UNLV Theses, Dissertations, Professional Papers, and Capstones August 2019 Investigation of Efficiency Loss of Distributed Solarower P Due to Soiling and Efficiency Recovery by Rainfall Amanda Mayumi Tanaka Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Environmental Engineering Commons Repository Citation Tanaka, Amanda Mayumi, "Investigation of Efficiency Loss of Distributed Solarower P Due to Soiling and Efficiency Recovery by Rainfall" (2019). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3750. http://dx.doi.org/10.34917/16076293 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INVESTIGATION OF EFFICIENCY LOSS OF DISTRIBUTED SOLAR POWER DUE TO SOILING AND EFFICIENCY RECOVERY BY RAINFALL By Amanda Mayumi Tanaka Bachelor of Science in Environmental Chemistry Universidade de Sao Paulo, USP 2015 A thesis submitted in partial fulfillment of the requirements for the Master of Science in Engineering - Civil and Environmental Engineering Department of Civil and Environmental Engineering and Construction Howard R. Hughes College of Engineering The Graduate College University of Nevada, Las Vegas August 2019 Copyright 2019 by Amanda Mayumi Tanaka All Rights Reserved Thesis Approval The Graduate College The University of Nevada, Las Vegas May 17, 2019 This thesis prepared by Amanda Mayumi Tanaka entitled Investigation of Efficiency Loss of Distributed Solar Power Due To Soiling and Efficiency Recovery by Rainfall is approved in partial fulfillment of the requirements for the degree of Master of Science in Engineering - Civil and Environmental Engineering Department of Civil and Environmental Engineering and Construction Jacimaria Batista, Ph.D. Kathryn Hausbeck Korgan, Ph.D. Examination Committee Chair Graduate College Dean David James, Ph.D. Examination Committee Member Sajjad Ahmad, Ph.D. Examination Committee Member Monika Neda, Ph.D. Examination Committee Member Shubhra Bansal, Ph.D. Graduate College Faculty Representative ii Abstract As the concern with global warming increases causing the need for CO2 reduction, renewable energy is of great interest as it has lower carbon footprint when compared to conventional sources (natural gas, coal, oil and nuclear). Solar energy has been drawing worldwide attention since it can transform sunlight directly into electricity with the use of photovoltaic (PV) cells. However, this technology has some drawbacks that need to be addressed including dust deposition on solar panels, also known as soiling. Soiling can decrease PV panel’s efficiency thereby resulting in less energy production. The soiling rates are very site specific and depend on the geographic location of the panels and the climate in that area. The solar panels can be cleaned naturally (by rainfall, snow or wind) or mechanically washed. This thesis addresses the impact of solar panel soiling and washing on the energy production of solar PV plants located at the UNLV campus. The objectives of this project were (a) to evaluate whether rainfall alone, in the desert environment with low rainfall, is sufficient to clean up the solar panels, and, if possible, determine the minimum amount of rainfall necessary to clean up panels.; (b) to examine the efficiency loss caused by soiling using different methods of analyses and (c) to evaluate if panel washing is worthwhile given the cost and the efficiency gain that is obtained by washing. To calculate the efficiency of the panels, a model was developed to generate parameters that were not measured at the site. Panel efficiencies before and after rainfall events were compared to determine the minimum amount of rain necessary to clean the panels. It was found that at least 0.2 inches of rain was needed to partially restore clean-panel efficiency. In Las Vegas, the recurrence periods of different depths rainfall were calculated using data from the past 29 years. iii It was observed that the 50th percentile recurrence period of a rainfall event with depth of 0.2 inches or higher was approximately 52 days. Student Union: -0.0044%/day, CBC-C: -0.00099%/day, and Dayton Hall: -0.0034%/day The amount of efficiency lost during the dry intervals (periods between rainfall events) was analyzed in three different ways. The average efficiency loss per day during the dry periods varied from -0.000171 % to -0.00533 %, depending on the method used and the building where the panels were located. However, there were some limitations to the calculations. It was not possible to completely isolate the effects of only soiling on the efficiency of the panels. The rate of decline seemed to be also impacted by seasonal effects. To better evaluate the effect of washing, a professional company was hired to wash a set of solar panels located on UNLV’s Student Union building. The panels were washed with water with a low concentration of TDS. The power output and the efficiency of those panels were analyzed from before and after the washing. There was a very small efficiency and power increase due to the washing. Therefore, it was concluded that washing in this area is not worthwhile, and that rainfall events in excess of 0.2 inches can adequately restore the efficiency of the panels. If there is a change in cost of energy, washing, water or a great increase in the efficiency of the solar panels, it would be necessary to reevaluate the analysis. iv Acknowledgements First of all, I would like to thank God. He has given me strength, support, courage and faith so I could keep going during the hardest moments. He also provided me a supporting family and friends during this journey. He has been so good to me and has given me so many opportunities and I could not be more thankful for that. Secondly, I would like to thank my parents, Marisa Baldi and Nelson Tanaka, for believing in me and supporting me financially and, most importantly, emotionally; not only throughout this process, but during my whole life. They are the best parents I could have asked for and without them I would not have achieved half as much as I have. I thank my brother, Thiago Tanaka, for all the love and fun he has always brought into my life and being there when I need him. I would like to thank Dr. Batista for giving me this opportunity and helping me since when I started applying to UNLV throughout my whole time here. I thank her for providing me funding for the master’s degree and guiding me in my research. I want to thank my committee, Dr. Neda, Dr. Ahmad, Dr. James and Dr. Bansal, for their time and help reviewing my work and valuable insights. I would like to thank Dr. Neda for all the assistance she gave me with the results and statistics calculations. I would like to specially thank Mark Elkouz for being a supporting boyfriend, spending late nights with me in the lab, proof-reading my e-mails and parts of my thesis, encouraging me to work when I was not motivated, listening to my complaints and for his companionship. It was a tough couple of years, but I could not imagine how much harder it would have been if he was not there for me. v I want to thank my family and friends in Brazil for all their support and my friends Ana, Alisson, Fernanda, May and Mayra for being there for me when I needed, always motivating me and sharing with me this experience. Also, thanks to Vivi for being a good friend and supporting me. I would also like to thank the Elkouz/Karacsonyi family: Jacquie, Elie, Sandra, Natalie, Joe, Noelle and baby Elias for welcoming me into their family and making me feel like home even when I am thousands of miles away from Brazil. Special thanks to my Kansas family, Rhonda, Dewayne, Kaylee and Kelsey for being the best host family I could have ever imagined and always being there for me. I would also like to thank everyone that helped me in this research and made it possible for this thesis to come together. Special thanks to Aaron Sahm for the help with all my calculations and the inputs in my results. Thanks to Mr. Whinery, Mr. McMath, Chad, Mr. Henson for giving me access to the data and to the solar panels at UNLV. I would also like to thank everyone that helped me in the solar panel survey and shared their knowledge with me. I wanted to thank my colleagues from WSP for being very supportive and especially my supervisor, Joanna Opeña, for being very understanding, believing in me, and teaching me so much every day. This research was only possible due to the financial funding provided by the National Science Foundation under Grant No. IIA-1301726. I would like to thank and acknowledge NSF for this opportunity. vi Table of Contents Chapter 1 – Introduction and Objectives ................................................................................... 1 Chapter 2 - Literature Review ..................................................................................................... 7 2.1. Sustainable Energy................................................................................................................... 7 2.2. Classification of Energy Generating Systems.......................................................................... 9 2.2.1. Centralized Generation (CG) ........................................................................................ 9 2.2.2. Distributed Generation (DG) ...................................................................................... 10 2.3. Components and Performance of Photovoltaic Solar Cells ................................................... 13 2.4.