Applied Solar Power Research
An Analysis of the Photovoltaic Potential of WWU
Prepared by Nate White
Senior, Environmental Policy
Huxley College of the Environment
Western Washington University
Bellingham, WA
Introduction:
This paper began as a project in Huxley College’s Environmental Policy Analysis class winter quarter 2008. We were assigned to find a problem that needed to be solved using alternative solutions. The problem focused on was reducing Western’s carbon footprint by using renewable energy. My alternatives were an energy conservation policy, a renewable energy credit policy and a solar energy policy. The policy that interested me the most was the solar energy policy, and I continued research after the class was over in the form of an independent study. This report is the culmination of that work.
Background:
Currently, the U.S. meets 70% of its electricity needs through the use of fossil fuels, including petroleum, coal, and natural gas.[1] Depending on the scale of implementation, the use of renewable energy can slow, halt, or even reverse the growing trend of fossil fuel greenhouse gas emissions. Solar electric technology in particular holds much promise for replacing dirty, fossil fuel electricity with clean, renewable electricity.
Photovoltaic (PV) panels convert radiation from the sun into electricity. With proper siting, solar radiation, orientation and scale, a PV system can provide anywhere from a portion to the total electrical needs of a building. However, drawbacks do exist. Current PV technology is limited in the conversion of solar radiation to electricity, and relatively high costs discourage wide-scale implementation. Additionally, the local climate plays a large role in the productivity of a PV system. Especially in Bellingham, where the solar resource is highly seasonal, PV systems produce more electricity in the summer and less during the winter.
Despite these drawbacks, the popularity of PV technologies has spiked in recent years due to fears of climate change, increases in financial incentives and technological improvements. This paper is a result of these issues and considers whether Western can capitalize on this new wave of renewable energy opportunity.
Paper Layout:
This paper analyzes the basic considerations of installing a PV system and recommends five buildings on Western’s campus that would qualify as productive sites for a rooftop PV installation. This paper is divided into three sections:
1. A research section that briefly explains the research relevant to this project
2. A results section that analyzes the research results in terms of PV potential
3. A conclusion section that compares the best PV study site on campus to other renewable energy options that Western might pursue
At the end of the paper, I hope that anyone curious about the photovoltaic potential of Western can understand the opportunities and obstacles facing such a system. Ultimately, I envision this study as a tool for students, faculty and administrators to use to decide whether photovoltaics should be a component of Western’s commitment to effective, innovative and sustainable solutions to environmental problems.
Acknowledgements:
I would like to thank the generous support of Ron Bailey and Tim Williams at Western’s Facilities Management, Robert Foster of the Institute for Energy and the Environment at New Mexico State University, Dana Brandt at EcoTech Energy Systems LLC, and the members of the Students for Renewable Energy Solar Committee. Without the help and support of these people, this project would have been overwhelming and not nearly as much fun as it was. Because of them, I have learned an incredible amount of renewable energy knowledge that I hope to turn into a career.
Thank you for reading, and please do not hesitate to contact me for further information or questions.
Sincerely,
Nathan White
Table of Contents
Section 1: Research Areas 5
Area #1: Appropriate buildings for a PV array 5
Area #2: Availability of insolation 5
Area #3: Site area 6
Area #4: System size 6
Area #5: Conversion efficiencies 7
Area #6: Estimated power output 7
Area #7: Estimated system cost 8
Section 2: Results 9
1. Appropriate buildings for a PV array 9
2. Availability of insolation 10
3. Site area 11
4. System size 13
5. Conversion efficiencies 15
6. Estimated power output 16
7. Estimated system cost 17
Section 3: Conclusions 21
Evaluative Criteria 21
1. Promote energy self-sufficiency 21
2. Reduce the cost of electricity 24
3. Reduce greenhouse gas (GHG) emissions 27
4. Educate people about renewable energy 29
Decision Matrix 31
Other Alternatives: 32
Improved REC Policy 32
Energy Conservation Measures 34
Final comments 36
Appendix 37
Figure 1: Solar Pathfinder 37
Figure 2: Excel spreadsheet 38
Figure 3: Estimated annual insolation of other studied buildings 38
Figure 4: Average insolation values for Seattle and Bellingham 38
Figure 5: Sample floor plans 39
Figure 6: Derate calculator 45
Figure 7: Average insolation values for San Diego 46
Figure 8: Map of Western Washington University 47
References: 48
Section 1: Research Areas
The following research areas are relevant to the siting and installation of a PV system. The information and data gathered for each area is specific to the installation of a PV system at Western, and was gathered from a combination of methods. Primary measurements, industry standards and procedures, and the experience of professionals within the renewable energy and campus administration fields are all used within the report, and offer a unique perspective on the opportunities and challenges for PV systems at Western.
