From left: Jason Dominic, Eric Faraci, and Thomas LaBella with their winning project.
A team of Virginia Tech electrical engineering students won the grand prize and the best efficiency award at the 2011 IEEE International Future Energy Challenge for their low cost lithium ion battery charger.
Every two years, the International Future Energy Challenge asks teams from universities around the world to develop the best device that meets the requirements for one of two specified topics. This year, teams chose between a battery charger for automotive and renewable energy applications (Topic A) and an induction motor drive system for emergency water treatment devices (Topic B).
Virginia Tech chose Topic A, competing against Huazhong University of Science and Technology (China), National Taiwan University of Science and Technology (Taiwan), Seoul Tech (South Korea), University of Connecticut, University of Kassel (Germany), and University of Peradeniya (Sri Lanka).
The goal for Topic A teams was to create a 3 kilowatt (kW) lithium ion battery charger with high efficiency, high power factor correction, low cost, small size, and safety features. Virginia Tech's team achieved greater than 94 percent efficiency even when delivering as much as 4kW. A battery charger that supplies more Watts (or kilowatts) will charge batteries more quickly. This charger is designed for lithium ion batteries that are much larger than those in our cellphones and laptops: standard overnight cellphone chargers supply less than 4W (1000W=1kW).
Advised by Kathleen Meehan, associate professor of Electrical and Computer Engineering (ECE) and Jason Lai, professor of ECE, more than 12 students worked on the project, mostly during the Spring 2011 semester. Three students completed the battery charger over the summer and took it to competition: Ph.D. candidate Thomas LaBella, and undergraduates Jason Dominic and Eric Faraci.
According to LaBella, "the main focus during the semester was the educational experience for the undergraduates. The majority of the work wasn't until the past month or so — before then it was a lot of theory." Even a week before the competition, the charger kept failing.
The first time the students were able to test their charger after transporting it from Blacksburg to Michigan was in front of the judges. "Going in, we were worried," Dominic says. "We just wanted it not to have broken during transportation."
"Once it was running, we knew we were good," adds Faraci.
Once the team proved that they could deliver 3kW, they were able to show that they could do even better: their charger could deliver 4kW as well. Dominic explains that they "didn't have to bring it up that high, but the judges wanted to see it, so we cranked it up. They didn't believe that we could do it."
"Compared to the other teams, we had tried a simpler approach for constructing our charger," Dominic observes. "We were focused on getting the power circuitry to work individually and together." During the Spring 2011 semester, they broke the project into three parts: the DC/DC component, Digital Signal Processing (DSP), and power factor correction. By the end of the semester, only the DC/DC portion was working. Fortunately, once each part was working independently, the team was able to combine them without any unexpected problems.
One challenge the group faced involved debugging one of their circuits. They were using oscilloscope probes to measure pins. "One time we tried measuring without the probe, and it turned out the probes were actually injecting noise into the device," Faraci explains. "So the debugging was causing the problem."
All three students enjoyed the hands-on experience and hope to find similar projects for next year. "There is so much here you won't learn in a classroom," says Dominic. "You have to take a lot into consideration."
Faraci agrees, saying that "simulations work great, but with power electronics that doesn't mean the PCB will. You can't ignore stuff like we do in the classroom — it's a big deal. You realize what is more and less important from the classroom learning. This is what we're going to college for."