Download Shahid_Solar_Charging_Cover_HW5

Bhakta, Realmuto, Shahid, Verbovsky 1
Kamal Bhakta, Robert Realmuto, Hasan Shahid, Patrick Verbovsky
Professor Hong Man
EE/CPE 322 A
Engineering Design VI
8 March 2013
Assignment 5
“I pledge my honor that I have abided by the Stevens Honor System.”
Section 1
This report contains information on topics related to the project gathered by the group as
well as an in-depth analysis of the project. This week, Robert was added to the group. For this
report, Kamal and Robert researched technical topics. Hasan identified design constraints and
professional and ethnical responsibilities of the project. Patrick itemized objective attributes and
organized an objective tree. A table showing the contributions of each member of the group is
shown below.
Group member
Percentage of
contributions
Kamal Robert
25%
25%
Hasan
25%
Patrick
25%
Section 2
This section contains the results of research on topics related to the project.
Solar Cells and Power Storage
Solar cells operate in circuits in very much the same way as traditional voltage sources
such as DC power supplies or batteries.
Figure 1 - Simple example of solar cell in a circuit. http://www.evilmadscientist.com/2008/simple-solar-circuits/ quick introduction to solar cell operation
However, current is only delivered when the solar cell is illuminated, and the cell has no inherent
ability to store charge. Additionally, solar cells do not provide a consistent voltage source, as the
voltage greatly fluctuates with the intensity of the light shining upon it.
This brings about a few issues for the solar cell phone case. It is impossible to simply
hook up a solar cell to the phones battery and expect it to charge correctly. Standard lithium-ion
batteries, such as those found in most cellular phones today, must be charged in a controlled
manner. Different charging methods, such as trickle charge, and fast charge, must be used in
different situations, such as different charge levels, in order to preserve the life of the battery.
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Dedicated Li-ion/polymer charging ICs can be used to automatically regulate the charging of
batteries, such as the Microchip MCP73833/4
(http://ww1.microchip.com/downloads/en/DeviceDoc/22005b.pdf). Premade circuit boards such
as the one found at https://www.adafruit.com/products/390 make interfacing with these chips
much easier. A solar panel (or a regulated DC source) is connected to the input terminals of the
chip, and it provides a stable regulated output for charging the batteries, as well as circuitry to
monitor charge levels and temperature.
Solar mobile phone charging is not a new concept. Many DIY and commercial solutions
are available, such as one at http://www.instructables.com/id/How-to-make-a-solar-iPodiPhonecharger-aka-Might/ . The issue is designing a compact solution to fit on the phone itself and
provide sufficient power.
Flexible Solar Panels
A new type of solar panel has been developed by several researchers for its practical use
in flexible applications. The Flexible silicon solar cells have been fabricated to attract the
growing market of the electronic industries. The flexible solar panel will be able to revolutionize
'green' energy by incorporating devices that have become a necessity. It is one of the best
candidates for application as the device quality and structure is becoming more important to
consumers for portable electronics like cell phones. The size and compatibility of the cover is an
essential quality to passively generate electricity without obstructing the use of the device. The
only downside to the flexible solar panel material is the degradation of efficiency in comparison
to flat solar panels. Research from Qingdao University of Science and Technology has shown
that the maximum solar conversion efficiency for the flexible glass substrates is 5.5%, whereas
the efficiency of modern solar cells has reached peak efficiencies of around 40%. Due to the
effects created by the reflection of the curvature of flexible materials the efficiency begins to
degrade as oppose to flat solar cells that are uniformly formed.
Dye-sensitized solar cells have been proven by research done at the Beijing National
Laboratory for Molecular Sciences for its next generation qualities. The qualities that make dyesensitized solar cells resilient are high efficiency, low-cost, environmentally friendly, and low
angle dependence of incident light. The conversion efficiencies of the next generation
amorphous silicon solar cells are showing promising potential for large scale integration. The
conversion efficiency of the flexible solar panels could be improved in the future in various ways
for instance by reducing the stress of the substrate, improving the form of the p-type and
intrinsic layers, and improving the thermal expansion of the flexible polymeric substrate during
the deposition processes. The light current intensity versus voltage of the flexible solar cell and
rigid solar cell show similar characteristic with a lower efficiency shown by the larger light
current intensity to voltage ratio. In essence the flexible solar panel will become one of the best
candidates in regards to device quality for large scale integration and will lower the production
cost for the flexible substrates.
Design Materials
Materials that will be incorporated as a device cover for the solar panel should be able to
protect the device as well as the solar cell. By taking the requirements of the cover into
consideration materials that will degrade the performance of the solar panel and will not be able
to protect the device cannot be selected. The cover should be composed of materials that will
allow a considerable amount of photon energy to pass through and onto the solar cells for
Bhakta, Realmuto, Shahid, Verbovsky 3
conversion. In regards to the rigidity of the cover's structure, material that is flexible, durable,
and will not compromise the requirements needed for the solar cell to function at its optimum
efficiency is the best option for the exposed area. Photons can pass through transparent material,
diffract off translucent material, and get absorbed by opaque material. With these characteristics
in mind some of the more fashionable materials that are incorporated with or around device
covers cannot be incorporated into the design. Likewise, materials which are transparent but do
not hold the durability of protective covers like glass are not a viable option. The overall
composition of the materials structure based on the energy levels of the atoms it is made up of
will determine its characteristic. Although materials like glass seem completely transparent for
photons to pass through, a range certain wavelengths will be absorbed such as ultraviolet. A
deeper understanding and better research into a variation of polymer plastics can be collected to
make an improve judgment of the design materials that will be used to make the cover for the
device and solar panel.
