With wireless transmission of electric power, irritating tasks such as replacing batteries or using a charger to recharge batteries will be drastically reduced. In some cases, it will be possible to dispense completely with power cords.
The cables that once restricted electronic equipment are gradually being rendered unnecessary by wireless communication technology, and as circuits shrink, only the power cords and huge batteries continue to chain mobile gear down. At last new technologies are appearing, providing the means to cut these final chains, offering completely wireless power supply and charging. Diverse commercial applications are expected from the second half of 2007.
Research into using wireless technology to supply power to terminals began about a century ago, when the first electronics technology appeared, and it is finally beginning to be realized. It entered limited use about a decade ago, and is expected to see widespread use in everyday applications like mobile phone handsets and portable music players from the second half of 2007 through 2008.
Non-contact
charging systems for mobile phones will go on sale in Europe in the
second quarter of 2007, for example (Fig 1). This charging technology
leaves a gap of a few millimeters between charger and handset, with no
metal pins in contact. Motorola Inc of the US and other firms in the US
are already developing mobile phones utilizing the technology. Apple
Inc of the US applied for a patent relating to a non-contact charger
for its iPhone, iPod portable music player and other products in
February 2007, pointing up the high level of interest in the industry.
In Japan, NTT DoCoMo Inc is actively developing similar technology,
with the first prototype mobile phone supporting wireless charging
developed in 2005. A variety of other technologies capable of pumping
power to terminals over ranges of several cm to several m have appeared
in addition to non-contact charging, with some of them expected to show
up in illumination products before the end of 2007.
Conditions Are
Right
These technologies are attracting so much attention from manufacturers
and researchers lately because of (1) market growth, (2) developments
in technology, and (3) delays in competing technologies (Fig 2). Market
growth here refers to the enormous surge in the quantity, variety, etc,
of battery-driven mobile phones. According to chief executive officer
(CEO) and founder John G Shearer of Powercast LLC of the US, which
developed one of the technologies in question, "Until about seven years
ago there was almost no really low-power equipment such as notebook
PCs, small mobile phones, digital cameras and portable music players
like we have now. It is only very recently that wireless power supply
has finally become a reality."
The key technological development involved in rapid progress is actually sending and receiving power without wires. For example, non-contact charging technologies in the past were only able to actually receive 10% to 20% of transmitted power, but in the last year or two this has been increased to 60% or more. A source at Seiko Epson Corp of Japan described the technology as "the same as an induction heating cooker" in principle, which means that excessive power loss translates to abnormal heating in the terminal. Even though companies wanted to apply the technology to mobile phones, which demand frequent charging, it simply wasn¡Çt possible. In addition to non-contact charging there are also technologies capable of beaming power to handsets at distances of up to about 10m, although only low voltages, and new wireless power supply technologies that haven¡Çt been used in actual applications yet.
At the same time, the widespread adoption of mobile terminals has brought the development of battery technology, a key competitor for wireless power supply, close to its limits. There has been little significant technical development in the last few years, and no dramatic increase in capacity is expected until fuel cells enter mainstream use. Even if the battery life per terminal remains the same, the increase in the number of terminals each person carries is leading to increased dissatisfaction with the time needed to charge them all.
Given this situation, many manufacturers, service providers and other firms are thinking about switching to wireless power supply, reducing the time and trouble needed for battery charging, replacement and other tasks, and perhaps even reducing battery sizes.
Wireless
Technologies
Wireless power supply technologies at present can be divided into three
groups according to their principle of operation (Fig 3). The first
non-contact technology achieving widespread adoption in many portable
terminals is electromagnetic induction. Two coils are brought close to
each other and when current is passed through one, the generated
magnetic flux causes electromotive force to be generated in the
other.
(Continue to the next page)
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