Power Augmentation of Shrouded Wind Turbines in a Multirotor System

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Yuji Ohya ◽  
Jumpei Miyazaki ◽  
Uli Göltenbott ◽  
Koichi Watanabe
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Bluff Body ◽  
Flow Direction ◽  
Total Power ◽  
Significant Saving ◽  
Vortex Interactions ◽  
Wind Turbine System ◽  
Flow Phenomena ◽  
Circular Disks

Diffuser-augmented wind turbines (DAWTs) can significantly increase the performance of the rotor. Multirotor systems (MRSs) have a lot of merits such as significant saving mass and overall cost of the wind turbine system. A MRS is defined as containing more than one rotor in a single structure. In the present research, DAWTs are studied in a MRS. In wind tunnel experiments, the power output and aerodynamics of two and three DAWTs placed in close vicinity, in side-by-side arrangements, have been investigated, along with circular disks and conventional wind turbines in the same configurations as the MRS. Results show a significant increase of up to 12% in total power output of the MRS with DAWTs compared to the sum of the stand-alone same turbines. The results can be explained by observing the bluff body flow phenomena in the wake interference around the multiple circular disks. Those flow phenomena are due to the accelerated gap flows and those biasing in the flow direction caused by the vortex interactions in the gap.

scholarly journals Multirotor Systems Using Three Shrouded Wind Turbines for Power Output Increase

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Koichi Watanabe ◽  
Yuji Ohya
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Total Power ◽  
Vortex Interaction ◽  
Wind Tunnel Experiments ◽  
Significant Saving ◽  
Wind Turbine System ◽  
Output Increase ◽  
Lowered Pressure ◽  
Total Power Output

Brimmed-diffuser augmented wind turbines (B-DAWTs) can significantly increase the performance of the rotor. Multirotor systems (MRSs) have a lot of merits such as significant saving mass and overall cost of the wind turbine system. In the present research, B-DAWTs are studied in a MRS. In wind tunnel experiments, the power output and aerodynamics of three B-DAWTs placed in close vicinity have been investigated. The results show a significant increase of up to 12% in total power output of the MRS with B-DAWTs compared to the sum of the stand-alone (SA) same turbines. The accelerated gap flows between B-DAWTs in a MRS cause lowered pressure regions due to vortex interaction behind the brimmed diffusers and draw more wind into turbines.

scholarly journals A New Approach Toward Power Output Enhancement Using Multirotor Systems With Shrouded Wind Turbines

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Ohya Yuji ◽  
Watanabe Koichi
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Vertical Plane ◽  
Total Power ◽  
Plane Normal ◽  
Output Performance ◽  
Wind Turbine System ◽  
Lowered Pressure ◽  
Single Structure

A multirotor system (MRS) is defined as containing more than one rotor in a single structure. MRSs have a great potential as a wind turbine system, saving mass and cost, and showing scale ability. The shrouded wind turbine with brimmed diffuser-augmented wind turbines (B-DAWT) has demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 2–5 compared with a bare wind turbine. In the present research, B-DAWTs are used in a multirotor system. The power output performance of MRSs using two and three B-DAWTs in a variety of configurations has been investigated in the previous works. In the present study, the aerodynamics of an MRS with five B-DAWTs, spaced in close vicinity in the same vertical plane normal to a uniform flow, has been analyzed. Power output increases of up to 21% in average for a five-rotor MRS configuration are achieved in comparison to that for the stand-alone configuration. Thus, when B-DAWTs are employed as the unit of a MRS, the total power output is remarkably increased. As the number of units for an MRS is increased from two to five, the increase in power output becomes larger and larger. This is because that the gap flows between B-DAWTs in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, a MRS with more B-DAWTs can draw more wind into turbines showing higher power output.

scholarly journals Brief Communication: On the influence of vertical velocity profiles on the combined power output of two model wind turbines in yaw

2017 ◽  
Author(s):  
Jannik Schottler ◽  
Agnieszka Hölling ◽  
Joachim Peinke ◽  
Michael Hölling
Keyword(s):  
Wind Turbines ◽  
Vertical Velocity ◽  
Velocity Gradient ◽  
Power Output ◽  
Velocity Profiles ◽  
Total Power ◽  
Misalignment Angle ◽  
Velocity Gradients ◽  
Total Power Output ◽  
Vertical Velocity Gradient

