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North Campus Photovoltaic Project Engineering Technologies Department Logan Dykes ET 494 – Senior ProjectInstructor: Dr. Cris KoutsougerasAdvisor: Dr. Rana MitraAdvisor: Mr. Byron PattersonTable of ContentsAbstract……………………………………………………………………………….3Project Development…….……………………………………………………………4Accomplishments & Future Goals……….…………………………………………...9References……………………………………………………………………………10Appendix 1 – Shading Information…………………………………………………..11Appendix 2 – LG 300W Specification Sheet………………………………………...30Appendix 3 – Fronius Primo 5.0-1 Specification Sheet……………………………..33Appendix 4 – NEC Tables…………………………………………………………...35Appendix 5 – Cost Analysis…………………………………………………………37Appendix 6 – Formulas………………………………………………………………38Appendix 7 – Diagrams and Details………………………………………………....41AbstractThis report serves to focus on the progression of the north campus photovoltaic (PV) array project. The PV array will supplement power at the Controller’s Office on north campus via a 5 kW producing system. This report will include developments and alterations of the project since the proposal stage. The location of the site is the main change to the original plan.Project DevelopmentThe north campus PV array project was initially proposed in early September with the hopes it would be a one semester project. The project will be completed by the end of the proposed deadline. The progress made includes site measurements, shading calculations, panel selection, system sizing, wire size calculations, and a suitable support structure was found. The only alteration to the project was the relocation of the system’s site. The first hurdle of the project was to determine where on the site that the least shading occurs. This was done using surveying processes. The area of the awning, the length of the Controller’s Office, the distance of the surrounding trees, and their heights were measured. The heights of the trees were determined using trigonometry. The measurements were taken a known distance from the tree and determined the angle between the ground and the gaze of the observer while looking at the tip of the tree. The distance from the tree was multiplied by the tangent of the angle between the ground and observer’s gaze. The distance from the ground to the observer’s eyes was added to the product to determine the height of the trees. There are seven trees in the area that affected different regions of the awning. A grid of the area was created to make it simpler to reference points in the area.A spreadsheet was created and used to calculate the elevation and azimuth angles for all potential obstructions along evenly spaced points on the awning. The distance between the point on the awning and the potential obstruction was calculated with Pythagorean Theorem. The elevation angle of the potential obstruction was calculated by finding the tangent of the height of the obstruction divided by the distance between the points. The azimuth of each potential obstruction was calculated by finding the tangent of the distance in the x direction divided by the distance in the y direction. X direction is the west to east plane. Y direction is the north to south plane.Next, the elevation and azimuth angles of all potential obstructions were transferred onto a sun path diagram retrieved from the University of Oregon. A sun path diagram for each point of interest on the awning was created. This allowed a transform into meaningful information. After analyzing every sun path diagram, it was found that there would be a substantial degree of shading along the entire awning. There was a 400 square foot region of the awning that would have been viable if we two trees could have been cut down. There was a conversation with Mr. Patterson about this idea and he noted it was against the university’s wishes to cut down trees. The second option was that the location of the site should be moved. He agreed that moving the system to the roof of the Controller’s Office would be in the best way to make this project succeed. By the time this was discovered it was too late in the project to recreate a sun path diagram for the new area. The upside to this was that the new area was unlikely to be obstructed by the surrounding trees. With permission from Dr. Koutsougeras and agreement with Mr. Patterson the project on the new area was in procession. The next step was to select a panel to use for the system and to the size of the system in regard to the selected panel. After comparing numerous photovoltaic cells and their specification sheets, the LG 300S1C-A5 Black MonoX Plus was determined to be the best candidate for this project. It boasts a 17.5% efficiency rating and has a competitive cost per watt produced. It was time to refer to the specification sheet to determine how many panels to use. In Appendix 2, the following values are found: voltages, currents, and temperature characteristics. In Appendix 3, the inverter’s specifications are listed. These values were used to determine the minimum and maximum panel parameters and sizing the conductors. The max number of panels allowed was determined by dividing the 660V nominal voltage input of the inverter by the maximum voltage max power point of 39.7 V. The max system voltage can be determined by multiplying the quotient by 39.7 V. This gives a maximum allotted panel usage of 16 panels. The bottom MPPT range of the Fronius Primo 5.0-1 is 240 V. The temperature characteristics of the LG 300 stated that the voltage is decreased by 0.1167 V/?C. The difference between the rated temperature and the highest recorded ambient temperature for the region was used to determine the decrease in voltage. This difference was 4.4 V. We can find the minimum number of panels needed by dividing this bottom MPPT range by 27.2 V (31.6 V – 4.4 V). The minimum number of panels that can be used is nine. The correct wire size needed