Charging Electric Cars from Solar Energy

Charging electric cars from solar energy

Xusheng Liang Elvis Tanyi Xin Zou

Supervisor: Dr. Erik Loxbo Examiner: Dr. Sven Johansson

Department of Electrical Engineering Blekinge Institute of Technology Karlskrona Sweden 2016

Abstract Until now vehicles heavily relied on fossil fuels for power. Now, these vehicles are rapidly being replaced by electric vehicles and or plug-in hybrid electric cars. But these electric cars are still faced with the problem of energy availability because they rely on energy from biomass, hydro power and wind turbines for electric power generation. The abundance of solar radiation and its use as power source in electric cars is not only an important decision but also a necessary condition for eradication of environmental pollution This study presents a model for charging electric cars from solar energy. Little focus on detailed technologies involved from solar energy capture to battery charging but our main focus is how to provide a modified charging parking lot in Karlskrona city-Sweden .With a surface area of 2900sq. m, we were able to choose mono crystalline 1STH-350-WH as the right PV modules. Based on the latitude of our design area, a computed result of 71 degrees angle positioning between solar panel and roof so as to maximise the surface area and optimise the solar irradiance gathering. Based on the maximum power output of approximately 294kW these PV modules generate, we further analysed and selected SDP 30KW inverter, PWM controller SDC240V-100A and the AGM (BAT412201080) lead acid storage batteries. Also we provide different car charging method by choosing the SAE J1772 standard as one of specifications for dedicated vehicle charging and Clipper Creek HSC-40 as our option of charger. With the data of the generating solar energy every day, charging time, consuming power, we can estimate how many cars the system can handle, and how many electrical vehicles can be charged. Then we can decide whether we need to use the electrical power from the external power grid. We finally concluded that, our model is able to generate at least 136kwh daily energy output in winter, average 823.2kwh daily energy output throughout a year in theory and it can charge up to 27 electrical vehicles at once with an average full charging time of up to 6.2 hours. Our model for charging of electric car batteries is not only supportive but efficient in terms of extracting solar energy from sunlight to charge electric cars, thus making the region an eco-friendly place.

Keywords: AC Net, Converter, Controller, Electric Car, Photovoltaic, Solar Energy, Solar Panel, Storage Battery, Solar Irradiance, System design

Acknowledgements

We are heartily thankful to our supervisor Dr. Erik Loxbo whose continuous critics, encouragements, guidance and support from the start of our work till the final level. His support enabled us to understand not only the research area but also the scope of our degree program in practical perspectives. Also we dully acknowledge the concern and time put in by some of our programme mates, friends and closes ones to make it a success. Finally we wish to acknowledge our program director (examiner) DR. Sven Johansson and all the other teachers for both the theoretical and practical skills they impacted on us and thus which enabled us in achieving our task.

Contents

Abstract ...... 2 Acknowledgements ...... 4 Contents ...... 5 List of figures ...... 7 List of tables ...... 8 List of symbols ...... 9 List of acronyms ...... 11 1 Chapter: Introduction ...... 12 2 Chapter: Background Theories ...... 14 2.1 Reviews Based on Topic of Study ...... 14 2.2 Review Based on System Design ...... 15 2.2.1 The Solar Panel System ...... 16 2.2.2 The Micro Controller ...... 17 2.2.3 Storage Bateries ...... 17 2.2.4 Solar Inverters ...... 18 2.2.5 The Vehicle Charger/ AC Net ...... 18 3 Chapter: Aim and Objective Statement ...... 19 3.1 Problem Statement ...... 19 3.2 Aim & Objective Statemnt ...... 20 4 Chapter: Solution ...... 21 4.1 Brief Description of the System Design ...... 21 4.2 Description of solar panel ...... 22 4.2.1 Types of solar cells ...... 22 4.2.1.1 Crystalline Silicon cells(c-SI): ...... 22 4.2.1.2 Thin-Film Photovoltaic/Solar cells (TFPC/TFSC): ...... 24 4.2.1.3 The third generation / Emerging photovoltaics ...... 26 4.2.2 Calculation ...... 33 4.2.2.1 Illumination time ...... 33 4.2.2.2 The PV modules Installation ...... 35 4.3 Description of controller ...... 45 4.3.1 Different Types of Charge Controller ...... 45

4.3.1.1 MPU Controllers ...... 45 4.3.1.2 Pulse Width Modulated (Pwm) ...... 45 4.3.1.3 Maximum Power Point Tracking Controller ...... 46 4.4 Description of storage battery ...... 53 4.4.1 Storage batteries ...... 53 4.4.2 Lead acid storage battery ...... 53 4.4.3 Lithium Ion storage battery ...... 54 4.4.4 Flow battery ...... 54 4.4.5 Connection of battery packs ...... 60 4.5 Inverter ...... 63 4.5.1 Description of inverter ...... 63 4.5.1.1 String inverters ...... 63 4.5.1.2 Micro Inverters ...... 63 4.5.1.3 Power Optimisers ...... 64 4.6 Utilization of electricity from general AC netwok ...... 66 4.7 Description of vehical charger ...... 67 4.7.1 Specification of the popular electrical vehicle battery ...... 67 4.7.2 Selection of charging mode ...... 70 4.7.3 SAE J1772 standard charger ...... 71 4.7.4 General Swedish power output analyzes...... 75 4.7.5 Charging time and consuming power ...... 76 4.7.5.1 Charging time and consuming power using SAE J1772 level 2 charging ...... 76 4.7.5.2 Charging time and consuming power using general socket 79 4.7.5.3 Chargers arrangement ...... 80 4.8 Installation cost ...... 81 4.8.1 Installation cost of our system ...... 81 5 Chapter: Conclusion and future work ...... 85 Reference ...... 86

List of figures

Figure 4-1 system structure ...... 21 Figure 4-2 monocrystalline silicon cell [45] ...... 22 Figure 4-3 polycristalline silicon cell [46] ...... 23 Figure 4-4 Thin-Film solar cell[47] ...... 24 Figure 4-5 A comparism of global market share for PVs[45] ...... 25 Figure 4-6 silicon based cell[47] ...... 26 Figure 4-7 Comparism Of Solar Cell Efficiencies And Choise For Our Research Project, solar cell efficiencies[53] ...... 28 Figure 4-8 the distance between the PV array a horizontal surface ...... 40 Figure 4-9 Connection pattern of each phalanx ...... 43 Figure 4-10 PWM controller SDC240V-100A,[69] ...... 50 Figure 4-11 AGM storage battery[77] ...... 54 Figure 4-12 Connection pattern of battery with the controller ...... 62 Figure 4-13 string inverter[85] ...... 63 Figure 4-14 Micro inverter[85] ...... 64 Figure 4-15 power optimizer[85] ...... 64 Figure 4-16 Utilization of electricity from general AC network ...... 66

List of tables

Table 4-1 Compares of Solar Cell Efficiencies and Choice for Our Research Project, Compares of solar cell efficiency [54] ...... 29 Table 4-2 Comparism of different Solar Panel Products Types [55] [56] [57] [58] ...... 31 Table 4-3 Illumination time ...... 34 Table 4-4 solar elevation and solar azimuth ...... 36 Table 4-5 the size of the PV modules [55] ...... 39 Table 4-6 the parameter of the PV module [55] ...... 41 Table 4-7 Monthly Averaged Insolation Incident on A Horizontal Surface (kWh/m2/day)[63]...... 42 Table 4-8 controller parameters ...... 47 Table 4-9 Detailed specification of the SDC240V-100A controller[73] .... 52 Table 4-10 Compare of the Different Battery Types for Solar Energy Storage [80] [56] ...... 56 Table 4-11 AGM batteries specification ...... 61 Table 4-12 Wikipedia-by Fraunhofer ISE 2014, from: Photovoltaic Report[86] [87] [88] [89] ...... 65 Table 4-13 Electrical Vehicle battery specification[90]–[116]...... 67 Table 4-14 Specification of SAE J1772 Standard Charging[119]...... 73 Table 4-15 HCS-40 electrical specification[120] ...... 74 Table 4-16 Standard power output in Sweden[121]...... 75 Table 4-17 Swedish General Plug Type Specification[122]...... 76 Table 4-18 Charging time and consuming power using SAE J1772 level 2 charging[90]–[116] ...... 78 Table 4-19 Electrical vehicle charging time and consuming power using general power socket[90]–[116] ...... 79 Table 4-20 Cost of system ...... 82

List of symbols

Symbol Quantity Unit PV Photovoltaic N W Watt J/s kW kilowatt 1000 J/s V Volt Φ Karlskona latitude ゜ δ Declination angle ゜ τ Hour angle ゜ h solar elevation ゜ γ solar azimuth ゜

휏휃 sunrise and sunset hour angles ゜ T duration of sunshine h n the number of days in a year day Z the installation inclination angle of the ゜ PV array l the distance between the solar PV arrays cm 퐶푂푃 the output capacity of each PV array Ah each day 퐶′푃푉 the value of the generation of all solar Ah PV arrays each day 푉푃푉 the work voltage of the solar PV array V 퐺′푃푉 the generation of the all PV arrays kWh Cw Capacity of battery pack Wh d Continuous days without sunlight Number of days D depth of the storage batteries discharge % level F Amending coefficient of discharge K Loss between the battery and the % electrical appliance Pm Peak power W QL Energy quantity can be delivered to the Wh electrical appliance

