What is wireless power transmission(WPT)?
History of WPT
Types of WPT
◦ Techniques to transfer energy wirelessly
Advantages and disadvantages
The transmission of power from one place to
another without using wires, cables or chords
But, the wireless power transmission is made
possible by using various technologies like
microwaves, lasers and EM waves
As per studies, most electrical energy transfer
is through wires.
Most of the energy loss is during
• On an average, more than 30%
• In India, it exceeds 40%
Wireless Power Transmission 4
History of WPT: Tesla’s Expt
In 1899, Sir Nikola Tesla
Proposed a method of Wireless
As it is in Radiative mode, most
of the Power was wasted and has
The efficient midrange power
transfer concept is Witricity. In
this model source and load are in
Magnetic resonance so there is no
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 which are mutually perpendicular to each
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.
A group of theoretical physicists at MIT came up with the idea to use
resonant induction to transmit power wirelessly led by Dr. Marin Soljacic.
“Resonance", a phenomenon that causes an object to vibrate when
energy of a certain frequency is applied.
The Rise Of The Fallen in 2007
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.
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.
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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.
Will it harm me?
Will it harm the environment?
Will it interfere with important
Need for battery is
Harmless, if field
Maintenance cost is
Field strengths have to be under safety levels
Initial cost is high
In RIC, tuning is difficult
High frequency signals must be the supply
Air ionization technique is not feasible
Transmission without wires- a reality
Low maintenance cost. But, high initial cost
Better than conventional wired transfer
Energy crisis can be decreased
In near future, world will be completely
Wireless Power Transmission
“Wireless Power Transmission”, Vol No.-
45, Electronics For U –August-2013
Peter Vaessen,” Wireless Power
Energy, September 2009
C.C. Leung, T.P. Chan, K.C. Lit, K.W. Tam
and Lee Yi Chow, “Wireless Power
Transmission and Charging Pad”
EFY posted articles on WPT.