Wireless charging room delivers electricity over the AIR

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A wireless charging room has been developed by scientists that can deliver power through the air to any laptop, tablet or phone without the need for plugs or cables.

The new technology involves generating magnetic fields over longer distances without also producing electrical fields that would prove harmful to any people or animals within the room, according to the team from the University of Tokyo. 

The system can deliver up to 50 watts of power without exceeding current guidelines for human exposure to magnetic fields, the study authors explained.

It could be used to charge any device with a wire coil fitted inside, similar to the system used with wireless charging pads currently in use – but without the pad.

As well as removing bundles of charging cables from desks, the team say it could allow for more devices to be fully automated without the need for ports, plugs or cables. 

The current system includes a pole at the centre of the room to allow the magnetic fields to ‘reach every corner,’ but it will work without, the compromise is ‘dead spots’ where wireless charging isn’t possible, the team said. 

Researchers didn’t say what the technology might cost as it is still very early in development, but that it was ‘years away’.

When available it could be retrofit to an existing building or integrated into a brand new build, with or without the central conductive pole.

Other uses include a smaller version to power tools within a toolbox, or a larger version that could allow an entire factory to operate without cables. 

‘This really ups the power of the ubiquitous computing world – you could put a computer in anything without ever having to worry about charging or plugging in,’ said study co-author Alanson Sample from the University of Michigan. 

There are also clinical applications, according to Sample, who said heart implants currently require a wire from the pump to run through the body and into a socket. 

‘This could eliminate that,’ the author said, adding it would act to reduce the risk of infection by eliminating the wire completely, ‘reducing the risk of infection and improving patients’ quality of life.’

To demonstrate the new system, they installed the unique wireless charging infrastructure in a purpose-built aluminium ‘test room’ that was 10ft by 10ft.

They then used it to power lamps, fans and mobile phones that drew current from anywhere in the room, regardless of where furniture or people had been placed.  

The system is a major improvement over previous attempts at wireless charging, which used potentially harmful microwave radiation or required devices to be placed on dedicated charging pads, the researchers said. 

Instead, it uses a conductive surface on room walls and a conductive pole to generate magnetic fields, that devices can tap into when they need power.

Devices harness the magnetic field with wire coils, which can be integrated into electronics like mobile phones. 

The researchers say the system could easily be scaled up to larger structures such as factories or warehouses while still meeting existing safety guidelines for exposure to electromagnetic fields set by the US Federal Communications Commission (FCC).

‘Something like this would be easiest to implement in new construction, but I think retrofits will be possible as well,’ said Takuya Sasatani, a researcher at the University of Tokyo and the corresponding author on the study. 

‘Some commercial buildings, for example, already have metal support poles, and it should be possible to spray a conductive surface onto walls, perhaps similar to how textured ceilings are done.’

A key to making the system work, Sample said, was building a resonant structure that could deliver a room-size magnetic field while confining harmful electric fields, which can heat biological tissues.

The team’s solution used devices called lumped capacitors, that work on the lumped capacitance model – where thermal systems are reduced to discrete lumps.

The temperature difference inside each lump is negligible, and is already widely used in climate control systems for buildings.

Placed in wall cavities, the capacitors generate a magnetic field that resonates through the room, while trapping electric fields inside the capacitors themselves.

This overcomes a limitation of previous wireless power systems, which are limited to either delivering large amounts of power over a tiny distance of a few millimetres, or very small amounts of power over long distances which is harmful to humans.

The team also had to design a way to make sure their magnetic fields reached every corner of a room, eliminating any ‘dead spots’ where charging might not work.

Magnetic fields tend to travel in circular patterns, creating dead spots in a square room, and making it difficult to align precisely with the wire coils in a device. 

‘Drawing power over the air with a coil is a lot like catching butterflies with a net,’ Sample said, adding the trick is ‘to have as many butterflies as possible swirling around the room in as many directions as possible. 

By having multiple butterflies, or in this case multiple magnetic fields interacting, it doesn’t matter where the net is, or which way it is pointed – you’ll hit the target. 

To make that happen, the system generates two separate, 3D magnetic fields. 

One travels in a circle around the room’s central pole, while the other swirls in the corners, travelling between adjacent walls. 

This approach eliminates dead spots, enabling devices to draw power from anywhere in the space, according to Sample.

Tests with anatomical dummies showed that the system could deliver at least 50 watts of power to any location in the room without exceeding FCC guidelines for electromagnetic energy exposure. 

Sample said it’s likely, however, that it will be possible to deliver higher levels of power with further refinement of the system.

The researchers note that implementation of the system in commercial or residential settings is likely years away. 

They’re currently working to test the system in a building on the University of Michigan campus to see if it could be retrofit to an existing building. 

The findings have been published in the journal Nature Electronics.