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It has become an international challenge to offer the world's people clean and reliable energy. It is imperative that we begin to utilize sustainable energy sources rather than rely on dwindling fuel supplies and uncertain political alliances. Sustainable energy sources are those that are constant, are renewable and will not deplete our earths delicate ecosystem. Solar electricity is merely one example of a sustainable energy source, and is offered to us through a technology called photovoltaics.

Energy from the Sun

• Photovoltaic (PV) systems produce electricity directly from sunlight. “Photo” meaning light is refering to the sun’s natural energy, which is absorbed by silicon panels. Discovered in the 1950’s by Bell Laboratories, silicon has the ability to convert energy directly into electricity. “Voltaic” refers to this voltage or the unit of force (electric pressure) that causes electrons to flow through a wire.

• Solar energy is the most efficeint form of electricity to use in a developing nation. Because developing nations lack finacial and material resources to maintain a conventional fuel system, photovoltaic modules are the most practical alternative. Beyond practicality, these systems hold far more advantages to the conventional systems. For this particular project, the photovoltaic module will be used to provide energy to four homes in a rural community in Argentina. A viable photovoltaic system requires little maintanace and repair, and will not be too costly for the recipients since it will eventually pay for itself.

• PV energy is a completely clean, inexhaustible source of electricity that does not require the extraction or consumption of fossil fuels. Photovoltaic modules are extremely safe and reliable products, with minimal failure rates and projected service lifetimes of 20 to 30 years.

Advantages of Photovoltaic Technology

Photovoltaic technology holds a number of unique advantages over conventional power-generating technologies. PV systems can be designed for a variety of applications and operational requirements, and can be used for either centralized or distributed power generation. PV systems have no moving parts, are modular, easily expandable and even transportable in some cases. Sunlight is free, and no noise or pollution is created from operating PV systems. It does not require the use fossil fuels such as coal, oil or natural gas in the energy production process. Alternatively, conventional fuel sources have created an array of environmental problems, namely global warming, acid rain, smog, water pollution, rapidly filling waste disposal sites, destruction of habitat from oil spills, and the loss of natural resources. PV systems do no pose such environmental consequences. Most PV modules use silicon as their main component. The silicon cells manufactured from one ton of sand produce as much electricity as burning 500,000 tons of coal (Solar Energy International 2004). PV systems that are well designed and properly installed require minimal maintenance and have long service lifetimes.

Solar Energy International (2004) indicates that there are many other benefits to consider when choosing photovoltaic technology:

• Reliability: Even under the harshest of conditions, PV systems maintain electrical power supply. In comparison, conventional technologies often fail to supply power in the most critical of times.
• Durability: Most PV modules available today show no degradation after ten years of use. With the constant advancement in solar energy systems, it is likely that future modules will not show signs of degradation for up to 25 years or more. PV modules produce more energy in their lifetime than it takes to produce them.
• Low Maintenace Cost: PV systems do not require frequent inspection or maintenace. Transporting supplies may get costly, but these costs are usually less than with conventional systems.
• No Fuel Cost: Since there is no fuel source, there is no required spenditure on the purchasing, storing, or transporting fuel.
• Reduced Sound Pollution: PV systems operate silently and with minimal movement.
• Photovoltaic Modularity: Unlike conventional systems, modules may be added to photovoltaic systems to increase available power.
• Safety: PV systems do not require the use of combustiable fuels, and are very safe when properly designed and installed.
• Independance: PV systems may operate independant of grid systems. This is a large advantage for rural communities in nations lacking basic infrastructure.
• Electrical Grid Decentralization: Small-scale decentralized power stations reduce such possiblitities as power outages, which are often frequent on the electric grid.
• High Altitude Performance: When using solar energy, power output is optimised at higher elevations. This is very advantagoeus for high altititude, isolated communities where diesel generators must be de-rated due to the loss in efficiency and power output.

Disadvantages of Photovoltaic Technology

Initial costs tend to be a disadvantageous when implementing photovoltaic systems. Since PV is new technology, the economic costs are naturally high. As PV systems become more widely used and conventional fuel sources become more expensive, initial costs will decrease and PV technology will become increasingly available.

