Witricity was actually first observed in the 50’s but among its many
problems was the unsafe factor. Having electricity carried through
electro magnetic waves could be cause for nervousness or even cancer.
Another major objection would be the theft of electricity through the
wireless waves. If you thought theft of broadband internet through
wireless network cards was a problem you could easily surmise that theft
of electricity would be an even major concern. Considering the fact that
people pay a lot more per month on electricity you would assume there
would be people stealing it via witricity wireless devices. We will have
to wait and see what may happen. For right now we can only guess as to
what the risks might be.
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 electricity 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 within
medium range (few meters) from the transmitter. The system uses a
relatively low frequency (few MHz). In their first paper, the group also
simulated GHz dielectric resonators.
Unlike the far field wireless power transfer systems based on electric
field coupling, built by Nikola Tesla in the late 19th century,
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,[dubious — see
talk page] albeit 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. The researchers
attribute lack of previous development of this technology from
long-known physical laws to a lack of motivation; modern consumer have a
high number of portable electronic devices which currently require
batteries and plug-in chargers.
The MIT researchers successfully demonstrated the ability to power a 60
watt light bulb from a power source that was 2 meters (7 ft) away at
roughly 40% efficiency. They used two capacitively loaded copper coils,
60 centimeters (24 in) in diameter, oriented along the same axis, The
coils were designed to resonate together at 10 MHz. One was connected
inductively to a power source, the other to a bulb. The setup powered
the bulb on, even when the direct line of sight was blocked using a
wooden panel. Aristeidis Karalis says that "the usual non-resonant
magnetic induction would be almost 1 million times less efficient in
this particular system".
The researchers plan to miniaturize the setup enough for commercial use
in three to five years. The researchers suggest that the radiated power
densities can be brought below the threshold for FCC safety regulations.
Wireless Electricity is an up and coming new technology that has it’s
premise in making electricity power convenient to the everyday user. No
longer would you need electricity wires strung out all over the ground
or someone to come into your house and bore holes through your firewall
in the house walls. That can actually be quite hard if you have a well
built house.Instead of rewiring a house you could simply install a
copper coil inside the middle of each room ceiling. With a 9 foot
diameter reach you can have electricity signaled out through a safe
electroc magenetic field. This field can safely deliver and trasmit the
needed electricity to an air conditioner, TV, microwave, refridgerator,
cell phone, laptop and many other electronic devices.
'WiTricity' about to become the next new thing? It seems that a
Massachusetts Institute of Technology team was able to light up a
60-watt bulb that had 'no physical connection' with the power-generating
appliance. MIT physics professor Marin Soljacic believes his system
needs to become twice as efficient to be on par with charging the
chemical batteries in portable gadgets.
Massachusetts Institute of Technology researchers made a 60-watt light
bulb glow by sending it energy wirelessly -- from a device 7 feet away
-- potentially heralding a future in which cell phones and other gadgets
get juice without having to be plugged in. The breakthrough, disclosed
Thursday in Science Express, the online publication of the journal
Science, is being called "WiTricity" by the scientists.
The concept of sending power wirelessly isn't new, but its wide-scale
use has been dismissed as inefficient because electromagnetic energy
generated by the charging device would radiate in all directions.
One advance was announced last fall, when MIT physics professor Marin
Soljacic said he had figured out how to use specially tuned waves. The
key is to get the recharging device and the gadget that needs power to
resonate at the same frequency - allowing them to more efficiently
It's similar to how an opera star can break a wine glass that happens to
resonate at the same frequency as her voice.
Bye Bye Batteries
The next step was to demonstrate the principle in experiments, which is
what was described in the new paper in Science. The MIT team was able to
light up a 60-watt bulb that had "no physical connection" with the
"It was quite exciting," Soljacic said. The process is "very
reproducible," he added. "We can just go to the lab and do it whenever
The development raises the prospect that we might eliminate some of the
clutter of cables in our ever-more electronic world. And if devices can
get their power through the air, they might not need batteries and their
attendant toxic chemicals.
On Second Thought
However, the technology has a ways to go before it becomes practical.
The MIT system is about 40 to 45 percent efficient -- meaning that most
of the energy from the charging device doesn't make it to the light
bulb. Soljacic believes his system needs to get twice as efficient to be
on par with charging the chemical batteries in portable gadgets.
Also, the copper coils that transmit the power are about 2 feet wide for
now -- too big to be feasible for, say, laptops. And the 7-foot range of
this wireless Relevant Products/Services handoff could be increased --
presumably so that one charging device could automatically power all the
gadgets in a room.
Soljacic believes all those improvements are within reach. The next step
is to fire up more than just light bulbs, perhaps a Roomba robotic
vacuum or a laptop.
