09-02-2021 | | By Sam Brown
Recently, Chinese tech giant Xiaomi demonstrated in a trailer of its Mi Air Charge Technology that can wirelessly charge devices in a room from several meters. What technology does the Mi Air Charge utilise, how much power can it deliver, and are such chargers a force for good or bad?
Recently, Xiaomi released a video that demonstrates their wireless charging system called Mi Air Charge. Up till now, wireless chargers have been based on bases that have built-in coils to provide devices with power via magnetic induction. However, the video demonstrates how the Mi Air Charge can deliver power wirelessly to devices in a room from several meters away.
According to Xiaomi, the system under development utilises 5 phased-array antennas to beamform sub-millimetre radio waves to devices. Receivers on devices can then convert this radio energy to electrical energy for charging their internal batteries. While adverts often contain misleading information (such as fake screens on devices), the video released by the Xiaomi does show devices charging while in the presence of the charging station.
The Mi Air Charge utilises 144 individual antennae on the charging station that provides the capability to beamform while 14 antennae on the receiving device are used to convert the incoming beam into electricity. The Mi Air Charge can provide up to a maximum of 5W per device, and charging of multiple devices is supported.
Furthermore, the use of intelligent tracking and processing means that objects in between the charging station and the device under charge do not interfere with the charging process. This may be due to the use of reflections and wave refraction around objects which are taken into consideration by the charging station.
Such a wireless charger has applications that go beyond simple charging of devices. Common household items that require power such as desk lamps, clocks, and controllers could all benefit from the Mi Air Charge. Reducing the number of devices directly connected to mains electricity not only provides convenience, but also safety (as high voltage electrics are separated from commonly handled devices).
The first question that some engineers may have when seeing the Mi Air Charge is if the device is in fact legitimate and not snake oil. Surprisingly, the device developed by Xiaomi does indeed work and can provide charging at a distance. However, there are a few facts that need to be considered around air charging in general as well as how Xiaomi announced their development.
Firstly, Xiaomi never released the video as a product announcement, but instead on their Twitter page as a message to their fans saying that they are working on such technology. Therefore, those who are waiting to purchase such a device may have a very long wait. The need for an integrated antenna in devices also raises the question regarding product support; such a charging system many only support Xiaomi devices (a company that is already finding itself in the middle of a trade war).
Secondly, wireless charging is not known for its efficiency, and wireless charging bases that have distances of a few mm are lucky to have a charging efficiency anywhere close to wired charging. While there are no figures released by Xiaomi regarding the energy efficiency of the Mi Air Charge, Dave Jones from EEVBlog mentioned that such a system would have to use “Wizz Bang” technology to be able to transmit 5W of energy at a distance of several meters from an input power of 500W.
Thirdly, the poor efficiency has a knock-on effect on its practicality as a product. Such a poor energy efficiency would have a seriously negative environmental impact with increased CO2 emissions (by orders of magnitude) per device charged. Furthermore, some government regulations such as those enforced by the EU do not allow devices with poor efficiencies in an attempt to reduce environmental impacts as well as reduce unnecessary electrical demand from the grid.
Overall, the development of the Mi Air Charge may be more of a concept as opposed to a real product, and I personally would not hold my breath for the Mi Air Charge to ever hit the shelves.