proposed wind turbine configuration to significantly improve the system overall efficiency in partial and full‐load regions of operation. Consequently, the proposed wind turbine configuration with extremum‐seeking control can be considered as an efficient and reliable possible alternative for future distributed and isolated wind energy systems.

Dataset on the measurement of power in the hybrid vertical axis wind turbine in natural wind.

The testing and performance data of the hybrid vertical axis wind turbines with magnetic levitation analyzed for low rated wind speeds is presented here. All the data are obtained by carrying out the investigations under natural wind conditions at Wind Turbine Research Station (WTRS), Kayathar, Tamilnadu, India. Four different wind turbine configurations namely helical Savonius - simple Savonius hybrid in two stage, helical Savonius - helical Bach hybrid in two stage, helical Bach – simple Bach hybrid in two stage, and single stage helical Bach. All the raw data obtained are processed and presented to compare the parameters among the different vertical axis wind turbine configurations.

Computational analysis of Savonius wind turbine modifications including novel scooplet-based design attained via smart numerical optimization

Simple design and low power coefficient of Savonius-style wind turbines make them attractive in experimental and computational fluid dynamics (CFD) based optimization studies. Still, after numerous studies the power coefficient is low, and the single optimal Savonius-style wind turbine shape and configuration is not known. This leaves room for improving the power coefficient, and the objective of this paper is to find an improved solution with application of smart numerical optimization.Several Savonius blade improvements proposed by other researchers were initially analyzed. The numerical (3D CFD) analysis has shown that simple modifications of the blades can be better than more complicated shapes such as spline or elliptical curve. This has encouraged the investigation on what is the limit to the optimized design which used only simple circular-arc based blades. Thus, we perform a global optimization of Savonius blade pair where each pair is composed of two circular arc segments. The smart numerical optimization was performed using 2D CFD and the results were verified and compared with the previous designs using the 3D CFD. The selected optimization operating conditions were tip speed ratio 0.9 and wind speed 12 m/s. The novel optimized design achieved 39% improvement of the maximum power coefficient relative to the classical Savonius design.

Performance enhancement of twisted-bladed Savonius vertical axis wind turbines

It is important to determine the most optimal configuration of a Savonius vertical axis wind turbine that attains the best performance with a high self-starting ability. Thus, the effects of several design parameters including twist angle, overlap ratio, and endplates size ratio, along with the wind velocity on the performance of the Savonius wind turbine are investigated. Novel assessment methods based on flow field characteristics such as streamlines and pressure fields around the Savonius wind turbine are carried out. This is the first contribution to understand how geometrical variables influence the aerodynamic performance of the twisted Savonius rotor. Moreover, the variation of torque, power, thrust, and static torque coefficients are estimated. Thus, a three-dimensional, incompressible unsteady Reynolds-averaged Navier-Stokes model in conjunction with k-ω shear-stress transport turbulence model is developed. The model is numerically simulated and validated using the experimental and numerical data available in literature. Results indicate that the Savonius rotor with a twist angle of 45°, an overlapping ratio of zero, and endplates size ratio of 1.1 attains the highest net output power compared to other designs. It is found that at a wind velocity of 6 m/s, the Savonius rotor achieves a maximum power coefficient of 0.223, and with further increase of the wind velocity to 10 m/s, the power coefficient reaches 0.231. In addition, the current developed design has a positive static torque coefficient at all rotor angles, and consequently, it achieves a high self-starting ability. However, for the conventional (untwisted) design, the maximum attainable power coefficient was found to be 0.174 at an overlapping ratio of 0.15, and equal endplate size ratio. In addition, negative values of the static torque coefficient were observed at a specific range of rotor angles that prevent the self-starting ability. Accordingly, the new twisted rotor design not only enhances the power coefficient but the self-starting ability as well. The findings of the current results provide another direction for researchers and designers to utilize the twisted Savonius wind turbine.

Effect of tip spacing, thrust coefficient and turbine spacing in multi-rotor wind turbines and farms

Abstract. Large eddy simulations (LESs) are performed to study the wakes of a multi-rotor wind turbine configuration comprising four identical rotors mounted on a single tower. The multi-rotor turbine wakes are compared to the wake of a conventional turbine comprising a single rotor per tower with the same frontal area, hub height and thrust coefficient. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The differences with the wake of a conventional turbine increase as the spacing between the tips of the rotors in the multi-rotor configuration increases. The differences are also sensitive to the thrust coefficients used for all rotors, with more pronounced differences for larger thrust coefficients. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and with the wind direction. Similar to the isolated turbine results, multi-rotor wind farms show smaller wake losses and smaller turbulence intensity compared to wind farms comprised of conventional single-rotor turbines. The benefits of multi-rotor wind farms over single-rotor wind farms increase with increasing tip spacing, irrespective of the axial spacing and thrust coefficient. The mean velocity profiles and relative powers of turbines obtained from the LES results are predicted reasonably accurately by an analytical model assuming Gaussian radial profiles of the velocity deficits and a hybrid linear-quadratic model for the merging of wakes. These results show that a larger power density can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines.