Tm Peak sun hours hours

List of acronyms

Acronym Unfolding AC Alternating current DC Direct current PV Photovoltaic

1 Chapter: Introduction

This project based on Charging Electric Cars from Solar Energy was carried out at the Blekinge institute of Technology Karlskrona-Sweden. Presently, developing new types of energy conversion and storage systems is becoming evident because of increasing human population and thus greater reliance on energy-based devices for survival. Due to the rapid increase in the world population and economic expansion geometrically, this is bringing about rapidly diminishing fossil fuels and the continuously growing environmental concerns as greenhouse gas emissions. Furthermore with the technological advancements in this modern era, more electronic devices are being used to replace manpower thus leading to a further increase in energy consumption. Energy obtained from the suns radiations when in contact with the earth’s atmosphere and or surface as irradiances is called solar energy. Presently, this is known by humans to be the prime renewable energy in existence till date, the energy produced in day is able of sustaining mankind even when traditional energy sources gets finished. This readily available environmentally friendly energy source can easily be obtain via series of methods as photovoltaic, solar thermal energy, artificial photosynthesis, solar heating and also solar architecture[1]. Research works have shown that at the core of the sun, the solar energy is in form of nuclear energy brought about by continues fusion between hydrogen and helium atoms each second. Thus as a result of this, it radiates out close to 3.8×1026 joules of solar energy each second[1]. With the free and abundant solar irradiances that provides enormous times more energy to the Earth than we consume, photovoltaic processes ensures that not only sustainable but greater efficiency and reliability to access electrical power for charging electric cars anywhere around the world without environmental pollution. With little upkeep, viable approach to self- charging of electric cars wherever need via photovoltaic processes. Solar energy thus provides a unique, simple and elegant method of harnessing the suns energy to provide electric power to electric cars thus taking the world much step closer to a greener community. Sweden being one of those unlucky countries with very little(or no) fossil fuel availability for extraction, coupled with the rapid increase in its

population [2], and also active cars in circulation [3] the demand for electricity so as to meet up the needs of the local masses is at an increase. With our focus area Karlskrona in Blekinge Region-Sweden, located at latitude/longitude: 56°09′41″N15°35′11″E, altitude: 18 m and also having and an average annual temperature of 7.8 degrees centigrade [4] ,our conceptual design based on harnessing solar energy to charge electric cars will not only make the region eco-friendly but also increase the solar energy availability but also encourage the masses to switch their choices from traditional cars to electric cars using solar electric power. The research work begins with a background study where related works were reviewed. Then, in chapter three, we present the problem statement, our objectives and main contributions. Furthermore, we present description of our system design and implementations in chapter four. In chapter five, we present our conclusion and (or) recommendations. Finally we end the work with references, appendices and list of figures.

2 Chapter: Background Theories 2.1 Reviews Based on Topic of Study

The negative impacts on climate change on humane lives is already being experienced and felt in most parts of the word. This has led to leading global economies (G 8) and other stakeholders stressing on the importance of renewable energies and immediate reduction of environmental pollutants. Other researchers argue that renewable energies do not completely stop climate change [5] whereas some stress that it’s not the only option but a necessary condition for a greener future [6].Apart from reducing climate change effect, renewable energies also have greater preferences to other energy sources. These renewable energy sources are not only reliable but also provide greater security due to their continuous availability [7] relatively cost effective than other traditional energy sources [8], and also creates more jobs and improves economic growth relatively [9]. Research work on how electric cars can be charged using both solar and wind energy has been going on in the past [10] [11].Here they based their idea on obtaining the various energy sources mainly by forecasting which depends on both time and weather of a particular location. That is they stated that forecasting the future weather conditions will give them the idea on what energy to generate and save for the car to use in future. But forecast based on climatic conditions is mostly never accurate or exact. So, this might bring about shortages or no energy to power the car. Building a design that conceptually show how solar energy can be easily harnessed, stored and utilise have not been fully researched on and also considered more realistic to operate. In the previous year’s series of authors have shared knowledge and ideas on how electric cars can be charged via the use of electricity from the grid which was generated from traditional energy sources as coal, fuel and hydropower [12] [13]. As more electric vehicles use the grid for power supply, it is decreases for power to be used for home consumption and other activities. This brings about imbalance in distribution thus providing poor power factor and power net instability. Though tighter controls are were put in place [14], using solar energy with unlimited power supply will serve as better option since electric cars will be encouraged more to be used and also providing greener environment. 14

Also, a handful of researchers have presented scholarly papers on how to use the optimal daytime charging strategy to charge electric cars using solar energy [15] since the solar irradiance is at peak during the day, they try to design an approach on how to fully maximize the energy falling on earth’s surface at peak hours. It’s an eco-friendly approach of energy harnessing using PV cells but they did not explain on how the excess energy will be shared and how energy will be obtained during periods of little or no solar irradiance. Our research work tries to explain how solar energy can be harnessed from PV cells to charge electric cars from parking lots thus providing room for excess energy storage during peak period and also energy reuse during low periods. Research on solar cells being integrated into electric vehicles to supply solar energy has been carried out in the past as well [16] , though they argued that the energy generated by the intergraded PV cells can be used only when the battery’s capacity is below optimum. Though it’s a sustainable approach, the capacity of the cars battery saturation point limits the solar energy capture of the cars PV setup. Also since the car mostly in motion, to optimise the energy capture will involve smarter and well advanced system embedded into the car, thus costly to operate.to reduce this complexity and cost is simply to use charging via solar panel from a parking lot which is easier and more convenient. Also some authors wrote on plug in hybrid electric cars [17] these cars are seen to use (consume) both petrol and electricity at rates that are based on the distance travelled and topology of the road. These cars not only increase environmental pollution but also costly due to their dual engines type. Furthermore since they are based on blended strategy in terms of their engine designs faults by one engine reduces the efficiency of the car to travel longer distances. The use of solar energy to charge electric cars is not only eco- friendly but secured.

2.2 Review Based on System Design

In this section we briefly state the framework and theories put forth by other researchers in line with our thesis work.

The conceptual design we developed guided us to understand the problems and thus providing a guide to solutions [18]. The design consisted of 6 sub-systems(solar panel, micro controller, storage battery ,inverters, AC Net and car battery showing how their specific and unique choices were linked to achieve our objective on charging electric cars using solar energy we concentrated on how to design modified parking and charging lots. Since this project describes conceptually how to charge a car using solar energy, on this section on literature review we will dwell on research works on each of the subsystems and how they are interrelated. 2.2.1 The Solar Panel System

The sun has been playing numerous roles in humane existence. Not only supplying energy and light to earth but also used to understand how the other areas of universe interact .With over 6.3*10^11 watts/sq. meter of solar radiation produced constantly in the form of rays.as these rays spread from the sun’s surface their intensity reduce and upon getting to planet earth the rays becomes parallel in nature [19]. Though most of the rays are being scattered, diffracted and deflected upon reaching earth’s surface [20] , it’s found that the total solar irradiance (insolation) that actually absorbed by earth annually is close to 3.8 million exajoule (EJ) [21] . Thus, solar energy doubles what is produced by all other non-renewable energy sources annually [22].This brings the abundance of solar irradiance reaching the earth’s surface for an hourly base unable to be harnessed by humans and other living organism for a year [23]. Photovoltaic being the interest of study, some authors stressed that the efficiently harnessed the solar intensity to provide the required solar energy to drive electric cars heavily relies on; not only the weather condition but location and time of day [24] the angle the solar irradiance makes with the solar panels [25], the material (and its temperature properties) used to design the PV panels [26], and also the aspect of PV surface area design [27] have to be fully considered.

2.2.2 The Micro Controller

Generating solar energy consist of harnessing the maximum irradiance at true solar noon. When the solar intensity is maximum, the electric car battery might be fully charged as well. To save this extra energy that is being generated photovoltaic charge controllers are needed to redirect the energy to storage battery cells. Series of microcontrollers used for photovoltaic were reviewed by other scholars. They did stress that importance of on and off, Pulse Width and Modulated (PWM) and Maximum Power Tracking micro controllers for increasing the efficiency of solar power generation. Stating that the on and off micro controllers operate both in series and shunt modes. Series controllers basically stop further charging when load is fully charged while shunt charge controller diverts excess electricity to other loads. On the other hand, Pulse width modulation (PWM) and maximum power point tracker (MPPT) technologies are more technologically sophisticated, and also adjusting charging rates depending on the battery's level, to allow charging closer to its maximum capacity [28]. 2.2.3 Storage Bateries

Batteries in solar applications ought to meet the demands of unstable grid energy, that is heavy charging and discharging cycles and also irregular full recharging. There’s a variety of battery types fitted for these unique requirements. Main subgroups of storage batteries for solar energies reviewed by others include flow batteries [29], lithium ion batteries [30] and lead acid batteries [31].Considerations for choosing a battery included the storage capacity which total energy actually stored with respect to that retrieved [32], power transmission rate which is time required to extract the energy stored [33], discharge time based on the maximum time the battery takes to discharge [34],efficiency as in implying rate of energy released to that stored as in [35], cycling capacity that’s the number of times that the battery discharges as designed after successively recharged [36] , cost based on both operational and investment expenses over the lifespan of the set storage battery [36] ,disposal effects considering the environmental impact of the storage battery after its life cycle completion [37] , and finally the self- discharge rate of the battery in that the rate at which the battery discharges while idling [38] .

