WITRICITY (The Wireless Electricity)

Introduction of witricity:

The ability to provide electrical energy to remote objects without wires using oscillating magnetic fields.

 The term WiTricity was used for a project that took place at MIT, led by Prof. Marin Soljačić in 2007

WiTricity is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. This differs from other methods like simple induction, microwaves, or air ionization.

The system consists of transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency

Due to operating in the electromagnetic near field, the receiving devices must be no more than about a quarter wavelength from the transmitter (which is a few meters at the frequency used by the example system). In their first paper, the group also simulated GHz dielectric resonators. The WiTricity devices are coupled almost entirely with magnetic fields (the electric fields are largely confined within capacitors inside the devices), which is argued to make them safer than resonant energy transfer using electric fields (most famously in Tesla coils, whose high electric fields allow them to be used as lightning generators), since most materials couple weakly to magnetic fields (Kurs, 2007)

History of Wireless Power:

àIn 1899, Sir Nikola Tesla Proposed a method of Wireless Power  Transmission.

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

à The efficient midrange power transfer concept is Witricity. In this model source and load are in Magnetic resonance so there is no power loss.

Need of Witricity:

Now a days there is a Rapid development of autonomous electronics like Laptops, Cell-phones, House-hold robots and all those devices typically rely on chemical energy storage(Battery)  As they are becoming daily needs to present generation, Wire less energy transfer would be useful for many applications as above and they need midrange energy. 

Basic Principle:

The basic principle involved in Witricity concept is, Two objects having same resonating frequency and in Magnetic resonance at Strongly coupled regime tend to exchange energy , while dissipating relatively little energy to the extraneous off-resonant objects.

Experimental Design:

Our experimental scheme consists of two Self-resonant coils. One coil (source coil) is coupled inductively to an oscillating circuit; the other (device coil) is coupled inductively to a resistive load. Self-resonant coils rely on the interplay between distributed inductance and distributed capacitance to achieve resonance.  

Electrical Resonance

•Tendency of a circuit system to oscillate at a maximum amplitude for a certain resonance frequency.

•Likely to occur when impedance between input and output is minimized.

•Increases the strength of interaction between two related devices

•Natural Frequency

f =1/2p(LC)0.5

nTypes:

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

1: SHORT RANGE WIRELESS ENERGY TRANSMISSION: INDUCTIVE COUPLING
Inductive Coupling is a method for short range wireless energy transfer. Its range can vary, but it’s often very short. Because of its short range it usually is used when the device containing the receiver and the device containing the transmitter are touching Inductive coupling works on the principles of electromagnetism:

2: MEDIUM RANGE WIRELESS ENERGY TRANSMISSION : RESONANT INDUCTION :

         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" is 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. WiTricity can transmit electricity wirelessly at 40% efficiency to about 7 feet. 

3: Long range; Electromagnetic Wave Power Transfer

 

Simulation model Using COMSOL:

Simulation Performance:

 A By the basic parameters, calculated results and performance given with and Without the External object in between the coils

Project…

There are many projects of wireless energy transfer:

         a) Haier wireless HDTV.

         b) Apple wireless charger.

         c) Car charging technology.

                       and many more…..

a) Haier wireless TV….

Using the wireless and efficient transmission technology to good effect, Haier has developed a completely wireless HDTV. Employing WiTricity and Wireless Home Digital Interface (WHDI), the HDTV is made to stream videos over 100 feet. That’s some distance, when you’re talking of no wires at all,
 

b) Apple wireless Charger….

     An accurate and reliable wireless charging concept is the requirement of the modern technology world. The leading technology innovator Apple has been spending much time to develop an improved method to recharge its devices wirelessly. That is why several of the company’s recent patent applications were related to various kind of wireless charging options

c) Car charging technology…

Toyota and WiTricity to develop new wireless charging tech that requires no contact and WiTricity’s current technology is comparable to standard Level 2 fast charge technology, providing up to 3.3 kilowatts of

 

How safe it is….

HOW SAFE IS WITRICITY ?
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? MIT's researchers are quite confident that WiTricity's coupling resonance' is safe for humans. They say that the 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. 

Future…

MIT's WiTricity is only 40 to 45% efficient and according to Soljacic, they have to be twice as efficient to compete with the traditional chemical batteries. The team's next aim is to get a robotic vacuum or a laptop working, charging devices placed anywhere in the room and even robots on factory floors. The researchers are also currently working on the health issues related to this concept and have said that in another three to five years time, they will come up with a WiTricity system for commercial use. WiTricity, if successful will definitely change the way we live. Imagine cellphones, laptops, digital camera's getting self charged! Wow! Let's hope the researchers will be able to come up with the commercial system soon. Till then, we wait in anticipation!

Advantages…

Safe, fairly efficient, good range.
`Magnetic fields interact weakly with biological masses (humans), and energy is only transmitted between resonating objects. 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.

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.

CONCLUSION

1:The transmission of power without wires is not theory or a mere possibility, it is now a reality. The electrical energy can be economically transmitted without

     wires to any terrestrial distance.

2:   Wireless transmission of electricity have tremendous merits like high transmission

      integrity and Low Loss (90 – 97 % efficient) and can be transmitted to any where

       in the globe and eliminate the need for an inefficient, costly, and capital intensive

       grid of cables, towers, and substations.

3:    The system would reduce the cost of electrical energy used by the consumer and

    get rid of the landscape of wires, cables, and transmission towers. It has

      negligible demerits like reactive power which was found insignificant and 

      biologically compatible.

4:    It has a tremendous economic impact to human society.