Wireless power supply for TV sets: how does that work?
By Andreas Roth
Translation by Siobhán Hayes28.10.2009, 09:34
Wireless power supply for electronic devices has long been a dream– not just for fans of electronic communication, but also as a practical sphere of activity for television technology. Although it will be more than a decade before this technology achieves long-term market readiness, it is already clear that wireless power supply has good prospects fort he future.
How does wireless power supply work at all?
The method behind wireless power supply is based on the principle of magnetic resonance, as it has been known for a long time. Thus, no-one is surprised that radio or television waves can secure wireless transfer of information. This is only possible because the information is coded in electromagnetic waves, for which the receiver devices provide suitable decoders. This principle of magnetic resonance can be applied to the use of other energy transfer options, as has been demonstrated over many years in several research laboratories and at international conferences.
Thus, in 2007, an American team of physicians wrote about "Wireless Power Transfer" using strong magnetic resonances in the well known and renowned Science Magazine: With magnetic resonance in a strongly coupled process, we were able to prove experimentally that it is possible to carry our efficient transfer of power across distances of up to eight times the radius diameter of the coil. We were able to run a 60-watt bulb with the transfer of electrical power at a 40 percent level of effectiveness and realized this at a distance of more than 2 metres between the power source and the power consumer. In the end, we were able to provide a quantitative model of the description of the power transfer.
Wireless transfer of electrical power is useful in those cases where instantaneous or continuous energy transfers are used in systems where no cables can be used for practical reasons; e.g. because laying the cables is inconvenient, dangerous or impossible. Here, it is then possible to make devices suitable for use in an environment where this was previously unthinkable. This starting point, which is currently still in its initial infant stages, will later be implementable in standard situations where today, cables must still be used fort he transfer of electricity.
Sony is already experimenting with the technology and can transmit an electrical power of 60 watts across a distance of half a metre. (Photo: Sony)
Transformers are important for the technology. Transformers are nothing other than voltage transformers such as those used in the power units of televisions or laptops. Transformers consist of two coils located close to each other. Here, too, power is transferred wirelessly, although the distance is very short. In order to increase this range by a considerable amount, it is necessary to use some complex strategies. These include special coils and magnetic resonance. These allow the distance to be increased to several metres, which is sufficient for many practical areas of application.
Magnetic resonance provides a strong magnetic coupling on both sides – both the transmitter and the receiver coil. The magnetic resonance effectively ensures that the energy transmitted by the transmitter in a particular direction in the room can only be absorbed by the receiver aerial.
In the research projects which are ongoing at present, only about 30 to 40 percent of the energy transmitted arrives at the receiver facilities. This would not be sufficient to ensure long-term implementation of the technology in practice, since the energy costs would be too high. However, work is being carried out using a range of technologies on increasing this quota to about 70 or 80 percent. This is still limited to one metre, but this would be sufficient for modern living space supply if the main power source can be placed in a central location.