The ability to
provide electrical
energy to remote objects without wires using oscillating magnetic fields.
The
term WiTricity was used for a project that took place at MIT,
led by Prof. Marin Soljačić
in 2007
WiTricity
is based on strong coupling between electromagnetic resonant objects to transfer energy
wirelessly between them. This differs from
other methods like simple induction, microwaves, or air ionization.
The
system consists of transmitters and receivers that contain magnetic loop
antennas critically tuned to the same frequency
Due
to operating in the electromagnetic near
field, the receiving devices must be
no more than about a quarter wavelength from the transmitter (which is a few
meters at the frequency used by the example system). In their first paper, the
group also simulated GHz dielectric resonators.
The WiTricity devices are coupled almost entirely with magnetic fields (the
electric fields are largely confined within capacitors inside the devices),
which is argued to make them safer than resonant energy transfer using electric
fields (most famously in Tesla coils,
whose high electric fields allow them to be used as lightning generators),
since most materials couple weakly to magnetic fields (Kurs,
2007)
History of Wireless Power:
àIn 1899, Sir Nikola Tesla Proposed a
method of Wireless Power Transmission.
à As
it is in Radiative mode, most of the Power was wasted and
has less efficiency.
à The efficient midrange power transfer concept is Witricity. In this model source and load are in Magnetic resonance so there is no power loss.
Need of Witricity:
Now
a days there is a Rapid development of autonomous electronics like Laptops, Cell-phones, House-hold robots and all those devices typically
rely on chemical energy storage(Battery)
As they are becoming daily needs to present generation, Wire less energy
transfer would be useful for many applications as above and they need midrange
energy.
Basic Principle:
The
basic principle involved in Witricity concept is, Two objects having same
resonating frequency and in Magnetic resonance at Strongly coupled regime tend
to exchange energy , while dissipating relatively little energy to the
extraneous off-resonant objects.
Experimental Design:
Our
experimental scheme consists of two Self-resonant coils. One coil (source coil)
is coupled inductively to an oscillating circuit; the other (device coil) is
coupled inductively to a resistive load. Self-resonant coils rely on the
interplay between distributed inductance and distributed capacitance to achieve
resonance.
Electrical Resonance
•Tendency
of a circuit system to oscillate at a maximum amplitude for a certain resonance
frequency.
•Likely
to occur when impedance between input and output is minimized.
•Increases
the strength of interaction between two related devices
•Natural
Frequency
f
=1/2p(LC)0.5
nTypes:
There
are 3 major types of wireless energy transfer:
• Short range; Inductive Coupling
• Medium range; Resonant Induction
• Long range; Electromagnetic Wave Power Transfer
• Short range; Inductive Coupling
• Medium range; Resonant Induction
• Long range; Electromagnetic Wave Power Transfer
1: SHORT
RANGE WIRELESS ENERGY TRANSMISSION: INDUCTIVE COUPLING
Inductive Coupling is a method for short range wireless energy transfer. Its range can vary, but it’s often very short. Because of its short range it usually is used when the device containing the receiver and the device containing the transmitter are touching Inductive coupling works on the principles of electromagnetism:
Inductive Coupling is a method for short range wireless energy transfer. Its range can vary, but it’s often very short. Because of its short range it usually is used when the device containing the receiver and the device containing the transmitter are touching Inductive coupling works on the principles of electromagnetism:
2: MEDIUM
RANGE WIRELESS ENERGY TRANSMISSION : RESONANT INDUCTION :
Resonant
induction still uses the same principles as magnetic induction (magnetic fields
to transfer current) , but it uses resonance to increase the range at which the
transfer can efficiently take place. “Resonance" is a phenomenon that
causes an object to vibrate when energy of a certain frequency is applied.
Everything resonates at a certain frequency, based on its shape and material.
Energy transfers easily between resonating objects. WiTricity
can transmit electricity wirelessly at 40% efficiency to about 7 feet.
