<p>Along with the rapid expansion of wind power in Sweden during the last decades the competition about favorable areas has hardened. This among other reasons has caused the projectors to look into development of wind power in forests. There are several aspects regarding fatigue loads on the constructions that are severe in complex terrain, among which turbulence is one. The levels of turbulence which are accepted in order for the turbines to face a life length exceeding 20 years are regulated by the International Electrotechnical Commission, (IEC). In order to keep the turbulence below these levels there are three major steering tools to use: The ambient turbulence decreases with height and can therefore be regulated by the hub height of the turbines. The wake-induced turbulence differs with the mutual placement of the turbines and is regulated by the layout of the park. One can also choose a turbine which is of a higher class regarding turbulence. The aim of this Master´s Degree Project is to investigate how these tools can be combined in order to keep the turbulence levels below the recommendations from IEC. The results are then to be applied to Wallenstams planned park in Skuggetorp. The results from the investigation are that the turbulence levels in forests generally are too high, even with sparse layouts and high towers. The problem is increasingly severe in large parks where the need for large separations between the turbines is evident. There is no use in increasing the separation along the dominant wind direction. The examination of Skuggetorp gives incentive to keep the distance between the turbines over 6 rotor diameters in all directions. The recommendations are to build the towers as high as technical and economical aspects can allow. The turbines should preferably be of IEC class A. There are no large wind power farms in forests that are running in Sweden at present, and the Swedish conditions cannot be compared with terrains in other countries. Whether or not wind turbines that are placed in high turbulence areas will survive for 20 years is a question to be answered in 20 years from now.</p>

Along with the rapid expansion of wind power in Sweden during the last decades the competition about favorable areas has hardened. This among other reasons has caused the projectors to look into development of wind power in forests. There are several aspects regarding fatigue loads on the constructions that are severe in complex terrain, among which turbulence is one. The levels of turbulence which are accepted in order for the turbines to face a life length exceeding 20 years are regulated by the International Electrotechnical Commission, (IEC). In order to keep the turbulence below these levels there are three major steering tools to use: The ambient turbulence decreases with height and can therefore be regulated by the hub height of the turbines. The wake-induced turbulence differs with the mutual placement of the turbines and is regulated by the layout of the park. One can also choose a turbine which is of a higher class regarding turbulence. The aim of this Master´s Degree Project is to investigate how these tools can be combined in order to keep the turbulence levels below the recommendations from IEC. The results are then to be applied to Wallenstams planned park in Skuggetorp. The results from the investigation are that the turbulence levels in forests generally are too high, even with sparse layouts and high towers. The problem is increasingly severe in large parks where the need for large separations between the turbines is evident. There is no use in increasing the separation along the dominant wind direction. The examination of Skuggetorp gives incentive to keep the distance between the turbines over 6 rotor diameters in all directions. The recommendations are to build the towers as high as technical and economical aspects can allow. The turbines should preferably be of IEC class A. There are no large wind power farms in forests that are running in Sweden at present, and the Swedish conditions cannot be compared with terrains in other countries. Whether or not wind turbines that are placed in high turbulence areas will survive for 20 years is a question to be answered in 20 years from now.