HSU solar suitcase

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Engr305 Appropriate Technology page in progress
This page is a project in progress by students in Engr305 Appropriate Technology. Please do not make edits unless you are a member of the team working on this page, but feel free to make comments on the discussion page. Check back for the finished version on May 15, 2018.

WeShareSolar Solar Suitcase

Background[edit]

Many schools, health centers, and other medical or humanitarian operations need better lighting, batteries, and device chargers that are portable and reliable. Since 2011, the nonprofit We Care Solar has worked with NGOs and development organizations around the world to help install Solar Suitcases in places where they are most needed.

The Solar Suitcase is a portable power unit with multiple functions. Standard kits are equipped with either two plastic-backed 20-watt solar panels or one 50-200 watt aluminum glass solar panel. They come with a 12 volt LFP battery, two LED lights, two rechargeable headlamps, USB slots, a AA/AAA battery charger and roof/wall mounting kits.

Problem statement[edit]

The objective for this project is for our team to construct a portable photovoltaic system or 'Solar Suitcase' and design a lab for our engineering class where we will teach about Photovoltaics and how to construct our portable Pv-cell suitcase. We also seek to revamp the design to potentially find ways to make it more intuitive or helpful to the users. We will be constructing the Solar Suitcase using materials provided to us by the HSU Engineering department and the Schatz Energy Research Lab.

Project Evaluation Criteria[edit]

The following criteria will be used to assess the success of this project. These criteria were chosen by our team to aid our goal of teaching the rest of the class about the Solar Suitcase. The scale (1-10) represents the importance level of meeting the constraint of each listed criteria.

Criteria Constraints Weight
(1-10)
Assembly Students must be able to assemble and test the Solar Suitcase during the allotted lab time.
10
Concepts Students must achieve an understanding of the function of each component and how the components fit into the entire system.
8
Purpose Students must be aware of the overarching purpose of the Solar Suitcase Projects.
7
Functionality Each Solar Suitcase must be completed and operational.
9

Literature Review[edit]

This is a review of the available literature pertinent to the HSU Solar Suitcase Project.

Photovoltaic (PV) systems[edit]

Systems that capture energy from the sun and convert it into electricity.

Radiant Solar Energy[edit]

The sun is constantly emitting electromagnetic energy that earth is bombarded with. The amount of sunlight reaching any given area on earth is called insolation (watts/meter sq.). Insolation is a function the distance from the sun to earth (on average 93,000,000 miles), the time of year (how the earth is tilting on the axis), time of day, climate, and shading. The climate and atmosphere at any given moment highly affects the amount of solar insolation, as dust particles or humidity affects solar radiation reaching the surface. Insolation data for various world regions are available c from both governments and other organizations. The amount of energy that actually reaches your load is highly dependent on the solar insolation.[1]

Components[edit]

Solar panels- Flat devices placed in the sunlight to harvest solar energy. Made up of photovoltaic (PV) cells and able to convert sunlight into usable direct current (DC) electricity. Electricity output is dependent on the angle at which the solar panel is placed in relation to the sun. For example, a panel placed at a 90 degree angle to the sun is getting the most direct sunlight.[2] Panel output is dependent on both the current and voltage output of the panel itself. Imagining electricity as liquid in a tube, current is the amount of electricity in the tube, while voltage is the amount of push the electricity would have through the tube.[1] If plotted on a graph, the maximum voltage and current would meet at a Maximum power point, or MPP. The MPP is slightly under the voltage at open current (meaning only voltage and no current flow, VOC). Current without voltage is a short circuit, or ISC. This maximum power point is only theoretical, and energy flowing from a solar panel is highly affected by how much light it receives, and the temperature of the cell. Higher temperatures reduce efficiency of solar panels.[3]

Inverter/Transverter - While solar panels collect sunlight in DC power, most plugs and outlets are in AC power. DC stands for direct current, where voltage is held constant. AC stands for alternating current, where voltage oscillates with time. AC power allows electricity to transmitted over a longer distance,as the voltage and be scaled up and down easily, which is why it is used for residential electricity. Inverters convert DC power to AC power by changing the DC voltage back and forth. Inverters are included in many electrical devices, since things like batteries also use DC energy while drawing AC energy from walls. [4]

Voltage Regulator/Charge Controller - device for managing voltage from solar panel to battery by providing the battery with the optimal current and keeps it from overcharging.[5]

Battery- stores electricity for later use. Lead-acid batteries are often used but nickel-cadmium batteries are common as well.[5] Sealed lead-acid batteries are frequently used in PV systems because they require no maintenance, no distilled water (as opposed to vented nickel-cadmium), and they don't spray acid from their vents like unsealed lead-acid batteries with high-antimony plates do. Like some other batteries, sealed lead-acid batteries require a charge regulator. Another consideration of sealed lead-acid batteries is that "they can be permanently damaged by sulphation if stored for several months without charging."[6]

