Since a magnetic field spreads in all directions, making a larger one would waste a lot of energy The distance between the coils can be extended by adding resonance to the equation. A good way to understand resonance is to think of it in terms of sound. An object's physical structure -- like the size and shape of a trumpet -- determines the frequency at which it naturally vibrates. This is its resonant frequency. It's easy to get objects to vibrate at their resonant frequency and difficult to get them to vibrate at other frequencies.
This is why playing a trumpet can cause a nearby trumpet to begin to vibrate. Both trumpets have the same resonant frequency. Induction can take place a little differently if the electromagnetic fields around the coils resonate at the same frequency. The theory uses a curved coil of wire as an inductor. A capacitance plate, which can hold a charge, attaches to each end of the coil.
As electricity travels through this coil, the coil begins to resonate. Its resonant frequency is a product of the inductance of the coil and the capacitance of the plates. The MIT wireless power project uses a curved coil and capacitive plates As with an electric toothbrush, this system relies on two coils. Electricity, traveling along an electromagnetic wave, can tunnel from one coil to the other as long as they both have the same resonant frequency.
The effect is similar to the way one vibrating trumpet can cause another to vibrate. As long as both coils are out of range of one another, nothing will happen, since the fields around the coils aren't strong enough to affect much around them.
Similarly, if the two coils resonate at different frequencies, nothing will happen. But if two resonating coils with the same frequency get within a few meters of each other, streams of energy move from the transmitting coil to the receiving coil. According to the theory, one coil can even send electricity to several receiving 12 Department of EEE. The researchers have named this non- radiative energy transfer since it involves stationary fields around the coils rather than fields that spread in all directions.
This kind of setup could power or recharge all the devices in one room. Some modifications would be necessary to send power over long distances, like the length of a building or a city B Far field: Means for long conductors of electricity forming part of an electric circuit and electrically connecting said ionized beam to an electric circuit.
These methods achieve longer ranges, often multiple kilometre ranges, where the distance is much greater than the diameter of the device s. Radio and micro wave transmission : Power transmission via radio waves can be made more directional, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in the microwave range.
A rectenna may be used to convert the microwave energy back into electricity. Power beaming using microwaves has been proposed for the transmission of energy from orbiting solar power satellites to Earth and the beaming of power to spacecraft leaving orbit has been considered.
Power beaming by microwaves has the difficulty that for most space applications the required aperture sizes are very large. These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. For earthbound applications a large area 10 km diameter receiving array allows large total power levels to be used while operating at the low power density suggested for human electromagnetic exposure safety.
This is the power level found in many modern electric power plants. High power: Wireless Power Transmission using microwaves is well proven.
Experiments in the tens of kilowatts have been performed, achieving distances on the order of a kilometer. This could include LEDs, computer peripherals, wireless sensors, and medical implants.
Currently, it achieves a maximum output of 6 volts for a little over one meter. Laser: With a laser beam centered on its panel of photovoltaic cells, a lightweight model plane makes the first flight of an aircraft powered by a laser beam inside a building at NASA Marshall Space Flight Center. In the case of light, power can be transmitted by converting electricity into a laser beam that is then fired at a solar cell receiver.
This is generally known as "power beaming". Its drawbacks are: 1. Conversion to light, such as with a laser, is moderately inefficient although quantum cascade lasers improve this 2. Atmospheric absorption causes losses. As with microwave beaming, this method requires a direct line of sight with the target.
Electrical conduction: Electrical energy can also be transmitted by means of electrical currents made to flow through naturally existing conductors, specifically the earth, lakes and oceans, and through the atmosphere — a natural medium that can be made conducting if the breakdown voltage is exceeded and the gas becomes ionized. For example, when a high voltage is applied across a neon tube the gas becomes ionized and a current passes between the two internal electrodes.
In a practical wireless energy transmission system using this principle, a high-power ultraviolet beam might be used to form a vertical ionized channel in the air directly above the transmitter-receiver stations. The same concept is used in virtual lightning rods, the electrolaserelectroshock weapon and has been proposed for disabling vehicles. Through longitudinal waves, an operator uses the Tesla effect in the wireless transfer of energy to a receiving device.
The Tesla effect is the application of a type of electrical conduction that is, the movement of energy through space and matter; not just the production of voltage across a conductor.
I have been able to produce such a condition by 15 Department of EEE. 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.
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. Radio waves are energy, and people use them to send and receive cell phone, TV, radio and Wi-Fi signals every day. The radio waves spread in all directions until they reach antennae that are tuned to the right frequency. This method for transferring electrical power would be both inefficient and dangerous.
Researchers have outlined a relatively simple system that could deliver power to devices such as laptop computers or MP3 players without wires. The concept exploits century-old physics and could work over distances of many metres, the researchers said.
A UK company called Splashpower has also designed wireless recharging pads onto which gadget lovers can directly place their phones and MP3 players to recharge them. The pads use electromagnetic induction to charge devices, the same process used to charge electric toothbrushes. Resonant inductive wireless energy transfer was used successfully in implantable medical devices including such devices as pacemakers and artificial hearts.
While the early systems used a resonant receiver coil later systems implemented resonant transmitter coils as well. A short summary of this paper. Download Download PDF. Translate PDF. Pravat Ku. Name of the guide- Prof. Last but not the least I express my sincere and hearty thanks to all those who have directly or indirectly helped me in completing this seminar presentation and report successfully.