The following are the areas researched for this project:
1. Appropriate buildings for a PV array
2. The availability of insolation at a site
3. The geometric area of a site
4. The estimated size of a PV system at each study site
5. The conversion efficiencies of a PV system at each study site
6. The estimated power output of a PV system at each study site
7. The estimated system cost of a PV system at each study site
Each research area is an important part of determining the PV potential of a site. They relate to the availability of energy that powers a PV system, the physical footprint of such a system, and the estimated performance and cost of a system. Each area is explained in further detail below.
Area #1: Appropriate buildings for a PV array
The buildings that were used in this report were chosen by a combined method of first-hand observations of sun exposure and more sophisticated collection of insolation (solar radiation) data using a Solar Pathfinder (explained below). Buildings with exposure to the south were ideal candidates because they receive the greatest exposure to the sun as it travels east to west in the Northern Hemisphere.
Area #2: Availability of insolation
Insolation is measured in kilowatt hours per meter squared per day (kWh/m2/day). The higher the insolation, the more effectively solar panels can convert solar radiation into electricity. The average insolation received by certain cities during a thirty year period can be found using charts generated by the National Renewable Energy Laboratory (NREL). The closest chart applicable to Bellingham is Seattle’s, and because the weather patterns between the two cities are similar, the trends are used for Bellingham.[2]
To measure the insolation received by specific roofs around campus, I worked with Facilities Management employee Tim Williams to get access to the roofs of the preferred buildings. To take these measurements, I used a Solar Pathfinder. A Solar Pathfinder is a small device with a clear dome that reflects the shadows influencing a site onto a chart of the sun arcs and total sun hours of each month. By tracing the shadows and adding up the total sun hours unaffected by the shading, you can determine the percentage of the site that is shaded and how much it will interfere with the array’s exposure to the sun. This analysis will provide site-specific insolation data and ultimately indicate whether a specific site is appropriate for installation or not. See Figure 1 in the Appendix for a Solar Pathfinder diagram, picture and a sample chart.
Area #3: Site area
Measurements of the area of preferred roofs were taken using the original floor plans found in Facilities Management’s vault. Use of the original plans, combined with first-hand observations and the professional expertise of Tim Williams, allowed accurate measurements of the geometric area of specific roofs that take into account aspects of roof shape, surfaces and obstacles.
Area #4: System size
Estimates of the physical area of a PV system are made using the dimensions and power rating of an example panel, an example tilt and the measured geometric area of the preferred roofs.
The estimated panel dimensions are based on the PV panels being installed on the Viking Union roof. These panels are assumed for familiarity purposes, and because it represents an average composition, power rating and size for PV modules today.
The example tilt is 34˚ in order to maximize the collection of insolation during the summer when the sun is higher in the sky. If panels were mounted in multiple rows of single panels oriented horizontally, they would have to be spaced far enough from each other to avoid shading the row behind.
Finally, the geometric area of the roof can only fit a finite number of panels. Dividing the roof area by the area of one panel and its shadow will give the total number of panels that can fit on a given roof. Multiplying the number of panels that will fit on a given roof by their 165 Watt power rating will give the estimated system size in watts, and if you divide by 1000, kilowatts.
