Wind Energy
Online ISSN : 1884-457X
Print ISSN : 0387-6217
ISSN-L : 0387-6217
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Volume 39, Issue 2
Displaying 1-44 of 44 articles from this issue
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  • Assessment of weather downtime for the construction of offshore wind power plants by using wind and wave simulations
    Yuka KIKUCHI, Takeshi ISHIHARA
    2015 Volume 39 Issue 2 Pages A_23-A_30
    Published: 2015
    Released on J-STAGE: September 30, 2016
    DOIhttps://doi.org/10.11333/jwea.39.2_A_23
    JOURNAL FREE ACCESS
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    In this study, the workability was assessed for offshore wind farm construction by using the numerical simulations for winds and waves. The predicted wind speeds, significant wave heights and significant wave periods were compared with measurements. Annual average values of absolute monthly error of wind speed, significant wave height and significant wave period were 4.30%, 12.3% and 7.8%, respectively. Then, seasonal occurrence times were examined for measured and predicted wind speeds, significant wave heights and significant wave periods. Predicted wave heights smaller than 1.0 m and predicted wave periods smaller than 6 s overestimated the measurements. The biases of predictions were modeled with linear equations and corrected to improve the accuracy of predictions. Construction records and work criteria of Choshi and Kitakyushu offshore wind farms were investigated and the sensitivity of construction methods on weather downtime were investigated. Choshi had a high sensitivity where the wave condition is severe, while Kitakyushu had a low sensitivity where the wave condition is mild. Finally, the weather downtimes were assessed with the investigated criteria and predicted wind and wave conditions, which had a good accordance with the records.
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  • Structural Improvement of Lightning Receptor for Wind Turbine Blade
    Yasuhiro FUJITA, Atsutoshi MUTO, Terufumi YAGI, Nobuyuki HONJO, Shin-i ...
    2015 Volume 39 Issue 2 Pages A_31-A_36
    Published: 2015
    Released on J-STAGE: September 30, 2016
    DOIhttps://doi.org/10.11333/jwea.39.2_A_31
    JOURNAL FREE ACCESS
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    Most of wind turbines have metallic receptors at the tip of their blades as lightning protection. Recently, aluminum tip receptors of some large wind turbines have dropped out accidentally. After the investigation, it is expected the following phenomena caused dropout accidents. At first, they were struck by lightning through the blade skin and the internal air and moisture expanded explosively by arc heat. Subsequently, bonded part around the tip receptor was fractured by pressure, and then holding force of the receptor was lost. To prevent similar accidents, the authors revised the tip receptor and its bonding structure. High-current arc tests and tensile strength tests were carried out on blade specimens which equipped the revised receptors. As a result, it was confirmed that the revised receptor can endure electric charge amount as high as 1500 C and sixteen times as much as the extreme tensile force.
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