Wireless Power Transmission Paper (WPT) (IEEE review paper) Subhash Mahla (S.M.5486956)

1. 1
Wireless Power Transmission: A Review
Subhash Mahla & Akash Sharma
Electrical Engineering Department
Baldev Ram Mirdha Institute of Technology, Jaipur
subhashmahla93@gmail.com
akashsir17896@gmail.com
Abstract—The aim of this paper is to give a overview of
recent researches and development in the field of wireless power
transmission. Generally, the power is transmitted through wires.
In present time every person needs wireless system, but still
power transmission for low power device using wired device
continuous power supply is one of the major issues in the purpose
of the application of wireless sensor network. Imagine a future
in which wireless power transfer is feasible for cell phones,
household robots, MP3 players, laptop computers and other
portable electronics capable of charging themselves without ever
being plugged in therefore presenting the concept of transmitting
power without using wires i.e. transmitting power as microwaves
from one place to another is in order to reduce the cost ,
transmission and distribution losses to increase efficiency. This
article introducing an idea that is discussed here about how
electrical energy can be transmitted without wire. Typical WPT
is a point to point power transmission.
Index Terms—Nikola Tesla Experiment, Microwave Power
Transmission (MPT), Wireless Power Transmission (WPT), Power
Transmission, Tesla Coil.
I. INTRODUCTION
In the past, product designers and engineers have faced
challenges involving power: the continuity of supplied power,
recharging batteries, optimizing the location of sensors, and
dealing with rotating or moving joints. Although those chal-
lenges remain, new demands that arise from increased use of
mobile devices and operation in dirty or wet environments
mean that designers require new approaches to supplying
power to equipment. Wireless Power Transmission from the
time of Tesla has been an underdeveloped technology. Tesla
had always tried to introduce worldwide wireless power dis-
tribution system. But due to lack of funding and technology
of that time, he was not able to complete the task.
Wireless power transfer (WPT) is the transmission of elec-
trical power from a power source to a consuming device
without using discrete man-made conductors. The situation of
wireless power transmission is different from that of wireless
telecommunications, like radio. The most common form of
wireless power transmission is completed using direct induc-
tion and then resonant magnetic induction. Other methods un-
der consideration include radio waves such as microwaves or
beam of light technology. Wireless communication is mostly
regarded as a branch of telecommunications.
II. LITERATURE SURVEY
• In 1864, James C. Maxwell predicted the existence of
radio waves by means of mathematical model.
Fig. 1: Tesla Coil
• In 1884, John H. Poynting realized that the Poynting
Vector would play an important role in quantifying the
electromagnetic energy.
• In 1888, bolstered by Maxwell’s theory, Heinrich Hertz
first succeeded in showing experimental evidence of radio
waves by his spark-gap radio transmitter. The prediction
and Evidence of the radio wave in the end of 19th century
was start of the wireless power transmission.[1]
• Nikola Tesla has been the pioneer in the field of wireless
transmission of electrical power [2]. He started efforts
on wireless transmission at 1891 in his experimental
station at Colorado. Nikola Tesla successfully lighted a
small incandescent lamp by means of a resonant circuit
grounded on one end. A coil outside laboratory with the
lower end connected to the ground and the upper end
free. The lamp is lighted by the current induced in the
three turns of wire wound around the lower end of the
coil.
Fig. 2: Nikola Tesla
III. NEED FOR WIRELESS POWER TRANSMISSION
Wireless transmission is employed in cases where instanta-
neous or continuous energy transfer is needed, but intercon-
necting wires are inconvenient, hazardous, or impossible.

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Fig. 3: Complexity of Transmission Wires
Number of household points receives electricity at the same
frequency using single transmitting coil as long as they all are
at resonance. So this setup could recharge all the devices in a
room at once.
Fig. 4: Number of Devices Charging at Single Plug Point
IV. METHODS OF WIRELESS TRANSMISSION OF
ELECTRICAL POWER
A. Induction
The principle of mutual induction between two coils can be
used for the transfer of electrical power without any physical
contact in between. The simplest example of how mutual
induction works is the transformer, where there is no physical
contact between the primary and the secondary coils. The
transfer of energy takes place due to electromagnetic coupling
between the two coils.[3]
B. Electromagnetic Transmission
Electromagnetic waves can also be used to transfer power
without wires. By converting electricity into light, such as a
laser beam, then firing this beam at a receiving target, such
as a solar cell on a small aircraft, power can be beamed to a
single target. This is generally known as power beaming.[4]
C. Evanescent Wave Coupling
Researchers at MIT believe they have discovered a new way
to wirelessly transfer power using non-radiative electromag-
netic energy resonant tunnelling. Since the electromagnetic
waves would tunnel, they would not propagate through the air
to be absorbed or wasted, and would not disrupt electronic
devices or cause physical injury like microwave or radio
transmission[5]. Researchers anticipate up to 5 meters of
range.