How WPT technology works 6. However, this is also an age where mobile phones, MP3 players, laptop computers and domestic robots exist alongside old- fashioned power wires and bulky batteries. Unlike information, electrical energy is still physically confined to these borderline anachronistic appliances. Overcoming these last obstacles would finally make this a truly wireless world.
It was the annoying reminder that the battery was running out, once again. The next morning, he returned to his office at the MIT determined to find a solution to the problem.
An exhaustive literature search soon revealed that wireless transmission of power was not an original idea. Back in the s Nikola Tesla, one of great pioneers of electromagnetism, was the first to envisage that electricity, then a newly found form of energy, should be delivered to every house, in every city, in every country on the planet. However, Tesla did not foresee that people would be willing to drag wires around the entire globe to use electricity.
Instead, he dreamed of a way of transferring electrical energy wirelessly over long distances. The construction was interrupted in about , not because the method was considered impractical or dangerous, but because the funder, the famed financier and banker J P Morgan, was concerned that there would be no way to bill remote electricity users.
Nowadays, more than a century after Tesla, electricity reaches nearly every home through a global electrical grid. In the near future, wireless electricity could replace the ubiquitous power cable.
Rauscher calculates the capacitance to be about 15, microfarads for the complete earth-ionosphere cavity capacitor. In comparison to the 3 billion kW available from the earth system, it is possible to calculate what the U. In , about 11 Quads quadrillion Btu were actually used by consumers for electrical needs, which is equal to 3.
Dividing by the hours in a year, we find that only million kW are needed on site to power our entire country. This would still leave 2. The reallyshameful U. No other energy production system of any kind in the world has so much wastefulness. Instead of trying to build 2 power plants per week at MW each for the next 20 years only to have a total of additional 6 trillion kWh available by , as some U.
Fig-1 losses in the wired system 2. Wireless power transmission can supply power to places that are difficult to reach. Especially small communities in rural areas could be supplied with power using WPT. In this way the cost associated with deploying towers and cables can be saved. These two words have become the base for the development in the technology.
Moreover it does not involve any emission of carbon gases. Many countries can enjoy the economic benefits of this technology. A signal resonant energy receiver is an ultimate device to connect various electrical applications.
Patent , describing a system for power transfer at 3 kHz. Houston Street laboratory in New York City by means of "electrodynamic induction," that is to say wireless resonant inductive coupling.
Reginald Fessenden - U. Patent Interference No. Louis World's Fair, a prize is offered for a successful attempt to drive a 0. Brown publishes an article exploring possibilities of microwave power transmission. John Boys at The University of Auckland in New Zealand, develops an inverter using novel engineering materials and power electronics and conclude that power transmission by means of electrodynamic induction should be achievable. A first prototype for a contact- less power supply is built.
Auckland Uniservices, the commercial company of The University of Auckland, patents the technology. John Boys team develops novel technology enabling multiple vehicles to run on the same inductive power loop and provide independent control of each vehicle.
Auckland UniServices Patents the technology. Uses coupled resonant coils in a flat "pad" style to transfer tens of watts into a variety of consumer devices, including lamp, phone, PDA, iPod etc.
Near field energy itself is non radiative, but some radiative losses will occur. In addition there are usually resistive losses. Near field transfer is usually magnetic inductive , but electric capacitive energy transfer can also occur.
In a wireless energy transmission system using this principle, a high-power ultraviolet beam might be used to form vertical ionized channels in the air directly above the transmitter-receiver stations.
The same concept is used in virtual lightning rods, the electrolaser electroshock weapon and has been proposed for disabling vehicles. A global system for "the transmission of electrical energy without wires" dependant upon the high electrical conductivity of the earth was proposed by Nikola Tesla as early as Around this conducting earth is an atmosphere. The earth is a conductor; the atmosphere above is a conductor, only there is a little stratum between the conducting atmosphere and the conducting earth which is insulating.
Now, you realize right away that if you set up differences of potential at one point, say, you will create in the media corresponding fluctuations of potential. But, since the distance from the earth's surface to the conducting atmosphere is minute, as compared with the distance of the receiver at 4, miles, say, you can readily see that the energy cannot travel along this curve and get there, but will be immediately transformed into conduction currents, and these currents will travel like currents over a wire with a return.
The energy will be recovered in the circuit, not by a beam that passes along this curve and is reflected and absorbed,. The intention of the Tesla world wireless energy transmission system is to combine electrical power transmission along with broadcasting and point-to-point wireless telecommunications, and allow for the elimination of many existing high-tension power transmission lines, facilitating the interconnection of electrical generation plants on a global scale.
Regarding the recent notion of power transmission through the earth-ionosphere cavity, a consideration of the earth- ionosphere or concentric spherical shell waveguide propagation parameters as they are known today shows that wireless energy transfer by direct excitation of a Schumann cavity resonance mode is not realizable. This is the transmitter form as described in U. The primary and secondary circuits of a transformer are not directly connected. The transfer of energy takes place by electromagnetic coupling through a process known as mutual induction.
An added benefit is the capability to step the primary voltage either up or down. The Battery chargers of a mobile phone or the transformers on the street is examples of how this principle can be used.
Induction cookers and many electric toothbrushes are also powered by this technique. The main drawback to induction, however, is the short range. The receiver must be very close to the transmitter or induction unit in order to inductively couple with it. Related Books Free with a 30 day trial from Scribd.
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