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Project Background

CCAT (Campus Center for Appropriate Technology) currently operates a work shop known as the greenshed, which is currently being allocated as a space to design, build, and maintain appropriate technology projects. The greenshed is located on the same property as the live-in CCAT center. This close proximity is very convenient, but it is being hindered by a lack of grid connected power. The greenshed is in need of a light source which is independent of the power grid.

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Shed Background

The CCAT green shed is approximately 18 ft x 10 ft with 180ft2 of floor space. It was constructed several years ago by a group of students.

Environmental Factors

Located in Arcata, California, the site of the green shed has a variable amount of solar irradience, using the PVWATTS v.1 solar irradiance calculator it was determined that Arcata receives a yearly average of 4.48 hours of full sun a day. [1]

Problem statement

The objective of this project is to design and build a small solar array to light the green shed at CCAT. The greenshed was built in such a way that it would not need lighting during the day, but work is halted as the sun sets. This lighting project will provide enough light for CCAT volunteers to return tools to their proper location and clean up the shed after a day of work. In addition to functionality our system will be used to show how small scale solar can be utilized to solve real world problems. This aligns with the demonstration goals of CCAT.

Project Evaluation Criteria

The following criteria will be used to assess the success of this project. These criteria were chosen based on the suggestions of the project coordinator as well as the diligent students who are working on the lighting system. The scale (1-10) represents the importance level of meeting the constraint of each listed criteria.

Criteria Constraints Weight
(1-10)
Maintainability Must be easy to clean and maintain the solar array. No more than 2 hours maintenance per month.
6
Aesthetics Must be pleasing to the eye and look professional.
8
Educational Aspect Must include an educational piece for community.
4
Safety & Placement Must be safe for use by CCAT staff and volunteers, must not interfere with work being done.
10
Reproducibility The structure could be reproduced by local builders.
5
Usability Must sufficiently light tool shed.
9
Budget Must not exceed budget of $400.
10
Functionality Successfully produces and stores energy for use in shed.
10
Lifetime Must be usable for at least 5 years.
8

Tentative Time Line

Project Started Completion
Calculate net sun for selected locations and determine collection panel placement. February 20 February 22
Determine shed size. February 21 February 21
Using shed size determine desired lighting needs, price, and order lights. February 21 February 22
Determine max kWh the system can generate using panel size and calculated solar exposure. February 22 March 22
Using calculated system generation capacity, desired lighting time, and project budget, determine battery bank size. February 23 March 1
Price the rest of the system including mounts, wiring, switches, and necessary conduit. March 1 March 8
Order remaining system components. March 9 March 16
Install photovoltaic array. April 7 April 12
Link array to chosen light source. April 10 April 16
Test system to ensure proper working of all components. April 22 May 3

Costs

The following table displays the costs for the Green Shed Solar Lighting project. Funding of this project was provided by CCAT. The 100 Watt panels were donated by Scurfield Solar in Arcata, California, which lowered the cost of this project significantly. In addition to the panel, lights were donated from a campus organization.

Quantity Material Source Cost ($) Total ($)
4 Mounting Clamps Online 15.00 60.00
3 Light Bulbs Arcata Recycling Center - The Reusables Depot Thrift Store donated donated
1 Voltage Controller http://www.savegreenmoney.com/product-p/020-01233.htm 60.80 60.80
1 Southwire 14YEL-SOLX500 Solid Copper THHN, 10 Gauge Online 54.00 54.00
1 12V 12 Ah Battery 60.00 60.00
1 25ft flexible conduit 26.35 26.35
1 100 Watt Solar Panel donated donated
1 Rubber Boot 24.00 24.00
3 Fixtures Online donated donated
Total Cost $315.15

Project Design and planning

Analysis of Solar Insolation

Arcata Insolation Values

Solar Pathfinding

Components of System

Voltage Controller

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Battery

Lights

Mounting

We needed to find a way to mount our panel on the roof of the shed and to wire it into the interior of the shed without damaging the roof=== 

Clamp.jpg
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===

Conduit and Wire

Installation

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Literature Review

The following is a concise synopsis of relevant literature reviewed for the comprehensive green shed lighting project at CCAT.

Solar basics

Solar energy can be converted into electricity by photovoltaic panels. This electricity can then be used to power a plethora of devices. Photovoltaics, among other uses, can be used to deliver power to buildings that are not connected to the standard electricity grid. We chose an off grid solar design to exemplify a small scale, self sustainable system which can provide light for various uses in the green shed. [2]

Applications of off grid solar

The lighting project for the green shed will demonstrate the manageability of a small off grid solar system. More than one in five people in the world live without electricity, off grid solar systems are an option that can be quickly installed in these areas and provide a base level of electricity. Currently, people without electrical lighting mainly use kerosene lighting which is expensive and when used inside for long periods of time has adverse health effects including from the inhalation of toxins and fire risk. [3] [4]

Calculating Possible Solar Power

In order to calculate the power output of a solar system you need to know the amount of full sun hours received by your site, this value will vary over the course of a year but can be averaged. There are online calculators which are able to estimate this solar irradience value. After determining this value a solar path finder can be used to identify the most appropriate location on your site to place your panels.

