Power up

The Opus College of Engineering’s EMPOWER Lab is building a name for itself with research in sustainable, cost-effective
solutions for electric-powered vehicles

By Chris Barncard, Comm ’03

Electric vehicles have a bit of a sustainability problem.

To displace traditional gas- and diesel-guzzling engines on the road to a carbon-free future, vehicle-grade electric motors are designed with powerful magnets made with rare-earth elements.

“Rare-earth materials make higher-grade permanent magnets,” says Dr. Ayman EL-Refaie, electrical and computer engineering professor. “The end result is they allow motors to be smaller in size and more efficient.”

That’s working for plenty of car buyers. Many popular mainstream vehicles are available in a hybrid version, and purely electric vehicles, or EVs, are as popular as ever.

“The most famous example is the Tesla, but GM and Ford and Toyota all are rolling out all-electric vehicles,” EL-Refaie says. “But cost is the key driver. If you compare a pure EV car to a comparable convention alone, there is probably at least a $10,000 price difference. That’s important, especially when the price of gas is not very high.”

The 17 metals classified as rare earths are not actually all that scarce, unlike the uncommon magnetic power and tolerance of high temperatures that made them the materials of choice in early generations of motors in hybrid
and electric cars. Their utility has driven sharp growth in other applications — from fishing reels and electric guitars to MRI scanners and wind turbines. The resulting demand has put enough pressure on a market with global political implications (China is the dominant producer) to make replacements an attractive investment.

The sky is the limit for the lab’s work to reduce the size and weight of electric motors. Or maybe the sky is the goal.

“There has been a push to try to reduce or eliminate use of these rare-earth materials as much as possible because they’re expensive, so that helps reduce the costs,” says EL-Refaie, “and also from a sustainability point of view, so that we don’t have to keep dealing with political issues and price fluctuations.”

The next advance in electric drive development could be a big step for alternatives to automobiles burning fossil fuels. In October, the U.S. Department of Energy awarded $5 million to EL-Refaie, the Thomas H. and Suzanne M. Werner Endowed Chair in Secure and Renewable Energy Systems, to incorporate alternatives to rare-earth magnets into a redesigned car motor. It’s one of several Department of Energy-funded projects putting EL-Refaie and his colleagues in Marquette’s EMPOWER Lab at the forefront of making electric motors cheaper, smaller and more efficient in cars, trucks and even planes, as well as more useful and convenient through improved charging technology.

The new wheeled-vehicle project aims to update every part of an electric (and hybrid) car’s drive and motors, except the batteries, with a mainstream benchmark in its sights.

“The ultimate goal of the project starts from a commercial baseline, and that’s the pure electric Chevy Bolt,” EL-Refaie says. “Our starting point is the electric drivetrain for the Chevy, and the ultimate deliverable is to develop technologies that GM will help integrate and test in their facilities.”

Collaborators at Virginia Tech are working on a new inverter, packing the electronics that convert the direct current electricity of batteries into the alternating current used by the motors.

Another partner, the Department of Energy’s own National Renewable Energy Lab (NREL), is doing similar work to replace typically separate cooling systems serving individual components with a single system that should save space and weight by managing the heat for a group of more tightly integrated parts. Cooling is important, as rare-earth magnets can do their thing at over 160 degrees Celsius — much higher than alternatives.

The replacement for rare-earth materials will come from permanent magnets made by Minnesota-based Niron Magnetics from a metal called iron nitride. The iron nitride magnets are high-performers and more affordable, though not yet as strong as rare-earth magnets.

“Iron nitride has many good features, but it won’t work simply as a one-to-one replacement for rare-earth permanent magnets,” says EL-Refaie, who came to Marquette in 2017 with nearly two decades of electric motor design experience. “That’s where we come in, to maximize the benefits of using iron nitride.”

In electric motors, permanent magnets serve as rotors, spun by the electromagnetic field created around them by a stator, which is usually made of copper wire wound in an arc around the rotor.

EL-Refaie says, “Higher voltage has a couple of benefits. It improves efficiency and, maybe most importantly, battery charging can happen faster at higher voltage.” The higher voltage will require further changes in the motor design,
especially in terms of the insulation system and cooling system.

The sky is the limit for the lab’s work to reduce the size and weight of electric motors. Or maybe the sky is the goal. The team’s newest project involves another multimillion-dollar grant, this one from the Department of Energy’s Advanced Research Projects Agency–Energy to improve electric drive systems for airplanes.

Weight is a big deal on a plane. According to EMPOWER Lab member Dr. Nathan Weise, assistant professor of electrical and computer engineering, batteries can’t yet match the weight of energy produced by liquid aviation fuel, limiting electric planes to small four-seat models.

“If we put enough batteries on a plane so that we have the power to take off with hundreds of people on board, it’d be too heavy. That’s a showstopper,” Weise says. “You need an immense amount of energy, and you need a way to turn that into power, for thrust for the plane, without adding a huge amount of weight or taking up much space.”

While researchers elsewhere tackle power storage, Weise and EL-Refaie are working on shaving pounds from the system while increasing the power of the power converters and electric motors. For aeronautic needs, rare-earth magnets are still welcome. But the Marquette engineers can employ methods similar to those in the electric car project — remaking the stator — by doing away with the usual wrapped copper wire altogether in favor of lighter aluminum 3D-printed into new shapes.

“Additive manufacturing can enable innovative cooling and system integration schemes,” EL-Refaie says. “With advanced cooling, you can send more current through the windings. And if you can send more current through, you get more power out of them for the same weight.”

“Distributed and innovative power electronics is another key technology development area in this demanding project,” Weise says. “Distributed power converters enable inherent fault tolerance, crucial in any aviation application.”

In addition, tight integration of the electric motor, power electronics and thermal management will be key to meeting the very challenging system requirements.

Collaborators at Florida State University will work on the development of the insulation system, NREL works on developing the thermal management system while Raytheon works on the system integration and verification testing.

The relentless quest for smaller, lighter and integrated comes through even in projects that aren’t self-propelled. With Washington-based StorEdgeAI, Weise is working on combining every part of a solar energy system except the solar panels into a portable package.

“Think of a storage container full of batteries and power electronics, minimizing the volume and weight,” Weise says.

After a disaster like a tornado or a hurricane, the units could be hauled in on trucks and dropped off, making electric power available and useful in a place— like on the road or in the skies — where it once seemed impractical or even impossible.

“This is where our expertise is,” EL-Refaie says. “Now is a moment when that can contribute to quite a few areas to improve sustainability.”