Accounting for the Atmospheric Stability in Wind Resource Variations and Its Impacts on the Power Generation by Concentric Equivalent Wind Speed

Ryu, Geon-Hwa; Kim, Dong‐Hyeok; Lee, Hwa-Woon; Park, Soon-Young; JungWoo, Yoo; Kim, Hyun‐Goo

doi:10.7836/kses.2016.36.1.049

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…It is an index of atmospheric stability indicating the degree of dominance of buoyancy over the shear effect. The MO similarity theory is basically organized under five hypotheses [13,43]:…”

Section: Monin-obukhov Lengthmentioning

confidence: 99%

Atmospheric Stability Effects on Offshore and Coastal Wind Resource Characteristics in South Korea for Developing Offshore Wind Farms

Ryu

Kim²,

Kwak

et al. 2022

Energies

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South Korea is surrounded by the sea on three sides. The characteristics of offshore wind resources vary from region to region due to the influence of the distribution of the coastline and differences in roughness length and atmospheric stability between the coast and the sea. In particular, turbulent gusts and low-level wind shear occurring near the hub height of the wind turbine within the atmospheric boundary layer have a significant effect on the load of wind turbines. These severe weather phenomena are closely related to atmospheric stability. Therefore, the objective of this study is to determine differences in wind resource characteristics in the South Korean offshore and coast in relation to variations in atmospheric stability using observation data from the HeMOSU-1 meteorological tower in the West Sea and the Boseong meteorological observation tower on the southern coast. On the southern coast, changes in sea and land breezes are observed throughout diurnal and nocturnal periods, with an atmospheric stability distribution similar to that of land, which is unstable during the day and becomes more stable at night. On the other hand, the stable ratio continues to dominate in the west offshore. In the case of coastal areas, low-level wind shear occasionally occurs near the general wind turbine hub height approximately over 100 m due to the influence of winds from the sea. This study shows that when constructing an offshore wind farm, it is necessary to first analyze the characteristics of local coastal and offshore wind resources for more efficient and safe wind farm construction and operation.

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Section: Monin-obukhov Lengthmentioning

confidence: 99%

Atmospheric Stability Effects on Offshore and Coastal Wind Resource Characteristics in South Korea for Developing Offshore Wind Farms

Ryu

Kim²,

Kwak

et al. 2022

Energies

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“…However, when atmospheric stability is near-neutral or weakly stable, or for small and medium-sized wind turbines with a rotor disk diameter of less than 50 m, this is a suitable method. As wind turbines have recently become super-sized, the rotor equivalent wind speed is recommended, which can take into account the effect of changes in kinetic energy on power generation [21,22]. This is a principle that considers wind speed at various heights passing through the rotor disk area by horizontally multiple divisions, as shown in Figure 2.…”

Section: Rotor Equivalent Wind Speedmentioning

confidence: 99%

“…As the capacity and scale of wind turbines increase, accurate measurement of power curves, and the calculation of expected power generation are required, and conflicting interests arise in that regard [19,20]. Traditionally, to calculate the expected power generation of a wind turbine, only the wind speed at a single height corresponding to the hub height is considered, under the assumption that atmospheric stability is in a near-neutral state [21][22][23]. This was proper in the past to apply to small wind turbines with short blade lengths, and in calm offshore or flat land without obstacles, the difference in wind speed by height is small.…”

Section: Introductionmentioning

confidence: 99%

“…This was proper in the past to apply to small wind turbines with short blade lengths, and in calm offshore or flat land without obstacles, the difference in wind speed by height is small. So even if the expected power generation was calculated by selecting the hub height wind speed as the representative wind speed within the rotor disk, the error compared with the actual power generation was not large [21,22]. However, in recent years, as the diameter of the rotor area of the wind turbine has exceeded 200 m, the hub height wind speed cannot be the representative value in complex terrain, such as mountains, or even in flat terrain, where wind speed fluctuations by height occur in short time, due to the meteorological characteristics within the local atmospheric boundary layer.…”

Section: Introductionmentioning

confidence: 99%

“…The IEC Technical Committee 88 (TC88) recognizes that if the wind shear coefficient is kept constant, the difference between the rotor equivalent wind speed and the hub height wind speed is generally small [24]. However, in special cases, the vertical wind speed profile cannot be sufficiently explained by a constant wind shear coefficient, and such cases may be influenced by local meteorological characteristics or atmospheric stability distribution [12,21,22]. In this case, it is necessary to recognize that the difference between the rotor equivalent wind speed and the hub height wind speed may be considerable.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of Vertical Wind Shear Effects on Offshore Wind Energy Prediction Accuracy Applying Rotor Equivalent Wind Speed and the Relationship with Atmospheric Stability

Ryu

Kim

et al. 2022

Applied Sciences

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If the wind speed that passed through a wind turbine rotor disk area is constant, the hub height wind speed (HHWS) could be representative of the wind speed over the rotor disk area. However, this assumption cannot be applied to the large wind turbine, because of the wind shear effect by atmospheric stability. This is because the hub height wind speed cannot represent the vertical wind shear effect from the aerodynamics characteristic on the wind turbine. Using SCADA and offshore LiDAR observation data of the Anholt offshore wind farm, it is investigated whether the rotor equivalent wind speed (REWS) introduced in IEC61400-12-1 can contribute to the improvement of power output forecasting accuracy. The weighted value by separated sector area and vertical wind shear effect by difference between heights can explain the role of energy flux and atmospheric stability on the exact wind energy calculation. The commercial CFD model WindSim is used to calculate power production according to the HHWS and the REWS, and to compare them with the actual AEP of the local wind farm. The classification of atmospheric stability is carried out by Richardson number, which well represents the thermal and physical properties of the atmosphere below the atmospheric boundary layer, along with the wind shear coefficient and turbulence intensity. When atmospheric stability was classified by each stability index, the REWS-based predicted power output was sometimes more accurate than HHWS, but sometimes inferior. However, in most cases, using the REWS, it was possible to calculate an estimate closer to the actual power output. Through the results of this study, it is possible to provide a rationale for which method, REWS or HHWS, can more accurately calculate the expected power output and effectively derive the economic feasibility of the project by identifying the characteristics of local atmospheric stability before the wind farm project.

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Influence of Vertical Wind Shear on the Annual Energy Production of a Coastal Region in Northeastern Brazil

Martins,

Oliveira,

Pimenta

et al. 2023

2023 Workshop on Communication Networks and Power Systems (WCNPS)

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Accounting for the Atmospheric Stability in Wind Resource Variations and Its Impacts on the Power Generation by Concentric Equivalent Wind Speed

Cited by 4 publications

References 11 publications

Atmospheric Stability Effects on Offshore and Coastal Wind Resource Characteristics in South Korea for Developing Offshore Wind Farms

Atmospheric Stability Effects on Offshore and Coastal Wind Resource Characteristics in South Korea for Developing Offshore Wind Farms

Analysis of Vertical Wind Shear Effects on Offshore Wind Energy Prediction Accuracy Applying Rotor Equivalent Wind Speed and the Relationship with Atmospheric Stability

Influence of Vertical Wind Shear on the Annual Energy Production of a Coastal Region in Northeastern Brazil

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