When the Tesla Roadster went into production in 2008, users were promised a range of more than 210 miles per charge. More than a decade later, the upcoming version is almost three times as many as that promise. But even if you can afford this eye-popping price, it will take you some time to stop and recharge. Being able to charge batteries on the highway at any time would be a better way, and a new Stanford research project points the way.
Currently, wireless charging technology can already charge batteries for electric cars, but compatible cars still need to be parked on the charging plate and connected to a power supply. A magnetic field is generated between the power supply and the receiver, which resonates at the same frequency and transmits the power wirelessly in a small air gap.
The installation of wireless charging technology on the highway, so that the batteries of electric vehicles can be recharged while the car is driving on the highway, has been the subject of research for many years, but it is still a considerable subject. One of the issues that needs to be addressed is the adverse effect of the variable distance between the source and the receiver on charging efficiency.
Three years ago, Fan Shanhui, an electrical engineer at Stanford University, and a graduate student named Sid Assawaworrarit built a system that largely overcame the problem. By adding an amplifier and feedback resistor to the design, the operating frequency can be automatically adjusted as the distance between the charger and the moving object changes. Unfortunately, this version is considered too inefficient, unfit, requires a lot of power to operate, and only transfers about 10% of its electricity to moving objects.
In the new development, the researchers replaced the original design amplifier with a more efficient “switch mode” unit, then spent a long time patching the circuit, and finally came up with a configuration with a transmission efficiency of 92%. Although the prototype can only transmit 10 watts of power wirelessly from a distance of two to three feet, the team believes there are no barriers to preventing the system from expanding to wirelesspower to fast-moving vehicles.
This is an important step toward a practical and efficient wireless charging system that enables wireless charging even when cars and robots are moving at high speeds, says Mr Fan. We have to expand power if we want to charge a moving car, but I don’t think it’s a serious roadblock. We have finished charging the moving robot.
Electric cars are known to travel over a four-foot charging area at 70 mph to get wireless charging. Currently, the charging speed of a car’s battery is the only potential limit for this application.