scholarly journals Low Wind Speed Technology Phase II: Developing Techniques to Evaluate the Designs and Operating Environments of Offshore Wind Turbines in the Mid-Atlantic and Lower Great Lakes Region; AWS Truewind, LLC

2006 ◽  
Author(s):  
Keyword(s):  
Wind Speed ◽  
Great Lakes ◽  
Phase Ii ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Great Lakes Region ◽  
Offshore Wind Turbines ◽  
Low Wind Speed ◽  
Operating Environments

Joint Probability Distribution of Environmental Conditions for Design of Offshore Wind Turbines

2017 ◽  
Author(s):  
Jan-Tore H. Horn ◽  
Jørgen R. Krokstad ◽  
Jørgen Amdahl
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Environmental Conditions ◽  
Wind Wave ◽  
Joint Probability ◽  
Offshore Wind ◽  
Joint Probability Distribution ◽  
Peak Period ◽  
Offshore Wind Turbines ◽  
Mean Wind Speed

The design process for offshore wind turbines includes a fatigue life evaluation of the structure with the relevant environmental conditions at the specified wind farm location. Such analyses require long-term distributions of the environmental parameters including their correlation. In general, the significant wave height, wave peak period and mean wind speed are the most important parameters for describing offshore environmental conditions. However, due to the low side-to-side damping level of offshore bottom-fixed wind turbines, wave directions misaligned with the wind direction may excite low-damped vibrational modes. As a consequence, the accumulated fatigue damage in the wind turbine foundation may change, compared to collinear wind and waves. In the current work, an extension to the three-parameter environmental joint probability distribution is presented, with the resulting distribution being a function of the significant wave height, peak period of the total sea, mean wind speed and the wave directional offset compared to the mean wind heading i.e. the wind-wave misalignment. The sea states within a 1-year return period for Dogger Bank are presented, as well as the 10- and 50-year environmental contour lines and extreme wind-wave misalignment angles.

scholarly journals Optimal Design of Rated Wind Speed and Rotor Radius to Minimizing the Cost of Energy for Offshore Wind Turbines

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2728 ◽  
Author(s):  
Longfu Luo ◽  
Xiaofeng Zhang ◽  
Dongran Song ◽  
Weiyi Tang ◽  
Jian Yang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Optimal Design ◽  
Wind Energy ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Energy ◽  
Offshore Wind Turbines ◽  
Cost Of Energy ◽  
The Cost

As onshore wind energy has depleted, the utilization of offshore wind energy has gradually played an important role in globally meeting growing green energy demands. However, the cost of energy (COE) for offshore wind energy is very high compared to the onshore one. To minimize the COE, implementing optimal design of offshore turbines is an effective way, but the relevant studies are lacking. This study proposes a method to minimize the COE of offshore wind turbines, in which two design parameters, including the rated wind speed and rotor radius are optimally designed. Through this study, the relation among the COE and the two design parameters is explored. To this end, based on the power-coefficient power curve model, the annual energy production (AEP) model is designed as a function of the rated wind speed and the Weibull distribution parameters. On the other hand, the detailed cost model of offshore turbines developed by the National Renewable Energy Laboratory is formulated as a function of the rated wind speed and the rotor radius. Then, the COE is formulated as the ratio of the total cost and the AEP. Following that, an iterative method is proposed to search the minimal COE which corresponds to the optimal rated wind speed and rotor radius. Finally, the proposed method has been applied to the wind classes of USA, and some useful findings have been obtained.