Soljacic's team stresses that the "magnetic coupling" process involved
in WiTricity is safe on humans and other living things. And in the
initial experiments on the light bulb, no harm came to the cell phones,
electronic equipment and credit cards in the room - though more research
on that is needed.
A company by the name of Versive LLC - The Makers of Vroom® had first
coined the term Witricity back in 2005 when they invented a
different type of technology not at all related to MIT’s invention. The
company seems to be welcoming of MIT using the coined term but they
would still like credit for originally coining the name. Sounds pretty
fair to me. I’m glad they are not trying to sue and so on. Because of
their generous spirit I think people should go to their website and give
them a little business for their generosity.
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.
WiTricity Potential and Risks
I personally see this having some serious potential and estimate that
Wal*Mart, Lowes and Home Depot will soon have WiTricity appliances in
the very near future as this would be so easy to apply in many different
applications for home and business. A question that pops into my head
is, will this possibly cause Luekemia or some kind of cancer. That fear
is always raised about those living near large power transformers and
lines. The fear has never been scientifically justified as being true
but if this wireless power were in every room in every house in the
United States it would be a matter of time before we would possibly know
because the numbers of Leukemia patients would probably drastically go
up if it were a legitimate fear.
A clean-cut vision of a
future freed from the rat's nest of cables needed to power today's
electronic gadgets has come one step closer to reality.
US researchers have successfully tested an experimental system to
deliver power to devices without the need for wires.
The setup, reported in the journal Science, made a 60W light bulb glow
from a distance of 2m (7ft).
WiTricity, as it is called, exploits simple physics and could be adapted
to charge other devices such as laptops.
"There is nothing in this that would have prevented them inventing this
10 or even 20 years ago," commented Professor Sir John Pendry of
Imperial College London who has seen the experiments.
"But I think there is an issue of time. In the last few years we have
seen an exponential growth of mobile devices that need power. The power
cable is the last wire to be cut in a wireless connection."
Professor Moti Segev of the Israel Institute of Technology described the
work as "truly pioneering".
The researchers from the Massachusetts Institute of Technology (MIT) who
carried out the work outlined a similar theoretical setup in 2006, but
this is the first time that it has been shown to work.
How wireless energy could work
"We had a strong faith in our theory but experiments are the ultimate
test," said team member Assistant Professor Marin Soljacic.
"So we went ahead and sure enough we were successful, the experiments
behave very much like the theory."
Wireless energy transfer has been thought about for centuries
Wireless power promise
The experimental setup consisted of two 60cm (2ft) diameter copper
coils, a transmitter attached to a power source and a receiver placed 2m
(7ft) away and attached to a light bulb.
With the power switched on at the transmitter, the bulb would light up
despite there being no physical connection between the two.
Measurements showed that the setup could transfer energy with 40%
efficiency across the gap.
The bulb was even made to glow when obstructions such as wood, metal and
electronic devices were placed between the two coils.
"These results are encouraging. The numbers are not far from where you
would want for this to be useful," said Professor Soljacic.
The system exploits "resonance", a phenomenon that causes an object to
vibrate when energy of a certain frequency is applied.
When two objects have the same resonance they exchange energy strongly
without having an effect on other surrounding objects. There are many
examples of resonance.
"If you fill a room with hundreds of identical glasses and you fill each
one with a different level of wine each one will have a different
acoustic resonance," explained Professor Soljacic.
MIT Assistant Professor of Physics Marin Soljacic
This was a rudimentary system that proves energy transfer is possible.
Each glass would ring with a different tone if knocked with a spoon, for
"Then if I enter the room and start singing really loudly one of the
glasses may explode if I hit exactly the right tone."
Instead of using acoustic resonance, WiTricity exploits the resonance of
low frequency electromagnetic waves.
In the experiment both coils were made to resonate at 10Mhz, allowing
them to couple and for "tails" of energy to flow between them.
"With each cycle arriving, more pressure, or voltage in electrical
terms, builds up in this coil," explained Professor Pendry.
Over a number of cycles the voltage gathered until there was enough
pressure, or energy, at the surface to flow into the light bulb.
This accumulation of energy explains why a wine glass does not smash
immediately when a singer hits the right tone.
"The wine glass is gathering energy until it has enough power to break
that glass," said Professor Pendry.
Using low frequency electromagnetic waves, which are about 30m (100ft)
long, also has a safety advantage according to Professor Pendry.
"Ordinarily if you have a transmitter operating like a mobile phone at
2GHz - a much shorter wavelength - then it radiates a mixture of
magnetic and electric fields," he said.
