A new power transfer technology described recently in IEEE Transactions on Industrial Electronics, makes it possible to conveniently charge devices without using any wires or plugs. Using this technology, warehouse robots, kitchen appliances, phones, laptops and other devices can receive power anywhere within the charging area. And because the power transfer continues even while the device is in motion, this technology could one-day power electric vehicles while they’re on the go.
The basics of wireless power transfer have been in place for some time, but existing systems are not able to charge devices placed just anywhere within a large area. Using a single large transmitter to cover the entire area leads to unwanted electromagnetic exposure and means that the power flow to individual devices cannot be controlled.
If many small transmitters are used, the receiving devices must be in a known position, and the transmitter and receiver have to be precisely aligned. This means the system either has to use fixed charging locations or incorporate position sensors, communication protocols, and processing capabilities to track the location of each receiver. But now, researchers at Aalto University have developed a power transfer technology that works regardless of the position and orientation of the transmitter and receiver.
The key idea is to arrange the transmitters in a grid with the current in neighboring transmitters running in opposite directions — for example, a clockwise loop in one transmitter and counter-clockwise loops in its neighbors. This creates a chessboard-like grid of ‘positive’ and ‘negative’ transmitting coils with a magnetic flux between them.
A receiver above the grid of transmitters captures the magnetic flux between positive and negative transmitters, which generates an electric current to charge the device. The beauty of this method is that it’s very simple yet quite sophisticated. It doesn’t need a high-end processor or lots of computations to make the transmitters intelligent.
At the end of the day, it’s all an electromagnetic system, and the challenge was to figure out how to detect the receiver’s presence and position electromagnetically. Because the presence of a receiver triggers the power transfer, the system can work without any positional tracking and communication between the receivers and transmitters. This also means that power is only transferred to the receiver, rather than the entire area being energized, and it makes it possible for several devices to be charged simultaneously. Tiling transmitters together produces a charging area of the desired size and shape. A subset of the transmitters is then activated at lower power.
The transmitters are listening for a receiver. If power transfer to a receiver begins, the neighboring transmitters switch from being off into an alert mode, primed to transfer power if the receiver appears over them. With this configuration, the system achieves almost constant efficiency and constant power transfer, regardless of the receiver’s position and orientation, and the power transfer continued smoothly even as the receiving device moved around.
The project aims to commercialize this new technology for industry and transport. The technology has been tested with commercial warehouse robots in cooperation with Finnish firm Solteq Robotics. Although the technology is essentially ready for real-world applications, it still needs commercial packaging and certification.
In the meantime, the team will continue to refine and improve it. One of their goals is to boost the power levels from about 1 kW to around 20 kW so that the technology could be used to charge electric vehicles. There are already pilot projects for electrifying roads across the world, so electric vehicles are a really great application of this technology