The growing demand for rare earth elements is creating a number of environmental, geopolitical, social and technical challenges. In this article, we explore how copper could help address them.
Copper benefits from good and well-distributed global availability, well-established mining techniques, a relatively stable price, a transparent global market pricing mechanism and sustainable recycling processes. This makes it an interesting alternative to rare earth elements (REEs) for rotating machines. While the share of usage of REEs in this application is currently modest, it is growing fast. As such, copper is one of the answers to reducing the EU’s dependency on REEs.
There are 17 REEs found in the earth’s crust. Their unique magnetic properties make them a key component of many 21st century technologies such as smartphones, hard drives, electric vehicles and wind turbines. An iPhone, for example, contains eight of them. REEs are essential, and in great and growing demand. Therefore, the the EU is working to improve access to these metals, reduce their consumption and improve extraction conditions in Europe to address existing concerns related to their supply, recycling and price evolution.
Copper as an alternative
For many of the applications mentioned, there are currently no straightforward alternatives. However, for the growing use of rare earth materials in rotating machines (used in, for example, electric vehicles and wind turbines), there is copper.
The majority of motors in electric vehicles currently rely on permanent magnet technology using rare earth magnets. Permanent magnet technology offers advantageous technical features, but there are also technical drawbacks, such as the demagnetisation risk if the temperature of the motor exceeds a certain limit. Adding these technical drawbacks to the overall challenges of REEs has led to new interest in developing alternative technologies that do not use permanent magnets.
One such project, funded by the European Union’s Horizon 2020 research and innovation programme, is called ReFreeDrive (Rare Earth Free Drive). It is looking to improve two motor technologies beyond the current state-of-the-art: copper-rotor induction and synchronous reluctance. The improvement will take place at several levels: motor design, materials formulation (steel and copper) and use of advanced technologies for wiring.
The project also addresses the design of power electronics using wide bandgap semiconductors, and of the control system, including battery charging functions. Two power levels are being analysed–75 kW and 200 kW–for their further prototyping, testing and integration on one EV vehicle. This power range covers a significant share of road and goods carrying vehicles.
In the field of wind energy, direct-drive generators equipped with full power converters are emerging as a leading technology option, since they avoid the use of gearboxes (which are the number one source of outages and frequent maintenance) and optimise the overall operation of the wind turbine. This technology is largely based on generators using permanent magnets. There exists, however, a copper-based alternative using excitation technology that skips the use of rare-earths, while taking full advantage of direct-drive benefits. It is currently used by a limited number of manufacturers, but it could be adopted more broadly.
What are the advantages of copper?
Good and well-distributed global availability
The supply of copper is well distributed: Chile (28%), Peru (12%), China (9%), and the US (7%) are the four top worldwide producers. Data has been collected on copper reserves for a long time, and it shows reserves are plentiful.
Mature mining technology
Most copper is mined by large, international companies adhering to strict safety and environmental standards. They use a mix of well-established open pit and underground mining technologies.
Copper operates on an open market with balanced supply and demand. Demand for primary copper in the EU is around 4.2 million tonnes per year. 37% of this need is covered through imports, 18% through copper production in Europe (Poland, Sweden mainly) and around 45% through recycling. Consequently, the EU has a manageable exposure to raw material imports in this sector and is at the forefront of the circular economy for this metal.
Copper can be recycled without loss of properties, and recycling is performed in economically stable and value-adding ways. Copper is also a carrier metal for many valuable substances such as tin, nickel, molybdenum, lead, cobalt, precious metals, rare earths, sulphuric acid and final slags.