Plugs and cables
Socket shortage solutions
This is a characteristic of what is known as the "far field", the field
seen more than one wavelength from the device. At a distance of less
than one wavelength the field is almost entirely magnetic.
"The body really responds strongly to electric fields, which is why you
can cook a chicken in a microwave," said Sir John.
"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."
As a result, the system should not present any significant health risk
to humans, said Professor Soljacic.
The team from MIT is not the first group to suggest wireless energy
Nineteenth-century physicist and engineer Nikola Tesla experimented with
long-range wireless energy transfer, but his most ambitious attempt -
the 29m high aerial known as Wardenclyffe Tower, in New York - failed
when he ran out of money.
Others have worked on highly directional mechanisms of energy transfer
such as lasers.
However, unlike the MIT work, these require an uninterrupted line of
sight, and are therefore not good for powering objects around the home.
Professor Soljacic and his team are now looking at refining their setup.
"This was a rudimentary system that proves energy transfer is possible.
You wouldn't use it to power your laptop.
"The goal now is to shrink the size of these things, go over larger
distances and improve the efficiencies," said Professor Soljacic.
The work was done in collaboration with his colleagues Andre Kurs,
Aristeidis Karalis, Robert Moffatt, John Joannopoulos and Peter Fisher.
MIT demonstrates wireless power transfer
Work could free cell phones, other portable electronics from power cords
CAMBRIDGE, Mass. -- Imagine a future in which wireless power transfer is
feasible: cell phones, household robots, mp3 players, laptop computers
and other portable electronics capable of charging themselves without
ever being plugged in, freeing us from that final, ubiquitous power
wire. Some of these devices might not even need their bulky batteries to
operate. A team from MIT’s Department of Physics, Department of
Electrical Engineering and Computer Science, and Institute for Soldier
Nanotechnologies (ISN) has experimentally demonstrated an important step
toward accomplishing this vision of the future. The team members are
Andre Kurs, Aristeidis Karalis, Robert Moffatt, Prof. Peter Fisher, and
Prof. John Joannopoulos (Francis Wright Davis Chair and director of ISN),
led by Prof. Marin Soljacic. Realizing their recent theoretical
prediction, they were able to light a 60W light bulb from a power source
seven feet (more than two meters) away; there was no physical connection
between the source and the appliance. The MIT team refers to its concept
as WiTricity (as in wireless electricity). The work will be
reported in the June 7 issue of Science Express, the advance online
publication of the journal Science.
The story starts one late night a few years ago, with Soljacic
(pronounced Soul-ya-cheech) standing in his pajamas, staring at his cell
phone on the kitchen counter. It was probably the sixth time that
month that I was awakened by my cell phone beeping to let me know that I
had forgotten to charge it. It occurred to me that it would be so great
if the thing took care of its own charging. To make this possible,
one would have to have a way to transmit power wirelessly, so Soljacic
started thinking about which physical phenomena could help make this
wish a reality.
Various methods of transmitting power wirelessly have been known for
centuries. Perhaps the best known example is electromagnetic radiation,
such as radio waves. While such radiation is excellent for wireless
transmission of information, it is not feasible to use it for power
transmission. Since radiation spreads in all directions, a vast majority
of power would end up being wasted into free space. One can envision
using directed electromagnetic radiation, such as lasers, but this is
not very practical and can even be dangerous. It requires an
uninterrupted line of sight between the source and the device, as well
as a sophisticated tracking mechanism when the device is mobile.
In contrast, WiTricity is based on using coupled resonant objects. Two
resonant objects of the same resonant frequency tend to exchange energy
efficiently, while interacting weakly with extraneous off-resonant
objects. A child on a swing is a good example of this. A swing is a type
of mechanical resonance, so only when the child pumps her legs at the
natural frequency of the swing is she able to impart substantial energy.
Another example involves acoustic resonances: Imagine a room with 100
identical wine glasses, each filled with wine up to a different level,
so they all have different resonant frequencies. If an opera singer
sings a sufficiently loud single note inside the room, a glass of the
corresponding frequency might accumulate sufficient energy to even
explode, while not influencing the other glasses. In any system of
coupled resonators there often exists a so-called strongly coupled
regime of operation. If one ensures to operate in that regime in a given
system, the energy transfer can be very efficient.
While these considerations are universal, applying to all kinds of
resonances (e.g., acoustic, mechanical, electromagnetic, etc.), the MIT
team focused on one particular type: magnetically coupled resonators.
The team explored a system of two electromagnetic resonators coupled
mostly through their magnetic fields; they were able to identify the
strongly coupled regime in this system, even when the distance between
them was several times larger than the sizes of the resonant objects.
