Blades for wind turbines

Intelligent blade monitoring
LM Glasfiber works continuously to optimise our blades, and not just in the design stage. We have therefore developed LM BladeMonitoring, a system that optimises the blades' operations, even after they have left our factories. As yet, LM BladeMonitoring only exists as a prototype, and is currently undergoing site tests on two wind turbines.

This blade monitoring system uses specially developed software and optical fibres placed within the blade's laminate. LM BladeMonitoring registers critical conditions such as loading, temperature and lightning, and can either download this information to the turbine's computerised control system or transfer the data via a wireless connection to a control centre or a service technician's computer.

Blade monitoring has great potential, both with regard to increased production and optimised service and maintenance.

Individual pitch
Utilising the process signals from LM BladeMonitoring directly in the turbine's control system enables individual pitching of the blades and thus increased production and optimum control of the loads during operation. A blade that is upright and away from the shadowing effects of the tower is exposed to quite different loads from a blade that is pointing downwards.

By individually pitching the blades, it is possible to minimise the blade flap fatigue loads by 15-30% and the fatigue loads on the yaw mechanism and tower construction by 10-30%. As a result, the same turbines can be fitted with larger blades, which in turn increases energy production.

Integrated testing
Reliability down to the tiniest detail
LM Glasfiber's material mechanics experts are always on the lookout for details that will help us improve our blade designs. It's only by being completely familiar with the outer limits of these materials' capabilities - and then stretching the envelope all the time - that we can ensure that each blade is reliable, durable and cost-effective. And do so without using more than is really needed, and without using materials that are more expensive than really necessary.

Microscopic examination
It's often the small details that lead to major technology breakthroughs. That's why we examine the microstructure of the materials we use in the lab, as part of our analysis of their overall properties. This helps reveal how these materials will perform when used in large-scale composite structures, paving the way to achieving the best possible quality.

To study these properties, we produce a special test model, which then undergoes a range of different tests. Part of these involves a special pull-and-push testing machine that uses computer-controlled servo-hydraulics to test the strength and stiffness of a particular material. The test unit is then inspected under a microscope. Any signs of damage always make their first appearance in the microstructure.

Different combinations of glass fibre and resin, under different process conditions, result in a wide range of different properties and strengths. The combination of testing and examination under a microscope enables us to map these in great detail so that we can adjust the properties of each laminate to any specific requirement, at the same time as making sure that any potential weaknesses are eliminated.

Breaking strength of boundary areas
Boundary areas, such as glued joints and interfaces between laminates and the core material, have a critical influence on the overall structural strength of a wind turbine blade. LM Glasfiber has worked with the Risø National Laboratory in Denmark to develop a method for testing mechanical breaking strength. This introduces different loadings using force moments, which makes it possible to apply well-defined loads in several different axes at once. These correspond to the forces that act on the blade while in real-life operation. These test procedures are carried out in our own specially developed mixed-mode test machine.

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