WiTricityWiTricity

Wireless Power Wireless Power TransmissionTransmission

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What is WPT?What is WPT?The transmission of energy from

one place to another without using wires

Conventional energy transfer is using wires

But, the wireless transmission is made possible by using various technologies

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HistoryHistory

Nikola Tesla in late 1890sPioneer of induction techniquesHis vision for “World Wireless System”The 187 feet tall tower to broadcast

energyAll people can have access to free energyDue to shortage of funds, tower did not

operate

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ORIGINAL WORK OF TESLAORIGINAL WORK OF TESLA

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There’s something new coming up to play with ‘Wireless Electricity’.

In the first successful trial of its kind, the team was able to illuminate a 60-watt light bulb 7ft away .

The team from Massachusetts Institute of Technology, who call their invention ‘WiTricity‘.

What Is Inductive Coupling?InductiveCoupling is a method for

short range wireless energy transfer. Its range can vary, but it’s often

very short.

Short Range Wireless Energy Short Range Wireless Energy Transmission: Inductive Transmission: Inductive CouplingCoupling

Inductive coupling Inductive coupling Primary and secondary coils are

not connected with wires.Energy transfer is due to Mutual

Induction

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How does Inductive Coupling How does Inductive Coupling Work?Work?

Inductive coupling works on the principles 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 , making inductive coupling effective only at very short ranges.

What Is Resonant Induction?

A group of engineers at MIT came up with the idea to use resonant induction to transmit power wirelessly. They deemed their result “WiTricity” (like Wi-Fi) . WiTricity can transmit electricity wirelessly at 40% efficiency to about 7 feet.

Medium Range Wireless Medium Range Wireless Energy Transmission: Energy Transmission: Resonant InductionResonant Induction

Resonance Inductive Resonance Inductive Coupling(RIC)Coupling(RIC)Combination of inductive

coupling and resonanceResonance makes two objects

interact very stronglyInductance induces current

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How resonance in RIC?How resonance in RIC?Coil provides the inductanceCapacitor is connected parallel to

the coilEnergy will be shifting back and

forth between magnetic field surrounding the coil and electric field around the capacitor

Radiation loss will be negligible

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Block diagram of RICBlock diagram of RIC

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An exampleAn example

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WiTricity (contd…)WiTricity (contd…)

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DisadvantagesDisadvantagesDistance constraintField strengths have to be under

safety levelsInitial cost is highIn RIC, tuning is difficultHigh frequency signals must be

the supplyAir ionization technique is not

feasible04/11/23 Wireless Power Transmission 17

Microwave Power Microwave Power Transfer(MPT)Transfer(MPT)Transfers high power from one

place to another. Two places being in line of sight usually

Steps:◦Electrical energy to microwave energy◦Capturing microwaves using rectenna◦Microwave energy to electrical energy

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MP T (contd…)MP T (contd…)AC can not be directly converted

to microwave energyAC is converted to DC firstDC is converted to microwaves

using magnetronTransmitted waves are received

at rectenna which rectifies, gives DC as the output

DC is converted back to AC

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Solar Power Satellites Solar Power Satellites (SPS)(SPS)

To provide energy to earth’s increasing energy need

To efficiently make use of renewable energy i.e., solar energy

SPS are placed in geostationary orbits

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SPS (contd…)SPS (contd…)Solar energy is captured using

photocellsEach SPS may have 400 million

photocellsTransmitted to earth in the form of

microwaves/LASERUsing rectenna/photovoltaic cell, the

energy is converted to electrical energyEfficiency exceeds 95% if microwave is

used.

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RectennaRectennaStands for rectifying antennaConsists of mesh of dipoles and

diodesConverts microwave to its DC

equivalentUsually multi-element phased

array

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Rectenna in USRectenna in USRectenna in US receives 5000MW

of power from SPSIt is about one and a half mile

long

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Other projectsOther projectsAlaska’21

Grand BassinHawaii

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MIT's WiTricity is only 40 to 45% efficient and they have to be twice as efficient to compete with the traditional chemical batteries.

Aim is to get a robotic vacuum or a laptop working, charging devices placed anywhere in the room

The researchers have said that in another five years time, they will come up with a WiTricity system for commercial use.

What's the Future of WiTricity? What's the Future of WiTricity?

ConclusionConclusionTransmission without wires- a realityEfficientLow maintenance cost. But, high initial

costBetter than conventional wired

transferEnergy crisis can be decreasedLow loss In near future, world will be

completely wireless

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