Design Vi – Homework 4
I pledge my honor that I have abided by Stevens Honor System
Team Members: Smik Naik, Kunjan Patel, David Formoso, William Haupt
Wireless Cell Phone/laptop Battery Charger
1: Summary of assignments of individual group members
The workload of this group assignment was shared responsibly among the members . All the
individuals performed their relative tasks and came up with the report for the assignment . High
level research was conducted In order to be as accurate as possible. It was understood that the
fundamental principles was the foundation of the project. 25% inputs from each of the
members resulted in the completion of this report
The work breakdown of team members was as follows:
David worked on researching the Wireless Energy Transfer technology. He researched this topic
and wrote the corresponding information regarding this technology.
Kunjan researched inductive coupling and helped the groups understanding of this technology .
He provided research and the information on this particular topic.
William looked into resonant induction and dug up some very useful references for this project .
Smit is the team leader and came up with the idea for this project . He studied the technology
behind microwave power transfer, and provided the corresponding references .
Each group member provided quality references about each of the technologies they were
assigned to research. After all the research was done the team members met up and explained
to one another the different technologies, and then proceeded to complete the “SWOT”
analysis. All the team members helped to contribute to this section of the report .
2: Fundamental principles
Introduction:
Technology has developed rapidly in the past century. But even with all the advancements,
there are some small areas which remained unaffected. Imagine how far we have reached in
the applications of cell‐phones. Sending texts, MMS, emails, etc. have made our job so much
easier. But there is one constraint in using cell‐phones. It needs to be charged to a threshold
level or connected to power. If we can eliminate this requirement, there would be no worries
about remembering where the charger or the USB cord is. Hence, transmission and reception
of voltage wirelessly and efficiently is still an obstacle in our lives.
Wireless Energy Transfer (WET)
This technology is credited to Tesla. The WET comprises of two units: Transmitter and Receiver.
Transmitter is a resonant antenna driven by grounded AC generator. Receiver is a grounded
resonant antenna directly powering the load. When WET is functioning, the electric currents in
transmitter and receiver are in phase and in same direction relative to ground. A magnifier is
made up of a resonant antenna. It produces both, oscillating electric field and magnetic field.
These fields are produced around the magnifier when transverse electromagnetic wave is
involved. Both the fields are perpendicular to each other. The ratio of oscillating electric field to
magnetic field, in the proximity of the magnifier, is higher than the free space impedance . The
only disadvantage of this process is that the received power reduces as the distance between
transmitter and receiver increases.
Inductive Coupling
Inductive coupling is used for short range wireless power transfer . Hence, it is used only when
the transmitter and receiver are in very close proximity of each other. Inductive Coupling is
defined as movement of energy between wires with the use of magnetic field. Because
magnetic fields decay very quickly, it is used only for short ranges . Principles of
Electromagnetism are utilized for generation of current. As electricity flows through a wire,
magnetic field is generated which is perpendicular to the wire. This magnetic field can be
enlarged by coiling the wire. Current is generated in the wire when it is in close range of the
magnetic field. Although Inductive Coupling is efficient, it is limited to short range. If cell
phones are kept near a device which undergoes Inductive Coupling, the battery of cell phones
can be charged.
Resonant Induction
This technique was the idea of MIT Engineers who named it ‘WiTricity’ . It was estimated that
electricity could be transmitted seven feet far with 40% efficiency. This method is more or less
similar to Inductive Coupling. The only difference is the use of resonance to increase the range
of transmission. Depending on shapes and materials, things resonates at a specific frequency.
Energy is shifted between two resonating coils. The main advantages of Resonant Induction are
that it is harmless, moderately efficient and medium range or energy transfer. Since humans
are not resonating objects, magnetic fields would not interfere with us. There is room for
improvement in the efficiency of transferring power. Imagine eight different cell phones kept in
a room. How awesome would it be when all of them get charged without any wires!
Microwave Power Transfer
Microwave Power Transfer is a type of power transfer via air using microwaves. This technique
can be used for long range energy movement. Power from space and satellite can be
transmitted, but it is still under experiment. First and foremost, DC current is converted into
microwaves. These microwaves are transferred through a large transmitter. In the open space,
these waves are grasped by a larger receiver. The microwaves are then converted into AC
current. There are two main advantage of this technique. It is very efficient and transfers
energy through long range. Conversion from DC – Microwaves – AC is 90% efficient and the
transmission is estimated to be 95% accurate. But this method has two huge flip sides. It is not
secured for biological masses in the sense that it creates health hazards. The second
disadvantage is the cost of transmitter and receiver. The receiver has to be 10 times larger than
transmitter. Solar Power Satellites (SPS) uses the functionality of Microwave Power Transfer .
This is a Green energy supporter since it utilizes the solar energy.
3: SWOT Analysis
Strength: This project is very marketable because of the convenience it provides the users.
Consumers would accept this product without doubt. Humans have usually created machines
to reduce their work load and increase their luxury. This is one of such products. In the real
world, it can be used in restaurants, transportation terminals, theme parks, etc. Different types
of cell phones have different chargers. This device would eliminate that problem. Since the
device provides an elegant solution to a problem that is increasingly being faced by many
people due to the increases in usage of portable devices with more powerful and thus power
hungry multi-media oriented processors on board, there is potentially a large market that can
be reached.
Weakness: There are some obstacles which will need to be rectified . Since engineers at MIT
have already attempted with moderate efficiency, our team will need to raise the stakes and
design a better charger. We will need to solve the problems of power loss during transfer of
voltages. Increasing the efficiency of wireless power transfer is the primary obstacle that is
faced by such a project. Interference with other devices will need to be taken care of. This sort
of wireless technology can create problems for other wireless devices (such as interfering with
the Wi-Fi signal of a computer, or the cellular signal of a cellular phone). Also, when to start
charging and stop charging will need to be defined, thus some sort of communication or
interface will have to be created between the delivering and receiving end of the product . The
production of cell phones will need to change in order to incorporate the usage if Wireless Cell
Phone Battery Charger, otherwise some sort of adapter must be used.
Opportunities: The size and cost of the product matters. It would be great if a compatible
and small wireless charger is designed to meet the needs of the end users . The product also
needs to be made so that it works without much effort from the end user. This product is
supposed to make people’s lives easier, and therefore it should work completely automatically.
Threats: the use of microwave is harmful for small children and can cause health problems.
Also, due to the efficiency problem of the product, if a high efficiency cannot be achieved, this
product may have a large power draw, and thus become unattractive to the customer.
4: References
‘Tesla Wireless Energy Transfer at CCC’ by Davor Jadrijevic, December 10,2009
http://electronics.howstuffworks.com/wireless‐power.htm
Wireless Energy Transmission, Max Seidman,
http://fc.bbns.org/cataldo_ctr_science_website/2007_2008/2008%20Symposiu
m%20Presentations/Wireless%20Energy%20Transfer.MS.ppt.pdf
http://web.mit.edu/newsoffice/2007/wireless‐0607.html
http://ecoupled.com/pdf/Wireless_Power_Overview.pdf
5: Recommended Reading
“Efficient Wireless Non‐Radiative Mid‐Range Energy Transfer”, by A. Karalis, J.
Joannopoulous and M. Soljacic
“Scalar Waves: Advanced Concepts for Wireless Energy Transfer”, by Dr.
Konstatin Meyl