Abstract. The effect of vertical velocity gradients on the total power output of two aligned model wind turbines as a function of yaw misalignment of the upstream turbine is studied experimentally. It is shown that asymmetries of the power output of the downstream turbine and the combined power of both with respect to the upstream turbine's yaw misalignment angle can be linked to the vertical velocity gradient of the inflow.

scholarly journals Brief communication: On the influence of vertical wind shear on the combined power output of two model wind turbines in yaw

2017 ◽  
Vol 2 (2) ◽  
pp. 439-442 ◽  
Author(s):  
Jannik Schottler ◽  
Agnieszka Hölling ◽  
Joachim Peinke ◽  
Michael Hölling
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Total Power ◽  
Misalignment Angle ◽  
Total Power Output

Abstract. The effect of vertical wind shear on the total power output of two aligned model wind turbines as a function of yaw misalignment of the upstream turbine is studied experimentally. It is shown that asymmetries of the power output of the downstream turbine and the combined power of both with respect to the upstream turbine's yaw misalignment angle can be linked to the vertical wind shear of the inflow.

scholarly journals Improving the Strategy of Maintaining Offshore Wind Turbines through Petri Net Modelling

2021 ◽  
Vol 11 (2) ◽  
pp. 574
Author(s):  
Rundong Yan ◽  
Sarah Dunnett
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Petri Net ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Maintenance Costs ◽  
Offshore Wind Turbines ◽  
Major Repair ◽  
Wind Turbine System ◽  
Periodic Maintenance

In order to improve the operation and maintenance (O&M) of offshore wind turbines, a new Petri net (PN)-based offshore wind turbine maintenance model is developed in this paper to simulate the O&M activities in an offshore wind farm. With the aid of the PN model developed, three new potential wind turbine maintenance strategies are studied. They are (1) carrying out periodic maintenance of the wind turbine components at different frequencies according to their specific reliability features; (2) conducting a full inspection of the entire wind turbine system following a major repair; and (3) equipping the wind turbine with a condition monitoring system (CMS) that has powerful fault detection capability. From the research results, it is found that periodic maintenance is essential, but in order to ensure that the turbine is operated economically, this maintenance needs to be carried out at an optimal frequency. Conducting a full inspection of the entire wind turbine system following a major repair enables efficient utilisation of the maintenance resources. If periodic maintenance is performed infrequently, this measure leads to less unexpected shutdowns, lower downtime, and lower maintenance costs. It has been shown that to install the wind turbine with a CMS is helpful to relieve the burden of periodic maintenance. Moreover, the higher the quality of the CMS, the more the downtime and maintenance costs can be reduced. However, the cost of the CMS needs to be considered, as a high cost may make the operation of the offshore wind turbine uneconomical.

Influence of the Blade-Spoke Connection Point on the Aerodynamic Performance of Darrieus Wind Turbines

2016 ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari
Keyword(s):  
Wind Turbines ◽  
Design Parameter ◽  
Flow Direction ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Common Solution ◽  
Curvature Effects ◽  
Flow Curvature ◽  
Low Incidence

The assessment of robust CFD techniques is casting new light on the aerodynamics of airfoils rotating around an axis orthogonal to flow direction, with particular reference to flow curvature effects and stall mechanisms. In particular, Darrieus wind turbines’ designers are taking profit from these new discovers to improve the aerodynamic design of the rotors, in view of an increase of the overall efficiency and a reduction of the structural stresses on the blades. A controversial design parameter for Darrieus turbines, especially in case of small-size rotors, is represented by the location of the blade-spoke connection along the chord. The most common solution is indeed to place the connection at approximately airfoil’s quarter chord, i.e. where the pressure center is commonly located for low incidence angles. In some cases, however, the blade is connected at middle chord due to symmetry or aesthetic reasons. In some small turbines, innovative designs have even disregarded this parameter. Even if one can argue that the blade connection point is about to have some aerodynamic effects on the turbine’s performance, the real impact of this important design parameter is often not fully understood. The present study makes use of extensive CFD simulations on a literature case study, using a NACA 0021 airfoil, to assess the influence of the blade-spoke connection point. In particular, the differences in terms of power coefficient curve of the turbine, optimal tip-speed ratio, torque profiles and stresses on the connection are analyzed and discussed. Detailed flow analyses are also shown for azimuthal positions of particular interest. Results on the selected case study showed that the middle-chord blade-spoke connection point seems to guarantee a higher performance of the rotor, even if additional solicitation is applied to the connection itself. It is further shown that the same performance can indeed be obtained with the airfoil attached at quarter chord and properly pitched. By doing so, the stresses are contained and the performance is maximized.

