Wireless electricity

intro

wireless electricity  is the process that takes place in any system where electrical energy is transmitted from a power source to an electrical load without interconnecting wires.We ca also call it as Wireless energy transfer or wireless power transmission.

The Need for a Wireless System of Energy Transmission:

A great concern has been voiced in recent years over the extensive use of energy, the limited supply of resources, and the pollution of
the environment from the use of present energy conversion systems.
Electrical power accounts for much of the energy consumed. Much of this
power is wasted during transmission from power plant generators to the
consumer. The resistance of the wire used in the electrical grid
distribution system causes a loss of 26-30% of the energy generated.
This loss implies that our present system of electrical distribution is
only 70-74% efficient.
A system of power distribution with little or no loss would conserve
energy. It would reduce pollution and expenses resulting from the need
to generate power to overcome and compensate for losses in the present
grid system.

The Important laws on which the wireless electricity  based on:

1)Faraday's law
The EMF generated is proportional to the rate of change of the magnetic flux.
2)Faraday's Law, together with Ampere's and Ohm's laws is Lenz's law:
    The emf induced in an electric circuit always acts in such a direction that the current it drives around the circuit opposes the change in magnetic flux which produces the emf.
The direction mentioned in Lenz's law
3)Tesla stated,
 "Instead of depending on [electrodynamic] induction at a distance to light the tube . . . [the] ideal way of lighting a hall or room would . . . be to produce such a condition in it that an illuminating device could be moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically connected to anything. I have been able to produce such a condition by creating in the room a powerful, rapidly alternating electrostatic field. For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal being preferably connected to the ground. Or else I suspend two sheets . . . each sheet being connected with one of the terminals of the coil, and their size being carefully determined. An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous."
and
 “In some cases when small amounts of energy are required the high elevation of the terminals, and more particularly of the receiving-terminal D' may not be necessary, since, especially when the frequency of the currents is very high, a sufficient amount of energy may be collected at that terminal by electrostatic induction from the upper air strata, which are rendered conducting by the active terminal of the transmitter or through which the currents from the same are conveyed."

Methods for wireless energy transfer:

1) induction:
Electromagnetic induction works on the principle of a primary coil generating a predominantly magnetic field and a secondary coil being within that field so a current is induced in the secondary. Coupling must be tight in order to achieve high efficiency.To improve this the addition of resonance
When resonant coupling is used the transmitter and receiver inductors are tuned to a mutual frequency and the drive current is modified from a sinusoidal to a nonsinusoidal transient waveform. Pulse power transfer occurs over multiple cycles. In this way significant power may be transmitted over a distance of up to a few times the size of the transmitter. Unlike the multiple-layer windings typical of non-resonant transformers, such transmitting and receiving coils are usually single layer solenoids or flat spirals with series capacitors, which, in combination, allow the receiving element to be tuned to the transmitter frequency and reduce losses.
2)electromagnetic transmission:
Electromagnetic waves, commonly known as light, can also be used to transfer power wirelessly. By converting electricity into light, such as a laser beam, then firing this beam at a receiving target, such as a solar cell on a small aircraft, power can be beamed to a single target. This is generally known as “power beaming”. There are several drawbacks to this, however. First, the conversion to light, such as a laser, is usually very inefficient.
3)Evanescent wave coupling:
The "electrostatic induction effect" or "capacitive coupling" is an electric field gradient or differential capacitance between two elevated electrodes over a conducting ground plane for wireless energy transmission involving high frequency alternating current potential differences transmitted between two plates or nodes. The electrostatic forces through natural media across a conductor situated in the changing magnetic flux can transfer energy to a receiving device

Advantages:

(1)    Wireless energy transfer can potentially recharge laptops, cell phones without chords.
(2)    No need of the wires to transfer the electricity.
(3)    Although, the energy is different, the appliances use a very little amount.

Disadvantages:

(1)    The transmitter and receiver also should be very powerful devices as the distance increases.
(2)    Wireless transmission of the energy causes some drastic effects to human body, because of its radiation.
(3)    Practical possibilities are not yet applicable as there is no much advancement in this field.
(4)    Initially, the procedure will be very expensive.
(5)    All the present appliances can’t be attached with a transmitter and receiver.

Uses:

The wireless transfer of energy is used in various devices, such as electric toothbrushes (to recharge their batteries), the transcutaneous energy transfer (TET) systems in artificial hearts like AbioCor and most notably in mobile phones.

Future vision:

A fully developed World System would, conceivably, allow for the removal of many existing high-tension power transmission lines, and facilitate the interconnection of electrical generation plants on a global scale. 
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