Load Reduction on Offshore Wind Turbines by Aerodynamic Flaps

2017 ◽  
Author(s):  
Shilpa Thakur ◽  
Nilanjan Saha
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Load Reduction ◽  
Horizontal Axis Wind Turbine ◽  
Trailing Edge ◽  
Hydrodynamic Loads ◽  
Trailing Edge Flaps ◽  
Unsteady Effects ◽  
Bem Theory

This paper focuses on load reduction by implementing controllable trailing-edge flaps on an offshore wind turbine (OWT) supported on different fixed bottom structures in various water depths. The benchmark NREL 5-MW offshore horizontal axis wind turbine is used as a reference. This work utilizes the wind turbine simulation tool FAST with coupled stochastic aerodynamic-hydrodynamic analysis for obtaining the responses. The flap is controlled using an external dynamic link library through PID controller. Blade element momentum (BEM) theory and Morison equation are used to compute the aerodynamic and hydrodynamic loads, respectively. BEM theory is presently modified to account for unsteady effects of flaps along the blade span. Variation in force coefficients is shown due to unsteady effects of flaps. The present analysis results show reduction up to 8–29% in blade loads for the turbine with different support structures on implementing controllable trailing edge flaps. Also, an influence of blade load reduction on tower base and nacelle is shown. Tower loads are calculated considering aerodynamic and hydrodynamic loads individually. This study can form the basis for evaluating the performance for large-scale fixed offshore wind turbine rotors.

Load Mitigation Using Slotted Flaps in Offshore Wind Turbines

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Shilpa Thakur ◽  
K. A. Abhinav ◽  
Nilanjan Saha
Keyword(s):  
Large Scale ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Dynamic Link Library ◽  
Trailing Edge ◽  
Offshore Wind Turbines ◽  
Trailing Edge Flaps ◽  
Bottom Structures ◽  
Unsteady Effects ◽  
Bem Theory

This paper focuses on load mitigation by implementing controllable trailing-edge slotted flaps on the blades of an offshore wind turbine (OWT). The benchmark NREL 5 MW horizontal axis OWT is subjected to coupled stochastic aerodynamic-hydrodynamic analysis for obtaining the responses. The OWT is supported on three different fixed-bottom structures situated in various water depths. Blade element momentum (BEM) theory and Morison's equation are used to compute the aerodynamic and hydrodynamic loads, respectively. Presently, the load reduction obtained by means of the slotted flaps is regulated using an external dynamic link library considering the proportional-integral-derivative (PID) controller. BEM theory is presently modified to account for unsteady effects of flaps along the blade span. The present analysis results show reduction up to 20% in blade and tower loads for the turbine with different support structures on implementing controllable trailing edge flaps (TEFs). This study can form the basis for evaluating the performance of large-scale fixed OWT rotors.

scholarly journals Modeling and Investigation of Blade Trailing Edge of Vertical Axis Offshore Wind Turbine

2021 ◽  
Vol 13 (19) ◽  
pp. 10905
Author(s):  
Lin Pan ◽  
Ze Zhu ◽  
Zhaoyang Shi ◽  
Leichong Wang
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Capture Rate ◽  
Vertical Axis ◽  
Wind Turbine Blade ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Trailing Edge ◽  
Structure Changes ◽  
Trailing Edge Flaps

In this study, the structure of the trailing edge of the vertical axis offshore wind turbine blade is modified. First, according to the method of parameterization, the offshore wind turbine model is established, and a series of characteristics of the offshore wind turbine are obtained. Second, we add flaps with different lengths to the trailing edge of NACA0021 airfoil to obtain different dynamic characteristics. The angle of the additional trailing edge flaps is modified. Finally, a simulation model for the modified airfoil of the vertical axis offshore wind turbine is reestablished, and the variable characteristics of the performance is studied. Through the optimization and analysis of the blade structure, this study has obtained the best parameters of the length and angle of the offshore wind turbine blade trailing edge flap. The optimization of the blade structure changes the flow field around the blade, which significantly improves the maximum wind energy capture rate and self-starting ability of the vertical axis offshore wind turbine.

