Recycling of thermosetting composites for wind blade application

Abstract

It is well known that wind energy could represent a promising solution to the continuous increase of energy demand in the modern society. At the end of 2016 the European wind power amounted to 153.7 GW, distributed on 77,000 wind turbines and corresponding to the 10.4% of the electrical energy supplied. Considering the EU program to increase the renewable energy share to 27% by 2030, the key role of the wind energy in the next decade is clear. As the number of wind towers that will be dismantled in the next years will continuously increase, the development of sustainable practices to dispose of these plants at the end of their life is of utmost importance. Some parts of these turbines (tower, foundations, generator and gear box) are constituted by materials having elevated recycling rates, while the blades, that are nowadays made up of thermosetting fiber reinforced polymers, are very difficult to be recycled, because of the nature of the materials involved and their complex composition. Therefore, the aim of this review is to present the state of the art in composite wind blades recycling. In the first chapter, some general concepts about wind energy and composite wind blades are presented. The second section of the work is devoted to the analysis of the most important methods for recycling composite laminates. In the third chapter, a presentation of the recycling processes directly applied on waste composite blades is reported. Considering the actual difficulties in composite blades recycling, particular attention is devoted in the fourth chapter to innovative solutions to develop composite structures with improved recyclability, with some examples of modified thermosetting composites, innovative thermoplastic laminates and composites reinforced with natural fibers. The key aspects of composite wind blades recycling and the future perspectives are summarized in the last section.