ABSTRACT: The technology used for wireless power transmission is known as witricity. Wireless power transmission is not a new idea, Nikola Tesla proposed theories of wireless power transmission in the late 1800s and early 1900s. Tesla's work was impressive, but it did not immediately lead to wide spread practical methods for wireless power transmission. Since then many researchers have developed several techniques for moving electricity over long distances without wires. Some exist only as theories or prototypes, but others are already in use. In 2006 researchers at Massachusetts Institute of Technology led by Marine Soijacic discovered an efficient way to transfer power between coils separated by a few meters. They have dubbed this technology as witricity . Witricity is based upon coupled resonant objects. Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while not interchanging the surroundings. The researchers demonstrate the ability to transfer 60W with approximately 40% efficiency over distance in excess of 2 meters. Currently the project is looking for power transmission in the range of 100watts. As witricity is in the development stage, lots of work is to be done in improving the range of power transmission and efficiency. 1.INTRODUCTION what it can make peoples lives easier, it can add a lot of clutter in the If we are particularly organized and good with tie wrap then also a few dusty power cord tangles around our home. We have even had to follow one particular cord through the seemingly impossible snarl to the outlet hoping that the plug pull will
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ABSTRACT:
The technology used for wireless power
transmission is known as witricity. Wireless
power transmission is not a new idea,
Nikola Tesla proposed theories of wireless
power transmission in the late 1800s and
early 1900s. Tesla's work was impressive,
but it did not immediately lead to wide
spread practical methods for wireless power
transmission. Since then many researchers
have developed several techniques for
moving electricity over long distances
without wires. Some exist only as theories or
prototypes, but others are already in use. In
2006 researchers at Massachusetts Institute
of Technology led by Marine Soijacic
discovered an efficient way to transfer
power between coils separated by a few
meters. They have dubbed this technology as
witricity
.
Witricity is based upon coupled resonant
objects. Two resonant objects of the same
resonant frequency tend to exchange energy
efficiently, while not interchanging the
surroundings. The researchers demonstrate
the ability to transfer 60W with
approximately 40% efficiency over distance
in excess of 2 meters. Currently the project
is looking for power transmission in the
range of 100watts. As witricity is in the
development stage, lots of work is to be
done in improving the range of power
transmission and efficiency.
1.INTRODUCTION
what it can make peoples lives easier, it can
add a lot of clutter in the If we are
particularly organized and good with tie
wrap then also a few dusty power cord
tangles around our home. We have even had
to follow one particular cord through the
seemingly impossible snarl to the outlet
hoping that the plug pull will be the right
one. This is one of the downfalls of
Fig.1:wireless electricity
electricity. While it can make people's
process. For these reasons, scientists have
tried to develop methods of wireless power
transmission that could cut the clutter or
lead to clean sources of electricity. Wireless
power transmission is not a new idea. Many
researchers developed several methods for
wireless power transmission. But witricity is
a new technology used for wireless power
transmission. By the use of this technology
transmission of electrical energy to remote
objects without wires can be possible. The
inventors of witricity are the researchers
from Massachusetts Institute of
Technology(MIT).
Fig.2:Expermiment on witricity
They developed a new technology for
wireless electricity transmission and this is
based upon the coupled resonant objects. In
this resonant magnetic fields are used. So
the wastage of power is reduced. The system
consists of witricity transmitters and
receivers. The transmitters and receivers
contain magnetic loop antennas made of
copper coils and they are tuned to the same
frequency.
2.HISTORY
While Tesla was the first person to demonstrate
the practical possibilities of wireless power in
1899, today, commercially there is little more
than electric toothbrushes and charger mats
available, and in both technologies the
toothbrush, phone, and other small devices
need to be extremely close to their chargers.
Wireless power transmission as an
alternative to transmission line power
distribution (our current system of electric
power distribution) was first proposed and
demonstrated by Nikola Tesla. In 1899,
Tesla demonstrated wireless power
Fig.3:fluorescent lamp
transmission by powering a field of
fluorescent lamps located twenty-five miles
from their power source without using
wires. As impressive and forward thinking
as Tesla's work was, at that time is was
actually cheaper to build coppertransmission
lines rather than build the type of power
generators that Tesla's experiments required.
Tesla ran out of research funding and at that
time a practical and cost efficient method of
wireless power distribution could not be
2
develoThis team from MIT belonged to the
Department of Physics, Department of
Electrical Engineering and Computer
Science and the Institute for Soldier
Nanotechnologies. The members of this
team were Andre Kurs, Aristeidis Karalis,
Prof. Peter Fisher, Robert Moffatt and Prof.
