EU Project Overcomes Obstacles in Increasing Wind Turbine Blade Size

03 October 2005

The Technical Research Centre of Finland (VTT) is currently developing a smart reinforced plastic material whose shape can be altered by an electric current.

The collaborative project, which involves 38 parties from around Europe aims to double the length of the current blade used, so that the plant's capacity can be quadrupled.

In the research project initiated by VTT, the european consortium plan to develop technologies that will make it possible to construct wind power plants of a new magnitude. VTT suggested that the initiative is the largest-ever development project in the field of European wind power technology, with an overall budget that amounts to €20 million.

The project is based on the premise that the capacity of wind power plants can be increased by using longer blades. Longer blades, however, will inevitably be subject to increased vibration stress so the structure of blades need to be made stronger without adding too much weight to them. The project aims to develop the optimisation of the blade structure using new manufacturing materials, and addressing issues of damping the vibration.

The project will seek to enhance the durability of blades by developing the ""active shape control"" where the shape of the blades is altered when the wind speed changes or the blade rotates past the tower. Active shape control increases the capacity of the wind power plant. When the vibration stress imposed on the blades is reduced, the lifting force of the blades can be kept constant in different wind speeds. This makes it possible to operate the wind power plant in stronger wind, which in turn increases the annual production time.

Most wind power plants are unoperable during periods of strong winds because their structure is unable to withstand the increased stresses imposed on them.

VTT is hoping to transform the blade shape by embedding shape memory metal wires in them. When the temperature of the wires is increased to approximately 60 degrees centigrade by means of electric current, the shape memory metal alloy transforms the blade into the desired shape, preventing unnecessary vibration and blade movement.

According to VTT, the capacity of the largest wind power plants currently amounts to 5 megawatts, with the rotor diameter being nearly 120 metres. The long-term project aims are to increase the capacity of offshore wind power plants from the current 5 megawatts to as much as 20 megawatts. Quadrupling the capacity requires doubling the blade length, which is possible by optimising the blade materials and structure and having better control over the load imposed on the wind power plant's structures.

VTT's own contribution to the project is to focus on the development of the structures and materials used in the blades of wind power plants. VTT will also direct the design and implementation of a two-meter-long scale model of a wind power plant blade.

A number of industry reports state that European companies have an 80% share of the world market of wind power plants, with the use of wind energy doubling approximately every three years. Finnish wind power technology has an annual export value of €200 million.

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