International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

382

Goodbye Wires: Approach to Wireless Power

Transmission Sourabh Pawade

1, Tushar Nimje

2, Dipti Diwase

3

1Student, Electronics & Telecommunication, G.H. Raisoni College of Engineering, Nagpur.(INDIA)

2Student, Electronics & Telecommunication, G.H. Raisoni College Of Engineering, Nagpur. (INDIA)

3Lecturer, Department of Information Technology, G.H. Raisoni College of Engineering, Nagpur. (INDIA)

1sourabh.pawade@gmail.com 2tusharnimje21@gmail.com

3dipti_123diw@yahoo.co.in

Abstract— In this paper, we are dealing with the concept of

transmitting power without using wires. The various

technologies available so far for wireless transmission of

electricity and the need for a wireless system of energy

transmission is being discussed here to find its possibility in

actual practices, their advantages, disadvantages and

economical consideration. Many concepts, research papers,

patents are available on wireless transmission of electricity

but the commercial technologies are yet to be materialized.

The paper summarises the possible ways to get useful and

practical results out of all research carried out so far

elsewhere.

Keywords— Wireless Power Transmission, Nikola Tesla, Solar

Power Satellites.

I. INTRODUCTION

One of the major issues in power system is the losses

during the transmission and distribution of electrical

energy. As the demand increases day by day, the power

generation increases and the power losses is also increased.

In our present electricity generation system we waste more

than half of our resources. Much of this power is wasted

during transmission from power plant generators to the

consumer. The resistance of the wire used in the electrical

grid distribution system causes a loss of 26-30% of the

energy generated. This loss implies that our present system

of electrical distribution is only 70-74% efficient. We have

to think of alternate state- of-art technology to transmit and

distribute the electricity [16]. Now-a-days global scenario

has been changed a lot and there is tremendous

development in every field. If we don‘t keep pace with the

development of new power technology we have to face a

decreasing trend in the development of power sector. The

transmission of power without wires may be one noble

alternative for electricity transmission.

The definition of Wireless Power Transmission (WPT)

can be given as a way of efficient transmission of electric

power from one point to another trough vacuum or an

atmosphere without the use of wire or any other substance.

This can be used for applications where either an

instantaneous amount or a continuous delivery of energy is

needed, but where conventional wires are unaffordable,

inconvenient, expensive, hazardous, unwanted or

impossible. The power can be transmitted using

microwaves, millimetre waves or lasers. WPT is a

technology that can transport power to locations, which are

otherwise not possible or impractical to reach.

II. WIRELESS ENERGY TRANSMISSION TECHNOLOGY

A. Tesla Theory:

Nikola Tesla is one who invented radio and shown us

he is indeed the ―Father of Wireless‖. Nikola Tesla is the

one who first conceived the idea Wireless Power

Transmission and demonstrated ―the transmission of

electrical energy without wires" that depends upon

electrical conductivity as early as 1891[2]. In 1893, Tesla

demonstrated the illumination of vacuum bulbs without

using wires for power transmission at the World

Columbian Exposition in Chicago. The Wardenclyffe tower

shown in Figure 1 was designed and constructed by Tesla

mainly for wireless transmission of electrical power rather

than telegraphy [3].

This was to be the first broadcasting system in the world.

Tesla wanted to transmit electricity from this Tower to the

whole globe without wires using the Ionosphere. The

source of the transmitted electricity was to be the Niagara

Falls power plant [1]. The most popular concept known is

Tesla Theory in which it was firmly believed that

Wardenclyffe; shown in figure 1 would permit wireless

transmission and reception across large distances with

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

383

negligible losses [2]. In spite of this he had made numerous

experiments of high quality to validate his claim of

possibility of wireless transmission of electricity [15]. But

this was an unfortunate incidence that people of that

century was not in a position to recognize his splendid

work otherwise today we may transmit electricity

wirelessly and will convert our mother earth a wonderful

adobe full of electricity[1][2][3].

