We investigate the capability of wind farms to track a power reference signal to help ensure reliable power grid operations. The wind farm controller is based on a simple dynamic wind farm model and tested using high-fidelity simulations. We find that the dynamic nature of the wind farm model is vital for tracking the power signal, and the controlled wind farm would pass industry performance tests in most cases.

A model for quick load analysis is presented. This is a fast model for the calculation of dynamic loads of an offshore wind turbine tower and foundation. The model is compared to the state-of-the-art aeroelastic code. In general, there is good similarity between the two models. This indicates that in the early stage of the design phase a simple dynamic model can be used to make a preliminary design of the foundation and wind turbine tower.

Current fast aeroelastic wind turbine codes suitable for certification lack an induction model for standstill conditions. A near-wake model for wind turbines in operation is extended to cover these conditions. The model is validated in aerodynamic simulations of the NREL/NASA Ames Phase VI rotor. Good agreement with the experiments has been obtained in attached flow and beginning separation. Aeroelastic simulations of the DTU 10 MW turbine in standstill indicate a minor impact of the model.

The wakes of wind turbines cause losses in the energy production of a wind farm. The accuracy of models applied to predict wake losses is a key factor for new wind projects. This paper presents an engineering wake model that can simulate merging wakes on the basis of physical principles. We used high-fidelity simulations of merging wakes to assess this model and found a better agreement with the reference than commonly used models implementing the superposition of individual wakes.

Stability classification is usually based on measurements from met masts, buoys or lidars. The objective of this paper is to find a classification for stability based on wind turbine supervisory control and data acquisition measurements in order to fit engineering wake models better to the current ambient conditions. The proposed signal is very sensitive to increased turbulence. It allows us to distinguish between conditions with different magnitudes of wake effects.

The majority of the wind turbine market is focused on large pitch-regulated machines, but small stall-regulated are still attractive because of their simplicity and robustness. This work focuses on aerodynamic section design for these machines and its impact on overall performance. The big challenge faced was that, beside the need to maximise the energy produced, the control of the machine depends on the section design. The results, however, showed a large performance gain and machine control.

This work provides a possible solution to closed-loop flow control in a wind farm. The remote sensing technology, lidar, which is a laser-based measurement system, is used to obtain wind speed information behind a wind turbine. The measurements are processed using a model-based approach to estimate position information of the wake. The information is then used in a controller to redirect the wake to the desired position. Altogether, the concept aims to increase the power output of a wind farm.

We conducted measurements in a wind tunnel with the remote sensing technique lidar to map the flow around a row of three model wind turbines. Two lidars were positioned near the wind tunnel walls to measure the two-dimensional wind vector over a defined scanning line or area without influencing the flow itself. A comparison of the lidar measurements with a hot-wire probe and a thorough uncertainty analysis confirmed the usefulness of lidar technology for such flow measurements in a wind tunnel.

Vertical axis wind turbines (VAWTs) operate through inherently unsteady aerodynamics, unlike their horizontal axis counterparts (HAWTs). This greatly affects the structure of the wake, i.e., the region of velocity deficit and increased turbulence downstream of the machine. In this work, we use an advanced vortex method to identify the flow structures and instabilities at work in the decay of a VAWT wake, a crucial step if one wishes to optimize this decay or perform the design of VAWT farms.

Actuator disc theory is the basis of most rotor design methods. However, the off-design condition of a very low rotational speed Ω is still a topic for scientific discussions. A small modification in the momentum theory for Joukowsky discs with uniform circulation results in the efficiency going to 0 instead of ∞ when Ω goes to 0. For high values of Ω, the classical momentum theory is reproduced. The new theory is confirmed by a very good match with numerically obtained results.

In the paper, rotor stability in slow idling operation is assessed on the basis of nonlinear time domain and linear eigenvalue analyses. A consistent and computationally cost effective modeling environment has been presented for the analysis of parked or idling rotors. The analysis shows that the lowest damped modes of a 10 MW idling rotor are out-of-plane modes (symmetric and asymmetric).

Floating platform wind turbines present a challenge for engineers to simulate. This paper explores some better methods for simulating the aerodynamics of wind turbines as they move about on a floating platform. We also derived a new way of investigating whether the aerodynamics of the wind turbine rotor help it stay stable.

This paper presents the idea of centralized electricity production in a wind farm by means of water technology. A new way of generating and transmitting wind energy is explored with no intermediate electrical conversion until the energy has reached the central offshore platform. This work includes the modelling and simulations of a hypothetical hydraulic wind farm, where results indicate good performance despite the turbulent wind conditions and wake effects.

Trailing edge flaps applied to the outer part of a wind turbine rotor blade are a very promising concept to reduce fatigue loads as they are able to increase or decrease the airfoil lift for a given angle of attack. They have been widely researched on 2-D airfoils, but only little is known about their aerodynamic characteristics on 3-D wind turbine rotor blades. The present article addresses this issue.

In recent years, wind farms have grown in size and are more frequently placed in wind farm clusters. This means that large-scale effects such as the interaction of the Coriolis force and wind farm wakes are becoming more important for designing energy efficient wind farms. The literature disagrees on the turning direction of a wind farm wake due to the Coriolis force. In this article, we explain why the Coriolis force turns a wind farm wake clockwise in the Northern Hemisphere.