**1.2 Methods**

*Wireless Power Transfer – Recent Development, Applications and New Perspectives*

device or gadget, microwaves can be used to send electro-magnetic radiation. The method of resonance can be applied at certain frequencies to cause an object to oscillate by electro-magnetic radiation. These oscillations can be used to transfer energy between two oscillating sources. The satellite in space with solar cells can be used to capture the solar energy and transmit this energy back to earth. This method would involve the conversion of radio waves frequencies into electrical power and electrical power into radio waves frequencies. The main purpose of the solar photovoltaic system is to distribute the collected electrical energy in various small-scale power applications wirelessly. These recent developments give technology based on how to transmit electrical power without any wires, with a small-scale by using solar energy. Wireless power transfer (WPT) using solar energy technology is having vast applications. The ability of technology is to transfer power efficiently, safely over distance can improve gadgets and products by making them more reliable, climate and environment benign. Wireless power transfer (WPT) can be used in various applications for example in automatic wireless charging, direct wireless power supply of devices such as cellphones, loudspeakers, digital picture frames, flat screen TV's, home theater accessories etc. [1]. The power can also be transferred wirelessly through an inductive coupling as an antenna. With this wireless electricity we can charge and make wireless electricity as an input source to electronic equipment such as Handphone, MP3 Player etc. In harvesting energy, technologies of ambient solar radiation like solar photovoltaic, kinetic, thermal or electro-magnetic (EM) energy can be used to recharge the batteries. Radio frequency (RF) harvesting technologies are also popular as they are enormously available in the atmosphere. The energy converted to useful DC energy which can be used to charge electrical devices which

This chapter outlines the recent developments of wireless power transfer using solar energy. The rest of the chapter contains brief history of the development of wireless power transfer. Various methods and technologies used in wireless power transfer are outlined. The State-of-the-Art of Wireless Power Transfer using Solar Energy is also described along with the literature review. The later part of the chapter contains novel concept of transmitter design of a parallel plate photovoltaic amplifier device integrated in a Building. The design of a receiver using radio waves for wireless information and power transfer is also briefly discussed. Conclusions and equations for design of a transmitter and a receiver are provided in the later part of the chapter.

The presence of electro-magnetic waves by devising a mathematical model is predicted by James C. Maxwell in 1864. The Poynting Vector would play an important role in quantifying the electromagnetic energy (John H. Poynting, 1884). Heinrich Hertz first succeeded in showing experimental evidence of radio waves by his spark-gap radio transmitter in 1888, which was bolstered by Maxwell's theory. The wireless power transfer was started by the prediction and evidence of the radio wave in the end of 19th century. Wireless power transfer of electrical power was pioneered by Nikola Tesla [2]. He conducted experiments on wireless power in 1891 at his "experimental station" at Colorado. A small incandescent lamp by means of a resonant circuit grounded on one end was successfully lighted by Nikola Tesla [3]. The lower end connected to the ground and the upper end free with a coil outside his laboratory. The current was induced in the three turns of wire wound around the lower end of the coil and the lamp was lighted. For trans-Atlantic wireless telephony and demonstration of wireless electrical power transfer by means of Wardenclyffe tower, which was designed by Tesla. The modern development of microwave power transmission which dominates research and development of wireless power transfer

**10**

**1.1 History**

need low power consumption.

**Radio and Microwave:** Typically, in the microwave range, wireless power transfer via radio waves can be made over longer distance power beaming, with shorter wavelengths of electromagnetic radiation with more directional component. To convert the microwave energy back into electricity, a rectenna may be used. Conversion efficiencies exceeding 95% have been realized with rectenna. For the transmission of energy from orbiting solar power satellites to Earth and the beaming of power to spacecraft leaving orbit, power beaming using microwaves has been considered [4].

**Electromagnetic Transmission:** Electromagnetic waves can also be utilized for wireless power transfer. Power beaming can be employed 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.

**Induction:** For the transfer of wireless electrical power, the principle of mutual induction between two coils can be used. Electromagnetic coupling between the two coils is used to transfer the energy. The simplest example of how mutual induction works is the transformer, where there is no physical contact between the primary and the secondary coils.

**Electrodynamic Induction:** Resonant inductive coupling for wireless power transfer resolves the main problem associated with non-resonant inductive coupling. It has dependence of efficiency on transmission distance. The transmitter and receiver inductors are tuned to a mutual frequency and the drive current is modified from a sinusoidal to a non-sinusoidal transient waveform with the use of resonant coupling. Pulse wireless power transfer occurs over multiple cycles. Significant wireless power may be transmitted over a distance of up to a few times the size of the transmitter with this method.

**Electrostatic Induction:** For wireless energy transfer involving high frequency alternating current potential differences transmitted between two plates or nodes, capacitive coupling is utilized with an electric field gradient or differential capacitance between two elevated electrodes over a conducting ground plane.
