Wireless Electricity (WiTricity)

This principle was invented by Tesla.

Wireless Electricity is called WiTricity. Transmission of electrical energy from one object toanother without the use of wires is called as WiTricity. WiTricity will ensure that the cellphones, laptops, iPods and other power hungry devices get charged on their own, eliminating the need of plugging them in. Even better, because of WiTricity some of the devices won't require batteries to operate.

The basic model of this is shown in below image.

As you can see in the figure that two magnetic coils are coupled with each other. One is energy transmitter and other is receiver. The concept behind this is as below.

Consider two self resonating copper coils of same resonating frequency with a diameter 20 inches each. One copper wire is connected to the power source (WiTricity transmitter), while the other copper wire is connected to the device (WiTricity Receiver).

The electric power from the power source causes the copper coil connected to it to start oscillating at a particular (MHz) frequency. Subsequently, the space around the copper coil gets filled with nonmagnetic radiations. This generated magnetic field further transfers the power to the other copper coil connected to the receiver. Since this coil is also of the same frequency, it starts oscillating at the same frequency as the first coil. This is known as 'coupled resonance' and is the principle behind WiTricity.

With the help of this concept we can recharge our devices without wires.

We can use this concept to transfer energy from solar plates in the satellite to earth directly without wires. The possible model for this is shown in the image.

These solar plates absorb energy from sun in space. This energy is transmitted to earth where the huge receiver is located. We can understand this by below figure.

In this figure we can consider transmitting antenna as transmitting satellite. And rectena( receiving antenna) as huge receiver at the earth.

However the efficiency of this is low. So it is hard for this technique to compete with present scenario.