scholarly journals Experimental and simulation-based analysis of asymmetrical spherical roller bearings as main bearings for wind turbines

2021 ◽  
Author(s):  
Amin Loriemi ◽  
Georg Jacobs ◽  
Sebastian Reisch ◽  
Dennis Bosse ◽  
Tim Schröder
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Measurement Data ◽  
Contact Angles ◽  
Suspension System ◽  
Roller Bearings ◽  
Axial Forces ◽  
Wind Turbine System ◽  
Bearing Life ◽  
The Individual

AbstractSymmetrical spherical roller bearings (SSRB) used as main bearings for wind turbines are known for their high load carrying capacity. Nevertheless, even designed after state-of-the-art guidelines premature failures of this bearing type occur. One promising solution to overcome this problem are asymmetrical spherical roller bearings (ASRB). Using ASRB the contact angles of the two bearing rows can be adjusted individually to the load situation occurring during operation. In this study the differences between symmetrical and asymmetrical spherical roller bearings are analyzed using the finite element method (FEM). Therefore, FEM models for a three point suspension system of a wind turbine including both bearings types are developed. These FEM models are validated with measurement data gained at a full-size wind turbine system test bench. Taking into account the design loads of the investigated wind turbine it is shown that the use of an ASRB leads to a more uniform load distribution on the individual bearing rows. Considering fatigue-induced damage an increase of the bearing life by 62% can be achieved. Regarding interactions with other components of the rotor suspension system it can be stated that the transfer of axial forces into the gearbox is decreased significantly.

scholarly journals Performance Enhancement of Proposed Namaacha Wind Farm by Minimising Losses Due to the Wake Effect: A Mozambican Case Study

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4291
Author(s):  
Paxis Marques João Roque ◽  
Shyama Pada Chowdhury ◽  
Zhongjie Huan
Keyword(s):  
Wind Speed ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Output ◽  
Wind Farm ◽  
Wind Farms ◽  
Operating Conditions ◽  
Wake Effect ◽  
Wind Generators ◽  
Wind Potential

District of Namaacha in Maputo Province of Mozambique presents a high wind potential, with an average wind speed of around 7.5 m/s and huge open fields that are favourable to the installation of wind farms. However, in order to make better use of the wind potential, it is necessary to evaluate the operating conditions of the turbines and guide the independent power producers (IPPs) on how to efficiently use wind power. The investigation of the wind farm operating conditions is justified by the fact that the implementation of wind power systems is quite expensive, and therefore, it is imperative to find alternatives to reduce power losses and improve energy production. Taking into account the power needs in Mozambique, this project applied hybrid optimisation of multiple energy resources (HOMER) to size the capacity of the wind farm and the number of turbines that guarantee an adequate supply of power. Moreover, considering the topographic conditions of the site and the operational parameters of the turbines, the system advisor model (SAM) was applied to evaluate the performance of the Vestas V82-1.65 horizontal axis turbines and the system’s power output as a result of the wake effect. For any wind farm, it is evident that wind turbines’ wake effects significantly reduce the performance of wind farms. The paper seeks to design and examine the proper layout for practical placements of wind generators. Firstly, a survey on the Namaacha’s electricity demand was carried out in order to obtain the district’s daily load profile required to size the wind farm’s capacity. Secondly, with the previous knowledge that the operation of wind farms is affected by wake losses, different wake effect models applied by SAM were examined and the Eddy–Viscosity model was selected to perform the analysis. Three distinct layouts result from SAM optimisation, and the best one is recommended for wind turbines installation for maximising wind to energy generation. Although it is understood that the wake effect occurs on any wind farm, it is observed that wake losses can be minimised through the proper design of the wind generators’ placement layout. Therefore, any wind farm project should, from its layout, examine the optimal wind farm arrangement, which will depend on the wind speed, wind direction, turbine hub height, and other topographical characteristics of the area. In that context, considering the topographic and climate features of Mozambique, the study brings novelty in the way wind farms should be placed in the district and wake losses minimised. The study is based on a real assumption that the project can be implemented in the district, and thus, considering the wind farm’s capacity, the district’s energy needs could be met. The optimal transversal and longitudinal distances between turbines recommended are 8Do and 10Do, respectively, arranged according to layout 1, with wake losses of about 1.7%, land utilisation of about 6.46 Km2, and power output estimated at 71.844 GWh per year.

