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A research team including faculty and students from the College of Engineering and the Electric Power Research Institute has been selected as a finalist for the Little Box Challenge.

Sponsored by Google and the IEEE Power Electronics Society, the challenge carries a $1 million prize and seeks to improve upon the current design and size of inverters, which play a key role in everything from solar power to electric vehicles.

Because this area of research has so many real-world implications, EPRI became a key collaborator with UT’s team.

With the addition of more power from wind and solar sources, and the need to modernize bulk electric power systems, the industry has undertaken steps to increase reliability and efficiency.

Power semiconductor devices and electronic circuits are essential to controllable and resilient power systems and to the low-carbon generation technologies that will be the backbone of future power systems.

EPRI’s strategic Technology Innovation program for power electronics—which funds innovative ideas and technologies related to the electric grid—backed the project.

“Competing in this challenge presented us with an opportunity to address critical research and development needs in power electronics,” said Rick Langley, program manager for critical power at EPRI. “Our research has identified improved component packaging and mechanical design, enhanced thermal management and optimization, and highly efficient power converters as requirements to support meaningful evolution of the electric grid.”

Daniel Costinett, an assistant professor of electrical engineering at UT, said, “EPRI’s expertise complemented our own, allowing us to address all aspects of the design—electrical, mechanical, and thermal. Their support allowed our team to really dedicate itself to creating the best prototype possible in the short timeframe of the competition.”

Costinett and his team—which includes Professors Leon Tolbert and Fred Wang from the Department of Electrical Engineering and Computer Science and graduate students Chongwen Zhao, Brad Trento, Ling Jiang, and Bo Liu— worked to develop the smallest, most efficient two-kilowatt inverter possible.

The device they developed is about the size of a deck of index cards, a vast improvement over current inverter models, which the contest notes are “roughly the size of a picnic cooler.”

To reach this size, the team used new circuits and semiconductor materials, and spent thousands of hours designing and testing their prototype.

“I have been extremely impressed with the effort and dedication of all team members on this project,” said Costinett.

A key challenge for teams was neither size nor efficiency, but heat.

Costinett said inverters can produce a large amount of heat when performing their main task of switching direct current to alternating current.

“When you make a converter this small, it becomes very difficult to keep it from overheating,” he said. “Keeping the temperature below sixty degrees Celsius [140 Fahrenheit] required significant effort—both increasing the efficiency and improving the cooling system.”

That the team did so despite only being able to use fans that are about the size of a stack of six quarters highlights the challenges and intricacies of the work by UT and EPRI.

“They utilized advanced finite element and multiphysics computer models, 3-D printing, and rapid prototyping that led to a near-maximum efficiency heat transfer from the inverter’s internal components to the air entering and exiting the inverter enclosure,” said John Jansen, an EPRI technical executive. “The result is an inverter that achieves a tenfold increase in power density when compared to commercially available inverters.”

The team will find out how well that work has paid off when the eighteen finalists present their inverter prototypes for testing at the National Renewable Energy Laboratory in Golden, Colorado, on October 21.

From there, the field will be narrowed to a final pool of six, whose designs will undergo a second round of testing. The overall winner will be announced in January 2016.


David Goddard (865-974-0683,