Seeking: Ultra-Efficient Electric Vehicles

Friday, December 15, 2017

Speaking in 2017, Professor Umesh Mishra (Electrical and Computer Engineering) predicted that twenty years from then, twenty percent of all vehicles on the road would be electric. “When the price of solar panels dropped, solar energy took off,” he said. “When the price of batteries in electric vehicles (EVs) drops, they will take off, especially in Brazil, China, and India. EVs and the Internet of Things will be the biggest growth industries in electronics.” 

Mishra is taking a GaN–based approach to enhancing the efficiency of electric vehicles. He uses the Tesla as an example of an advanced technology that also embodies a main challenge — heat that results from inefficiency in its electrical system, which converts DC power to AC power. 

He explains that a 100-watt light bulb generates enough heat to burn your hand, and that ten times that — 100 kilowatts (kW) — is required to power a Tesla or other full-size EV sedan. The energy comes from the battery’s DC current, which is transformed into AC current to drive the motor. At today’s 95-percent efficiency, that process generates 5 kW of heat, which will cause parts of the car and the electronics to degrade if not managed effectively.

The current solution to all that heat is a large, heavy cooling system. But, Mishra explained, if it were possible to use GaN transistors to perform DC-to-AC conversion at, say, 99-percent efficiency and, thus, decrease the resulting heat, a car could be designed differently, with air cooling replacing water cooling. And that, Mishra says, would be a triple win: “The more-efficient battery creates more energy and less heat, which allows the cooling system to be smaller and lighter. That makes the car lighter, so it requires less energy to operate, further extending battery range.”

Mishra and his collaborators have achieved 99.5-percent efficiency in some EV sub-systems, an encouraging indicator that reaching the ambitious goal of a 99-percent-efficient system is on the horizon.

“The world is coming full circle,” Mishra says. “Some of the first automobiles were EVs. The advent of an efficient internal-combustion engine has driven the automotive industry for one-hundred-fifty years. Now, efficient power-conversion electronics that drive the motor are the modern-day internal-combustion engine. They ensure that the future will belong to the electric vehicle, with tremendous benefits to mankind in terms of reducing pollution and helping to bend the arc of climate change.”

Professor Umesh Mishra