1. WITRICITY:
A WORLD WITHOUT WIRES
SUBMITTED BY: SUBMITTED TO:
SATYAJIT MOHANTY Dr. ABHIMANYU MAHAPATRA
Regd. no- 0901106207 Dr. RANJAN KU JENA
2. TOPICS TO BE DISUSSED :
• WIRELESS POWER TRANSFER
•CONCEPT OF ELECTROMAGNETIC WAVE
•EVIDENCE FROM HISTORY
•MODES OF WPT TRANSMISSION
•WHAT IS WITRICITY
HOW IT IS DEVELOPED
RESONACE COUPLING (COUPLING RESONATOR)
COMPARISON WITH OTHER TECHNOLOGIES
APPLICATIONS
ADVANTAGES & DIS ADVANTAGES
3. WHAT IS WIRELESS POWER TRANSFER :
Efficient transmission of electric power from one
point to another through vacuum or without the use of
wire or any other substance. This is used for
applications where
continuous delivery of energy is needed, but
conventional wires are inconvenient, expensive or
impossible.
The power can be transmitted using
electromagnetic waves like microwaves, radio waves
or lasers.
5. CONCEPT OF ELECTROMAGNETIC WAVE:
When an electric current passes through a wire, there
is an electric field & magnetic field in the dielectric
surrounding the conductor .
The electric field of a circuit over which energy flows
has three main axes at right angles with leach other:
a. The magnetic field, concentric with the conductor.
b. The lines of electric force, radial to the conductor.
c. The power gradient, parallel to the conductor.
6. In a direct current circuit, the current is continuous &
the fields are constant . There is a condition of stress
in the space surrounding the conductor, which
represents stored electric and magnetic energy, just
as a compressed spring or a moving mass represents
stored energy.
In an alternating current circuit, the fields are
alternate; that is, with every half wave of current and
of voltage, the magnetic and the electric field start at
the conductor(primary) and run outwards into space
with the speed of light. Where these alternating fields
impinge on another conductor(secondary) & voltage
and current are induced. This is called
Electromagnetic induction.
7. Electromagnetic induction is proportional to the
intensity of the current and voltage in conductor &
frequency of field. The higher the frequency the
more is the inductive effects.
A high frequency current does not pass for long
distances along a conductor but rapidly transfers
its energy by induction to adjacent
conductors. The more rapidly the energy
decreases and the current dies down along the
circuit.
in electromagnetic wave radiation , flow of
electric energy comprises -phenomena inside of
the conductor and phenomena in the space
outside of the conductor .
9. Maxwell's theory of electromagnetism, published
in 1865 mentions electromagnetic waves moving at
the speed of light.
In 1886 Hertz performed a successful
experiment with pulsed wireless energy transfer.
He produced an apparatus that produced and
detected microwaves in the UHF region.
10. Tesla’s experiment : TESLA COIL
In1894 Nikola Tesla used resonant inductive
coupling, also known as "electro-dynamic
induction" to wirelessly light up phosphorescent
and incandescent lamps at the 35 South Fifth
Avenue laboratory.
1897 he patented a device called
high-voltage resonance transformer or
"Tesla coil” capable of producing
very high voltagesat high frequency.
In 1899 using pulsed wireless energy
managed to light 200 lamps, without wires, from 40
kilometers away by using an aerial tower callled
Wardenclyffe tower, which was meant to be a pilot
plant for his “World Wireless System” to broadcast
energy around the globe. The core facility was
never fully operational and was not completed due
to economic problems .
12. 1.Electrostatic induction or capacitive coupling
2.Electromagnetic radiation-beam powered antenna,
microwave radiation , laser radiation
3.Electrodynamic induction method or resonant
inductive coupling or witricity
13. Electrostatic induction:
It is the passage of electrical energy through a
dielectric. Here insulated terminals or plates
are elevated over a conducting ground plane.
The electric field is created by charging the
plates with a high potential, high frequency ac
power supply. The capacitance between two
terminals and a powered device form a voltage
divider . The electric energy transmitted by this
is utilized by wireless lamp.
14. MICROWAVE POWER TRANSMISSION:
power transmission through microwave is called far
field power transmission .
It is accomplished by 3 stages:
1. The electrical energy is transmitted towards receiver
by transmitting antenna which is supplied by a dc
energy
2. Propagating medium
3. Rectenna : the energy sent was received by a a
special designed antenna called Rectenna. “An
antenna comprising a mesh of dipoles and diodes for absorbing
microwave energy from a transmitter and converting it into
electric power.”
Microwaves radiation: 85% efficiency around 5km
across
(3.1 miles) ,95% of the beam will fall on the Rectenna.
16. Recent development has shown that power can be transmitted by laser wave
Microwave vs. Laser transmission
Microwave Laser
More developed Recently
High efficiency up developed
to 85% solid state lasers
Beams is far below allow efficient
the lethal levels of transfer of power
concentration even Range of 10% to
for a prolonged 20% efficiency
exposure within a few years
Cause interference Conform to limits
with satellite on eye and skin
communication damage
industry as 2.45
ghz.
17. WITRICITY
WiTricity ,is used for "wireless electricity” in which
wireless energy transfer includes resonant energy
transfer , 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 Marin Soljačić
in 2007.
