Over the past 40 years, the wind industry in Europe has driven the energy transition through innovations that have pushed turbine availability, efficiency, and performance to ever-expanding heights. As a result, onshore and offshore wind power plants help Germany generate nearly half of its electricity from renewable sources at affordable prices.
If we want to expand the share of renewables in Germany to 80 percent by 2030, that currently means no less than doubling the installed capacity. This new decade of growth ahead of us, poses new challenges as we must make it as sustainable as possible to use finite resources as efficiently as possible.
Employees during the production of recyclable rotor blades © Siemens Gamesa
Rotor blades are robust and material-intensive
Currently a large part of the turbine can be recycled; the steel in the towers and the copper in the cables - in total approximately 85 percent. The rotor blades, however, were a challenge until recently because of the technical prerequisites of the materials.
The rotational forces found in operational wind turbines put immense strain on the blades. With tip speeds reaching approximately 90 meters per second – equivalent to 324 kilometers per hour - and a projected lifetime of more than 25 years, high quality and innovative design is imperative especially when considering their exposure to hail, lightning or, in the case of offshore turbines, their exposure to salty. For a 108-meter-long offshore blade the rotational forces are around a staggering 80 million newton meters. To put this into perspective, the force pulling on a human shoulder while spinning a 1 kg object around in an outstretched arm is only about 10 newton meters!
First installation of recyclable blades in Kaskasi wind park in Germany 2022 © RWE / Fotograf Matthias Ibeler
Several components make recycling challenging
With the growing size of the blades, the reinforced fiberglass structure has been supplemented with carbon fiber technology. Carbon is a stiff and light material, and the result is a very reliable and robust blade design which is perfect for the extreme conditions. But as all components are bonded together, adding the carbon increases the difficulty of separating them at the end of the blade’s life cycle.
The challenge of recycling the blades at end-of-life is related to the durable nature of the thermoset resin used, which makes it energy-intensive to separate the materials at end-of-life either mechanically, thermally, or chemically. However, with adaptations to the traditional resin system, this challenge has now been mastered for the first time.
The solution: easier separation of the components
Innovative recyclable blades use a new resin that can be easily dissolved in a mild acid solution at the end of the rotor blade's life cycle. This is achieved by a chemical change in the structure, which creates a ‘cleavage point’ that can be activated by a combination of heating and exposing to acidic solution. By doing so, the resin will dissolve and become a thermoplastic recyclate that can be used for new purposes. For example, suitcases or monitor housings can be built from the recovered material. Also, the remaining materials in the blade, such as fiberglass and wood components, can easily and energy efficiently be separated from each other and returned to the material cycle.
The process has been developed in a way so that the production process remains the same and therefore does not require new processes, equipment or facilities, but can utilize the existing processes as the current manufacturing setup. The recyclable blade can be produced for any offshore turbine and any size of blade. The material properties of the new resin are higher than those of the old one. Furthermore, the resin has been designed for extra slow reactivity to enable improved processability and to cure faster than conventional materials, thereby contributing towards lowering cycle time in blade manufacturing.
Recyclable blades: Only one year from theory to practice
Just as remarkable as the technology itself was the speed of getting the recyclable blades into market. From the introduction of the technology in late 2021 to the first deployment in the offshore wind power plant Kaskasi in the German North Sea less than a year has passed. That this speed is urgently needed, is highlighted by a little figures game. Adding up all Offshore projects in the pipeline worldwide until 2050, more than 200.000 blades will be installed. Considering that landfill used to be the solution for decommissioned rotor blades in the past, these blades one after another would span around half of the globe with more than 22.000 kms length and a total weight of more than 10 million tons.
Recyclable rotor blades ready for transport © Siemens Gamesa
Currently, the recyclable blades come at a price increase compared to the conventional solutions. However, the end-of-life costs will on the other hand decrease while the recycling rate of the blade will increase significantly compared to landfill or energy recovery processes often applied to conventional blades today.
Laws and environmental protection demand more sustainability
What happens today to decommissioned blades is laid out in different national legislations. In Germany, the operators carry the responsibility and landfill is already not an option anymore. One option would be to repair and reuse these blades but considering the high prerequisites for the material this option clearly has its limits. Repurposing old blades for pools, playgrounds, bicycle stands, or the like is a fashionable option, but these will also require material recycling at some time. Recycling options for the composite materials are available today, but they are neither available cost competitive nor at the scale necessary. This leaves for most old blades the option of regaining the thermal energy in them, meaning incineration and co-processing for example in cement production.
We want the wind industry to be a part of the solution by having a small carbon footprint value chain and fit in a circular economy
Martin Gerhardt, Managing Director of Siemens Gamesa Germany
Wind power plant operators could benefit from this new technology because it reduces their environmental footprint, which becomes increasingly important as qualitative criteria are introduced in more and more auction systems. Additionally, at the end of the plant's life, when the operators must dismantle it, they do not produce waste or simply energy for incineration, but they get back valuable raw materials.
Reccyclable blades show what the european wind idnustry is capable of
This new technology is a good example of how the wind industry in Europe pushes the energy transition with new innovations and as a result creates many jobs and value across different countries. The blades that were used in the Kaskasi wind farm are a multinational project: The development took place in Denmark, the blades were produced in the United Kingdom and the nacelles for the project came from Germany. This European collaboration underlines the technological experience and innovative character of the European wind industry and also highlights that Europe can hold security of supply in our own hands.
We will need to rapidly deploy wind turbines to help decarbonize, avoid climate change effects, and support energy security. With the recyclable blade it is demonstrated that this can be achieved in a waste-minimized matter, where we are also reducing the carbon footprint of the wind turbine life cycle by making materials available for future purposes after having produced renewable electricity for many years.
This Article is part of issue 03-2022 of the current issue of German Wind Power Magazine, the international magazine of the German Wind Energy Association (BWE) about innovations of the German wind industry. You can read the full magazine here, online and for free.