Section 3
This section contains a list of constraints and responsibilities of the project.
The constraints of the solar charging cover include the following:
- Low light environments: The solar cell will not absorb energy in low light environments such
as night time, days that are overcast, and when the phone is stored in the user’s pocket or
bag.
- Efficiency: The efficiency of solar panels is about 35% under direct sunlight which is
extremely low.
- Surface area: The amount of energy a solar panel absorbs is proportional to the surface. The
solar panel on the solar charging cover must be large enough to absorb a sufficient amount of
energy but small enough to avoid bulkiness.
- Cost: Solar cells are traditionally very expensive to manufacture.
- Manufacturability: While the new peel-and-stick method is an easy way to produce a flexible
solar cell, solar cells have not been mass produced using this process.
- Position of the solar cell: The solar cell will not absorb energy if it is pointed downwards. If
a solar cell is to be placed on the front of the solar charging cover, it must be transparent.
- Color: If the solar cell is to be dyed, only dark colors will absorb sufficient energy. A
brightly colored solar cell will be extremely inefficient.
The main responsibility of the project is to ensure that the solar charging cover is
manufactured and packaged through an environmentally-friendly process. Solar cells themselves
are a sustainability form of energy and the peel-and-stick process has not yet been shown to have
negative environmental effects. However, the case itself will most likely be made of plastic.
Therefore the case must be made in an environmentally-safe process. Other responsibilities
include marketing the product in an effective and tasteful manner and distributing and pricing the
product fairly.
Bhakta, Realmuto, Shahid, Verbovsky 4
Section 4
This section contains a list of objective attributes of the project.
I) High and Efficient Recharging Rate: The solar charging cover needs to recharge the
electrical device’s battery at a higher or equal rate than the power being consumed.
A) High Power Absorption from Solar Cells: The solar cells need to be able to absorb light
at high efficiency.
1) Consistent Efficiency Regardless of Environment: The solar panel cover should have
a consistent power absorption rate despite the effect from the environment. In other
words, the environment should have minimal effect on the solar panel cover.
2) Solar Cells on Both Back and Front: The more solar cells used implies more energy
absorbed from light. In addition, the user of the electrical device will have the back
side away from the sun when they use it so there is a need to have solar cells in the
front as well.
B) Efficient Transfer of Energy between Batteries: The second battery needs to recharge the
electrical device’s battery by transferring the stored energy with minimum loss of power
through the wires.
C) Efficient Temporary Battery: The second battery needs to be a good temporary storage
device.
1) High Recharging Rate: The second battery can be fully recharged at a fast rate.
2) Stores 5 Volts: The second battery can store about 5 volts.
II) Promotes Sales: The solar charging cover needs to be easily producible and appeal customers
to buy it.
A) Appealing Cover Appearance: The solar charging cover needs to look attractive and
appeal to customers.
1) Mask Solar Panels: Solar panels have an unattractive look to them. Therefore, the
solar panels on the cover needs to been hidden from the users view.
a) Dye Solar Cells in Different Colors: The solar panel cover can come in different
colors by dying the solar cells.
2) Avoid Bulkiness: The solar panel cover should be thin and weightless
B) Permits Market Flexibility: The solar panel cover price can be varied flexibly.
1) Inexpensive to Produce: The solar panel cover needs to be produced at low cost.
2) Quick to Manufacture: The solar panel covers need to be produced and a fast rate.
III) App to Interface with Solar Panel Cover: The app will inform the user the amount of charge
that the second battery is receiving and amount of charge it has. Also it will provide
efficiency improvement hints.
A) Provides Accurate Information: The app will inform the user the amount of charge that
the second battery is receiving and amount of charge it has. Also it will provide
efficiency improvement hints.
1) Accurate Reading of Second Battery Charge: The app needs to accurately read how
much charge is on the second battery.
2) Accurate Reading of Power Absorbed by Solar Panel: The app needs to accurately
read how much power the solar panel is receiving. The reading may contain noise that
needs to be filtered out (Reference 1).
B) Easy to Use App: The app needs to be simple to use and display the information neatly.
Bhakta, Realmuto, Shahid, Verbovsky 5
1) Display Important Information on One Page: The app needs to be able to display all
import information, like solar panel efficiency and second battery charge, on one
page. This would be much simpler than having to display different information on
different pages.
2) Use Popups for Unimportant Information: The app needs to allow the user to read
other information, like hints to help improve efficiency, by clicking on a button which
will display a popup for the respected information needed.
3) Easy to Read: The app needs to display the information in big text and in a neat
format.
C) Looks Appealing: The app UI needs to look appealing and not boring. For example, the
UI will have color instead of black text on a white screen.
Bhakta, Realmuto, Shahid, Verbovsky 6
Figure 2: Objective Attributes Tree
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References
1) National Instruments. (2012, 8 3). Teach tough concepts: Frequency domain in
measurements. Retrieved from http://www.ni.com/white-paper/13042/en
2) Yingge Li; Dongxing Du, "Characterization of Low Temperature Deposited Flexible
Amorphous Silicon Solar Cells," Energy and Environment Technology, 2009. ICEET '09.
International Conference on , vol.1, no., pp.548,551, 16-18 Oct. 2009
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5364315&isnumber=53625
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3) Liping Heng, "P-N junction based flexible dye sensitized solar cells," Nanotechnology
(IEEE-NANO), 2010 10th IEEE Conference on , vol., no., pp.1160,1162, 17-20 Aug. 2010
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5697879&isnumber=56977
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