2.2.4 Solar Inverters

The energy harnessed by the solar panels is basically DC. For this to be used in charging the electric cars or other automobile devices, it has to be converted to AC current. Solar inverters converts these DC to AC before charging begins, or the current being channelled to off grid electrical networks. Thus they have special function in photovoltaic system based on energy conversion and balanced. The various types and specifications have been deeply researched on such as string inverters where panels are placed parallel with central inverter [39], micro inverters in which solar panels placed serially with separate inverters [40] and also power optimizers similar to micro inverters but more involved with monitoring. Power optimizers are used to monitor the total output of the PV panel arrays so as to continually adjust and modify the load attached in order the keep the system operational at its peak [40]. 2.2.5 The Vehicle Charger/ AC Net

The converted AC current has to be supplied to the power grid or charging units for the electric cars. Charging of electric cars here based on specify car and battery types, charger specifications and also the specification of the socket. In Sweden the standard is 230V, 16A but the power varies with design setup. Our choice for the electric car battery charging unit based on the standard set up by the required authorities. We also took measures on the car design and power consumption rates. All these are based on the power generated from the PV panels. Based on our respective sub analysis of the different systems within the conceptual design, we do believe a well-integrated design linking the respective systems based on their optimum efficiencies will make the Karlskrona region not a greener but saver region to live in based on environmental polluting avoidance

3 Chapter: Aim and Objective Statement 3.1 Problem Statement

There has been rapid increase in levels of oceans due to faster rate of ice melting in artic, coupled with fast desertification’s in other parts of the earth’s surface as a result of continues increase in global climate as well. Looking at the rapid increase in world population and further increase in number of circulating cars, it’s found that more than 70% of environmental pollution is caused by cars using traditional source of energy for power [41] .With the climate change crises becoming a global issue, the continuous awareness created by learning institutions, government bodies and other stockholders have to be intensified and implemented [42]. Nowadays, with the global concern for greenhouse gases and environmental pollution, electrical vehicles are being developed in quick paces for both private and commercial purposes. At daily use of these cars, users have to charge the battery of the car once they run out their battery in the charge station. It takes not short time to fully charge their car. During charging, user cannot only use their cars but the process creates an imbalance in power distribution in the grid. Thus it causes poor power factor and power net instability to other third parties using the grid. Furthermore, some electric car owners still face the problem of charging their electric cars in some charging station because of incompatibility between their car batteries and the charging stations charger. Thus the question of how to charge electric cars from solar energy has become an important and necessary link to solve these environmental issues.

3.2 Aim & Objective Statemnt

The main aim of this research work is to provide a system model that can be used to brainstorm both innovative ideas and solutions to current problems in the research area and also to serve as eye opener for future research design and development. Also, it can provide an efficient, effective and sustainable system based on using photovoltaic as a better renewable energy source to charge electric cars. The main objective of our research work is to outline a conceptual design based on how solar energy from sun (photovoltaic energy) can be used for charging electric vehicles. We also wish to explore conceptually how existing parking lots can be modified into solar energy charging points for charging the cars. Furthermore, we explored ways on how the PV panels will be placed on the roof of the parking lot, choice of the various components to convert and channel the harnessed solar energy to storage battery cell and to charging points and also the specification of the charging system for both the car battery and electric charger. Finally we explore how the design can be implemented in Karlskrona in our study area.

4 Chapter: Solution 4.1 Brief Description of the System Design

System designs are basically structured and modelled representation of actual systems that show the various steps and components involved achieving stated goals. These designs also guide researchers to understand the problems and thus providing a guide to solutions as in [18]. Our design is presented in Figure 4-2. consisted of 6 sub-systems(solar panel, micro controller, storage battery ,inverters, AC Net and car battery).it clearly shows how each of these subsystems are linked to each other furthermore in each subsystem we clearly analyse the various product components and how our specific choices were made to achieve our objective on charging electric cars using solar energy. The next part of the research work presents detailed analysis of each of these subsystems.

AC Network

Kwh DC DC Solar Panel Controller Converter

Charging DC Discharging General socket

Storage Battery SAE J1772 charge Vehicle Charger

Figure 4-1 system structure

4.2 Description of solar panel

4.2.1 Types of solar cells

4.2.1.1 Crystalline Silicon cells(c-SI): These cells produced initially in the 1950s and till date they are most useful and dominant semiconductor material used nowadays in most photovoltaic solar cells production [43]. Crystalline silicon solar cells comprise of different forms but differentiated by their respective purity degrees. That is, when the silicon molecules are well aligned ,it gives that particular silicon a better preference over others because solar cells made of that specie will effectively convert the solar energy into electricity [44]. Crystalline silicon consist of two types; mono and polycrystalline and String Ribbon silicon cells. Monocrystalline Silicon solar cells consist of cylindrical ingots and four sites cut to make silicon wafers. This not only reduces cost but optimize the performance of the ingots as well. Also, the crystals have a higher power efficiency rate of up to 20%, smallness in sizes so space efficient and a longer lifespan of above 25years[45]. Though they have significant edge over other silicon solar panels, they are relatively costly, more fragile and extreme variation in weather temperatures quickly affects its efficiency.

Figure 4-2 monocrystalline silicon cell [45] On the other hand, polycrystalline (p-Si)/multi-crystalline silicon solar cells (mc-Si) consist of squared ingot wafers. They are less fragile, lower production cycle and slightly lower heat tolerance factor compared to

monocrystalline solar panels. But, they do have an efficiency of power generation below 20%, a lower space efficiency and less attractive in terms of market values.

Figure 4-3 polycristalline silicon cell [46] While String Ribbon solar cells is another form of multi crystalline silicon cell production introduced by Evergreen Solar Company. Here high temperature resistant wires are pulled through molten silicon to produce polycrystalline ribbon of silicon crystals. It’s less costly than monocrystalline because its production requires half the amount of silicon as compared to monocrystalline manufacturing, but it’s inefficient and ineffective because of lower power efficiency value compared to polycrystalline, and also due to its lower space efficiency.

4.2.1.2 Thin-Film Photovoltaic/Solar cells (TFPC/TFSC):

Figure 4-4 Thin-Film solar cell[47] This solar cell consist of: Organic photovoltaic cells (OPC), Copper indium gallium selenide (CIS/CIGS), Amorphous Silicon (a-Si), Cadmium Telluride (CdTe). They are basically the second generation of solar cells obtained by the deposition of thin layer(s) of photovoltaic material on a substrate. Its uniqueness includes simplicity in large scale production, flexibly in terms of handling and space, and little impact on weather extremities on its performances. Whereas, space installation is a factor, low power output compared to monocrystalline cells coupled with shorter lifespan makes it lower in terms of preference. Cadmium Telluride(CdTe) is found to be the only thin-film solar panel that has exceeded the cost efficiency of silicon solar panels with an efficiency of solar panel being 9-11% [48] .it also has the smallest or lowest energy payback time [48] .though it has high efficiency and lowest energy pack back time, its high cost of obtaining the tellurium component and also high toxicity of cadmium makes its preference uncertain [49]. Furthermore, Amorphous Silicon (a-Si), basically used in small scale power harnessing, consist of low-cost substrate and very little silicon material which is nontoxic. It absorbs wide ranges of light spectrum thus functions well in almost all hours of days and irrespective of temperature variations. But its power output is very small(though can be improved by stacking) and also it has a shorter effective lifespan of less than a year [50].

Copper indium gallium selenide (CIS/CIGS) having a lab efficiency of above 20%, it uses an absorber consisting of copper, indium, gallium and selenide.it is produced via a process of vacuum extraction and co-evaporation and sputtering. Presently most promising with respect to the others [48]

Figure 4-5 A comparism of global market share for PVs[45]

4.2.1.3 The third generation / Emerging photovoltaics

Figure 4-6 silicon based cell[47]

These are a group of thin-film photovoltaic that uses both inorganic and organometallic materials. Presently they still possess lower efficiencies and lifespan still shorter as well. This includes; Copper Zinc tin sulphide solar cell (CTZTS), Dye-sensitized solar cell, Polymer solar cell, Quantum dot solar cell, Perovkite solar cell, amongst all listed above, the Dye –sensitized solar cell has the highest solar conversion efficiency with about 11% because they are built with only thin layers of conductive plastic in front layer, thus this allows them to radiate some heat away easily and quicker. Thus, suitable for lower internal temperatures[51]. Unlike fragile silicon cells that are protected from external surfaces via glasses and which increases internal temperatures of the silicon cells causing a drop in efficiency. Despite the proses of dye solar cells, the use of liquid electrolyte leads to environmental temperature stability issues because at extremely cold temperatures, the electrolytes freezes and power generation stops while higher temperatures can cause the liquid expansion and destruction of cell internal designs as well. Base on figure 4-7 below that shows the comparism of solar cell efficiencies and choice for our research project, we found that multi-junction cells do have the highest energy efficiency conversion rates as compared to the other cell types. But due to their high cost of production and installations[52],we could not integrate into our system. Presently they are mostly applied in astronomical applications as satellite launching. So, we are left with a choice based on silicon, thin-film and third generation photovoltaic cells as in table 4-1. Table 4-1 shows a Comparism of solar cell efficiencies and choice for our research project based on a confirmed terrestrial cell and sub module efficiencies measured under the global AM1.5 Spectrum. From the table we clearly found that silicon cells do have relatively higher cell efficiency and fill factor as well. Thus, it is a better choice for our research work.

Figure 4-7 Comparism Of Solar Cell Efficiencies And Choise For Our Research Project, solar cell efficiencies[53]

Table 4-1 Compares of Solar Cell Efficiencies and Choice for Our Research Project, Compares of solar cell efficiency [54] TITLE CONFIRMED TERRESTRIAL CELL AND SUBMODULE EFFICIENCIES MEASURED UNDER THE GLOBAL AM1.5 SPECTRUM (1000 W/M2) AT 25 °C (IEC 60904-3: 2008, ASTM G-173-03 GLOBAL).

CLASSIFICATION EFFICIENCY (%) AREA(SQ.CM) VOC(V) JSC(MA/SQ.CM) FILL FACTOR (%) SILICON: Si(crystalline) 25.6 ± 0.5 143.7 (da) 0.740 41.8 82.7 Si(multi-crystalline) 20.8 ± 0.6 243.9 (ap) 0.6626 39.03 80.3

Si(thin transfer submodule) 21.2 ± 0.4 239.7 (ap) 0.687 38.50 80.3 Si(thin film minimodule) 10.5 ± 0.3 94.0 (ap) 0.492 29.7 72.1 111 V CELLS:

GaAs (thin film) 28.8 ± 0.9 0.9927 (ap) 1.122 29.68 86.5

GaAs (multicrystalline) 18.4+-0.5 18.4 ± 0.5 4.011 23.2 79.7 InP (crystalline) 22.1 ± 0.7 4.024.02 0.878 29.5 85.4 THIN FILM CHALCOGENIDE: CIGS (cell) 20.5 ± 0.6 0.9882 (ap) 0.752 35.3 77.2 CIGS (minimodule) 18.7 ± 0.6 15.892 (da) 0.701 35.29 75.6 CdTe (cell) 21.0 ± 0.4 1.0623 (ap) 0.8759 30.25 79.4 AMORPHOUS/MICROCRYSTALLINE Si (amorphous) 10.2 ± 0.3 1.001 (da) 0.896 16.36 69.8 Si (microcrystalline) 11.4 ± 0.3 1.046 (da) 0.535 29.07 73.1 DYE SENSITISED: Dye 11.9 ± 0.4 1.005 (da) 0.744 22.47 71.2 Dye (minimodule) 10.0 ± 0.4 24.19(da) 0.718 20.46 67.7 29

Dye (submodule) 8.8 ± 0.3 398.8 (da) 0.697 18.42 68.7 ORGANIC: Organic thin-film 11.0 ± 0.3 0.993(da) 0.793 19.40 71.4 Organic (minimodule) 9.5 ± 0.3 25.05(da) 0.789 17.01 70.9 MULTIJUNCTION DEVICES: InGaP/GaAs/InGaAs 37.9 ± 1.2 1.047 (ap) 3.065 14.27 86.7 a-Si/nc-Si/nc-Si (thin-film) 13.4 ± 0.4 1.006 (ap) 1.963 9.52 71.9 a-Si/nc-Si (thin-film cell) 12.7+-0.4 1.000(da) 1.342 13.45 70.2 (da) = designated illumination area; (ap) = aperture area

Table 4-2 Comparism of different Solar Panel Products Types [55] [56] [57] [58]

TITLE Comparism of different Solar Panel Products Types [55] [56] [57] [58]

Classification Cost Power Vmp(V) Imp(A) Power Number Voltage Efficiency Temp Dimension (mm) rating(W) (%/Years) Coeff. (/Wp) Tolerance Cells (Vmax) (%)

Crystalline Silicon cells(c-SI):

M-Si $1.05 350 42.98 8.13 3 60 1000 16.22/25 -0.48%/K 1652*1306*50 (1SolTech 1STH-350-WH (350W)

P-Si(JY250M) $0.05 250 29.6 8.45 2 72 1000 15.3/25 1650*992*40

String Ribbon $1.05 210 18.1 11.05 5 - 600 13.4/25 1650.5*951.3*46 (Evergreen 210 W, ES-A Series)

Thin-Film Photovoltaic/Solar cells(TFPC/TFSC): [59] [60] [61]

CIS/CIGS(BP- $1.76 380 31.5 12.06 5 75 1000 16.6/25 (-40 to 2598*1000*17mm M-F380 CIGS) 85ºC) a-Si/(OYD-250) $0.54 250 38 8.54 3 60 1000 17/25 –40˚C to 1640*990*40 -0.6 85˚C)

CdTe(DM 77W $0.86 80 16.8 4.58 - - 1000 12/25 -0.21(Pm) 1200*6000*6.8 CdTe-2)

The third generation / Emerging photovoltaics[62] dye solar cell SI- $0.6 250 30.30 8.25 -0.03 60 1000 15.37/25 -0.45%/°C SPM250W 1650*990*50

156*156(cell)

Based on the data obtained from Table 4-2 above, we decided to choose the silicon crystalline solar (Specifically 1STH-350-WH solar panels) panel to design the solar panel. this is due to the fact that is has an efficiency of more than 25% with over 41 J in terms of power generated per square meter. Furthermore, with a fill factor of over 82 %( that is ratio of the solar cells actual power output to its dummy output) over an area of 143.7 sq. metre. [27]. 4.2.2 Calculation

4.2.2.1 Illumination time Because of the high latitude in Karlskona, the disparity of duration of sunshine is large, in order to increase the role of solar PV modules, we have to know the illumination time by calculating the declination angle of the sun, and calculate the solar elevation and the solar azimuth to decide the distance between each PV panels, in order to make each component can exposure to the sun fully and completely to increase utilization. Then according to the karlskona latitude to adjust the inclination of the solar panels, make the sunlight vertical irradiate on the solar PV modules as much as possible, to make the radiation reaches the maximum, increase power output. First, we seek the latitude of Karlskona the map. Karlskona latitude Φ=56.16゜ Then, we collect declination angle of some few special dates and whole summer. According to those data, we can calculate the declination angle1, 284+푛 δ = 23.45° × sin(360° × ) 365 Where n is the number of days in a year. Then Sunrise and sunset hour angles,

cos τ휃 = − tan 휙 tan 훿

1 angle between the sun rays and earth equatorial plane

or −1 휏휃 = cos (− tan 훿 tan 휙)

휏휃 is the angle of sunrise or sunset; positive angle is at sunset, negative angle is at sunrise. Following other data, then we can calculate the duration of sunshine with any season, any day length latitude.

Duration of sunshine 2 2 Τ = cos−1(− tan 훿 tan 휙) = 휏 15° 15° 휃

Table 4-3 Illumination time the the illumin angle angle n(d δ 휏 ( ation data cos휏 휃 of of ay) (゜) 휃 ゜) time sunris sunset (hour) e(゜) (゜) karls - kona 2010/3 0.0 89. 80 0.403 -89.44 89.44 12 /21 1 44 653 - 2010/6 23.44 130 - 173 0.6 130.38 17 /22 8046 .38 130.38 5 - latit 2010/6 23.18 129 - 181 0.6 129.77 17 ude /30 4489 .77 129.77 4 - 2010/7 21.67 126 - φ= 195 0.5 126.42 17 /14 4617 .42 126.42 9 - 2010/7 18.67 120 - 56.16 210 0.5 120.33 16 /29 0488 .33 120.33 0

- 2010/8 14.74 113 - 224 0.3 113.17 15 /12 4488 .17 113.17 9 - 2010/8 9.599 104 - 239 0.2 104.66 14 /27 3972 .66 104.66 5 - 2010/9 0.0 88. 266 1.008 -88.54 88.54 12 /23 3 54 871 - 2010/1 0.6 49. 356 23.44 -49.72 49.72 7 2/22 5 72 457

Based on the Table 4-3, we know illumination time in one day; it will help us to calculate the average power in the whole year. 4.2.2.2 The PV modules Installation Next, in order to decide the distance between each PV panels, we should know about solar elevation and solar azimuth. First, hour angle τ = ωt It is defined as: at noon when τ= 0, every 1 hour plus 15゜, morning is positive, afternoon is negative. For example, at 10:00, t=2, τ=30゜, at 14:00, t=2, τ=-30゜ the solar elevation2, sin ℎ = sin 훿 sin 휙 + cos 훿 cos 휙 cos 휏 the solar azimuth3, cos 훿 sin 휏 sin 훾 = cos ℎ

2 the angle between center of the sun light direct to the ground and the local plant, solar elevation angle is an important factor on the strength of the solar that ground can gain. 3 the angle between the projection of the sunlight on the ground plane and south of the local meridian, it means that it represents the sun position, decided the direction of the incident sunlight. 35

Table 4-4 solar elevation and solar azimuth

n(day τ data δ(゜) time h(゜) γ(゜) ) (゜)

12:0 - 0 0.000 0 2010/3/2 0 karlsko 80 0.40365 1 14:0 26.01 - na 3 -30 0 3 33.8209 12:0 57.31 0 0 2010/6/2 23.4480 0 7 173 2 46 14:0 60.01 - -30 0 5 66.6459 10:0 50.40 46.1759 30 0 8 2 12:0 57.05 0 0 2010/6/3 23.1844 0 3 latitude 181 0 89 14:0 50.40 - -30 0 8 46.1759 16:0 35.67 - -60 0 6 78.5652 10:0 49.04 45.1667 30 0 5 6 12:0 55.54 0 0 2010/7/1 21.6746 0 3 φ= 195 4 17 14:0 49.04 - -30 0 5 45.1668 16:0 34.45 - -60 0 6 77.4679 10:0 46.30 43.3150 30 0 8 5 12:0 52.53 0 0 2010/7/2 18.6704 0 7 210 9 88 14:0 46.30 - -30 0 8 43.3151 56.16 16:0 32.00 - -60 0 0 75.3814 10:0 42.69 41.1580 30 2010/8/1 14.7444 0 2 8 224 2 88 12:0 48.60 0 0 0 9

14:0 42.69 - -30 0 2 41.1581 16:0 28.93 - -60 0 1 73.1604 10:0 37.90 38.6853 30 0 0 6 12:0 43.46 0 0 2010/8/2 9.59939 0 1 239 7 72 14:0 37.90 - -30 0 0 38.6854 16:0 24.40 - -60 0 9 69.7061 12:0 32.84 - 0 0 2010/9/2 0 8 266 1.00887 3 14:0 27.89 - 1 -30 0 1 34.4632 10:0 27.5062 30 6.433 0 7 12:0 10.40 - 0 0 2010/12/ 0 1 356 23.4445 22 14:0 - 7 -30 6.433 0 27.5063 Different latitude, the sun irradiation direction angle of the sun to the ground is different, in order to obtain much more solar irradiance, the inclination of the PV array is different. It can be roughly achieved the installation inclination angle of the PV array depended on the local latitude: When =0~25, the installation inclination angle of the PV array is Z=; When =26~40, the installation inclination angle of the PV array isZ = ∅ + (5°~10°); When =41~55, the installation inclination angle of the PV array isZ = ∅ + (10°~15°); When =>55, the installation inclination angle of the PV array isZ = ∅ + (15°~20°). The latitude in Karlskona is ∅ = 56.16° Oblique angle Z=Φ+15゜=71゜

Because the oblique angle is too large, if we install it in a horizontal plane, it will be unstable, so we decide to mount it on the roof with the angle of 30 ゜.

