Various new technologies are being developed for transmitting power through wireless systems and one of the ways to transmit electricity without wire is through the microwave transmission. The process of transmitting the power using microwaves is called as Microwave Power Transmission.This will cause reduction in the transmission and distribution losses. This paper will give the idea about impact on human beings, advantages, disadvantages, & applications of wireless power transmission.
Keywords: Wireless power transmission (WPT),
Microwave power transmission (MPT), Wireless Sensor network (WSN).
Wireless power transfer is the transmission of the energy over a distance without, the usage wires or cables, wherein distances involved may be short or long. Researchers have developed a number of techniques for moving electricity over long distance exclusive of wires. This paper provides the techniques used for wireless power transmission. It is a common term that refers to a number of dissimilar power transmission technologies that use the time to shift electromagnetic fields.
Wireless power transmission is used to power electrical devices in the case where interconnecting wires are not achievable, hazardous, or are not convenient. For example, the life of WSN is its node which consists of several device controllers, memory, transceivers, sensors, actuators, and battery. The transceiver has four states, i.e. 1) Transmit 2) Receive 3) Idle and 4) Sleep. The major energy trouble of a transmitter of a node is consuming a great amount of power its receiving in an idle state, as in this state it is always being prepared to receive.
However, the batter has a very short lifetime and moreover in some developments owing to both practically and economically infeasible or may involve significant resists to human life. That is why energy harvesting for WSN in replacement of the battery is the only and unique solution. During wireless power transfer, a transmitter device source, such as the mains power stripe, transmits power via electromagnetic fields diagonally an intervening gap to one or more receiver devices, where it is converted back to electric power and utilized. In communication the objective is the transmission of information, so the amount of power reaching the receiver is insignificant as long as it is enough to facilitate signal to noise ratio is high enough that the information can be received intelligibly. In wireless communication technologies, generally, only tiny amounts of power reach the receiver. By distinction, in wireless power, the quantity of power received is the important thing, so the efficiency (fraction of the transmitted power that is received) is the more significant parameter.
Figure 1.1 Microwave Region of Electromagnetic Spectrum
Figure 1.1 shows that the microwaves are the radio signal which has the wavelength array of 1 mm to 1 meter and the frequency is 3000 MHZ to 300 GHZ. Microwaves contain wavelength that preserves is calculated in centimetres microwaves are good quality for transmitting information from one place to another place because microwave energy be able to penetrate haze, snow, clouds, light rain, and smoke. Microwave radiation is still connected with an energy level that is typically nontoxic except for people with pacemakers.
II. EXISTING METHOD
Possible methods of wireless transmission of electrical power
A. Inductive coupling
C. Radio frequency
A. Inductive coupling
In this when transmitting coil is excited then it generates flux and when receiver coil receives this flux a potential difference is developed across its terminal. This is the basic model and its efficiency is very poor hence cannot be used for large distance transmission.
It is a device which emits light based on the stimulated emission of electromagnetic radiation. Power can be transmitted by means of converting electricity keen on the laser beam. But in this the laser radiation is hazardous and conversion between electricity and light is ineffective.
C. Radio frequency
Radio frequency signals to direct current electrical current powered from either an international or ambient power sources.
III. PROPOSED METHOD:
Figure 1.2 block diagram
The figure 1.2 shows that the purposeful block diagram of WPT consists of two sections: transmitting section and receiving section.
Figure 1.3 shows the transmission section, the microwave power source generates microwave power which is prohibited by the electronic control circuits. The waveguide circulator protects the microwave resource from the reflected power, which is connected through the co-ax waveguide adaptor. The tuner contests the impedance between the microwave source and transmitting antenna. Then, based on the signal broadcast direction, the attenuated signals are separated by the directional coupler. The transmitting antenna emits the power frequently through open space to the receiving antenna.
Figure 1.3 shows the receiving element, the receiving antenna receives the transmitted power and converts the microwave power into DC power. The impedance matching circuit and filter is provided for locating the harvest impedance of a signal source which is equivalent to rectifying circuit. This circuit consists of Schottky barrier diodes which convert the received microwave power keen on DC power.
Figure 1.3 Transmitting and Receiving Sections
A rectenna is a rectifying circuit, a special type of antenna that is used to convert microwave energy into DC current. Its elements are usually aligned in a mesh pattern, to offer a distinct appearance from most antennae. We can construct simple rectenna by using a Schottky diode placed between antenna dipoles. The diode (a uni -direction device) rectifies the current induced in the antenna by the microwaves signals. Rectenna is highly efficient for converting microwave energy into electricity. In laboratory environments, efficiencies above 90% have been observed. Scientists also tried to convert electricity into microwave energy using inverse rectenna, but efficiencies are very low. Only in the area of 1%. With the advent of nanotechnology and MEMS, the size of rectenna elements can be brought down to the molecular level. A rectenna consist of a mesh of dipoles and a mesh of diodes for absorbing microwave energy from a transmitter and converting it into electric current.
In emergent, this design, the PBG antenna, DGS LPF, and rectifier circuits were every first fabricated, designed, and characterized alone.
The rectenna is a passive element which consists of an antenna, rectifying circuit with a low pass filter between the antenna and rectifying diode.Schottky Barrier diodes(GaAs-W, Si, GaAs) are usually used in the rectifying circuit due to the fast reverse recovery time and lower forward voltage drop and good RF characteristics.The rectenna efficiency for various diodes at a different frequency is shown in table 1.1.
Table 1.1 Rectenna Efficieny For Various Diodes at Different Frequency
Figure 1.4 Rectenna Design
Figure 1.4 shows the rectenna used in the project. Rectenna has divided two copper plates with Schottky diode which acts as a resistor between two plates. Likewise, we have positioned 10 setups in parallel such that we have placed 10 resistors in parallel which intone act as the conductor with high absorption power since resistors in parallel act as a conductor.
Table 1. 2 Distance Covered Vs Voltage
In table 1.2 we have presented the wireless power transmission with distance and voltage in which when the distance increases the voltage get decreased. This is shown in figure1.5. The decrease in voltage absorbed by the rectenna is due to distortion of microwaves in the air medium.
Figure 1.5 Distance Vs Voltage Curve
IV. ADVANTAGES AND DISADVANTAGE
1. Entirely eradicate the existing high-power transmission line towers, cables etc…
2. The transmission and distribution cost becomes less.
3. Hence, the efficiency of this method is very much higher than wired transmission.
4. The power failure as a result of short circuit and fault of cables would never be present.
5. The power can be transmitted to the places where the wired transmission is not a feasible.
6. Capability to charge vehicles such as for industrial vehicles and golf carts.
7. Substantiate and alter to loads.
1. Still under production and development.
2. It does not give sufficient energy to charge enormous vehicles and types of equipment.
3. Transmitting distance is unreliable.
4. Heat loss takes place.
5. The intervention of microwaves with a present signal.
1. Used in cordless tools, automatic wireless charging for mobile robots and instrument this eliminates complex mechanism.
2. Easy and neat Installation – there is no cable running here and there, just start up the wireless device.
3. Mobility – within the wireless range user device can be moved easily.
4. The ability of our technology to transfer power efficiently, safely and over distance can improve products by making them more reliable, convenient, and environmentally friendly.
Wireless Power Transmission (WPT) was successfully achieved up to the distance of 1 meter and beyond with the help of the high power rectenna and proposed with higher lumens. It is difficult to find inductors and capacitors that are capable of working at higher power levels. However, safety is needed to be concern for the further extension of the project and modification is required for higher end design. Configuration on the cost factor and design constraints, including noise factor are to be considered and suggested to concern for the further development.
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