Solar Energy International (2004) mentions these other disadvantages:

• Variability of Solar Radiation: Systems must be modified to meet the specific solar requirements of the site.
• Energy Storage: Some PV systems require batteries to store energy for night use and for overcast days. This increases the size, cost, and complexity of a system.

Photovoltaic System Compontents

• Photovoltaic Cell: Thin squares, discs, or films of semiconducting material which generate voltage and current when exposed to sunlight. This is the basic unit of a photovoltaic module.
• Module: Configuration of PV cells laminated between a clear superstrate (glazing) and an uencapsulating substrate.
• Panel: One or more cell modules.
• Array: One or more panels wired together at a specific voltage.
• Charge Controller: Equipment that regulates battery voltage and controls the charging rate, or the state of charge, for batteries.
• Battery: A medium that stores direct current electrical energy.
  • Deep-Cycle Battery: this is a type of battery that can be discharged to a large fraction of capacity many times without damaging the battery. (Lead-acid batteries can usually be discharged up to 80 percent without damaging the battery).
• Inverter: An electrical device that changes direct current to alternating current.
• Load: Anything electrical within a circuit that draws power from that circuit. Loads can be turned on and off (such as a lightbulb or a refigerator).
• DC Loads: Appliances, motors, and equipment powered by direct current.
• AC Loads: Appliances, motors, and equipment powered by alternating current.

Terminology

• Photovoltaic (PV): a way of converting photons of sunlight into electricity.*Electricity- the flow of electrons through a circuit.
• Voltage: the force or pressure of moving electrons in a circuit.
• Amperage: the flow rate of electrons.
• Watts: the power of a system
  • Volt:(V) the unit of force (electrical pressure) that causes electrons to flow through a wire. Volts are abbreviated 'V', or expressed by the symbol 'E'. Electrical pressure is occasionally referred to as the electromotive force (EMF). Common voltages used in smaller systems include 12v, 24v, and 48v. Most homes use 120v and 240v systems.
  • Amp/Current:(A)/(I) the unit of electrical current flowing through a wire. They are abbreviated as 'A', or 'I' for the intensity of the current.
  • Watt:(P) the unit of electrical power equivalent to a current of one ampere under the pressure of one volt. This is referring to the rate at which an appliance uses electricity or the rate at which electrical energy is produced.
  • Watt-hour:(Wh) the rate of electrical energy consumption in a given hour.
  • Resistance:(R) the property of a conductor which opposes the flow of an electric current resulting in the generation of heat in the conducting material. Resistance is measured in ohms.

P = Power or Watts

Watts(P) = Current(I) X Volts(V)

Watts X Hours = Watt-hours (Wh) = Quantity of energy use or production

1,000Wh = 1 Kilowatt-hour (kWh)

Volts(V) = Current(I) X Resistance(R)

Types of Current

• Direct Current (DC) is electric current that flows in only one direction. DC can be stored.
• Alternating Current (AC) is electric current caused by a magnetic field in which direction of flow reverses at frequent, regular intervals (first in one direction, then reversing to the other direction). AC must be used immediately.

DC Versus AC

• Photovoltaic power systems are generally classified according to their functional and operational requirements, their component configurations, and how the equipment is connected to other power sources and electrical loads. The two principle classifications are grid-connected or utility-interactive systems and stand-alone systems. Photovoltaic systems can be designed to provide DC and/or AC power service, can operate interconnected with or independent of the utility grid, and can be connected with other energy sources and energy storage systems.

• Photovoltaic panels take in sunlight through the silicon cells, which produce direct current electricity (DC). The current flows from the solar panel, through the positive and negative wires, and into the load/resistance.
  • When using DC, you must utilize the electricity that is provided immediately.
  • If you wish to use the electricity during the night when the sunlight is not available to provide electricity, a battery can be attached to store the electric current so that it can be used at a later time. A Direct Current system is beneficial when your loads are not far from the solar source (i.e. the longer the wire, the more loss in efficiency of a DC system).
  • If you have a system in which your loads are far apart from each other, an Alternating Current (AC) may be your best bet. This system incorporates an inverter, which converts the current from DC to AC.

