• The new research shows the properties of electric fields can be used to overcome significant limitations of more conventional systems that rely on magnetic resonance for wireless power transfer (WPT).
• The innovation could pave the for a wide range of applications in fields as diverse as medical implants and electric vehicles, while offering much greater flexibility and unprecedented energy efficiency.
Nikola Tesla is best remembered as the inventor of the polyphase current system and for his contribution regarding induction and other types of alternating-current machines. What is less well-known is that he also filed patents and published notes on worldwide wireless power distribution scheme: a technological dream which, if it were to come true now, would revolutionize the functioning of IoT both in the home and in the workplace and have major impact on industry, electronics and other sectors. Although global wireless power on a scale imagined by Tesla remains unlikely, Korean researchers at the Ulsan National Institute of Science and Technology (Unist) have recently developed an electrically resonant wireless power transfer (ERWPT) technology that is a step towards the Serbian-American engineer’s vision. Their innovation notably overcomes a major limitation inherent in conventional approaches based on magnetic fields to make wireless power a flexible, efficient and accessible option for a wide range of applications.
Nonradiative power transfer of up to 50 watts and 46% PTE over a distance of two metres
A persistent limitation of current technologies like magnetically resonant wireless power transfer (MRWPT) is that they are heavily reliant on the spatial alignment of transmitters and receivers, given that magnetic fields depend on two opposing poles to function. Magnetic field lines form closed loops, leaving a north pole to return to a south pole, which means that they need to be perfectly aligned. As the researchers point out in their article, “MRWPT encounters a challenge due to the absence of monopole magnetic properties, impacting power transfer efficiency (PTE) sensitivity to receiver arrangement.” It is a problem that prevents the development of practical applications for WPT in environments where alignment accuracy is difficult to guarantee.
An innovative approach based on ERWPT
To overcome this limitation, the researchers at Ulsan have developed a WPT technology that makes use of electric fields, which, unlike magnetic fields, can act as monopoles, a key advantage that eliminates the need for alignment. Their innovation, which utilizes an open bifilar coil functioning at a resonant frequency, has demonstrated unprecedented experimental results, achieving “nonradiative power transfer of up to 50 watts and 46% PTE over a distance of two metres.” This represents a significant gain over magnetic field-based systems which struggle to function at distances of one metre and are usually limited to a few dozen centimetres. At the same time, ERWPT is distinguished by a remarkable ability to remain effective even when the position of the receiver is varied laterally. Tests showed that “despite differences in load placement within the XY-plane, the system maintained consistent PTE over a distance of 2.05 metres.” However, alterations in the receiver’s position along the z-axis led to changes in resonance frequency and PTE, an area that could be improved in future applications.
Impact across several sectors
The unique capabilities of ERWPT could make it a game-changing technology in several fields.
- In healthcare, it should make it much easier to recharge medical implants without having to precisely align chargers and devices.
- It could also make it possible to provide a constant wireless power supply for electronic devices and to charge electric vehicles while they are on the move.
- In industry, it could also pave the way for the streamlining of complex processes that require multiple power sources, making it easier to design and implement production lines.
By exploiting the intrinsic properties of electric fields, this technology overcomes the historical obstacles of traditional magnetic field-based approaches to offer unrivalled energy efficiency and flexibility. As the authors of the research paper point out, “The freedom of receiver arrangement provided by ERWPT will open up new opportunities for efficient and adaptive wireless power.”
Ulsan National Institute of Science and Technology
