Wind Energy – Addressing the Challenges of Tomorrow, Today

In this edition of Beyond Bax, we return to the topic of wind energy. Speaking to Philippe Spring, structural design engineer at TPI Composites – the largest U.S.-based independent manufacturer of composite wind blades – we cover the main challenges regarding the wind industry’s waste, and ways to address them using available technologies and practices.

Deployment of wind turbines is growing every year, and so is their size. That means quite a lot of composite waste when these turbines reach their end of life. What are the main challenges that need to be addressed in order to tackle this issue?

PS. The wind industry, by designing structures and choosing materials, bears most of the responsibility to account for end-of-life strategies. To strengthen its steadily growing importance, these solutions need to correspond to the basic sustainable concept and initial idea of renewable energies. In terms of recycling, the overarching challenge is to recover the most possible value of entire structures or materials with processes which economically underbid the sourcing of virgin raw materials or manufacturing of new structures.

From a technical point of view, there are two challenge levels. The first and most urgent is the treatment of existing thermoset-glass fibre-blades which were designed without awareness of requirements regarding recycling. For the blades with immediate necessity of treatment, dismantling and recycling networks need to be enabled to act responsibly and reproducible.

wind energy
TPI Composites blade

The second challenge level is related to the development of blades showing significantly reduced beforelife and end-of-life footprints. Not only the recycling rates need to be increased but also the ecological impacts of material sourcing and blade manufacturing before commissioning can be analysed to identify and avoid for example CO2-emission sources. 

Which technologies or practices do you think will help us address the above challenges, and which are you focusing on in TPI Composites?

PS. Recycling rates of composite parts can be increased significantly when the industry finds viable ways to develop and use recyclable resins such as recyclable/reprocessable/repairable-thermoset (3R-TS) or thermoplastic (TP) resin systems instead of “classic-crosslinked” TS-resins. There is a wind specific TP-resin formulation available on the market and TPI Composites had the chance to study its abilities within a research program.

For future blade designs, the application of new materials should be justified by methods of the Life-Cycle Analysis (LCA) to show their advantages in terms of emissions and other socio-ecological aspects. The use of second-life fibres, resin or entire blade sections within blade or other industries can be interpreted as energy credit and is beneficial to the LCA-results.

Regarding the present and near future treatment of blades, the cement-kiln route is available: The use of glass fibre reinforced plastic (GFRP)-flakes as refuse-derived fuel (RDF) reduces the combustion of coal and the residual silicon dioxide from the glass fibres helps to avoid the mining of siliceous sands. To facilitate the segmentation, transport and chopping of blades, their material composition, mass and dimensional properties need to be made accessible to the involved companies. It can be realised by documentation in an Environmental Product Declaration (EPD). At TPI Composites we can provide the service of EPD creation for our customers and their blades.

Although technologies for recycling and retrieval of full fibres from composites exist, it’s difficult to make the business case for glass fibre, as the added costs for recycling it are much higher than virgin GF. How do you think we could address this issue?

PS. The chemistry of established TS-matrices is not primarily designed to allow for economically reasonable recovery of full-length fibres. Instead of investing high efforts to separate resin and fibres, I prefer secondlife applications of entire wind blade parts, such as shell and web sandwich panels or massive spar caps. These parts keep most of their valuable integrity, can be characterised technically and commercially to become structural elements for the construction or transportation sectors. Recycling networks across industries can allocate demand and supply. All these activities need to be analysed ongoingly by using the LCA-methods to show that reuse of parts is the favoured way compared to newly produced parts from virgin raw materials. 

In parallel, to increase possibilities of full-length fibre recovery, we can work on reformulation of existing TS-hardeners to create 3R-TS-resins featuring dynamic crosslinks. In addition, further elaboration on the potential of TP-resins and their establishment as alternative resin is a promising path to follow as a backup. 

Achieving sustainability in the energy sector requires the involvement of all stakeholders within the value chain. How can we raise attention/awareness among designers and manufacturers regarding product responsibility? 

PS. The suitable standards, methods and documentation types already exist, for example in the building sector: Environmental Product Declarations (EPD) and sustainability product labels can reflect the ratio of generated electricity to expended energy/emissions by use of LCA, characterisation of material composition and manufacturing circumstances assessment. The wind turbine as an energy converting product already shows an undisputed positive LCA-result. Design guidelines for recycling can enable designers to further increase the positivity of the LCA-balance and to promote suitable End-of-Life solutions. 

All above-mentioned practices and development of technology to increase sustainability require time and investment. I see companies willing to do the next steps and publishing sustainability plans. Today’s policymakers understand the need to offer incentives such as the Horizon 2020 program which is welcome and suitable as a steering method. 

You have been working in the wind industry for a few years already. How do you see the progress made towards sustainability, and what’s next?

PS. When I began my working life as a structural engineer with a focus on lightweight materials, my doubts regarding land-use change driven by Balsa farming in Ecuador, questionable use of PVC-core material, or consumables waste generation as a result of the vacuum infusion process, were not widely reflected among colleagues. This situation has changed a lot, meaning that in terms of sustainability requirements, people are no longer relaxing working for the renewable energy sector. Most of my professional contacts are interested, caring and willing to contribute within the given time and financial budget. 

The next step can be a reward system to promote sustainable design and manufacturing. The pricing of ecological costs to increase the levelized cost of energy (LCOE) would represent the other way around but have the same effect. Solutions like thermoplastic resins or Environmental Product Declarations are already available. By offering blade design for sustainability, TPI Composites can support its customers to anticipate these upcoming steps.

At Bax & Company, we’re lucky enough to work with experts in emerging and existing fields from around the world. Beyond Bax is an opportunity for us to share some of their knowledge with you.

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