Magnetic field technology transfers enough electricity to power a transit bus for up to 30 minutes.
The next-generation of electric vehicle technology was on display last week, as Utah State University (USU) rolled out a wirelessly charged electric transit bus.
Dubbed the “Aggie Bus,” the 22-foot vehicle powers-up by sitting over charging pads embedded in the roadway. Through a magnetic field, the bus receives 25 kilowatts of energy — enough power to drive approximately 30 miles before needing a recharge.
For the initial demonstration held on Thursday, Nov. 15, researchers charged the bus in a garage-like laboratory with an above-ground charging pad, and then took university and media passengers on a short ride.
Officials tout the Aggie Bus as the first bus to receive wireless energy of up to 25 kilowatts with more than 90 percent efficiency over an air gap of six inches. That gap includes roadway materials such as asphalt.
From a consumer perspective, the system is similar to rechargeable pads that mobile devices sit on to wirelessly recharge. But in this case, the device could sit on a shelf above the pad and still receive power.
The idea is that eventually, a public transit bus could charge up, go on its route and, every time it stops to pick up passengers, it would sit above an in-ground charging pad that would recharge the vehicle.
If it works as planned, the technology could set the stage for a viable form of non-fossil fuel power. Some work still needs to be done before you’ll see big city transit authorities adopting the technology, however. Researchers must still test various forums of surface materials to determine which are the most conducive to charging, and they need to increase the height of the air gap. But officials believe the question is now a matter of “when” rather than “if.”
Dr. Hunter Wu, director of USU Commercial Product Development, and the lead research scientist on the project, said the demonstration was meant to validate inductive charging technology and prove that wireless charging would work. The next step will to be to install a charging pad in the ground at USU and test various road surfaces to see which shows the best power transfer efficiency.
Wu and his team of scientists developed the wireless power transfer technology over the past couple of years. Last year a 5 kilowatt system was perfected, transferring energy over an air gap of 10 inches, including concrete. Now that a 25 kilowatt system has proved successful, a 50 kilowatt system is under development, which will contain multiple charging pads.
Once complete, the 50 kilowatt system and transit bus will be featured at the University of Utah in Salt Lake City. The Aggie Bus will be used to test the more powerful system, but a 40-foot bus will be used on a regular bus route at the school.
The project is being financed through a $2.7 million Federal Transit Administration grant.
When interviewed by Government Technology last year, Eric Warren, director of public relations for the Utah State University Research Foundation, explained that the decision to have the bus operate at the University of Utah was due to maximizing exposure in the state’s capital city.
Safety & Security Concerns
The National Cancer Institute said studies of electric and magnetic fields (EMFs) have shown only limited evidence that magnetic fields can cause cancer. But the health risks regarding magnetic fields have been debated for years. Wu explained he and his team are applying the standard outlined by the International Commission on Non-Ionizing Radiation Protection, which was adopted out of 50 years of studies and thousands of research experiments.
“To give you an idea how small the field we’re talking about is, at our frequency, we’re at a tenth of the Earth's own magnetic field,” Wu said. “That’s how small it is. We make sure anybody standing next to the bus beyond the chassis can’t be possibly exposed to a high field.”
The charging system is controlled over a wireless computer network. Wu explained that while he has “much less data” on whether the system can be hacked or not, his team designed the system with security in mind, and it operates on frequency bands that are “extremely rare” and not accessible by consumer devices.
“We don’t operate at Wi-Fi frequencies where people can potentially see we’re transmitting things,” Wu said. “We’re using our own proprietary protocol and everything is encrypted. We’re doing our best to make sure the wireless communication is safe and un-hackable.”
Photo courtesy of Donna Barry and Utah State University