The Effect of Yaw Error on the Mooring Systems of Floating Offshore Wind Turbines in Extreme Weather Conditions

2018 ◽  
Author(s):  
Evelyn R. Hunsberger ◽  
Spencer T. Hallowell ◽  
Casey M. Fontana ◽  
Sanjay R. Arwade
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Wind Farm ◽  
Turbine Blades ◽  
Wind Farms ◽  
Offshore Wind ◽  
Single Line ◽  
Direct Result ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

As floating offshore wind turbines (FOWTs) become the most viable option for wind farms in deeper waters, it is important to investigate their dynamic response in inclement conditions when failures, such as yaw misalignment, are more likely to occur. This research uses hour-long simulations in FAST, software developed by The National Renewable Energy Lab (NREL), to analyze the effect of yaw error on anchor tensions and platform displacements in both a traditional single-line wind farm geometry, where each anchor is connected to one turbine, and an optimum multiline anchor geometry, where each anchor is connected to three turbines. NREL’s 5 MW reference turbine on a semi-submersible base is analyzed using six realizations of each combination of co-directional wind and waves, wind speed and yaw error; resulting in 2,484 simulations in total. The variability in platform displacements and mooring forces increases as wind speed increases, and as yaw errors approach critical values. The angle of incidence of the co-directional wind and waves dictates which anchor experiences the most tension for both the single-line and multiline concepts. In the multiline geometry, the greatest increases in anchor tension occurs when the downwind turbine has yaw error. Yaw error increases the maximum anchor tension by up to 43% in the single-line geometry and up to 37% in the multiline geometry. In the multiline geometry, yaw error causes the direction of the resultant anchor force to vary by up to 20°. These changes in anchor tension magnitudes and directions are governed by the platform displacements, and are a direct result of the differences in the tangential and normal coefficients of drag of the turbine blades. When designing floating offshore wind farms, the influence of yaw error on loading magnitudes and directions are to be considered when determining the necessary capacities and calculating the corresponding reliabilities for wind turbine components.

The Influence of Foundation Modeling Assumptions on Long-Term Load Prediction for Offshore Wind Turbines

2009 ◽  
Author(s):  
Erica Bush ◽  
Lance Manuel
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Stochastic Simulations ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Extreme Loads ◽  
Reliability Method ◽  
Flexible Foundation

The objective of this study is to investigate the effect of alternative monopile foundation models for shallow-water offshore wind turbines on extreme loads associated with 20-year return periods. Foundation models with tower base fixed at the mudline, with apparent fixity points below the mudline, with coupled transverse and lateral springs at the mudline, and with distributed springs over the entire penetration depth of the monopile are compared. We employ a utility-scale 5 MW offshore wind turbine model with a 90-meter hub height in stochastic simulations; the turbine is sited in 20 meters of water. Selected 20-year wind speed and wave height combinations are employed as we study comparative response statistics, power spectra, and probability distributions of extreme loads for the fixed-base and the three different flexible foundation models. A discussion on the varying dynamics, on short-term response statistics, and on extrapolated long-term loads from limited simulation is presented. Sea states involving wind speeds close to the turbine’s rated wind speed are found to control 20-year loads, and the flexible foundation models are found to experience higher extreme loads than the fixed-based case. Overall, the three flexible foundation models appear to yield similar long-term loads based on an Inverse FORM (First-Order Reliability Method) approach for the selected turbine and soil profile used in this study.

Integrated Dynamic Analysis of Floating Offshore Wind Turbines

2006 ◽  
Author(s):  
Finn Gunnar Nielsen ◽  
Tor David Hanson ◽  
Bjo̸rn Skaare
Keyword(s):  
Wind Speed ◽  
Dynamic Analysis ◽  
Wind Turbines ◽  
Control Strategy ◽  
Rotor Blade ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Pitch Control ◽  
Floating Offshore Wind Turbines ◽  
Wind Velocities

Two different simulation models for integrated dynamic analysis of floating offshore wind turbines are described and compared with model scale experiments for the Hywind concept for floating offshore wind turbines. A variety of both environmental conditions and wind turbine control schemes are tested. A maximum power control strategy is applied for wind velocities below the rated wind speed for the wind turbine, while a constant power control strategy is achieved by controlling the rotor blade pitch for wind velocities above rated wind speed. Conventional rotor blade pitch control for wind velocities above rated wind speed introduces negative damping of the tower motion. This results in excitation of the natural frequency in pitch for the tower and may lead to unacceptable tower motions. Active damping of the undesirable tower motions is obtained by an additional pitch control algorithm based on measurement of the tower velocity.

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines
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