Wireless Recharging/Transmission Technology

Submitted By

C Somaskhandan

MBA-1st Year

VGSOM

IIT Kharagpur

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Table of content

I. Abstract 3

II. Introduction 3

III. Current Status of the Technology 6

IV. Economic Potential of the Technology 8

V. Current Players in the WPT 9

VI. Advantages and Hurdles 10

VII. Conclusion 12

VIII. Reference 13

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I. ABSTRACT

Today we are surrounded by electronic gadgets and many of them run on electricity from battery as

source. Battery makes these electronic gadgets mobile which makes it easy to carry around anywhere

we want. But when the power lever of the battery runs low we need to run towards the nearest wired

power source to recharge the battery. Now imagine a way through which we can recharge the battery

without the wire-recharger. This is possible now through the use of charge pump technology. This

technology uses a wireless charger which converts the RF/Microwave frequency waves into DC signal

and this energy can be stored in the battery. This term paper focuses on the modalities and

technological aspects of the technology. Then we will look into the existing products which already

incorporates this technology also some other research areas where electricity can be transmitted

wireless. This term paper will end with the future scope of this technology.

II. Introduction

We are using electricity for more than a century now and all these years electricity is transmitted

through wire cables to commercial and home units. We also use various electronic gadgets which

uses electricity through wire cables. Is it possible to done away with wire cables altogether and have

free electricity transmission without the physical connection? It is possible through wireless

transmission of electricity. The first concept that electricity can be transmitted without wire was

demonstrated by Nikola Tesla in 1893 during which he demonstrated the wireless illumination of

phosphorescent lamps at world exposition in Chicago. This feat was possible because of electro

dynamic induction. Induction is the prime principal used to transmit electricity for shorter distances.

Other means like R/F energy is used for short range electricity transmission. For far range electricity

transmission microwaves and laser as medium can be used which is currently in research stage. The

short range electricity transmission can be used to light electric gadgets and also to change batteries

wirelessly. Long range electricity transmission can light an entire city. The main advantage of this

transmission technique is that we can totally do away with wires which will help us to bring the

electricity to nook and corner of the world. Efficiency is the main criteria for this technology. R/F

energy transmission is having the least efficiency ratio and induction charger is having the most

efficiency.

History of Wireless transmission Technology

In 1820 Andre Ampere develops Ampere’s law proving that electric current in a metal conductor

produces a magnetic field around it.

In 1931 Michael Faraday develops faraday’s law describing that a magnetic field is induced when a

metal is subjected to time varying magnetic field flux.

In 1983 Nikola Tesla demonstrates the wireless illumination of lamps thus proving the possibility of

wireless power transmission.

In 1897 Tesla got the first patent registered for wireless transmission.

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In 1964 William brown demonstrated a model helicopter flown with a beam of microwave sent from

the ground.

In 1973 world’s first RFID system was demonstrated in Los Alamos National lab.

In 2008 Intel reproduces Tesla’s 1894 electrodynamics induction and wirelessly powered a bulb with

75% energy efficiency.

In 2010 Haier Group debuts world’s first completely wireless LCD television based on Tesla’s

electrodynamics induction process.

Techniques of Wireless Electricity Transmission

Wireless energy transmission or wireless power transmission (WPT) is different from wireless

information transmission; here the electric power is transmitted to a receiver through the use of radio,

Laser or a microwave waves. The efficiency or transmission ratio becomes the critical parameter

against which various methods are calibrated. In short wireless power transmission is defined as the

process through which energy/electricity can be transferred to the conductor without any physical

means of contact.

We will look into the various technologies in detail now-

a) Inductive Charging: Induction is the production of electricity across a conductor situated in a

changing magnetic field moving or a conductor moving through a changing magnetic field.

When a conductor is subjected through a changing magnetic field a current is induced in the

conductor and this current can be stored or used. The transfer of energy takes place by

electromagnetic coupling through a process known as mutual induction. This process works

only in short distances and can be used to run electric gadgets. The basic wireless changer

consists of the units which produces the changing magnetic field in varying degree. These

chargers are now commercially available and this can be used to charge any device which

uses a battery. Like cell phones, lap tops etc.

Fig 1:Induction based wireless charger.

