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Technical Brief

On the Use of Site Data to Define Extreme Turbulence Conditions for Wind Turbine Design

[+] Author and Article Information
Jae Sang Moon

Department of Civil,
Architectural,
and Environmental Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: mjaesang@gmail.com

Watsamon Sahasakkul

Department of Civil,
Architectural,
and Environmental Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: watsamon.kik@gmail.com

Mohit Soni

Department of Civil,
Architectural,
and Environmental Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: mohitsonit@utexas.edu

Lance Manuel

Professor
Department of Civil,
Architectural,
and Environmental Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: lmanuel@mail.utexas.edu

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received January 22, 2014; final manuscript received September 17, 2014; published online October 13, 2014. Assoc. Editor: Yves Gagnon.

J. Sol. Energy Eng 136(4), 044506 (Oct 13, 2014) (5 pages) Paper No: SOL-14-1024; doi: 10.1115/1.4028721 History: Received January 22, 2014; Revised September 17, 2014

In wind turbine design, external conditions to be considered depend on the intended site for the planned installation. Wind turbine classes, defined in terms of wind speed and turbulence parameters, cover most sites and applications. In the International Electrotechnical Commission's (IEC's) 61400-1 standard, there is a design load case that requires consideration for ultimate loading resulting from extreme turbulence conditions. Since site-specific wind conditions should not compromise the structural integrity of turbine installations, at some sites where class-based design may not apply, there is sometimes a need to establish extreme turbulence (50-year) levels as part of site assessment by making use of measurements. This should be done in a manner consistent with class-based design where the extreme turbulence model (ETM) provides 50-year turbulence standard deviation (σ) value as a function of the ten minute average hub-height wind speed, V. For one site in Germany and three contrasting terrain sites in Japan, wind velocity data are used to establish 50-year ETM levels. The inverse first-order reliability method (IFORM) is applied with 10 min data for this purpose. Sometimes, as in assessing wind farm wake effects, analysis of turbulence levels by direction sector is important because normal and extreme turbulence levels can vary by sector. We compare ETM levels by sector for the Hamburg, Germany site. The influence of terrain complexity on ETM levels is also of interest; the three sites in Japan have contrasting terrain characteristics—referred to as flat, hilly, and mountainous. ETM levels are compared for these three terrain types. An important overall finding of this study is that site-specific ETM levels can greatly exceed levels specified in the standard for class-based design.

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Figures

Grahic Jump Location
Fig. 1

Inverse FORM approach (the variables, U1 and U2, are standard normal variables mapped to empirical distributions for V and σ|V, derived from site data; beta represents the value that a standard normal variable must have so that its complementary CDF matches the target probability of exceedance, PT, of the ETM level σ.)

Grahic Jump Location
Fig. 2

Monthly variation of the mean σ with V (increasing radially) for the Hamburg site. (a) Monthly variation of mean σ (m/s) and (b) reference polar system for wind speed (radial)

Grahic Jump Location
Fig. 3

Hamburg, Germany Site: DE-01 and sector analysis. (a) ETM levels and (b) smoothed ETM levels

Grahic Jump Location
Fig. 4

Japan site: JP-07 (flat). (a) ETM levels and (b) smoothed ETM levels

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Fig. 5

Japan site: JP-37 (hilly). (a) ETM levels and (b) smoothed ETM levels

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Fig. 6

Japan site: JP-22 (mountainous). (a) ETM levels and (b) smoothed ETM levels

Grahic Jump Location
Fig. 7

Comparison of ETM levels for the four sites analyzed: DE-01, JP-07 (flat), JP-37 (filly), JP-22 (mountainous), and class-based ETM levels for turbine classes I-A and III-C

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