Light Bulb - lighting is the main use of electricity in small solar systems and choosing an efficient bulb ensures the PV system can power the light.[5]

Wiring Basics[edit]

Most PV modules are produced as 12-volt modules, and in order to reach the system voltage, series wiring and parallel wiring of batteries is required. The diagrams, sizing charts and other useful information can be found in the book referenced in this section.[7]

Teaching Methods[edit]

In many classrooms, project based learning is utilized to encourage the use of prior experiences and understandings to solve problems. Positive results have been found connecting project based learning to learned and retained content knowledge. Also students are shown to have gained skills including teamwork, communication, and problem solving skills. [8] Project-based learning provides a sense of post education project skill practice. Project-based learning is the easiest and most efficient way to achieve multiple outcomes.[9] When students are engaged in constructing real world projects, it often affects their experiences surrounding project outcome. Utilizing projects as a way of learning often opens up students minds to use past knowledge and skills to solve problems, as well as developing and gaining new skills to complete tasks.[10]


Rural Solar Electrification[edit]

Solar energy systems can conveniently be located off the grid, which is perfect for the developing world. Off-grid small scale solar home systems(SHSs) are cost effective ways to respond to energy poverty challenges. SHSs allow rural communities around the world to gain energy without relying on expensive fossil fuels, like kerosene, or attempting to extend national electricity grids, which comes with a high price tag. While SHS programs greatly enhance quality of life in the developing world, the high upfront cost of these systems tends to only allow middle and upper class rural homes to have access and the systems are prone to theft and damage. However while they are expensive and hard to come by, there are more than 40 SHS programs around the world that are committed to installing these systems in efforts to curb energy poverty through off-grid electrification.[11][12] For some communities in isolated rural locations, the unfamiliarity with modern technology presents a barrier to the effectiveness of the PV systems. Maintenance is crucial for the long-term use of PV systems. "Modules must be kept reasonably free of dust and bird droppings, and electrical connections must remain tight and corrosion free. Such tasks are far removed from the experience of many rural communities." [13]

References[edit]

  1. 1.0 1.1 Bullock, Charles E. (1934). Making the Sun Work For You. New York, NY: Can Nostrand Reinhold Company. 40-57
  2. Kreider, J., & Kreith, F. (1982). Solar heating and cooling: Active and passive design (2nd ed.). Washington : New York: Hemisphere Pub. ; McGraw-Hill, 7-152.
  3. Haberlin, H., Eppel, H., ProQuest, ProQuest CSA, & Ebooks Corporation. (2012). Photovoltaics: System design and practice. Hoboken, N.J.: Wiley. 91-93
  4. Worden, J., & Zuercher-Martinson, M. (1982). Inverters and Converters . 1982 IEEE Power Electronics Specialists conference, 2(3). doi:10.1109/pesc.1982.7072403
  5. 5.0 5.1 5.2 Roberts, S. (1991). Solar electricity: A practical guide to designing and installing small photovoltaic systems. Englewood Cliffs, N.J.: Prentice Hall, 37-133.
  6. Roberts, Simon. Solar Electricity: a Practical Guide for Designing and Installing Systems: Ill.: Bib. UK: Prentice-Hall, 1996.
  7. Schaeffer, J., & Pratt, D. (2001). Solar Living Sourcebook: The complete guide to renewable energy technologies and sustainable living (11th ed., Real Goods solar living book). Ukiah, CA : White River Junction, Vt.: Gaiam Real Goods ; Distributed by Chelsea Green Pub, pg 478.
  8. Ralph, Rachel A. "Post secondary project-based learning in science, technology, engineering and mathematics." Journal of Technology and Science Education 6, no. 1 (2016).
  9. Lenz, B., Wells, J., & Kingston, S. (1991). Deeper learning : transforming schools using common core standards, project-based learning, and performance assessment. Retrieved from https://ebookcentral.proquest.com
  10. Boss, S., & Krauss, J. (2014). Reinventing project-based learning : your field guide to real-world projects in the digital age. Retrieved from https://ebookcentral.proquest.com
  11. Karoly, R., Iorga, N., Dorin, B., & Cristian, D. (2014). Energy Monitoring and Load Control. Application for an Off-Grid PV System. Scientific Bulletin of the Petru Maior" University of Tîrgu Mureș, 11, 30-33. Retrieved February 16, 2018.
  12. Sovacool, Benjamin K., and Drupady, Ira Martina. 2012. Energy Access, Poverty, and Development : The Governance of Small-Scale Renewable Energy in Developing Asia. Abingdon: Taylor and Francis. Accessed February 14, 2018. ProQuest Ebook Central. https://ebookcentral.proquest.com/lib/humboldt/reader.action?docID=1068875&query=
  13. Lynn, Paul A. Electricity from sunlight: an introduction to photovoltaics. Chichester: John Wiley & Sons, Ltd, 2010.