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b) Evanescent Wave Coupling: This concept works on the principle that if both the coils of the

gadget and the transmitter to resonate at the same frequency then electricity can be induced

in them. One good point to be noted is that this process can be carried out even if distance

between the conductor coil and the transmitter coil is high and even multiple devices can be

powered through this process till they share the same frequency. This wave coupler can

power all electric devices in a home. The efficiency of this process depends on the distance

between the transmitter and the conductor coil. The efficiency is highest when both the

couples are tight and with increase in distance the magnetic energy is lost between the coils

and efficiency reduces. This technology is not commercially available yet but the future is

bright as lots of research is going on.

Fig 2: Evanescent Wave Coupling

c) Capacitive Induction: Capacitive Induction or Capacitive coupling is an electric field created

through differential capacities between two electrodes using high frequency AC current. The

alternative current produces a changing electric field which induces a current in the

electrodes. This effect is knows as Tesla effect.

d) Far Field Electricity Transmission: All the above stated technologies are used to transmit

power wireless through a small distance often in centimetre or in inches. But there are ways

to transmit power to large distances. This can be achieved using the radio or microwave

power transmission. The main criterion here is also the efficiency. If we can transmit large

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power efficiently over large distance then this technology could be used widely. First we look

at Radio/Microwave power transmission.

I. Radio/Microwave Power transmission: The basic step up for this process is three

components like a transmitter, Antenna and a charge pump to power some power units. The

transmitter is used to transmit high frequency radio/microwave energy. The frequency is

usually between 900 to 1200 MHz range. The transmitted radio frequency (RF) is captured

using an antenna. The energy captured through antenna is fed to a charge pump which will

convert this energy into DC current which can be used to run gadgets. The main component

here is the charge pump. At the heart of the charge pump consists of capacitors which will be

charged by the received RF. This stored in the capacitor can be converted to DC current.

Usually this current is stored in a battery and then this battery is used to run electronic

components. The main disadvantage with this type of power transmission is its efficiency is

very less. Lots of energy is lost in the transmission of RF. Only a small fraction is trapped by

the antenna placed at a distant. The efficiency can be slightly bettered through the use of

microwave as it can be transmitted in a line. But still its efficiency is way behind the

conventional transmission. In conventional power transmission the loss is around 6 %( in

USA) but with the current wireless transmission technology efficiency is less than 80-90% and

this is for inductive power transmission. For RF power transmission is less than 10%. But still

this is one technology which can transmit power to great distance.

II. Laser Power Transmission: Similar to RF power transmission we can use LASER to

transmit power to large distance. Since laser is a concentrated beam of light with very high

energy this can be used to transmit power with an efficiency of 40-45%. Some of the

advantage of using Laser over RF power transmission is that Laser has more energy

transmission capacity. It does not interfere with the existing radio frequency usage systems

like mobile phone transmission. It does have adverse human effects unless someone comes

into the line of sight of laser. One main advantage over RF power transmission is we have

control over the direction of the power transmission as in RF power transmission it is

omnipresent and laser can be transmitted in any particular direction which we want.

III. Current Status of the Technology

The induction based wireless chargers are already available in the market. Some companies are

already marketing their products with wireless charger. The induction based chargers have achieved

efficiency between 80 to 90%. The evanescent wave coupling is still in research stage, but once this

technology is viable then all electronic component in a home can be charged with a single transmitter

placed centrally in a home. In far field electricity transmission the technology can transmit power but it

is not economically viable due to less efficiency and high input cost.

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Fig 3: Dell Laptop with wireless charger. Dell Latitude model.

Above picture shows the Dell Latitude series laptop which uses world’s first wireless recharging pad to

charges its batteries. The battery of the laptop is connected to an induction coil and this laptop is

placed on the charging pad which has coils made inside. When power is connected to the charger

due to mutual induction the battery of the laptop is charged. The time it takes to charge this laptop is

same as the time it takes with the wired charger.

In 2009 Haier announced world’s first wireless LED TV. The figure of the TV is given below.

Fig 4: Haier’s world’s first Wireless LCD TV.

