Can the Wind Turbine Transition Piece be designed to mitigate structural vibrations?

Wind turbines and their blades have rapidly been upsizing in the last decades. Current design methods, basic assumptions on the structural and soil model, and the impact of extreme natural events such as storms and earthquakes, should be re-investigated to avoid undesired shortcomings and premature failures (see e.g. Renewable Economy article).

Because of the recent development in seismic areas, we do not have enough statistical data and experience to understand the behaviour of wind turbines (and wind farms) subjected to strong earthquakes. Therefore, several researchers are now assessing the seismic reliability of next-generation wind turbines. Traditional complex solutions such as Tuned Mass Dampers and Tuned Liquid Column Dampers are currently being investigated to mitigate dynamic vibrations.

In our study, we are proposing a novel solution, called the Reduced Column Section approach, to transfer into the Wind Industry, seismic control approaches normally used for buildings, such as the reduced beam section approach, the rocking foundation and the isolation system. Therefore, we adopted this approach to derive an innovative mitigation device which can replace the traditional transition piece of the wind turbine. The proposed transition piece is featured by hourglass shape and high-strength steel to meet the following objectives:

1. Control of the fundamental period of the wind turbine and rocking-induced behaviour;

2. Increment of the plastic moment capacity.

The approach can also be used for columns of buildings, although the research is currently focused on the protection of wind turbines.

The study is the first attempt to investigate how to re-design the traditional transition piece to mitigate dynamic vibrations, with a main focus on seismic behaviour.

Analytical formulation, numerical analyses and monitoring of an existing onshore wind turbine can be found in the open-access paper " A novel reduced column section approach for the seismic protection of wind turbines" by Rohollah Rostami and Alessandro Tombari . The Authors gratefully acknowledge the contribution of the financial support of the Engineering and Physical Sciences Research Council ( EPSRC ) through the New Investigator Award EP/W001071/1 “Structural Life-Cycle Enhancement of Next-Generation Onshore and Offshore Wind Farms” and the technical support provided by the Industrial Partner Ergowind s.r.l. (Italy) for the installation of the continuous monitoring dynamic system in Sassoferrato, Italy.