Table 4-5 the size of the PV modules [55]

Length Width Manufacturer Model (in.) (in.) 1SolTech 1STH-350-WH 65.0 51.4 Now, we use the size of the solar PV module is 1STH-350-WH, its width is 51.4inch, is about 130.556cm. Before the installation, we should splice the solar PV modules into the solar PV array. We decide the total area of the roof of our car park is 50 * 58M, since the inclination angle is 41゜ , in order to prevent the solar phalanx broken for the large volume, I design to place on 10 * 4 solar phalanx, each phalanx consists of 3*7 solar PV modules. Considering about the 3*7 PV array is large, so we decide to put all of them on the roof, not to build them up, and use longer wires to connect with series and parallel. So W = 130.556cm. Using this data and the installation inclination angle of the PV array we can know the actual height of the solar panel H′. H′ = 푊푠𝑖푛푍 = 130.556푠𝑖푛71° = 123.4431푐푚 In order to make solar panels radiate heat, solar panels will be elevated 10cm 10 H = H′ + = 134.9905푐푚 퐶푂푆(30°) In order to make sure the solar panels can work well whole year, we adopt the data of solar elevation angle and azimuth angle on winter solstice (December 22) at noon, because this time the solar elevation is the lowest in whole year, at this time if the sunlight can shine on the PV modules shows that whole year achieve the requirement. At this time, according to the Table 4-4, we know:

h = 10.39527° 134.9905 L = H/tanh = = 735.8473푐푚 tan(10.39527°) γ = 0° D = Lcosγ = L = 735.8473cm

Figure 4-8 the distance between the PV array a horizontal surface a = Wcos71° = 42.50488cm ℒ = a + D = 778.3522cm ℒ푡푎푛ℎ b + ℓ = 푡푎푛30° + 푡푎푛ℎ = 216.716푐푚 푐표푠30° b = Wcos41° = 98.532cm ℓ = 216.716 − 98.532 = 118.1841cm So, at the end, we calculate the distance between the solar PV arrays is about 1.18m.

For the fixed installation in northern hemisphere, as long as setting in about south 20゜, the power generation capacity will not be affected any more. Considering about using in winter, the solar panels can be set south 20 ゜, the peak of the solar generation will appear in the afternoon, and this will help increasing the generation in winter. In conclusion, we will set the PV modules on a roof with 30゜, the installation inclination angle is 41゜, west 20゜, and the distance between the PV array is1.18m. The capacity of solar modules

Table 4-6 the parameter of the PV module [55] Rated Rated power Max. Max. power @ power power @ STC PTC voltage current Manufacturer Model (W) (W) (Vmp) (Imp) 1SolTech 1STH-350-WH 350 309.1 42.98 8.13

Table 4-6 is the parameter of the solar PV module 1STH-350-WH, according to our design about 3*7 solar PV modules, we can calculate how many energy each solar PV array provide. Frist, we should know about the output capacity of each PV array each day (Cop), it’s the product of the lowest monthly averaged insolation incident in a year and the maximum power current. Table 4-7 Monthly Averaged Insolation Incident on A Horizontal Surface (kWh/m2/day)[63]. Lat Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annua 56.16 l Avera Lon ge 15.58 22- 0.6 1.2 2.5 3.8 5.1 5.2 5.1 4.3 2.8 1.4 0.7 0.4 2.80 year 0 8 0 8 5 8 2 3 0 3 4 6 Avera ge

The lowest monthly averaged insolation incident in a year is 0.46 kWh⁄푚2

퐶표푝 = 0.46h × 8.13A = 3.7398A ∙ h

Figure 4-9 Connection pattern of each phalanx Figure 4-9 presents the connection pattern of each phalanx, the output voltage, output current and electric quantity can be calculated according this structure.

Then, we can calculate the generation of one solar PV array each day， the output power on each day multiply 3(parallel number) is the value of the generation of all solar PV arrays each day (C′PV),

퐶표푝 × 3 퐶′ = = 11.23063퐴 ∙ ℎ 푃푉 1.11 × 0.9

Where, 1.11 is the efficiency of charge the battery by solar PV modules; 0.9 is correction factors of the loss of PV modules caused by the attenuation of the solar PV modules and dust. So, all PV arrays can provide 12퐴ℎ every day. A ∙ h is the unit of the storage battery, so now we should count the voltage of the PV array to converted Ah into kWh.

Then, we will calculate the work voltage of the solar PV array (푉푃푉), it is the product of the maximum of power voltage and series number.

푉푃푉 = 42.98푣 × 7 = 300.86푣 The value of the work voltage of the solar PV array is 301V.

At the end, we can know the power of one solar PV array (푃푃푉),

퐺푃푉 = 퐶′푃푉 × 푉푃푉 = 3378.848푊 ∙ ℎ = 3.378푘푊 ∙ ℎ And we have 10*4 solar PV arrays in the roof, so they will provide about ′ 퐺푃푉 = 40 × 푃푃푉 = 135.154푘푊 ∙ ℎ

At the end, we calculated the generation of the all PV arrays is 136 kWh every day.

4.3 Description of controller

4.3.1 Different Types of Charge Controller

Microcontrollers or solar battery regulators are electronic devices used to regulate the flow of electric current or voltage between to electric batteries. Its basic functions involved preventing complete discharge or over charging of batteries so a main tool in protecting batteries life. The term charge controller or regulator may be referred to either a standalone device or an integrated circuit attached to the battery system. There are basically three sets of solar battery micro controllers; MPU controllers, Pulse Width Modulated (PWM) Controller, and Maximum Power Point Tracking Controller. 4.3.1.1 MPU Controllers These are the first generation of PV charge controllers performing one way operations. They involve the Series regulators, shunt charge controllers and the simple charge controller. Series regulators mainly disable further current from flowing into batteries when fully charged while shunt charge controllers diverts excess electricity from a fully charged battery to auxiliary load (loads). Furthermore, simple charge controllers basically stop to charge a battery when they exceed their specified voltage level and they further re- enable the charging process when the battery voltage gets below their specified minimum voltage levels [28] .some of the benefits of using on and off controller is that it’s very simple to operate, efficient with little heating, and also it operation help saves battery life since it prevent over and under charging of the battery. Recharging of battery by this controller is slower as compared to PWM controllers. 4.3.1.2 Pulse Width Modulated (Pwm) PWM basically uses higher voltage spikes in forwarding the charged current from the solar panels to the storage batteries. Some designs have output voltage pre-set so that they can be set for the particular battery in use.it also recharges batteries faster than on and off controllers.

One of the problems using the PWM controller is that most 12V units need at least 8V at the battery before they can function properly.so if a storage battery has been discharged below that value it will be difficult for the PWM controller to transfer the power irrespective of the amount being generated by the solar panels. Also some micron rollers have internal heat sink that reduces the total power from solar panels to storage batteries. 4.3.1.3 Maximum Power Point Tracking Controller It’s a micro controller set up to allow high voltage PV modules to charge batteries with lower voltage capacities. The controller indirectly hides the batteries from the PV solar modules thus supporting the batteries to operate at their optimum.in extreme climatic conditions, this controller still extract the most energy from the PV modules. Also it can operate efficiently even when it is separated some distance from the panels .The prime problem is that, in very low light levels such as early mornings or when sun sets, the controller might relay little or no power to the storage batteries.

Table 4-8 controller parameters

Floode Self- maximum working d Temp. paramet rated consu Full char Low- price charging tempera chargin compensati er voltage mptio ge cut voltage cut current ture g on type n voltage MPU controller [64] [65] SC4060/ $168 ≤ -25℃ -3MV/℃ 48V ≤50A 54.8V 43.2V 54.8V 50A .00 25MA ~+45℃ /CELL Sc4120/ ≤ -25℃ -3mv/℃ 48V ≤100A 54．8V 43．2V 54.8V 100A 50mA ~+45℃ /cell pulse width modulated controller [66] [67] [68] [69] WS- 12V/24 $28. <=30m 13.7V / 10.5~11V / -25℃ 17V / -3mv/℃ C2460(5 Vauto 50A 00 A 27.4V 21V~22V ~+55℃ 34V /cell 0A) work 12V/24 $60. -35℃ KT1215 Vauto 15A <5mA 13.2V 12.6V 13.8V NO 00 ~+55℃ work 12/24V 13.7/27. auto 4V 12.6/25.2V $26. ≤ -40℃ 13.8V/ -3mv/° SR-50 matic 50A recogniz recognize 00 45mA ~+60℃ 27.4V C/cell volt e tacit tacitly age ly

$2,5 - SDC240V ≤10 ＞285V± -3mv/° 00.0 240v 100A 210V 25℃ ～ 405.0V -100A mA 2 C/cell 0 +60℃ maximum power point tracking controller[70] [71] [72] ≤ 20mA( 12V/24 Tracer4 $169 12V) -25℃ Vauto 40A 14.6V 11.1V 13.8V -3mV/℃/2V 210A .00 ≤ ~+45℃ work 16mA( 24V) 12V/24 V 1.4 IT4415N $422 /36V/4 -25℃ 45A ～ 11.1V 13.8V -3mV/℃/2V D .60 8V ~+55℃ 2.2W auto work refer DC14V~ the I-P- 14.2V- DC100V charge eSMART- （the top $150 /DC30~ ≤ -25℃ voltag 12V/24V 40A 110V 10.5V temperatur .00 DC100V 40mA ~+55℃ e of /48V(40 e-25℃） /DC60~ the A) *0.3 DC100V batter y

Following the Table 4-8 controller parameter, we choose the PWM controller SDC240V-100A, because the output voltage is higher than other controller, it is suitable for our batteries. There are three stages charging function to protect battery: constant current; constant voltage and flooded charging. Besides the basic function of controller, likes input short-circuit protection; input overcurrent protection, batteries and PV array reverse polarity protection, the controller has the function of restricting maximum input power of the PV array, make sure the array can’t be overload under any condition; it also can protect the batteries overcharge and over-discharge.

