Witricity - Online Article

Introduction

Don't you hate it when you forget to put your mobile phone on charge? Well, take heart - a new technology called WiTricity could mean never having to plug it in again. Welcome to the world of 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 a MIT research team led by prof. Marin Soljačić in 2007, to describe the ability to provide electrical energy to remote objects without wires. WiTricity is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. The system consists of WiTricity transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency. As WiTricity operates in the electromagnetic near-field, the receiving devices must be no more than about a quarter wavelength from the transmitter, that is a few meters at the frequency of a few MHz used by the system. In the study of diffraction and antenna design the electromagnetic field (or EM field) is, where the radiation pattern and/or the energy level depends on the distance from the antenna. The near field is that part of the radiated field nearest to the antenna. Beyond the near field is the infinite far field. In their first paper, the group also simulated GHz dielectric resonators.

Wireless power transmission is not a new idea, but to do so in an efficient way typically requires a directed beam like a laser or microwave. William C. Brown demonstrated in 1964 on the CBS Walter Cronkite news a microwave-powered model helicopter that received all the power needed for flight from a microwave beam (which requires the beam to be aimed at the aircraft as it flies). Between 1969 and 1975 Bill Brown was technical director of a JPL Raytheon program that beamed 30 kW over a distance of 1 mile between stationary points at 84% efficiency. Methods that don't require directed beams are typically very inefficient, as the energy is radiated in all directions (like a radio antenna) and only a small amount reaches the desired destination.

Unlike the far field wireless power transfer systems based on traveling EM waves, WiTricity employs near field inductive coupling through magnetic fields, which interact far more weakly with surrounding objects, including biological tissue. The WiTricity concept is fundamentally identical to the near field magnetically coupled Tesla coil resonators , WiTricity uses considerably lower and safer power levels and thus may be able to meet FCC and EMC regulations. Near-field technologies draw power from the transmitter when a receiver is nearby, but with far-field techniques, the source is always transmitting power in all directions, even if there is no receiver. It is not known exactly why this technology had not been developed. Researchers attribute it to various reasons ranging from the limitations of well-known physical laws, to simply a lack of need. Only recently have modern consumers obtained a high number of portable electronic devices which currently require batteries and plug-in chargers.

WiTricity: MIT tests breakthrough theory on wireless electricity

Using magnetically coupled resonators, a team of MIT students and professors have successfully tested their newly developed system for wireless electricity. The concept has been around for a while and even practiced using different transfer methods such as radio waves and lasers. The problem, however with radio waves is that there is no control of dispersion, which emits wasted energy into the atmosphere, and the problem with lasers is that there needs to be an uninterrupted line of sight (not to mention that lasers can be dangerous).

The team from MIT, led by professor Marin Soljacic, was able to power a 60W bulb without any physical connection between the bulb and the power source. This works by having two electromagnetic resonators, in the form of copper coils that share the same frequency. The resonators are placed within a relative proximity of each other, and the source resonator, also called the sending unit, can then transmit energy to the detached resonator across their shared frequency and not interfere with objects of differing frequencies.

Besides the wasteful nature of dispensing energy in a non-controlled direction (i.e. radio waves), there is also concern for safety. One property of WiTricity is that released energy remains within a magnetic field surrounding the source resonator until it is picked up by an object sharing the same frequency.

This technology is being toted as the answer to recharging portable devices, which makes perfect sense, but there is even greater potential with recent advances in wireless USB, or even remote controls. Imagine never having to change the batteries in your TV remote, and therefore never having to reprogram it.

As this technology will inevitably take off, it becomes the role of the designer to think of where these properties can appropriately be used, and to ensure that non-powered components within a facility don't share the same resonant frequencies; everything has a resonant frequency. The only foreseeable downside to this breakthrough is if your cat fluffy shares the same resonant frequency as your cell phone's power coil, but only then do I see a problem.

Inventors of Witricity

The inventors of witricity are the researchers from the team from Massachusetts Institute of Technology. They are the people who had coined the phrase of witricity and this invention can change the way electricity is used today. With witricity, the tangle of cables, plugs and charters that normally clutter homes can be rid of.

This team from MIT belonged to the Department of Physics, Department of Electrical Engineering and Computer Science and the Institute for Soldier Nanotechnologies. The members of this team were Andre Kurs, Aristeidis Karalis, Prof. Peter Fisher, Robert Moffatt and Prof. John Joannopoulos. The leader of this team of researchers was Prof. MarinSoljacic.

It was Prof. Marin Soljacic who provided the inspiration for the experiment and invention of witricity. It was while standing in the kitchen one night, that on staring at his mobile phone that he had thought it would be nice if his mobile phone would take care of its own charging instead of him having it periodically recharge.

He then tried out his experiment using two coils of copper, where one was connected to a receiver, and the other to a transmitter. With the help of these two coils of copper, the inventors of witricity managed to transmit power across seven feet through the air to instantly light up a light bulb>

Though witricity worked only distances up till 9 feet at its inception, the inventors believed that it was possible to charge a battery that was located at a distance of a few yards from the power source that was connected to the receiving coil. They state that it would be sufficient to place a source in each room to provide power to the whole house.