to be determined to run the produced power properly. The short circuit current of the LG 300 was multiplied twice by the safety factor of 1.25 outlined in NEC 705.12. This resulted in the required conductor ampacity of each string to be 15.734 A. The max current output of the inverter was determined using the same method minus one safety factor multiplication. The required ampacity for the conductors after the inverter was found to be 29.625 A. These values were adjusted using the adjusted ampacity for temperature and conduit running 0-1/2” above the roof. The results showed that a minimum of #10 AWG wire to be used before the inverter and a minimum of #6 AWG wire to be used after the inverter.Support StructureTo begin the design of the support structure the minimum spacing of the panels needed to be calculated so the panels in the front row would not shade the ones behind it. There were four calculations that gave the row width. The formula to find the row spacing is D'=htanα, where D’ is the row spacing, h is the height of the tilted panel, and α is the angle of the sun’s elevation to the bottom of the second panel. The elevation angle was found using the NOAA Solar Position Calculator, found in Appendix 1. Next the height of the tilted angle was needed. This was found by multiplying the height of the panel by the cosine of the tilt angle. The easiest way to optimize the system by tilt angle was to average it out for the year so it would always collect efficiently since it is a fixed array. This was done by multiplying the latitude of the location by 0.76 and then adding 3.1 ? (Optimum Tilt of Solar Panels). The optimal angle needed for the fixed array system is 26 ?. Solving for row spacing, D', yields 36.895” or 3.07’. The minimum row spacing can be found using D=D'?cos180-Ψ, where Ψ is the azimuth angle found using the NOAA Solar Position Calculator, found in Appendix 1. The minimum row spacing, D, was found to be 28.83” or 2.4’. The total width of the row was found by adding D and cosine of the tilt angle multiplied by the height of the panel. The width of each row is 64.78” or 5.4’. The LG 300 is a tall panel; to work with most supports, it will have to be laid on its side. ?The best support structure for this application was found to be Renology?RNG-MTS-TM100. It is a flat roof mounting system that utilizes an extension bracket. A modular setup such as this is preferred because it is required to meet building codes. The area for the roof was calculated and the layout is two rows of 11 panels with a total distance of 62.3' with the panels mounted on their side with spacing for bracket inserts. The tilt angle these can achieve is about 22 ?. These will be mounted on a flat roof and flat roofs typically have a tilt of 3? or 5?. This should get us about 25? to 27?. If the tilt of the roof is working against the array, small modifications with spacers can be made to offset the difference. Cost AnalysisThe allotted budget for the project was $22,000. Due to Mr. Patterson’s efforts, this budget was supplied by grant money. The only parts left to order are the 4x4 pieces of pressure-treated wood and stainless-steel lag bolts for support. Duralast bonding contractors will need to be contracted out to provide adhesive-laying services for the structure. With a grand total of $13,577.65, the average kWh saved per month is 580.83. This is done by multiplying a 5 kW system by the 82% efficient 1700 from the shaded region map divided by 12. The efficiency is determined by the efficiency ratings of the PV cells and inverter and power losses along wires (Hahn, Dan). This gives a monthly saving of $69.70 at average of $0.12 per kilowatt. If this number is multiplied by 12 and then 20, the total savings over a 20-year period is $16,728. Over an average span of 20 years the system it will save the school $3,150.35. The system may last longer than 20 years, but a more efficient panel will be available by the time repairs are needed. The manufacturer’s warranty was another reason why the LG 300 panel was chosen to be the production cell.AccomplishmentsInitial Proposal and PresentationWritten proposal for review and approvalPowerPoint presentation designed and submitted for approvalOptimum Placement of PV Cells on Awning Measure building dimensions that could affect shadingEvaluate angles of elevation and azimuthAddress shading concerns for the areaMaximum versus efficient panel placementSize the PV SystemWork around Mr. Patterson’s preferencesStart with his inverter, then PV cells, then sizing wire, etc.Create Support StructureDesign with tilt of panels in mindPerform stress analysis on structureMounting considerationsList All Parts Necessary for ProjectSpreadsheet with quantity and price of equipment/hardwareMaximizing benefits within the budgetDesigned a Plan to InstallSchematics and diagrams of systemWorks CitedSimpson, Jeff. (2014, August 22). 2014 NEC 705.12(D)(2) – Understanding PV Interconnections. Retrieved from , Charles R. (2015, November 11). Optimal Tilt of Solar Panels. Retrieved from Hahn, Dan. (2012, June 5). How to Calculate the Amount of Kilowatt Hours (kWh) Your Solar Panel System Will Produce. Retrieved from Solar. Calculating Tilted Array Spacing. Retrieved from Choice Staff. (2017 February 6). Sizing Inverters to Optimize Solar Panel System Efficiency. Retrieved from Solar Planner. (2013). Optimum Solar PV Array Placement. Retrieved from The Solar Planner. (2013). Optimum Array Orientation & Placement. Retrieved from Oceanic and Atmospheric Administration. NOAA Solar Position Calculator. Retrieved from Electric Co. NEC Table 310.15. Retrieved from NEC Code Reference 310.15(B)(3)(C). (2012, January 15). Retrieved frompowerdesigninc.us/best-practices/2011-NEC-Code-310.15B3c.doAppendix 1Appendix 2Appendix 3Appendix 4Appendix 6Appendix 7Appendix 8Panel Layout ................
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