Figure 4-10 PWM controller SDC240V-100A,[69]

Table 4-9 gives the detailed specification of the SDC240V-100A controller.

Table 4-9 Detailed specification of the SDC240V-100A controller[73]

Model SDC240V-100A Rated battery voltage 240V Rated current of solar energy panel 100A Rated current of each solar energy panel 25A Maximum voltage of solar energy panel 440V Rated Power of the Solar Panel 24KW Number of solar energy panel array 4 circuits Method of working Working continuously Function Charging and control State display LED Protection class IP30 Operating environment Temperature:-10-40 ℃ Humidity≤80% Stopping charging voltage of 1&2 circuits solar Panel ＞285V±2 Resuming charging voltage of 1&2 circuits solar Panel ＜270V±2 Stopping charging voltage of 3&4 circuits solar Panel ＞290V±2 Resuming charging voltage of 3&4 circuits solar Panel ＜270V±2 Connection cable of provided battery(㎡) ＞20mm² Maximum no-load self-consume （MA） 300mA Voltage drop between solar energy panel and accumulator 2V Applicable altitude ﹤1000 m Product size 585*585*980mm

4.4 Description of storage battery

4.4.1 Storage batteries

For the impact of the solar energy to be felt, the storage batteries used in the respective solar applications and systems need to meet the demands of unstable grid energy. Thus, solar storage batteries are considered to be key components in stand-alone renewable energy systems so as to continuously store the supply energy harnessed during peak and low periods respectively. There’s a variety of battery types fitted for these unique requirements. Main subgroups of storage batteries for solar energies earlier reviewed included flow batteries[74], lithium ion batteries [75] and lead acid batteries[76]. Also, choice for the battery comprised of parameters such as; the storage capacity which total energy actually stored with respect to that retrieved [32], power transmission rate [33], discharge time [34], battery efficiency [35], cycling capacity [36], cost of the storage battery [36],disposal/environmental effects[37], and finally the self-discharge rate of the storage battery[38] . A brief presentation of each of these subgroups is presented below.

4.4.2 Lead acid storage battery

Also known as valve regulated (VRLA) battery, it comprises of; Gel, Absorbed Glass Mat (AGM) and flooded lead acid models. Flooded lead acid has a higher replacement/maintenance and disposal risk factor because of constant refilling of the evaporated electrolytes. But AGM and gel are recombinant in that they require little or no maintenance and filling since there is minimal evaporation of the electrolytes making them environmentally safer. Being cheaper than lithium Ion batteries, and also high capacity, higher efficiency and cycle life, lead acid storage battery performance makes them a better choice for solar energy standby.

Figure 4-11 AGM storage battery[77] 4.4.3 Lithium Ion storage battery

Presently the most common storage battery used in modern technology especially in smartphones. Its various forms consist of Iron phosphate, Nickel, Cobalt, Manganese storage models. Unlike lead acid storage battery types, they basically require low maintenance, low self-discharging, higher energy and capacity densities, and thus they can provide higher current outputs. Despite the above benefits, they are more expensive, higher aging rates, and they require a lot of protection in terms of voltage/ current balances [78]. 4.4.4 Flow battery

Flow battery for solar energy storage is consisted of basically redox vanadium and hybrid models. Still considered as an emerging form for solar energy storage and cost assumed to be cheaper than lithium acid in near future[79]. Flow batteries are considered to deliver optimal power supply since its electrolytes and electro- active materials are stored externally and separately. Though there is separation of reactive components, externally there is high cost of construction and environmental risk of spillage.

So from the tabular analysis as seen on Table 4-10 below and our investigations, AGM(BAT412201080) lead acid storage battery was selected for our research work

Table 4-10 Compare of the Different Battery Types for Solar Energy Storage [80] [56]

Temp Energ Pow Depth sensi y/ er/ Ene Capacit Volta of Design Cyc tivit weigh wei Self- Parameters/ rgy Price y Energy/v ge dischar life le y t ght discharge Dispo eff ($/kwh ol ratio Model (A ge (years lif ratio rat sal ) (V) (best (wh/l) (%) (%) /20h) ) e io (%) degre (wh/k (w/ e ) g) kg)

Lead acid batteries

T105-RE 70.0- 152 225 12 30-50 12 800 - 35.0- 180 70.0 3.0- High Flooded 92.0 .0- 20 ℃ 40.0 - 4.0 safety 100 - 80.0 measures 0.0 +70 1 ℃

AGM(BAT41220 92 387 220 1 30-80 7.0 - 200 - 4- 42 - < ISO 1080) 2 10.0 Cyc 25 ℃ 2 9001 quality les - standard @ +60 100 ℃ %

4 Can’t find the data for boxes with -. This is because the data available was not in line with our research work

GEL(BPG12- 90 150- 150 1 30-80 10.0 - 4- - - - <2 Moderat 24T) 180 (20 2 15.0 5.6 e safety hours measure rate (7.5A 10.8V))

lithium ion batteries [81] [82] [76]

Iron 92 7 60 3.2-3.3 12 6 200 - 80.0- 1400 >300 180A High phospate(BAT 9 .8 0Cycles 45 ℃ 120.0 (LFP safety 512600500) 7 @ 80% - -CB measures +70 12,8 ℃ /60)

Nickel,Cobal >91 9 20 2.7-4.2 4 8 0.75- 55 140.0 260- 5 80% Moderate t,Manganese 7 1.9 - 450 - safety 0 150.0 measure

Flow batteries[83] [84]

Redox(vanedi 80 no 100kw 48V DC 10 20- unlimit -40℃ 10.0 10 15- <150 environmen um cellcube price h 0 30 ed ~+50 -20.0 25 W tally FB 10-100) assume ℃ friendly & rental recyclable

Hybrid(UPS >94 no 6.0 12 5 3- 2500 0℃ ~ - 18 - (+/- >97% Premium price to 0 20. +40℃ (0.9 ) recycle DSP0.9 assume 300 0 power 405V rate, Li- Hybrid 10- rental factor DC ion low 500kVA) ) &(+/

5 Can’t find the data for boxes with -. This is because the data available was not in line with our research work 58

-) safety 300V level DC

4.4.5 Connection of battery packs

In order to figure out the connection pattern of batteries, we have to refer the specification of the controller, the PV modules, how they connect together and produce how much power. There are formulas describes the relationship between the solar panels phalanx and the storage battery pack. We will figure out the connection pattern base the formulas below. 푄 푑퐹 퐶 = 퐿 푤 퐾퐷

푄퐿퐹 푃푚 = 퐾푇푚

Cw is the battery pack capacity with the unit Wh; QL is the energy quantity which can be deliver to the electrical appliance; d is the number of continuous days without sunlight and we assume d=2 here; F is the amending coefficient 퐶ℎ푎푟𝑔𝑖푛𝑔 푞푢푎푛푡𝑖푡푦 of discharge (퐹 = ); K is the loss between the battery and 퐷𝑖푠푐ℎ푎푟𝑔𝑖푛𝑔 푞푢푎푛푡𝑖푡푦 the electrical appliance; D is the depth of the storage batteries discharge level, we suppose D=80% in our utilization of batteries; Pm is the peak power of each PV phalanx, a PV phalanx consists of 3×7=21 PV modules with 350W maximum power, thus

푃푚 = 350 × (3 × 7) = 7350푊;

Tm is the Peak sun hours, Tm=2.8 hours in average throughout a year according Table 4-7. According the two formulas above, we obtain that: 푃 푇 푑 퐶 = 푚 푚 푤 퐷 The storage battery pack should have the capacity for a PV phalanx bigger than: 푃 푇 푑 7350 × 2.8 × 2 퐶 = 푚 푚 = = 51450 푊ℎ 푤 퐷 80%

The voltage of each battery pack is same with the system voltage, 240V. Therefore we need 240 ÷ 12 = 20 Batteries connected in series to raise the voltage in the battery pack. 12V is the voltage of each battery. In the meanwhile, the capacity of each battery pack should be bigger than 퐶 51450푊ℎ C = 푤 = ≈ 214.38 퐴ℎ 푈 240 Table 4-11 describes the specification of different types of AGM batteries. And the capacity of the BAT412201080 is 220Ah, which is bigger than 214.38Ah, conforming our requirement of conserving the daily energy output of a PV phalanx. Therefore we do not need to connect the batteries in parallel in each battery pack to raise the capacity of each battery pack. Table 4-11 AGM batteries specification

12 Volt Deep Cycle AGM General Specification RES Article l x w x h Weight CCA Technology: flat plate AGM Ah V CAP number mm kg @0°F Terminals: copper @80°F Rated capacity: 20 hr discharge BAT406225080 240 6 320x176x247 31 1500 480 at 25°C Float design life: 7-10 years at BAT212070080 8 12 151x65x101 2,5 20 °C Cycle design life: BAT212120080 14 12 151x98x101 4,1 400 cycles at 80% discharge 600 cycles at 50% discharge BAT212200080 22 12 181x77x167 5,8 1500 cycles at 30% discharge BAT412350080 38 12 197x165x170 12,5 BAT412550080 60 12 229x138x227 20 450 90 BAT412600080 66 12 258x166x235 24 520 100 BAT412800080 90 12 350x167x183 27 600 145 BAT412101080 110 12 330x171x220 32 800 190 BAT412121080 130 12 410x176x227 38 1000 230 BAT412151080 165 12 485x172x240 47 1200 320 BAT412201080 220 12 522x238x240 65 1400 440 According the features that each controller has 4 circuits connecting with the battery packs, the rate current and rated voltage is 25A and 240V of each circuit, the input current and the input voltage for each battery is also 25A and 240V.