Series and Parellel Connections

• Series Connection - when connecting electrical equipment in series, attach all positive leads to negative leads. This configuration causes the voltage to increase, while the current remains the same.
  • Volts Add - V total = V1 + V2 + V3 + ....
  • Current stays the same - I same
  • Resistance Adds - R total = R1 + R2 + R3 + ....
• Parallel Connection - when connecting electrical equipment in parallel, attach all positive leads to positive leads, and all negative leads to negative leads. This configuration cause the current to increase while the voltage is constant.
  • Volts stay the same - V same
  • Current Adds - I total = I1 + I2 + I3 + ....
  • Resistance Adds under 1 - 1/R total = 1/R1 + 1/R2 + 1/R3 + ....

Project Description

This photovoltaic project was designed to provide lightbulb electricity to a home in Central Argentina. There will be six lightbulbs used, four inside the home and 2 outside of the home. This home will be constructed by Kleiwerks and the lighting will provide an example for the community to understand how photovoltaic systems work, focusing on how energy is sustainably drawn from sunlight and converted into electricity to power their homes. This will be the first of many photovoltaic systems in this community.

This inparticular system is to operate loads at night or during cloudy weather. This PV systems will use batteries as a means of storing electrical energy. System loads can be powered by batteries at any time, regardless of weather. The size and configuration of a battery bank depends on the operating voltage and the amount of nighttime usage. The number of modules must be adequate to recharge the batteries during the day. It is very important not to let the batteries discharge or overcharge as either situation will damage them severely. A charge controller will disconnect the module from charging once the battery has fully loaded. Some charge controllers can also prevent the batteries from discharging too much by stopping the supply of power to the DC load. The DC system’s basic components include a PV module, charge controller, storage batteries, and the systems elestrical load.

Method

Imperative to the success of building such a system, the following steps are specific to folks who are working on an international project as well as students whom are first-time photovoltaic builders. Steps:

1. Who/What/Where/When/Why/How
   • Who are you building the project for?
   • What is required of the system?
   • Where are you building the system?
   • When does the system need to be completed?
   • Why are they utilizing solar?
   • How is it going to be funded?
2. Communication
   • Once you figure out the basics, communicate with your site and let them know you are taking on the project. Ask any questions that might help you in the initial planning process.
3. Design a Timeline
   • Though this will often change during the trial/error process, make a tentative timeline and try to stick to it. Keep a journal and record all progress and include a communication log with your site. Remember that things will always take longer than you think - so get started EARLY!
4. Buy a Book
   • I recommend purchasing "Photovoltaics: Design and Installation Manual" and make it your new best friend. If you are new at photovoltaics, and have never worked with electricity before, you may require many nights of book-bonding in order to make sense of pv systems.
5. Contact Locals
   • Finding people in town who can help you answer questions will assist you in your learning process, and may also be available to help you during the construction of your project.
6. Draw a Preliminary Design
   • Make sure you've figured out how to set up the whole entire system with all the parts. Draw out the system and label everything to make sure you've got every part labeled that you will need.
     • Gather site data
     • Calculate load estimates
     • Determine number of pv panels
     • Determine how to wire pv panels together (series/parellel)
     • Determine how the system will be mounted
     • Determine battery type, sizing and wiring configurations
     • Determine controller type, sizing
     • AC or DC - Determine if you need an inverter
     • Determine how much wire your system will require based on distances of equipment
7. Write a Budget
   • Figure out where you are purchasing all your materials (make sure they have it in stock), how much each will cost, and what the total price will be for the project.
8. Get Funding
   • Turn in your budget to be approved for funding. Discuss with them how you will go about purchasing the materials. (i.e. are they giving you money upfront, are you to purchase and get reimbursed, etc.)
9. Gather Electrical Materials
10. Practice Wiring your PV System
    • I found it was very helpful to sit with my materials and wire everything together before trying to really "build" the system. Just hook up all your electrical materials and make sure that your loads are operating. Use the voltage meter to see where your electricity is being pulled from if you are using an AC system.
11. Gather Mounting Materials
    • Think about how you need to set up your system. Are you building it on a roof? Are you buidling your own mount on the ground somewhere? Gather some materials from local junkyards to construct the mount for the system. I collected most of my mounting materials from the metal junk yard and from a resale lumber yard.
12. Build the System
    • I made an "A-Frame" mount for my photovoltaic system that I designed myself based on where the weight distribution would need to be supported the most.
13. Test the system
    • The best way to test the system is by re-wiring the system to make sure that all your connections are secure and that you have reevaluated all the parts to make sure that they are doing their job properly within the system.
14. Draw Diagrams
    • This will help you in the presentation process, as well as those who are trying to understand why and how everything works the way in which it does. It will also help you organize your thoughts so that you can review all the information - ultimately re-learning the logistics of the system design.
15. Write up a report
    • Include any difficulties or problems you encountered during the learning process. This will also be good to review the next time you are interested in working on a similar project. A report serves as a guideline for those whom are also interested in working on a similar project.
16. Teach somebody
    • If you don't have a class to present your project to, teach your friends/family/neighbors/roommates. Teaching someone will solidify your knowledge of photovoltaics, as well as introduce you to some new questions you may not have thought of on your own. THIS IS KEY!

