scholarly journals Comparing the Effect of Rotor Tilt Angle on Performance of Floating Offshore and Fixed Tower Wind Turbines

2019 ◽  
Vol 12 (5) ◽  
pp. 84
Author(s):  
Wongsakorn Wisatesajja ◽  
Wirachai Roynarin ◽  
Decha Intholo
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Tilt Angle ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Offshore Wind ◽  
Floating Platform ◽  
Optimal Position ◽  
Wind Speeds ◽  
Floating Offshore Wind Turbines

The development of Floating Offshore Wind Turbines (FOWTs) aims to improve the potential performance of the wind turbine. However, a problem arises due to the angle of tilt from the wind flow and the floating platform, which leads to a vertical misalignment of the turbine axis, thereby reducing the available blade area and lowering the capacity to capture energy. To address this problem, this paper seeks to compare the influence of the rotor tilt angle on wind turbine performance between fixed tower wind turbines and FOWTs. The models used in the experiments have R1235 airfoil blades of diameter 84 cm. The experiment was analyzed using a wind tunnel and mathematical modelling techniques. Measurements were obtained using an angle meter, anemometer and tachometer. Testing involved wind speeds ranging from 2 m/s to 5.5 m/s, and the rotational speeds of the two turbine designs were compared. The study found that the rotational speeds of the FOWTs were lower than those of the fixed tower turbines. Moreover, at tilt angles from 3.5° – 6.1° there was a loss in performance which varied between 22% and 32% at different wind speeds. The tilt angle had a significant effect upon FOWTs due to the angle of attack was continuously changing, thus altering the optimal position of the turbine blades. This changing angle of attack caused the effective area of the rotor blade to change, leading to a reduction in power output at suboptimal angles. The study finally makes recommendations for future studies.

Design and Evaluation of a Rooftop Wind Turbine Rotor With Untwisted Blades

2013 ◽  
Author(s):  
Sayem Zafar ◽  
Mohamed Gadalla
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Low Cost ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Wind Speeds ◽  
Small Wind Turbines ◽  
Wind Turbine Rotor

A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.

Fully Coupled Aero-Hydro-Structural Simulation of New Floating Wind Turbine Concept

2018 ◽  
Author(s):  
Aengus Connolly ◽  
Marc Guyot ◽  
Marc Le Boulluec ◽  
Léna Héry ◽  
Aonghus O’Connor
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Structural Model ◽  
Capital Expenditure ◽  
Offshore Wind ◽  
Floating Platform ◽  
Simulation Methodology ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Fully Coupled

This paper describes a fully coupled numerical simulation methodology which is tailored towards floating offshore wind turbines. The technique assembles three key components; an aerodynamic model of the applied wind loads based on blade element momentum theory, a structural model of the floating platform and its associated mooring lines based on the nonlinear finite element method, and a hydrodynamic model of the wave-induced forces based on potential flow theory. The simulation methodology has been implemented in a commercial software product called ‘Flexcom Wind’, and the technical validation involves comparisons with experimental data derived from model-scale tank test facilities. The validation process centres on an innovative floating wind turbine concept developed by Eolink. Unlike most wind turbines in industry which are supported by a single mast, this patented design uses four separate pillars to connect the turbine structure to the corners of the floating platform. This unique configuration offers several advantages over conventional designs, including a more even stress distribution in structural members, reduced dynamic vibration, smaller floater size and lower overall capital expenditure. Data obtained from the numerical simulations combined with the empirical tests is helping to optimise the device, with a view to further improving its structural design and performance.

scholarly journals A 6-DOFs Hardware-in-the-Loop System for Wind Tunnel Tests of Floating Offshore Wind Turbines

2019 ◽  
Author(s):  
Alessandro Fontanella ◽  
Ilmas Bayati ◽  
Federico Taruffi ◽  
Francesco La Mura ◽  
Alan Facchinetti ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Scale Model ◽  
Hardware In The Loop ◽  
Floating Platform ◽  
Wind Tunnel Tests ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Abstract This article presents a hardware-in-the-loop (HIL) methodology developed at Politecnico di Milano (PoliMi) to perform wind tunnel tests on floating offshore wind turbines (FOWTs). The 6-DOFs HIL setup is presented, focusing on the main differences with respect to a previous 2-DOFs system. Aerodynamic, rotor and control related loads, physically reproduced by the wind turbine scale model, must be measured in real-time and integrated with the platform numerical model. These forces contribute to couple wind turbine and floating platform dynamics and their correct reproduction is of fundamental importance for the correct simulation of the floating system behavior. The procedure developed to extract rotor loads from the available measurements is presented, discussing its limitations and the possible uncertainties introduced in the results. Results from verification tests in no-wind conditions are presented and analyzed to identify the main uncertainty sources and quantify their effect on the reproduction of the floating wind turbine response to combined wind and waves.

