An-Najah National University Faculty of Graduate Studies The Techno - Economical Impact of PV On-Grid Systems on the Security of Palestinian Electrical Supply (Jericho PV system - Case study) By Abdel Latif Wasef Abdel Latif Kharouf Supervisor Dr. Imad Ibrik This Thesis is Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Clean Energy and Conservation Strategy Engineering, Faculty of Graduate Studies, An-Najah National University, Nablus-Palestine 2014 III Dedication To my father, mother, brother and sisters...……………….. To my wife and sons………………………………………….. To all friends and colleagues………………………………… To everyone works in this field…………………………….. To all of them, I dedicate this work IV Acknowledgment I would like to thank my family for constant love and support that have always given me. My furthermost appreciation goes to my supervisor, Dr. Imad Ibrik for his exceptional guidance and insightful comments throughout the duration of this project. Thanks go also to all my friends and fellows graduate Students. My special gratitude and appreciations go to the educational staff of Clean Energy and Conservation Strategy Engineering Master Program in An-Najah National University. V اإلقرار :العٌْاى تحول التي الزسالح هقذم أدًاٍ، الوْقع أًا The Techno - Economical Impact of PV On-Grid Systems on the Security of Palestinian Electrical Supply (Jericho PV system - Case study) إليَ اإلشارج توت ها تاستثٌاء الخاص، جِذي ًتاج ُْ إًوا الزسالح ُذٍ عليَ اشتولت ها تأى أقز علوي لقة أّ درجح أي لٌيل قثل هي يقذم لن هٌِا جزء أي أّ كاهلح، الزسالح ُذٍ ّأى ّرد، حيثوا .أخزٓ تحثيح أّ تعليويح هؤسسح أي لذٓ تحثي أّ Declaration The work provided in this thesis, unless otherwise referenced, is the researcher's own work, and has not been submitted elsewhere for any other degree or qualification. Student's Name: :اسم الطالة Signature: :التوقيع Date: :التاريخ VI List of Abbreviations AC Alternative current DC Direct current kWh Kilo watt hour STC Standard Test Condition PSH Peak sun hour PV Photovoltaic FIT Feed in Tariff GTI Grid Tie Inverter PWM Pulse Width Modulation LCC Life Cycle Cost AW Annual Worth PW Present worth PEA Palestinian Energy Authority PERC Palestinian Electricity Regulatory Council PSI Palestinian Solar Initiative SCADA Supervisory Control and Data Acquisition MPPT Maximum Power Point Tracker SPBP Simple Pay Back Period LV Low Voltage MV Medium Voltage Wp Watt peak CER Certified Emission Reduction VII Table of Contents No. Contents Page Dedication III Acknowledgment IV Declaration V List of Abbreviations VI Table of Contents VII List of Tables X List of Figures VII List of Appendixes XIII Abstract XIV Introduction 1 Structure of Thesis 2 Chapter 1: Renewable Energy Strategy in Palestine 4 1.1 Renewable Energy Potential in Palestine 5 1.1.1 Wind Resource 6 1.1.2 Biogas Resource 8 1.1.3. Solar Resource 8 1.1.3.1 Solar Radiation 9 1.1.3.2 Ambient Temperatures 11 1.2 Solar Energy Applications in Palestine 13 1.3 Energy Strategy by 2020 in Palestine 16 Chapter 2: Solar Energy Systems 19 2.1 Elements of PV Systems 20 2.2 Types of PV Systems 21 2.2.1 Off-Grid PV Systems 21 2.2.2 Grid-Connected PV Systems 22 2.3 Policy of On-Grid PV Systems 23 2.3.1 Feed in Tariff (FIT) 23 2.3.2 Net Metering 24 2.4 Renewable Energy Policy in Palestine 25 2.4.1 The Palestinian Solar Initiative (PSI) 25 2.4.2 Feed in Tariff for the Palestinian Solar Initiative 26 Chapter 3: Design of PV On-Grid Systems 28 3.1 Selection the Capacity of PV Modules 29 3.2 Selection of Grid Tie Inverters 35 3.2.1 Multiple Inverters 36 3.2. 2 Inverter Sizing 37 3.3 Grid Connection 39 3.4 Configuration of Monitoring System 40 Chapter 4: Modeling On-Grid PV Systems 42 VIII No. Contents Page 4.1 Configuration of Grid Tie PV System 43 4.2 Mathematical Modeling of Photovoltaic Array 44 4.3 Simulink Modeling of the Photovoltaic Array 53 4.4 Validation of PV Simulink Model 57 4.5 Impact of Shading on I-V Characteristic Curve of Photovoltaic Module 61 4.6 Maximum Power Point Tracking (MPPT) 66 4.6.1 Incremental Conductance Based Maximum Power Point Tracking (MPPT) 66 4.6.2 Incremental Conductance MPPT Algorithm 67 Chapter 5: Techno-Economical Impact of PV On- Grid Systems 69 5.1 Determining the Cost of Producing One kWh from Grid Tie PV System 70 5.1.1 Life Cycle Cost (LCC) 70 5.1.2 Economic Factors 72 5.1.3 Cost of Producing One kWh from Grid Tie PV System for Jericho Power Plant 73 5.2 Evaluation the Economic Impact of Jericho Grid Tie PV System 75 5.3 Levelized Cost of Energy (LCOE) 75 5.4 Environment Impact of Grid Tie PV System 77 Chapter 6: Performance Analysis of Jericho PV On-Grid System 78 6.1 Introduction of Jericho PV On-Grid System 79 6.2 Elements of Jericho PV On-Grid System 79 6.2.1 PV System 81 6.2.2 DC/AC Inverter 83 6.2.3 Step-up Voltage Transformer 84 6.2.4 LV/MV Transformer 84 6.2.5 Switchgear 84 6.2.6 Main Monitoring System 85 6.3 Performance Analysis of Jericho Solar PV Station 85 6.4 Environmental Impact Assessment for Jericho Solar Station 88 6.5 Simulink Configuration of Jericho PV Power Plant 89 6.6 Recommendation 90 Chapter 7: Conclusions & Future Scope of Work 92 7.1 Conclusions 93 7.2 Scope for Future Work 93 IX No. Contents Page References 94 Appendices 97 ب الملخص X List of Tables No. Table Page Table 1.1 Wind speed (measured at 10 m height) and potential in some areas of the West Bank 8 Table 1.2 The daily ambient temperature 23-7-2013 12 Table 1.3 Energy strategy by 2020 in Palestine 18 Table 2.1 PSI geographic distribution 26 Table 2.2 PSI first three year rollout plan 27 Table 4.1 Electrical characteristics data of the MSX-50 solar 57 Table 5.1 Cost of elements and installation of grid tie PV system 73 Table 5.2 On ground PV LCOE 76 Table 5.3 On ground PV LCOE sensitivity analysis 77 Table 6.1 Kaneka PV module's datasheet 82 Table 6.2 Grid connected inverter datasheet 83 Table 6.3 Solar station data from 8/2012 – 1/2013 85 Table 6.4 Generated KWh units from solar station that seen by grid 87 Table 6.5 Amounts of energy generated by Jericho PV power plant 89 XI List of Figures No. Figure Page Figure 1.1 Wind potential in Palestine 7 Figure 1.2 Kardallah monthly solar irradiation average 10 Figure 1.3 Irradiation and temperature profile at the Jericho area 11 Figure 1.4 The daily ambient temperature 23-7-2012 12 Figure 2.1 Schematic of off-grid PV systems 22 Figure 2.2 Schematic of grid-connected PV systems 23 Figure 3.1 Array of PV panels divided in strings 31 Figure 3.2 Irradiation and temperature influence to PV cells performance 34 Figure 3.3 Grid tie inverter 36 Figure 3.4 Grid tie feed in tariff 40 Figure 3.5 Grid tie net metering tariff 41 Figure 4.1 Simulink model of PV system 43 Figure 4. 2 PV cell equivalent circuit 45 Figure 4.3 A typical I-V, P-V characteristics of a solar cell 46 Figure 4.4 Influence of the ambient irradiation on the PV cell - a); and of the cell temperature on the cell characteristics - b). 48 Figure 4.5 Series (a) and parallel (b) connection of identical cells 48 Figure 4.6 PV module equivalent circuit 49 Figure 4.7 Model structure of the photovoltaic array 53 Figure 4.8 Simulation of the PV module 54 Figure 4.9 Simulink modeling implementation for Io 55 Figure 4.10 Simulink modeling implementation for Iph 55 Figure 4.11 Simulink modeling implementation for Im 56 Figure 4.12 PV array modeling 56 Figure 4.13 PV model simulation at different temperatures 58 Figure 4.14 Simulink IV characteristic curves for different temperatures 58 Figure 4.15 Datasheet IV characteristic curves for different temperatures 59 Figure 4.16 PV model simulation at different radiations 59 Figure 4.17 Simulink IV characteristic curves for different radiations 60 Figure 4.18 Simulink P-V characteristic curves for different temperatures 60 Figure 4.19 Simulink P-V characteristic curves for different radiations 61 XII No. Figure Page Figure 4.20 PV modules with bypass diodes 63 Figure 4.21 Each position of bypass diodes and blocking diodes 64 Figure 4.22 Two PV module with series connection at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab - Simulink. 64 Figure 4.23 I-V characteristics at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab - Simulink [Y- axis: current (A), X - axis: voltage (volt)] 65 Figure 4.24 P-V characteristics at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab - Simulink [Y- axis: power (watt), X - axis: voltage (volt)] 65 Figure 4.25 Basic idea of incremental conductance method on a P-V curve of solar module 66 Figure 4.26 Incremental conductance MPPT flow chart 68 Figure 5.1 Cash flow which represent initial, operational cost and salvage revenue 71 Figure 5.2 Cash flow of grid tie PV system for Jericho PV power plant 74 Figure 6.1 Jericho PV station single line diagram 81 Figure 6.2 Generated KWh units from Jericho solar station 86 Figure 6.3 Monthly average solar radiation in Jericho station 87 Figure 6.4 Generated kWh units from solar station that seen by grid 88 Figure 6.5 Simulink model of grid tie PV system 90 XIII List of Appendixes No. Appendix Page Appendix A Specifications of Jericho PV on-grid system elements 97 Appendix B Simulation models 111 Appendix C Performance results of Jericho PV on-grid system 114 Appendix D Simulation results 124 Appendix E Table of interest at i = 10% 128 XIV The Techno - Economical Impact of PV On-Grid Systems on the Security of Palestinian Electrical Supply (Jericho PV system - Case study) By Abdel Latif Wasef Abdel Latif Kharouf Supervisor Dr. Imad Ibrik Abstract This research based on modeling the grid tie PV power system using Matlab Simulink software program in order to study the techno-economic performance analysis of building these systems according to our environmental conditions such as temperature, solar radiation and wind speed. The main objective of research is to design a grid tie PV system by using Matlab Simulink program and apply this system on Jericho PV power plant as a case study. To achieve this objective we should study the mathematical models which characterize each part of grid tie PV power system such as PV module, MPPT controller, transformer, and then convert the mathematical models to Simulink models. Furthermore, we should investigate the design connection topologies for all components of grid tie PV system in order to study the operation of system for different environmental conditions. Current predictive models are very useful for a grid tie system, which is limited to operate at the maximum power point. These models accurately predict the power output of different PV On grid tie system based on data specification. XV The program is dynamic, and fit with the changes of parameters, which are related to the reduced power output caused by increased temperature, as well as the effect of non-linear absorption of solar radiation on power output. Data was collected and analyzed as a case study for Jericho PV power plant. On the M.V case study of Jericho network and Jericho Solar PV station, negligible technical impacts were noted on the current level of penetration which, the current capacity of the station, equals 300 kWp. On the low voltage case study, it is recommended to minimize the negative technical impact of the distributed PV generators on the conventional grid by using smart grid systems to monitor the grid performance hourly and control the energy exchange times. Regarding the L.V case, it’s recommended from the researcher point of view, as a result of this study, that it was more justified and preferable if limiting the PV penetration level on the grid to 15% or to equal the minimum load of the feeder by the regulator for more safety. Based on the economic evaluation, the cost of energy generated by Jericho PV power plant were studied is 0.18 (US$/kWh) while the cost of energy generated by conventional supply is 0.19 (US$/kWh). 1 Introduction Solar energy is one of the most abundant energy resources on earth. Photovoltaic (PV) technology converts this natural energy (solar radiation) into electricity creating no pollution with consuming no conventional fossil fuels, and lasting for decades with relatively little maintenance efforts. The use of a widely available and reliable energy source, the sun, makes this related technologies highly promising. Indeed, numerous examples of deployed systems are already successfully available in the world. In addition, the scalable nature of the technology lends itself well to varying power requirements from the smallest autonomous platforms to infrastructure-based systems. PV module represents the fundamental power conversion unit of a PV generator system. The output characteristics of PV module depends on the solar insolation, the cell temperature and output voltage of PV module. Since PV module has nonlinear characteristics, it is necessary to model it for the design and simulation of maximum power point tracking (MPPT) for PV system applications. Almost all well-developed PV models describe the output characteristics mainly affected by the solar insolation, cell temperature, and load voltage. PV On – grid systems has the ability to provide 24-hour electricity to the load. This system offers a better reliability, efficiency, flexibility of planning and environmental benefits compared to the standalone system. Each kilowatt-hour (kWh) generated from solar systems saves the environment from the burning of fossil fuels. The diesel –fired and the 2 natural-gas-fired power generators produce 1.2 Kg and 0. 5307 Kg carbon dioxide, respectively, to generate 1 kWh electricity [1]. The main scope of thesis is to study the medium voltage level PV generation system station. The study case of this thesis investigates a techno-economic study of the Jericho PV generation station in Jericho, West Bank with total installed capacity 300 kWp. Structure of Thesis The work carried out in this thesis has been summarized in seven chapters Chapter 1: Renewable Energy Strategy in Palestine This chapter illustrates renewable energy potential in Palestine, Photovoltaic (PV) Implemented Projects in Palestine, and energy strategy in Palestine by 2020. Chapter 2: Solar Energy Systems This Chapter describes the main elements of PV systems, types of PV systems, Policy of on-grid PV systems (Feed in Tariff, Net Metering), and renewable energy policy in Palestine. Chapter 3: Design of PV On-Grid Systems This chapter describes the selection of the capacity of PV modules, selection of grid tie inverters, grid connection, and configuration of monitoring system. Chapter 4: Modeling On-Grid PV Systems This chapter describes mathematical modeling and Simulink of grid tie PV system and designs a grid tie PV system by using Matlab Simulink and 3 observes how the system works with a dynamics behavior of changing solar radiations and temperature. Chapter 5: Techno - Economical Impact of PV On-Grid Systems This chapter studies the evaluation of techno economical impact of Jericho grid tie PV system, Levelized Cost of Energy (LCOE), Environment impact of grid tie PV system. Chapter 6: Performance Analysis of Jericho PV System This chapter introduces some information about Jericho PV power plant, potential of solar energy, also, sizing the elements of the grid tie system for this plant and simulation results in different conditions such as solar radiation and temperature. Chapter 7: Conclusions and Future Scope of Work This chapter describes the main conclusions about grid tie PV system and future scope of work. 4 Chapter One Renewable Energy Strategy in Palestine 5 1.1 Renewable Energy Potential in Palestine Introduction Palestine is located between 34º:20´ - 35:30´ E and 31º: 10´ - 32º:30´ N , It consists of two separated areas from one another , the Gaza Strip is located on the western side of Palestine adjacent to the Mediterranean Sea and the West-Bank which extends from the Jordan River to the center of Palestine . Palestine's elevation ranges from 350 m below sea level in Jordan Valley, to sea level along Gaza Strip sea shore and exceeding 1000 m above sea level in some mountains sites in the west-Bank. Climate conditions in Palestine vary widely, the coasted climate in Gaza Strip is humid and hot during summer and mild during winter. These areas have low heating loads, while cooling is required during summer. The daily average temperature and relative humidity vary in the ranges: (13.3 – 35.4) C° and (67 – 75) % respectively. In the hilly areas of the West-Bank, cold winter conditions and mild summer weather are prevalent. Daily average temperature and relative humidity vary in ranges: (8 – 23) Cº and (51 – 83) % respectively. In some areas the temperature decline below 0 Cº. Hence, high heating loads are required, while little cooling is needed during summer. In Jericho and Jordan Valley, almost no heating is needed during winter while high cooling during summer is needed [2]. Renewable energy is energy that is derived from natural processes that are replenished constantly. In its various forms, it derives directly or indirectly from the sun, or from heat generated deep within the earth. 6 Included in the definition is energy generated from solar, wind, biomass, geothermal, hydropower, ocean energy, bio-fuels and hydrogen derived from renewable resource. The main renewable energy sources considered to have potential in Palestine are wind energy, biogas and solar energy. 1.1.1 Wind Resource The wind speeds in the West Bank are low or moderate, varying between 2-5 m/s, depending on the site and altitude. Which can be translated to an average wind potential of 150 kWh/m² yr in the Jordan valley, 300-450 kWh/m² yr in most of the West Bank and in some spots (like in the northern and southern parts) it could reach up to 600 kWh/m² yr, as shown in figure 1.1. However, these figures were based on estimates and theoretical calculations without any wind measurements or real data from the field. Thus, an analysis with real measurements covering different parts of the West Bank was still needed and is presented [3]. 7 Figure (1.1): Wind potential in Palestine However, based on previously available metrological data from various stations (around the West Bank taken before the year 2000 from the national meteorological stations) average wind speed is moderate, see table 1.1. 8 Table 1.1 - Wind Speed (measured at 10m height) and Potential in some areas of the West Bank 1.1.2 Biogas Resource In Palestine there are many people living from the agriculture in rural areas. Therefore animal solid waste resources appear as a useful and viable input for electricity generation. Moreover, recently the informal deposit of solid waste has been forbidden. As a consequence, three large landfills had planned to build in the West Bank. This assessment analyzes the potential of these two sources of energy to produce biogas used for electricity generation through the following applications:  Animal waste distributed digester (50 kW)  Landfill waste centralized digester (6 MW) [4] 1.1.3. Solar Resource Palestine has high potential of solar energy. It has around 3000 sunshine hours / year and high annual average solar energy radiation which is about 5.45 kWh/m² - day. The lowest average solar energy is in December which is about 2.84 kWh/m² - day and the highest one is in June which is about 8.245 kWh/m² - day [2]. 9 These figures are encouraging to exploit the solar energy for different applications such as water heating, drying of crops, vegetables, and fruits, water desalination, water pumping, and electrification of remote locations far from the electrical networks, and also for distributed generation of electricity for shaving peak demand as a DSM tool . In order To Know the Potential of solar energy in Palestine, we must study and measure two elements. 1- Solar Radiation (w/m²) 2- Ambient Temperature (C) 1.1.3.1 Solar Radiation Solar irradiation data can be obtained mainly in two different ways: from ground meteorological stations or by satellites (geostationary or polar- orbiting). Some well-known available online web applications such as PVGIS1 use data from ground measurements in their first databases, which are then interpolated until they cover the desired surface resolution. New databases that are being incorporated in such applications come from satellite databases like Meteosat. Satellite data is not as accurate as ground measurements but it offers the best coverage and regular calculations for large territories. Satellite data covering Palestine territories comes from Meteosat satellites, which are treated into different solar databases. One of the available databases is Helioclim2, produced using the Heliostat 2 processing models from Meteosat images. Since data comes from satellite images, data 10 precision depends on their resolution, which in turn depends on the latitude and longitude of the site. Monthly averages from ground stations have been compared with data values from the Helioclim databases. Furthermore, in order to strengthen the data analysis, measurements have also been compared with the irradiation data provided by the PVGIS tool. PVGIS data also comes from the Helioclim databases, but provides only the average monthly irradiation data from the last few years [5]. Figure 1.2 depicts the graphical result of the correlation data analysis of Kardallah ground station. Figure (1.2): Kardallah monthly solar irradiation average 11 It is clear that the different series of data do not present significant differences. The data analysis shows that the average difference is lower than 10%. In conclusion, on average Palestine has a solar Global Horizontal Irradiation of 5.2 kWh/m²/day, which yearly stands for about 1900 kWh/m²/year. Figure 1.3 depicts the relation between the Global Horizontal Irradiation used for the photovoltaic technology, and the Direct Normal Irradiation used for the CSP plants, at the Jericho area using Meteonorm databases. As expected, DNI irradiation is higher than Global Horizontal Irradiation, especially in winter. Figure (1.3): Irradiation and temperature profile at the Jericho area 1.1.3.2 Ambient Temperatures Ambient temperature affects the PV generators efficiency. The relation between efficiency and ambient temperature is inversed. 12 The shown data is the average of five days measurement in June 2013. The original Measurements are done on a 5 - minute interval basis. Table 1.2: The daily ambient temperature 23-7-2013 Figure (1.4) shows the daily curve of the ambient temperature drawn from the data table (1.1). It shows that the maximum temperature occurs around noon time (32°C), and the minimum temperature occurs in the early morning (21°C). Figure (1.4): The daily ambient temperature 23-7-2013 13 1.2 Solar Energy Applications in Palestine: Photovoltaic electrification in isolated rural villages and communities in Palestine is considered feasible and effective compared with other alternatives like electrical grid and diesel generators. The PV electrification could be using the decentralized stand alone and centralized systems, depending to the nature of the load and the distribution of houses. Photovoltaic electrification is limitedly used in different rural areas in Palestine mainly for schools, clinics, Bedouins communities, agricultural and animal farms, and private homes. The most important solar energy projects in Palestine are: 1. Atouf (Tubas) project by PV centralized power system; the village includes 25 houses, school, and clinic with power capacity about 12 kWp. 2. Imnezel (south Hebron) project by PV centralized power system. 