A 34 m long wind turbine blade being tested at Risø DTU.
A 34 m long wind turbine blade being tested at Risø DTU.

By Renewable Energy Focus staff

Traditionally loads have been applied to wind turbine blades by casting a clamp around the blade and then subject the clamp to vertical and horizontal pulling. This, however, does not reproduce actual loads experienced by wind turbine blades in operation.

“The new test method is based on more realistic loads being applied to the blade where we rotate/turn the blade and subsequently apply a combined pull to the edge and the flap. In this way, loads are also applied to, e.g. the glued joint between the shells, which is one of the known critical areas in the blade structure,” says Find Møholt Jensen, head of the project.

The new test method involves mounting steel anchor plates directly on the wind turbine blades, allowing deformation and tilting of the blades when subjected to pulls.

“During the project, we developed two new measuring methods. The first involves using an optical digital system to accurately determine even the slightest blade deformation. By making an area of randomly placed spots, you can subsequently compare the images from the two cameras filming the blade during load testing and see whether the spots have been displaced and in which direction. The other method uses acoustic emission to measure deformation and can thus help prevent fatal blade cracks during the actual test,” Møholt Jensen says.

“With a combination of wind turbine owners, manufacturers, test centres, accreditation companies, equipment suppliers, measuring equipment experts and the experience of the aircraft and helicopter industry, there are high expectations of the new three-year research, development and demonstration project,” he concludes.

The 10 external partners of the wind turbine blade testing project are: