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Background

Bob and Cody will be modifying the off-grid photovoltaic system out at the Arcata Educational Farm. The system already in place consists of most components; solar panel, battery, charge controller, wiring, and answering machine. The system will power an answering machine as well as a compost toilet fan. This system provides the means for shareholders to contact the AEF for the upcoming 2008 food season. Currently, there is power to the answering machine but messages cannot be left by veteran shareholders as well as interested shareholders. We will assess the photovoltaic system; replace any broken parts (eg. old wiring, etc.) and add any components (eg. compost toilet fan) that may improve the operation of the system. Through the process of modifying the photovoltaic system, a "how to" manual will be put together for current and future directors at the Arcata Educational Farm.

Description of Opportunity

The off-grid photovoltaic system is for the directors and all share holders apart of the Arcata Educational Farm on Bayside Rd in Arcata, CA. There already is a off-grid photovoltaic system out there but messages cannot be received. We will assess the current system, and locate any problems that exist. New wiring will be added and broken parts replaced. Share holders currently cannot contact the AEF by phone so there is a need for this project to be done earlier in the semester. This is so they will be able to receive messages for the near approaching food season. Our hope is to have a working solar system when done for the AEF and all those interested in the AEF in the future. This photovoltaic system will power the answering machine as well as a composting toilet fan.

Proposed Timeline

  • - 3/29/08
ITEM PROPOSED DATE DATE MET?
Sizing of system and pricing components for client and CCAT approval 3/11/08 Yes!
Budget turned into CCAT 3/12/08 Yes!
Replace existing wiring with new wiring on photovoltaic system, install inverter, new battery and test 3/29/08 Yes!
Create user manual/maintenance log for system 4/16/08 Yes!

Criteria

Criteria Constraint Success?
Cost Under $400 Yes
Easily Maintained/Documentation Easy to maintain by others and clearly documented. -
Safe Least chance of electric shock-no exposed wiring Yes
Educational/Usable by all who are apart of AEF Answering Machine works to provide easy access tool to the farm/shareholders -
Durability Lasts for many years, continuous educational tool -

Literature Review

'There has been substantial discussion and writing on PV design, installation and maintenance. This system is not-grid connected so we focused on the same literature review done for our other project: Engr_305_solar_learning station and is here literature review and Photovoltaics.

Components on site and their functions

Cell
Thin squares, discs, or films of semi conducting material which generate voltage and current when exposed to sunlight.
Panel
Collection of PV cells designed and installed on the panel depending on serial or parallel configuration
Charge Controller/Low Voltage Disconnect (LVD)
Regulates battery voltage and controls the charging rate, or the state of charge, for batteries. LVD shuts system off when voltage drops below 11.6 v and turns it back on after the battery has charged to 12.6 v.
Absorbed Glass Mat (AGM) Sealed Battery
Storage of DC Electrical Current.
Inverter
Changes direct current (DC)generated by the Panel to alternating current (AC)used by households.
Load (Answering Machine)
Any electrical component within a circuit that draws power from that circuit.
Most loads can be turned on and off, such as a light bulb or a refrigerator.
Loads are either AC or DC.
Fuses
When a current exceeds a fuse´s rated amperage, the circuit opens and stops all current flow. When a fuse has "blown", it must be replaced.
Meter
A gauge that allows you to see from where you are pulling your power, and how much power is being drawn from the loads.
Outlet
Outlet to run AC appliances-answering machine

Operating/Maintenance Instructions for components

Answering Machine
The answering machine is a used ATT 1715 and the user's manual is on-line
Charge Controller/Low Voltage Disconnect
The charge controller is a SunSaver 10 Amp Unit and the user's manual is on-line
Inverter
The Inverter is a Xantrex XPower Inverter 400 and the user's manual is on-line

System Installation Photos

System Installation

After assessing what components could be re-used from the old system and answering machine(Fig 1,2, 3, 4)), we got together to plan out the re-installation. Cody, being better at tough installation tasks, rebuilt the battery box(Fig 6), re-wired and attached the charge controller and inverter( Fig 8 and 10), and coached Bob as he re-wired the AC portion of the system. Bob ran Romex wiring from the inverter to the AC plug box. He also wired the AC outlet as it previously had direct DC wiring(Fig 7). Bob re-wired the compost fan to protect anyone from getting shocked if they fell asleep while on the toilet(Fig 14). We basically put the new wiring where the old wiring was but installed it just a little better.

