Vertical wind speed profiles in atmospheric boundary layer flows

In this chapter, we elaborate on several similarity theory-based and empirical wind speed profile formulations. We highlight their strengths and weaknesses through various examples from the literature. Some of these formulations are sometimes inappropriately used in various practical applications (e.g., offshore wind resource assessments). We...

Impact Assessment of Wind Farm Blockage in Complex Terrain

Measurement campaigns and CFD simulations have recently identified a large-scale flow phenomenon called wind-farm flow blockage. This is found to bear a significant and far-reaching reduction in wind speed upstream of a wind farm. The wind farm blockage is attributed to the cumulative induction effects of multiple wind turbines placed in series....

Detecting nighttime inversions in the interior of a Douglas fir canopy

Despite the importance of forests in the water and carbon cycles, accurately measuring their contribution remains challenging, especially at night. During clear-sky nights current models and theories fail, as non-turbulent flows and spatial heterogeneity become more important. One of the standing issues is the ‘decoupling’ of the air masses...

The impact of atmospheric stability on the global blockage effect of offshore wind farms

This thesis research is set up to increase the knowledge on the influence of atmospheric stability on the Global Blockage Effect (GBE) of offshore wind farm flows, thereby aiming to improve the accuracy of energy yield calculations and predictions of offshore wind farms.

Atmospheric Stability Effects on a Spar-Type Floating Wind Turbine

Simulations of a spar-type floating wind turbine supporting the DTU 10 MW reference turbine under fitted atmospheric conditions are performed. Atmospheric conditions are modelled using the turbulent models recommended by the IEC: the Mann model and the IEC Kaimal and exponential coherence model. Model parameters are fitted to measurements at the...

The effects of atmospheric stability on wind farm layout optimization

The power production of downstream wind turbines in a wind farm is significantly impacted by wake effects of upstream turbines. Improving the layout optimization process could reduce these wake losses and therefore result in more efficient wind farms. The wakes are also affected by atmospheric stability conditions, as stable conditions lead to a...

Dutch Offshore Wind Atlas applications for wind energy purposes

The installed offshore wind energy capacity in Europe has been increasing rapidly over the past years, this trend is expected to continue thanks to the European green deal. In order to meet the future energy demand, new wind energy solutions such as increasing wind turbine size but also floating structures are being developed. This means that...

Site-specific validation of turbulence models on large offshore wind farms for improving fatigue assessment

Wind turbines installed in a wind farm are typically subject to increased turbulence because they are in the wake of upstream wind turbines that generate additional turbulence. Accurate prediction of turbulence in wind farms is critical as it is proportional to wind turbine fatigue loads, power losses and prediction of wind farm lifetime. IEC...

Evaluation of a wind farm parameterization in an operational mesoscale model

In the coming decade, the Dutch government plans to broadly expand its wind farm real estate over the North Sea region. This is a significant undertaking because, from literature, it is understood that wind turbines can affect the local environment. These impacts include, but are not limited to, changes in variables such as wind speed and...

The Illusion of Power Curves: Understanding TI, Shear, and Atmospheric Stability in Power Performance

Power curves are a fundamental element of any wind resource assessment. These are required to estimate how much energy a wind turbine will convert. The theoretical power curves are validated with measurements in test sites, however they may not be fully applicable in different wind climates as they are dependent on the site where, and the...

Atmospheric stability and wind profile climatology over the North Sea: Case study at Egmond aan Zee

The statistics of atmospheric stability and non-dimensional wind profiles are studied using the standard surface-layer theory at Egmond aan Zee in the North Sea. Measurements at 21, 70 and 116 m are used to validate the theoretical profiles. Charnock’s relation is used to estimate the sea surface roughness. Bulk Richardson number is used to...