3. Al-Saed (Yaebd-Jinin) project by PV centralized power system. 4. Al-Mikhal (Yaebd-Jinin) project by PV centralized power system. 5. Yerza (Tubas) project by PV decentralized power system. 6. Ibziq (Tubas) project by PV decentralized power system. 7. Electrifying a Palestinian School Rabood (south Hebron) by PV decentralized power system. 8. Electrification of Alisteqlal center for media and development by PV decentralized power system. 14 9. Electrification of Um-Alkher, Almajaz and Aldaqiqa villages in south of Hebron by PV decentralized power system. 10. The applied research institute-Jerusalem (ARIG), implemented some PV projects such as:  Utilization of Solar Energy in lighting Jub-Altheib Village in the West Bank (Southeast Bethlehem).  Utilization of Solar Energy in lighting Al-Bierh Children Happiness Center (Albira).  Utilization of Solar Energy in lighting the emergency entrance of the clinic of Medical Charitable Society (Toque- Bethlehem).  Installed 500 watt solar system at the Applied Research Institute to power the external lighting system of ARIJ and to assist in establishing a research center for renewable energy [6]. 11. Palestinian solar and sustainable energy society (Psses), implemented project for Streetlights of Wadi El-Nar (the road connects Hebron with Bethlehem) by Solar energy [7]. 12. Renewable energy Unit- Hebron University. Research and development of exploitation of wind energy and solar energy for lighting of the University and its facilities by two stages, First stage; lighting the green room at the University, Second stage; street lighting for the University [8]. 13. Action Against Hunger Foundation (ACF). Implemented some Projects to supply electricity to the Nomadic areas in Yatta, Khirbet Altaban and Alfkhit (South of Hebron) using solar energy [9]. 15 14. SATCO Company. Implemented project of Street Lighting using Solar Energy; this project was executed in December 2010 in Jericho city, to light the Amman-AL-Karama Bypass Street in Jericho [10]. 15. Palestinian Energy Authority implemented some PV projects such as: Jericho PV project - This project provides the Palestine with Photovoltaic Power Generation system of 300 kW output of grid tied type in Jericho Governorate; this project was funded by Japanese Government, with the support of the Japanese development cooperation (JICA). Tubas PV project - This project provides the Palestine with Photovoltaic Power Generation system of 120 kW output of grid tied type in Tubas Governorate; this project was funded by Czech Republic, with the support of the Czech Development Agency. 16. Authority of Water and House of Water and Environment (HWE) and An-Najah National University implemented Water pumping project in the Palestinian village Beitillu (Ramallah) by using solar energy, this project was funded by UNDP_ GEF\SGP [11]. 17. Palestinian Hydrology Group for water and environmental resources development (PHG) –Gaza, Implemented lighting project. The main aim is to provide electricity for Gaza Valley Bridge by solar energy; this project was funded by Global Environmental Facility - Small Grant Program, and UNDP [12]. 16 1.3 Energy Strategy by 2020 in Palestine Since Palestine is a developing nation, its access to considerable amounts of energy is essential to achieve economic growth and development. While most of Palestine has access to electricity, there are many challenges facing Palestine, arising mainly from its energy dependence. Its energy is not provided through domestic means but rather provided through Israel which controls the quantity and quality of energy imported. Electricity is one of the major problems facing the Palestinian Authority, especially as the PA imports the majority of its needs, depending mainly on Israel (even though there is a power-generation plant in Gaza). Palestinians are still very dependent on importing electricity. One of the main obstacles that most of the government in the developing countries encounter is how to improve the efficiency and the degree of reliability of energy supplied while making modern energy services available to all people and affordable at the same time, and because of the huge unmet demand for energy and the volatility of energy prices in the recent period, ensuring the availability and security of energy supplied at reasonable prices has become the core issue in the development of energy policy. Accordingly, the Palestinian Energy Authority has prepared a strategy for renewable energy as an important part of the resources matrix, where Palestine needs clean and more secure supply of electrical power. The Palestinian Energy Authority has developed a clear goal for the year 2020 is as follows: 17 To attain 240 GWh gradually (at least) to generate electricity from different renewable resources which is equivalent to 10% of the power that will be produced locally by 2020, according to the strategic plan of the energy sector. The estimated exploitation of renewable resources (thermal) is about 18% of the total current energy consumption in Palestine, which represents 2287 GWh (of the power produced) which will be used in particular in heating and thus, the dependence on renewable energy will reach 25% of the power produced by the year 2020 [13]. To achieve this goal, this strategy requires:  Apply the necessary regulations and legislations for the development and promotion of the use of this technology.  Securing funding sources to cover the required costs and provide incentives for private sector investors.  Approving a plan to develop local human resources to be capable of manufacturing, installing and managing the renewable energy systems.  Applying the Palestinian solar initiative (PSI) for the period between 2012-2015.  Adopting a development plan for the renewable energy resources until 2020. Based on the assessment studies of renewable energy resources conducted by the energy authority, the required technology needed have been identified in terms of application and investment until 2020. 18 Table 1.3: Energy Strategy by 2020 in Palestine Technology used 2020 (MW) On Ground PV 25 Rooftops PV (Palestinian Solar Initiative) 20 Concentrated solar power plants 20 biogas from landfills 18 biogas from animal waste 3 Small-scale wind 4 Wind Farms 40 Total 130 It is noted from the table above that the dependence on solar energy sources represented 50% of total capacity, so this strategy contained the initiative of solar energy in order to disseminate and promote the use of renewable solar energy technology to generate electricity [13]. 19 Chapter Tow Solar Energy Systems 20 2.1 Elements of PV Systems Photovoltaic systems (PV system) use solar panels to convert sunlight into electricity. A system is made up of one or more solar panels, usually a controller or power converter, and the interconnections and mounting for the other components. A small PV system may provide energy to a single consumer, or to an isolated device like a lamp or a weather instrument. Large grid-connected PV systems can provide the energy needed by many customers. Generally, PV panel, Power conditioner (inverter), batteries, distribution board and junction box can be counted as typical components of PV systems.  PV panel: photovoltaic panels convert sunlight to direct current (DC) electricity which can be used to charge batteries or to supply loads.  Charge controller: This manages the efficient charging of the batteries using the DC energy from the PV panels.  Batteries: DC energy is stored in deep cycle lead-acid batteries, which give back the electricity as needed, especially when no charging energy is being produced. Energy put into batteries over a period of time can be taken out more quickly when needed. Lead –acid batteries need to be quickly 100% re-charged to remain in good condition. To maintain a good lifespan, they should not be drawn down below 50% charge.  Inverter: The inverter converts the DC energy from the batteries or panels to 220 volts AC for standard house loads [14]. 21 2.2 Types of PV Systems PV systems can be mostly classified as standalone (off-grid) system and grid-connected (on-grid) system by applications of the power connection. Various applications could be available according to a combination of facilities on site and each project. Figure-2.1 and figure-2.2 show each schematic. 2.2.1 Off-Grid PV Systems An off-grid system does not have a connection to the electricity "mains" (grid). Standalone systems vary widely in size and application from wristwatches or calculators to remote buildings or spacecraft. If the load is to be supplied independently of solar irradiance, the generated power is stored and buffered with a battery. In non-portable applications where weight is not an issue, such as in buildings, lead acid batteries are most commonly used for their low cost and tolerance for abuse. A charge controller may be incorporated in the system to: a) avoid battery damage by excessive charging or discharging and, b) optimizing the production of the cells or modules by maximum power point tracking (MPPT). However, in simple PV systems where the PV module voltage is matched to the battery voltage, the use of MPPT electronics is generally considered unnecessary, since the battery voltage is stable enough to provide near- maximum power collection from the PV module. In small devices (e.g. calculators, parking meters) only direct current (DC) is consumed. In larger systems (e.g. buildings, remote water pumps) AC is usually required. To 22 convert the DC from the modules or batteries into AC, an inverter is used [14]. Figure (2.1): Schematic of off-grid PV systems 2.2.2 Grid-Connected PV Systems A grid connected system is connected to a large independent grid (typically the public electricity grid) and feeds power into the grid. Grid connected systems vary in size from residential (2-10 kWp) to solar power stations (up to 10s of MWp). This is a form of decentralized electricity generation. In the case of residential or building mounted grid connected PV systems, the electricity demand of the building is met by the PV system. Only the excess is fed into the grid when there is an excess. The feeding of electricity into the grid requires the transformation of DC into AC by a special, grid-controlled solar inverter [14]. 23 Figure (2.2): Schematic of grid-connected PV systems [14] 2.3 Policy of On-Grid PV Systems 2.3.1 Feed in Tariff (FIT) Since the power generation costs of different RE technologies vary, a successful FIT design should provide technology-specific tariff levels. The following factors influence the power generation costs and therefore should be taken into account when the tariff levels are determined:  Investment for the plant  Other costs related to the project, such as expenses for licensing procedures  Operation and maintenance (O&M) costs  Fuel costs (in the case of biomass and biogas)  Return on/of capital  Other potential revenues (for instance, CER selling)  Financial constraints commonly employed by financing institutions (DSCR6, etc.) 24  According to the expected amount of electricity generated and the estimated lifetime of the power plant, a level of remuneration can be fixed [15]. 2.3.2 Net Metering Net metering policies and programs may serve as an important incentive for consumer investments in renewable energy generation. Net metering shall be available to any Palestine consumer who generates electricity from a renewable source (wind, solar, water or biomass), using equipment of maximum cumulative output up to 100 kW. One of the key aspects for this mechanism is the settlement of the guidelines to implement this system. Below are listed the main steps:  Contact with the local utility company for obtaining a net metering agreement.  An authority shall be appointed and entitled of inspect and approve net metering equipments.  Determine the size system. Such net metering arrangements may involve separate sets of unidirectional meters for recording the electricity received and supplied to the utility by the power producer, or special bidirectional meters capable of instantaneously recording net power transfers. This facility would be particularly suitable for incentivizing dispersed small scale RE generation, such as rooftop PV panels, helping optimize their utilization and payback rates and obviating the need for expensive on site storage batteries. 25 The suited approach for Palestine should be similar than the EU methodology, purchasing electricity at retail prices and selling their own power output at feed in tariff price settled depending on the characteristics of the generation technology and size. The settlement of a net metering approach similar than United States require an upfront subsidy which, at the end of the day, result at least the price rate established for that technology. This type of net metering is considered simplest that the proposed approach [15]. 2.4 Renewable Energy Policy in Palestine 2.4.1 The Palestinian Solar Initiative (PSI) The first phase will include an unprecedented initiative to spread the concepts of solar energy which is called the Palestinian Solar Initiative (PSI). This initiative consists of three phases over a period of three years from the mid-2012 until mid-2015. This initiative aims to set up small businesses with a capacity up to 5 kW for each project to be installed on the roofs of homes to achieve 1/2 MW from the 100 homes in first half and expand the project up to generate one and a half MW during the following year. In the last year of the project it will generate 3 MW extra to reach a total of 5 MW at the end of three years. Nearly 1,000 homes, distributed 30%, 40% and 30% in northern, central, and southern West Bank, respectively, in addition to 400 homes in the Gaza Strip when it is possible. Every citizen shall install this system in his home will attain a preferable electricity tariff produced from solar cells [15]. 26 2.4.2 Feed in Tariff for the Palestinian Solar Initiative The concept of the Palestinian solar Initiative has been drafted as part of the renewable energy strategy for PEA and PERC. The initiative aims to achieve a 5 MW of solar energy renewable by 2015, through the installation of solar cells on the roofs of 1000 houses throughout the West Bank. And it will be distribute 5 MW of renewable solar energy in different regions of the West Bank according the following table: Table 2.1- PSI geographic distribution MW Location 1.5 North WB 2 Center WB 1.5 South WB The reasons behind the Palestinian solar initiative are as follows:  Increase technology awareness  Attaining international support especially from the communities that are interested in renewable energy  To encourage the Palestinians on the use of renewable energy technologies  reduce carbon dioxide emission in Palestine  Political benefits, to get independence from the Israeli power sources  Increase the knowledge of the Palestinians in the field of renewable energy [15]. The PSI is supported by financial incentives that facilitate the initiative and shorten the pay-back period by more than one half. 27  The Palestinian solar power initiative will be supported by subsidies and rebates that aim at encouraging people to install PV panels on their rooftops.  Through the PSI, PENRA aims at shortening the pay-back period by more than one half for people installing PV panels. This means that the average 20 to 25-year pay-back period of regular PV installations will be reduced to around seven to eight years.  Two kinds of subsidies were set in place to support the PSI; rebates and feed-in tariffs (FIT). The table below depicts the rebates and FIT’s that are planned for the period between 2012 and 2014.  The PSI will be subsidized by a 47% subsidy (approximately USD 7.5m) and the participants will contribute the remaining 53% (approximately USD 8.5m).  It’s worth noting that the planned rollout of the PSI is 100 households in the first year (2012), 300 households in the second year and 600 in the third year. The expected PV production within the rollout is 750 MWh in 2012 going up to 7500 MWh in 2014 as the rollout period ends [15]. Table 2.2- PSI First Three Year Rollout Plan 28 Chapter Three Design of PV On-Grid Systems 29 3.1 Selection the Capacity of PV Modules The PV generator is composed by the total photovoltaic panels responsible of generating electricity by transforming solar energy. Opposite to off grid applications were dimensioning must fit the requirements of energy consumption of a specific village, community or even a single house, On ground PV installations are supposed to produce as much energy as possible, since the goal is to sell energy to the grid and make profit with it. The only or the most limiting factor of plant size is the amount of money that the project developer wants to invest. Large photovoltaic installations as a consequence have a wide range of kWp of power, typically starting from few kWp such as 50 kWp, up to 97 MW (biggest PV plant constructed). Unlike off grid installations, On ground PV installations need big areas of terrain being this another typical constraint. The PV generator part of these installations represents the main component while considering the amount of material needed and as a consequence, the highest cost. Since the feasibility of the project will depend on the amount of energy sold to the grid, and this to the electricity that the PV generator is capable to produce, it is important to take into account some basic considerations during the projection of it [16]: Shadows Photovoltaic panels decrease their productivity if they have a partial or total shadow over them to the level that depending on the model of the panel, it can just not produce any energy. Solar panels in a generation park are divided in groups of several rows working together. Hence, the fact that 30 one or more panels do not work because of shadowing over them (or any other reason), affects the overall performance of the group and even the generator park in terms of energy produced instantly. Shadows usually are produced either by external elements of the generator park (these can be from some elements like trees which are possible to modify, to other like buildings or mountains), or by internal elements (usually the panels itself makes shadows over other nearby ones). In some cases we will be able to modify the elements that can produce permanents shadows over the generating solar system (such as trees), other cases help determine the area where the generator park is placed (such as mountains or buildings), and other affect directly the design of the generator park itself (shadows between panels). Whichever the case, shadows are an important factor to consider and avoid since it affects directly the performance of the installation. Land Since PV on-grid installations can be really big installations, it may need a considerable amount of land, so sometimes it can also be a limiting factor or at least condition the site of the installation. While evaluating the approximate amount of land needed, it can be taken as a reference that only considering the surface of the panels, for 1 kWp of power around 6-7 m² are required. However, as mentioned it is important to consider the shadows that panels can produce to each other, the ratio commonly used in order to avoid shadows can increase project size to 15 to 20 m² for 1 kWp of power. These ratios are given as a valid reference for a pre-design. 31 Configuration PV Large installations can vary significantly in size. This means that different configuration strategies in terms of wiring the panels are needed. Solar panels especially in medium-big installations are divided in several arrays that work together. Each array (which might be composed of several strings of panels from a generating park), is connected to an inverter. The number of arrays and the number of panels that conforms each array depends on the characteristics of each installation and the characteristics of the inverters used. Figure (3.1): Array of PV panels divided in strings Dividing the panels into different arrays gives the installation a better reliability (if there is a problem with one inverter the other ones can still continue generating energy) and design (if a single inverter can hold a limited number of panels depending of the voltage and current produced by 32 the group). However, usually this configuration is recommended, but it makes the project more expensive because more equipment is needed. For powers above 50 kW three-phase inverters are used. Technology Different technologies exist nowadays depending on how the panel is manufactured and that affect both, the performance and the final price of it. The most common technologies while considering On ground PV installations are mono-crystalline, poly-crystalline and thin-film, having the first a slightly higher performance than the second and third one but also being more expensive. The final decision will depend on the criteria of the engineering team. More than the technology the tolerance percentage that the modules have over their peak power capacity designed by the manufacturer should also be considered. Other aspects to keep in mind while selecting solar panels are the following:  Codes  Resistance to weather conditions  Electrical connection box [16] Distance to grid On grid installations obviously need to be connected to the grid in order to feed the generated electricity. Sometimes and especially in areas not highly electrified, the nearest grid point of connection can be far from the 33 emplacement of the generation park. This is important because of two main reasons:  Having a long distance to the grid will increase dramatically the final cost of the project (prices of medium voltage grid extension in the Distributed PV section are highlighted).  Energy transport always is associated with energy losses. This means that for bigger generating parks the technical energy transportation losses will have to be compensated, again increasing the final cost of the project [16]. Orientation While considering the PV generator park configuration, it is important to determine the panels’ orientation, since this also affects directly the final performance of the park and emplacement configuration. Panels obtain a better performance while being orientated directly to the south for installations at the northern hemisphere and to the north for installations at the southern hemisphere. Usually there is a relative tolerance of about ±10 degrees. Emplacement Medium to big size installations must be placed on the ground, however, smaller size installations can also be placed over the roofs (usually on industrial buildings, supermarkets, farm building, etc.). The decision of placing the installation on the ground or over a roof depends firstly on the availability of each case and the characteristics of each installation and secondly on the regulation laws of a particular country. 