(Insert image of excel sheet)

Lighting options

There are many different lighting options that will need to be analyzed. These include a comparison of DC and AC lighting, incandescent, CFL, and LED bulbs. There is a range of criteria that these alternatives will be rated with that includes wattage, lifetime, and cost.

Calculating illumination needs

Calculating Illumination

Illumination can be calculated as

I = Ll Cu LLF / Al (1)

where

I = illumination (lux, lumen/m2)

Ll = lumens per lamp (lumen)

Cu = coefficient of utilation

LLF = light loss factor

Al = area per lamp (m2)

[5]

Calculating Battery Size

(insert battery sizing table)

Energy Efficiency

Efficiency will be of great importance to this project for many reasons. These reason include the a reduced total system size, reduced carbon intensity of the system, and decreased system cost. Some efficiency measures such as LED lighting instead of CFL lighting may have a higher upfront cost , but this additional cost should be offset by their lower life cycle energy usage.[6]

Return On Investment

Because the energy generated by this system will offset energy that would otherwise have to be purchased by a grid provider, in this case PG&E, this system will generate revenue in the form of offset electricity cost. This offset electricity cost will help to recover the upfront cost of the system. The value of this energy offset can be calculated and compared to the upfront cost of the system to determine financially feasible project options.[7]

National Electric Code

Although it may not be of importance for this project to meet national electric code, the same standards will be used as a measure of quality assurance. The goal of these standards are to promote safe, reliable, and consistent results from photo-voltaic power systems. [8]

Alternatives

Using the sun’s energy to illuminate the green shed is one of the many options available in terms of renewable energy. Similar projects could be achieved by taking advantage of other available resources such as wind, micro hydro, or geothermal. Wave or tidal energy could potentially be harnessed as well, given that the location was close enough to the ocean. Solar is most preferred in this case because of the availability of donated panels as well as simple installation and maintenance. [9]

Off Grid Power

This photovoltaic system will exemplify the benefits of off grid power. Relief from rising electricity prices will be a benefit. Additionally, trends indicate that the current reliance on petroleum will cause future price increases. Off grid power offers security from these potential downfalls.[10][11]


Maintenance and Possible Future Plans

The solar system installed in the CCAT green shed will require minimal maintenance over the course of its lifetime. The photovoltaic panel on the roof should be cleaned on a monthly basis to ensure that the solar energy falling on it is not being blocked by dust or other debris. Should a problem with the lighting arise, the wiring can easily be checked via an access box on the underside of the solar panel. The battery for this system is located inside the greenshed, and has been placed in a plastic storage box to prevent foreign objects coming in contact with the battery terminals. This box is easily accessible, and can be opened in order to check on the wiring within. If any of the actual lights dim or go out completely, they can easily be removed and replaced with another identical light, which are currently at CCAT.

There are several potential future additions which may be of interest to future students. A motion sensor could be installed for convenience, as well as ensuring that the lights turn off by themselves in case they are left on by accident. A USB charger could also be put in place. It would draw power from the battery, and could charge devices such as cell phones, small lights, cameras, etc.

References

  1. http://www.nrel.gov/rredc/pvwatts/site_specific.html
  2. Boxwell, Michael. 2010. Solar electricity handbook: a simple, practical guide to solar energy : designing and installing photovoltaic solar electric systems. Ryton on Dunsmore, Warwickshire, U.K.: Greenstream Pub.
  3. Bank, World. 2008. The Welfare Impact of Rural Electrification a Reassessment of the Costs and Benefits. Washington: World Bank. http://public.eblib.com/EBLPublic/PublicView.do?ptiID=459798.
  4. Njeri Wamukonya, Solar home system electrification as a viable technology option for Africa's development, Energy Policy, Volume 35, Issue 1, January 2007, Pages 6-14, ISSN 0301-4215, 10.1016/j.enpol.2005.08.019. (http://www.sciencedirect.com/science/article/pii/S0301421505002235)
  5. http://www.engineeringtoolbox.com/light-level-rooms-d_708.html
  6. Craig B. Smith, “Electrical Energy Management in Buildings,” in CRC Handbook of Energy Efficiency, ed. Frank Kreith et al. (Boca Raton: CRC Press, inc., 1997), 305.
  7. J. Kelleher and J.V. Ringwood, “A computational tool for evaluating the economics of solar and wind microgeneration of electricity,” Energy 34 (2009): 401, Accessed February 13,2013, doi:http://dx.doi.org/10.1016/j.energy.2008.10.009
  8. John Schaeffer, Solar Living Source Book: The Complete Guide To Renewable Energy Technologies & Sustainable Living (White River Junction: Chelsea Green Publishing Company, 2001), 504–505.
  9. Boyle, Godfrey. Renewable energy: power for a sustainable future. Oxford, England: Oxford University Press in association with the Open University, 1996.
  10. Boyle, Godfrey. Renewable energy: power for a sustainable future. Oxford, England: Oxford University Press in association with the Open University, 1996.
  11. Blackburn, John O.. The renewable energy alternative: how the United States and the world can prosper without nuclear energy or coal. Durham, N.C.: Duke University Press, 1987.
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