Developed by the Fraunhofer Institute for Chemical Technology, it is also cheaper to build.
Mass, aerodynamics, and powertrain efficiency are the three pillars of a more efficient combustion engine vehicle. Although electric cars already have the most energy-efficient engine man has ever created, it also pursues low weight. And more aerodynamic designs, as pop-out door handles and cameras instead of rear-view mirrors clearly demonstrate. But they also have room for improvement. Curiously, one of these opportunities has been found on the most unlikely element: the electric motor. What if its housing is made of plastic in place of metal? This is what the Fraunhofer Institute for Chemical Technology (ICT) and the Karlsruhe Institute of Technology (KIT) have recently proposed in Germany.
“An electric motor consists of a rotating rotor and a static stator. The stator contains the copper windings that the electricity flows through – and this is where the majority of electrical losses occur”, says Robert Maertens, a researcher at Fraunhofer ICT. Maertens refers to the 10 percent of losses that happen through the heat in an electric motor. This is why electric cars are so efficient: 90 percent of the electric energy becomes movement, while the very best combustion engines can only turn 40 percent of the chemical energy contained in fuels to work.
The new motor addresses the 10 percent of losses in current projects. In order not to overheat, these motors present a metal housing that guides the generated heat to a cooling sleeve, also made of metal. The Fraunhofer engine uses rectangular flat wires around the stators instead of the round wires used nowadays. That saves space for cooling channels close to the stators. “In this optimized design, the heat losses can be dissipated through the cooling channel inside the stator, eliminating the need to transport the heat through the metal housing to an exterior cooling sleeve”, says the researcher, who also points to other advantages, such as lower thermal inertia, what means it can cool down much faster, and higher continuous output, something that does not need any explanation. The rotor also has a cooling solution in this project.
This higher cooling efficiency is what allowed the researchers to built the engine from plastic. Better saying, from fiber-reinforced thermosetting plastics. “Polymer housings are lightweight and easier to produce than aluminum housings. They also lend themselves to complex geometries without requiring post-processing, so we made some real savings on overall weight and cost”, says Maertens.
According to the researchers, prototypes take only four minutes to be built. And mass-production will be relatively easy to achieve. In what relates to the cooling process, it prevents 80 percent of the 10 percent of losses. That alone increases the electric motor efficiency to 98 percent, but the researchers believe they can make the 20 percent left, or 2 percent of total losses, be lower still by optimizing the flow of coolant. If these motors prove to be as reliable as the ones with metal housing, we will soon get lighter, cheaper and more efficient vehicles. It is just a matter of waiting for solid-state batteries to become a reality to have a quantum leap regarding EVs. In all aspects.
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