Our group was given the opportunity to work with the non-profit organization We Share Solar to assemble solar suitcases and teach a class about them as well. These solar suitcases are off-grid solar powered kits that provide light and charging capabilities to places with no access to electricity. Throughout our project, we assembled several small solar suitcases, as well as two big ones that we are sending back to We Share Solar and eventually will be sent to a community who needs them. We also ran a lab with our engineering class, using the instruction manuals provided as well as a power point presentation we created to go along with it, where we helped our peers assemble the solar suitcases so they could learn about off-grid solar systems.
Background[edit | edit source]
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.
We Share Solar is the educational program of We Care Solar, a 501(c)3 organization dedicated to bringing light and power to maternal health clinics in the developing world.
Problem Statement[edit | edit source]
The objective of this project is for our team to construct a Solar Suitcase and design a lab session for our engineering class where we will teach about Photovoltaics and how to construct the portable Pv-cell suitcase. We also hope to consider any aspects of the design that we could suggest changes to that would 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, the Schatz Energy Research Lab, and We Share Solar
Criteria[edit | edit source]
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.
|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.||9|
|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 | edit source]
This is a review of the available literature pertinent to the HSU Solar Suitcase Project.
Photovoltaic (PV) systems[edit | edit source]
Systems that capture energy from the sun and convert it into electricity.
Radiant Solar Energy[edit | edit source]
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.
Components[edit | edit source]
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.
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.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.
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.
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.
Battery- stores electricity for later use. Lead-acid batteries are often used but nickel-cadmium batteries are common as well.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."
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.
Wiring Basics[edit | edit source]
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.
Teaching Methods[edit | edit source]
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. 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. 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.
Rural Solar Electrification[edit | edit source]
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.
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."
Prototyping[edit | edit source]
For our project, we were lucky enough to have We Share Solar provide us with the solar suitcases and the tools we needed for our project. As for prototyping for our project, we decided to design a lab that we could run through with the class while they were simultaneously assembling their own solar kits in small groups.
We didn't create this lab until we had fully constructed a small solar suitcase ourselves and tested it in the sunlight. Construction of the kit will be included in the "Construction" section as well as the construction of our lab presentation.
This lab ended up consisting of a power point presentation in which we had step by step instructions that followed along with the instructions manuals provided in the solar suitcase kits.
Construction[edit | edit source]
To construct the smaller, educational solar suitcase, our team met up in the library. We followed the instructions manual step by step, and ultimately got the suitcase assembled in its entirety. After this, we tested it in the sunlight, however it did not work.
This photo shows the charge controller not reading that we had the panel connected to the solar kit. While the light bulb did turn on, it only did so because of the stored charge in the battery.
These two photos were taken after we met with our professor to figure out why our panel wasn't charging our battery. Once we got it working properly, it worked perfectly. As you can see, the charge controller displays that the panel is connected and charging the battery, which in turn is powering the light bulb. We were also able to charge our cellphone with the solar suitcase.
The large suitcases, provided by We Share Solar, were also constructed by us and will be sent to another country by We Care Solar.
While the learning suitcase is shipped with one lightbulb, the larger suitcases come shipped with 3 bulbs; one wired to a switch in the system and two more wired through a lightswitch, which can be mounted.
Once we got the solar suitcases up and running, it was time to run our lab with our ENGR 305 class. Below are some photos of the class assembling the suitcases in small groups.
Once the suitcases were all assembled we took them outside to test them out. Lucky for us it was a sunny day and all of the suitcases successfully worked!
Timeline[edit | edit source]
This is our proposed timeline for our project. Ideally we will accomplish all items by their assigned date, but with testing, we need sunlight to use panel, and we could possibly be setback by weather. We hit most of our dates spot on, however getting the big suitcase assembled came to be a bit later than the anticipated timeline.
|2/18/18||Assemble Small Solar Suitcase|
|3/04/18||Test with panel and sunlight|
|3/25/18||Create and finalize lab|
|3/28/18||Perform lab with class|
|3/25/18 - 4/15/18||Assemble Big Solar Suitcase|
|5/8/18||Present Final Project to class|
|5/8/18 - 5/11/18||Return Big Solar Suitcase back to Schatz|
Costs[edit | edit source]
This is our Budget Proposal for our project. All of the items used have been provided to us by Schatz Energy Research Center, initially provided by We Share Solar. The small suitcases are the kits in which we will perform our informative lab on with our class, and the big suitcases are the ones we will be constructing after completion of the lab and sending back to We Share Solar.
|Quantity||Material||Source||Cost ($)||Total ($)|
|5||Multimeter||We Share Solar||128.00||Provided|
|3||Solar Panel 10W||We Share Solar||19.14||Provided|
|7||12V Lead Acid Battery||We Share Solar||20.00||Provided|
|2||Big Solar Suitcase||We Share Solar||1,645||Provided|
|5||Small Solar Suitcase||We Share Solar||N/A||Provided|
Operation[edit | edit source]
Maintenance[edit | edit source]
The Solar Suitcase is designed to require relatively little maintenance. Broadly speaking, the three most important maintenance steps are: making sure all wiring is connected properly and undamaged, keeping the panel adequately clean and in direct sunlight, and replacing the battery at the end of it's lifespan.
