Finding applications for end-of-life wind turbine blade materials based on their acoustic properties

Abstract

Current wind turbine blades are made from a material that is difficult to recycle, while a lot of them are being decommissioned. A large influx of high-performance and high embodied energy wind turbine waste material (WTBM) is forming. Next to structural applications, very few novel applications that make proper use of the excellent material properties of decommissioned WTBM are known.

To identify novel applications for WTBM sourced from decommissioned wind turbines a focus on the acoustic properties of WTBM was taken. Various strategies including a variation on material driven design, i.e. circular application through selection strategies (CATSS), were used to identify applications. For that, relevant acoustic WTBM properties were determined to properly identify a knowledge gap. To evaluate the applications identified through CATSS, experiments were set up in the anechoic chamber of the Applied Sciences faculty of the Delft Technical University. The data generated from these experiments, together with the knowledge gained during earlier parts of the project were used for concept ideation of an acoustic application. Sitka Spruce, a natural tone wood used for making tone boards in acoustic instruments, has been found to be the most acoustically similar to WTBM. Based on that, various applications including a distributed mode loudspeaker (DML) line array, acoustic instruments and a resonating acoustic amplifier (RAA) have been identified and evaluated. An application based on replacing tone wood in a resonating acoustic amplifier (RAA) was chosen to embody through a functional prototype. The performance of this RAA prototype showed that WTBM has potential to replace tone woods in acoustic applications; however, more research is needed to identify all the advantages and limitations of such a replacement.