Area #5: Conversion efficiencies
The efficiency of a solar array is determined by multiple factors:[3]
1. The average amount of insolation a locality receives over time
2. The amount of shade blocking incoming insolation
3. The orientation of the array
4. The power rating of the PV panels
5. The individual efficiencies of the balance of system components (i.e. “parts”: invertors and transformers, wiring, and diodes and other connectors)
6. Maintenance
7. Age
Values for the categories were found using a combination of first-hand measurements, correspondence with PV professionals and industry averages. Collectively, they provide an overall value called the “Derate Factor” that is used to represent the estimated efficiency of the entire PV system. The industry average is a 77% Derate Factor, meaning that the average AC power rating of a photovoltaic system is 77% of the nameplate DC power rating after conversion.[4]
Area #6: Estimated power output
Estimates of potential power are used to forecast the productivity of a PV system into the future. They can be used to determine the percentage of a building’s energy a system can produce, how much money will be saved by avoiding paying for electricity in the short and long term, and ultimately whether a system is worth the investment. Monthly and yearly estimates of electricity production can be calculated to see the bell-shaped trend of photovoltaic electricity production in our climate, which peaks during the sunny summer months and ebbs during the rainy winter months.
Area #7: Estimated system cost
Estimates for photovoltaic systems are difficult to make because of the variable costs of modules, parts and installation, which in turn are influenced by the location and specific characteristics of a site. That being said, system costs can be based on the linear nature of some components (modules, racking and grounding) and the experience of photovoltaic professionals for variable cost components like inverters, grid interconnect, design and installation time.[5] Generally, a contemporary grid-tied PV systems cost between $8.00-10.00 per Watt, with larger systems costing less and smaller systems costing more.[6] Additionally, the cost-per kilowatt-hour can be estimated by dividing the total cost of a PV system (in cents) by its lifetime production of kilowatt-hours (a PV system lasts anywhere between thirty to fifty years).[7] Depending on the economies of scale and available incentives, electricity from modern PV systems costs anywhere from twenty one to thirty-seven cents per kilowatt-hour.[8]
Section 2: Results
The information and data gathered during the research was analyzed and tabulated in an Excel spreadsheet to graphically portray the crucial information needed to make an assessment of the photovoltaic potential of Western. See Figure 2 in the Appendix to review the tabulated results of the study. Sheet 1 contains information on physical site characteristics and output estimates for each PV site, and Sheet 2 contains estimates of the costs for each PV system.
Explanations of the analysis are listed under the individual research areas to show the specific methodology, calculations and techniques that were used to obtain the results. The example results in the paper differ slightly from the results in the spreadsheet because of differences in rounding: consult the spreadsheet for the most accurate results
1. Appropriate buildings for a PV array
Ø The buildings studied to host a PV system are listed at the top left of each data block in Sheet 1 of the spreadsheet
The five buildings chosen for study in this report are Parks Hall, Bond Hall, Wilson Library, the Performing Arts Center (PAC) and Buchanan Towers (BT). These five buildings were chosen because they range in size from large to small and have low shading interference. The lower the percentage of the site that is shaded, the more insolation it receives to convert to electricity. These buildings also have flat roofs that would allow them to easily hold a PV system. Six other buildings were measured for the affect of shading on their annual insolation estimates. They can be found in Figure 3 in the Appendix.
Additionally, the roofs of these five buildings are partially or fully hidden from view at the street level. This limited visibility satisfies an important criterion of Facilities Management relating to the aesthetics of campus architecture. Concerns were raised that any PV system on campus should be out of sight to the general public, so as to not disrupt the historic aesthetics of Western’s campus. Each of the buildings recommended in this report fully or partially satisfies that criterion, with those only partially hidden still being relatively inconspicuous.
2. Availability of insolation
Ø The raw insolation for Bellingham is listed in Sheet 1 the spreadsheet under “Raw Insolation”