Electicity Materials

• 3 - 50 Watt/12 Volt Photovoltaic Panels
• 1 - Solar Charge Controller
• 1 - 12 Volt Battery
• 1 - 400 Watt/110 Volt Mod-Sine Inverter
• 6 - 15 Watt Compact Flourescent Lightbulbs
• 6 - Light Sockets
• 1 - Light Switch
• Wires
• Colored Electrical Tape

Wiring the PV System

Once I had bought all of my materials for the Photovoltaic System, I sat them all out infront of me on the floor in my home. I put the parts in chronological order (pv panels - charge controller - battery - inverter - light switch - lightbulbs). I had my wire cutters, wire nuts, and wire. I made sure that I knew where all the positive leads connected to the next positive lead and negative to the negative since I was wiring my system in parallel. I then cut around the tip of the wire to remove the protectant layer, exposing the tip of the wire. This allows me to make the connection strong between the wires I am putting together. Once I had two exposed ends of the wire, I connected them together using the wire nut. First, I connected the positive lead of the PV panel to the positive lead of the charge controller. Then I connected the negative lead of the PV panel to the negative lead of the charge controller. Keeping the positive connections to the next positive, and the negative to negative, I then connected the wires to the battery. From the battery, the wires connect to the inverter. Since the inverter had two plug outlets on the side of it instead of a place to connect raw wires, I made my own plugs by connecting the wires directly to the plug heads and wiring them into the system. I was then able to "plug in" the lights instead of having them permanently attached to the system. The lightbulbs directly plug into the inverter, and hence, are controllable by direct manipulation. There are six lightbulbs, wired in sets of three, totaling two plugs into the inverter.

Something that I was really excited about when building the system was the discovery that the charge controller actually told me where it was pulling electricity from - the panels or the battery. The charge controller also indicates how much charge the battery is currently holding and when it is adding charge to the battery from the solar electricity produced.

The inverter has a switch on the side of it to turn it on/off, which illuminates when operating.

I put a light switch between the lightbulbs and the inverter so that the clients could operate the system via a wall-plug or by switching on/off the inverter.

Mounting Materials

• Plywood
• Supports 2x4
• Nails/Screws
• Hinges
• Measuring Tape
• Hammer
• Screwdriver
• Electric Drill
• Wire Cutters

Clients/Site

Clients: San Francisco del Monte de Oro, Argentina.

Site: The Photovoltaic System was constructed in Arcata, California at the designers home. Later, it will be transported to the community in Argentina.

