Bhakta, Realmuto, Shahid, Verbovsky 1

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 / Kamal / Robert / Hasan / Patrick
Percentage of contributions / 25% / 25% / 25% / 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. - 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. Dedicated Li-ion/polymer charging ICs can be used to automatically regulate the charging of batteries, such as the Microchip MCP73833/4 ( Premade circuit boards such as the one found at 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 . 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 dye-sensitized 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 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.

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.

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.

Figure 2: Objective Attributes Tree

References

1)National Instruments. (2012, 8 3).Teach tough concepts: Frequency domain in measurements. Retrieved from

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:

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: