Wireless charging is already a thing (in smartphones, for example), but scientists are working on the next level of this technology that could deliver power over greater distances and to moving objects, such as cars.

Imagine cruising down the road while your electric vehicle gets charged, or having a robot that doesn't lose battery life while it moves around a factory floor. That's the sort of potential behind the newly developed technology from a team at Stanford University.

If you're a long-time ScienceAlert reader, you may remember the same researchers first debuted the technology back in 2017. Now it's been made more efficient, more powerful, and more practical – so it can hopefully soon be moved out of the lab.

"This is a significant step toward a practical and efficient system for wirelessly recharging automobiles and robots, even when they are moving at high speeds," says electrical engineer Shanhui Fan.

"We would have to scale up the power to recharge a moving car, but I don't think that's a serious roadblock. For recharging robots, we're already within the range of practical usefulness."

Wireless electricity transfer relies on generating oscillating magnetic fields that can then cause electrons in a conductor to also oscillate at a particular frequency. However, that frequency is easily messed up if the device is moving. Your smartphone needs to be sitting perfectly still on its charging mat, for example.

What Stanford scientists did in 2017 was set up an amplifier and feedback resistor loop that could change the operating frequency as the receiving device moved. At that stage though, only 10 percent of the power moving through the system was transmitted.

Now, they've got it up to 92 percent. That huge boost in efficiency is down to a new 'switch mode' amplifier – a more precise solution, but a far more complex one, which is why it's taken the team another three years to develop it to a satisfactory level.

The basic idea is the same as it was in 2017 though: adjusting the resonating frequency coming from the charger as the device moves around. Right now the system can transmit 10W of power across a distance of up to 65 centimetres (nearly 26 inches), but the researchers say there's no reason why it can't be quickly scaled up.

An electric car would need hundreds of kilowatts to charge it, but the system outlined here is fast enough to provide it, if it were built into the road surface, for example. The only limitation would then be how quickly the car's batteries could absorb the power as the vehicle sped past.

Other potential uses are with robots that can be charged up by pads in the floor of the environments they're operating in, or with drones that can pass over roof surfaces during their journeys to stay charged up. There would be less need to return to the base to recharge, and the robots and drones wouldn't even need to stop.

That's still some way off, not least because the technology remains expensive to implement. It is now available though, at least in prototype, and the scientists say it all operates within frequencies that don't pose any danger to human health.

Being able to not only beam electricity wirelessly but also to beam it to a moving device could eventually revolutionise the way our gadgets work, and the way we travel.

"To harness the full benefits of wireless power delivery, it is important to develop an efficient and robust scheme that is capable of power delivery to a moving device," write the researchers in their published paper.

The research has been published in Nature Electronics.