COMPARISON OF THE WIND POWER PRODUCTION MODELS IN THE BALTIC SEA, A CASE STUDY IN THE LILLGRUND OFFSHORE WIND FARM

Abstract: Wind energy, which is no emission of greenhouse gases, is attracting increasing attention world widely. Compared to onshore wind farms, offshore wind farms can yield greater power production since the wind speeds over the sea are higher and steadier than those over the land. An increasing number of offshore wind farms are being planned and deployed all over the global near-sea areas. Thus, accurate evaluation of wind power production is essential for offshore wind farm development. This study compares two popular models, the minimalistic prediction (MP) model and the linear WAsP model, in the modeling power production of the Lillgrund offshore wind farm in the Baltic Sea. The wind condition data from New European Wind Atlas (NEWA) is used to analyze the wind resources and as input data of the models to calculate wind power production. The calculated results are compared in different years and wind direction sections. The sensitivity of the calculated power production to different influencing factors, including the size of the wind farm and hub heights, are examined. The results show that the WAsP model generally yields higher energy production than the Minimalistic Prediction (MP) model. The requirement for wind condition data and wind farm layout parameters in those two models is different. Compared to the WAsP model, the MP model does not require detailed wind farm layout parameters and wind direction data, which leads to different power production results. From the results of sensitivity experiments, both the size of the wind farm and hub heights have an impact on power production. When the wind farm size increases by 5 times the original size, the wind power production increases by around 50 %. However, when the distances between wind turbines are large, the wake effect would disappear gradually. Therefore, the growth rate decreases with the increase in the size of the wind farm. The wind speed is higher with the increase in hub height. However, due to the smaller turbulence flux, the increase in wind power production with higher hub height is not obvious. When the hub height increased by 2.6 times, the wind speed just increased by around 13 %. It is not hard to conclude that designing a wind farm is a process full of trade-offs. Balancing the rich wind resources and the financial benefits from offshore wind farms are equally essential. Our study can contribute to the application of the models and the designing of offshore wind farm layouts in the Baltic Sea.