34 Performance PV panels have different performance in function of the radiation and temperature, among other factors. These are not really factors that determine a configuration or emplacement of any installation, since such do not vary much inside a country itself especially if it is a small one. However, these factors are important when designing the installation in particular weather conditions [16]. Figure 3.2 shows the effects of irradiation (top) and temperature (bottom) to the performance of PV cells. Figure (3.2): Irradiation and temperature influence to PV cells performance 35 3.2 Selection of Grid Tie Inverters The inverter is responsible of transforming electricity from DC to AC. It must adapt the electricity to the needed characteristics in order to be injected to the grid: 230/400 V pure sine wave with a 50 Hz frequency. The inverter is also responsible of monitoring the grid for anti-islanding protection, which in such case the inverter should disconnect the PV system from the grid [17]. Islanding operation mode will be performed when Supply and/or Energize the PV power to loads and/or grid (transmission/distribution lines) under the following condition:  A part of grid is disconnected from the ordinary utility power sources.  The part of grid is energized by the PV power only.  The loads connected with the said grid is supplied the PV power only. Main characteristics of common inverters are the following ones: Self-commutated Provided with automatic maximum power point tracking (MPPT) system of the photovoltaic farm Anti-islanding protection and automatic connection and disconnection Galvanic isolation between the DC and AC inverter’s circuits Protections against shorts in AC Inverter’s manual starting/stopping control Performance over 90% when working over 25% of load 36 Power factor over 0.97 when working over 25% of load Auto consumption in night mode below 0.5 W Temperatures range between -15 and +45 ºC Environmental humidity range between 0 to 90% Internal measurement of impedance of the grid deactivated Figure (3.3): Grid tie inverter The selection of the inverter for the installation will depend on:  the energy output of the array  the matching of the allowable inverter string configurations with the size of the array in kW and the size of the individual modules within that array  whether the system will have one central inverter or multiple (smaller) inverters [17]. 3.2.1 Multiple Inverters If the array is spread over a number of rooves that have different orientations and/or tilt angles then the maximum power points and output currents will vary. If economic, installing a separate inverter for each section of the array which has the same orientation and angle will maximize the output the total array. 37 This could also be achieved by using an inverter with multiple maximum power point trackers (MPPTs). Multiple inverters allow a portion of the system to continue to operate even if one inverter fails. Multiple inverters allow the system to be modular, so that increasing the system involves adding a predetermined number of modules with one inverter. Multiple inverters better balance phases in accordance with local utility requirements. The potential disadvantage of multiple inverters is that in general, the cost of a number of inverters with lower power ratings is generally more expensive [17]. 3.2.2 Inverter Sizing Inverters currently available are typically rated for:  maximum DC input power i.e. the size of the array in peak watts  maximum DC input current  maximum specified output power i.e. the AC power they can provide to the grid. The maximum power of the array is calculated using the following formula: Array Peak Power = Number of modules in the array × the rated maximum power (Pmp) of the selected module at STC. The designer shall follow the manufacturer’s recommendation when matching the peak power rating of the array to that of the inverter. 38 Many manufacturers provide the maximum rating of a solar array in peak power for a specific size inverter. Accredited designers shall follow the recommendations of the manufacturer. If the manufacturer does not provide recommendations then the designer shall match the array to the inverter allowing for the de-rating of the /array. The typical PV array output in watts is de-rated due to:  manufacturers tolerance of the modules  dirt and temperature [17]. Inverter with crystalline modules Based on figures of:  0.97 for manufacture  0.95 for dirt  0.825 for temperature (based on ambient of 35°C). The de-rating of the array is: 0.97 × 0.95 × 0.825 = 0.76 Inverter with thin film modules The temperature effect on thin film modules is less than that on crystalline modules. Assuming the temperature coefficient is only 0.1% then the temperature de-rating at ambient temperature of 35°C is 0.965 Based on figures of:  0.97 for manufacturer  0.95 for dirt  0.965 for temperature (based on ambient of 35°C). The de-rating of the array is: 0.97 × 0.95 × 0.965 = 0.889 39 3.3 Grid Connection Energy produced by the photovoltaic generator, once it is transformed from DC to AC must be adapted to the voltage of the grid where it is going to be injected. On-grid photovoltaic plants are usually connected to medium voltage grids due to the capacity of the grid (usually it will be able to absorb all the energy produced by the PV generator) and the fact that normally these kinds of installations are far from urban centers. As a consequence the closest lines are in medium voltage. In the case of small on-grid installations however, which are more flexible in terms of emplacement and the grid probably arrives at the same place where the installation is placed, would be able to connect to the low voltage grid (these could be for example the case of roof photovoltaic installations). In both cases it is important to ensure that the grid offers the necessary stability (frequency, voltage) and capacity (cable section) to support the injection of all the energy produced by the photovoltaic plant. In a common On ground PV installation configuration it is necessary to transform and transport the generated energy to the adequate point where the distribution electric company of the area can absorb it. The transformation center will be placed closed to the photovoltaic installation in order to minimize the technical losses. The transformation center will keep the transformers and all the security equipment necessary to connect to the medium voltage grid. Usually the transformation center is built with pre-manufactured concrete allowing a fast and economic assembly. It is important to consider the necessary ventilation for the transformers to function properly while 40 designing the transformation center and all the security measures that medium voltage installations need according to the local codes. From the transformation center to the electrical distribution company substation usually aerial grid extension are used, however in some cases buried lines would fit better since they have a lower visual impact and due to the characteristics of the area it could be difficult to extend aerial lines. Moreover if the line needs to go through the photovoltaic panels it could shade them, affecting the energy production. 3.4 Configuration of Monitoring System Distributed photovoltaic applications analyzed are those suitable for urban areas mainly rooftop photovoltaic installations in buildings (but can also be integrated systems in car parks or in other ways). Building photovoltaic applications analyze the case where all the produced energy is sold to the grid. Typically two scenarios fit the configuration described in this application:  Generate energy to sell to the grid. This is the common feed in tariff scenario where user(s) can sell the produced energy at a fixed price for a guaranteed period established by the government. 41 Figure (3.4): Grid tie feed in tariff  Net-metering scenario. In this case the user would consume the produced energy, selling to the grid only the surplus. Figure (3.5): Grid tie net metering tariff Distributed PV installations characteristics are similar to Large Grid PV power plants differing obviously in size. As well a bi-directional meter is required to measure electricity taken and being fed into the grid. 42 Chapter Four Modeling On-Grid PV Systems 43 4.1 Configuration of Grid Tie PV System The configuration of grid tie PV system under study is shown in figure (4.1). Figure (4.1): Simulink model of PV system [18]. Figure (4.1) shows the Simulink model of grid tie PV system which consists of photovoltaic Array, DC-DC Boost converter, maximum power point tracking controller, three phase voltage source inverter, system controller and LC filter. For grid tie PV system the output of the PV array is connected to DC-DC boost converter that is used to perform MPPT functions and increase the array terminal voltage to a higher value so it can be interfaced to the distribution system grid. A DC link capacitor is used after the DC converter and acts as a temporary power storage device to provide the voltage source inverter with a steady flow of power. The capacitor’s voltage is regulated using a DC link controller that balances input and output powers of the capacitor. 44 The voltage source inverter is controlled in the rotating dq frame to inject a controllable three phase AC current into the grid. To achieve unity power factor operation, current is injected in phase with the grid voltage. A phase locked loop (PLL) is used to lock on the grid frequency and provide a stable reference synchronization signal for the inverter control system, which works to minimize the error between the actual injected current and the reference current obtained from the DC link controller. RL load are connected to the grid to simulate some of the loads that are connected to a distribution system network. An LC low pass filter is connected at the output of the inverter to attenuate high frequency harmonics and prevent them from propagating into the power system grid [18]. 4.2 Mathematical Modeling of Photovoltaic Array The PV uses semiconductor cells (wafers), each of which is basically a large area p-n diode with the junction positioned close to the top surface. PV results in the generation of direct voltage and current from the Sun’s (light) rays falling on the cell. To achieve higher voltage and current, multiple cells are used as needed. The PV cell can be represented by a simple equivalent circuit shown in Figure 4.2. The output current is a function of solar radiation, temperature, wind speed and coefficients that are particular to the cell technology. The PV current Ipv is a function of the array output voltage Vpv (V-I) characteristic of the array) which is given in Figure 4.3 The maximum 45 power output is obtained when the array operates at point M on the V-I characteristic. Figure (4. 