Three-dimensional Numerical Study of the Performance of a Small Combined Savonius-Darrieus Vertical Wind Turbine

Energy crisis and global warming have encouraged the use of renewable energy resources such as wind power. Among different types of wind turbines, vertical axis wind turbines can be easily installed in residential areas. In this study, a computational fluid dynamics analysis was performed to predict the performance characteristics of three configurations of small vertical axis wind turbines. For this purpose, an shear stress transport k-omega turbulent model and a rotating frame of reference were employed. Initially, a Savonius and a Darrieus wind turbine were simulated; the low power coefficient of the Savonius wind turbine and the poor performance of the Darrieus wind turbine in low tip speed ratios were the main disadvantages of these systems. Finally, a combined Savonius-Darrieus wind turbine was proposed to deal with these drawbacks. The power coefficient of this combined wind turbines was nearly as high as the Darrieus wind turbine (0.3), while the Savonius blades recover the low torque obtained at low tip speed ratios and help produce more consistent torque, making it suitable for residential applications.

Optimal Configuration and Diversification of Wind Turbines: A Hybrid Approach to Improve the Penetration of Wind Power

Literature indicates a decline in the market value of wind power with increasing market penetration. Two promising measures to mitigate this market value drop are system-friendly turbines and geographical diversification. This study analyzes the combined potential of a hybrid approach used to simultaneously improve market values, reduce system costs and the overall subsidy needs in Germany. Therefore, promising diversification regions and site optimal turbine configurations are identified. The corresponding market values and levelized cost of electricity are forecasted for penetration rates of up to 65% (2030). The analysis shows that the market value drop in diversified regions using system-friendly turbines is less severe. Furthermore, the hybrid approach results in system cost and subsidy savings. Additional analyses show that the dominant share of the hybrid approach benefits can be attributed to the use of system-friendly turbines and that diversification does not seem to be a promising alternative for Germany.

Review of feasibility wind turbine technologies for highways energy harvesting

Wind energy is one of the non-conventional forms of energy and it is available in affluence. It is also claimed that the wind power is pollution-free, replacement of fossil fuel and that its source of energy is freely available. Electricity can be generated with the help of a wind turbine generator. In this paper, a comprehensive study on contemporary portable wind energy harvesters has been conducted. The different existing performance such as reliability evaluation models, various problems related to structure wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed. At the same time, experimental analysis is focused on behaviour, especially characteristics of impact wind energy, performance as lots of advanced research work has already been done or going on the harnessing of natural wind energy. In this review paper, a different model wind turbine has been studied from previous testing purpose presented. This review aim of utilizing this wind energy in a most effective manner to get the maximum electric output, and therefore the government can think over implementing the suitable type of wind turbine configuration selected highway at low cost as our installation site taking the advantage of the moving vehicles on both sides of the road.

Performance investigation of a new Darrieus Vertical Axis Wind Turbine

In present work, a new configuration of Darrieus type Vertical Axis Wind Turbine (VAWT) is introduced, and its aerodynamic performance is examined using three-dimensional numerical simulation by the solution of Reynolds averaged Naiver-Stokes equations. In comparison to each other, straight-blade VAWTs have higher average output torque and are simpler to manufacture while helical-blade VAWTs deliver non-oscillatory and smoother torque. To include advantages of both types of Darrieus VAWTs, a new straight-blade turbine is proposed which in general performs better than helical-blade VAWT. This turbine, called three-part-blade or simply 3-PB VAWT, includes straight blades where each of them is vertically cut into three parts. The objective of this paper is to show that while the proposed turbine is simple to manufacture, its performance is better than that of helical-blade VAWT. Present simulation is validated using experimental data. Having compared performance of the proposed turbine with a helical-blade VAWT, it is shown that 3-PB VAWT produces 6.06% higher average of total torque coefficient at low Tip Speed Ratio (TSR) of 0.44, and 158.19% at high TSR of 1.77. Based on these results, it is strongly recommended to use 3-PB VAWT considering its better aerodynamic performance and low cost of production.