3: Long
range; Electromagnetic Wave Power Transfer
Simulation model Using COMSOL:
Simulation Performance:
A
By the basic parameters, calculated
results and performance given with and Without the External object in between
the coils
Project…
There
are many projects of wireless energy transfer:
a) Haier wireless HDTV.
b) Apple wireless charger.
c) Car charging technology.
and many more…..
a) Haier
wireless TV….
Using
the wireless and efficient transmission technology to good effect, Haier has
developed a completely wireless HDTV. Employing WiTricity
and Wireless Home Digital Interface (WHDI), the HDTV is made to stream videos
over 100 feet. That’s some distance, when you’re talking of no wires at all,
b) Apple
wireless Charger….
An accurate and reliable wireless charging
concept is the requirement of the modern technology world. The leading
technology innovator Apple has been spending much time to develop an improved
method to recharge its devices wirelessly. That is why several of the company’s
recent patent applications were related to various kind of wireless charging
options
c) Car charging technology…
Toyota
and WiTricity
to develop new wireless charging tech that requires no contact and WiTricity’s
current technology is comparable to standard Level 2 fast charge technology,
providing up to 3.3 kilowatts of
How safe it is….
HOW
SAFE IS WITRICITY ?
Human beings or other objects placed between the transmitter and receiver do not hinder the transmission of power. However, does magnetic coupling or resonance coupling have any harmful effects on humans? MIT's researchers are quite confident that WiTricity's coupling resonance' is safe for humans. They say that the magnetic fields tend to interact very weakly with the biological tissues of the body, and so are not prone to cause any damage to any living beings.
Human beings or other objects placed between the transmitter and receiver do not hinder the transmission of power. However, does magnetic coupling or resonance coupling have any harmful effects on humans? MIT's researchers are quite confident that WiTricity's coupling resonance' is safe for humans. They say that the magnetic fields tend to interact very weakly with the biological tissues of the body, and so are not prone to cause any damage to any living beings.
Future…
MIT's
WiTricity
is only 40 to 45% efficient and according to Soljacic,
they have to be twice as efficient to compete with the traditional chemical
batteries. The team's next aim is to get a robotic vacuum or a laptop working,
charging devices placed anywhere in the room and even robots on factory floors.
The researchers are also currently working on the health issues related to this
concept and have said that in another three to five years time, they will come
up with a WiTricity
system for commercial use. WiTricity,
if successful will definitely change the way we live. Imagine cellphones,
laptops, digital camera's getting self charged! Wow! Let's hope the researchers
will be able to come up with the commercial system soon. Till then, we wait in
anticipation!
Advantages…
Safe, fairly efficient, good
range.
`Magnetic fields interact weakly with biological masses (humans), and energy is only transmitted between resonating objects. Efficiency can be increased with time; most of the 60% lost is from heat radiated from the coils. Theoretically one stationary coil in a room could power multiple devices with receiving coils. No more messy wires, and with widespread enough use it could even eliminate costly batteries.
`Magnetic fields interact weakly with biological masses (humans), and energy is only transmitted between resonating objects. Efficiency can be increased with time; most of the 60% lost is from heat radiated from the coils. Theoretically one stationary coil in a room could power multiple devices with receiving coils. No more messy wires, and with widespread enough use it could even eliminate costly batteries.
Limitations:
☼The resonance condition should be
satisfied and if any error exists, there is no possibility of power transfer.
☼ If
there is any possibility of very strong ferromagnetic material presence
causes low power transfer due to
radiation.
CONCLUSION
1:The
transmission of power without wires is not theory or a mere possibility, it
is now a reality. The electrical energy can
be economically transmitted without
wires to any terrestrial distance.
2: Wireless transmission of electricity have
tremendous merits like high transmission
integrity and Low Loss (90 – 97 %
efficient) and can be transmitted to any where
in the globe and eliminate the need for
an inefficient, costly, and capital intensive
grid of cables, towers, and substations.
3: The system would reduce the cost of
electrical energy used by the consumer and
get rid of the landscape of wires,
cables, and transmission towers. It has
negligible demerits like reactive power
which was found insignificant and
biologically compatible.
4: It has a tremendous economic impact
to human society.