18. Inductive Coupling:
It uses magnetic fields that is produced due to
current's movement through- wire. Bending the wire
into a coil amplifies the magnetic field. The more
loops the coil makes, the bigger the field will be.
This is the principle how a transformer works.
Using it an electric toothbrush recharged. It takes
three basic steps:
1. Current from the wall outlet flows through a coil
inside the charger, creating a magnetic field. In a
transformer, this coil is called the primary
winding.
2. When you place your toothbrush in the charger,
the magnetic field induces a current in another
coil, or secondary winding, which connects to
the battery.
3. This current recharges the battery.
19. Need of Resonant coupling
Non-resonant coupled inductors(transformers,)work
on the principle of inductive coupling is of short range
power transfer & requires a magnetic core. Over greater
distances the NRI Method is highly inefficient and
wastes the majority of the energy in resistive losses of
the primary coil.
Hence concept of resonant coupling comes where
two coils are tuned to a particular frequency called
resonating frequency & absorb optimal energy.
20. CONCEPT OF COUPLED RESONATOR :
For resonance coupling coupled resonator is used.
Here Two resonant objects of the same resonant
frequency tend to exchange energy efficiently, while
interacting weakly with extraneous off-resonant objects.
Coupled resonators operate in a strongly coupled
regime where energy transfer rate is substantially higher
than the rate at which they lose energy due to material
absorption and radiation. So energy transfer can be very
efficient.
This is use for wireless charging of devices
(mobile/laptop)
21. WiTricity Technology is Born
Experimental demonstration :
Two copper coils, each a self-resonant system. resonant source &
resonant capture device, connected to a 60 watt light bulb. The coils are
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 can transfer power through
certain materials and around metallic obstacles.
23. general principle:
If an ac is applied to a primary coil which is
capacitively loaded, the coil will 'ring', and form an
oscillating magnetic field. The energy will transfer back
and forth between the magnetic field in the inductor and
the electric field across the capacitor at the resonant
frequency. This oscillation will die away at a rate
determined by the gain-bandwidth (Q factor), mainly due
to resistive and radiative losses. However secondary
coil has to cut most of the field before loss, then most of
the energy can be transferred.
The primary coil forms a series RLC circuit, and
the Q factor for such a coil is:
For R=10 ohm,C=1 micro farad and L=10 mH, Q is given as 10.
Because the Q factor can be very high, (1000 with air cored coils) only
a small percentage of the field has to be coupled from one coil to the
other to achieve high efficiency.
24. Transmitter coils and circuitry
Unlike the multiple-layer secondary of a
non-resonant transformer, coils for this
purpose are single layer solenoids (to
minimize skin effect and give
improved Q) in parallel with a suitable
capacitor. Insulation absent, with spacers
of low permittivity, low loss materials
such as silk to minimize dielectric losses.
To progressively feed energy/power into
the primary coil with each cycle, Colpitts
oscillator is used
25. Receiver coils and circuitry
In receiver coil is connected to a
microchip. It provides capacitance
to give resonance & regulators to
provide suitable voltage.
The secondary receiver coil is of
same design & same tuning
frequency like primary . so offers
less impedance. So energy is
optimally absorbed.
To remove energy from the
secondary coil, different methods Receiver of a smartcard
can be used, the AC can be used
directly or rectified and a regulator
circuit can be used to generate DC
voltage.
26. FEATURES OF THIS COUPLING:
It is a near field effect . the wireless power
transmission concept based on strongly-coupled
resonator.
Time taken for energy transfer is less than the time of
loss . So high efficiency. Since the resonant wavelength
is much larger than the resonators, the field can
circumvent extraneous objects in the vicinity and no
need of line-of-sight.
This method is safe, since magnetic fields interact
weakly with living organisms.
27. Coupling coefficient:
The coupling coefficient is the fraction of the flux of
the primary that cuts the secondary coil, and is a
function of the geometry of the system. The coupling
coefficient is between 0 and 1.
a. Tight coupling coupling coefficient ~1 as with
conventional iron-core transformers.
b. Over coupling :secondary coil is so close that it
tends to collapse the primary's field . Critical
coupling is when the transfer in the pass band is
optimal.
c. Loose coupling coils are distant from each other,
most of the flux misses the secondary.
In Tesla CC=0.2 . At greater distances, for inductive
wireless power transmission, it may be < 0.01.
28. Comparison with other technologies:
In conventional transformers, for inductive transfer
efficiency around 80% at short range
in witricity tightly coupled conventional transformers
has efficiency around 90-95% .
In addition, where batteries need periodic
maintenance and replacement, resonant energy
transfer can be used instead. So pollution due to
Batteries during their construction and their disposal is
largely avoided.
29. Regulations and safety:
Shock prevention unlike wired connection cause
no direct connection.
The coupling is due to predominantly magnetic
field. so technology is safe up to <10 mhz
according to Safety standards and guidelines for
electromagnetic field exposures . This also
depends on transmitted power .
Deployed systems already generate magnetic
fields, for example induction
cookers and contactless smart card readers . But
they are proved not to be harmful.
30. APPLICATION:
Contactless smart card
High voltage (one million volt) sources for X-ray production
Tesla coils
Some Passports
recharging mobiles or computers ,tooth brush etc.