2): PV cell equivalent circuit (Lorenzo, 1994) The model contains a current source Iph, one diode and a series resistance Rs, which represents the resistance inside each cell and in the connection between the cells. The net current is the difference between the photocurrent Iph and the normal diode current ID. (4.1) where: m– idealizing factor k – Boltzmann’s constant (1.38*10 -23 J/K) Tc– the absolute temperature of the cell e – electronic charge (1.6*10 -19 Cb) V – the voltage imposed across the cell Io – the dark saturation current (strongly depends on temperature) 46 Figure (4.3): A typical I-V, P-V Characteristics of a solar cell In the above representation of I-V characteristic, a sign convention is used, which takes as positive the current generated by the cell when the sun is shining and a positive voltage is applied on the cell’s terminals. A real solar cell can be characterized by the following fundamental parameters: A. Short circuit current: It is the greatest value of the current generated by a cell. It is produced under short circuit conditions: V = 0 B. Open circuit voltage Corresponds to the voltage drop across the diode (p-n junction), when it is traversed by the photocurrent Iph (namely ID=Iph) when the generator current is I = 0. It reflects the voltage of the cell in the night and it can be mathematically expressed as: (4.2) where: 47 Vt - known as thermal voltage and Tc is absolute cell temperature C. Maximum power point Is the operating point A (Vmax, Imax) at which the power dissipated in the resistive load is maximum: Pmax = Imax * Vmax D. Maximum efficiency Is the ratio between the maximum power and the incident light power. (4.3) where Ga is the ambient irradiation and A is the cell area. E. Fill factor is the ratio of the maximum power that can be delivered to the load and the product of Isc and Voc: (4.4) The fill factor is a measure of the real I-V characteristic. Its value is higher than 0.7 for good cells. The fill factor diminishes as the cell temperature is increased. 48 Figure (4.4): Influence of the ambient irradiation on the PV cell – a); and of the cell temperature on the cell characteristics – b). Figure (4.5): Series (a) and parallel (b) connection of identical cells In current practice, the performance of a module or another PV device is determined by exposing it at known conditions. The module characteristics supplied by the manufacturer are usually determined under special conditions, as for example nominal or standard conditions (Lorenzo, 1994) – see Table below: 49 In Figure 4.6 the series resistance Rs represents the internal losses due to the current flow, whereas the shunt resistance Rsh corresponds to the leakage current to the ground and it is normally ignored. For an ideal PV cell (no series loss and no leakage to ground, i.e., RS = 0 and RSH = ∞, respectively). The equivalent circuit of a PV module, which consists of a combination of series and parallel-connected cells are the same. Figure (4.6): PV module Equivalent Circuit The governing equations of the equivalent circuit are: (4.5) (4.6) (4.7) 50 (4.8) Where: V, I – output voltage and current q – electron charge (1.6*10 -19 Cb) k – Boltzmann constant (1.38*10 -23 J/K) T – temperature in K A – quality factor (constant) ID – reverse saturation current of the diode IL – photocurrent, dependent on T PI – insolation level in W/m 2 Isc1 – short circuit current at 1000 W/m 2 solar radiation The PV cell characteristics also depend on external factors including temperature and solar irradiation level. To incorporate these effects into the model, two additional relations are used. Output current varies with solar irradiation and temperature through [16]: (4.9) Where In: is the nominal PV cell output current (at 25 °C and 1000 W/m 2 ). KI: is the current/temperature variation coefficient (A/°C). ΔT: is the variation from the nominal temperature (25°C). Gn: is the nominal solar irradiation (1000 W/m 2 ). 51 The value of KI is relatively small and this makes the cell output current linearly dependent on solar radiation level more than temperature. Temperature, however, has a strong effect on the reverse saturation current, I0 in equation (4.10) Where Isc, n: is the nominal short circuit current of the PV cell. Voc, n: is the nominal open circuit voltage. KI and KV: are the current and voltage temperature variation coefficients, in A/°C and V/°C, respectively. A PV module is the result of connecting several PV cells in series to order to increase the output voltage. The characteristic has the same shape except for changes in the magnitude of the open circuit voltage. The PV array is composed of several interconnected photovoltaic modules. The modeling process is the same as the PV module from the PV cells. The same parameters from the datasheet are used. To obtain the required power, voltage and current, the PV modules are associated in series and parallel the number of modules connected in series and connected in parallel must be calculated the number of modules modifies the value of resistance in parallel and resistance in series. The value of equivalent resistance series and resistance parallel of the PV array are: (4.11) 52 (4.12) Nss - is the total quantity of modules within the series. Npp - is the amount of modules in parallel. After extending the relation current voltage of the PV modules to a PV array, the new relation of current voltage of the PV array is calculated in by [20]. (4.13) Where I0, Iph, Vt are the same parameters used for a PV modules. This equation is valid for any given array formed with identical modules. The photovoltaic array will be simulated with this equation. The simulation circuit must include the number modules series and parallel. Figure (4.7) shows the circuit model of the PV array. 53 Figure (4.7): Model structure of the photovoltaic array [19] 4.3 Simulink Modeling of the Photovoltaic Array The PV characteristics from data sheet are used to generate the file necessary for Rs, Rp and other parameters for the maximum power point. The initial setup is used to obtain the I-V curve characteristics of the PV array and show the maximum power point of the PV. The model of the PV is used with the boost converter to determine the performance of the maximum power point tracker. The model of the photovoltaic array has been implemented in Simulink as shown in figure (4.8). The temperature and the irradiance are specified. The simulation allows having the curve I-V and P-V characteristics. The Simulink model uses a current source and the value of the resistance in series and parallel of the PV. 54 Figure (4.8): Simulation of the PV module The number of modules in series and parallel are set with Nss and Npp. The Im result is used for the Simulink block as a current source to obtain the voltage and current delivered from the PV. Figure (4.9) shows the Simulink model for the reverse current saturation (Io) at the reference temperature which is given by the equation: (4.14) 55 Figure (4.9): Simulink modeling implementation for Io. Figure (4.10) shows the Simulink model for the light generated current of the photovoltaic cell which depends linearly on the influence of temperature and solar radiation as given by the equation: (4.15) Figure (4.10): Simulink modeling implementation for Iph. 56 Figure (4.11) shows the Simulink model for the model current Im which given by the equation: (4.16) Figure (4.11): Simulink modeling implementation for Im Figure (4.12) depicts the PV array modeling. Figure (4.12): PV array modeling. 57 4.4 Validation of PV Simulink Model In order to validate the PV model, I substituted the PV model parameters from a real PV module (MSX-50), then PV model simulated under different temperatures and radiations. As a result, I achieved the same curves from the simulation model and from data sheet PV module as shown in figure (4.14) to (4.19). Table (4.1): Electrical characteristics data of the MSX-50 solar at 25 °C, 1.5AM 1000W/m 2 taken from the datasheet Figure 4.13 depicts Validation of PV Module Model for Different Temperatures. 58 Figure (4.13): PV model simulation at different temperatures. Figures (4.14), (4.15) show the main effect of temperature on the PV module voltage by simulink and by data sheet, which decreases when the temperature increases. Figure (4.14): Simulink IV characteristic curves for different temperatures. 59 Figure (4.15): Datasheet IV characteristic curves for different temperatures. Figure 4.16 depicts Validation of PV Module Model for Different radiations. Figure (4.16): PV model simulation at different radiations. Figures (4.17), (4.18) show the main effect of radiation on the PV module current, which decreases when the radiation decreases. 60 Figure (4.17): Simulink IV characteristic curves for different radiations. Figure (4.18) shows the effect of temperature on the PV module power, which decreases when the temperature increases. Figure (4.18): Simulink P-V characteristic curves for different temperatures. 61 Figure (4.19) shows the effect of radiation on the PV module power, which decreases when the radiation decreases. Figure (4.19): Simulink P-V characteristic curves for different radiations. 4.5 Impact of Shading on I-V Characteristic Curve of Photovoltaic Module Solar PV panel is a power source having non-linear internal resistance. A major challenge in using a PV source containing a number of cells in series is to deal with its non-linear internal resistance. The problem gets all the more complex when the array receives non-uniform insolation. Cells under shade absorb a large amount of electric power generated by cells receiving high insolation and convert it into heat. This heat may damage the low illuminated cells under certain conditions. To relieve the stress on shaded cells, bypass diodes are added across the module. 62 The bypass diodes’ function is to eliminate the hot-spot phenomena which can damage PV cells and even cause fire if the light hitting the surface of the PV cells in a module is not uniform. The bypass diodes are usually placed on sub-strings of the PV module. This configuration eliminates the creation of hot-spots and enables the PV modules to operate with high reliability throughout their lifetime [20]. The destructive effects of hot-spot heating may be circumvented through the use of a bypass diode. A bypass diode is connected in parallel, but with opposite polarity, to a solar cell. Under normal operation, each solar cell will be forward biased and therefore the bypass diode will be reverse biased and will effectively be an open circuit. However, if a solar cell is reverse biased due to the a mismatch in short-circuit current between several series connected cells, then the bypass diode conducts, thereby allowing the current from the good solar cells to flow in the external circuit rather than forward biasing each good cell. In practice, however, one bypass diode per solar cell is generally too expensive and instead bypass diodes are usually placed across groups of solar cells. Figure-4.20 shows an outline of the bypass diode in a PV system. 63 Figure (4.20): PV modules with bypass diodes Blocking diodes are installed between parallel panel string and/or the entire array and the battery. They prevent current from flowing back into paralleled series strings or arrays that are acting as a power consumer, discharging all of the power produced by the other series strings and/or the power stored in the battery at night when the array is darkened. When the sun shines, as long as the voltage produced by PV panels is greater than that of the battery, charging will take place. However, in the dark, when no voltage is being produced by the panels, the voltage of the battery would cause a current to flow in the opposite direction through the panels, discharging the battery, if it was not for the blocking diode in the circuit. Blocking diodes will be of benefit in any system using solar panels to charge a battery. 64 Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required. Figure-4.21 represents each position of bypass diodes and blocking diodes [20]. Figure (4.21): Each position of bypass diodes and blocking diodes In figure (4.22) shows simulink model for two PV modules with series connection at variable irradiance at 1000 W/m 2 and 500 W/m 2 [21]. Figure (4.22): Two PV module with series connection at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab - Simulink. 