scholarly journals Suspension Design of a Semi-Submersible Platform

2016 ◽  
Author(s):  
Hongzhong Zhu ◽  
Changhong Hu ◽  
Yingyi Liu ◽  
Kangping Liao
Keyword(s):  
Wave Energy ◽  
Linear Models ◽  
Low Cost ◽  
State Space Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Ocean Energy ◽  
Floating Platform ◽  
Pitch Motion ◽  
Wave Energy Dissipation

With the development of ocean energy exploration, reliable and low cost semi-submersible platforms are expected to develop. The maximum pitching amplitude of a floater for floating offshore wind turbine should be less than a few degrees to avoid fatigue failure. In this paper, a novel conceptual design of a new type semi-submersible with suspensions for suppressing the pitch motion is presented. Many wave energy dissipation devices, such as add-on wave energy converters to a floating platform, could be regarded as the suspension system in our design. Firstly, linear models are applied to approximate the radiation forces and wave exciting forces so that the whole motion system is represented by a state-space model. Then, we show that design of suspensions leads to synthesize a controller via solving a constrained H∞ optimization problem. Finally, numerical examples are performed to verify the design and it can be shown that the pitch motion of the semi-submersible platform is remarkably reduced.

A Technology of Electrical Energy Generated From Ocean Power Using Flexible Piezoelectric Device

2010 ◽  
Author(s):  
Hidemi Mutsuda ◽  
Kenta Kawakami ◽  
Takayuki Kurokawa ◽  
Yasuaki Doi ◽  
Yoshikazu Tanaka
Keyword(s):  
Bluff Body ◽  
Electric Energy ◽  
Electrical Energy ◽  
Energy System ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Ocean Energy ◽  
Floating Platform ◽  
Piezoelectric Device

We have developed a way of harvesting electrical energy from the ocean power, e.g. tide, current, wave, breaking wave and vortex, using a flexible piezoelectric device consisting of piezo-electric polymer film (PVDF), silicon and natural rubber. The flexible piezoelectric device (FPED) is a hydro-electric ocean energy converter designed to convert renewable energy harnessed from ocean energy into usable electricity. The basic concept generating electric power using FPED is to utilize fluid structure interaction, e.g. flattering, flapping and periodic bending, caused by ocean energy. The FPED deformed by kinetic energy of the ocean power stores elastic energy and also converts it to the electric energy. We carried out some experiments using wave tank and the water tunnel with a bluff body. We have confirmed the electricity generated by wave, current and vortex using the FPED. The developed FPED could be a new technology of harvesting electrical energy from the ocean power. A floating platform attached FPED could be coupled with an offshore wind turbine as a hybrid energy system in ocean space.

scholarly journals Optimum Design of a Passive Suspension System of a Semisubmersible for Pitching Reduction

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Hongzhong Zhu ◽  
Changhong Hu ◽  
Yingyi Liu
Keyword(s):  
Controller Design ◽  
Design Method ◽  
Feedback System ◽  
Suspension System ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Practical Case ◽  
Floating Platform ◽  
Small Motion ◽  
Pitch Motion

With the development of ocean energy exploration, reliable semisubmersible platforms with very small motion are expected to develop. Especially, in a floating offshore wind turbine (FOWT) system, the maximum pitching amplitude is required to be less than a few degrees. To reduce wave-induced pitch motion, a new type semisubmersible with suspensions and a design method of the suspension coefficients are presented. In practical case, an add-on wave energy dissipation device mounted on a floating platform, such as the combined wave-wind energy converter system, could be regarded as the suspension system. In this study, first, the conceptual semisubmersible is described. Then, the hydrodynamic loads to the semisubmersible are linearized so that the whole system is expressed by a state-space model. The suspension design problem is transformed into solving a constrained H∞ optimization problem, which after all is the optimal controller design of a feedback system. Finally, numerical examples are performed to verify the effectiveness of the design. The results illustrate that the pitch motion of the semisubmersible can be remarkably reduced by the designed suspensions.

scholarly journals Large eddy simulations of offshore wind turbine wakes for two floating platform types

2020 ◽  
Vol 1452 ◽  
pp. 012034
Author(s):  
H M Johlas ◽  
L A Martínez-Tossas ◽  
M A Lackner ◽  
D P Schmidt ◽  
M J Churchfield
Keyword(s):  
Wind Turbine ◽  
Large Eddy Simulations ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Large Eddy

Dynamic Modeling and Simulation of a Spar Floating Offshore Wind Turbine With Consideration of the Rotor Speed Variations

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Mohammed Khair Al-Solihat ◽  
Meyer Nahon ◽  
Kamran Behdinan
Keyword(s):  
System Dynamics ◽  
Wind Turbine ◽  
Torque Control ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Aerodynamic Load ◽  
Floating Platform ◽  
Dynamic Simulations ◽  
Floating Offshore Wind Turbine ◽  
Wind Turbine Tower

