In a paper published in Nature, Stanford University researchers have worked out how to transmit electric charges wirelessly to a nearby moving object. The team transmitted 1 milliwatt of charge – 10 million times less than what’s needed for operating an electric car – so it’s a small but promising step.
“We still need to significantly increase the amount of electricity being transferred to charge electric cars, but we may not need to push the distance too much more,” said Shanhui Fan, a professor of electrical engineering and senior author of the study, in a statement. “In addition to advancing the wireless charging of vehicles and personal devices like cellphones, our new technology may untether robotics in manufacturing, which also are on the move.”
The system is envisioned as the precursor for a charge-as-you-drive mode, where theoretically you’d never have to stop to recharge. Currently, you need several hours to fully recharge the batteries of an electric car.
The technology is based on an existing experiment on wireless charging, which was put together at the Massachusset Institute of Technology in 2007. The original set up was based on magnetic resonances. The electric charge is transmitted using an oscillating magnetic field. This set up requires the charging circuits to be in alignment and requires adjustment, done manually if either is moved.
It would be an impossible task for anyone to continuously fine-tune the system. So Stanford researchers added a commercially available voltage amplifier and feedback resistor. This tweak lets the system automatically adjust to changes without any human input.
“Adding the amplifier allows power to be very efficiently transferred across most of the three-foot range and despite the changing orientation of the receiving coil,” lead author Sid Assawaworrarit added. “This eliminates the need for automatic and continuous tuning of any aspect of the circuits.”
The key to more power might be in the amplifier itself. The team used an off-the-shelf piece of equipment with an efficiency of 10 percent. Custom-made amplifiers could have more than 90 percent efficiency.
“We can rethink how to deliver electricity not only to our cars, but to smaller devices on or in our bodies,” Fan said. “For anything that could benefit from dynamic, wireless charging, this is potentially very important.”
Currently, the Chevy Bolt can go over 380 kilometers (235 miles) on a single charge and the upcoming Tesla Model 3 will do about 320 kilometers (200 miles). And soon, we might not even care about these numbers.