Contactless energy transfer system

Submitted To: Submitted By:

Prof. L M Saini Aditi Goyal

Electrical Deptt. Roll No. 107296

NIT Kurukshetra Section – E1

Index

Problems With Conventional Methods

Emergence Of CEET

Different Ways Of Energy Transfer

Inductive Power Transfer

Working Principle

Model Of Magnetic System

Simulation results

Applications

Design methodology

Methods Of Improving Efficiency

References

Problems associated with the conventional methods

Wear and tear on electrical contacts

Exposure to environmental problems

Around 23% of transmission and distribution losses

Also the technology for alternative sources of energy like solar, wind etc are still considered costly.

Emergence of CEET

In 1996, Auckland Uniservices developed an Electric Bus power system using electrodynamic induction and Prof. John Boys Team commissioned 1st commercial IPT Bus in New Zealand.

Prof. Marin Solacic, at MIT, wirelessly powered a 60W light bulb with 40% efficiency at 2 meters with two 60 cm-diameter coils.

What Contactless Energy Transmission Is

Transmission of electrical energy from a power source to an electrical load without interconnecting wires

Large amount of power transmitted is received

Closely related to optimization of transferable power, efficiency and heat development

Elimination of cables, slip rings, plugs and sockets, increasing reliability

Maintenance free operation

Different Ways of Energy Transfer

1. Electromagnetic induction

A) Electrodynamic induction method

B) Electrostatic induction method

2. Electromagnetic radiation

A) Microwave method

B) Laser method

3. Electrical conduction

Electromagnetic Induction

Electrodynamic induction method

This wireless transmission technique is near field over distances up to about one-sixth of the wavelength used. Near field energy itself is non-radiative but some radiative losses do occur. In addition there are usually resistive losses.

Electric current flowing through a primary coil creates a magnetic field that acts on a secondary coil producing a current within it.

Inductive coupling allows power transfer from few mW up to hundred KW

Electrostatic Induction Method

Electrostatic or capacitive coupling is the passage of electrical energy through a dielectric

The capacitive coupling is used in low power range (sensor supply systems)

The electric field is created by an alternating current of high potential and high frequency

Electromagnetic radiation

Microwave method

More directional power transmission via radio waves, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation.

A rectenna is used to convert the microwave energy back into electricity having efficiency greater than 95%

Laser method

Closer to visible region of spectrum (10s of microns (um) to 10s of nm)

Power can be transmitted by converting electricity into a laser beam that is then pointed at a solar cell receiver

Also known as power beaming

Advantages

no radio-frequency interference to existing radio communication

control of access; only receivers illuminated by the laser receive power

compact size of solid state lasers

Disadvantages

Conversion to light, such as with a laser, is inefficient.

Conversion back into electricity is inefficient, with photovoltaic cells achieving 40%-50% efficiency

Atmospheric absorption causes losses.

As with microwave beaming, this method requires a direct line of sight with the target

Electrical Conduction

Actual displacement of charge through earth and atmosphere.

Low frequency alternating current transmitted through earth with low loss because the net resistance of earth is less than 1 ohm.

Electrical conduction through atmospheric strata is made possible by the creation of discharge plasma through the process of atmospheric ionization.

Working Principle Of IPT

Consists of magnetically coupled transmitter coil L1 and a receiver coil L2

Alternating current in transmitter coil generates magnetic field inducing voltage in the receiver coil

Efficiency depends on the coupling (k) between the inductors and their quality (Q)

Model Of Magnetic System

The inductances L(h), L1 and L2 can be obtained by means of a magnetic flux simulation. The inductances can be calculated as described in thefollowing equations:

L(h): main inductance

R1, R2: ohmic resistances

R(L): secondary load resistance

L1, L2: leakage inductances

Results of simulationVariation of main inductance with air gap

Variation of output power and efficiency with load resistance

Variation of output power with air gap length

Variation of output power with transmission frequency

Applications

Powering the Home

Wireless Charging

Defence

Space based Solar Power

Transport

Portable phone battery Charger

Design Methodology

Methods of improving efficiency

Leakage inductance compensation method

Realized by a parallel resonance capacitor or series resonance capacitor at secondary coil

Use Of ferrite cores

improves the magnetic characteristics.

Increases transferable electrical power and

efficiency

Conclusion

Thus we have seen that wireless energy transmission has improvements over the conventional ones. An efficiency greater than 90 % can be realized by using this system. A lot of study is being done in this field. It finds application in many fields like spacecraft propulsion, battery charging and defence. Thus this technology used in combination with the conventional methods can lead to an effective and efficient system.

References

Modelling and design of a contactless energy transfer system for a notebook battery charger Pascal Meyer, Paolo Germano and Yves Perriard Eßer, A.; Nagel, A.: Contactless high speed signal transmission integrated in a compact rotatable powertransformer. European Conference on Power Electronics and Applications, Brighton 1993, Vol. 4, pp 409-414Green, A. W.; Boys, J. T.: 10 kHz inductively coupled power transmission – concept and control.International Conference on Power Electronics and Variable Speed Drives, London 1994, pp 694-699Knaup, P.; Hasse, K.: Zero voltage switching converter for magnetic transfer of energy to movable systems.Hayes, J. G.; Hall, J. T.; Bellino, G.; Conroy, K.: Off-board incuctive charging for the Genaral Motors EV1electric vehicle.