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Background

This page was added by a Humboldt State University Engineering class January-May 2015:

CCAT (Campus Center for Appropriate Technology) is an appropriate technology demonstration house on the Humboldt State University campus in Arcata, California. Student staff and volunteers work weekly at CCAT to keep it running smoothly. The Greenshed is a building where the workers store tools and work on small projects. The Greenshed solar panel powers a solar lighting system that workers can use to light the shed at night. The solar lighting system was installed in early 2013. There are eight lights powered by the panel that hang inside the shed. CCAT workers would like to use the shed at night, especially when it gets dark early in the day.

Problem statement

Problem: CCAT staff let us know the lights in the shed are too dim for workers to use the shed at night.

Our goal is to keep the lights bright at night. This project is for our Engineering 305 class (which ends May 2015). We will be investigating the solar panel, its location, the battery, wiring, and light fixtures for problems. The CCAT workers would like us to try to power their tools with the solar panel. If we find an easy solution to the brightness problem we will look into having the system power tools in the shed, adding a shut-off timer, and a data logging device.

The objective of this project is to: -Create better lighting in the CCAT tool shed -Find the best location for the solar panel to intake it's maximum -Replace and fix any poorly functioning or broken equipment -Add improvements to the system if time/resources allow (tool powering ability, shut-off timer, data-logging device)

Criteria

Below are the Project Evaluation Criteria. We will use them to judge the success of our project. We, the students working on this project, created these criteria with the help of the project manager. These criteria will help everyone working on the project know what is most important (10 being most important/non-negotiable; 1 being least important).

Criteria Weight Contraints
Funtionality 10 Produces and stores enough to sufficiently light the green-shed
Safety/Placement 10 Must be constructed and placed in risk-free positions (no hazards)
Cost 9 Does not exceed project budget
Maintainability 8 Easy to preserve equipment
Aethetics 7 Looks professional
Educational 5 Includes educational piece for community/CCAT demonstration house
Reproducibility 5 Can be reproduced by local builders

Costs

The following table displays the costs for the Green Shed Solar Lighting project. Equipment is purchased after testing so costs may fluctuate.

Proposed budget.

Quantity Material Source Cost ($) Total ($)
6 DC Lights Bulbs Amazon $15.99/2 $47.97
3 Leviton Medium Base Turn Knob Socket Interior Ace Hardware $4.49 $13.47
3 Leviton Ivory Twin Light Socket Adapter Interstate Battery $4.99 $14.97
1 12 feet Southwire 14YEL-SOLX500 Solid Copper THHN: Solid black and solid white, 10 Gauge Ace Hardware $0.79/ft $9.78
Total Cost $86.19

Rough Timeline

Objectives Relative Week
Group forms Week 1 Jan 19th
Research literature and prepare criteria Week 3 Feb 2nd
Go to CCAT and evaluate project Week 4 Feb 9th
Perform a Solar Pathfinder Analysis(best location Study) Week 5 Feb 16th
Create temporary timeline and budget Week 6 Feb 23rd
Identify best location and test battery, lights, system efficiency with tools(multimeter), consult with CCAT on data logging and order Raspberry PI data logger Week 7 Mar 3rd
Review and identify issue 1. If lights: order new efficient lights 2. If location: order equipment needed to move to new location 3. If battery: unknown Week 8 Mar 9th
If new equipment arrives, install and test Week 10 Mar 23rd
If new equipment arrives, install and test Week 11 Mar 30th
Install Raspberry PI and motion sensor CCAT decided this was not necessary at this time Week 12 Apr 6th
Test system with data logger in best location and evaluate CCAT decided data logger was not necessary at this time Week 13 Apr 13th
Write up review and handbook for operating the system- including data logger and motion sensor Week 14 Apr 20th
Final evaluation of system Week 15 Apr 27
Final Report and Appropedia page complete Week 16 May 4th

Literature Review

This is a summation of the literature reviewed to work on the lighting system for the CCAT Green-shed January-May, 2015.

