“Wireless Electricity”

PRESENTED BY: SHAIK SARTAJ AHMED

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

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

On June 7 ’07, a team of researchers at MIT announced the successful operation of WiTricity concept.

They had lit up a 60W bulb with a power source at a distance of 7 feet(over 2m) with no wires.

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

Forgotton invention was reborn in 2007

In 1891, Sir Nikola Tesla Proposed a method of Wireless Power Transmission.

As it is in Radiative mode, most of the Power was wasted and has less efficiency.

In 1891, Nikola Tesla invented a type of resonant transformer called the Tesla coil, which was used to generate very high voltage, low current, and high frequency alternating electricity. He experimented with a large variety of coils and configurations, one of which is as:

In1899,Tesla achieved a major breakthrough in his work at Colorado by transmitting 100 million volts of electric power wirelessly over a distance of 26 miles to light up a bank of 200 light bulbs and run one electric motor.

Cell phones, i pods, laptop computers are capable of re-charging themselves without ever being plugged in.

Currently, wired electricity powers have concured nearly everything.

In present electricity generation system we waste more than half of its resources. Especially the transmission and distribution losses are the main concern of the present power technology.

The resistance of the wire used in the electrical grid distribution system causes a loss of 26-30% of the energy generated

The transmission of power without wires may be one noble alternative for electricity transmission.

Prof. Marin Soljacic from Massachusetts Institute of Technology (MIT), is the one who has proved that magnetic coupled resonance can be utilized in order to transfer energy without wires.

He used Michael Faraday's principle of electromagnetic induction (1831) came up with WiTricity.

There are 3 major types of wireless energy transfer: – Short range; Inductive Coupling – Medium range; Resonant Induction – Long range; Electromagnetic Wave Power

Transfer

What Is Inductive Coupling? Inductive Coupling is a method for short

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

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.

Resonant induction still uses the same principles as magnetic induction (magnetic fields to transfer current) , but it uses resonance to increase the range at which the transfer can efficiently take place.

“Resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied.

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

Energy transfers easily between resonating objects. An example of this is when an opera singer shatters wine glasses by singing at the frequency at which the glasses resonate.

With resonant induction, power is transmitted between two resonating coils.

Consider two self resonating copper coils of same resonating frequency with a diameter 20 inches each. One copper wire is connected to the power source , while the other copper wire is connected to the device.

A Tesla Coil produces high voltage electric arcs. These arcs cause permanent damage to electrical devices on contact

Tesla coils also destroy hearing aids and cardiac pacemakers in their vicinity.

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?

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

Efficiency is mesured by measuring the current at the midpoint of the self resonant coils with a current probe.

This gives a measurement of the current parameters

We then compute power dissipated in each coil from:-

Then the efficiency can be calculated .

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 its WiTricity power source

Consumer Electronics

Industrial

Transportation

Miscellaneous

Will it harm me? Will it harm the environment? Will it interfere with important

communication?

Human beings or other objects placed between the transmitter and receiver do not hinder the transmission of power.

However, does magnetic coupling or resonance coupling have any harmful effects on humans?

magnetic fields tend to interact very weakly with the biological tissues of the body, and so are not prone to cause any damage to any living beings.

Safe, fairly efficient, good range: Magnetic fields interact weakly with

biological masses (humans), Efficiency can be increased with time, most

of the 60% lost is from heat radiated from the coils.

Theoretically one stationary coil in a room could power multiple devices with receiving coils.

No more messy wires, and with widespread enough use it could even eliminate costly batteries.

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.

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.

1. An article published in the Science Magazine as “Wireless Power Transfer via Strongly Coupled Magnetic Resonances” by Andre kurs, Science 317, 83(2007); Dol:10.1126/ science.1143254.

2. H. Haus , “Waves and Fields in Optoelectronics”, Prentice hall Publishers, Englewood

3. http://electron9.phys.utk.edu/optics507/modules/m6/coupled_resonators.htm

4. “Efficient Non-Radiative Midrange Energy Transfer” by Aristeidies karalis, Marlin Soljacic.

5. Nikola Tesla, My Inventions, Ben Johnston, Ed., Austin, Hart Brothers, p. 91,1982.

6. Thomas F. Valone, “ Tesla’ s Wireless Energy... For the 21st Century!!! One Step Beyond Direct TV!!!” Extra Ordinary Technology, 1, no. 4, Oct / Nov / Dec 2003.

7. James O. McSpadden, “ Wireless Power Transmission Demonstration”, Texas A&M University, June, 1997.

8. Charych Arthur (Setauket, NY), “ System and method for wireless electrical power transmission”, Patent No. 6,798,716, September 28, 2004.

9. Joe T. Howell, et. al , “Advanced receiver / converter experiments for laser wireless power transmission”5th. Wireless transmission conference, pp 1-8, Garanda, Spain,2004.