Fully-Coupled Aero-Hydrodynamic Simulation of Floating Offshore Wind Turbines by Different Simulation Methods

2018 ◽  
Author(s):  
Ping Cheng ◽  
Decheng Wan
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Hydrodynamic Simulation ◽  
Floating Offshore Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Fully Coupled

To accurately predict the critical loads due to wind and wave is one of the common challenges in designing a floating offshore wind turbine (FOWT). The fully-coupled aero-hydrodynamic simulation of a floating offshore wind turbine, the NREL-5MW baseline wind turbine mounted on a semi-submersible floating platform, is conducted with two methods. Firstly, the in-house code naoe-FOAM-os-SJTU, which is developed on the open source platform OpenFOAM and coupled with the overset grid technique, is employed for the directly CFD computations. And another in-house code FOWT-UALM-SJTU developed by coupling the unsteady actuator line model (UALM) with naoe-FOAM-SJTU is also utilized for coupling simulations. In both models, the three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are solved with the turbulence model k-ω SST, and the Pressure-Implicit with Splitting of Operations (PISO) algorithm is applied to solve the pressure-velocity coupling equations. Both two solvers provide reasonable results of main aerodynamic loads as well as the main hydrodynamic forces. The FOWT-UALM-SJTU solver achieves better computational efficiency by simplifying the blade structure as actuator line models, while the naoe-FOAM-os-SJTU solver provides more accurate detailed flow information near the turbine blades.

scholarly journals Analysis of Influence of Tilt Angle on Variable-Speed Fixed-Pitch Floating Offshore Wind Turbines for Optimizing Power Coefficient Using Experimental and CFD Models

2020 ◽  
Vol 10 (2) ◽  
pp. 201-212
Author(s):  
Wongsakorn Wisatesajja ◽  
Wirachai Roynarin ◽  
Decha Intholo
Keyword(s):  
Wind Turbine ◽  
Tilt Angle ◽  
Offshore Wind ◽  
Power Coefficient ◽  
Variable Speed ◽  
Offshore Wind Turbines ◽  
Pitch Control ◽  
Wind Speeds ◽  
Floating Offshore Wind Turbines ◽  
Fixed Pitch

This study focused on optimization of the power coefficient of floating offshore wind turbines (FOWTs) to maintain their wind power performance in order to overcome problems with the tilt angle resulting from an unstable wind turbine platform, which can reduce the effective area of wind turbine energy extraction. FOWTs with a variable-speed fixed-pitch control strategy were investigated using an experimental model in a wind tunnel and a CFD simulation model for analysis and comparison, using wind speeds of 2–5.5 m/s and tilt angles of 3.5–6.1°. The results showed that average rotational speed differences of 16.4% and optimal power coefficients of 0.35–0.36 could be maintained at tip speed ratios of 7.7–9.6 during wind speeds of 3–5 m/s with tilt angles of 3.9–5.8°. The results of this study provide insights into a new concept of power coefficient optimization using variable tilt angle for small to medium fixed pitch FOWTs, to reduce the cost of pitch control systems.

scholarly journals Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

2021 ◽  
Vol 9 (5) ◽  
pp. 543
Author(s):  
Jiawen Li ◽  
Jingyu Bian ◽  
Yuxiang Ma ◽  
Yichen Jiang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Motion Response ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions

2015 ◽  
Author(s):  
H. K. Jang ◽  
H. C. Kim ◽  
M. H. Kim ◽  
K. H. Kim
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Random Waves ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects. In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios. In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.

scholarly journals A Review of Recent Advancements in Offshore Wind Turbine Technology

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 579
Author(s):  
Taimoor Asim ◽  
Sheikh Zahidul Islam ◽  
Arman Hemmati ◽  
Muhammad Saif Ullah Khalid
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Offshore Wind ◽  
System Level ◽  
Offshore Wind Turbine ◽  
Component Level ◽  
Foundation Design ◽  
Offshore Wind Turbines

