This thesis presents the design process of a novel noise barrier design made from horizontally arranged, decommissioned wind turbine blade material.

To address climate change challenges worldwide, wind power is increasingly being adopted. The wind turbine blades (WTBs) used for them are decommissioned after 20-25 years, at which point a problem emerges: the complex material composition makes that current end-of-life options result in the loss of material value without regaining significant economic value. The aim is therefore to structurally reuse WTB material in applications that preserve material integrity and prolong its lifetime. Scalable and long-lasting noise barriers are consequently identified as a fitting opportunity. This thesis focuses on horizontal arrangements of WTB material for use in a noise barrier as this is underexplored and will more closely resemble conventional building materials.

However, due to the variable curved shapes of WTBs, seamless assembly in noise barriers becomes challenging. Especially since gaps compromise the noise attenuation of a noise barrier. The proposed design is a solution to that challenge. It configures WTB panels in modular cassette-panel-cassette sections that allow for tackling alignment issues and can be easily (dis)assembled on frame structures. It attenuates noise by reflecting sound waves into the sky off of tilted, continuous front panels. A second column of panels further reduces sound transmission behind the barrier. Continuity and aesthetic harmony of the barrier in its surroundings is aimed for by use of climbing plants and a green colour palette.

The design follows from a process based on research. Led by a vision on durability, modularity and feasibility, ideas are developed into two concepts that are evaluated with input from experts. Subsequently, one integrated concept is further developed through (CAD) modelling, prototyping, testing, simulating, and a survey.

Three research questions are answered throughout this process. To ensure seamless fitting, a parametric model is developed to inform segmentation strategies. It filters out excessively curving parts to retrieve suitable panels. Alternating the orientation of cladded panels and avoiding seams in the road-side surface of the assembly further tackle alignment issues. Analysis of existing noise barriers reveals that mounting and assembly are facilitated by use of modular cassette-based systems. Cassettes can accommodate the WTB panels that contain variable curvature. A prototype is developed to test fastening options, resulting in an adjustable and reversible clamp design that allows for acoustic sealing. The resulting cassette-panel-cassette modules can be pre-fabricated off-location to reduce time spent on-location. Maintaining opportunities for next material lifecycles is found to largely depend on resizing activities. Large panels are prioritized as they can be more broadly reused than smaller ones. Additionally, protecting exposed core materials of sandwich structures (balsa wood and foam) against weathering is important. An explorative test with epoxy coatings provides starting insights to this end.

Overall, the valuable insights in this thesis culminate in a functional, feasible and desirable noise barrier made of WTB material, and highlights areas for further industry research.

Softtop surfboards have become very popular over the past decades, especially within surf schools. They are beginner-friendly, and aren’t damaged as easily as traditional fibreglass composite boards. However, the design and materials used in these boards make end-of-life strategies very limiting, resulting in a product that is generating a significant amount of waste. The effective lifetime of these boards is only two years, and most surf schools burn through approximately 70 boards during this period. To turn this linear lifecycle around, this thesis proposes Tides: a product-service system for softtop surfboards. It consists of redesigning the current softtop construction and a service system through which the boards can be accessed within a circular business model.

Through co-creation with different Dutch surf schools, a subscription-based service model is developed. It takes ownership over the boards away from users, and provides them with the guarantee of always having quality softtops. The system makes use of the seasonality in surfing, in which the low season is used to take the boards back and restore them professionally. After materials have gone through multiple iterations of reuse, the boards go into a second lifecycle by leasing them to individual surfers. These use the boards on a less intensive scale and demand less quality.

Restoring the boards is done through three different recovery strategies, which are a result of a thorough analysis of the failing mechanisms of current softtops. Each strategy has its own touchpoints within the lifecycle of the boards. The first one, Repair, is used to temporarily fix boards untill the end of the high-season. The second one, Repair+, is done periodically at the end of the season. Finally, Refurbishing is done when the boards can’t be repaired anymore without seriously hurting performance.
The Repair strategy was developed into a technical proof of concept, as this is the first step towards realising a viable circular business model. The patches were prototyped, tested on waterproofness, and evaluated on user-friendliness with surf schools.

The recovery strategies resulted in a new construction design concept. The construction allows for easier implementation of the three recovery strategies, and introduces a few new features to improve the durability of the boards. This concept will be developed further in the future of this project, and its viability in the product-service system will be evaluated with surf schools.

More and more wind turbines are erecting in the landscape, stemming from the need for sustainable energy. However, less attention is paid to the secondary effects of these wind turbines, more specifically, the wind turbine blades. Wind turbine blades are made of composite material, a material that provides many advantageous properties for the desired functionality. Nevertheless, the material is difficult to reuse or recycle after the lifespan of the wind turbine blade. This challenge is expected to result in thousands of tons of decommissioned blades entering the market in the coming years which, due to the absence of good alternatives, are most likely to be disposed of in an unsustainable manner.

This project focuses on how composite material from decommissioned wind turbine blades can be reused in order to retain the value embedded in the material. It explores how delamination can potentially add to design freedom of the material for it to be used in a scalable way and match the large influx of the material. Focus is put on the curved elements of the blade: the inboard and outboard sections. Aside from producing scientific knowledge on the topic, the aim is to exhibit the findings through means of a demonstrator of a potential reuse application.

In chapter one, the thesis starts with research into background information, identifying the knowledge gap, setting the scope and conceiving the mission and research questions for the project. Then, in chapter two, a better understanding of a wind turbine blade is formed based on a reference blade. After this the geometry of the blade parts in focus, together with the material composition is researched. Chapter three dives into the possibilities of retrieving elements out of wind turbine blades and looks at the characteristics of these elements.

In chapter four the delamination of the sandwich structured wind turbine material is explored. It is investigated how this can be done and what potentially influences this process. Then, in chapter five the material characteristics of the retrieved and delaminated elements are analysed. This showed that the material can be elastically deformed, opening up the floor for a broader range of reuse applications.

The most suitable reuse application is then methodically determined in chapter 6. Based on, amongst other things, the material qualities and the vision, the choice fell on a bus shelter. A concept of this is then proposed and concretised in the form of a demonstrator. It exhibits the possibilities of the material and embodies the approach for facilitating reuse of decommissioned wind turbine blades on large scale as presented in the project.

In the end, the report concludes with an evaluation of the design and the process in the form of a discussion, a summary of the findings and multiple recommendations to improve future sustainability with respect to wind turbine blade material