wireless electricity
wireless electricity
wireless electricity
WiTricity is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. This differs from other methods like simple induction, microwaves, or air ionization. The system consists of transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency. Due to operating in the electromagnetic near field, the receiving devices must be no more than about a quarter wavelength from the transmitter
Unlike the far field wireless power transmission systems based on traveling electro-magnetic waves, WiTricity employs near field inductive coupling through magnetic fields similar to those found in transformers except that the primary coil and secondary winding are physically separated, and tuned to resonate to increase their magnetic coupling. These tuned magnetic fields generated by the primary coil can be arranged to interact vigorously with matched secondary windings in distant equipment but far more weakly with any surrounding objects or materials such as radio signals or biological tissue.
In particular, WiTricity is based on using 'strongly-coupled' resonances to achieve a high power-transmission efficiency. Aristeidis Karalis, referring to the team's experimental demonstration, says that "the usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system". Researchers attribute the delay to develop the technology to limitations of well-known physical laws and a simple lack of need. Only recently have modern consumers obtained a high number of portable electronic devices which currently require batteries and plug-in chargers
Introduction to Witricity:
Electricity is today a necessity of modern life. It is difficult to imagine passing a day without electricity. The conventional use of electricity is made possible through the use of wires. However researchers in MIT have devised a means of providing electricity without any wires.
WiTricity, a portmanteau for wireless electricity, is a term coined initially by Dave Gerding in 2005 and used by an MIT research team led by Prof. Marin Soljai in 2007. This principle of wireless electricity works on the principle of using coupled resonant objects for the transference of electricity. The system consists of WiTricity transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency. Wireless power transmission is not a new idea; Nikola Tesla demonstrated a "transmission of electrical energy without wires" that depends upon electrical conductivity as early as 1891.
The receiver works on the same principle as radio receivers where the device has to be in the range of the transmitter. It is with the help of resonant magnetic fields that witrecity produces electricity, while reducing the wastage of power. This is unlike the principle adopted by Nikola Tesla in the later part of the 19th century; where conduction based systems were used. The present project on witricity aims at power transmissions in the range of 100 watts. May be the products using WiTricity in future might be called Witric or Witric's.
So far the MIT researchers have been able to power a 60 watt light bulb from a power source that is located about seven feet away, while providing forty percent efficiency. This was made possible using two copper coils that were twenty inches in diameter which were designed so that they resonated together in the MHz range. One of these coils were connected to a power source while the other, to a bulb. With this witricity setup, the bulb got powered even when the coils were not in sight.
WiTricity Technology: The Basics
Understanding what WiTricity technology is transferring electric energy or power over distance without wires is quite simple. Understanding how it works is a bit more involved, but it doesn't require an engineering degree. We'll start with the basics of electricity and magnetism, and work our way up to the WiTricity technology.
Electricity: The flow of electrons (current) through a conductor (like a wire), or charges through the atmosphere (like lightning). A convenient way for energy to get from one place to another.
Magnetism: A fundamental force of nature, which causes certain types of materials to attract or repel each other. Permanent magnets, like the ones on your refrigerator and the earth's magnetic field, are examples of objects having constantmagnetic fields. Oscillating magnetic fields vary with time, and can be generated by alternating current (AC) flowing on a wire. The strength, direction, and extent of magnetic fields are often represented and visualized by drawings of the magnetic field lines.
As electric current, I, flows in a wire, it gives rise to a magnetic field, B, which wraps around the wire. When the current reverses direction, the magnetic field also reverses its direction.
The blue lines represent the magnetic field that is created when current flows through a coil. When the current reverses direction, the magnetic field also reverses its direction.
Electromagnetism: A term for the interdependence of time-varying electric and magnetic fields. For example, it turns out that an oscillating magnetic field produces an electric field and an oscillating electric field produces a magnetic field.
Magnetic Induction: A loop or coil of conductive material like copper, carrying an alternating current (AC), is a very efficient structure for generating or capturing a magnetic field. If a conductive loop is connected to an AC power source, it will generate an oscillating magnetic field in the vicinity of the loop. A second conducting loop, brought close enough to the first, may "capture" some portion of that oscillating magnetic field, which in turn, generates or induces an electric current in the second coil. The current generated in the second coil may be used to power devices. This type of electrical power transfer from one loop or coil to another is well known and referred to as magnetic induction. Some common examples of devices based on magnetic induction are electric transformers and electric generators.
Energy/Power Coupling: Energy coupling occurs when an energy source has a means of transferring energy to another object. One simple example is a locomotive pulling a train car the mechanical coupling between the two enables the locomotive to pull the train, and overcome the forces of friction and inertia that keep the train still and, the train moves. Magnetic coupling occurs when the magnetic field of one object
An electric transformer is a device that uses magnetic induction to transfer energy from its primary winding to its secondary winding, without the windings being connected to each other. It is used to "transform" AC current at one voltage to AC current at a different voltage.
interacts with a second object and induces an electric current in or on that object. In this way, electric energy can be transferred from a power source to a powered device. In contrast to the example of mechanical coupling given for the train, magnetic coupling does not require any physical contact between the object generating the energy and the object receiving or capturing that energy.
Resonance:
This video shows how a wine glass captures sound energy that ocillates at its natural resonant frequency, converts it to mechanical energy that causes the glass to deform at that same frequency and eventually causing it to shatter.
Resonance: Resonance is a property that exists in many different physical systems. It can be thought of as the natural frequency at which energy can most efficiently be added to an oscillating system. A playground swing is an example of an oscillating system involving potential energy and kinetic energy. The child swings back and forth at a rate that is determined by the length of the swing. The child can make the swing go higher if she properly coordinates her arm and leg action with the motion of the swing. The swing is oscillating at its resonant frequency and the simple movements of the child efficiently transfer energy to the system. The resonant frequency depends on the size, shape and thickness of the material.
Resonant Magnetic Coupling: Magnetic coupling occurs when two objects exchange energy through their varying or oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two objects are approximately the same.
Two idealized resonant magnetic coils, shown in yellow. The blue and red color bands illustrate their magnetic fields. The coupling of their respective magnetic fields is indicated by the connection of the colorbands.
WiTricity Technology: WiTricity power sources and capture devices are specially designed magnetic resonators that efficiently transfer power over large distances via the magnetic near-field. These proprietary source and device designs and the electronic systems that control them support efficient energy transfer over distances that are many times the size of the sources/devices themselves.
The WiTricity power source, left, is connected to AC power. The blue lines represent the magnetic near field induced by the power source. The yellow lines represent the flow of energy from the source to the WiTicity capture coil, which is shown powering a light bulb. Note that this diagram also shows how the magnetic field (blue lines) can wrap around a conductive obstacle between the power source and the capture device.
WORKING OF WITRICITY:
STEP 1:
A circuit [A] attached to the wall socket converts the standard 60-hertz current to 10 megahertz and feeds it to the transmitting coil [B]. The oscillating current inside the transmitting coil causes the coil to emit a 10-megahertz magnetic field.
STEP 2:
The receiving coil [C] has the exact same dimensions as the sending coil and thus resonates at the same frequency and, in a process called magnetic induction, picks up the energy of the first coil's magnetic field.
STEP 3:
The energy of the oscillating magnetic field induces an electrical current in the receiving coil, lighting the bulb [D].
WiTricity's technology is different than:
Magnetic Resonance Imaging(MRI):
MRI machines use "magnetic resonance imaging" to produce diagnostic images of soft tissue.Many people assume that WiTricity's "Resonant Magnetic Coupling" must be similar to magnetic resonance imaging (MRI) technology, however, the technologies are similar in name only. MRI is, as its name suggests, a technology for using magnetism as a basis for diagnostic imaging of soft tissue in the human body. It utilizes a strong DC magnet to orient the magnetic fields of atoms within tissues, and radio frequency fields to manipulate those atoms in a selective way, so that tissues and structures can be imaged clearly. The "resonance" referred to in "MRI" refers to the resonance of atomic structures. MRI is not considered to be a method for wireless power transfer.
Tesla's Vision of a Wireless World
In the late 1800's and early 1900's, at the dawn of the electrification of the modern world, some scientists and engineers believed that using wires to transfer electricity from every place it was generated to every place that it could be used would be too expensive to be practical. Nikola Tesla, one of the most well known of these scientists, had a vision for a wireless world in which wireless electric power and communications would reach around the world, delivering information and power to ships at sea, factories, and every home on the planet. Tesla contributed significantly to our understanding of electricity and electrical systems and is credited with inventing three-phase AC power systems, induction motors, fluorescent lamps, radio transmission, and various modes of wireless electric power transfer. WiTricity technology for power transfer is different than the technologies proposed by Tesla, but his work is referenced and acknowledged in the scientific articles published by WiTricity's founding technical team.
Nikola Tesla's Wardenclyffe tower built on Long Island, NY in 1904. This tower was intended to implement Tesla's vision of transmitting power and information around the world. The tower was destroyed in 1917.
Non-Radiative Energy Transfer is Safe for People and Animals:
WiTricity's technology is a non-radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organisms people and animals and are scientifically regarded to be safe. Professor Sir John Pendry of Imperial College London, a world renowned physicist, explains: "The body really responds strongly to electric fields, which is why you can cook a chicken in a microwave. But it doesn't respond to magnetic fields. As far as we know the body has almost zero response to magnetic fields in terms of the amount of power it absorbs." Evidence of the safety of magnetic fields is illustrated by the widespread acceptance and safety of household magnetic induction cooktops.Through proprietary design of the WiTricity source, electric fields are almost completely contained within the source. This design results in levels of electric and magnetic fields which fall well within regulatory guidelines. Thus WiTricitytechnology doesn't give rise to radio frequency emissions that interfere with other electronic devices, and is not a source of electric and magnetic field levels that pose a risk to people or animals.
Limits for human exposure to magnetic fields are set by regulatory bodies such as the FCC, ICNIRP, and are based on broad scientific and medical consensus. WiTricitytechnology is being developed to be fully compliant with applicable regulations regarding magnetic fields and electromagnetic radiation.
ADVANTAGES OF WITRICITY:
More Convenient:
No manual recharging or changing batteries.
Eliminate unsightly, unwieldy and costly power cords.
More Reliable:
Never run out of battery power.
Reduce product failure rates by fixing the weakest link': flexing wiring and mechanical interconnects.
There is no need of having a line of sight.
More Environmentally Friendly:
Reduce use of disposable batteries.
Use efficient electric grid power' directly instead of inefficient battery charging.
WiTricitytechnology can be used to provide:
Direct Wireless Powerwhen all the power a device needs is provided wirelessly, and no batteries are required. This mode is for a device that is always used within range of its WiTricity power source.
Automatic Wireless Chargingwhen a device with rechargeable batteries charges itself while still in use or at rest, without requiring a power cord or battery replacement. This mode is for a mobile device that may be used both in and out of range of its WiTricity power source.
WITRICITY IN FUTURE:
Just imagine the future, with witricity, where there will be no need of power cables and batteries. The city just has to be covered with witricity hot spots wherein you can use your electric gadget battery and wire free making it more convenient to carry around and much lighter. With witricity, there will be no need of charging batteries, or buying new batteries for your electrical gadgets.
APPLICATIONS:
Consumer Electronics:
Automatic wireless charging of mobile electronics (phones, laptops, game controllers, etc.) in home, car, office, Wi-Fi hotspots while devices are in use and mobile.
Direct wireless powering of stationary devices (flat screen TV's, digital picture frames, home theater accessories, wireless loud speakers, etc.) eliminating expensive custom wiring, unsightly cables and "wall-wart" power supplies.
Direct wireless powering of desktop PC peripherals: wireless mouse, keyboard, printer, speakers, display, etc eliminating disposable batteries and awkward cabling.
Industrial:
Direct wireless power and communication interconnections across rotating and moving "joints" (robots, packaging machinery, assembly machinery, machine tools) eliminating costly and failure-prone wiring.
Direct wireless power and communication interconnections at points of use in harsh environments (drilling, mining, underwater, etc.) where it is impractical or impossible to run wires.
Transportation:
Automatic wireless charging for future hybrid and all-electric passenger and commercial vehicles, at home, in parking garages, at fleet depots, and at remote kiosks.
Direct wireless power interconnections to replace costly vehicle wiring harnesses and slip rings.
Other Applications:
Direct wireless power interconnections and automatic wireless charging for implantable medical devices (ventricular assist devices, pacemaker, defibrilator, etc.).
Automatic wireless charging and for high tech military systems (battery powered mobile devices, covert sensors, unmanned mobile robots and aircraft, etc.).
Direct wireless powering and automatic wireless charging of smart cards.
Direct wireless powering and automatic wireless charging of consumer appliances, mobile robots, etc.
Conclusion:
WiTricity's technology is a non-radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organismspeople and animalsand are scientifically regarded to be safe. WiTricity products are being designed to comply with applicable safety standards and regulations. Hence witricity is technology safe.witricity can transfer power depends on the source and receivers. if it is relatively close to one another, and can exceed 95%.Efficiency is primarily determined by the distance between the power source and capture device, however, the shape may impact the efficiency. it can transfer the power through walls also. Traditional magnetic induction requires that the power source and capture device be very close to one another usually within millimeters to transfer power efficiently. WiTricitytechnology is based on sharply resonant strong coupling, and is able to transfer power efficiently even when the distances between the power source and capture device are several times the size of the devices themselves.
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