Challenges for tower structures of modern wind turbines

Wind energy is already significant and will become even more important among the renewable energies in the future. The development of modern wind turbines provides new challenges for tower structures. Modern wind turbines are designed for a service life time of 20 to 25 years and the whole turbine has to withstand high dynamic loads. Typical tower heights of modern wind turbines are between 100 m and 160 m. The towers are usually made of steel. However, hybrid towers are also common for high towers. This paper focuses on recent developments and future trends of the design of tower structures for modern wind turbines. Firstly, steel and hybrid tower concepts of modern wind turbines are presented. Then, challenges of modern wind turbines are described; particularly the behaviour of concrete under fatigue loading. Furthermore, possible cases of damage of tower structures are presented.