Wireless power transfer achieved at 5-meter distance


April 17, 2014
Technology

The way electronic devices receive their power has changed tremendously over the past few decades, from wired to non-wired. Users today enjoy all kinds of wireless electronic gadgets including cell phones, mobile displays, tablet PCs, and even batteries. The Internet has also shifted from wired to wireless. Now, researchers and engineers are trying to remove the last remaining wires altogether by developing wireless power transfer technology.

Chun T. Rim, a professor of Nuclear & Quantum Engineering at KAIST, and his team showcased, on April 16, 2014 at the KAIST campus, Daejeon, Republic of Korea, a great improvement in the distance that electric power can travel wirelessly. They developed the “Dipole Coil Resonant System (DCRS)” for an extended range of inductive power transfer, up to 5 meters between transmitter and receiver coils.

Since MIT’s (Massachusetts Institute of Technology) introduction of the Coupled Magnetic Resonance System (CMRS) in 2007, which used a magnetic field to transfer energy for a distance of 2.1 meters, the development of long-distance wireless power transfer has attracted much attention for further research.

However, in terms of extending the distance of wireless power, CMRS, for example, has revealed technical limitations to commercialization that are yet to be solved: a rather complicated coil structure (composed of four coils for input, transmission, reception, and load); bulky-size resonant coils; high frequency (in a range of 10 MHz) required to resonate the transmitter and receiver coils, which results in low transfer efficiency; and a high Q factor of 2,000 that makes the resonant coils very sensitive to surroundings such as temperature, humidity, and human proximity.

Professor Rim proposed a meaningful solution to these problems through DCRS, an optimally designed coil structure that has two magnetic dipole coils, a primary one to induce a magnetic field and a secondary to receive electric power. Unlike the large and thick loop-shaped air coils built in CMRS, the KAIST research team used compact ferrite core rods with windings at their centers. The high frequency AC current of the primary winding generates a magnetic field, and then the linkage magnetic flux induces the voltage at the secondary winding.

Scalable and slim with a size of 3 m in length, 10 cm in width, and 20 cm in height, DCRS is significantly smaller than CMRS. The system has a low Q factor of 100, showing 20 times stronger against the environment changes, and works well at a low frequency of 100 kHz. The team conducted several experiments and achieved promising results: for instance, under the operation of 20 kHz, the maximum output power was 1,403 W at a 3-meter distance, 471 W at 4-meter, and 209 W at 5-meter. For 100 W of electric power transfer, the overall system power efficiency was 36.9% at 3 meters, 18.7% at 4 meters, and 9.2% at 5 meters.

“With DCRS,” Professor Rim said, “a large LED TV as well as three 40 W-fans can be powered from a 5-meter distance.”

“Our technology proved the possibility of a new remote power delivery mechanism that has never been tried at such a long distance. Although the long-range wireless power transfer is still in an early stage of commercialization and quite costly to implement, we believe that this is the right direction for electric power to be supplied in the future. Just like we see Wi-Fi zones everywhere today, we will eventually have many Wi-Power zones at such places as restaurants and streets that provide electric power wirelessly to electronic devices. We will use all the devices anywhere without tangled wires attached and anytime without worrying about charging their batteries.”

Professor Rim’s team completed a research project with the Korea Hydro & Nuclear Power Co., Ltd in March this year to remotely supply electric power to essential instrumentation and control equipment at a nuclear power plant in order to properly respond to an emergency like the one happened at the Fukushima Daiichi nuclear plant. They succeeded to transfer 10 W of electricity to the plant that was located 7 meters away from the power base.



Wireless power transfer achieved at 5 meter distance

3 Responses to Wireless power transfer achieved at 5-meter distance

  1. Nkululeko (14141036) May 5, 2014 at 5:29 am #

    Wireless technology is one of the best ways in which electronic devices have improved, who ever imagined a electronic device with no wire or cable to irritate you. This has made life much easier because we are able to connect with each other or share data with someone who is in much further distance than you are. Wireless technology is a few steps into the future.

  2. u14154847 May 3, 2014 at 4:33 am #

    The advancements in wireless technology has gone forth in leaps and bounds. The idea that we could power a room with no cables is awesome and hard to believe yet the technology to do it is just around the corner. I agree with Mahlatse with regards to the fact that air is nowhere near suitable to carry current yet we have found a way to power objects 5 meters away! However, this leads me to believe there could be a problem to this.

    On the one hand, it may reduce production and costs of cables and pylons etc. yet, with an efficiency of only 9.2% at the maximum 5 meter range, it leads me to think that surely it is a huge waste of energy. At this point in time, the world is looking to countless alternative energy sources and looking for the most efficient way in which to utilize the energy it does have, and the amount of energy ‘lost’ while it travels through the air would surely not be ideal for the energy companies?

    Additional to this, there is already new evidence found all the time proving that all these waves and energies traveling through the air are detrimental to our health. I am not sure weather or not this will be the case will the electrons but if they were to discover that it is in fact detrimental then the entire ‘wireless energy’ industry would come down. So have we done all that we can to prove its safe to be in our environment?

  3. Mahlatse_Moganedi_13304870 April 27, 2014 at 7:03 am #

    The research findings on wireless power transmission from MIT opened the way to think of electric current more as a signal with a characteristics similar to that of an electromagnetic waves. Classically an electric current is known to flow in a dense medium with a significantly large concentration of outer electrons as the charges are carried by the electrons, but now this shows that current can also propagate through a less dense medium which is gas. This shows that the goal will be achieved in the near future and will definitely save the inhabitants of this world from quite a lot of demands and environmental damages caused by pilon installation.

    On the other hand I think air has more resistance compared to metal which might be a drawback in this innovation because a charge can’t necessarily be taken as a massless unit like internet or telephone signal. I don’t fully understand , can someone please clarify these for me ?

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