Fig.1. 187-foot Wardenclyffe Tower (Tesla Tower) [16]

In order to transport electricity is has to be transformed

into a suitable energy form. For wireless transmission, this

has to be a form that can travel trough air. Microwave

frequencies hold this ability. The microwave spectrum is

defined as electromagnetic energy ranging from

approximately 1 GHz to 1000 GHz in frequency, but older

usage includes lower frequencies. Most common

applications are within the 1 to 40 GHz range. A complete

microwave transmission system consists of three essential

parts:

• Electrical power to microwave power conversion

• Absorption antenna that captures the waves

• (Re) conversion to electrical power

B. Laser Method:

In the case of electromagnetic radiation closer to visible

region of spectrum (10s of microns (um) to 10s of nm),

power can be transmitted by converting electricity into a

laser beam that is then pointed at a solar cell receiver. This

mechanism is generally known as "power beaming"

because the power is beamed at a receiver that can convert

it to usable electrical energy Units.

Fig. 2: Energy transfer through microwave between two stations

[15]

In 2002 and 2003, Steinsiek and Schoafer demon

started ground to ground wireless power transmission via

laser to a small, otherwise fully independent rover vehicle

equipped with photovoltaic cells as a first step towards the

use of this technology for powering airships and further in

the future lunar surface rovers. The experiment was based

on a green, frequency-doubled Nd:YAG[8] laser at only a

few Watts. It included the initiation and supply of the rover

including a micro-camera as payload as well as the pointing

and tracking of the moving rover over a distance up to 280

m by applying active control loops. Fig (3) shows EADS

developed, fully laser powered autonomous rover.

Fig. 3: EADS developed, fully laser powered autonomous rover

In principle, all lasers can be used for transmitting

power. Using the general conditions as specially applied for

the selection of lasers, these imply in addition constraints

related to the efficiency of the laser generation process, and

the efficiency of the absorption and laser-to-electric

conversion processes. Specially for direct solar pumped

lasers, there are several types of materials suitable as laser

medium. From the standpoint of resistance to thermal

stress, Sapphire seems optimal material for laser medium.

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

384

Since large sapphire crystals are very difficult to produce,

most concepts rely on YAG (yttrium aluminium garnet)

laser crystals. Concerning the required energy densities,

solar energy compression ratios of a few hundred times are

required for YAG lasers. Applications in space or from

space to Earth add additional constraints regarding the laser

generation system mass like laser generation temperature

requirements (preference for very high temperature

operations in order to allow for a low radiative heat

rejection system mass and small size), absence of

consumables and other potential waste products, high laser

beam quality to avoid the use of lenses and achieve small

receiving surfaces and control of the phase (arrays of

matrices of different laser, possibly used in order to form

virtual, large apertures).

Laser power transmission systems are still considered

as less mature than microwave based systems. However, it

is argued that due to recent advances in direct solar pumped

lasers, the potential integration of space and terrestrial

based solar power plants and potentially radical

simplifications on the space system design; laser-based

wireless power transmission concepts should be matured

further in order to represent a credible alternative.

C. Electric Resonance:

Electromagnetic radiation has been used, typically, for

information broadcasting. But that is not the only possible

application, however. It is possible to transfer power using

electromagnetic radiation. In Particular, using microwaves

the energy can be directed to a specific point as shown in

Figure 2[8].Although the method is efficient, it has two

draw-backs: requires a sight line and it is a dangerous

mechanism for live beings.

Mechanical resonance is well known, it works applying

a vibratory action on an object. The vibration period match

the frequency in which the object reaches the highest

energy absorption rate. Such frequency is known as

resonance frequency. This phenomenon well known on

mechanics is also perceived in electricity and it is known as

electric resonance. Such phenomenon can be used to

transfer energy in a wireless fashion with following

benefits:

The maximum absorption energy rate is guaranteed and

it is possible to work using low frequencies (not so harmful

to the human being). When two objects have the same

resonant frequency, they can be coupled in a resonant way

that one object can transfer energy (in an efficient way) to

the other. In electricity there are two kinds of resonant

coupling: ―inductive‖ [13] and ―strong‖ [10].