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In near future we can expect such technology to be incorporated into many more gadgets like I-Pod,

TV Remote, LCD TV, Lamps to run on induction based electricity transmission. We don’t need to

worry about charging our gadgets. The battery level of these components will be always at optimal

level.

In the realm of science fiction there are ideas and concepts where scientists and visionaries see this

concept being used for applications outside of this world. There is a concept of solar power satellite.

This concept is given another name as space based solar power where the solar radiation is

converted into electricity and beamed to earth for use here. Even though this idea is not yet in

practical application, some countries are active in research and development of this unique concept

like Japan in 2009 announced plan to orbit low earth satellites which will collect solar radiation and

transmit power back to earth through microwave. The first prototype will be operational in the year

2030. European space agency plans to put solar collecting small satellites in deep space to study

various ways solar energy can be captured and stored with degree of efficiency.

Fig 5: Artistic concept of solar satellite

The above picture is a conceptualization of a solar powered satellite which will capture the falling solar

radiation and transmit it back to earth as a powerful microwave radiation. This radiation will be pin

pointed to a collection station where it will be converted to electricity. This is where the Japan is

currently working on.

IV. Economic Potential of the Technology

This technology is already being used commercial as seen in the figure given couple of pages above.

Some companies have started to sell induction based charger to charger small battery operated

gadgets like TV remote, i-Pod, cell phones etc. Dell started to use wireless charger with their model

back in 2008.Evanescent coupling devices could possibly power all electric appliances in a home. A

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transmitting device fitted centrally in a home can power all electric devices within a specified distance

range.

Researchers at Korea Advanced Institute of Science and Technology (KAIST) has developed an

electric bus which drives power beneath the road surface where non-contact magnetic charging unit is

placed which the bus picks up as it moves along and gets itself recharged. This technology

demonstrator just gives us a glimpse of the future it holds. The experiment was a huge success;

researchers were able to transmit up to 60% of power from the coupling to the charging circuit in the

bus.

Aviation sector is one area where there is huge potential for practical application of this technology.

Experiments were carried out successfully to fly air craft with power beamed from the ground to the air

craft. World’s first fuel less aircraft was flown in Canada in 1987 with microwave energy beamed from

the ground. This program was called stationary high altitude relay platform, in short SHARP. Recently

NASA test flown an aircraft power by Laser beam sent from ground from its Dryden centre. The power

beamed to the aircraft is stored is a high power battery which deliver power to the motors which fly

these aircraft.

In 1975 NASA successfully demonstrated the microwave wireless power transmission of 30Kw power

over a distance of 1.6 Kms. The receiver transferred the power at 82% efficiency which was

remarkable. If this technology can be implemented then remote villages can receive power wireless

from distant transmission station and power can be made available to villages.

V. Current Players in the WPT

Some companies are active in Wireless power transmission technology. For eg

DELL- Dell has started giving the option of having wireless chargers in there customization option to

the customers.

Palm Inc- This smart phone company announced in 2009 to launch touch stone models of phones

with wireless charger as its standard accessory.

Hughes Electronics- This Company in collaboration with General motors introduced a battery

operated car with the option of recharging it wireless. The car is named General Motors EV1 electric

car.

Evatran Company- A subsidiary of MTC Transformers began development of ‘plug less power’ in

2009. This is based on inductive charging system which will power electric car through wireless

recharging technology.

Toshiba- They released a wireless powered television which was first in the world to have a powering

mechanism of that kind.

Wireless Power Consortium- An alliance of 20 firms had formed this group to device open source

standard for wireless charging technology. Some bug tickets include Philips, Sanyo, Nokia, Texas

Instruments, research in Motion, Duracell, and Energizer etc. Their draft version is ready as of July

2010. Some companies like Samsung electronics and Ericson are associates of this group who will

contribute standards to be part of this alliance.

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IAV GmbH- This German Company is working on chargers which can be implemented in the road

which would allow the car to be charged as it runs along the road surface.

VI. Advantages and Hurdles

If wireless recharging and transmission technology is applied in a large way, then we can do away

with costly grids and substations which provide us with power till now. Homes and cities can be

provided power wireless from a central transmission point which will cater to the needs of the

population within its reach. Battery operated devices will never run out of power if this technology is

implemented. When this technology is extended to cars then we can have cars that run non-stop with

full battery charge. We will never have to go to charging station or to any fuel station to get the tank

filled.

