Finite element modeling of a 40 m lattice wind turbine tower

The U.S. Department of Energy report titled "20% Wind Energy by 2030" initiated the investigation of taller wind turbines. With the increasing height of the wind turbines the tubular wind turbine tower design has issues with the base diameter for transportation from manufacture to installation site. Highway infrastructure in the U.S. has motivated the wind energy industry to investigate an alternative design; the lattice design is one such solution. One company designed a lattice tower that utilizes interference between the bolt and clamped components. To study the dynamics of this tower an intensive model was created using beam, shell, and solid finite elements. The model utilized simplifications of the various components; simulations were performed to verify the requirements of the said simplifications. Experimental results indicated that the model could utilize a fixed boundary condition; however, the resulting frequencies for the first two modes were unacceptable. In order to investigate the cause of this error, the soil surrounding the tower was modeled using a relatively large linear solid continuum to simulate an elastic boundary. The addition of the solid continuum greatly improved the results; resulting in a maximum frequency difference of -7% and mode shapes for the experiment and model follow the same trend.