Polymeric concrete for wind generator towers or other large structural applicatons

Abstract

The present invention relates to towers for wind generators or other large structural applications and uses a new construction concept, based on polymeric concrete. Polymeric concrete is composed of thermosetting resin and aggregates such as sand or gravel. Polymeric concrete has low maintenance costs and exceptional high resistance to corrosion, thus justifying its main usage in non-structural applications. Additionally, polymeric concrete has been used as mortar in the rehabilitation of civil structures, especially retrofitting of bridges and heritage buildings. Its advantages for these applications are the adherence to the traditional materials, higher compressive strength than traditional concrete and low specific weight. The tower (1), according to the invention, is built of two or more superimposed ring sections (2) in conical or cylindrical shape, each ring (2) being built of one or more shell segments and the said segments being fixed by means of mechanical and / or chemical couplings, and being made of prefabricated polymeric concrete.

Description

TECHNICAL DOMAIN[0001]The present invention relates to towers for wind generators or other large structural applications and applies a new construction concept, based on polymeric concrete.STATE OF THE ART[0002]Wind generators have gained wide acceptance as an alternative source for the production of renewable and clean energy. In recent years, state of the art wind energy converters had a dramatic development in energy output / production, by using longer blades and more powerful generators. Rotor diameter of state of the art units has reached 120 m and generator power has reached 5 MW. Wind generators are supported to a convenient height by towers, in order to expose them to a convenient wind flow and prevent interaction between the rotor blades and the ground. The towers themselves are adequately attached to the foundations. The development trend described above requires increased hub height, and tower height for the same state of the art unit has reached 120 m.[0003]These towers m...

AI Technical Summary

Benefits of technology

[0011]The present invention provides a solution for building large scale towers, including towers beyond 80 m height, reducing substantially the maintenance needs, avoiding the logistics restrictions of the maximum transportable diameter and reducing the production costs of the current state of the art steel tower solutions, through the application of polymeric concrete.

[0012]Polymeric concrete is composed of thermosetting resin and aggregates such as sand or gravel. Polymeric concrete has low maintenance costs and exceptional high resistance to corrosion, justifying its main usage in non-structural applications and in small size parts where corrosion is the main problem. Complementary, polymeric concrete has been increasingly used in recent years in the rehabilitation of civil structures, especially retrofitting of bridges and heritage buildings using polymeric mortar. Its advantages for these applications are the adherence to the traditional materials, a compressive strength higher than traditional concrete and low specific weight.

[0013]Ongoing research has shown that an adequate amount of aggregates such as dry sands with a fine grain and gravel, with proper sizes, combined with low viscosity resin, can provide very good adhesion and compression properties preserving the other advantages of polymeric concrete. The nature of polymeric concrete allows adequate reinforcement through addition of fibre reinforced plastic materials or steel, thus complementing its mechanical properties, namely flexure strength. Thus, polymeric concrete can be successfully employed as a basis material on its own for large structures. Applied to towers for wind generators and other structural applications, the casting process of polymeric concrete allows plasticity in form modelling in a very cost-effective way, thus allowing adaptation and optimization of the structural design to loads and logistic restraints, while contributing with its chemical properties to reduce maintenance costs.

[0014]Towers for large structural applications typically have a base diameter of more than 4 m and reach heights above 50 m, supporting heavy loads. Examples of towers for large structural applications are towers for windmills, lighthouses or pillars supporting highways in viaducts. For all of these polymeric concrete can be used as the base material, presenting advantages in lower maintenance and in lower logistics and production costs.

Problems solved by technology

However, as increased tower height implies bolder dimensioning of the tower diameter, of the wall thickness, or both, in order to assure the necessary stiffness, this solution has met increasing limitations due to materials costs and also manufacture and transport limitations due to dimensions, as a diameter of 4.2 m is the maximum allowed in many roads due to over-crossings.

Lattice towers need more ground space and imply more time consumption for on site assembly.

They also have increased inspection and maintenance costs.

A variant hybrid construction, made of a lower section of steel lattice and an upper section of steel wall, has been proposed as in DE 103 39 438 A1, but it requires expensive joints.

Hybrid variants with a concrete lower section, as in WO 2005 / 015013, improve the load-bearing capacity and easiness of attachment to the foundation, thus allowing higher towers, but they present increased costs and fail to solve the maintenance issues.

Furthermore, all the steel wall and lattice solutions require maintenance of the tower during the project lifetime of the wind generator, due to corrosion.

Although corrosion usually appears late in the 20 year life-cycle of the on-shore tower, control and maintenance of corrosion spots on the external wall or in lattice construction entail important costs and risks.

In more aggressive environmental conditions, such as off-shore towers, corrosion becomes an even more important concern and implies increased maintenance costs and risks.

However, this solution is considerably heavier than the one of steel wall, with corresponding higher logistic costs and longer on-site assembly time.

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