This conceptually innovative tower design developed by Siemens Wind Power, Andresen Towers and Tension Control Bolts Ltd provides a economically viable tower for wind turbines above 100m tall. The bolted Steel Shell Tower is suitable for towers of heights up to 140m, significantly increasing the energy yield of a wind turbine generator on sites with a high wind shear.

There are 300 towers of this design across Northern Europe primarily in Sweden, Denmark and Finland. The Bolted Steel Shell Tower consists of multiple tower sections. Each section is fabricated from steel ‘shells’ which are transported to site and then assembled together. A standard truck can be used to transport the sections in this ‘flat-pack’ design. The sections are bolted together with TCB (HRC/Tension Control Bolts) bolts to form a tower section.


  • Fast and easy installation using tension-controlled TCBs with tower erection completed within a couple of days.
  • Utilising TCBs means there are no welded connections, problems with fatigue and cracks are avoided.
  • High hub heights; virtually no restriction on the maximum hub height.
  • Low transportation requirements.
  • Minimal maintenance - In fact, the TCBs require no re-torquing during the tower’s lifetime. Research from the Fraunhofer Institute allied to the University of Rostock engineering faculty verified that Greenkote TCBs from Tension Control Bolts will not lose preload after correct installation. In simple terms the TCBs are maintenance free and will outlive the design life of the tower. These towers are almost always located in remote areas.
  • Reduced steel requirement; in contrast tubular steel towers have larger tower diameters with thicker steel material.
  • Utilises steel coils which are more cost effective than quarto steel plates.
  • Highly automated shell production ensuring consistent high quality and reduced costs.
  • Easy transportation of shells on standard trailers, in containers or by rail, facilitating access to even remote locations.
  • Fully recyclable tower at end of life.

Greenkote® anti-corrosion protection

Tension Control Bolts Ltd has its own metal coating plant producing an environmentally friendly anti-corrosion coating called Greenkote, which is comparable to galvanising, although it is harder wearing and readily accepts all paint systems. Learn more about Greenkote.