Figure 28 Wind turbine towers, courtesy of GE Vernova.
Function
The tower is typically a tubular steel structure that supports the nacelle. It also provides access to the nacelle and houses electrical and control equipment. Also provides shelter and storage for safety equipment.
What it costs*
The tower cost for a 15 MW wind turbine is about £1.4 million.
Who supplies them
CS Wind, Gestamp Renewable Industries, Global Energy Group, GSG Towers, Haizea Wind Group, Hutchinson, Titan Wind Energy and Welcon.
Fasteners: Cooper & Turner
Polymer solutions: Nylacast
Key facts
Fabricators manufacture towers to designs provided by wind turbine suppliers, sometimes using free-issue materials (both steel and internal components).
Towers are normally made at coastal locations to avoid road transport .
Once fabricated, the tower sections are shot-blasted and painted before fit-out with other internal components then prepared for transport and storage.
The hub height is about 135 m above mean sea level minimum depending on the rotor diameter, so each tower is about 120 m high and has a mass over 800 t.t. About 90% of the mass is steel plate with forged steel flanges making up most of the rest.
Towers are generally tapered, with a top diameter of about 6 m and a base diameter of about 10 m for a 15 MW turbine. Design is driven by fatigue and extreme loading plus natural frequency requirements and avoidance of bucking.
The optimum tower height is normally as low as needed to comply with maritime safety regulations for blade clearance above the water. This is because the wind shear is low offshore (the wind speed does not increase very much with increasing the hub height), meaning there is no cost benefit for using a taller tower. The tower height to achieve blade clearance needs to take account of the tidal range. Permitting at some sites has required taller towers to reduce the risk of bird strikes.
Integrated design of substructures and towers is increasingly seen as desirable with the transition from substructure to tower predicted to be less distinct. The tower, though, continues to be a discrete component supplied with the wind turbine.