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Wireless Electricity

PRESENTED BY: SHAIK SARTAJ AHMED


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What do you mean by Wi Tricity ? Need of witricity History of wireless power Witricity Basics Detailed Principle How Safe is Wi Tricity ? What's the Future of WiTricity ? Advantages Limitations Bibliography


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The Transfer of Electricity from one place toanother without wires is known as WiTricity.

On June 7 07, a team of researchers at MITannounced the successful operation ofWiTricity concept.

They had lit up a 60W bulb with a powersource at a distance of 7 feet(over 2m) withno wires.


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In 2005, Dave Gerding coined the termWiTricity which is being used today.

Forgotton invention was reborn in 2007

In 1891, Sir Nikola TeslaProposed a method of Wireless

Power Transmission.

As it is in Radiative mode,

most of the Power was wasted

and has less efficiency.


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In 1891, Nikola Tesla invented a type ofresonant transformer called the Tesla coil,which was used to generate very high voltage,low current, and high frequency alternating

electricity. He experimented with a largevariety of coils and configurations, one ofwhich is as:


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In1899,Tesla achieved

a major breakthroughin his work atColorado bytransmitting 100

million volts of electricpower wirelessly overa distance of 26 milesto light up a bank of

200 light bulbs andrun one electricmotor.


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Cell phones, i pods, laptop computers arecapable of re-charging themselves withoutever being plugged in.


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Currently, wired electricity powers haveconcured nearly everything.

In present electricity generation system wewaste more than half of its resources.Especially the transmission and distributionlosses are the main concern of the present

power technology.


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The resistance of the wire used in theelectrical grid distribution system causes aloss of 26-30% of the energy generated

The transmission of power without wires maybe one noble alternative for electricitytransmission.


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Prof. Marin Soljacic from MassachusettsInstitute of Technology (MIT), is the onewho has proved that magnetic coupledresonance can be utilized in order to transfer

energy without wires.

He used Michael Faraday's principle ofelectromagnetic induction (1831) came upwith WiTricity.


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There are 3 major types of wireless energytransfer:

Short range; Inductive Coupling

Medium range; Resonant Induction Long range; Electromagnetic Wave Power

Transfer


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What Is Inductive Coupling?

Inductive Coupling is a method for short

range wireless energy transfer. Its range can vary, but itsoften very short.


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Inductive coupling works on theprinciples of electromagnetism:

When a current (electricity) passes

through a wire, it generates a magnetic

field perpendicular to the wire.

When a wire is in proximity to a

magnetic field, it generates a current in

that wire.

Magnetic fields decay quickly , makinginductive coupling effective only at very

short ranges.


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What Is Resonant Induction? A group of engineers at MIT came up with theidea to use resonant induction to transmitpower wirelessly. They deemed their resultWiTricity(like Wi-Fi) . WiTricity can transmitelectricity wirelessly at 40% efficiency to

about 7 feet.


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Resonant induction still uses the sameprinciples as magnetic induction (magneticfields to transfer current) , but it usesresonance to increase the range at whichthe transfer can efficiently take place.

Resonance",a phenomenon that causes an

object to vibrate when energy of a certainfrequency is applied.


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Everything resonates at a certain frequency,based on its shape and material.

Energy transfers easily between resonatingobjects. An example of this is when an operasinger shatters wine glasses by singing at thefrequency at which the glasses resonate.

With resonant induction, power is transmitted

between two resonating coils.


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Consider two self resonating copper coils ofsame resonating frequency with a diameter20 inches each. One copper wire isconnected to the power source , while the

other copper wire is connected to the device.


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A Tesla Coil produces high voltage electric

arcs. These arcs cause permanent damage toelectrical devices on contact

Tesla coils also destroy hearing aids andcardiac pacemakers in their vicinity.


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Is WiTricity safe? How much power can be transferred? What about the range of transferred? How efficient is WiTricity? What's the Future of WiTricity?


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The rate of energy transfer between theemitter and the receiver is greater than therate of energy dissipation.

Efficiency is mesured by measuring thecurrent at the midpoint of the self resonantcoils with a current probe.

This gives a measurement of the current

parameters


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We then compute power dissipated in each coilfrom:-

Then the efficiency can be calculated .


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Direct Wireless Power No device needs wires

Immobile devices

Automatic Wireless Charging Device with rechargeable

batteries

charges itself Mobile device

Used in and out of range of itsWiTricitypower source


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Consumer Electronics

Industrial

Transportation

Miscellaneous


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Will it harm me? Will it harm the environment?

Will it interfere with importantcommunication?


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Human beings or other objects placedbetween the transmitter and receiver donot hinder the transmission of power.

However, does magnetic coupling or

resonance coupling have any harmful effectson humans?

magnetic fields tend to interact veryweakly with the biological tissues of the

body, and so are not prone to cause anydamage to any living beings.


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Safe, fairly efficient, good range:

Magnetic fields interact weakly withbiological masses (humans),

Efficiency can be increased with time, mostof the 60% lost is from heat radiated from

the coils. Theoretically one stationary coil in a room

could power multiple devices with receivingcoils.

No more messy wires, and with widespreadenough use it could even eliminate costlybatteries.


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The resonance condition should be satisfied andif any error exists, there is no possibility of powertransfer.

If there is any possibility of very strongferromagnetic material presence causes low powertransfer due to radiation.


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MIT's WiTricity is only 40 to 45% efficient and

they have to be twice as efficient tocompete with the traditional chemicalbatteries.

Aim is to get a robotic vacuum or a laptop

working, charging devices placed anywhere inthe room

The researchers have said that in anotherfive years time, they will come up with a

WiTricity system for commercial use.


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1. An article published in the Science Magazine as Wireless Power Transfer via StronglyCoupled Magnetic Resonances by Andre kurs, Science 317, 83(2007); Dol:10.1126/science.1143254.2. H. Haus , Wavesand Fields in Optoelectronics Prentice hall Publishers, Englewood3. http://electron9.phys.utk.edu/optics507/modules/m6/coupled_resonators.htm4. EfficientNon-Radiative Midrange Energy Transferby Aristeidies karalis, Marlin Soljacic.5. Nikola Tesla, My Inventions Ben Johnston Ed. Austin Hart Brothers, p. 91,1982.6. Thomas F. Valone, Teslas Wireless Energy... For the 21stCentury One Step BeyondDirect TV Extra Ordinary Technology 1 no. 4 Oct / Nov / Dec 2003.7. James O. McSpadden, Wireless Power Transmission Demonstration Texas A&MUniversity, June, 1997.8. Charych Arthur (Setauket, NY), System and method for wireless electrical powertransmission Patent No. 6 798 716 September 28, 2004.9. Joe T. Howell, et. al , Advanced receiver / converter experiments for laser wirelesspower transmission5th. Wireless transmission conference pp 1-8 Garanda

Spain 2004.


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