Photovoltaic Systems Overview

The photovoltaic (PV) system converts solar radiation into thermal energy and direct electrical current (DC). The direct current (DC) can be converted to alternate current (AC) through an inverter. [1] A single cell of the PV system module consists of two thin silicon wafers enhanced with other elements that produce a surplus of electrons and when the sunlight strikes this layer of surplus electrons, some release and make their way to the metallic conductors on the silicon surface of the cell, to then flow in the circuit and is pumped out. A module is a group of cells arranged in series and parallel to provide the voltage and amperage output required. A PV system is a stationary system so they are nearly maintenance free, except for any washing needed, which should be done in the morning or evening due to thermal shock breaking the glass.***

Energy, Electricity, & Circuits

"OHM's LAW: Voltage (electrical pressure) pushes amperage (current) through a resistance" [2]

Equation: V=IR

V (voltage, sometimes written as E, measured in volts), I (current, measured in amps), R (resistance, measured in ohms) [3]

Off Grid Power

CCAT’s photovoltaic system is classified as a stand-alone system. This system connects the battery to the modules through a charge controller. This controller switches off the PV array when the battery is fully charged. This battery must be large enough to store enough charge for night use, when the lights are necessary. There is no back-up supply or main grid connection. [4]

Orientation and Location of Panel

Power output by the module will change based on the angle of sunlight striking the module. [5] The output will rise as sunlight striking angle increases until the sun reaches its peak, then decreases as the sun goes down and the angle decreases once again. All modules will catch the maximum sunlight if oriented correctly, thus, in the winter, angle it to your latitude plus 23 degrees (precessional angle of the sun), while in the summer, the angle should include your latitude minus 23 degrees.****

Batteries

Batteries provide storage of energy beyond household needs, until charging sources can no longer provide energy to household. Once they are full, no more energy will flow in because batteries are finite in capacity. Safety devices, such as fuses, should be used between the power source and the system because they help prevent overheating from excess energy flow from the batteries and burning a home down.***

Inverters

Batteries release DC electricity, because AC cannot be stored. However, AC is more easily transmitted and is used by the world's power grids. Inverters help invert the DC to AC which is a more beneficial source of electricity. AC lights are mass-produced, which means they are cheaper and more available at a higher quality and selection than DC appliances. AC also allows for more conventional techniques as more lighting is easier and cheaper to install for a full-home system. However, with our simple circuit, DC is more reasonable as is it low power and off-grid.***

PV Controllers

Controllers stop the charging process of the battery when it is at full capacity because the battery can experience damage or be destroyed if overcharged too often. Controllers meter in the energy more slowly as the battery approaches 100% full capacity. They also prevent the reverse current flow that occurs with PV modules over night.***

Monitors

A monitor manages the system's state of charge and its state of charge.

Factors Affecting Output

Standard test conditions: Industry conditions under which a solar panel is tested and a production tolerance of +/-5%, meaning that the total wattage expressed is 95 Watts/ 100 Watt module. [5]

Temperature: Module output power reduces as modular temperature increases, while they increase power output at colder temperatures. [5]

Dirt and dust: Accumulation of the substances blocks sunlight, which reduces the final output.

Wiring and mismatch: Inconsistencies in performance from one module to another results in a 2% loss in the system’s power.

DC to AC conversion loss: The DC power generated by the photovoltaic system loses power during the conversion process.

Weather/Climate: The panels need solar radiation to produce energy, shade (by objects or clouds) decreases output [6]

Operation

This is the how to section explaining how and when to maintain the new system in the greenshed with the new added features.

Maintenance

The system needs to be properly maintained in order to run properly and at full power. For full detail on the past full maintenance of the PV system project, refer to http://www.appropedia.org/CCAT_greenshed_solar_lighting#Maintenance_and_Next_steps.

