Researchers at the US Department of Energy’s (DOE) Argonne National Laboratory (ANL) have developed a new magnet technology that could benefit virtually any technology that draws power from electric motors or generates power from generators.

HyMag significantly increases the usable magnetic flux density of a permanent magnet by 10 to 30 percent, leading to a significant improvement in the energy efficiency of electric motors and wind turbine generators. HyMag Magnets are less expensive and more environmentally friendly, consuming 60 to 90 percent fewer heavy-rare-earth materials.

The technology was developed by Kaizhong Gao and Yuepeng Zhang, both of whom work for the nanomaterials, devices and systems group in Argonne’s Applied Materials division.

This additional efficiency will translate into either more energy produced or you will have less loss.

—Kaizhong Gao, Argonne group leader, Nanomaterials, Devices, and Systems

Flux density is a property of permanent magnets that can be harnessed for power generation.

The higher the flux density you use for power generation, the more energy you generate. You have to have higher flux density in order to have more efficiency.

—Kaizhong Gao

Conventional permanent magnets composed of niobium, iron and boron became industrially widespread in the 1990s, yet they have resisted significant efforts to improve their performance, said Zhang, an Argonne materials scientist. Permanent magnets are a class of magnets that retain their magnetization and flux lines after they have been magnetized, conceptually similar to a battery holding electrical charges.

In the past 15 to 20 years, the increase in magnet energy product reached a plateau due to lack of material solution.

—Yuepeng Zhang

Researchers have looked into various ways to improve the composition, microstructures and processes of existing magnetic materials. Each could lead to a small improvement of the magnet’s energy product. On the other hand, the magnetic flux of a magnet decays rapidly with distance, which makes the use of magnetic flux insufficient.

Gao and Zhang have improved permanent magnet performance by combining hybrid layers of material in particular way that reduces the flux leakage. Further, they can tailor the layers for a specific application.

In electric cars, for example, the maximum allowable temperature of a motor would be around 150 ˚C. But for wind turbines, the peak temperature can be up to 300 ˚C, which calls for a magnet design that is more robust (not demagnetized) at higher temperatures.

There are materials that actually have better performance at higher temperatures.

—Yuepeng Zhang

Another appealing feature of HyMag technology is that for certain applications it may compositionally require up to 90% less heavy rare-earth elements, such as dysprosium and gadolinium, by weight, than the regular magnets that have similar performance.

These elements, mostly imported from China, are scarce, expensive and difficult to recycle. But the motors in electric and hybrid cars contain approximately a tenth of a kilogram of dysprosium per motor.

HyMag could especially benefit a weight-sensitive application, such as wind turbines, because the technology’s higher efficiency could lead to downsized structures. Stronger magnets would, for example, make it possible to reduce the amount of weight-bearing and support materials of the outer casings that sit atop direct-drive wind turbines. The outer casings account for more than half the weight of a 100- to 130-ton wind tower. Smaller casings could be designed into taller towers, allowing the turbines to access stronger winds.

But even without an optimized design, a six-megawatt wind turbine that runs half the time during the year could generate three gigawatts more power with a 10 percent efficiency increase of its generator, according to Gao and Zhang.

HyMag received a 2018 R&D 100 award for its innovative solution to increasing usable magnetic flux density. Sponsored by R&D Magazine, the awards recognize the 100 most innovative technologies of the last year.

Industry representatives interested in collaborating with Argonne in further developing this technology for specific applications, or to inquire about licensing, may contact [email protected].

The Department of Energy’s Wind Energy Technology and Advanced Manufacturing offices have provided support for the development of Argonne’s HyMag technology.

Resources

• “Novel Permanent Magnet Design to Enable Higher Magnetic Flux Density”, IN-17-017, Argonne National Laboratory, US patent filed, 2017