Schedule[edit | edit source]
This is a general time-frame for maintaining the Solar Suitcase:
- Make sure the system is turned on so the battery stays charged.
- Briefly check the wire connections to make sure the connection is good and the wires aren't under any stress.
- Briefly check the panel for dirt or debris and clean them with water and a soft cloth if needed.
- Check the accessories and replace them if necessary.
- Every 2 Years
- Replace the SLA Battery.
- Every 5 years
- Replace the LFP Battery.
Conclusion[edit | edit source]
Testing results[edit | edit source]
In order to test our project, we put on an in-class, hands-on lab where our Appropriate Technology class split up into groups of three or four and worked together to assemble the small solar suitcases. Our group first gave a presentation introducing the solar suitcases and showed GIF's of each assembly step. The small groups that the class split up into allowed our team to be available to walk around and assist if needed. We wanted to limit the number of times we had to step in and physically do the assembly step for a group. Also during this time we were able to record what we observed people doing, and what they were talking about if they had questions or comments. Some of these observations included:
- Not much reliance on the GIF powerpoint
- Groups took turns assembling parts of the kit
- The groups worked at different paces, which led to more reliance on the manuals
- When groups found it difficult to judge the orientation of the manuals assembly pictures, they referred to the powerpoint
- Some groups assembled their kits based off of the circuit diagram rather than going step by step
- A few groups had difficulty testing their assembled kits
- Some groups found the end result to be anticlimactic
Discussion[edit | edit source]
All groups successfully assembled and tested their solar kits, thus concluding the lab. After the lab ended a few of our group members discussed with our professor how we believed our lab went. It was then when we had agreed that the assembly GIF powerpoint was a bit redundant, and was not necessary for the lab. We observed the groups putting together kits and how they relied heavily on the manuals, and rarely on looked the presentation. This was not the results we were expecting. Having struggled ourselves with some of the assembly instructions, we felt as though the GIF's of the steps would be helpful to include in our lab design. However, we had not considered that having put together the solar kit ourselves, we would be there to assist the groups where we thought the manual fell short. We had been trying to come up with a happy medium of helping the groups as much as we could, and letting them push through the difficult steps. We observed the groups ask for help on a certain part, over looking at the presentation playing.
The small groups of 4-5 people were a good size that allowed for everyone to contribute to building their kit.
Lessons learned[edit | edit source]
Lessons learned during this project were to not recreate the wheel. The manual did its job of telling its user how to assemble the solar kit, so by creating our powerpoint to instruct the lab groups how to assemble the kits we just created a different version of the manual. From this, we observed not much use of the powerpoint by the groups when constructing the kits, thus telling us that it was unnecessary.
This lab could have benefited from a more structured, informative version of the manual. Going through step by step with the groups about what each part of the assembly process does and why we are doing it would benefit the students. Also, including an assignment that goes along with the construction may be helpful.
Next steps[edit | edit source]
The next steps for our project will include the suitcase's journey to another country where electricity is not as prevalent than in the US. Our professor plans to take one of the learning kits with him on his trip this summer (2018). As for the other six learning solar kits, they will remain on campus to be reused in the Engineering 305 class to learn about solar circuits. For the larger two kits, one will be sent off to an African country to be used by a community in need, while the other will remain at the Schatz Energy Research Center.
Troubleshooting[edit | edit source]
|System not working||Check the wiring; is everything connected properly?|
|System still not working||Check the panel; is it obstructed by shade, by debris/dirt, or bad weather?|
|System still not working||Check the date on the battery; does it need to be replaced?|
|System STILL not working||Call the number on the inside of the kit; it will refer you to the nearest installer
OR go to the troubleshooting section of the user manual or wesharesolar.org
Team[edit | edit source]
The following people made up SENS Design, during ENGR 305 Spring 2018 at Cal Poly Humboldt:
References[edit | edit source]
- Bullock, Charles E. (1934). Making the Sun Work For You. New York, NY: Can Nostrand Reinhold Company. 40-57
- Kreider, J., & Kreith, F. (1982). Solar heating and cooling: Active and passive design (2nd ed.). Washington: New York: Hemisphere Pub. ; McGraw-Hill, 7-152.
- Haberlin, H., Eppel, H., ProQuest, ProQuest CSA, & Ebooks Corporation. (2012). Photovoltaics: System design and practice. Hoboken, N.J.: Wiley. 91-93
- Worden, J., & Zuercher-Martinson, M. (1982). Inverters and Converters. 1982 IEEE Power Electronics Specialists conference, 2(3). doi:10.1109/pesc.1982.7072403
- Roberts, S. (1991). Solar electricity: A practical guide to designing and installing small photovoltaic systems. Englewood Cliffs, N.J.: Prentice Hall, 37-133.
- Roberts, Simon. Solar Electricity: a Practical Guide for Designing and Installing Systems: Ill.: Bib. UK: Prentice-Hall, 1996.
- 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.
- Ralph, Rachel A. "Post secondary project-based learning in science, technology, engineering and mathematics." Journal of Technology and Science Education 6, no. 1 (2016).
- 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
- 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
- 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.
- 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=
- Lynn, Paul A. Electricity from sunlight: an introduction to photovoltaics. Chichester: John Wiley & Sons, Ltd, 2010.