Fraunhofer Institute for Wind Energy SystemsAt a glance
- Lightning strikes on modern wind turbines can cause serious damage and result in long downtimes, as it is not currently possible to repair the pultruded CFRP spar cap planks in rotor blades in situ.
- In the CaReUp research project, the partners are developing a method allowing the repair of the spar cap planks in situ, thus reducing the turbine downtime to just a few weeks.
- Fraunhofer IWES, the project coordinator, is responsible in a subproject for developing the overall concept and validating it under realistic conditions.
The challenge
Lightning strikes represent a technical challenge for wind turbines – one that is becoming more significant as rotor blades continue to grow in size and length, thus increasing the likelihood. The blades are equipped with lightning protection systems for precisely this reason, but no system offers 100% protection. Lightning can occasionally strike outside the predicted zones or with greater force than expected, which can result in deviating current paths in the system in isolated cases. In particular in the case of modern rotor blades with additional electrically conductive elements such as CFRP spar cap planks, it is important that these protection concepts be continuously further developed, so that any issues can be quickly identified and resolved.
Conventional repair methods are reaching their limits for modern rotor blades with planks produced in a pultrusion process. As a result, damaged rotor blades have to be exchanged and repaired under laboratory conditions. This translates to long downtimes and high costs for wind farm operators.
The solution
In the CaReUp research project, the partners are thus developing a standardized, validated, and certified repair method for pultruded CFRP profiles in rotor blades in situ. To this end, all partners have designed a concept to analyze the stresses and loads to which the planks are subjected during the repair. On this basis, a temporary auxiliary structure is being developed to support the structure during the repair. Subsequent component tests will lead to final validation of the method on a full rotor blade section.
As the project coordinator, Fraunhofer IWES is responsible in a subproject for the development of the overall concept among other tasks. In addition to the determination of favorable turbine positions for the repair, this also includes the design of the support and auxiliary structures as well as the validation under realistic conditions.
The added value
The newly developed method will make it possible to perform repairs on rotor blades so efficiently that the wind turbine can enter operation again after just a few weeks. This will significantly reduce the loss of revenue and resources employed, which will translate to considerably lower costs for operators. At the same time, higher availability of wind turbines makes an important contribution to climate-friendly energy production.
