Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Composite material wind turbine tower

Within the MEGAWIND project on-site manufactured towers, featuring composite material shells and concrete or other core materials are introduced for application in the wind energy sector. The design and development of an alternative wind turbine tower allowing for on-site manufacturing of the tower involved research on materials and large-scale structural tests on representative subassemblies of the tower. Composite material parts of the tower structure offer the potential of being transported to the site in low weight, small volume pre-forms and assembled on site, thus reducing the transportation costs.

Whereas standard concrete and steel towers offer competitive prices in standard erection sites this is not generally the case in isolated locations or in water depths of over 10 metres. New structural solutions are possible by using advanced composite materials technology that may offer cheaper whole-life solutions by increasing the net area of commercially viable wind sites and prolong the life, or reduce the maintenance cost, of the wind generator superstructure. It is expected that a tower made from composite materials will have a number of advantages over a standard steel tower: lower maintenance costs, improved dynamic damping characteristics, extended fatigue life, reduced logistic costs for installation and, potentially, the capacity to improve on some aspects of environmental (landscape) pollution. The aim was to provide an alternative to the existing steel or concrete designs particularly where the site and accessibility conditions are difficult.

The construction and manufacturing methodology aims to reduce the logistic burden (heavy cranes and ancillary equipment), usually incurred when erecting towers made up of large monolithic elements, by using light weight composite formwork segments that can be assembled on site. The innovative use of composite materials is also of interest for offshore applications. In this case the advantages are those qualities that are afforded by the low chemical inertness of fibre-reinforced composites in saline environments, as well as the reduced logistic and transportation costs. Although the tower design revolved around a land-based tower, the advantages show that such constructions may offer new structural solutions for offshore platforms in waters over 10 metres in depth.

Different manufacturing solutions have been pursued during the course of the MEGAWIND project, in order to discern the optimum one. From the initial design concepts the design group defined a preliminary design, part of which was tested at component level for structural verification. The design approach to such a composite structure is based on the critical interaction between the design and the manufacturing process. Moreover, the tower design and its construction procedure address the key issues relating to the erection of large wind turbines in isolated locations: logistics of construction, long term maintenance and motivate the potential for tower self-erection.

The group comprising structural expert organisations, a construction company and a materials testing research laboratory, elaborated the conceptual design of the main structural elements of the tower and provided tower design, based on the use of fibre-reinforced composites. The dynamic and structural performance of the tower was initially verified by numerical simulation. In addition to this, large-scale structural tests on representative subassemblies of the tower design were carried out before the approval of the final construction. Eventually, the group gave extra emphasis on the optimisation of the composite lamination sub-element joining as well as the manufacturing process.

The final wind turbine tower design was conducted according to the IEC 61400-1 standard using state-of-the-art tools, extensively validated in complex terrain applications. A 40m height composite material tower was manufactured and the performance of the prototype was evaluated through systematic laboratory testing. Test results will be used for the design assessment of tower.

The introduction of new materials and design options in the wind turbine tower industry is expected to impose favourable socio-economic impacts in Europe by enhancing industry competitiveness, supporting employment and promoting social cohesion by the regional industrial development.

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