WiTricity - Definition, working principles and all

WiTricity (Wireless Energy Transfer)

What is WiTricity?

WiTricity is a non-radioactive energy transfer over a distance without any wire. MIT researcher Marin Soljacic describes the ability to provide electricity to a remote object without wire. At first, WiTricity is explored by Nicola Tesla in 1890 by using his demonstration on resonant transformers, Tesla coils. But the strong grip on this idea founded in recent years. WiTricity is now extending its application to medical operations to save the patient’s life, charging electric vehicles at any place. This technology also works in water. So, today we will know some interesting topics of WiTricity - definition, working principles and all others like advantages, disadvantages, and applications, etc.

‘Resonance’ is the property by which the energy transformed. This technology frees us from power cords or wires, the first step towards a smart city. WiTricity technology needs a physical separation between two coils – Power transmitter coil and Power Receiver coils. Power transmission between these coils depends upon the strongly coupled resonance between them. The transmitter coil emits a non-radioactive magnetic field and the receiver coil resonates in that field. The frequency of the resonating magnetic field at MHz. 

Now we will see how it works, application, advantages and disadvantages of WiTricity.

How does it work?

Today technologies are so advanced that electricity can be transferred over a distance wirelessly by various methods. These are the classification of types of energy transfer:

WiTricity is depended on the Resonance Coupling under No-radioactive energy transfer.

Non-radioactive field transfer: Non-radioactive field transfer are wireless energy transmission techniques over distance.

Resonance coupling: Resonance coupling energy transfer works on the principle of a primary coil (Power source coil) generating a predominantly magnetic field and a secondary coil (Power receiver coil) resonates in the magnetic field and a current generated in the coil when both of the coils resonate at the same frequency (or near about the same frequency). The efficiency depends upon their resonating frequencies.

Example: Due to an explosion, the glass windows of nearby buildings can be shattered. This is an example of resonance energy transfer. Here the sound energy converted into vibrating energy. The glasses have their own natural frequency. When the frequency of the explosion will match the frequency of the natural frequency of the glasses, the glasses will vibrate. After a time, the glasses will shatter. This is how a resonance energy transfer works.

Circuit analysis:

The resonance coupled system consists of a high-frequency power source which drives power through a transmitting coil. The transmitting coil sends energy through electromagnetic resonance coupling to the receiver antenna or coil. A pair of similar winding with the same shape and structure is present in the transmitter and receiver to achieve the wireless power transfer.

The induced electric field in the receiver coil is generated by the variation the magnetic field produced by the power transmitter coil. So, the voltages received by the receiver are depended upon the different distances and different frequencies. The frequency range of the source can be 0.01MHz to 10MHz.

The LC tank or LC circuit does not resonate by itself. So, the LC circuit must be driven by an AC power supply. The frequency at which equality is occurred and hold for a particular circuit is called resonant frequency.

In order to achieve resonance frequency in the oscillatory circuit the inductive and capacitive reactance of the resonator coil should be same.

X_L = X_C

Where   ωL = 1 ÷ ωC

And   ω = 2πf

Capacitive reactance,     X_C = 1 ÷ 2πfC

Inductive reactance,     X_{L =} 2πfL

The formula:  4π²f²LC = 1

And    f = 1 ÷ 2π(LC)^1/2

Where

X_L = Inductive reactance in Ohm

X_C = Capacitive reactance in Ohm

f = Frequency in Hertz

L = Inductance in Henry

C = Capacitance in Farads

Features:

The main feature of the technology is its efficiency. The efficiency defined as the power usable over a distance by the receiver to the power input or power supply to the power transmitter coil. In many applications, the efficiency is above 90%.

Efficiency = (power usable over a distance by the receiver) ÷ (The power input or power supply to the power transmitter coil)

The electromagnetic field can be pass through a variety of medium like wood, concrete, plastics, textile, gypsum wallboard.

 

Advantages:

Eco-friendlier: (a) Eliminate the use of removable batteries

(b) More efficient in charging than a normal battery charger

More reliable: (a) Never run out battery power

(b) Less failure due to less wiring

More convenient: (a) Unaffected by weather, day-night cycle

(b) Reduce the cost of setup

 

Disadvantages:

·      ·        There will be no power transform if the resonance frequency of both coils does not match.

·      If there is a ferromagnetic material near it, then power transformation will be low due to radiation. 

Applications:

Being a wireless power transformation technique WiTricity has a wide range of applications. The power transformation in this technique is safe and efficient. WiTricity can be used in:

    1)  Wireless power charging: When in this world everyone demands a wireless technology, WiTricity provide us wireless charging feature in our devices in which no batteries required. The interesting feature is it can charge the device while the device is still in use or at rest. Mobile can be charged in home, office, car and any place automatically.

2)     Direct power to stationary devices: Many stationary devices (like – PC, TV, home theatre, machine tools, keyboard, printer, mouse, etc.) get direct power from the source through WiTricity.

3)     Medical application: Do you know how a pacemaker works? Yes, you are right by the principle of resonance power transfer. WiTricity technique is developed in medical equipment like left ventricular assist device (LVAD) heart assist pumps, pacemaker, and infusion pumps. These devices in the human body consume power through the skin or over a distance greater than the thickness of the skin.

4)     Military application: Because of the wireless charging the military equipment charged at any time. Nowadays military equipment like electronics in the helmet, night vision glasses, and radio devices are charged wirelessly which eliminates the use of power cord and heavy batteries in the military vest.

 

Conclusion:

WiTricity is the mid-range non-radioactive energy transformation technique based on strongly coupled resonance. With respect to distance, the small device has better performance and efficiency. The power transformation totally depends upon the resonance coupling between the coils. Due to its wireless operation, the application is huge.

WiTricity is the future technology to supply power to consumers. Countries demand it to make a smart city. The team of MIT’s next target is to get a robotic vacuum or a laptop working, charging the devices placed anywhere in the room and even the robot vacuum presents on the floor.

 

 - post by Riju Sharma

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