65 The figures (4.23), (4.24) show the effect of shading in the I-V, P-V characteristic curve. Figure (4.23): I-V characteristics at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab – Simulink [Y- axis: current (A), X –axis: voltage (volt)]. Figure (4.24): P-V Characteristics at variable irradiance at 1000 W/m 2 and 500 W/m 2 , by Matlab – Simulink [Y- axis: power (watt), X –axis: voltage (volt)] [21]. 66 4.6 Maximum Power Point Tracking (MPPT) 4.6.1 Incremental Conductance Based Maximum Power Point Tracking (MPPT) As known from a Power-Voltage curve of a solar panel, there is an optimum operating point such that the PV delivers the maximum possible power to the load. The optimum operating point changes with solar irradiation and cell temperature. This thesis deals with Incremental conductance MPPT algorithm method due to its simple approach. In incremental conductance method the array terminal voltage is always adjusted according to the MPP voltage it is based on the incremental and instantaneous conductance of the PV module. Figure (4.25): Basic idea of incremental conductance method on a P-V Curve of solar module 67 Figure (4.25) shows that the slope of the P-V array power curve is zero at The MPP, increasing on the left of the MPP and decreasing on the Right hand side of the MPP. The basic equations of this method are as follows. = - At MPP (4.17) > - Left of MPP (4.18) < - Right of MPP (4.19) Where I and V are PV array output current and voltage respectively. The left hand side of equations represents incremental conductance of P-V module and the right hand side represents the instantaneous conductance. When the ratio of change in output conductance is equal to the negative output conductance, the solar array will operate at the maximum power point [22]. 4.6.2 Incremental Conductance MPPT Algorithm This method exploits the assumption of the ratio of change in output conductance is equal to the negative output Conductance Instantaneous conductance. We have, P = V I (4.20) Applying the chain rule for the derivative of products yields to ∂P/∂V = [∂ (VI)]/ ∂V (4.21) At MPP, as ∂P/∂V=0 (4.22) 68 The above equation could be written in terms of array voltage V and array current I as ∂I/∂V = - I/V (4.23) The MPPT regulates the PWM control signal of the dc – to – dc boost converter until the condition: (∂I/∂V) + (I/V) = 0 is satisfied. In this method the peak power of the module lies at above 98% of its incremental conductance. The Flow chart of incremental conductance MPPT is shown below [22]. Figure (4.26): Incremental conductance MPPT Flow chart 69 Chapter Five Techno - Economical Impact of PV On-Grid Systems 70 5.1 Determining the Cost of Producing One kWh from Grid Tie PV System The economic analysis used in this thesis is based on the use of life cycle cost, cost annuity (NIS/kWh) and economic impact of grid tie PV system. 5.1.1 Life Cycle Cost (LCC) The life cycle cost (LCC) is defined as the sum of the PWs of all the components. The life cycle cost may contain elements pertaining to original purchase price, maintenance costs, operation costs, and salvage costs or salvage revenues. A) Initial cost of grid tie PV system Initial cost includes purchasing equipment (PV-panels, grid tie inverter, transformer, wires and other components used in installation). Also includes labors and technicians costs for installation. These costs depend on the size and type of a component. All these costs are summed to give the overall initial cost. Initial cost = Σ Components cost + installation (5.1) Initial cost of photovoltaic modules PV-modules are available in different sizes and types, the size of PV is characterized by their peak watt at STC (rated power).The price of peak watt is the same for mono or poly crystalline, but the installation or Structure cost will differ depending on the installed PV area. The (NIS/Wp) will decrease as the size of module increases. 71 Initial cost of grid tie PV inverter The grid tie inverter available in different sizes and types .The price of the grid tied inverter depend on its capacity, efficiency, contain MPPT controller or not, protection and other parameters. Other initial costs Shipping costs and accessories needed for installation and system protection, wiring, rooms, should be also considered. These costs depend on the system size and vary with the kind of the project; if it for public use (may be land available free), or for private use. B) Operation and maintenance cost of grid tie PV system The operation costs considered are incurred after installation in order to run the system for a certain number of years (system life time). C) Salvage value The salvage value is considered as the value of the project elements after the system life time finishes. Figure (5.1) shows the cash flow which represents the initial, maintenance cost and salvages revenue. 72 Figure (5.1): The cash flow which represent initial, operational cost and salvage revenue 5.1.2 Economic Factors In order to calculate the equivalent uniform annual series (Aw) of cash flow in figure (5.1), the most important fact to remember is to first convert everything to a present worth. The life cycle cost of grid tie system = initial cost of PV system + present worth of maintenance and operation – present worth of salvage value. The life cycle cost of grid tie system = initial cost of the system + Operation and maintenance × (P/A, i, n) – salvage value × (P/F, i, n). The term A (P/A, i, n) is called the uniform-series present worth factor. This expression determines the present worth P of an equivalent uniform annual series A which begins at the end of year 1 and extends for n years at an interest rate i, and (P/A) can be found by equation (5.2): (5.2) The term F (P/F, i, n) is known as the single-payment present-worth factor, or the P/F factor. This expression determines the present worth P of a given future amount F after n years at interest rate i, and (P/F) can be found by equation (5.3): (5.3) In order to simplify the routine engineering economy calculations involving 73 the factors, tables of factors values have been prepared for interest rates from 0.25 to 50% and time period from 1 to large n values, depending on the interest value 10% and interest table in appendix (E). The equivalent annual worth AW is obtained with appropriate A/P, as follow: AW = PW (A/P, i, n) Then the energy unit price calculated from equation (5.4) (5.4) 5.1.3 Cost of Producing One kWh from Grid Tie PV System for Jericho Power Plant The price of the PV system and its installation are important factors in the economics of grid tied PV systems. These include the prices of PV modules, inverter, and all other auxiliaries as shown in table (5.1). The cost of installation must be taken into consideration. Table (5.1): Cost of elements and installation of grid tie PV system Component Material or Work Quantity Price($) Life time(Year) PV Cells / Modules 2610 280789 25 Power conditioners (Inverters) 3 107612 25 Supporting structure for PV modules 2610 154244 25 Connection boxes 30 107636 25 Collection boxes 3 17938 25 Substation equipment 1 14348 25 Total 682567 For the present PV system, the life cycle cost will be estimated as follows: 74 1- The lifecycle of the system components will be considered as 25 years. 2- The interest rate is about 10%. The initial cost of the PV system = PV array cost + inverter cost + installation cost. The initial cost of the PV system = 280789 + 107612 + (154244 + 107636 + 17938 + 14348) = 682567 $ The annual maintenance and operation costs are about 2% of initial cost which is equal to 13651 $/year, salvage value after 25 years is taken 15% from initial cost and it is equal to 102385 $. The life cycle cost of PV system is obtained by drawing cash flow as in figure (5.2): Figure (5.2): Cash flow of grid tie PV system for Jericho PV Power Plant The life cycle cost of PV system = 682567 + 13651 (P/A, i, n) – 102385 (P/F, i, n). PW = 682567 + 13651 (P/A, 10%, 25) – 102385 (P/F, 10%, 25). The factors in the above equation are taken from appendix (E): PW = 682567 + 13651 × 9.0770 – 102385 × 0.0923 = 797027 $. AW = PW (A/P, i, n) = 797027 (A/P, 10%, 25). 75 From appendix (D), the term (A/P, 10%, 25) is equal to 0.11017, then: AW = 797027 (A/P, 10%, 25) AW = 797027 × 0.11017 = 87808 $. The total energy yield from Jericho PV power station for the first year is equivalent to 480572 kWh. The cost of 1 kWh from the PV generator = 87808 $ / 480572 kWh = 0.18 $/kWh. 5.2 Evaluation the Economic Impact of Jericho Grid Tie PV System The following equation determines simple payback period which evaluate the economic impact for Jericho PV Power Station. SPBP = (5.5) Annual saving money for Jericho Power System = Output Energy per year × Feed in Tariff/kWh Saving = 480572 kWh/year × 0.19 $/kWh = 91309 $/year SPBP = = 7.5 Year 5.3 Levelized Cost of Energy (LCOE) Since the LCOE ratio computes the total cost of the facility during its cycle of life dividing it for the energy produced for the same time, first we need to specify the energy produced by the 300 kW of Jericho power plant we are considering for this analysis. In order to calculate the energy production for the whole lifecycle, the following values were considered (considering the irradiation characteristics of Palestine):  Peak power: 339 kWp 76  Performance Ratio (PR): 75 % (for the whole system)  Peak irradiation hours per day: 5,5 h Energy production can be calculated following the next formula: Energy (kWh/year) = Power (kWp) * Peak hours (PH/day) * 365 * PR (%) As a result, the energy produced yearly is about 510 MWh/year. The Global Horizontal Irradiation GHI is about 5.2 peak hours per day. Considering tilted panels, the number of peak hours per day increases to 5.5 according to PVGIS results. A 5.5 hours peak irradiation per day has a production ratio of about 1500 kWh/kWp. Considering the formula for calculating the LCOE ratio, for the case of the On ground PV installation described in the scenario proposed the following LCOE are obtained: Table 5.2 - On ground PV LCOE Costs from photovoltaic installations are not expected to vary as much as the CSP case in non-mature markets since this is a less sophisticated technology. Sensitivity analysis for this case considers a variation of +10% over the initial costs in order to obtain a range of LCOE. Results are showed at the next table: 77 Table 5.3 - On ground PV LCOE sensitivity analysis 5.4 Environment Impact of Grid Tie PV System In the long term, environmental benefits may be the most important reason for the implementation of grid-tied PV systems. The environmental impact of PV is small when compared with all nonrenewable energy sources. Coal plants produce huge quantities of CO2 as well as particulates and oxides of sulfur and nitrogen. Of course, CO2 is inherent in the combustion process and cannot be avoided. Scrubbers can reduce, but not eliminate sulfur and particulate emissions. Gas fired plants are cleaner than coal plants, but still produce greenhouse gases. Atmospheric emissions from nuclear plants are negligible, but radioactive waste is an incessant problem with no clear cut solution. The amount of CO2 produced from conventional source using fossil fuel is 0.7 kg for 1 kWh, so if I consider Jericho Power Plant as a case study the reduction of CO2 from energy yield 480572 kWh is 336.4 ton annually. [13] 78 Chapter six Performance Analysis of Jericho PV On- Grid System 79 6.1 Introduction of Jericho PV On-Grid System Jericho station is an example of integrating the PV systems into the medium voltage distribution network. Unlike