3D printing, or additive manufacturing (AM), is “the process to make parts from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing and formative manufacturing technologies” . Contrasting with these latter technologies, AM can produce components with complex geometries, consume fewer raw-materials, produce less waste, has decreased energy consumption and reduced time-to-market.
Adding numbers, AM can speed up the development time by up to 75%, reduce material resources by up to 65% and reduce gas emissions by up to 30% . Moreover, a single part can be manufactured in one step, not requiring a secondary joining process [3, 4].
Additionally, additive manufacturing doesn’t solely need to be applied to the early stage of development, but can also be incorporated in the repair of components.
In the early stage of being introduced to the market, AM was used to create and develop models and prototypes. However, due to all of the advantages offered, the market for 3D printing products started to grow, especially in areas with short-run production and with high customisation and freedom of design .
There are several additive manufacturing processes and techniques that can be classified in terms of heat source, the feedstock and the manipulator . The processes can be applied to multiple types of material, including polymers, which are more common and developed, composites, ceramics and metals .
Additive manufacturing applied to wind turbines
The Global Wind Energy Council has stated that the wind industry is experiencing exponential growth in recent years with the aid of the offshore wind turbines market. Thus, development and innovation through materials and manufacturing technologies are essential for the wind industry to prosper and to continue increasing their annual energy production .
Figure 1 shows a general representation of wind turbine components.
The blades rotate and shift with the action of the wind, making the rotor spin. The gear-box makes the connection between the low-speed shaft to the high-speed shaft, increasing the rotations per minute from 30 to 60 rpm to approximately 1000 to 1800 rpm, in turn making it possible for the generator to produce electric power. The tower supports the turbine’s structure, with the nacelle containing and protecting the components on top of the tower .
AM technologies show a lot of potential when it comes to the wind power industry, as it could in the future enable in-situ manufacture of turbine components that are designed for the unique needs of the resources of a particular location. This would, for example, decrease the shipping, transportation and handling costs and increase the rate at which new blade prototypes can be tested .
The 5 areas in wind energy where additive manufacturing is set to make its mark
Additive manufactured moulds
The Advanced Manufacturing Office (AMO) of the US Department of Energy has started to print moulds for the blades with AM technologies, as shown in figure 2. Consequently, it can make the wind energy a more market competitive technology. The expansion of this application in the mould industry would reduce the steps, the cost and the time for mould fabrication, as the traditional route is a process that may take several weeks to months to achieve in its totality [6, 10].
The mould in figure 2 was printed by using by joining multiple printed sections created in the Big Area Additive Manufacturing (BAAM, figure 3) 3D printer at Oak Ridge National Laboratory .
The final blade section was successfully manufactured using the AM mould and can be seen in figure 4.
Additive manufacturing of small, off-grid turbines
A different project called ‘A Small Turbine to Make a Big Difference’ started by Kyle Bassett, has the goal to install small-scale plastic-based 3D printed wind turbines in remote areas with a lack of access to electricity. The founder of this project started by designing a turbine capable of storing the generated energy in batteries for personal use .
As a result, a scale model of the turbine (figure 5) was developed using a Printrbot Simple Metal 3D printer . It included the blades, hubs, rotor connectors, the frame, and the blade ends, which would be the most expensive components if made through traditional manufacturing methods .
Other applications could include the creation of the nacelle. The advantages of incorporating AM into such structures are similar, e.g. economic incentives for mould production, but challenges are also encountered, such as the need to offer weather protection, passive cooling and high geometry complexity.
The Additive Manufacturing Integrated Energy (AMIE) project, however, has successfully manufactured the nacelle structure and it can be seen in figure 6 .
Repair and replacement of components
Even though most of the attention is focused on the manufacture of new components, the repair of parts which need improvement or replacement due to wear should also be considered. For this application, hybrid systems incorporating processes such as Directed Energy Deposition with subtractive machining could eventually lead to the proper tolerances and design imitation of the replaced components .
Printing large-scale components
Large Scale Metal AM or Wire and Arc Additive Manufacture is an emerging technology which may facilitate the printing of large-scale parts. This even makes additive manufacturing of the nacelle and blade moulds possible, as it doesn’t need a constricted operation room, allowing, as the name indicates, large-scale applications .
Overall, additive manufacturing technologies offer a wide range of advantages for the wind industry. The examples given show that implementation is possible, and even recommended, for a more market-competitive energy supplier. After the technologies become more developed, reliable and standardised, the supplier chains will be reduced and the production could be more localised, reducing the transportation times and costs, furthering the implementation of AM in the wind industry.
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