This way, efficient power transfer was enabled. Magnetic coupling is
particularly suitable for everyday applications because most common
materials interact only very weakly with magnetic fields, so
interactions with extraneous environmental objects are suppressed even
further. The fact that magnetic fields interact so weakly with
biological organisms is also important for safety considerations,
Kurs, a graduate student in physics, points out.
The investigated design consists of two copper coils, each a
self-resonant system. One of the coils, attached to the power source, is
the sending unit. Instead of irradiating the environment with
electromagnetic waves, it fills the space around it with a non-radiative
magnetic field oscillating at MHz frequencies. The non-radiative field
mediates the power exchange with the other coil (the receiving unit),
which is specially designed to resonate with the field. The resonant
nature of the process ensures the strong interaction between the sending
unit and the receiving unit, while the interaction with the rest of the
environment is weak. Moffatt, an MIT undergraduate in physics, explains:
The crucial advantage of using the non-radiative field lies in the fact
that most of the power not picked up by the receiving coil remains bound
to the vicinity of the sending unit, instead of being radiated into the
environment and lost. With such a design, power transfer has a
limited range, and the range would be shorter for smaller-size
receivers. Still, for laptop-sized coils, power levels more than
sufficient to run a laptop can be transferred over room-sized distances
nearly omni-directionally and efficiently, irrespective of the geometry
of the surrounding space, even when environmental objects completely
obstruct the line-of-sight between the two coils. Fisher points out:
As long as the laptop is in a room equipped with a source of such
wireless power, it would charge automatically, without having to be
plugged in. In fact, it would not even need a battery to operate inside
of such a room. In the long run, this could reduce our society’s
dependence on batteries, which are currently heavy and expensive.
At first glance, such a power transfer is reminiscent of relatively
commonplace magnetic induction, such as is used in power transformers,
which contain coils that transmit power to each other over very short
distances. An electric current running in a sending coil induces another
current in a receiving coil. The two coils are very close, but they do
not touch. However, this behavior changes dramatically when the distance
between the coils is increased. As Karalis, a graduate student in
electrical engineering and computer science, points out, Here is
where the magic of the resonant coupling comes about. The usual
non-resonant magnetic induction would be almost 1 million times less
efficient in this particular system.
WiTricity is rooted in such well-known laws of physics that it makes one
wonder why no one thought of it before. In the past, there was no
great demand for such a system, so people did not have a strong
motivation to look into it, points out Joannopoulos, adding,
Over the past several years, portable electronic devices, such as
laptops, cell phones, iPods and even household robots have become
widespread, all of which require batteries that need to be recharged
As for what the future holds, Soljacic adds, Once, when my son was
about three years old, we visited his grandparents’ house. They had a
20-year-old phone and my son picked up the handset, asking, ‘Dad, why is
this phone attached with a cord to the wall"’ That is the mindset of a
child growing up in a wireless world. My best response was, ‘It is
strange and awkward, isn’t it" Hopefully, we will be getting rid of some
more wires, and also batteries, soon.’
This work was funded by the Army Research Office (Institute for Soldier
Nanotechnologies), National Science Foundation and the Department of
Electric plugs could become things of the past
after scientists devised a way of recharging laptops and mobile
telephones without the need for cables.
WiTricity: scientists find a way to send power through thin air
The team was able to light a 60W bulb from a power source 7ft away
For the first time electrical engineers have powered a light bulb from a
source seven feet away without a cable using mainly magnetic waves.
They believe the WiTricity technology could be developed to allow
portable electronic gadgets to be charged wirelessly.
It would also help the environment, dispensing with the long-term
problems caused by battery disposal.
Scientists have long known that transferring electric power does not
require wires, but for years have struggled to find a way to make it
A team from the Massachusetts Institute of Technology unveils its
WiTricity (wireless electricity) concept today in Science Express, an
online advance publication of the journal Science.
The method exploits an effect close to inductance which is at work in
transformers used to charge everyday appliances containing coils which
transmit energy to each other by electromagnetic induction.
Up to now transferring energy this way over distances of more than a few
inches has been inefficient.
Concerns have also been raised about a possible link between
electromagnetic waves and cancer. However, Prof Marin Soljacic, who led
the research, said yesterday he believed the technology can be developed
without posing any additional health risks.
Instead of irradiating the environment with electromagnetic waves, a
power transmitter could fill the space around the power waves with a
"non-radiative" electromagnetic field, he said.
Energy would only be picked up by gadgets designed to "resonate" with
The team was able to light a 60W light bulb from a power source seven
feet away; there was no physical connection between the source and the
appliance, each of which contained a copper coil.
The team believes an object the size of a laptop could be recharged
within a few metres of a wireless power source.