Costs

• Photovoltaic Panel (price for one) $285.00 Alternative Energy Engineering - Redway, California
• Solar Charge Controller $060.00 Alternative Energy Engineering - Redway, California
• 12 Volt Battery (Damaged frame) $100.00 Alternative Energy Engineering - Redway, California
• 400 Watt/110 Volt Mod-Sine Inverter $042.31 Alternative Energy Engineering - Redway, California
• 15 Watt Compact Flourescent Lightbulbs $020.00 Ace Hardware - Arcata, California
• Light Sockets $010.00 Ace Hardware - Arcata, California
• Wires $010.00 Ace Hardware - Arcata, California
• Colored Electrical Tape $004.00 Ace Hardware - Arcata, California
• Wood for mount $030.00 Resale Lumber - Eureka, California
• Hinges FREE Metal Scrap Yard - Arcata, California
• Light Switch
• Wheels
• Nails/Screws

Funding

All funding was through Hunboldt State University's Campus Center for Appropriate Technology (CCAT).

Final Design

After collecting all of my electrical and mounting materials, testing the wiring, and designing a mount, I began building the system in my front yard. To complete the building process took 5 days of labour, working about 5 hours each day (which includes making lots of trips to gather missing materials/equipment/tools). After collecting materials from the re-sale lumber yard and the junk metal shop, I began constructing the "A-frame" that I designed. I made a design that would fold into itself. My first problem with this was that I was unable to find matching wood widths. My second problem was figuring out where to properly install the hinges so that it would fold and still allow room for supports underneath each piece of wood.

Once I was able to complete the original design I had in mind, the frame folded very nicely onto itself - and it even has wheels so that I can roll the equipment around!

After building the "A-frame", I drilled holes into the large piece of plywood and attached all the parts so that they could be easily seen. Once this laborious process was complete, I was able to wire the system. After the wiring, I made diagrams for the entire system so that anyone who was interested could easily understand how the wiring was completed. Each wire is labeled and the entire back part of the plywood is accesible so that viewers can look on both sides - to see the "outer shell" of what the system will look like ontop of a mount, and what is going on behind the scenes with all the wiring - ultimately making the system easy to understand to even those who have no previous background in photovoltaics. (I tested it on a friend!)

Discussion/Conclusion

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This was an excellent project to work on! I have gained an invaluable amount of knowledge during this process. This project forced me to think about electricity, building/mounting designs, international communication, and mostly, challenged me to constantly analyse my efforts. The largest challenge for me was learning and comprehending the material on photovoltaics. I have had NO previous experience working with electricity. I will be the first to admit, I did not even know what the word 'photovoltaic' meant when I first became aware of this possibility. When I found out it was solar electricity, I immediately yearned for the opportunity - as I felt it was the best reason for me to learn and grow with a project that would be above and beyond challenging. I felt supported in that I had a class, a professor, and a knowledgable community to ask for help when I would need it. It was the one project I was skeptical of teaching myself.

Upon beginning the project, I had enormous frustrations with the material. I would read and read and read. The more I read, the more I felt lost and confused. But persistence pays off eventually, and soon enough - the material sunk in and CLICKED! It was a thrilling moment in my education, as I had to come to grips with it on my own, no matter how much or how little help I was given. It took months before I actually bought the materials, as I wanted to be sure that I knew I was not wrong in my understandings, logic and design. I also wanted to get all the materials in one swoop, so that I would not have to travel far for more than one trip. Once I obtained the materials, I sat alone in a house for four days and tried wiring the parts together. That was my next challenge! I was really concerned about connecting the wires together as I had no idea even how to attach them! In desperation, I had a friend come and show me how to put them together. The system was in place, wires connected - and the moment I plugged in a lamp - tears conjured in my eyes! I had produced a system that was conducting electricity! It was a moment I will never forget.

A couple of weekends later I drew up my final mounting design, bought my parts and started sawing away. The mount took about five days to build, including placing all the parts into the mount and wiring the system together on the mount. I must say, it sure is heavy - but it looks magnificent. It is really a treasure to have invested the work I have into this project - as the rewards are insurmountable!

Links and References

• Energy Efficiency and Renewable Energy Network - www.eren.doe.gov/pv/ : Information on how a solar cell works complete with animation.

• Komp, Richard J. - Practical Photovoltaics: Elecricity from Solar Cells :

• Solar Energy International. - Photovoltaics: Design and Installation Manual : A very thurough resource for those whom are at a beginner level or are advanced in their knowledge of pv. I would not attempt a project without this book as a companaign.