Future application of this technology is so immense that it is unwise not to invest in this area. As

mentioned above the experiments carried out with aircraft and public power transmission, if this

technology is implemented then aircraft can fly nonstop with no need to refuel. Remote corners of our

nation can be provided electricity with this technology. The future highway could have inductive coils

imbedded in the road which will provide continuous stream of electricity to the car. This technology

has a high efficiency of 80 to 90 % in some cases which is very encouraging. The potential for this

market is huge and estimated to be around 1 billion dollar per year market. Many companies are

researching in this area and standards have been put in place.

Hurdles for this technology-

a) Biological Drawbacks-

Some consider the usage of such high frequency radio and microwave to transmit power

could cause potential damage to living tissues. There is no concrete study to prove this, but

still many are wary about the prospect of being surrounded by high frequency waves. This

could be a hurdle to implement wireless transmission in large scale, but there are no known

aliments associated with induction based recharging techniques. If any life form comes in

between the line of sight of microwave and Laser signal then it can cause harm.

b) Economic cost-

The initial set up to transmit power to remote village is huge. Consider a village of 500 people;

it is not justified to invest 10-15 million dollars just to install the transmitting station to receive

the power. In house wireless power transmission like evanescent wave coupling is costly and

many people may be going for it.

c) Efficiency of current technology-

The maximum efficiency that can be achieved is around 92% with induction based wireless

charger. If wires chargers are used they can provide power to battery with much higher

efficiency. The wireless power transmission technique is also having very low efficiency

compared to the traditional or conventional way of power transmission. The transmission loss

in USA through conventional way is around 6%. All currently know wireless power

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transmission technique has efficiency far less than this figure. In such situation the takers for

this technology will be less.

d) Resonance loss and atmosphere absorption loss-

Induction based power recharging technique has resonant loss which is unavoidable and may

produce excess heat. Sometimes the heat produced is so huge it may damage the

components permanently. If microwave or Radio waves are used to transmit power then there

could be some atmospheric absorption loss which cannot be done away with. One more

serious problem with Laser and Microwave based transmission technique is that they sent

signals in a particular direction and if there line if sight is broken or any obstruction come in

between then the power transmission will break.

e) Interference with existing network- Induction based recharging can cause resonance in

electric circuit which can cause motors and other such devices which will fluctuate will change

in resonance frequency. High frequency radio and microwave signal can interfere with the

existing mobile and radio signal which can play spoil sport.

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VII. Conclusion

Transmission of power without wire is not science fiction but a reality now. Without any physical

contacts we can transmit power to any distance and run appliances which can be controlled

independently. Many companies now have wireless chargers as part of their standard accessory.

When Nikola Tesla tried his induction coupling experiments the efficiency was in the range of 20%,

now the efficiency has increased to 80 to 90%. This is a very encouraging sign and academia and

industry recognize this change and trying to incorporate these solutions in everyday life. Some non-

profit organization like Japan’s space agency and European space agency is the process of

formulating a plan to send solar power satellite. May be in future the earth’s power requirement may

come from these satellites which can beam back power to earth. And one of the best advantage of

this technology would be we could get rid of all the cables line which stretch the face of our homes

and cities carrying power. Remote corners of our country can enjoy the benefits of electricity as this

technology can bring power to their footsteps. The future of wireless transmission/recharging

technology looks secured.

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VIII. Reference

1) Wireless Electricity

http://www.fastcompany.com/magazine/132/brilliant.html

2) http://en.wikipedia.org/wiki/Inductive_charging

3) http://en.wikipedia.org/wiki/Wireless_energy_transfer

4) Time line of Technology-

http://inventors.about.com/od/timelines/a/electricity_timeline.htm

5) Wireless Technology

http://emergingtechnology.wordpress.com/2007/10/02/wireless-

electricity/

6) Espejel, J.D., “RF to DC power generation”, University of Maryland,

December 2003.

http://drum.umd.edu:8003/dspace/handle/1903/176

7) Wireless Charger

http://www.economist.com/science/tq/displayStory.cfm?

story_id=13174387

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