We expect to provide knowledge on the effects of key-hole cuts and clearings in forests around windfarms, including the effects on turbulence, fatigue loads on turbines and energy production.

Further, we expect to provide general recommendations on how and where to clear forest around a wind farm, and how key-hole cuts should be designed to minimize the maintenance costs and fatigue loads on turbines.

Measurements will be performed at test site C made available by Stena Renewables. At the test site, which will include a wind farm, scanning LIDAR measurements will be performed by Meventus before and after the tree felling. Chalmers will carry out advanced CFD simulations of the site coupled to energy production and load predictions. Simuiation of the windfarm of Oberga Vind AB will also be performed. Vestas will contribute with their expertise.

WP 1: CFD Simulations Wind field simulations will be performed in two stages. In the first stage (Stage I), test case C will be simulated, before and after tree felling, making use of the measurements to verify the models. The second phase aims to find the optimal size and shape of clearings and key whole cuts by simulating hypothetical cases.

I Simulations, using SOWFA, of the wind flow field will be performed before and after tree felling at test site C. The predicted flow field before and after the clearing around the wind farm will be compared with the LIDAR measurements made in WP2. The predicted fatigue forces, obtained by FAST, with and without clearing will be evaluated and compared. SCADA data from the turbines collected in WP2 will also be used as a source for verification of the models and to evaluate the production effects.

Simulations of the windpower stations of Oberga Vind AB will be carried out before and after tree felling. The predicted energy production and loads will be compared with existing SCADA data.

II Simulations of hypothetical clearings with different sizes and shapes will be performed with SOWFA. The predicted fatigue forces (obtained by FAST) with and without clearing will be evaluated and compared. The aim is to find recommendations on how large clearings should be in order to make a balance between high production and minimal maintenance cost.

WP 2: Experiments A test site (denoted test site C) in forested terrain with an existing windfarm and planned tree felling will be made available for measurements and modelling by Stena Renewables. A wind measurement campaign with a scanning LIDAR will be performed before (spring 2018) and after the tree felling (spring 2019). The measurement campaign will be designed to be used as verification of the wind flow simulations. SCADA data from the turbines before and after the forest clearing will also be collected and analysed to see the effects on production and fatigue loads.

Since open-source software (SOWFA and FAST) is used in the project, the simulations tools will be made available for the Swedish Windpower industry and the Swedish universities.

1. Matsfelt, J.
   "Large Eddy Simulation of clearings in forest and their effect on wind turbines", thesis of Lic. of Engng, Division of Fluid Dynamics, Dept. of Mechanics and Maritime Sciences, Chalmers University of Technology, Göteborg, Sweden, 2018.
   View PDF file of thesis
    
   
2. J. Matsfelt and L. Davidson
   Large-eddy simulation study of effects of clearing in forest on wind turbines, 6th Symposium on OpenFOAM in Wind Energy, June 13th-14th, 2018, Visby, Sweden
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3. J. Matsfelt, L. Davidson, K.. Brennan
   "Influence of complex terrain on a flow above a forest with clearing", Journal of Physics: Conference Series 17426588 (ISSN) 17426596 (eISSN), 2020.
   View PDF file
    
   
4. J. Matsfelt and L. Davidson
   "Large eddy simulation: A study of clearings in forest and their effect on wind turbines", Wind Energy, DOI 10.1002/we.2637
   Get article at publisher