Wireless charging anywhere in the room , Are you looking forward to ？
Wireless charging promises to free electronic devices from batteries and cables , But commercial systems are often limited to charging stations . In recent days, , A study by the University of Tokyo and the University of Michigan has brought new opportunities for wireless charging —— They have developed a method of Wireless Secure charging throughout the room . Can't help asking ： Will this be the ultimate form of wireless charging ？
At present , Wireless power transmission system is used to assist the charging of small electronic devices such as smart phones and electric toothbrushes . However , Most commercial systems that rely on magnetic fields require electronic equipment to remain stationary , And put it on or near the charging pad or charging base .
In terms of effect , The wireless power transmission strategy using microwave or other electromagnetic radiation can realize efficient charging over a long distance . however , Microwave based wireless charging may pose a potential safety hazard to biological tissues , And it requires a lot of antennas and complex mechanisms to track the device .
Special teaching assistant, Graduate School of engineering, University of Tokyo Takuya Sasatani And the professor Yoshihiro Kawahara、 Associate Professor, Department of electronic engineering and computer science, University of Michigan Alanson P. Sample Researchers have developed a way to safely turn a room into a wireless charging station . They said , This method can reduce the scale to create a small charging cabinet , It can also expand the scale and turn the whole plant workshop or building complex into a wireless charging area .
The study was published in 《 natural · Electronics 》 The journal .
Address of thesis ：https://www.nature.com/articles/s41928-021-00636-3
For the prospect of this wireless charging method ,Takuya Sasatani Express ：「 future , This method can also supply power to implantable medical devices . at present , Such devices face major challenges in power supply .」
Takuya Sasatani Wireless charging is available everywhere in the room
The researchers call the new technology 「 Multimode quasi-static cavity resonance 」（multimode quasistatic cavity resonance, M-QSCR）, It uses the conductive layer embedded in the wall of the whole room and the conductive column in the center of the room to generate 3D The magnetic field , The latter enables efficient interaction with small coil receivers attached to electronic devices .
The figure below 1 by M-QSCR Overview of Technology , among a Is the line current , Including transmitter and receiver ;b Is the surface current ;c It is multimodal ;d Based on M-QSCR Wireless power transmission system .
The figure below 2a It is the room level that enables the above current （room-scale） Resonator , chart 2b For the real scene of the wireless power transmission system .
Researchers at 3m×3m×2m Experiments were carried out in a specially built aluminum alloy test room , It turns out that ： No matter where people are or where furniture is placed , Researchers can work around the room for smartphones 、 Wireless charging of electronic devices such as bulbs and fans .
The figure below 5 Show room level wireless power transmission in living environment . among a Give the room an overview ,b A bulb for wireless charging ,c A smartphone that charges wirelessly ,d Removable fan for wireless charging .
Sasatani Express ：「 This technology can realize tens of watts of power transmission in any large volume , This cannot be safely achieved by other methods . also , Compared with the wireless charging board composed of coils , Our method makes the device have more freedom in position .」
at present , The receiver needs to maintain an appropriate angle with the magnetic field to achieve maximum charging efficiency , But the power transmission efficiency of all parts of the room and mobile devices can still exceed 37%.
What are the challenges ？ A key point for this method to run is to limit 「 Harmful electric fields that may harm biological tissues 」. The researchers placed a capacitor in the wall cavity , Thus, this structure can generate a magnetic field that resonates in the room , At the same time, the electric field inside the capacitor is captured .
Another challenge is to generate a magnetic field that can reach any corner of the room . This is because magnetic fields usually move in a circular way , Thus forming a dumb spot in an empty room （dead spot）.
To solve this problem , The researchers generated multiple 3D The magnetic field , One of them moves around the conductive column in the center of the room , Others coil around the corners of the room and move between adjacent walls , Successfully eliminated the blind spot .
Besides , Dummy safety tests show that ： The new wireless power transmission system can provide at least... To any corner of the room 50 Watt Power , And not beyond FCC and IEEE Electromagnetic field exposure limits . Researchers say , Through further adjustment , They can achieve higher power transmission .
The following figure is based on a specific absorption rate （specific absorption rate, SAR） Safety assessment of ,a by SAR A side view of the manikin used in the evaluation and its location inside the room level transmitter resonator ,b When the position of the manikin changes PI（pole-independent） Modal sum PD（pole-dependent） Modal input power limit ,c Is when the input power reaches the exposure limit SAR Distribution .
What improvements can be made in the future ？
Sasatani Also said ,「 There is an obvious disadvantage of our method —— The whole environment must be changed to make the system work .」 also , The safety assessment is still primitive , Therefore, they certainly need to conduct in-depth research on this subject .
In terms of the significance of this study , Both help to promote IoT application , Or for the family 、 Mobile robots in warehouses or other locations assist in charging .
Sasatani explains ,「 at present , Due to the cost of maintaining the battery , It's hard to deploy minicomputers anywhere . Our technology can omit the manual charging step , So as to become the driving force of power distribution for intelligent devices .」
In terms of the use scenario of this technology , Most easily implemented in new buildings , However, it is also possible to adapt the existing building structure to this charging mode . Researchers say , They are planning to explore the use of standard construction methods to build these systems , And if we can develop excellent conductive coatings in the future , Then they can also build the system by coating conductive materials on the wall .
Reference link ：https://spectrum.ieee.org/charging-rooms-can-power-devices-without-wires