12-09-2014, 04:50 PM
A Survey on wireless power transmission methods
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Abstract
Wireless power transmission is an old idea, as old as use of electricity. Early experiments
performed by Nikola Tesla still capture the imagination of young engineers even nowadays
when we witness the proliferation of transmission methods previously deemed unfeasible, now
being made commercially viable by advances in electronic devices manufacturing. This survey
lists a number of implementations in both consumer devices and non-consumer applications,
some old, well known methods as well as latest yet to be implemented technology.
Introduction
The wireless transmission of energy is common in much of the world. Radio waves
are energy, and people use them to send and receive cell phone, TV, radio and WiFi signals
every day. The exponential increase in scientific and technological achievements in the last ten
years has lead to general need for more efficient power transmission systems. The abundance
and widespread of wireless technologies is the cornerstone of the motivation for pursuing a
similar approach when power transfer is concerned. In light of recent advances in technology,
it is a belief of the authors of this paper that wireless energy transmission has a firm foothold
in today’s technology centered reality. Furthermore, we believe that man has passed the
adolescence in this pursuit and that technology has matured enough to allow us a new means
to power our ever-mobile devices and gadgets.
Nikola Tesla proposed theories of wireless power transmission in the late 1800s and
early 1900s. One of his more spectacular displays involved remotely powering lights in the
ground at his Colorado Springs experiment station.Tesla's work was impressive, but it didn't
immediately lead to widespread, practical methods for wireless power transmission. Since
then, researchers have developed several techniques for moving electricity over long distances
without wires. Some exist only as theories or prototypes, but others are already in use.
Laser/infrared optics transmission
Power transfer can also be achieved by converting energy into a laser beam and then pointing
it at a solar cell. There are several advantages in using this method over other wireless
power transmission technology, such as transfer over large areas, small (compact) sizes of
components used, no interference, control of access. There are drawbacks as well. Namely,
conversion (from electricity to light and back) is inefficient, atmosphere absorption causes
losses, and it requires a direct line of sight with the target (microwave transmission suffers from
the same drawback).
One example of the use of this technology is supplying an unmanned aircrafts using and
invisible, ground based laser, as demonstrated by the researchers at NASA's Marshall Space
Flight Center, Huntsville, Ala.
Trends
Consumer devices that implement some kind of wireless energy transfer are reaping the
benefits of arriving relatively late to the market and having relatively well defined and reasonable
criteria for comparison between them. Ease of use and efficiency are correctly identified
as major advantages and efforts are concentrated in those areas. Methods used appear to
have their own target applications and don’t compete with each on many fronts. Chargers for
mobile devices are the most sought after market at the moment but the approach of absolute
competition would create a situation similar to our old problems of standards and interoperability
which plague the industry since the first electrical outlet. A trend of standardisation such as one
promoted by Wireless Power Consortium is most welcome but their efforts might be upstaged
by emerging technologies which offer greater distance for transfer and more freedom in relative
positioning of devices which is one of the problems with EM induction that the consortium
currently stands behind.
Non-consumer applications are wildly more interesting and in some cases, unsettling. As
is the nature of military and industrial technology, real progress is always hidden from the public
and it is of strategic importance not to reveal the direction your research and development
is taking or at least how far along it is. Such is the nature of this field that no apparent trend
can be observed with any certainty but it is safe to assume that it will be here that biggest
breakthroughs will happen far away from the public eye, probably in applications most
interesting for military use. We shall not speculate about the nature of possible advancements
as it is well outside the scope of this paper
Optimal solutions for the future
We believe its too early to proclaim any single solution optimal or even make a
conjecture about the nature of such solutions. Applications in consumers devices are numerous
and heterogeneous but they all seek to replace just one object - the power cable, and while a
piece of wire is, or was, the best tool for the job, wireless methods of transfer and their inherent
shortcomings make us think about electrical devices and appliances from a functional point of
view.
Advances in battery technology and intelligent chargers might be the actual solution to
the problem we are trying to solve by eliminating wires, plugs and sockets with mobile device
chargers in an effort to charge our devices continuously and everywhere, having a battery that
charges within moments of being plugged-in makes that a non-issue.
On the opposite side there is now a possibility of battery-free devices that are
continuously powered not charged by wireless transfer within their defined zone of operation,
while that might sound restricting, some applications would benefit from that kind of limitation
and most applications would not suffer from them.
Eventually there even might be a persistent, continual, public power supply available in various
forms of transmission across wide areas and we might come to stop thinking in terms of
batteries and electrical grids
Conclusion
The copious amount of applications for wireless power transmission delivers no small
amount of motivation to this pursuit and certainly promises a beginning of an exciting new future
in the energy industry and will have massive impacts throughout our everyday lives. However
the technology is still young and it will be interesting to monitor its development through the
course of the next ten years.
It’s easy to see where wireless power transfer will better our lives, eliminating excess
cables and wires, removing unnecessary clutter and the need for cleaning, allowing us
even greater mobility with our devices and also allowing us to inhabit, in today’s standards,
uninhabitable areas. Furthermore it allows us to build cleaner, and certainly cheaper and
environmentally friendly solutions of sustainable energy. And it will bring us one step close in
solving the worlds energy crisis.
In this paper we tried to show the potential uses and some commercially available
solutions of wireless power transmission, different approaches and most popular methods of
delivering power, the drawbacks of current technologies and also tried to delve into new trends
and future uses.