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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

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 can be converted to alternate current (ac) through an inverter. [3}

Energy, Electricity, & Circuits

"OHM's LAW: Voltage (electrical pressure) pushes amperage (current) through a resistance" [1]

Equation: V=IR

V (voltage, sometimes written as E, measured in volts), I (current, measured in amps), R (resistance, measured in ohms) [2]

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. [2]

Orientation and Location of Panel

Power output by the module will change based on the angle of sunlight striking the module. [1] 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.

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. [3]

Temperature: Module output power reduces as modular temperature increases. [3]

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 [4]

References

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[1] Arthur unkown. "A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INSTALLATION." Http://www.energy.ca.gov/reports/2001-09-04_500-01-020.PDF. June 14, 2001. Accessed February 9, 2015. http://www.energy.ca.gov/reports/2001-09-04_500-01-020.PDF.

[2] Reddy, P. Jayarama. Science Technology of Photovoltaics. 2nd ed. Hyderabad [India: BS Publications, 2010.

[3] Tiwari, G. N. Solar Energy Technology Advances. New York: Nova Science Publishers, 2006.

  1. Sullivan, Daniel (2011). "What are VOLTs, OHMs & AMPs?" Youtube, <https://www.youtube.com/watch?v=zYS9kdS56l8> (Feb. 2, 2015).
  2. Turner, R.P.(1978).Solar Cells and Photocells, Indianapolis, Indiana.
  3. 3.0 3.1 (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)
  4. Solar Energy International (2004).Photovoltaics: Design and Installation Manual, Gabriola Island, British Columbia.
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