This is the literature review and references section for the CCAT solar kiosk project.
Solar Panels Description[edit | edit source]
Solar panels transfer energy from the sun and convert that energy into electricity, a concept called photovoltaics. The general process behind the photovoltaic idea is first the sunlight strikes the solar panel, second the material on the solar panel (mostly silicon) absorbs the sunlight which forces the electrons to leave the silicon atoms and then flows on through a material away from the solar panels to conduct electricity.
There are two types of photovoltaic systems that solar panels use; first is the off-grid system and second is the grid-tied system. The off grid system is designed for rural types of environments and a major purpose of the off grid system is to provide electricity where there is not enough electricity on the grid. It stores power in the solar panels and then that energy can be used later (night time) when the solar panels are not generating electricity. The grid-tied system uses solar panels to collect energy and provide to the community on a big scale and provides lots of energy, for example a college campus. The grid-tied system is also connected to power lines, therefore if the solar panels did not work, the power lines would provide the electricity to the public. This system uses the solar panels to produce electricity first and as a backup system, the power lines will provide electricity if necessary.
Client Criteria[edit | edit source]
The client for the CCAT solar kiosk are students who live in the CCAT house, more specifically the three co-directors. It is important that we take in their considerations for how the kiosk should be built and function very precisely. Residents of CCAT know first hand what the people who will be using the kiosk most want, as well as the needs the kiosk should be addressing to assure the solar panels function are being used appropriately. Their criteria may change as the semester goes by, but as of now CCAT mainly wants the kiosk to be up and running again with new parts so the solar panels can work properly. Beyond that, they want the kiosk to be able to bring more thrill and excitement to their volunteer Fridays for students who come out to work with them. So far, they have mentioned they would like to see the kiosk be able to charge a speaker and phones so music can be playing outside along next to volunteers to keep them motivated and having fun working, yet showcasing a good example of appropriate technology. This would include making a storage box to keep the speaker and any adapters or chargers safe from theft and also safe from the weather.
Science Terms[edit | edit source]
Power is the rate of doing work or Power = Work/Time (Volts x Current=Power). Energy is the potential work that can be done on the system. It can transform into other forms i.e. solar into electricity, but energy can never be destroyed only transform. A Watt is the International unit for power and it is also a rate at which energy is being used or Watts = Joules/Time. A Joule is the international unit for energy and it is a Joule = Newton*Meter. Voltage is how much electrical potential an item has.
Solar Kiosk Components[edit | edit source]
Sizing[edit | edit source]
For our project we are given two 100 watt solar panels. One 100 watt solar panel could charge a 100 Ah battery in two days (20-25 hours), depending if the sun was out the entire day and the number of amps one 100 watt solar panel produces in an hour is roughly 5 amps. The number of amps depends on two factors; voltage and watts. To determine the voltage size on a battery, we need to know the number of watts a solar panel will produce and how many amps the total system produces. In a past solar kiosk project that was accomplished by CCAT, known as the CCAT Solar Charging Station, a few years ago. The number of amps being produced is 8.77amps and since we have the number of watts of a solar panel, which is 100 per solar panel. We can then find voltage on a battery with this formula, Volts = Watts/Amps. 100/8.77 = 12 Volts. So a 12 volt and 100 A/h battery may be required for our project.
A charge controller regulates how much voltage or electricity travels into the battery, preventing the battery from overcharging and overheating. The size the controller needs to be greater then the number of amps being used in our system. For example we have 8.77 amps and thus we would need a a charge controller great then 8.77 amps to protect the battery from not working properly.
Kiosk Material[edit | edit source]
The CCAT solar kiosk will be built on and around the already existing CCAT papercrete clayslip demo wall. The demo wall has an outer frame made of natural logs on the sides and 4x4 lumber running across the top to connect the two logs. The roof is made of 20 square feet of plywood layered with cedar shingles on top to act more roof like to protect the wall from rain. The inner wall is composted half by paper-crete bricks in the shape of cinder blocks and the other half is clay-slip-straw stuffed around the bricks. The paper-crete bricks are a mixture of paper:cement:water:sand at a ratio of 3:2:3:1. The clay-slip-straw is just straw dipped into clay. The straw remains in the wall by a wood lath allowing the wall to be maximally stuffed with straw with the bricks in the very center. Finally, the wood lath with the bricks and straw stacked in-between, is painted with a natural plaster.
Batteries, charge controllers, and fuses[edit | edit source]
Batteries can be necessary to be part of the system along with solar panels to store the energy made from the panels to provide a constant power source for charging equipment. Most batteries are used for storing solar energy and lead batteries can be recharged many time in their life.. Lead acid batteries recharge by having lead at the cathode end be oxidized and the anode lead is reduced. During usage, the cathode is reduced and the anode is oxidized. Lead acid batteries have the potential to last 10 years in optimal conditions. Although they realistically last around 5 years and are used heavily charging electronics, and weather is a factor in determining the life of a battery. Too hot of climates assist in degrading the battery.
