--The Wireless Electricity.

By

Karan Bir Singh

E073026

What is witricity?

Witricity is nothing but wireless electricity.Transmission of electrical energy from one

object to another without the use of wires is called as Witricity.

Because of Witricity some of the devices won't require batteries to operate.

.

The story started late one night a few years ago. It was probably the sixth time that month that MIT Professor Marin Soljacic was awakened by his mobile phone beeping battery low. At that time it occurred to him that there is electricity wired all through his house, office-everywhere. He think about- how it is possible to use electricity without using wires…

Electro magnetism

Resonant magnetic coupling

RESONANCE

Electromagnetic induction is the production of voltage across a conductor moving through a magnetic field.Electromagnetism is one of the four fundamental interactions of nature, along with strong interaction, weak interaction and gravitation. It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called electromagnetic fieldsEnergy/Power Coupling: Energy coupling occurs when an energy source has a means of transferring energy to another object

Resonance :is the tendency of a system to oscillate with larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies (or resonance frequencies). At these frequencies, even small periodic driving forces can produce large amplitude oscillationsResonant Magnetic Coupling: Magnetic coupling occurs when two objects exchange energy through their varying or oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two objects are approximately the same.

The Transfer of Electricity from one place to another without wires is known as “Witricity”.

There is witricity power sources(transmitter) and capture devices(receiver).

Power source provides power to the devices where as capture device captured it to work.

Power source and capture devices are specially designed magnetic resonators.

Magnetic resonators efficiently transfer power over mid-range distance via the magnetic near-field.

Near field Near field is a wireless transmission

technique over distances comparable to or a few times the diameter of devices.

Near field is usually magnetic.

Near field energy is non radiative .but some radiative and resistive losses will occur.

Coupled resonators Two resonant objects of the same resonant

frequency tend to exchange energy.

It exchange energy strongly ,while interacting weakly with living beings and other environmental objects.

Coupled resonators are said to be operate in strongly coupled regime to avoid material absorption and radiative loss.

MIT teams behind witricity technology The first experiment of witricity, the concept of wireless electricity, was conducted in the year 2006, by researchers from Massachusetts Institute of Technology. The Assistant Professor of this team of researchers was Marin Soljacic.

2007: A physics research group, led by Prof. Marin Soljacic,at MIT, wirelessly power a 60W light bulb with 40% efficiency at a 2 meters (6.6 ft) distance using two 60 cm-diameter coils

Schematic Diagram

Diagram of power source and capture device

Power source is connected to ac power.

Bulb is connected to capture device.

Blue lines represent the magnetic near field induced by the power source.

Yellow lines represent the flow of energy from the source to the capture coil.

This powers light bulb.

The magnetic field can wrap around the obstacle between power source and capture coil.

Range & Rate of Coupling:

Using Coupled Mode Theory (CMT), we can give some frame work to the system. The field system of the two resonant objects 1, 2 is

F(r,t)=a1(t)F1(r)+a2(t)F2(r)

Where F1,2(r) are the resonating modes of 1 and 2 alone, and then the field amplitudes a1(t) and a2(t).The lower order representation of the system is given by :

Where ω1, 2 are the individual frequencies, Γ1, 2 are the Resonance widths (Decay rates) due to the objects’ intrinsic (absorption, radiation etc.) losses, and ‘κ’ is the coupling coefficient .

The solution of the equation show that at exact resonance at

ω1=ω2 and Γ1=Γ2

the normal modes of the combined system are split by 2κ.

Ratio {κ /sqrt (Γ1, 2)} shows that, it will set as figure-of-merit for any system under consideration for wireless energy-transfer, along with the distance over which this ratio can be achieved.

The desired optimal regime {κ/sqrt (Γ1,2)>>1} is called “Strong-Coupling” regime. There is No change in Energy, unless κ/Γ>>1 is true.

Simulation model Using COMSOL:

Simulation Performance: By the basic parameters, calculated results and performance given with and Without the External object in between the coils.

Comparison of Results:

Two loops D/r Qrad Q=ω/2Γ ω/2κ κ/ Γ

R=30cm,a=2mm,ε=10,d=4mm,Qabs=4886.

3 30729 4216 63.7 68.7

5 29577 4194 248 17.8

Two loops D/r Qrad Q=ω/2Γ ω/2κ κ/ Γ

R=30cm,a=2mm,ε=49+16i,d=4mm,Qabs=4886.

3 30729 4136 62.6 67.4

5 29577 4106 235 17.6

Results without Extraneous objects:

Results with Extraneous objects:

Witricity technology is more than…

Traditional magnetic induction.

Radiative power transfer.

Tesla’s vision of a wireless world.

Used in power transformers. conductive coils transmit power to each other

wirelessly, over very short distance.

An electric tooth brush uses traditional magnetic induction to recharge its batteries

Radio frequency energy is used for wireless power transfer.

Radiated power is wasted into free spaceNeed line of sight.Harmful.

Microwave oven utilizes radiation to cook foods

Nikola Tesla the most well known scientist had a vision of wireless world.

In which wireless electric power and communication would reach around the world, delivering information and power.

WardenclyffeTowerDec 1914US Patent No. :1,119,732

Features and benefits

Witricity’s Technology Technology BenefitHighly resonant strong coupling High efficiency over distance

Energy transfer via magnetic near field

Can penetrate and wrap around obstacles

Non radiative energy transfer Safe for living beings and other environmental objects

Flexible geometry Device that can fit into OEM (original equipment manufactures)products

Scalable design From Mw to kW

Applications

WITRICITY APPLICATIONS

Automatic wireless charging of mobile electronics in home, car, office,...while devices are in use and mobile.

Direct wireless powering of stationary devices…eliminating expensive custom wiring, unsightly cables and “wall-wart” power supplies.

Robots, package machinery, assembly machinery, machine tools.

Direct wireless power and communication interconnections at points of use in harsh environments.

Direct wireless power for wireless sensors and actuators, eliminating the need for expensive power wiring or battery replacement and disposal.

Automatic wireless charging for existing electric vehicle classes: golf carts, industrial vehicles.

Automatic wireless charging for future hybrid and all-electric passenger and commercial vehicles, at home, in parking garages, at fleet depots, and at remote kiosks.

Other Applications Direct wireless power

interconnections and automatic wireless charging for implantable medical devices .

Automatic wireless charging and for high tech military systems.

Direct wireless powering and automatic wireless charging of smartcards.

Direct wireless powering and automatic wireless charging ofconsumer Appliance, mobile robots, etc.

ADVANTAGES No need of line of sight. No need of power cables

and batteries. Does not interfere with

radio waves. Wastage of power is small .Negative health implications.Highly efficient than electromagnetic induction Less costly.

Limitations:

☼ The resonance condition should be satisfied and if any error exists, there is no possibility of power transfer.

☼ If there is any possibility of very strong ferromagnetic material presence causes low power transfer due to radiation.

References• Wireless Power Transfer via Strongly Coupled Magnetic Resonances André

Kurs,Aristeidis Karalis,Robert Moffatt,1 J. D. Joannopoulos,Peter Fisher, Marin Soljacˇic´ .

• Efficient wireless non-radiative mid-range energy transfer Aristeidis Karalis*, J.D. Joannopoulos, and Marin Soljačić Center for Materials Science and Engineering and Research Laboratory of Electronics Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA .

• Magnetic Resonant Coupling As a Potential Means for Wireless Power Transfer to Multiple Small Receivers.