1:48 PM - 2:03 PM
[MZZ48-01] Overview of the NEDO project in Mutsu-Ogawara site to establish a method for offshore wind resource assessment
Keywords:Offshore wind energy, Wind measurement campaign, Doppler LiDAR, Atmospheric stability, Turbulence intensity, Wind met mast
A typical method for wind measurements prior to the construction of a wind farm is to use a met mast. However, since the typical hub height of the latest large offshore wind turbine can exceed 120 m, such a measurement with a met mast has been getting more difficult recently. Thus, remote sensing devices, such as scanning LiDAR and floating LiDAR, which can measure wind speeds up to several hundred meters in height, has been developed for surveying offshore wind conditions. For this reason, the New Energy and Industrial Technology Development Organization (NEDO) Fixed Offshore Wind Farm Development Support Project (Establishment of Offshore Wind Resource Assessment Method) (2019-22FY) is now underway to verify the practical effectiveness of these remote sensing devices through intensive meteorological observations at Mutsu-Ogawara, Aomori Prefecture.
The purpose of this paper is to introduce the Mutsu Ogawara site, which is one of valuable observation fields for coastal meteorology research in Japan. This paper mainly presents the early analysis of observation data from the measurement campaign with onshore and offshore met masts and vertical LiDARs. In particular, it focuses on the differences in wind conditions between the onshore (St. A) and offshore (St. B) stations, which are deployed about 1.6 km apart.
The vertical profiles of the period-mean wind speeds at St. A and St. B are shown in Figure 2. The wind profiles are depicted for each stability condition. It is noteworthy that while the mean wind speeds are similar at the two sites at altitudes above 150m, they differ at lower altitudes. The difference is more pronounced when the atmospheric stability over the sea area is unstable. This is considered due to the intensification of vertical mixing in the internal boundary layer during the unstable conditions.
It is known that the vertical shear of wind speed increases as the atmosphere becomes stable, and the wind speed difference between the upper and lower layers becomes larger. At St. B, for the sea-sector wind in a stable condition, the vertical sheer is relatively large up to about 70 m height, but it becomes smaller in the upper layers (about 70-180 m height), resulting in an S-shaped distorted profile. In other words, the wind characteristics inferred from the atmospheric stability in the surface layer can be confirmed only below 70 m. This fact means that wind conditions above 70m, corresponding to the swept area of an offshore wind turbine, cannot be estimated from lower-level measurements from a buoy or a short met mast, and it is thus necessary to measure them with scanning or floating LiDARs.
This paper is based on results obtained from a project, JPNP07015, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). The authors are grateful to all the project.
The purpose of this paper is to introduce the Mutsu Ogawara site, which is one of valuable observation fields for coastal meteorology research in Japan. This paper mainly presents the early analysis of observation data from the measurement campaign with onshore and offshore met masts and vertical LiDARs. In particular, it focuses on the differences in wind conditions between the onshore (St. A) and offshore (St. B) stations, which are deployed about 1.6 km apart.
The vertical profiles of the period-mean wind speeds at St. A and St. B are shown in Figure 2. The wind profiles are depicted for each stability condition. It is noteworthy that while the mean wind speeds are similar at the two sites at altitudes above 150m, they differ at lower altitudes. The difference is more pronounced when the atmospheric stability over the sea area is unstable. This is considered due to the intensification of vertical mixing in the internal boundary layer during the unstable conditions.
It is known that the vertical shear of wind speed increases as the atmosphere becomes stable, and the wind speed difference between the upper and lower layers becomes larger. At St. B, for the sea-sector wind in a stable condition, the vertical sheer is relatively large up to about 70 m height, but it becomes smaller in the upper layers (about 70-180 m height), resulting in an S-shaped distorted profile. In other words, the wind characteristics inferred from the atmospheric stability in the surface layer can be confirmed only below 70 m. This fact means that wind conditions above 70m, corresponding to the swept area of an offshore wind turbine, cannot be estimated from lower-level measurements from a buoy or a short met mast, and it is thus necessary to measure them with scanning or floating LiDARs.
This paper is based on results obtained from a project, JPNP07015, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). The authors are grateful to all the project.