The inductive coupling is the resonant coupling between

the coils of two LC circuits with the same resonant

frequency, transferring energy from one coil to the other as

seen in figure (4).The disadvantage of this technique is that

the efficiency degrades sharply as coils separate. In fact,

there are commercial products that recharge mobile devices

that require placing the device right over the transmitter; it

means that maximum efficiency can be reached only at 0

cm.

Fig. 4: Inductive coupling for energy transfer

This scheme has two drawbacks. The first one is self-

resonant frequency is a coil that depends on its parasite

capacitance, this cause that such frequency be high (in the

range of GHz). Therefore, to achieve a low self-resonant

frequency (< 10Mhz) is necessary to employ thick copper

wire and be placed in such a way to achieve a high parasite

capacitance reducing the self-resonant frequency to the

megahertz range. In fact, in [10][11] it is reported an

experiment using cable with radius of 3 cm and the second

drawback is efficiency on the power transfer sharply de-

clines as the separation between coils in-crease, then it is

necessary to employ big coils in order to achieve longer

separation distances. This is the reason why the re-ported

experiments in [10] [11] the coils have radius of about 30

cm.

III. APPLICATIONS

Wireless power transmission would have many

interesting applications. Some of the applications involve

simply powering devices or vehicles from a remote power

source. However, the energy grid could be affected as well.

If long distance, high efficiency wireless power

transmission is possible, we could reduce our reliance on

transmission lines to transfer energy over long distances.

Moreover, wireless power transfer could allow an

alternative source of clean energy by transmitting solar

power from space back down to places where it is needed

on earth. Some applications are as follows-

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

385

A. Solar Power Satellites

If an efficient method of wireless power transmission is

developed, one possible application would be a solar power

satellite as shown in Figure 5[17]. This idea consists of

having a satellite with solar panels orbiting the earth. The

satellite generates electrical energy using its solar cells.

This energy is converted into an electromagnetic wave and

transmitted wirelessly to receivers on the earth. The

receivers then convert the transmitted energy back into

usable electrical power. To demonstrate technical

feasibility, researchers would first like to transmit kilowatts

of power from a satellite in low-earth orbit. Additionally,

target 80% conversion efficiency is desired within both the

transmitter and the receiver. Since the satellite orbits above

the atmosphere, it would consistently collecting solar

energy, as opposed to photovoltaic systems on earth which

may be obstructed by weather conditions. Also, a single

satellite could potentially provide power to many locations

around the world by having multiple wireless power

receivers linked to the satellite. Thus, the development of

solar power satellites could consistently provide clean

energy around the world [17].

Fig. 5: A schematic of the proposed solar power satellite [17]

B. Wireless Charging of Devices

Wireless energy transfer has been thought about for

decades by scientists all over the world. There were many

experiments done and some are successfully till some

extent. In 2007, US researchers have successfully tested an

experimental system to deliver power to devices without

the need for wires. The experimental setup consisted of two

60cm (2ft) diameter copper coils, a transmitter attached to a

power source and a receiver placed 2m (7ft) away and

attached to a light bulb. WiTricity, as it is called, exploits

simple physics and could be adapted to charge other

devices such as laptops.

The bulb was even made to glow when obstructions

such as wood, metal and electronic devices were placed

between the two coils [18].Figure 6 shows the experimental

setup for charging of bulb [18].

Fig.6. Charging Of Bulb.

