The new resin makes the wind turbines recyclable

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If we are to move to a truly sustainable society, the circularity of materials and energy must go hand in hand. If the electricity we use to power our cars comes from fossil sources, the environmental impact is still significant. The same goes for wind turbines. They could produce clean energy for decades, but what’s the point if their bulky blades end up in landfills for centuries? However, have a low carbon production per kWh fed into the grid, around 6 grams of CO22 equivalent – ​​old turbines represent an additional source of waste. A new resin to bond blade components together is paving the way for making them fully recyclable.

Why we write on this topic:

Solar and wind energy will power the future, but they also lead to waste streams. Recyclable wind turbines help achieve 100% green and circular energy.

The wind blades are cast using glass and carbon fiber. A core material that can be wood or PET plastic – the same used for bottles – and an epoxy resin system. The latter attacks all the components, making it more difficult to separate the materials when the turbine reaches the end of its cycle. The resulting compound is called fiber reinforced composite – FRP. Siemens Gamesa has devised a new cohesive substance that allows easier separation of materials without compromising performance. The first recyclable blades are already spinning at the Kaskasi offshore wind farm in Germany, operated by energy company RWE.

Growing waste stream

Recycling wind turbines has been a tricky business. While there are creative solutions – Siemens Gamesa itself has repurposed some as bicycle sheds – most of them end up in landfills. Conversely, other wind turbine components can already be recycled. The tower is made of steel, which can be reused countless times. If wind energy is to play a crucial role in the coming decades, the management of its waste is just as important. According to a study by the University of Cambridge, wind turbines will generate 43 million tonnes of waste by 2050. Moreover, countries are banning landfills: Austria, Finland, Germany and the Netherlands have already banned it.

Recyclable wind turbines have the same characteristics

Not much changes between the non-recyclable and the blades made with the new RecyclableBlade technology. “The good part is, there wasn’t much redesign needed to be done. The new cohesive substance has the same set of properties as the one we use for conventional ones. In addition, the manufacturing processes and lifetime of the blades remain unchanged,” Harald Stecher, blade materials engineer at Siemens Gamesa told Innovation Origins.

Wind turbines have a relatively simple structure and few components. The so-called beam is the inner part. It is made of fiberglass and carbon, with a resin coating. Two shells, also in fiberglass, cover the beams. Subsequently, shells and beams are assembled, passing through a kiln to join them into a single structure. After a check, the blades are ready to reach their destination.

The manufacturing process – © Siemens Gamesa

This procedure applies to all types of wind turbines up to 110 meters in length. Siemens Gamesa’s prototype recyclable blades will soon reach 108 meters. They are suitable for both onshore and offshore wind farms. Since they are similar to conventional blades, the maintenance procedures for recyclable blades also remain the same. These operations mainly concern the control of cracks in the structure and do not require any additional intervention to be performed on the recyclable ones.

“The concept is potentially plug and play, but we are far from understanding the potential of the material. We’ll explore the process more, we still have to play around with temperatures and brew times. There may be further gains that we are not aware of yet,” adds the engineer.

Harald Stecher
© Harald Stecher

Harald Stecher

Blade material engineer at Siemens Gamesa

He is part of the materials team, responsible for the resin of the blades.

Regular process

What makes the difference is the chemistry of the resin. In particular, the bonds of the compound can be broken more easily. When it’s time to dismantle a wind turbine, the blade is first cut into pieces of small square meters. The pieces are immersed in preheated and diluted acetic acid – up to 90°C – for a couple of hours. Subsequently, they rest in a ventilated room, where the epoxy compound dissolves and the separation of the materials takes place.

In this way the recovery of the fibers takes place. Then the resulting solution is filtered to recover the cohesive substance as well. It can occur in two ways, by evaporation or by neutralization – a chemical reaction in which an acid and a base react together – of the solvent. Regardless of breaking the material bonds, the stiffness and strength levels are nearly the same as the parent material. Thus, the resin can be reused for non-stressful uses such as that of a wind turbine blade, yet still ready to serve in demanding industries such as automotive.

“When comparing the process to similar ones it is worth noting that it operates below the boiling point, which means there is no risk of overpressure. This means that the equipment needed doesn’t have to be as sophisticated as that needed to perform other types of procedures,” notes Stecher.

Fully circular wind turbines

At the moment, the technology is being introduced. By 2024, Siemens Gamesa aims to ramp up production as its supplier builds a plant to produce the new resin on a larger scale.

2040 is the deadline set by Siemens Gamesa to build a 100% recyclable wind turbine. Since the blade recycling code has been cracked, the spacecraft And then. It is the cover that houses the critical components of the turbine, such as the transmission, generator and gearbox. The carrycot is also made of composite fibers with a similar resin coating. The knowledge gained in recyclable blade design will come in handy, although a great deal of research is needed as the components need to be durable and safe.

“We solved the main structure. However, there are smaller things to consider, such as turbine magnets and other small parts that we need to have a fully recyclable blade,” summarizes Stecher.

© Siemens Gamesa

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