THE blades of wind turbines are by far the main factor in the development of high-performance machines to make the most of this sustainable energy resource.

Researchers at the University of Nottingham, England, are playing an important role in an international project to develop more efficient, less wasteful methods of constructing blades with the correct aerodynamic and structural characteristics.

At present, blade manufacture is the "bottle-neck" in wind turbine production. Slow production methods mean that blades are not being made quickly enough to satisfy the demands of the fast-growing wind energy industry. Existing processes are also labour intensive - that can lead to human error - and result in appreciable levels of waste.

The Polymer Composites Group in Nottingham's Faculty of Engineering is looking at how aerospace technology can be adapted to improve wind turbine blade manufacturing methods.

The team is are working alongside aerospace, composites and wind energy experts - from companies such as Gamesa, BAE Systems and Hexcel Composites - in the three-year Airpower project (short for affordable innovative rapid production of offshore wind energy rotor-blades) funded by the Technology Strategy Board.

The Nottingham team discovered that, by using automated tape laying technology to lay composite materials in blade construction, there could be an eight-per-cent cost saving per blade.

This could equate to an annual saving of 2.3 million pounds for a wind turbine factory. In addition, the use of high-stiffness fibres helps engineers to optimise performance characteristics of large-scale blades and also to expand the range of useable wind speeds.

As part of the project the researchers are investigating how fibre-optic sensors can be used to monitor residual strain levels in the blades during production.

Team leader Dr Peter Schubel said: "This project is unique in terms of the university's links with the wind energy industry. We are the only British university to work with Gamesa, one of the world's largest wind-energy companies. The project will not only improve the construction process, it will allow us to monitor how these materials change during production."

"Integrating pioneering structural monitoring solutions to gauge micromechanical strains created during the laminate curing process should lead to the development of more efficient processing conditions," he added.

Benefits may also extend to the use of a similar system to provide structural health monitoring of blades during their service life.

The Airpower project is developing a seven-metre section of a turbine blade to be used as a demonstrator to showcase the developed automated tape laying and fibre-optic technology.

Plans are also in place to build a 15m-high test turbine at the university's Sutton Bonington agricultural site this year. Research into new blade shapes, turbine designs and electronics will be tested on the equipment.

"The test turbine isn't full size," added Dr Schubel. "But all of the test designs will scale up to the real thing."

Image caption: Air craft: international engineers at Nottingham University examine how aerospace technology could improve wind turbine blade manufacturing methods. Clockwise: Dr Peter Schubel (top left), Richard Crossley, Darshil Shah, Eric Boateng, Joel Hutchinson GRN_13677 Image by Dr Peter Schubel