D. Electrodynamic Induction
Also known as ”resonant inductive coupling” resolves the
main problem associated with non-resonant inductive coupling
for wireless energy transfer; specifically, the dependence of
efficiency on transmission distance. When resonant coupling
is used the transmitter and receiver inductors are tuned to a
mutual frequency and the drive current is modified from a
sinusoidal to a non-sinusoidal transient waveform. Pulse power
transfer occurs over multiple cycles. In this way significant
power may be transmitted over a distance of up to a few times
the size of the transmitter.[6]
E. Radio and Microwave
Power transmission via radio waves can be made more
directional, allowing longer distance power beaming, with
shorter wavelengths of electromagnetic radiation, typically in
the microwave range. A rectenna may be used to convert the
microwave energy back into electricity. Rectenna conversion
efficiencies exceeding 95% have been realized. Power beaming
using microwaves has been proposed for the transmission
of energy from orbiting solar power satellites to Earth and
the beaming of power to spacecraft leaving orbit has been
considered.[7]
F. Electrostatic Induction
Also known as ”capacitive coupling” is an electric field
gradient or differential capacitance between two elevated elec-
trodes over a conducting ground plane for wireless energy
transmission involving high frequency alternating current po-
tential differences transmitted between two plates or nodes.[8]
V. CLASSIFICATION OF WPT
These techniques are briefly classified into three depending
on the distance between the transmitter and receiver. These
are: Short range, Moderate range and Long range.
A. Short distance induction
These methods can reach at most a few centimetres The
action of an electrical transformer is the simplest instance of
wireless energy transfer. The primary and secondary circuits
of a transformer are electrically isolated from each other. The
transfer of energy takes place by electromagnetic coupling
through a process known as mutual induction. (An added
benefit is the capability to step the primary voltage either up
or down.) The electric toothbrush charger is an example of
how this principle can be used.[9]
B. Moderate distance
Household devices produce relatively small magnetic fields.
For this reason, chargers hold devices at the distance necessary
to induce a current, which can only happen if the coils are
close together. A larger, stronger field could induce current
from farther away, but the process would be extremely ineffi-
cient. Since a magnetic field spreads in all directions, making
a larger one would waste a lot of energy. An efficient way

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Fig. 5: A Splashpower mat uses induction to recharge
multiple devices simultaneously
to transfer power between coils separated by a few meters is
that we could extend the distance between the coils by adding
resonance to the equation [10]. A good way to understand
resonance is to think of it in terms of sound. An object’s
physical structure – like the size and shape of a trumpet –
determines the frequency at which it naturally vibrates. This
is its resonant frequency. It’s easy to get objects to vibrate at
their resonant frequency and difficult to get them to vibrate
at other frequencies. This is why playing a trumpet can cause
a nearby trumpet to begin to vibrate. Both trumpets have the
same resonant frequency.
A capacitance plate, which can hold a charge, attaches to
each end of the coil. As electricity travels through this coil,
the coil begins to resonate. Its resonant frequency is a product
of the inductance of the coil and the capacitance of the plates.
Fig. 6: The wireless power project uses a curved coil and
capacitive plates
C. Long-distance Wireless Power
Whether or not it incorporates resonance, induction gen-
erally sends power over relatively short distances. But some
plans for wireless power involve moving electricity over a span
of miles. A few proposals even involve sending power to the
Earth from space. In the 1980s, Canada’s Communications
Research Centre created a small airplane that could run off
power beamed from the Earth. The unmanned plane, called
the Stationary High Altitude Relay Platform (SHARP), was
designed as a communications relay. Rather flying from point
to point, the SHARP could fly in circles two kilometres in
diameter at an altitude of about 13 miles (21 kilometres). Most
importantly, the aircraft could fly for months at a time.[11]
VI. ADVANTAGES AND DISADVANTAGES
Some of the advantages are as follows:
1) Various ways of transmitting power wirelessly have been
famous for centuries. The most widely known example
is non-particulate radiation, for example radio waves.