John Joannopoulos. The leader of this team
of researchers was Prof. Marin Soljacic.
fig.3:MITteam
It was Prof. Marin Soljacic who provided the
inspiration for the experiment and
invention of witricity. It was while standing
in the kitchen one night, that on staring at
his mobile phone that he had thought it
would be nice if his mobile phone would
take care of its own charging instead of him
having to periodically charge it.
He then tried out his experiment using two
coils of copper, where one was connected
to a receiver, and the other to a transmitter.
With the help of these two coils of copper,
the inventors of witricity managed to
transmit power across seven feet through
the air to instantly light up a lightbulb.
Though witricity worked only distances up
till 9 feet at its inception, the inventors
believed that it was possible to charge a
battery that was located at a distance of a
few yards from the power source that was
connected to the receiving coil. They state
that it would be sufficient to place a source
in each room to provide power to the whole
house.
3.WiTricity Technology: The Basics
The experimental design consisted of two
copper coils, each a self-resonant system.
One of the coils, connected to an AC power
supply, was the resonant source. The other
coil, the resonant capture device, was
connected to a 60 watt light bulb. The power
source and capture device were suspended in
mid-air with nylon thread, at distances that
ranged from a few centimeters to over 2.5
meters (8.2 ft). Not only was the light bulb
illuminated, but the theoretical predictions
of high efficiency over distance were proven
experimentally.
By placing various objects between the
source and capture device, the team
demonstrated how the magnetic near field
3
can transfer power through certain materials
and around metallic obstacles.
Thus Prof. Soljačić’s dream of finding a
method to wirelessly connect mobile electric
devices to the existing electric grid was
realized. WiTricity Corp. was soon launched
to carry this technology forward from the
MIT laboratories to commercial production.
Fig.4:witricity technology
3.1:Electricity: The flow of electrons (current)
through a conductor (like a wire), or charges
through the atmosphere (like lightning). A
convenient way for energy to get from one
place to another place
3.2:Magnetism: A fundamental force of
nature, which causes certain types of
materials to attract or repel each other.
Permanent magnets, like the ones on your
refrigerator and the earth’s magnetic field,
are examples of objects having constant
magnetic fields.
Fig.5:magnetism
Oscillating magnetic fields vary with time,
and can be generated by alternating current
(AC) flowing on a wire. The strength,
direction, and extent of magnetic fields are
often represented and visualized by
drawings of the magnetic field lines.
3.3:Electromagnetism: A term for the
interdependence of time-varying electric and
magnetic fields. For example, it turns out that
an oscillating magnetic field produces an
electric field and an oscillating electric field
produces a magnetic field.
Fig.6:Electro magnetism
As electric current, I, flows in a wire, it gives rise
6.A radio transmitter can produce waves having a power of several kilowatts or even megawatts but this energy scatters in all directions. Only a small fraction, less than a millionth part, of the transmitted energy is received. However, this is sufficient to yield the intelligence.
7.^ Jump up to: a b G. A. Landis, "Applications for Space Power by Laser Transmission," SPIE Optics, Electro-optics & Laser Conference, Los Angeles CA, 24–28 January 1994; Laser Power Beaming, SPIE Proceedings Vol. 2121, 252–255.
8. ^ Jump up to: a b Corum, K. L. and J. F. Corum, "Nikola Tesla and the Diameter of the Earth: A Discussion of One of the Many Modes of Operation of the Wardenclyffe Tower," 1996
9.^ Jump up to: a b c d e f General Electric review, Volume 15 By General Electric. "Velocity of Propagation of Electric Field", Charles Proteus Steinmetz
10.Jump up ̂ 188,000 miles per second
11.Jump up ̂ Such as an internal change of load, starting and switching operations, and short circuits.
12.Jump up ̂ Such as the external change due to lightning.
13.Jump up ̂ Charles Steinmetz (Fellow, A. I. E. E. Chief Consulting Engineer, General Electric Company, Schenectady, N. Y.). "Condenser
Discharge Through a General Gas Circuit". American Institute of Electrical Engineers., 1922. Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers. Presented at the 10th Midwinter Convention of the A. I. E. E., New York, N. Y., 15–17 February 1922.
11. Jump up ̂ viz., the dissipation of electric energy by the resistance of the conductor through its conversion into heat;
12. Jump up ̂ Such as when it gives trouble by induction in telephone circuits or when it reaches such high intensities as to puncture insulation, cause mechanical motion, etc.
13. Jump up ̂ such as an iron needle.
14. ^ Jump up to: a b c Theory and calculation of transient electric phenomena and oscillations By Charles Proteus Steinmetz
15.Jump up ̂ Speculation was made as to what
the electric wave was, leading to the
contradictory deductions that for certain
reasons space is considered as a gas of infinitely