Recently in Perm, Russia, a robot named P escaped from its laboratory on its own. Eventually, it ran out of battery and ended up in the middle of the street, causing a minor traffic jam.
For robots, a lack of power will prevent them from functioning properly. For many people addicted to their smartphones, a low battery can cause anxiety and frustration. This phenomenon is commonly referred to as "low battery anxiety."
To alleviate this "modern ailment," scientists are attempting to introduce wireless charging technology. But what exactly is this technology? Can it be widely adopted and truly alleviate "low battery anxiety"?
Traditional battery technology has relatively weak battery life.
"No matter how poor you are, you need WiFi; no matter how tough life is, you can't be without battery power." This "new version of Maslow's hierarchy of needs" circulating online clearly conveys the message in a humorous way: "low battery anxiety" has affected the basic living conditions of many people.
According to reports, LG conducted a survey of over 2,000 mobile phone users. The results showed that 90% of respondents were very concerned about the loss of their phone battery; 60% of respondents had experienced being unable to contact family, friends, or colleagues due to their phone running out of power; and 41% of respondents felt panicked when their phone ran out of power.
With battery technology offering relatively weak battery life, can wireless charging alleviate "low battery anxiety"?
In recent years, the core performance of smartphones has increased exponentially, but limited by existing lithium-ion battery technology and device space, weak battery life has become an insurmountable industry obstacle. To solve this problem, major mobile phone manufacturers have racked their brains, and the current common approach is to apply fast charging technology. For consumers, carrying a portable power bank is an important way to provide emergency charging.
However, scientists believe that with the development of wireless charging technology, consumers will be able to charge their devices anytime, anywhere, freeing them from the constraints of sockets and cables. For example, in cafes, offices, and homes, we can simply place our phones on the sensing area to charge; or, stepping into a bus, subway station, or even a movie theater is like entering an electromagnetic field, allowing our portable electronic devices to be "recharged" at will…
The American company Energous is turning this concept into reality. Researchers at the company are using radio frequency (RF) waves to provide point-to-point wireless power to devices within a 4.5-meter range. The transmitter is placed high up or in a corner of a room; when a device connected to a receiver enters the transmission range, the RF waves are focused to charge the device. The receiver locates the device via Wi-Fi and Bluetooth Low Energy and connects to the transmitter.
Experiments have shown that such a transmitter can simultaneously supply 2 watts of power to four devices within a 4.5-meter distance, while taking only half the time of traditional wired charging.
Magnetic resonance imaging enables "remote charging".
In 2014, Qualcomm showcased a wireless charging system for cars. This system uses a charging box to drive a wireless charging pad on the ground, and power transfer begins once a car drives onto it.
Experiments show that compared with traditional methods such as charging stations, wireless charging for electric vehicles can solve a series of problems such as sparks, dust accumulation, contact loss, and mechanical wear, while also enabling automatic charging in parking spaces and mobile power supply. This will reduce the requirements for battery capacity and enhance the driving range of electric vehicles.
Wireless charging technology is in huge demand not only in the consumer electronics sector but also shows promising application prospects in the new energy vehicle industry. So, what is its underlying principle?
More than 100 years ago, scientists discovered that electricity could be converted into electromagnetic waves that propagate through the air. At that time, scientists created two copper coils, one connected to a power source to generate energy, and the other connected to a light bulb to receive energy, with no wires connecting the two coils. Because the two coils had the same electromagnetic vibration frequency, electrical energy was successfully transmitted between them.
Wireless charging technology utilizes principles such as magnetic resonance and electromagnetic induction to transfer electrical energy between a charging transmitter and an electronic device. Based on the power transmission distance, it can be divided into three main categories: short-range, medium-range, and long-range transmission.
Short-range power transmission typically relies on electromagnetic induction. Electromagnetic induction power transmission primarily uses a magnetic field as a medium, inducing current through primary and secondary coils. It can transmit power through many non-metallic materials and is generally suitable for powering small, portable electronic devices. The maximum short-range transmission distance is 10 centimeters.
