Wireless Power Transmission

By: Yogitha R Malkireddy

Overview of the topics:

1.What is meant by wireless power transmission?

2.Reason to go for WPT3.History of WPT4.Different Kinds of WPT5.Advantages6.Disadvantages7.Conclusion

What is wireless power transmission?

- Transmission of power from one place to another without using conducting devices/wires.

- Generally this is useful where interconnecting wires are inconvenient, and hazardous to handle.

- This is achieved by many different methods. It’s also known as “Witricity”.

Why Wireless Power Transmission?

• It is reliable,• Fast,• Efficient,• Low maintenance cost,• Applicable for both short and long ranges• And also to reduce the energy losses due to

resistance of conducting wires/transmission lines during transmission.

History:

• The idea of WPT was first proposed by Nikola Tesla in 1897.

• He is considered as the pioneer of induction techniques.

• Tesla was successful in transferring energy from one coil to another.

• He was successful in lighting 200 lamps from a distance of 40km.

• Later his ideas were taken into consideration and the phenomenon got named as “Witricity”

Recent improvements and achievements in WPT:

In 2007- MIT was the first to demonstrate about wireless power using resonant near field inductive coupling.In 2008- Intel achieved wireless power transfer using Inductive coupling.Many other charging devices are also invented in recent days for batteries, iPods and mobiles. Example: A mouse pad that can send power through distance of some inches.

Energy Coupling Techniques: The transfer of energy can be done using - Magnetic Coupling- Inductive CouplingInductive Coupling:The primary and secondary coils are not in contact with each other. The transfer of energy takes place due to mutual induction.

*In figure we can observe Transformer coupling which is inductively coupled.

Types of Technologies involved in WPT:Near Field Technologies:1. Inductive Coupling2. Resonant Inductive Coupling3. Air IonizationFar Field:4. Microwave Power Transmission(MPT)5. LASER Power Transmission2. Resonant Inductive Coupling:In this method both resonant and inductance of the coils interact with each other.Resonance generally improves the interaction between both the coils where as inductance induces the current.

3. Air Ionization technique:• This is the toughest technique, because Air ionizes

only when there is high field. (Required field is 2.1MV/m).

• Practically cannot be implemented.• Natural example with high voltages is:

Lightning

Advantages: • Less use of wires.• Shock Proof• Easy to use• Portable• Efficient energy transfer• Maintenance cost is less• Harmless if field strengths are under safety levels.

Disadvantages:• Distance constraint• Field strengths should be taken care all the time• Initial cost is high• To implement RIC tuning is difficult• High frequency must be the supply.

Far Field Energy Transfer1. Microwave Power Transfer: Transfers high

power from one place to another which are in sight.

- This is like a cyclic process where electrical energy is converted to microwave. Microwave collected by rectenna and microwaves are converted to electrical again.2. Laser Power Transmission:• Laser is highly directional.• Gets attenuated when passed through

atmosphere.

Advantages of far field: - Efficient- Easy- Need for grids, substations are eliminated- Low maintenance cost- Effective when Line of sight is perfect- Can reach places which are remoteDisadvantages:

- Need line of sight- Initial cost is very high- Radiative, and absorption loss is high- Interference problem with microwave transmission.• The disadvantage of MPT is, it cannot convert ac

directly to microwave. First it converts to dc then using magnetron dc is converted to Microwave.

Applications:1.To charge mobile phones, iPods and

batteries in short distances. 2.The most important advantage I have

observed is for medical applications.

Example: For the people who use pace makers implanted in their body that runs on a battery.

Conclusion:Since Wireless power transmission is implementable and cost efficient(even initial costs are high) the transmission is effective in this method. Energy losses can be reduced.