Shajjad Chowdhury’s capacitor package is designed to take up less space and improve operational lifetime. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Novel Capacitor to Shrink Size & Reduce Cost of Electric Drives

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As a researcher in power electronics, Shajjad Chowdhury is focused on exceeding capacity. In a lab space at the Department of Energy’s National Transportation Research Center at Oak Ridge National Laboratory, he’s developing a novel capacitor and inverter component that will shrink the size and reduce the cost of electric drive units. He sees this as a potential step to increase electric vehicle adoption in the United States.

“The capacitor (which stores electrical energy) in an inverter (the circuitry that provides voltage) is generally large and restricts power density. A small, high-energy-density capacitor is necessary. If we can build one that takes up less space in the vehicle, but increases energy density and improves performance, that’s what we’re looking to accomplish,” Chowdhury said.

Chowdhury’s capacitor research is part of a larger project he’s leading for DOE’s Vehicle Technologies Office that focuses on developing an integrated drive system to achieve a high-power-density electric drive. Chowdhury is tasked with identifying, evaluating and integrating capacitor technologies. If successful, this research will be essential to meeting DOE’s technical target for light-duty electric vehicles, which is to reach a power density needed of 33 kilowatt liters for a 100-kilowatt traction drive system by 2025.

“The vehicle’s electric traction drive is the main user of stored energy,” Chowdhury said. “The drive system has to perform with high efficiency to maximize the vehicle range for the battery’s capacity.”

Chowdhury said future electric vehicles will need a high-performing, power-dense traction drive to extend electric vehicle range and increase market adoption.

“If we want more electric vehicles on the roadways, we also have to keep the vehicle cost down,” he added. “One thing that will help with cost is miniaturizing the whole electric train system; it’s about making the internal system more compact but more efficient overall.”

Gaining traction and attention

Chowdhury was chosen to work alongside senior researchers and to guide a critical DOE initiative because his accomplishments have led to patents, multiple journal publications and national and international attention from the power electronics research community.

“I’ve been working with scientists to develop new materials that can reduce the volume of electric vehicle components, looking at composite-based dielectric materials,” he said. “One of the things I am proudest of is that one day I received an inquiry from an esteemed Nobel Prize-winning scientist who read one of my papers and wanted to talk about emerging materials for next-generation power electronics and traction drives.”

Chowdhury said it’s this type of acknowledgement that, although unexpected, has been encouraging as his research progresses.

“It was a big deal to get the funding to explore these new materials and new ways of thinking about how a capacitor or electric drive can function,” he said. “When your role is to develop and build something, test it and then basically set a guideline for how others can mass produce it for commercialization, it’s a lot of responsibility and pressure. Getting that type of validation keeps you motivated.”

An artistic eye

Chowdhury’s ability to create and innovate as an electrical engineer grew out of an artistic aptitude. Growing up in Dhaka, the capital of Bangladesh, as the son of an engineer, Chowdhury had plans to follow a similar path. However, school exams almost steered him a different way.

“In school there, you take exams to determine your study path, and my exam scores put me in the arts field, not science,” he said. “I was really upset; I had to take an additional exam to place myself in the science program.” Chowdhury said he was good in both subjects, but one score was slightly higher than the other.

“The school testing experience was a life-changing moment for me,” he said. “I had to fight for the opportunity to study science. If I had not done that, my life would have been a different story.”

Chowdhury went on to study electrical and electronics engineering as an undergraduate at American International University in Bangladesh, where he received his degree in 2009. From there, he chose Liverpool John Moores University in the United Kingdom for his graduate studies, earning a degree in power and control engineering. In 2016, Chowdhury completed his doctoral degree in electrical and electronics engineering from the University of Nottingham in the U. K.

Global impact

While he continued to work at Nottingham after graduation as a research fellow concentrating on power electronics and electric drives, he kept his eye on opportunities to do similar research in a laboratory setting, the type of environment Chowdhury said he needed to support testing of his novel concepts.

“I was aware of Oak Ridge National Laboratory and its research in wireless charging through my father-in-law, who worked in the United States as an architect,” he said. “Then a friend from Nottingham, who I saw at a conference, was working at Oak Ridge in the same area I wanted to join. He told me there was a position open on his team, so I quickly applied, and in 2018 I became a researcher in electric drives here. Everything just quickly fell into place.”

Since then, Chowdhury said the lab has provided the right structure and resources to meet his research goals. While he’s been focused primarily on ground transportation, Chowdhury is also turning his attention to the sky.

“I’m looking at electrifying aircraft next. I worked on aircraft electrification when I was a part of an aerospace research team at Nottingham,” he said. “It’s going to be challenging because the risks are great; safety is critical. The rewards are great too, because if we can electrify aircraft, we’re further reducing carbon emissions throughout the world. That’s something I am really dedicated to, because I have a future generation I’m concerned about, and that includes my daughter. My research here can have a global impact, even reaching my family in Bangladesh.”

UT-Battelle manages ORNL for the Department of Energy’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit

Courtesy of Oak Ridge National Laboratory.

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