We were careful to have all components either covered from the elements or away from incidental human contact.This part was actually easier than the learning station as we could work at the same time instead of one at a time because of space. Once we were done and plugged in the new answering machine, it all worked perfectlyand it looked good(Fig11, 12, and 13)! For awhile.....

System Testing

First we assessed the current system and figured out which components were still good and which ones were bad. The battery was five years old, would not hold a charge, and needed to be replaced. The charge controller still worked, but we decided to replace the old one with a new charge controller with a low voltage disconnect (LVD). This prevents the battery from being discharged to levels that decrease its life.

Using the old wiring coming from the solar panel, we tested the voltage coming from the panel to the charge controller. Only 1.79v were coming through so our initial thought was a bad panel. CCAT had some panels and were willing to donate one in case the original was bad. On a sunny day the panels in their Solar Trailer were all tested and one very similar to the existing panel was donated to us. But, it turned out that it was the old wiring. After removing the old wiring and testing the panel, it showed us 19.5v. The lifespan of a panel at full voltage is 15 - 25 years and after that the voltage output only slightly decreases.

After the system was completely installed, we tested the answering machine and everything worked. We were able to leave messages on the answering machine for a week before the system turned off. It now has been a full week and the system has not yet turned on, we tested our system at every point checking to make sure that our wiring was done correctly. The wiring was determined good and now we are testing individual components. The inverter worked when hooked up to battery, so now we're testing the battery to make sure it will hold a charge. All components are new so it is difficult to troubleshoot a new product being bad. After charging the battery up with a battery charger a load test was performed to make sure the voltage didn't drop rapidly. The battery was determined good, so now its down to the charge controller. With the battery charged we hooked it back up to the system and it is currently working again. At this point its a matter of patience, time, and more trouble shooting if the problem persists.

List of steps to take when testing this system:

  1. Test system meters-Test on a device where you know the voltage and verify it is working and correct
  2. Array/panel voltage-Use a DC voltmeter/ampmeter to measure the voltage/amperage(in full sun) in an array/panel and record
  3. Battery voltage-carefully measure the voltage of the battery before and after connecting and record
  4. Check status indicators on charge controller and inverter if available
  5. Check all wiring to see if any is live by testing voltage and/or current at all points before and after a component
  6. Check all terminals and wires for loose, broken, corroded or burnt connections or components
  7. Make sure charge controller is clean
  8. Fire up the system under full sun and re-test each point and component
  9. Turn on the answering machine!

Reference: Maintenance and operation of stand-alone Photovoltaic systems (1991). Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 157

Answering machine has no power:

  • Check in another outlet to make sure it is not broken and/or try another power cord
  • Use voltage meter to check voltage by carefully touching both ends individually to a separate end of a circuit. Test outlet, panel, charge controller, battery(carefully!) to see if the voltage is at or near 12 volts
  • If any of the components have less than 12 volts, give the folks at CCAT a call.


Precautions

  • Do not touch any of the wires or components with your hands or a metal tool.
  • Never touch both terminals of the battery with anything other than a voltmeter
  • Only let someone that knows what they are doing repair or change the system or its wiring


Budget

System Cost Table
Component Cost
AGM 12 Volt 75 Amp Hour Battery $160.95
400 Watt Inverter $42.90
Charge Controller with Low Voltage Disconnect $69.95
15 Amp Fused Outlet $13.50
24 feet of Romex wiring $48.00
25 feet of 10 gauge wiring $12.25
7 Feet of 12 gauge wiring $2.45
Answering Machine $3.82
Total $353.82
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