PREET KAMAL SINGH M.E. ELECTRONICS ME 14207018 WITRICITY ~ WIRELESS ELECTRICITY PREET KAMAL SINGH M.E. ELECTRONICS ME 14207018

WHAT IS WITRICITY? Transmission of Electrical energy from one object to other without use of wires.

History of Witricity In 1899, 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. The efficient midrange power transfer concept is Witricity.

Need of Witricity: Due to Rapid development of autonomous electronics like laptops, cell-phones etc. devices typically rely on chemical energy storage(Battery) If we adopt this witricity concept to these devices, we may eliminate the problems caused by the battery. We may use this by fixing on our room ceiling to charge our devices wirelessly.

How does Witricity Work? Near-field inductive coupling through magnetic fields. Interact weakly with surrounding objects. 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.

Methods of wireless energy transfer Radiative Methods Omni-Directional Radiation Uni-Directional Radiation Non Radiative Methods Electromagnetic Induction Resonant Coupling

Omni-Directional Radiation : Since radiation spreads in all directions, a vast majority of power would end up being wasted into free space. So radioactive modes of omni directional antennas are not suitable for the Power transfer. Uni-Directional Radiation : can be efficiently used for energy transfer even for long distances but require existence of an uninterruptible line-of-sight Also not Eco friendly.

Electromagnetic Induction The action of an electrical transformer is the simplest instance of wireless energy transfer. The energy is transferred from primary to secondary coil by induction coupling. The main drawback to induction, however, is the short range. The receiver must be in very close proximity to the transmitter or induction unit in order to inductively couple with it.

Examples of Electromagnetic induction The electric toothbrush battery charger. The induction cooker stovetop.

Resonant coupling In 2007 researchers at MIT found a way of increasing the distance between the primary and secondary coil of a transformer by introducing the phenomenon of resonance between the two coils. “Resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied.

How Resonant Coupling actually works

Frequency of Oscillating circuit The frequency of oscillations can be approximated as F = 1 / (2π √(LC) ) Where f = frequency L = inductance C = capacitance

In real-world LC circuits there's always some resistance which causes the amplitude of the current to grow smaller with each cycle, however it does not effect the frequency of the circuit. After a few cycles the current diminishes to zero.  This is called a "damped sinusoidal" waveform.

Where there's a natural frequency there's a way to excite a resonance Where there's a natural frequency there's a way to excite a resonance. We do this by hooking an alternating current (AC) power supply to the circuit.

we have put a resistor back in the circuit we have put a resistor back in the circuit. If there is no resistor in the circuit the current's amplitude will increase until the circuit burns up. As a rule of thumb, a circuit will not oscillate unless the resistance (R) is low enough to meet the following condition: R=2 √(LC)

Disadvantages of resonant coupling Works only in midrange, around 7 to 10 feet. Efficiency is only 40 % .

Advantages of Resonant Coupling No need for direct line of sight. Elimination of power cables and wires. Does not interfere with radio waves. Energy is only transferred between the resonant coils.

No chance of getting an electric shock as the energy transfer only takes place between the resonant objects. The electrical component of the electromagnetic field of the transmitting coil is very small and 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. Only one transmitting source can power up many receiving coils of same resonant frequency.

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

Efficiency can be increased with time, most of the 60% lost is from heat radiated from the coils. Still more efficient than traditional wires.

Witricity Today MIT powered 60 watt light bulb from 2 meters (7 ft) at 40% efficiency MIT researchers working on improving the technology

Witricity Tomorrow 1) Power from mains to antenna, which is made of copper 2) Resonates 10MHz (electromagnetic waves) 3) Tunnel up to 2m (6.5ft) 4) Electricity received by antenna, also resonating at 10MHz. 5) Energy not transferred to laptop re-absorbed by source antenna. People/other objects not affected as not resonating at 10MHz

Applications Wireless power to consumer electronics. Wireless charging for Laptops and Cell phones.

Transportation : Charging pads for electric cars so you don’t have to plug the car in every time you come into the garage.

Conclusion: Witricity is a promising new technology which will finally free us from the hassle of batteries and charging them. It will also help us get rid of all the wires associated with electric appliances. According to the latest research, it is now possible to run an LCD TV without electric wiring.

WORLD IN OUR DREAM

Witricity Concerns Will it harm me? Will it harm the environment? Will it interfere with important communication?

Questions ?

QUIZ SECTION

Q1: NAME THE SCIENTIST WHO PROPOSED THE CONCEPT OF WITRICITY? Ans: Sir Nikola Tesla

Q2: METHODS OF WIRELESS ENERGY TRANSFER ? Ans: 1) Radiative 2) Non-Radiative

Q3: HOW THE ELECTRICITY IS GENERATED IN WITRICITY ? Ans: Resonant Coupling

Q4: WHAT IS EFFICIENCY ACHIEVED IN WITRICITY? Ans: 40%