Solar panels can haul in a lot of electricity, so a charge controller is needed to manage the flow of electricity in and out of the battery and cords running to direct current (DC) appliances. A charge controller makes it so while using the system to draw electricity out of or drawing in from the panels, the battery won't overcharge/overheat and brake. It does this by managing the flow of energy in and out from the battery; adjusting the current with a temperature sensor but still allowing the maximum flow of energy within the battery's capability.
It is possible a PV system could have a large power overload or grounding fault and could lead to damaged electrical equipment or even start a fire. Even in a small PV system, only charging DC appliances, it is necessary to use fuses for precaution. Fuses are a small piece of metal wire that melts when overheated which will stop the flow of electricity. Fuses must be replaced once melted. It is noted to buy fuses that can handle slightly more voltage than the normal current flowing through the system.
Direct Current Appliances[edit | edit source]
Temporary Direct Current, or DC, provides constant voltage or current in a single direction. For example a cell phone battery or any type of battery is a type of dc appliance. The battery provides the phone with power to function over a certain amount of time and when the battery runs out of energy, the phone does not function. Another analogy is a electronic portable device that does need to be fed constantly (like a wall outlet) is usually a dc appliance.
Some common examples of DC devices are bluetooth speakers, lighting, computers, cellphones, security systems. Rechargeable electronics such as computers, cellphones, and speakers use about 10-20 watts. Lighting use around 11-30 watts and security systems use 20-30 watts. For reference, a common household dryer uses about 2800 watts. The two solar panels should provide enough energy for small DC appliances.
Similar Examples[edit | edit source]
Jeanne Marie's story: Solar kiosk franchisee in Rwanda
Jeanne Marie Uhiriwe possess one of the 25 solar kiosks in Rwanda. The components of her kiosk consist of the following items; a pair of 40 watt solar panels, a lithium ion battery that draw power from the solar panels, 30 outlets to charge electronic devices, a big plastic container to keep the structure intact and a bike to make the solar kiosk easily transportable. People who want to use the device pay Jeanne 14 cents for two hours to charge any electronic device of the client's choosing.
One Billion Have No Access To Electricity — Solar Kiosks Can Help
SolarKiosk Gmbh is a company based out in Berlin that helps people in Africa to have better accessibility to electricity and one method they use to provide electricity to the public is by using the solar kiosk method. A standard solar kiosk that SolarKiosk Gmbh provides can charge 220 cellphones every day. Solar kioks also have the potential to charge items such as a laptop, a refrigerator and rarely a cell phone tower. The company has made accessible 45 solar kiosks to the public and one particular aspect that company is interested in is to observe the economic impact of many solar kiosks that are close together.
The Energy Kiosk Model, Current Challenges and Future Strategies
In a village called Avartsena, there were 5000 people with no access to electricity and then the Higher Education Research Institute opened up a solar kiosk in the village of Avaratsena in Madagascar in 2012. Which then people could rent lamps and use as a greater light source rather then using candles which are not as efficient and both of the items cost the same to use. Now people in Avaratsena do not need to walk several kilometers to charge their phone since they have a portable solar kiosk in their village.
- Nagawiecki, Tom. A Beginners Guide to On-Campus Solar Development, aashe.org/Google Scholar 2009 pg. 6-7.
- NA. 12v Solar Panel, Photonic Universe, 2016
- Andorka Frank. How to choose the perfect charge controller, Solar Power World, 2014.
- NA. Basic of a Solar Cell, Leonics. 2013.
- Boxwell, Michael. Solar electricity handbook: a simple, practical guide to solar energy: how to design and install photovoltaic solar electric systems. Greenstream Publishing, 2012
- Sullivan, J. L., and Leigh Gaines. A review of battery life-cycle analysis: state of knowledge and critical needs. No. ANL/ESD/10-7. Argonne National Laboratory (ANL), 2010.
- Ruetschi, Paul. "Aging mechanisms and service life of lead–acid batteries." Journal of Power Sources 127.1 (2004): 33-44.
- Boxwell, Michael. Solar electricity handbook: a simple, practical guide to solar energy: how to design and install photovoltaic solar electric systems. Greenstream Publishing, 2012.
- Garg, Akshat. Charge Controller Solar Power Battery Charge System. Academia. RLH Industries, Inc., 2017.
- Khatib, Tamer. "Standalone Photovoltaic Power Systems." Journal of Applied Sciences 10.13 (2010): 1212-1228.
- Khatri, Ishan. What is the difference between AC and DC currents?. Quora Incrporated, 2015.
- Catalog of DC Appliances and Power Systems, Ernest Orlando Lawrence Berkeley National Laboratory, 2011. pg 26
- Gilks, Tom. Jeanne Marie's story: Solar kiosk franchisee in Rwanda, One Campaign, 2015.
- Richardson Jake. One Billion Have No Access To Electricity — Solar Kiosks Can Help, Solarlove, 2015.
- Knobloch, Claudia & Hartl, Judith. The Energy Kiosk Model, Current Challenges and Future Strategies. Endeva Business Model Library. 2014.