Circular applications through selection strategies (CATSS)

Abstract

Wind turbines are crucial for the energy transition, but their end-of-life treatment presents a challenge. Most wind turbine blades, made from composites, are currently sent for disposal or recycled through methods that degrade the value of the material. Structural reuse through blade segmentation was introduced as a recovery method that maintains high material value throughout subsequent life cycles. Most recovery attempts focus on thermoset composites, but thermoplastics are becoming more common. Unlike thermosets, thermoplastics can be reshaped through thermoforming processes, which offers the opportunity of adapting the geometry of a blade to new reuse applications. This paper introduces selection strategies to identify secondary applications of reshaped thermoplastic blade sections. A new methodology is proposed based on Landru's selection strategies and the Material Driven Design method (MDD). The Circular Applications Through Selection Strategies (CATSS) methodology proposes understanding a material at different levels to identify applications. Each sectioning level of the blades yields different material characteristics, such as the reshapability, that are then put into Landru's three selection strategies: substitution, selection by function, and inverse selection. Substitution directly supplants other materials with blades in an existing application; selection by function compares material properties and performance indices to derive the most relevant functions (i.e. "light-weight beams"); and inverse selection identifies suitable market sectors. The CATSS method is a systematic approach to exploring the reuse of blade sections across multiple life cycles, taking into consideration the changes in blade geometry introduced by each sectioning level. For example, the second use cycle might use blade segments for infrastructural applications like electrical transmission poles, while 3rd and 4th cycles reuse blade elements or blade units for urban furniture or automotive parts, respectively. Thus, by identifying multiple use cycle applications at various sectioning levels, we introduce structural reuse and reshaping as a long-lasting recovery pathway for decommissioned wind turbine blades. The selection strategies presented on the one hand can help identify new applications for thermoplastic composite products at their end-of-life, while on the other hand they indicate which aspects need to be considered in the original design, thus contributing to more circular practices in the composites industry.