Table 4-19 present the connection of the batteries and the connection between the battery packs and the controller.

......

...... Controller

......

battery ...... 220Ah, 12V .

20 Battery pack 240V, 220Ah

Figure 4-12 Connection pattern of battery with the controller Since there are ten controllers handling all the electric energy output from the PV phalanxes, and each controller controls four battery packs charging and discharging. We need 10×4 = 40 battery packs to conserve the energy generated by the PV phalanxes. In other word, There are 40×20 =800 batteries in our system to conserve the energy.

4.5 Inverter

4.5.1 Description of inverter

Based on electricity generated by solar cells, there are three basic inverters or converters which convert the DC electricity from the solar panel to AC electricity that can be used to charge the cars both at home sockets or charging stations these converters includes, the string inverters or centralised inverters, micro inverters and power optimizers. 4.5.1.1 String inverters Involves arranging the solar panels parallel into sets of strings that relay the power they harnessed into a single inverter. Here the panels produce equal total power at higher voltages. This reduces cost of wiring and lesser internal losses of the harnessed energy leading to improved efficiency [39].

Figure 4-13 string inverter[85] 4.5.1.2 Micro Inverters Unlike string inverters, micro converters the DC electricity of each solar panel to the AC per panel- that is each panel is attached to a micro inverters and output of the several micro inverters are combined and fed into the electric grid of the home or load. Here any failure of one of the panels as a result of shadings, debris or snow lines does not affect the functionality of the other panels because each micro inverter harnesses maximum power [39].

Though individual micro inverters generally have lower efficiency values as compared to string inverters, their combined efficiency is increased due to the fact that every inverter / panel unit acts independently.

Figure 4-14 Micro inverter[85]

4.5.1.3 Power Optimisers Similar to micro inverters in that both systems attempt to isolate individual panels in order to improve the performance of the entire system. Power optimizers are used to monitor the total output of the pane arrays so as to continually adjust and modify the load attached in order the keep the system operational at its peak. This process is known as maximum power point tracking (MPPT) by use of a Smart Module [40].

Figure 4-15 power optimizer[85]

Table 4-12 Wikipedia-by Fraunhofer ISE 2014, from: Photovoltaic Report[86] [87] [88] [89]

Title Comparison of inverter

Type Power Efficiency Module Module Cell modules (%) Voc Ioc (W)

Fronius 6.6- 97 650 38 4 strings Primo 8.2 12.7K inverter

SDP 1-200K 94 240 136 4 30KW inverter

P350 350 99.5 1000 15 Up to Power 25 strings optimizer

To conclude based on our analysis on Table 4-12 above, we will adopt the SDP 30KW inverter due to its rated output power compatible to the energy produced by our solar panels and also output frequency range in line with that specified with the vehicle charger selected. We determine to use micro inverter in our research work because of its higher power output rate and also more flexible in that additional solar panels can be added, and monitoring done to access our power harnessing and consumption rates.

4.6 Utilization of electricity from general AC netwok

AC Network

kwh ......

General socket

SAE J1772 charge

Vehicle Charger

Figure 4-16 Utilization of electricity from general AC network Since the high latitude at Karlskrona, the solar radiation in the Karlskrona is much less than the districts at low latitude. Moreover, the illumination time is very short in the winter, PV module acquire little irradiation at these time. It cannot afford the daily requirement of the charging. We adopt the use of electricity from general AC power grid, in case the PV modules cannot provide enough electricity for daily charge by user. jointed straightway to the AC network and separate the general power circuit with the photovoltaic energy generation circuit. That is to say only SAE J1772 chargers in our system will use the energy generated by the PV modules; the energy the general sockets use is from the general AC network. Figure 4-16 presents a rough and simple structure of the use of the energy from AC network. At this case, when the storage batteries are detected in low level by controller and are about to run out of their energy, the system will turn off some unused SAE J1772 chargers to prevent either battery charge breaking off or batteries over discharging. Meanwhile, the system will notice the user to use the general socket to charge their vehicles.

4.7 Description of vehical charger

4.7.1 Specification of the popular electrical vehicle battery

In order to implement our charging system, we study several electrical vehicles, their batteries and how they are charged. Table 4-13 below gives the basic information about these. Table 4-13 Electrical Vehicle battery specification[90]–[116]. Battery Capacity( Model Charger Adapter type kW h) 3.5kW AC 10A 220V- onboard charger 240V Renault Fluence household lithium-ion 22 Z.E. Optional Zoe's charger; Chameleon charger (43 kW) SAE J1772 SAE J1772 public chargers.

Adapters to IEC 60309 5 PIN Red 16A/3- 11 kW AC phase (400 onboard charger Tesla Model S V) or IEC lithium-ion 90 P90D 60309 3 120 kW DC fast PIN Blue charger 32A/single- phase (240 V) or some other kinds of domestic adapter or general adapters

based on regions.

Optional CHAdeMO charger.

Super charger.

120v Toyota Prius 3.3kW AC lithium-ion household 8.8 Plug-in Hybrid onboard charger outlet;

SAE J1772 7.4kW AC SAE J1772 onboard charger BMW i3 lithium-ion Optional 22

Combo DC. DC fast charger 120V cord plugs into any household outlet; 3.3kW AC Chevrolet Spark onboard charger 240V lithium-ion 21.3 EV chargers; DC fast charger DC Fast Charge- capable (SAE Combo) adapters for domestic 3.3kW AC AC sockets onboard charger Mitsubishi i- (110-240 lithium-ion 16 MiEV V); 44kW DC fast

charger 15 A 240 V AC (3.6

kW)[2] on the SAE J1772-2009 inlet,

optional Chademo (max 44 kW 480 V DC[3]); Standard SAE J1772- 2009 connector 120/240 3.6 kW AC volts AC onboard charger Nissan Leaf lithium-ion JARI high- 24

voltage DC DC fast charger connector(5 00 volts DC 125A, CHAdeMO ) 6.6kW AC on SAE J1772 board charger Kia Soul EV lithium-ion 27

CHAdeMO DC fast charger 6.6kW AC Fiat 500e lithium-ion SAE J1772 24 onboard charger 120-volt charging Mercedes B- 10kW AC onboard lithium-ion cable; 28 Class Electric charger

SAE J1772 120V convenienc e charge Ford Focus 6.6kW AC cord lithium-ion 23 Electric onboard charger 240V Home Charging Station

SAE-J1772 charging cable in conjunction with a 3.6kW AC standard Volkswagen E- onboard charger domestic lithium-ion 24.2 Golf mains DC fast Charger socket;

Combined Charging System;

The table above lists the present popular electrical vehicles battery data. The capacity of these vehicle batteries is approximately 43kWh. 4.7.2 Selection of charging mode

According to Table 4-13, most electrical vehicle provides several kinds of charging mode. All these electrical vehicles generally support connecting household electric socket charging and SAE J1772 standard charging or DC fast charging. Among these charging modes, the DC fast charging is latest. It is supported by several vehicles, mode. In this mode, the charging rate has been raised to two to three times than AC charging. It realized that charging battery up to 80% in an hour. There are three main types of DC fast charging standard: CHAdeMO, Combined Charging Standard and Tesla’ Supercharger. However, although this DC charging technology has high efficiency, its consuming power rate is too high. If we implement the fast DC charging in our system, according the present CHAdeMO standard charger at least providing 40 kW power[117], we need to place more than 114 PV modules with 350w maximum power output to provide 40 kW power for one DC charger. And the total number of our PV modules in our system is 840. 350×840×2.8 With the = 823.2kWh theoretical daily energy output, it can 1000 823.2 only support a DC charger work for about = 20.58 hours each day. In 40 350×840 other way, we can only deploy ÷ 40 ≈ 7 DC fast chargers and 1000

provide enough power only if the PV modules work at the STC6. Obviously, it is not realistic to equip the DC charging in our system. Our system cannot handle so much power to the DC fast charger. In the table, it indicates all the vehicles support the SAE J1772 standard charging and general household socket charging. Therefore this two charging mode will be employed in our system. Regarding the general power socket in Sweden, we have to have one kind of power output conformed the Swedish standard and another kind conformed the SAE J1772 standard. Order to simplify the structure of our system, the energy the general socket use comes from the general AC power grid instead of coming from the PV modules. And using the general socket to charge vehicle is an alternative charging option in our system, it make the charge tasks still available when the system run out all of the energy in the storage batteries and there is no output from the PV modules in the same time.