Schedule

Yearly
  • Perform checks on the SunSaver
  • Test voltage/amperes in full sun
  • Check all terminals and wires for loose, broken, corroded or burnt connections or components
Monthly
  • Clear PV panel on roof of any debris

Instructions

General maintenance includes:

  • The PV panel tasks and signs of damage

-Should a problem with the lighting come up, the wiring can easily be checked via the box on the underside of the solar panel.

  • The yearly SunSaver-10 PV controller tasks
  • Any battery testing and replacement
  • Light failure dimming analysis and testing

New maintenance tasks include:

  • Continuing general maintenance listed above
  • Monitor the new LED DC lights for dimming and failure
  -If failure, examine wiring connections, battery load and/or solar panel input
  -If dimming, test socket load output.
-Socket Output Load Testing-
File:
How to Test a Socket Output Load

Read more at: 1. http://www.ehow.com/how_7882922_use-multimeter-test-light-fixtures.html 2. http://www.instructables.com/id/EVERYONE-Needs-a-Multi-Meter/step5/Light-bulbs/

Conclusion

Testing

The system requires each feature functioning to run, so we tested every feature that may be the cause of the lights running dim. We tested the battery load, the lights in the system at the start, and the position of the solar panel.

Processes

Battery Load Test: The battery load test was necessary to confirm the battery was still providing it's full capacity. A battery load test involves initially covering the panel to stop anymore load input after at least 12 hours of solar charging. Then run the system lights until the battery load is run dry by the output lighting source. This will provide the total hours needed to drain the total energy supplied by the battery. This number can be used with the total given voltage and amp-hours for the battery (12V x 12 Ah = 144 Wh).

Light Power Test: Although CCAT requested for lighting through sockets, we tested the replaced hard-wired lights to show that they still produced their full power output. This testing was done with the help of the Humboldt State Physics lab staff and equipment. Professors Terry Halmo and Tyler Hooker tested that the lights could produce more Wattage (5 V x 0.3 A = 1.5W) than what they were producing in the greenshed through the PV system (2.8 V x 1.2 A = 3.36 W). These results were found through cutting down a light and testing the circuit through its open wires exposed. We have installed DC lights that function at 5 W.

Solar Pathfinder:

Location of Sunlight throughout a day: This test involved showing up hourly, and recording the location of the sunlight along the roof to show which location received the most solar insolation. The following figures are based on the sunrise-sunset period of May 1, 2015. All pictures taken earlier than 10 AM showed similar solar insolation to that of 10 AM. The sunset to sunrise period is 6 AM to 8 PM.


10:00

13:00

15:00

17:00

19:00

Results

Battery Load Test:

Light Power Test:

The hardwired lights were able to produce up to 5 volts/ 0.3 amps. This test was performed under conditions in the Humboldt State University Physics lab using a dummy load test machine (meter).

Solar Pathfinder:

This test provided the results needed to identify whether the solar panel should be moved to the most North location on the roof of the greenshed for more sun hours. The following image shows the diagram reading taken from the south end of the roof (green marking line), and the north end (red marking line). Due to tree blockage, the sun does not hit the panel until the afternoon each day (south end).

South End of Roof

Total Solar Radiation =

North End of Roof

Total Solar Radiation =

Discussion

Next Step

Team

References

Template:Reflist

  1. Tiwari, G. N.(2006). Solar Energy Technology Advances. New York: New York.
  2. Sullivan, Daniel (2011). "What are VOLTs, OHMs & AMPs?" Youtube, <https://www.youtube.com/watch?v=zYS9kdS56l8> (Feb. 2, 2015).
  3. Turner, R.P.(1978).Solar Cells and Photocells, Indianapolis, Indiana.
  4. Reddy, P. Jayarama.(2010). Science Technology of Photovoltaics. 2nd ed. Hyderabad, India.
  5. 5.0 5.1 5.2 (2001)."A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INSTALLATION".Energy Council of Canada <http://www.energy.ca.gov/reports/2001-09-04_500-01-020.PDF>.(Feb. 9,2015)
  6. Solar Energy International (2004).Photovoltaics: Design and Installation Manual, Gabriola Island, British Columbia.
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