scholarly journals The Effect of the Second-Order Wave Loads on Drift Motion of a Semi-Submersible Floating Offshore Wind Turbine

2020 ◽  
Vol 8 (11) ◽  
pp. 859
Author(s):  
Thanh-Dam Pham ◽  
Hyunkyoung Shin
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Second Order ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Hydrodynamic Loads ◽  
Drift Motion ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Floating offshore wind turbines (FOWTs) have been installed in Europe and Japan with relatively modern technology. The installation of floating wind farms in deep water is recommended because the wind speed is stronger and more stable. The design of the FOWT must ensure it is able to withstand complex environmental conditions including wind, wave, current, and performance of the wind turbine. It needs simulation tools with fully integrated hydrodynamic-servo-elastic modeling capabilities for the floating offshore wind turbines. Most of the numerical simulation approaches consider only first-order hydrodynamic loads; however, the second-order hydrodynamic loads have an effect on a floating platform which is moored by a catenary mooring system. At the difference-frequencies of the incident wave components, the drift motion of a FOWT system is able to have large oscillation around its natural frequency. This paper presents the effects of second-order wave loads to the drift motion of a semi-submersible type. This work also aimed to validate the hydrodynamic model of Ulsan University (UOU) in-house codes through numerical simulations and model tests. The NREL FAST code was used for the fully coupled simulation, and in-house codes of UOU generates hydrodynamic coefficients as the input for the FAST code. The model test was performed in the water tank of UOU.

Numerical Simulations of Aerodynamic Feature for Variable Speed Offshore Wind Turbine

2011 ◽  
Vol 52-54 ◽  
pp. 1556-1559
Author(s):  
Ping He ◽  
Nai Chao Chen ◽  
Dan Mei Hu
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Gas Flow ◽  
Rapid Change ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Total Force ◽  
Variable Speed ◽  
Horizontal Axis Wind Turbine ◽  
Blade Height

The liquid-gas flow is proposed to accurately simulate the offshore environmental state. The aerodynamic feature is estimated using the three-dimensional model of horizontal-axis wind turbine with NRELS809 series aerofoil by means of the simulating software tool of FLUENT. The variable speed is implemented via the six different wind speeds. The calculated results show that the similarly evolutional tendency of velocity occurs in the wake region when operating at the six variable speeds. The stall speed is related to blade height and wind speed. The small blade height or large wind speed also leads to the serious stall phenomenon. The total force is conducted to estimate the potential capability for leeward and windward surface to capture wind power. The calculated results reveal that the larger wind speed facilitates generating the more magnitude of total force. However, the velocity and force feature for the wind turbine has the especially rapid change at the wind speed of 6 m/s, which perhaps results from the intrinsic geometry and configuration.

At Sea Experiment of a Hybrid Spar for Floating Offshore Wind Turbine Using 1/10-Scale Model

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Tomoaki Utsunomiya ◽  
Hidekazu Matsukuma ◽  
Shintaro Minoura ◽  
Kiyohiko Ko ◽  
Hideki Hamamura ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Prestressed Concrete ◽  
Cost Effective ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Prototype Model ◽  
Horizontal Axis Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Level 3

This study aims at development of a cost-effective, floating offshore wind turbine. The prototype model considered herein is composed of (1) 2-MW horizontal-axis wind turbine (HAWT) of downwind type, (2) steel monotower with 55-m hub height above sea level, (3) steel-prestressed concrete (PC) hybrid SPAR-type foundation with 70-m draft, and (4) catenary mooring system using anchor chains. In order to demonstrate the feasibility of the concept, an at-sea experiment using a 1/10-scale model of the prototype has been made. The demonstrative experiment includes (1) construction of the hybrid SPAR foundation using PC and steel, the same as the prototype; (2) dry-towing and installation to the at-sea site at 30-m distance from the quay of the Sasebo shipbuilding yard; (3) generating electric power using a 1 kW HAWT; and (4) removal from the site. During the at-sea experiment, wind speed, wind direction, tidal height, wave height, motion of the SPAR, tension in a mooring chain, and strains in the tower and the SPAR foundation have been measured. Motion of the SPAR has been numerically simulated and compared with the measured values, where basically good agreement is observed.

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