Principal Research Results

Study on Wind Turbine Considering the Wind Characteristics(Typhoon and Wind Turbulence) in Japan
Background
Introduction of wind turbine generation systems is recently being advanced in Japan. Also, the scale of the wind turbines
tends to be growing larger. There is the International Standard (IEC61400) for wind power generation systems including the windturbine itself. The systems are generally supplied as a standard product fitting with the wind turbine class that satisfies the standard
wind condition (combination of the wind speed and turbulence) provided in the International Standard. However, since this standard isbased on the wind characteristics in Northern Europe, the influences of strong wind speed and turbulence by typhoon and complex
terrain, which are specific to Japan, are not considered. The influences of strong thunderbolts in winter are also not satisfactorilyconsidered. From such situations, many troubles concerning blade damage by typhoon or lightning have recently occurred in Japan. It
is also thought that the influence of the troubles grows more serious as wind turbines become larger. From the viewpoint of securing
the safety of wind power generation systems, there is a strong need to review the technological standards and devise the design guidelines considering the wind and thunderbolt conditions, specific to Japan. The development of a forecasting system for wind power
generation and evaluation of the prediction error are also needed under such Japanese weather conditions.

Objectives
The purpose of this study is to develop an evaluation method of wind conditions and a wind power generation forecasting
system considering the characteristic weather conditions specific to Japan in the wind turbine design.

Principal Results
1. Wind tunnel test using a small-scale wind turbine model
The wind turbine model of 1/30 scale corresponding to the 1,000kW class machine (2m diameter rotor and rotor rotational
speed 600 rpm in the model) was made to verify the analytical accuracy and to evaluate the influence of the response of wind turbine
by fluctuating wind. It had been experimented on at a large wind tunnel facility of Mitsubishi Heavy Industries, Ltd. As a result, theinfluences on the blades and the rotor axis of the fluctuating wind condition were well found, and the accuracy of the numerical analysis was confirmed (Figure 1).
2. Investigation of the evaluation techniques about wind turbulence that influence wind turbines overthe complex terrain.
The wind speed and turbulence were analyzed in condition of the simple wavy terrain by our own four fluid-analysis-codeswith the different numerical handlings about the turbulence modeling and the coordinates. It was found that each code well calculated
the flow over the simple wavy terrain. It was also confirmed that the calculated results were good corresponding to the observed dataover the complex terrain in a wind farm by using one code among them (Figure 2).
3. Development of the forecasting system for wind power generation in a wind farm
The GPV data of JMA, NCEP, ECMWF, meso-scale weather prediction model of UT, JWA, CTC, CRIEPI, and CFD modelof JWA, CRIEPI were compared each other. Finally, the uncertain forecasting errors were discussed, and the forecasting system wasimproved. Based on these results, the forecasting system for wind power generation for each wind turbine and the total generation in awind farm was developed.
4. Verification of the forecasting system
Using the forecasting system, the wind power for five wind farms (Tohoku 3 site, Kanto 1 site, and Kyushu 1 site) withdifferent wind conditions was forecasted and compared. The target accuracy value (the improvement rate (20% or more on that day,
30% or more on the next day) and the prediction error rate (15% or less on that day, 20% or less on the next day)) were achieved.

Future Developments
The results of review on the wind resistance, fatigue, and lightning might be reflected in design manuals such as the"Ministerial ordinance on technical criteria for power generation wind equipment". The practical use of the forecasting system forwind power generation will be advanced and examined in new locations such as mountains and the ocean.
This study is executed as part of the research and development of “Project for Establishing Wind Power Guidelines forJapan” and “Wind Power Stabilization Technology Development Project - Development of Wind Power Prediction Models Based on
Numerical Weather Prediction-” that is consigned by the New Energy and Industrial Technology Development Organization (NEDO).
Main Researcher: Nobukazu Tanaka,
Dr. of Engineering, Executive Research Engineer, Civil Engineering Laboratory1127. New Energy

Fig.1 Wind load evaluation on a wind turbine at typhoon
Left: Photograph in the main part of a wind turbine model (1/30 reduced scale) used for wind tunnel test (state to open nacelle cover)
Right: Comparison of the simulation and the observation results corresponding to time change of the wind (The wind speed rapidly changes
at the typhoon. The change of the load was confirmed to be accurately reproduced using the existing analytical code).

︵ｍ︶︵HeightStandard deviation︵︶︶

Wind turbulence（ｍ）

Fig.2 Evaluation of the wind turbulence that uses numerical analysis code intended for wind farmon complex terrain
Left: Vertical space distribution of standard deviation of fluctuating wind obtained by numerical analysis (The value of red areas is strong,
and the value of blue areas is weak. It is understood that the standard deviation of the change velocity of the wind that is one of theevaluation parameters of the fatigue strength of the wind turbine has changed spatially).
Right: Vertical distribution of standard deviation of fluctuating wind in wind turbine installation point (It agrees well, and it is understoodthat the fatigue evaluation of the wind turbine that originates in the wind turbulence by using the numerical analysis is possible withthe observation value (circles) and the analytical result (solid lines)).
WindWind Speed

MARS
RSM- GPV
RSM-GPV[m/ s]

25
20
15
10
50
2006/12/22 21:00

Obs.
Obs.

2006/12/23 9:00

2006/12/24 9:00

2006/12/24 21:00

WindWind Direct ion

360
[deg]

2006/12/23 21:00

MARS
RSM- GPV
RSM-GPV270

Obs.
Obs.

180
900
2006/12/22 21:00

2006/12/23 9:00

2006/12/24 9:00

2006/12/24 21:00
MARS
RSM- GPV
RSM-GPVObs.
Obs.

WindWind Power

1500
[kW]

2006/12/23 21:00

1000
500
0

2006/12/22 21:00

2006/12/23 9:00

2006/12/23 21:00

2006/12/24 9:00

2006/12/24 21:00

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Fig.3 Example of the forecasting
result of using the weather
forecasting model.
The comparison of the calculation andobservation value of wind speed, direction, andpower generation forecasted by our own
weather forecast system (MARS). And,meteorological data (RSM-GPV in figure) werecompared. It was found to be able to capture
local weather phenomena such as passing lowpressure by using the weather forecastingmodel. (Red: Change by passing of small lowpressure, Green: Steady increase of power
generation output according to flow of local
wind, typical to these area)

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