María Teresa Pérez Prado, IMDEA MATERIALS

More than half of the European Union’s electricity powers electric motors. According to estimates by the European Commission, electric motors accounted for around 53% of EU electricity consumption in 2020. The Commission reports that the 380 million motors rated between 0.12 and 1,000 kilowatts (kW) covered by European ecodesign regulations consumed approximately 1,326 terawatt-hours (TWh) in 2020, equivalent to 53% of the European Union’s total electricity consumption. Since then, the installed base has grown exponentially.

These motors drive industrial machinery as well as the pumps found in everyday household appliances. Renewable energy systems themselves depend on electric motors, and electric vehicles are now an established part of the landscape. Reducing their energy consumption therefore has a significant impact.

At this scale, even modest efficiency improvements can make a substantial difference. If efficiency gains of just a few percentage points were achieved across the board, the resulting savings could amount to tens of TWh per year.

The COP28 conference called for the global average annual rate of energy efficiency improvement to double by 2030. The goal is to increase annual improvements from approximately 2% to more than 4%. How can this be achieved?

Where Energy Is Lost

Improving the efficiency of modern electric motors is not straightforward, as they already operate at very high efficiencies. The key is therefore to focus on the sources of energy loss and find ways to minimise them.

These losses arise from several mechanisms

• Heating of conductive materials within the electrical circuits (winding resistance).
• Magnetic losses in the motor core.
• Eddy currents (small whirlpools of electric current that are generated within the metallic core as the magnetic field changes).
• Mechanical and other miscellaneous losses.

To address these issues, researchers work on improving the entire electromagnetic and thermal design of motors, while also developing materials that enable new geometries and minimise these losses.

A Different Kind of Metal

Our research focuses on an unusual family of materials: metallic glasses.

Most metals, including the silicon electrical steels commonly used in today’s motors, possess a crystalline structure. This means their atomic arrangement repeats periodically over long distances. Metallic glasses, however, have a unique characteristic: they solidify extremely rapidly, resulting in an amorphous structure. Their atoms exhibit short-range order among neighbouring atoms but lack the repeating pattern found in crystals. This turns out to be a major advantage.

This structural difference has important consequences. In an electric motor, the magnetic field in the core changes continuously as electrical energy is converted into motion. Every time the current changes direction, the magnetic material must reorganise itself, much like an elastic band repeatedly stretching and contracting. The more difficult it is for the material to reorganise itself, in other words, the higher its coercivity, the more energy is lost as heat during each cycle. Coercivity is essentially a measure of the effort required for the material to change magnetic direction.

Motor core materials must repeatedly reorganise themselves at frequencies that can reach thousands of cycles per second in some applications. In crystalline materials, the atomic structure impedes this process and increases energy losses. In addition, changing magnetic fields induce eddy currents, which dissipate energy as heat.

Although the loss in any individual motor may seem small, the cumulative effect becomes highly significant when multiplied by the billions of electric motors in operation across the EU.

Metallic glasses can reduce some of these losses, and iron-based metallic glasses are particularly attractive candidates for advanced electrical machines, especially in high-speed or high-power-density designs.

3D-Printed Motor Components

If metallic glasses have been known for decades, why are they not already widely used in electric motors?

Manufacturing them is challenging. To prevent crystals from forming during solidification, extremely rapid cooling rates are required. As a result, production has traditionally been limited to ribbons or thin sheets. The challenge is to preserve the desired amorphous structure while producing three-dimensional geometries that can ultimately be used in electric vehicle motors.

This challenge has been a key focus of the European project AM2SoftMag, funded by the EU’s Horizon Europe programme. The project brings together specialists in materials science, manufacturing and electric machine design to investigate whether metallic glasses can be transformed into functional motor components.

Starting from Powder

At IMDEA Materials Institute, we have worked with laser powder bed fusion processing of metallic glass powders. This approach provides an inert environment to prevent oxidation while enabling the manufacture of complex geometries with minimal material waste.

In a recent study, the consortium developed and investigated a new iron-based metallic glass alloy composed of iron, silicon, boron, niobium and nickel, featuring improved glass-forming ability. The alloy achieves thicknesses of approximately 1 mm without the addition of phosphorus, cobalt or rare-earth elements, thereby avoiding dependence on both cobalt and rare-earth materials.

The team achieved relative densities above 92% under all investigated conditions and amorphous fractions exceeding 87%.

The coercivity of the new material reached values as low as 44 A/m (amperes per metre). In practical terms, this means the material can be magnetically reoriented with very little resistance. It is rather like comparing a soft elastic band, which stretches and contracts effortlessly, with a stiff spring that requires considerable force during every cycle. This is why such materials are known as soft magnetic materials. The term does not refer to their physical hardness; instead, it describes their ability to respond easily to changes in magnetic fields. This responsiveness translates directly into lower heat generation and reduced hysteresis losses.

There is still work to be done. Among other challenges, researchers must further reduce the material’s porosity and scale up production to quantities suitable for commercial applications.

While we cannot yet demonstrate efficiency improvements at the full motor level, we have established a technically promising pathway that combines alloy design and additive manufacturing to reduce energy losses in electric machines. It is an open avenue of research, but one with considerable promise.

María Teresa Pérez Prado, Professor and Senior Scientist, Sustainable Metallurgy, IMDEA MATERIALS

This article was originally published in The Conversation. Read the original (content in Spanish).