Mid-range transmission can be achieved through electromagnetic waves and radio frequency, with a transmission distance of up to 10 meters, but the transmission power is relatively small, and it is mostly used for supply support of automotive parts, hearing aids and implantable devices.
Long-distance power transmission primarily utilizes microwave or laser technology. Microwave transmission converts electrical energy into microwaves, which are then transmitted through free space to the target location and converted back into direct current to supply the load. Laser power transmission leverages the strong directionality and high energy carrying capacity of lasers to achieve power transmission over long distances.
Transmission distance and radiation limitation applications
Typically, when tech companies talk about wireless charging technology, they mean placing a phone on a charging pad to charge it, eliminating the need for a charging cable. For example, watches from brands like Apple and Huawei use inductive charging via contact between two coils to convert electrical energy. However, many people question the fundamental difference between this and charging with a data cable.
True wireless charging technology, similar to "air charging," transmits electrical energy through a medium like air, much like WiFi signals. Its energy transfer efficiency can be maintained at around 70%, and it employs intelligent control, automatically identifying whether the load is fully charged. This makes it more environmentally friendly and energy-efficient than traditional chargers that cannot detect charging completion. Therefore, its widespread adoption is promising.
However, transmission distance and radiation issues also limit the widespread application of wireless charging technology. The diffusion, absorption, and attenuation of radio waves are considered the challenges of wireless charging. When electromagnetic waves transmit energy in free space, they scatter in all directions, are difficult to concentrate, and have poor directionality; during wireless transmission, various interferences cause energy loss, especially microwaves, which diffuse in space, causing energy to deplete even faster.
Furthermore, products using wireless charging operate at frequencies between 50 Hz and 60 Hz, theoretically resulting in electromagnetic radiation comparable to that of ordinary small household appliances. However, tests have revealed that the electromagnetic radiation from wireless charging is significantly higher than that from wireless communication. Experts also point out that radiation isn't limited to wireless chargers; computers, mobile phones, Wi-Fi, televisions, and microwave ovens also emit radiation, creating a cumulative radiation problem. Therefore, while improving the transmission capabilities of wireless charging, it's crucial to reduce electromagnetic radiation levels to a safe and permissible range. This may be a major bottleneck in the development and application of wireless charging technology.
Testing of wireless charging systems for cars also revealed that the transmission of electrical energy via magnetic induction produces slight radiation. Among the human body's organs, the heart and lungs are most significantly affected and require special protection. However, due to the shielding effect of the car body and the rapid attenuation of electromagnetic parameters with distance, the electromagnetic safety indicators outside the car are significantly better than inside. Therefore, for individuals, it is best to avoid being in the central area of wireless charging. (Reporter Xia Bin)
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Ingenious wireless charging methods
The University of Washington is developing a "WiFi power system." This technology can charge devices within an 8.5-meter range using WiFi signals. Sensors receive electrical energy from the radio frequency signals and convert it into direct current.
A Brazilian designer has created a new device called AIRE mask that uses breath to charge mobile phones. It contains a small wind turbine that converts the wind energy generated by breathing into electrical energy.
Tribocharging utilizes the principle of electrostatics. A piece of nanomaterial the size of a fingernail can generate 8 milliwatts of electricity through friction, enough to power a pacemaker; rubbing 25 square centimeters of material is enough to light up 600 LED lights.
The sound-powered device is like a "sandwich," with zinc oxide nanotubes sandwiched in the middle by a specific compound. When external sound reaches the surface, the sound waves vibrate, causing the zinc oxide nanotubes to compress and expand, resulting in a minute voltage. Currently, this device can convert a sound level of about 100 decibels into a voltage of 50 millivolts.
IKEA has launched a range of home furnishings that support wireless charging. The most eye-catching items include table lamps, desks, bedside tables, and floor lamps. These pieces come with built-in wireless charging modules, allowing users to simply plug them into a power source and use them.