the low voltage grid connected PV systems, Jericho station will be fed, in the grid, through a step up LV/MV transformer to supply the distribution network. Jericho station system has been designed and constructed as the grid- connected, with reverse power flow, and without storage batteries system. This thesis aims to provide an understanding of PV integration to the medium distribution network from technical point of view [25]. The description of Jericho PV On-Grid system is the following:  Rated Capacity = 300 kWp at 1 ,st stage, 550 kWp at 2 ,nd stage  Number of Modules = 2610, 115 W  Expected Yearly KWh = 422,000 kWh, Actual for the 1 ,st year = 552,657.8 kWh  Area of Installation = 13,000 m 2  Expected Amount of Reduction of Carbon Dioxide = 290.6 tons/year. 6.2 Elements of Jericho PV On-Grid System This project provides the Palestine with Photovoltaic Power Generation system of 300 kW output of grid tied type in Jericho. The system comprises of PV module 115 W × 2610pcs, Power conditioners 100 kW × 3 no. and Substation. The system generates power from sunlight and intended to supply 3-phase AC power rated 300 kW. One string consisted of 6pcs of PV modules in series supply rated DC 330 V, input to the power conditioner pass through 80 junction box and collection box. Power conditioner converts from DC power to 3-phase 3-wire 202 VAC power which to be synchronized with grid line, insulation transformer makes step-up to 3-phase 4-wire 400 V power and supply to load. When output voltage of PV module is raised by increasing solar irradiance, power conditioner automatically starts operation. When output voltage of PV module is fallen by decreasing solar irradiance, power conditioner automatically stops operation. Generated power and voltage are measured, indicated and recorded using by personal computer. And solar irradiance, air temperature and surface temperature of PV module are also measured, indicated and recorded [25]. 81 Figure (6.1): Jericho PV Station Single Line Diagram 6.2.1 PV System The PV system in Jericho station has a peak power of 300 KW. This system is built from the Thin-Film (Amorphous) Silicon solar panels from Kaneka Corporation. The datasheet of the solar panel which is used in designing this PV system is shown in table (6.1). 82 Table 6.1: Kaneka PV Module's Datasheet The base element in this system is 115 W module, every six modules in series represent a string of modules. The system separated into 30 blocks, each block consists of 10 kW of combination of PV strings. The block alone has 15 parallel strings and the block is connected to its own distribution board. A group of 10 blocks that have a power of 100 kW are connected to one DC/AC inverter of 100 kW. Briefly, the PV system is a group of 30 blocks where 10 blocks are connected to one inverter; each block consists of 15 parallel strings which are connected to a distribution board. The PV string consists of 6 PV panels which are connected in series [25]. 83 6.2.2 DC/AC Inverter As mentioned above, the station has three DC/AC inverters. The inverter which is used in this station has a rated power of 100 kW, table (6.2) shows the datasheet of the (P83B104R) inverter in grid connected operation mode. Table 6.2: Grid Connected Inverter Datasheet The three inverters are supplied by the DC power from the PV system which is divided into three parts in order to provide the DC power to the three inverters. Each part of this PV system as mentioned earlier above contains 10 groups; each group consists of 15 parallel strings, so each inverter is connected to 150 parallel strings at 6 panels in series per string. The output power from the inverters is 300 kW (AC) three phase at output voltage rated 202 V as shown in table (6.2) [25]. 84 6.2.3 Step-up Voltage Transformer Jericho station has two stages of transforming using two types of transformers; voltage transformer and distribution transformer. The usage of the voltage transformer is to raise the output voltage from the inverter from 202 V to 400 V. As we use three inverters, here we need a voltage transformer to each inverter. 6.2.4 LV/MV Transformer After raising the voltage to 400 V and in order to integrate the PV system to the medium voltage distribution grid, LV/MV transformer is needed. The main specifications of this transformer are; the voltage levels are from 400 V to 33 KV, the transformation is from Star connection to Delta connection and the rated output power is 630 KVA [25]. 6.2.5 Switchgear The switchgear limits the switching of the electric components in the system at the low voltage level, provides protection to the devices in the system throw circuit breakers and fuses and isolates the electrical sections of the system. The electrical protection at low voltage level is apart from fuses normally incorporated in circuit breakers, in the form of thermal, magnetic devices and/or residual current operated. The over voltage protection and under voltage protection are provided by specific devices like contactors and isolators. The low voltage systems of Jericho PV station need the switchgears to control the switching between the different devices, different supplying systems (PV and the grid) and to protect them from faults and damages. 85 6.2.6 Main Monitoring System In the main monitoring room at Jericho Solar Station, many screens which connected to the computer are observing all parts of the system through a special software acting like SCADA system which can managing control and observing the system and its parts. From this software system we can extract different type of reports (hourly, daily, yearly), about the system performance, generating units, voltages and currents, metrological data. 6.3 Performance Analysis of Jericho Solar PV Station From the main monitoring system at Jericho station different reports and data were collected per month and per day, and it’s attached in the appendixes, summary of some important information for this study in the next table (6.3) [25]. Table 6.3: Solar Station Data from 8/2012 – 1/2013 86 Unfortunately, the monitor system were not working from 2/2013 – 8/2013 due to technical malfunction. It was observed that there were differences between generated kWh units that were counted by the monitoring system at the station and the number of units that seen by the grid through the number of units that were counted by JDECO Meter, and this due to transmission and step up transformer losses. There are three transmission stages to deliver the generated energy units to JDECO M.V grid, and at each stage there are losses. Technical losses from the PV panels to the end point of the conditioner = (8.7% - 9.8%), and the total technical losses to JDECO grid = (9.5% - 11.4%). Figure (6.2): Generated KWh Units from Jericho Solar Station The next figure and table, depicts the number of KWh units generated by the solar station that were delivered and counted by JDECO grid, for a total 87 one year from 8/2012 – 8/2013, the total quantity of KWh units that were generated by PV solar station and delivered to grid = 480,572 KWh Figure (6.3): Monthly Average Solar Radiation in Jericho Station Table 6.4: Generated KWh Units from Solar Station that counted by Grid [25] Average losses percent = 10.5 %, and so the Total Generated Units from the Solar Station for the first year = 480,572 + (480,572 * 0.105) = 531,032.06 KWh. 88 Figure (6.4): Generated kWh Units from Solar Station that seen by Grid [25] 6.4 Environmental Impact Assessment for Jericho Solar Station The calculations of environmental impact assessment in this section are depending on three types of data:  Expected amount of energy generated by Jericho Solar Station according to the station designer and developer (JAIP) is equal to (422,000 KWh) [25].  The amount of generated energy from Jericho Solar Station by theoretical calculations is: (6.1) 89 The actual amount of generated energy units from Jericho Solar Station according to the real data that were gathered from the main monitoring system at Jericho Solar Station and from JDECO kWh meter from 8/2012 to 8/2013 is equal to 480,572 KWh. The previous data from JDECO are after discount of the losses which are approximately 10.5%, so this data are equal to 531,032 KWh [25]. The amounts of energy generated are shown in Table 6.5. Table 6.5: Amounts of energy generated by Jericho PV power plant Type Amount of Energy (KWh) Energy According to Station’s Designer 422,000 Energy Calculated (My Calculation) 478,953 Energy According to Readings at Jericho Station (Actual) 480,572 Energy According to Readings at JDECO (Actual) 531,032 The expected amounts of carbon dioxide emissions reduction according to the mentioned data are: 480,572 * 0.7 = 336,400 Kg of carbon dioxide per year. 6.5 Simulink Configuration of Jericho PV Power Plant Figure (6.5) shows the whole Simulink model, the simulation results for this system for different conditions are in (Appendix B). 90 Figure (6.5): Simulink model of Grid tie PV system [26] 6.6 Recommendation On the low voltage case study, the recommendation is to minimize the negative technical impact of the distributed PV generators on the conventional grid:  Using smart grid systems to monitor the grid performance hourly and control the energy exchange times to mitigate the negative impacts, and maximize the benefits.  Limiting the PV penetration level on the grid to 15% by the regulator for more safety.  Study a storage system on the grid to act as a buffering zone. 91  Limiting the penetration level of the grid tied PV system on the network (Feeder) to equal the minimum load of the feeder due to the potential rising of the voltage assuming no tap changing in L.V/M.V transformer. 92 Chapter Seven Conclusions and Future Scope of Work 93 7.1 Conclusions From this research it was shown that it is possible to accurately predict the power output from grid connected photovoltaic arrays by including the effect of temperature and solar radiation. Furthermore, it was shown that it is possible to adapt the size of models and the different PV system configurations which are applicable to a grid connected and modify it in such a way that important information about techno-economic performance of these systems can be obtained. Using this software Simulink program, and determined the effect of temperature coefficient and non-linear radiation term, the maximum power output from each PV system sizes and configurations can now be predicted with accuracy. This can be done, not only for a single unrealistic value of solar radiation, but under general operating conditions. Being able to accurately predict the power output is very important for increased growth in the deployment of photovoltaic systems. 7.2 Future Scope of Work After the completion of the simulation work, the scope is been identified as:  Build Simulink dynamic smart system with all parts and controller.  Study effects of switching & fault conditions for grid tied systems.  Analyze the policy of RE in Palestine regarding the impact of different FIT systems, also the break-even cost of RE in Palestine.  Analyze the impact of interest (i) or subsidies on the feasibility of RE systems in Palestine. 94 References [1] U.S. Emission Data, Environment Energy-Related Emission Data & Environmental Analysis, Energy Information Administration, http://www.eia.doe.gov/environment.html [access date 5-12-2013] [2] Energy Research Center (ERC) Meteorological measurements in West Bank /Nablus: An-Najah National University; 2011 [3] Shabbaneh R and Hasan A, 1997. Wind energy potential in Palestine. Renewable Energy, Vol. 11 No. 4. [4] Palestin