17-01-2013, 11:54 AM
WIRELESS RECHARGING
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ABSTRACT
Today we are surrounded by electronic gadgets and many of them run on electricity from battery as source. Battery makes these electronic gadgets mobile which makes it easy to carry around anywhere we want. But when the power lever of the battery runs low we need to run towards the nearest wired power source to recharge the battery. Now imagine a way through which we can recharge the battery without the wire-recharger. This is possible now through the use of charge pump technology. This technology uses a wireless charger which converts the RF/Microwave frequency waves into DC signal and this energy can be stored in the battery. This term paper focuses on the modalities and technological aspects of the technology. Then we will look into the existing products which already incorporates this technology also some other research areas where electricity can be transmitted wireless. This term paper will end with the future scope of this technology.
INTRODUCTION
We are using electricity for more than a century now and all these years electricity is transmitted through wire cables to commercial and home units. We also use various electronic gadgets which uses electricity through wire cables. Is it possible to done away with wire cables altogether and have free electricity transmission without the physical connection? It is possible through wireless transmission of electricity. The first concept that electricity can be transmitted without wire was demonstrated by Nikola Tesla in 1893 during which he demonstrated the wireless illumination of phosphorescent lamps at world exposition in Chicago. This feat was possible because of electro dynamic induction. Induction is the prime principal used to transmit electricity for shorter distances. Other means like R/F energy is used for short range electricity transmission. Long range electricity transmission can light an entire city. The main advantage of this transmission technique is that we can totally do away with wires which will help us to bring the electricity to nook and corner of the world. Efficiency is the main criteria for this technology. R/F energy transmission is having the least efficiency ratio and induction charger is having the most efficiency.
PROBLEM STATEMENT
The goal of this thesis is to determine if is possible to capture enough power in a cellular phone in order to charge the battery. The requirements for the system to be presented are that it be incorporated into a base station and the operating frequency is set. The design of the board and choice of antenna for the stand are the focal point of the experiments that are to be performed. In order to prove the concept, power needs to be supplied to the energy harvesting circuit by an external transmitter. This transmitter will send a signal at the set frequency. Our test system will then receive this signal through the energy have sting circuit. This circuit is the fundamental design problem of this thesis. This circuit will convert the received signal into voltage to charge the battery. The RF transmitter, the analysis of the cellular phones to be used,A set of experiments will be conducted to demonstrate the feasibility of wirelessly charging a cellular phone battery.
PROPOSED SYSTEM
History of Wireless Charging Technology
• In 1820 Andre Ampere develops Ampere’s law proving that electric current in a metal conductor produces a magnetic field around it.
• In 1931 Michael Faraday develops faraday’s law describing that a magnetic field is induced when a metal is subjected to time varying magnetic field flux.
• In 1983 Nikola Tesla demonstrates the wireless illumination of lamps thus proving the possibility of wireless power transmission.
• In 1897 Tesla got the first patent registered for wireless transmission.
• In 1964 William brown demonstrated a model helicopter flown with a beam of microwave sent from the ground.
• In 1973 world’s first RFID system was demonstrated in Los Alamos National lab.
• In 2008 Intel reproduces Tesla’s 1894 electrodynamics induction and wirelessly powered a bulb with 75% energy efficiency.
• In 2010 Haier Group debuts world’s first completely wireless LCD television based on Tesla’s electrodynamics induction process.
Techniques of Wireless Electricity Transmission
Wireless energy transmission or wireless power transmission (WPT) is different from wireless information transmission; here the electric power is transmitted to a receiver through the use of radio, Laser or a microwave waves. The efficiency or transmission ratio becomes the critical parameter against which various methods are calibrated. In short wireless power transmission is defined as the process through which energy/electricity can be transferred to the conductor without any physical means of contact
SCOPE
This project is based on a very simple concept, capture RF energy using an antenna, input it into a charge-pump and use this energy to power some other circuit. As a precursor to this thesis, there have been many projects involving charge pumps. These projects range from tuning the charge pump to using results from existing charge pumps to drive other circuits. For the tuning projects, usually the testing is done using a light emitting diode (LED). RF energy is transmitted to the circuit and the charge pump stores the energy in a large capacitor.
OBJECTIVE
Wireless energy transfer, also known as wireless energy transmission, is the process that takes place in any system where electromagnetic energy is transmitted from a power source (such as a Tesla coil) to an electrical load, without interconnecting wires. Wireless transmission is employed in cases where interconnecting wires are inconvenient, hazardous, or impossible. Though the physics can be similar (pending on the type of wave used), there is a distinction from electromagnetic transmission for the purpose of transferring information (radio), where the amount of power transmitted is only important when it affects the integrity of the signal.
SYSTEM SPECIFICATION
This research project is primarily empirical. There are many variables in the system that can change the voltage that is developed. The stage capacitors need to be optimized. The number of stages needs to be determined that, combined with the capacitor values for each stage, will result in a sufficiently high voltage level to turn on the phone and charge the phone’s battery. Also, a capacitor can be used across the output as a filter to provide a flat DC signal and store charge. The value of that capacitance also needs to be determined. There really are no fixed parameters for any of these values. The only specified value for any element in this research is the frequency that is being transmitted to the station. This frequency is to be 915MHz
WORKING PROCESS OF WIRELESS CHARGING
Inductive Charging:
Induction is the production of electricity across a conductor situated in a changing magnetic field moving or a conductor moving through a changing magnetic field. When a conductor is subjected through a changing magnetic field a current is induced in the conductor and this current can be stored or used. The transfer of energy takes place by electromagnetic coupling through a process known as mutual induction. This process works only in short distances and can be used to run electric gadgets. The basic wireless changer consists of the units which produces the changing magnetic field in varying degree. These chargers are now commercially available and this can be used to charge any device which uses a battery. Like cell phones, lap tops etc.
CONCLUSION
Transmission of power without wire is not science fiction but a reality now. Without any physical contacts we can transmit power to any distance and run appliances which can be controlled independently. Many companies now have wireless chargers as part of their standard accessory. When Nikola Tesla tried his induction coupling experiments the efficiency was in the range of 20%, now the efficiency has increased to 80 to 90%. This is a very encouraging sign and academia and industry recognize this change and trying to incorporate these solutions in everyday life. Some non-profit organization like Japan’s space agency and European space agency is the process of formulating a plan to send solar power satellite. May be in future the earth’s power requirement may come from these satellites which can beam back power to earth. And one of the best advantage of this technology would be we could get rid of all the cables line which stretch the face of our homes and cities carrying power. Remote corners of our country can enjoy the benefits of electricity as this technology can bring power to their footsteps. The future of wireless transmission/recharging technology looks secured.