While such radiation is extremely good for wireless
transmission of knowledge, it’s not at all feasible to
apply it for power transmission. Since radiation spreads
in all directions, a massive tastes power would become
wasted into free space.
2) Wireless Power Transmission system would completely
eliminates the previous high-tension power transmis-
sion line cables, towers and sub stations involving the
generating station and consumers and facilitates the
interconnection of electrical generation plants with a
global scale.
3) It’s more freedom of both receiver and transmitters. Even
mobile transmitters and receivers might be chosen to the
WPT system.
4) The power could possibly be transmitted towards places
the location where the wired transmission isn’t feasible.
Decrease of transmission is negligible level from the
Wireless Power Transmission; therefore, the efficiency
with this way is a lot higher than the wired transmission.
5) Power can be purchased with the rectenna provided
that the WPT is operating. The power failure because
of short and fault on cables could not exist from the
transmission and power theft will be not possible in
any respect.
Some of the disadvantages are as follows:
1) High capital cost for practical implementation of wire-
less power transmission.
2) Another potential disadvantage is the interference of the
microwaves with the present wireless communication
system.
3) The effect of microwave radiations at high doses re-
ceived is not suitable to human health.
VII. APPLICATIONS OF WPT
1) Moving targets for example fuel free airplanes, fuel
free electric vehicles, moving robots and fuel free rock-
ets. Another applying WPT are wireless power source,
wireless sensors and RF power adaptive rectifying cir-
cuits(PARC).
2) Mobility - user device might be moved easily in the
wireless range.
3) Neat and easy Installation - since no cable running
occasionally, just start-up the wireless device and you’re
ready to rumble.
4) Generating power by placing satellites with giant solar
arrays in Geosynchronous Earth Orbit and transmitting
the power as microwaves on the earth called Solar Power
Satellites (SPS) will be the largest application of WPT.

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VIII. FUTURE SCOPE
Witricity is building a near field wireless charging apparatus
for consumer devices with the help of the Haier group, a
Chinese electronics manufacturer. Witricity demonstrated this
technology by wireless powering a 32-inch television at a
distance of six feet. Delphi Automotive is working with Witric-
ity to develop a wireless charging system for electric cars.
The ground breaking technology will enable to automotive
manufacturer to integrate wireless charging into the design
of hybrid electric vehicles [12]. There is another standard
protocol for charging mobile phone initiated by the Wireless
Power Consortium.
IX. CONCLUSION
The concept of wireless power transmission offers greater
possibilities for transmitting power with negligible losses.
In the end, this could reduce our societys dependence on
batteries, which are currently heavy and expensive. As wireless
technology is getting popular now a days, the demand of bat-
tery is also decreasing. For the long range power transmission
power can be sent from source to receivers instantaneously
without wires, reducing the cost. Batteries need to be recharge
or changed eventually, hence the need for this kind of work.
REFERENCES
[1] https://en.wikipedia.org/wiki/Heinrich Hertz.
[2] Colorado Springs notes
http://www.bibliotecapleyades.net /tesla/coloradonotes
[3] Wireless energy transfer, Wikipedia Foundation, Inc
http://en.wikipedia.org/wiki/Wireless energy transfer.
[4] G. E. Maryniak, Status of international experimentation in wireless
power Transmission, Sunset energy counsel, vol. 56 ,1996, pp. 7379.
[5] R. B. ERB, International cooperation for the acquisition of space based
energy, R Bryan ERB, Solar Energy, vol. 43 ,1998, pp. 108115.
[6] http://www.nss.org/settlement/ssp/index.html.
[7] P. Vessen, wireless Power transmission, Leonardo energy; briefing
paper,1998, pp. 64-69.
[8] A. Bomber, Wireless Power Transmission: An Obscure History, Possibly
a Bright Future,2003.
[9] T21 World Global Trends (Accessed March 23, 2006)
http://www.t21.ca/energy/index.html.
[10] http://web.mit.edu/newsoffice/2007/wireless 0607.html.
[11] F. Mishriki, Power Solutions A New Approach to Wireless Power
Transfer, Sensors,January 1, 2010, pp. 227-238.
[12] Wireless witricity new post, USA.
http://witricity.com