This paper presents a rigid multibody dynamic model to simulate the dynamic response of a spar floating offshore wind turbine (FOWT). The system consists of a spar floating platform, the moorings, the wind turbine tower, nacelle, and the rotor. The spar platform is modeled as a six degrees-of-freedom (6DOFs) rigid body subject to buoyancy, hydrodynamic and moorings loads. The wind turbine tower supports rigid nacelle and rotor at the tip. The rigid rotor is modeled as a disk spinning around its axis and subject to the aerodynamic load. The generator torque control law is incorporated into the system dynamics to capture the rotor spinning speed response when the turbine is operating below the rated wind speed. The equations of motions are derived using Lagrange's equation in terms of the platform quasi-coordinates and rotor spin speed. The external loads due to hydrostatics, hydrodynamics, and aerodynamics are formulated and incorporated into the equations of motion. The dynamic simulations of the spar FOWT are performed for three load cases to examine the system eigen frequencies, free decay response, and response to a combined wave and wind load. The results obtained from the present model are validated against their counterparts obtained from other simulation tools, namely, FAST, HAWC2, and Bladed, with excellent agreement. Finally, the influence of the rotor gyroscopic moment on the system dynamics is investigated.

scholarly journals Hydrodynamic investigation on an OWC wave energy converter integrated into an offshore wind turbine monopile

2020 ◽  
Vol 162 ◽  
pp. 103731 ◽  
Author(s):  
Yu Zhou ◽  
Dezhi Ning ◽  
Wei Shi ◽  
Lars Johanning ◽  
Dongfang Liang
Keyword(s):  
Wind Turbine ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Energy Converter

Structural Analysis of Conical Bottom-Supported Offshore Wind Turbine Foundation

2011 ◽  
Vol 117-119 ◽  
pp. 726-729
Author(s):  
Yuan Lin Zhao ◽  
Zhi Wen Zhu ◽  
Shi Deng
Keyword(s):  
Wind Turbine ◽  
Low Cost ◽  
Element Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Shallow Sea ◽  
Offshore Wind Power ◽  
The Finite Element Model ◽  
Conical Bottom ◽  
Survival Condition

In this paper, a kind of conical bottom-supported offshore wind turbine foundation was developed. The finite element model was built in SESAM and the structure was analyzed in operating condition and survival condition. The result shows that both the bearing platform and the conical bottom can satisfy the requirement of displacement and strength. The new kind of platform can be applied in shallow sea and offshore, easy to tow, and has low cost, which is helpful to offshore wind power exploitation.

Structural Control of an Ultra-Large Semi-Submersible Floating Offshore Wind Turbine

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Zhixin Zhao ◽  
Wenhua Wang ◽  
Dongdong Han ◽  
Wei Shi ◽  
Yulin Si ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Dynamic Model ◽  
Structural Control ◽  
Degrees Of Freedom ◽  
Vibration Suppression ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine ◽  
Proposed Model

Abstract A braceless semi-submersible floating platform is proposed for a Technical University of Denmark (DTU) 10-MW wind turbine at moderate water depths with reference to an existing National Renewable Energy Laboratory (NREL) 5-MW braceless semi-submersible floating platform, and a servo control system for a 10-MW semi-submersible floating offshore wind turbine (FOWT) is introduced. To control the ultimate and fatigue loads of the FOWT, a fore-aft tuned mass damper (TMD) installed in the nacelle of the 10-MW semi-submersible FOWT was investigated for vibration alleviation and load reduction. Considering the hydrodynamic and mooring effect, a four degrees-of-freedom (DOFs) (platform surge and pitch motions, tower fore-aft bending, and TMD translation) simplified dynamic model for the 10-MW semi-submersible FOWT is established based on D’Alembert’s principle. Then, the parameter estimation is conducted based on the Levenberg–Marquardt (LM) algorithm, and the simplified dynamic model was further verified by comparing the output responses with FAST and the proposed model. Furthermore, the exhaustive search (ES) and genetic algorithm (GA) are embedded into the simplified dynamic model to optimize the TMD parameters. Finally, a fully coupled time-domain simulation for all the selected environmental conditions is conducted in FAST, and the vibration suppression performance of the optimized TMD design for the 10-W semi-submersible FOWT was further examined and analyzed.

scholarly journals Numerical Study of a Proposed Semi-Submersible Floating Platform with Different Numbers of Offset Columns Based on the DeepCwind Prototype for Improving the Wave-Resistance Ability

2019 ◽  
Vol 9 (6) ◽  
pp. 1255
Author(s):  
Zhenqing Liu ◽  
Yicheng Fan ◽  
Wei Wang ◽  
Guowei Qian
Keyword(s):  
Wind Turbines ◽  
Numerical Study ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Offshore Wind Turbines ◽  
Irregular Wave ◽  
Decay Test ◽  
Floating Offshore Wind Turbines

DeepCwind semi-submersible floating offshore wind turbines have been widely examined, and in some countries this type of floating offshore wind turbine has been adopted in the construction of floating wind farms. However, the DeepCwind semi-submersible floating offshore wind turbines still experience large surge motion that limits their operational time. Therefore, in this study, a semi-submersible floating platform with different numbers of offset columns, but with the same total weight, based on the DeepCwind prototype is proposed. From the free-decay test, it was found that the number of the floating columns will affect the natural frequency of the platform. Furthermore, the regular wave test in the time domain and the irregular wave test in the frequency domain show that increasing the number of the floating columns will reduce the surge motion greatly, while the effects in the heave and pitch motions are not obvious.

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