Jason Lai (right) demonstrates previous milestone efficienciees to Bradley Fellow Parrish Ralston, who is characterizing fifth generation transistors for the FreedomCAR project.
Jason Lai, director of the Future Energy Research Center, is heading a $2.7 million effort to develop a power electronics inverter for the Department of Energy FreedomCAR project. The FreedomCar is a multi-year effort to develop technologies that enable the adoption of first gas/hybrid, then fuel cell/hybrid vehicles.
Lai's is the only university-based team of the five involved in the drive train development. The target for the project is to be able to run the entire drive train at 105 degrees Celsius at the cost of $8.50 per kW.
"With today's technology, it is practically impossible to run electronics at that temperature with a reasonable cost," he says. His goal is to develop the system that can run with consumer-grade silicon in order to keep the cost down. The other teams are using silicon carbide (SiC), which can handle the temperature, but is very expensive and has reliability issues, according to Lai. "A four-inch silicon wafer is $25 and a two-inch SiC wafer is $950. A three-inch SiC wafer is $5000," he says.
Lai's team is pursuing two key issues: soft switching technology and advanced power module packaging, which he is partnering with Powerex to develop. The Virginia Tech team is developing the soft- switching technology, trying to get the efficiency higher than 98.5 percent. "We can get it to 99 percent with the use of more silicon, which we don't want to do obviously for the economical reason."
Lai's team has previously achieved record-breaking efficiency on other projects, including a 97 percent efficient isolated DC-to-DC converter for fuel cells, developed in 2005. "If we cannot achieve the 98.5 efficiency, nobody can," he says. "That's why we won the project."