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Illustration showing what an electric-powered aircraft might look like. Credit: NASA

Aviation is one of the backbones of the modern world, moving people and goods around the planet in a method that far outpaces other transportation options. The industry’s carbon footprint has long been criticized, however, with increasing calls for improved efficiency and reduced emission in aircraft.

The results of a recently concluded five-year, $2 million project led by the University of Tennessee, Knoxville, and Boeing for NASA could have major implications on aircraft design and performance for decades to come.

Fred Wang, Condra Chair of Excellence in Power Electronics

“We were able to develop a high-performing low-weight inverter that allows for electrified propulsion, something NASA has identified as a goal for the next generation of flight,” said Fred Wang, the Condra Chair of Excellence in Power Electronics in UT’s Tickle College of Engineering. “This allows for greater fuel efficiency while the switch to electrified propulsion also drastically reduces the amount of pollution produced, which is a real win–win.”

In a significant technological advance, the team’s inverter is the first of its kind capable of operating at a megawatt level using cryogenic cooling. The team showed that the technology is scalable to much larger sizes, crucial for widespread adaptation.

At its most basic level, the inverter that Wang and his team developed helps turn energy into physical movement within aircraft engines.

Critically, it does so at a rate of more than 99 percent efficiency, meaning there’s almost a one-to-one ratio of energy used to propulsion produced. Cryogenic cooling—which can be accomplished without added weight by using liquified natural gas or liquid hydrogen—makes the inverter a natural fit for future superconducting motors, further improving the efficiency of the system.

With the volatile nature of fuel costs playing an oversized role in the relative success of airlines, aircraft, and routes, that efficiency is especially important.

NASA has been developing future aircraft technology to make large reductions in aircraft energy use, emissions, and noise. One concept that builds on the new technology is the N3-X future hybrid-wing body electric airplane, which employs a turboelectric distributed propulsion system. This aircraft is equipped with two wingtip-mounted superconducting generators and multiple superconducting motors to run fans mounted on top of the fuselage—all of which is dependent on the new UT–Boeing technology.

“To enable us to develop NASA’s turbo-electric propulsion for large transport aircraft, pure superconducting electric machine development along with a cryogenically cooled inverter is one of the most essential technologies,” said NASA Technical Monitor Benjamin Choi. “In collaboration with Boeing, the UT team has successfully demonstrated a megawatt-level cryogenic inverter, and this great achievement has paved the way for the feasibility of using superconducting machines for NASA’s mission-critical electrical propulsion for large transport aircraft.”

The project’s NASA team received one of the agency’s highest achievement awards for its role in developing the new technology.

Wang said the project is just the latest example of research UT has done with Boeing to meet those goals, noting that the two have almost 15 years of working together on improving aircraft and their systems—work that has impacted global air commerce.

“People around the world are really putting an emphasis on the environment, and companies like Boeing are looking to see how they can make things better,” said Wang. “Aviation is a vital part of our interconnected word, both economically and socially. Making it better for the environment allows that to continue, but in a way that benefits everyone.”

Joining Wang on UT’s team are Min H. Kao Professor Leon Tolbert, Blalock-Kennedy-Pierce Professor Ben Blalock, Associate Professor Daniel Costinett, and Research Assistant Professor Ruirui Chen, all from the Min H. Kao Department of Electrical Engineering and Computer Science.


David Goddard, (865-974-0683​,