Experimental Analysis of a NACA 0021 Airfoil Under Dynamic Angle of Attack Variation and Low Reynolds Numbers

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
D. Holst ◽  
B. Church ◽  
F. Wegner ◽  
G. Pechlivanoglou ◽  
C. N. Nayeri ◽  
...  
Keyword(s):  
Design Process ◽  
Surface Pressure ◽  
Wind Turbines ◽  
Full Range ◽  
Vertical Axis ◽  
Reynolds Numbers ◽  
Time Resolved ◽  
Pressure Distributions ◽  
Pressure Development ◽  
Flow Phenomena

The wind industry needs reliable and accurate airfoil polars to properly predict wind turbine performance, especially during the initial design phase. Medium- and low-fidelity simulations directly depend on the accuracy of the airfoil data and even more so if, e.g., dynamic effects are modeled. This becomes crucial if the blades of a turbine operate under stalled conditions for a significant part of the turbine's lifetime. In addition, the design process of vertical axis wind turbines needs data across the full range of angles of attack between 0 and 180 deg. Lift, drag, and surface pressure distributions of a NACA 0021 airfoil equipped with surface pressure taps were investigated based on time-resolved pressure measurements. The present study discusses full range static polars and several dynamic sinusoidal pitching configurations covering two Reynolds numbers Re = 140k and 180k, and different incidence ranges: near stall, poststall, and deep stall. Various bistable flow phenomena are discussed based on high frequency measurements revealing large lift-fluctuations in the post and deep stall regime that exceed the maximum lift of the static polars and are not captured by averaged measurements. Detailed surface pressure distributions are discussed to provide further insight into the flow conditions and pressure development during dynamic motion. The experimental data provided within the present paper are dedicated to the scientific community for calibration and reference purposes, which in the future may lead to higher accuracy in performance predictions during the design process of wind turbines.

Effect of Tube Diameter on Flow Phenomena of Gas-Liquid Two-Phase Flow in Microchannels

2015 ◽  
Author(s):  
Hideo Ide ◽  
Eiji Kinoshita ◽  
Ryo Kuroshima ◽  
Takeshi Ohtaka ◽  
Yuichi Shibata ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Water Solution ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Tube Diameter ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Flow Phenomena ◽  
The Waves

Gas-liquid two-phase flows in minichannels and microchannels display a unique flow pattern called ring film flow, in which stable waves of relatively large amplitudes appear at seemingly regular intervals and propagate in the flow direction. In the present work, the velocity characteristics of gas slugs, ring films, and their features such as the gas slug length, flow phenomena and frictional pressure drop for nitrogen-distilled water and nitrogen-30 wt% ethanol water solution have been investigated experimentally. Four kinds of circular microchannels with diameters of 100 μm, 150 μm, 250 μm and 518 μm were used. The effects of tube diameter and physical properties, especially the surface tension and liquid viscosity, on the flow patterns, gas slug length and the two-phase frictional pressure drop have been investigated by using a high speed camera at 6,000 frames per second. The flow characteristics of gas slugs, liquid slugs and the waves of ring film are presented in this paper.

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