First Experiment of Witricity

The first experiment of witricity, the concept of wireless electricity, was conducted in the year 2006, by researchers from Massachusetts Institute of Technology. The Assistant Professor of this team of researchers was Marin Soljacic.

This experiment was done using two copper coils of diameter two feet, a transmitter that was attached to a power source and a receiver that was placed about seven feet from the transmitter. This receiver was attached to a light bulb and once power was switched on at the transmitter, the bulb lit up despite there being no physical connection between the transmitter and receiver.

Data collected through measurements showed that there was transference of 40% of electricity through witricity. The interesting part of the electricity was that the bulb glowed despite the fact that wood, metal and other devices were placed in between the two coils.

This concept of witricity was made possible using resonance where an object vibrates with the application of a certain frequency of energy. So two objects having similar resonance tend to exchange energy without causing any effects on the surrounding objects . Just like in acoustic resonance, where there is a chance of a glass breaking if you strike the right tone, witricity is made possible with the resonance of low frequency electromagnetic waves.

In this experiment, the coils were resonated at 10 MHz where the cols coupled and energy made to flow between them. With each cycle, more pressure and voltage built up in the coil till the accumulation of voltage provided enough pressure and energy to flow to the light bulb. These low frequency electromagnetic waves are rather safe as though the body responds strongly to electric fields; it has almost zero response to absorbing power from a magnetic field.

About Marin Soljacic

Marin Soljacic was the leader of the team of researches from MIT who had found out a means of transmitting electricity to electrical gadgets without using any wires. He was basically an Assistant Professor of Physics since September 2005 who has a BsE degree in physics and electrical engineering from MIT in the year 1996. After this, he had earned his PhD in physics from the Princeton University in the year 2000.

It was in September 2000 that he was named an MIT Pappalardo Fellow in Physics and in the year 2003, he was appointed the Principal Research Scientist in the for the Research Laboratory of Electronics at MIT in the year 2003. He was also awarded the Adolph Lomb medal from the Optical Society of America in the year 2005.

It was basically his interests in exploring new and exciting concepts in physical phenomena that led him to experiment with the concept of wireless electricity. With this, he said that witricity would eventually replace power cables in the same way mobile and cordless phones have replaced landlines today.

Professor Soljacic basically turned to the concept of resonance to create witricity where there is efficient transmission of energy between the two objects that tend to resonate at the same frequency. The typical witricity system has two copper coils where one sends power and the other receives it. This concept worked efficiently and automatically where there is no necessity of having a clear line of sight in between the transmitter and electronic appliance. All that is needed for witricity is a source of wireless power which charges automatically without needing any plugging in.

How would be the future with Witricity

Modern science has now made it possible to use electricity without having to plug in any wires. This concept is called witricty which seems to have a bright future in providing wireless electricity.

Researchers developed witricity using resonance where energy is transmitted between two copper coils that resonate at the same frequency. Of these two coils, one is the power transmitter and the other, the receiver. The advantage of witricity is that there is no need of having a line of sight. As long as the object to be powered has a source of wireless power, in its vicinity, the appliances charges automatically without having to be plugged in.

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.

Just as beneficial witricity may be, there are some contraindications to the concept, with debates if it is risky living next to power lines and having a low power witricity network running in the home. They wonder what happens if a glass of water is spilt in a witricity room. However despite these contraindications, witricity has a bright future with the many advantages it provides in terms of weight, convenience and portability of electrical appliances.

How WiTricity works

This invention consists of a copper coil placed on the ceiling or in the ceiling that produces a weak electro magnetic field. Only devices created to react with this field will soak up the energy. By placing a coil in each room in a house you could potentially power the whole house using this wireless or WiTricity device.

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Witricity Power Applications

Researchers from the Massachusetts Institute of Technology have devised a means of transferring electricity without using any wires. They have dubbed this technology as witricity and has declared that there are many potential applications for it. Some of these potential applications include the powering of cell phones, household robots, laptops and other devices that normally run with the help of batteries or with plugging in of wires.

As witricity is in the developmental stage, lots of work is still to be done in improving it as the device used for their research disclosed that witricity power applications operate at only 40% efficiency. The potential applications of witricity are expected to materialize in the new future, of say a few years' time, after the necessary modifications are made to them.

These witricity applications are expected to work on the gadgets that are in close proximity to a source of wireless power wherein the gadget charges automatically without necessarily having to get plugged in. There are no limitations in witricity power applications where anything and everything that used to run with batteries or electrical connections can be used using WiTricity.

Just imagine, the future witricity power applications permit you to use wireless energy, without having to replace or recharge batteries. There will be no need of getting rid of these batteries either or of remembering to recharge batteries periodically. In addition to this, with witricity, there is no need of plugging in any wires and plugs and thus face a mess of wires.

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Comments

KUSHAL AB on 2010-02-10 22:31:18 wrote,

good work man.well done