Offshore wind turbines are becoming increasingly popular due to their higher wind energy harnessing capabilities and lower visual pollution. Researchers around the globe have been reporting significant scientific advancements in offshore wind turbines technology, addressing key issues, such as aerodynamic characteristics of turbine blades, dynamic response of the turbine, structural integrity of the turbine foundation, design of the mooring cables, ground scouring and cost modelling for commercial viability. These investigations range from component-level design and analysis to system-level response and optimization using a multitude of analytical, empirical and numerical techniques. With such wide-ranging studies available in the public domain, there is a need to carry out an extensive yet critical literature review on the recent advancements in offshore wind turbine technology. Offshore wind turbine blades’ aerodynamics and the structural integrity of offshore wind turbines are of particular importance, which can lead towards system’s optimal design and operation, leading to reduced maintenance costs. Thus, in this study, our focus is to highlight key knowledge gaps in the scientific investigations on offshore wind turbines’ aerodynamic and structural response. It is envisaged that this study will pave the way for future concentrated efforts in better understanding the complex behavior of these machines.

Numerical Simulation of Dynamics of a Spar Type Floating Wind Turbine and Comparison With Laboratory Measurements

2016 ◽  
Author(s):  
Hyunseong Min ◽  
Cheng Peng ◽  
Fei Duan ◽  
Zhiqiang Hu ◽  
Jun Zhang
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Deep Water ◽  
Offshore Wind ◽  
Wind Loads ◽  
Floating Offshore Wind Turbines ◽  
The Cost

Wind turbines are popular for harnessing wind energy. Floating offshore wind turbines (FOWT) installed in relatively deep water may have advantages over their on-land or shallow-water cousins because winds over deep water are usually steadier and stronger. As the size of wind turbines becomes larger and larger for reducing the cost per kilowatt, it could bring installation and operation risks in the deep water due to the lack of track records. Thus, together with laboratory tests, numerical simulations of dynamics of FOWT are desirable to reduce the probability of failure. In this study, COUPLE-FAST was initially employed for the numerical simulations of the OC3-HYWIND, a spar type platform equipped with the 5-MW baseline wind turbine proposed by National Renewable Energy Laboratory (NREL). The model tests were conducted at the Deepwater Offshore Basin in Shanghai Jiao Tong University (SJTU) with a 1:50 Froude scaling [1]. In comparison of the simulation using COUPLE-FAST with the corresponding measurements, it was found that the predicted motions were in general significantly smaller than the related measurements. The main reason is that the wind loads predicted by FAST were well below the related measurements. Large discrepancies are expected because the prototype and laboratory wind loads do not follow Froude number similarity although the wind speed was increased (or decreased) in the tests such that the mean surge wind force matched that predicted by FAST at the nominal wind speed (Froude similarity) in the cases of a land wind turbine [1]. Therefore, an alternative numerical simulation was made by directly inputting the measured wind loads to COUPLE instead of the ones predicted by FAST. The related simulated results are much improved and in satisfactory agreement with the measurements.

scholarly journals Proposal and Performance Study of a Novel Mooring System with Six Mooring Lines for Spar-Type Offshore Wind Turbines

2021 ◽  
Vol 11 (24) ◽  
pp. 11665
Author(s):  
Shi Liu ◽  
Yi Yang ◽  
Chao Wang ◽  
Yuangang Tu
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Included Angle ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Spar-type floating offshore wind turbines commonly vibrate excessively when under the coupling impact of wind and wave. The wind turbine vibration can be controlled by developing its mooring system. Thus, this study proposes a novel mooring system for the spar-type floating offshore wind turbine. The proposed mooring system has six mooring lines, which are divided into three groups, with two mooring lines in the same group being connected to the same fairlead. Subsequently, the effects of the included angle between the two mooring lines on the mooring-system’s performance are investigated. Then, these six mooring lines are connected to six independent fairleads for comparison. FAST is utilized to calculate wind turbine dynamic response. Wind turbine surge, pitch, and yaw movements are presented and analyzed in time and frequency domains to quantitatively evaluate the performances of the proposed mooring systems. Compared with the mooring system with six fairleads, the mooring system with three fairleads performed better. When the included angle was 40°, surge, pitch, and yaw movement amplitudes of the wind turbine reduced by 39.51%, 6.8%, and 12.34%, respectively, when under regular waves; they reduced by 56.08%, 25.00%, and 47.5%, respectively, when under irregular waves. Thus, the mooring system with three fairleads and 40° included angle is recommended.

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