Modern science, which is evolving every day, seems to be the one that is far away for us, but there are moments when such technology really hits in our lives. It is like when we are likely lose the way if we don’t have smartphone, when we check the arrival time of bus with smartphone while standing at the bus stop or when Smartphone arrange and combine the pictures from cloud storage according to the time and create videos for us. When we think about this, technologies we actually feel come from smartphone. This means that what we really need is a smartphone when we enjoy simple and convenient modern life.
Redemption for digital addicts, wireless charging technology
When we need to charge smartphone, which became a part of our body rather than a ‘machine’, we feel certain distance to it. It could be selfish to hope that Smartphone would be operated forever without charging as if it is a part of our body, but such endless desire could make us develop the technology. Therefore, the most important technology trend for us now is charging with no wire, that is, wireless charging. Then, when and how was this technology, which exactly reflects our desire for convenience to make ultra-high speed charging by just placing, developed?
Michael Faraday, discovered the principle of wireless charging (1791 - 1867)
Michael Faraday in England discovered the principle of wireless charging in 1831. It is commonly called as Faraday’s laws of induction and it is one of laws that could be the base of electric phenomenon. If you repeat keeping magnet close and away to the coil, the voltage occurs to this coil. In other words, voltage is generated only when the magnetic field changes over time. This is called as time-varying field. Faraday discovered the basic law of induction, but the one who strengthened the basics for wireless communications and transmission of wireless power through this law was Nikola Tesla, a scientist in Austria.
Nikola Tesla, dreaming of supplying electricity to whole world by wireless (1856 - 1943)
Nikola Tesla invested a lot of time and effort from 1890s to 1906 to make transmission of wireless power possible by creating high frequency with electricity, generating and receiving signal in the reception device and then again converting it into electricity. As a result, he succeeded to turn on the neon light which was dozens of centimeters away by sending wireless electricity. This principle, also called as non-contact charging method, utilized the Faraday’s law of induction. Let’s apply this to wireless charging technology that is close to our lives. When the current flows in the smartphone charger, the magnetic field flows around it, and when the magnetic field is generated and the smartphone is approached within the influence area of it, the smartphone is charged. He, who had made transmission of wireless power possible through continuous research and experiments, is known as the first scientist who achieved the wireless charging for the first time.
1990s, when the wireless charging technology was in full bloom
After Nikola Tesla’s realization of wireless charging, William C. Brown in the USA (1916 - 1999) succeeded in supplying wireless power to fuel-free helicopter by using 2.45GHz microwave in 1964. These researches led to the solar power satellite product of NASA (National Aeronautics and Space Administration) and the Ministry of Energy in 1979, starting full R&D. Since then, what progress has wireless charging technology made? Wireless charging which has been researched so far can be divided into three ways. They are magnetic induction, magnetic resonant and electromagnetic wave.
Three ways of wireless charging
Wireless charging with magnetic induction is for short distance and can be applied to mobile phones, laptops and an electric car. It is harmless to human body and very efficient. It is the closest way for us who usually charge smartphone. In 2008, Wireless Power Consortium (WPC) was launched to research this in 2008. WPC has established ‘Qi’, an international standard, in the field of wireless charging for personal electronics. Products certified by Qi can be safely and conveniently charged wirelessly anywhere in the world. Smartphone wireless charging feature is an example in which magnetic induction method is applied in most useful way. However, the drawback of magnetic induction method is that the transmission distance is very short so the charger and the device should be within a few mm distance.
Wireless charging with magnetic resonant is similar with magnetic induction, but it is for middle distance that covers up to 1-3m for charging. It is a technology that allows the energy to be transmitted only to the transmission unit which is designed with the same resonant frequency after generating the magnetic field that vibrates with resonant frequency in the coil of transmission unit since the resonant frequency of the first and second coil is the same. It has longer transmission distance of power than magnetic induction method and can charge multiple devices at the same time. The biggest drawback of this method, however, is that harmfulness to human body is not investigated clearly yet. So, even though the standard is established, there has been no significant progress in commercialization.
Wireless charging with electromagnetic wave is for long distance that can transmit up to tens of km. When transmission unit sends the electromagnetism, the reception unit receives the electromagnetic wave using rectenna and converts it into electricity. Since it can transmit the power over long distance without electrical wires, it can be used for remote-distance unmanned system or power transmission of renewable electric energy. However, it has fatal drawback that it is harmful to human body. So, further technology development is required to overcome this drawback.