Technology developed for offshore turbines and substructures is being deployed in the construction of a telescopic tower onshore prototype in east-central China.
Spanish infrastructure firm Esteyco is putting the finishing touches to the tower, which features three concentric sections designed to slide into one another – like a telescope.
The installation in Henan province will have a hub height of 170 metres and support a 3.6MW turbine with a rotor diameter of 155 metres.
The tower combines three concrete levels – with heights ranging from 40 to 50 metres – with conventional tubular steel sections at its top.
Several concrete sections levels are cast in place at ground level.
The pieces are arranged concentrically before the auto-erecting lifting phase is launched.
Esteyco first tested its technology as an onshore prototype without a turbine near Madrid in 2018.
Building a concrete telescopic tower involves three stages:
- On-site construction of concrete sections
- Upper steel section, level, nacelle and rotor assembly
- Self-erection system, with two operation stages
In China, both the concrete construction and the installation of the steel level have been completed.
The tower is ready for the self-lifting process, which is scheduled for March 2021.
The design and construction are based on experience in building conventional precast concrete towers.
Esteyco has built more than 1,600 towers since 2004 for several turbine manufacturers with hub heights ranging from 80 metres to 120 metres.
The firm believes the telescopic tower solution is key for both off and onshore markets as demand for hub heights up to 190 metres increases.
This demand has been driven by renewable energy policies where reduction of cost of energy is crucial, the firm explained. The technology means large, costly and in-demand heavy cranes are not needed for construction.
If needed, steel tubular sections from conventional steel towers can be used in a hybrid solution to further reduce the cost of energy.
Esteyco patented solution uses heavy-lift strand jacks placed about 40-50 metres from the ground, to lift each tower section.
Guides are used with a hoist to lift sections as part of a self-installing procedure, in which the tower is the only supported structure, working from a single access platform at heights of 40-50 metres.
The technology allows for construction that is independent of expensive heavy-lift vessels.
The first fully operational prototype was completed in 2018 on Gran Canaria Island, in Spain which meant the build could avoid the use of heavy cranes or vessels.
The construction involved a self-installing, bottom-fixed offshore wind turbine which was designed, built and then certified by Esteyco.