Title: Wireless Power Transmission – For Sophisticated Future
Authors: Y.Geetha Rani & P.Pravallika, 3rd Year BTech, EEE
College: Dr.L.B.College of Engineering for Women
ABSTRACT:
We are aware of that the use of technology is being increased day by day. Also, the techniques to inplement this technology is also increasing rapidly. The most common problem is charging the gadets or what so ever. Sometimes you may have the use of charging multiple devices at a time which is impossible with a single wired charger connected to a single plug. To overcome this, a new technology called wireless power transmission has emerged. Power can be transferred through a power former without any contact between the transformer and receiver which reduces the complexity in this process and is also use in charging more than one device at a time.
INTRODUCTION:
Generally, power transmission is done using cables, wires, cords etc. we probably have a few dusty cord tangles around our home. This is one of the downfalls of electricity. While it can make people’s lives easier, it can add a lot of clutter in the process. You may have even had to follow one particular cord through the seemingly impossible snarl to the outlet hoping that the plug you pull will be the right one.
Emerging science and technology have brought techniques to avoid bulky usage of wires and cables for power transmission and we say it WIRELESS POWER TRANSMISSION.
This technique of transmission is basically depended on the distance between the transmitter and the receiver.
The classification goes as –
• Short distance range
• Moderate distance range
• Long distance range
SHORT DISTANCE RANGE :
This transmission technique is done usually when the transmitter and receiver are distanced at few centimeters. The action of electric transformer is basic need for wireless energy transfer.
The electric toothbrush charger is an example of how this principle can be used. A toothbrush’s daily exposure to water makes a traditional plug-in charger potentially dangerous. Ordinary electrical connections could also allow water to seep into the toothbrush, damaging its components. Because of this, most toothbrushes recharge through inductive coupling.
For example, A Splashpower mat uses induction to recharge multiple devices simultaneously.
Electronic devices use corresponding built-in or plug-in receivers to recharge while resting on the mat. These receivers contain compatible coils and the circuitry necessary to deliver electricity to devices’ batteries
MODERATE DISTANCE RANGE:
This transmission technique is done usually when the transmitter and receiver are distanced at few meters. The devices used for domestic purposes have very low magnetic fields. For this reason the coils are placed close together. A larger, stronger field could induce current from farther away, but the process would be extremely inefficient. Since a magnetic field spreads in all directions, making a larger one would waste a lot of energy. To overcome this an additional property called RESONANCE is added to the present system.
Induction can take place a little differently if the electromagnetic fields around the coils resonate at the same frequency. The theory uses a curved coil of wire as an inductor. A capacitance plate, which can hold a charge, attaches to each end of the coil. As electricity travels through this coil, the coil begins to resonate.
Its resonant frequency is a product of the inductance of the coil and the capacitance of the plates.
As long as both coils are out of range of one another, nothing will happen, since the fields around the coils aren’t strong enough to affect much around them. Similarly, if the two coils resonate at different frequencies, nothing will happen. But if two resonating coils with the same frequency get within a few meters of each other, streams of energy move from the transmitting coil to the receiving coil. According to the theory, one coil can even send electricity to several receiving coils, as long as they all resonate at the same frequency. The researchers have named this non-radiative energy transfer since it involves stationary fields around the coils rather than fields that spread in all directions.
According to the theory, one coil can recharge any device that is in range, as long as the coils have the same resonant frequency.
LONG DISTANCE RANGE:
This transmission technique is done usually when the transmitter and Receiver are distanced at few meters.Induction generally sends power over relatively short distances. But some plans for wireless power involve moving electricity over a span of miles. A In the 1980s, Canada’s Communications Research Centre created a small airplane that could run off power beamed from the Earth. The unmanned plane, called the Stationary High Altitude Relay Platform (SHARP), was designed as a communications relay. Rather flying from point to point, the SHARP could fly in circles two kilometers in diameter at an altitude of about 13 miles (21 kilometers). .
The secret to the SHARP’s long flight time was a large, ground-based microwave transmitter. The SHARP’s circular flight path kept it in range of this transmitter. A large, disc-shaped rectifying antenna, or rectenna, just behind the plane’s wings changed the microwave energy from the transmitter into direct-current (DC) electricity. Because of the microwaves’ interaction with the rectenna, the SHARP had a constant power supply as long as it was in range of a functioning microwave array.
Rectifying antennae are central to many wireless power transmission theories. They are usually made an array of dipole antennae, which have positive and negative poles. These antennae connect to shottkey diodes. Here’s what happens:
1. Microwaves, which are part of the electromagnetic spectrum reach the dipole antennae.
2. The antennae collect the microwave energy and transmit it to the diodes.
3. The diodes act like switches that are open or closed as well as turnstiles that let electrons flow in only one direction. They direct the electrons to the rectenna’s circuitry.
4. The circuitry routes the electrons to the parts and systems that need them.
CONCLUSION: The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost. With such a design, power transfer for laptop-sized coils are more than sufficient to run a laptop can be transferred over room-sized distances nearly omni-directionally and efficiently, irrespective of the geometry of the surrounding space, even when environmental objects completely obstruct the line-of-sight between the two coils.As long as the laptop is in a room equipped with a source of such wireless power, it would charge automatically, without having to be plugged in. In fact, it would not even need a battery to operate inside of such a room.” In the long run, this could reduce our society’s dependence on batteries, which are currently heavy and expensive. At the same time for the long range power transmission, power can be sent from source to receivers instantaneously without wires ,reducing the cost.
References:
1. Benson, Thomas W., “Wireless Transmission of Power now Possible”
2. U.S. Patent 787,412, “Art of Transmitting Electrical Energy through the Natural Mediums”.
3. U.S. Patent 2,415,688, “Induction device”
4. “‘Evanescent coupling’ could power gadgets wirelessly”, NewScientist.journal