Again one of the applications is that we can charge

laptop wirelessly. This is shown in figure 7. Power from

mains to antenna, which is made of copper antenna,

resonates at a frequency of about 10MHz, Producing

electromagnetic waves. Tails of energy from antenna

‗tunnel‘ up to 2m is transmitted(6.5ft).Electricity is picked

up by laptop‘s antenna, which must also be resonating at

10MHz. Energy is used to re-charge device. Energy not

transferred to laptop is re-absorbed by source antenna.

People/other objects are not affected as not resonating at

10MHz.

Fig.7.- Wireless laptop charger

C. Indistrial Application

Wireless communication can be used in very effective

manner for many industrial applications. Use of direct

wireless power and communication interconnections across

rotating and moving ―joints‖ (robots, packaging machinery,

assembly machinery, machine tools) eliminate costly and

failure-prone wiring[19]. Another example is the use of

direct wireless power and communication interconnections

at points of use in harsh environments like drilling, mining,

underwater, etc it is impractical or impossible to run wires.

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

386

Direct wireless power for wireless sensors and actuators,

eliminating the need for expensive power wiring or battery

replacement and disposal. Automatic wireless charging for

mobile robots, automatic guided vehicles, cordless tools

and instruments eliminate complex docking mechanisms,

and labor intensive manual recharging and battery

replacement [19].

IV. MERITS, DEMERITS OF WIRELESS POWER

TRANSMISSION

Wireless power transmission is consider as one of the

most effective and emerging power transmission technique

and has following merits of using it.

An electrical distribution system, based on this

method would eliminate the need for an

inefficient, costly, and capital intensive grid of

cables, towers, and substations. The system would

reduce the cost of electrical energy used by the

consumer and rid the landscape of wires, cables,

and transmission towers [14][15].

There are areas of the world where the need for

electrical power exists, yet there is no method for

delivering power. Africa is in need of power to

run pumps to tap into the vast resources of water

under the Sahara Desert. Rural areas, such as

those in China, require the electrical power

necessary to bring them into the 20th

century and

to equal standing with western nations. The

wireless transmission will solve many of these

problems. Electrical energy can be economically

transmitted without wires to any terrestrial

distance, so there will be no transmission and

distribution loss [14].

More efficient energy distribution systems and

sources are needed by both developed and under

developed nations. In regards to the new systems,

the market for wireless power transmission is

enormous. It has the potential to become a multi-

billion dollar per year market.

The increasing demand for electrical energy in

industrial nations is well documented. If we

include the demand of third world nations, pushed

by their increasing rate of growth, we could expect

an even faster rise in the demand for electrical

power in the future.These systems can only meet

this 90–94 % efficient transmission [3, 8].

High Transmission Integrity and Low Loss: - To

transmits wireless power to any distance without

limit. It makes no difference what the distance is.

The efficiency of the transmission can be as high

as 96 or 97 per cent, and there are practically no

losses.

Every coin has two sides and same story continue over

here that means wireless power transmission method is

accompanied with some disadvantages. The major demerit

of this method is a biological impact on wireless power

transmission. One common criticism of the Tesla wireless

power system is regarding its possible biological effects.

While calculating the circulating reactive power, it was

found that the frequency is very small and such a frequency

is very biologically compatible.

V. CONCLUSION

The transmission of power without wires is not a theory

or a mere possibility, it is now a reality. The electrical

energy can be economically transmitted without wires to

any terrestrial distance. Many researchers have established

in numerous observations, experiments and measurements,

qualitative and quantitative. Dr.N.Tesla is the pioneer of

this invention. Wireless transmission of electricity have

tremendous merits like high transmission integrity and Low

Loss (90 – 97 % efficient) and can be transmitted to

anywhere in the globe and eliminate the need for an

inefficient, costly, and capital intensive grid of cables,

towers, and substations. 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. It has a

tremendous economic impact to human society. Many

countries will benefit from this service. Monthly electric

utility bills from old-fashioned, fossil-fuelled, loss prone

electrified wire-grid delivery services will be optional,

much like ―cable TV‖ of today.

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012)

387

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