4.7.3 SAE J1772 standard charger

“SAE J1772 (IEC Type 1) is a North American standard for electrical connectors for electric vehicles maintained by the SAE7 International and has the formal title "SAE Surface Vehicle Recommended Practice J1772, SAE Electric Vehicle Conductive Charge Coupler". It specifies the requirements of the charging system in many aspects, such as physic, electric, communication protocol, and performance[119]. Since this standard charging had been developed since early and has advantages such as price comparing to other standards, it has been used widely, most electrical vehicle in the market. In order to integrate this charging pattern in our solar charging system, we have studied the electricity parameter of SAE J1772 standard and create the required condition to install this charger. There are two level of charging of SAE J1772 standard.

6 “Standard Test Conditions (STC) are specified in standards such as IEC 61215, IEC 61646 and UL 1703; specifically the light intensity is 1000 W/m2, with a spectrum similar to sunlight hitting the earth's surface at latitude 35°N in the summer (airmass 1.5), the temperature of the cells being 25 °C”[118]. 7 Society of Automotive Engineers 71

Table 4-14 below gives descriptions of these two levels of charging.

Table 4-14 Specification of SAE J1772 Standard Charging[119]. Voltage Phase Peak current Power AC Level 1 120 V Single phase 16 A 1.92 kW 32 A (2001) 7.68 kW AC Level 2 240 V Split phase 80 A (2009) 19.20 kW

Nowadays, almost all the electrical vehicle supports the SAE J1772 level 2 charging mode, and level 2 charging rate is much higher than level 1 charging. Therefore we will integrate this charging mode in our system based on the specification indicated in

Table 4-14. In order to implement our charging electrical network, we have chosen a certain type of charger, Clipper Creek HSC-40 as our option of charger. Table 4-15 below gives specification of this type of charger.

Table 4-15 HCS-40 electrical specification[120]

General

Charging Power 32 Amp (7.7kW max)

Product Dimensions 19.7"L x 8.9"W x 5.3"D

Product Weight

Installation Hardwired (3 foot service whip provided)

Supply Circuit 208/240V, 40A

Frequency: 60 Hz

Warranty 3 years

Charge Cable Length 25 feet

Vehicle Connector Type Lockable SAE J1772

Accessories Included SAE J1772 Connector Holster, Wall Mount

Enclosure Fully Sealed NEMA 4

Environment Rating Indoor/Outdoor rated

Operating Temperature -22°F to 122°F (-30°C to +50°C)

Certifications ETL, cETL

According this specification, we can build up an eligible electrical circuit to service the HSC-40 charger.

4.7.4 General Swedish power output analyzes.

In Sweden, the general power socket conforms CEE 7/3 standard8, the general plug conforms CEE 7/49 standard. They together have been called "Schuko" and Type F. This Schuko connection system is symmetrical and unpolarised which means that it does not matter whether you put the plug into the socket reversely. The CEE 7/3 standard socket is also compatible with the CEE 7/16 standard plug and CEE 7/17 plug which are belong to type C. Table 4-16 and Table 4-17 below present the standard power output and plug specification in Sweden. Table 4-18 Standard power output in Sweden[121]. Voltage Frequency Accepting Plug Type 230V 50Hz C,F

8 CEE 7/3 standard was released by The International Commission on the Rules for the Approval of Electrical Equipment (IECEE). 9 CEE 7/4 standard was released by The International Commission on the Rules for the Approval of Electrical Equipment (IECEE). 75

Table 4-19 Swedish General Plug Type Specification[122]. IEC Standar Rating Earth Polaris Fuse Insulat Socket Wor d ed ed d ed accepts ld pins Europl Plug ug s Typ e CEE 2.5 250 NO NO NO YES N/A 7/16 A V C (Europl ug) CEE 16 250 NO NO NO NO N/A - 7/17 A V plug CEE 7/3 Socket 16 250 F YES NO NO NO YES CEE 7/4 A V Socket

Base on the specification in the tables above, we will use Type F (CEE 7/4) socket as one of our charging socket. And it will provides 230V power output, maximally allows 16A current flow.

4.7.5 Charging time and consuming power

4.7.5.1 Charging time and consuming power using SAE J1772 level 2 charging Regarding the SAE J1772 charging, we also study the charging time of the electrical vehicle listed in Fel! Hittar inte referenskälla.,

Table 4-20 below gives data of these.

Table10 4-20 Charging time and consuming power using SAE J1772 level 2 charging[90]–[116] Capacity( Power Curren Charging time Model kW h) (kW) t(A) (hour) Renault Fluence 22 3.5 14.6 7.5 Z.E. Tesla Model S 90 6.6 27.5 14 P90D Toyota Prius 8.8 3.3 13.8 2.25 Plug-in Hybrid BMW i3 22 7.4 30.8 3.5 Chevrolet Spark 21.3 3.3 13.8 7 EV Mitsubishi i-MiEV 16 3.3 13.8 6 Nissan Leaf 24 3.6 15.0 8 Kia Soul EV 27 6.6 27.5 4 Fiat 500e 24 6.6 27.5 4 Mercedes B-Class 28 10 41.7 3.5 Electric Ford Focus Electric 23 6.6 27.5 4 Volkswagen E-Golf 24.2 3.6 15.0 8 5.4 6.0

According this table, we can obtain the average charging power with using SAE J1772 charging is 5.4kW; the consuming power is 6.5 hours in average. However, as our option of charger maximum power is 7.7kW, the Mercedes B-Class Electric cannot charge at its maximum charge rate 10kW. Instead its maximum charge power becomes 7.7kW. Since of these and it is hard to measure the increasing time when Mercedes B-Class charge at this power

10 The data in this table is not accurate. The practical data varies caused by many factors such as the condition of the battery. All this data is gathered from the internet. 78

rate, we recalculate the average consuming power and average charging time by removing the data about this vehicle. We obtain the results that the consuming power of charging is about 4.9 kW and the average fully charging time for each vehicle is about 6.2 hours.

4.7.5.2 Charging time and consuming power using general socket Regarding using the general power socket to charge the electrical vehicle, we have studied the charging time in several types of vehicle listed in Table 4-13. Table 4-21 below gives the data of these. Table11 4-21 Electrical vehicle charging time and consuming power using general power socket[90]–[116] Capacity( Power Curren Charging time Model kW h) (kW) t(A) (hour) Renault Fluence 22 2.3 10 11 Z.E. Tesla Model S 90 2.9 13 30 P90D Toyota Prius 8.8 Plug-in Hybrid BMW i3 22 2.7 12 9.5 Chevrolet Spark 21.3 EV Mitsubishi i-MiEV 16 Nissan Leaf 24 2.3 10 12 Kia Soul EV 27 Fiat 500e 24

11 The blank cell means the data is missing. The data in this table is not accurate. The practical data varies caused by many factors such as the condition of the battery. All this data is gathered from the internet. 79

Mercedes B-Class 28 Electric Ford Focus Electric 23 Volkswagen E-Golf 24.2 2.3 10 13

According this table, we can obtain the average charging time with general socket is 15.1 hours; the consuming power is 2.5kW in average.

4.7.5.3 Chargers arrangement

According the result of daily electric output quantity Pm•Tm=350×840× 2.8 = 823.2kWh and the 4.9kW average consuming power of charging, we can acquire that 823.2kWh/4.9kW=168 hours total charging time. In order to approach the maximum quantity requirement of users, we suppose that each charger can work at least 6.2 hours. In this case we can deploy 168/6.2≈27 chargers at our system. In other word, if 27 vehicles need to be charged in the same time, our system still assures that the 27 vehicle can be acquired fully charging service. Otherwise if there are less than 27 hour vehicle charging at the same time, each charger service hours will relatively increase. And this reckon is theoretical, it neglects the loss between the PV modules 823.2푘푊 and the charger and other influencing factor. ≈ 27 4.9푘푊×6.2ℎ표푢푟푠

4.8 Installation cost

4.8.1 Installation cost of our system

Base on the number and the price of each component we use, we can approximately estimate the total cost of our system. Table 4-22 Lists most of the components we use at our system and the cost of them.

Table 4-23 Cost of system

Capacity 135KW

Daily Power Solar radiation 2.8hours 823.2KWH Consumption

System Voltage 240V

Type 1STH-350-WH $1.05/panel $882.00

Pmax 350W 840 panels Solar panel Vmp 42.98V

Imp 8.13A

SPEC 350w $6,000.00 $12,000.00

Wave form Sinc wave 2 inverters

Inverter Output voltage 60v

Output frequency 50Hz~60Hz

Inverter efficiency 98.80%

Rated voltage 240V $2,500.00 $25,000.00 Controller Rated current 100A 10 controllers

Control mode PWM

Smart charging and discharging; Protection three stages charging function to protect battery.

Battery Type AGM(BAT412350080) $118/battery $94,400.00

Storage battery Voltage 12v 800 batteries

Capacity 38(A/20h)

Type SAE J1772 $565.00 $15,255.00

Vehicle charger Supply Circuit 240V, 40A 27 chargers

Charging power 32 Amp (7.7kW max)

General socket Type F CEE 7/4 socket $3.00 $81.00

Distribution Box Specification 2 inputs; 2 outputs 20

Cable Specification 1.0mm2

Solar Mounting Inclined Roof Mounting Type System

Total $147,618.00

5 Chapter: Conclusion and future work

Striving for a greener and eco-friendly future depends on how much actions we put in so as to reduce and while not stop those humane behaviours based on car usage that increases the level on environmental pollution. Efficient harnessing of solar energy involved choosing efficient components that provide the required energy capacity to charge the electric cars. With a surface area of 2900m2, 840 1STH-350-WH PV modules at 71 degrees inclination, it generated approximately at least 136kwh daily energy output in winter, average 823.2kwh daily energy output throughout a year in theory. Combining 10 SDC240-100A micro controllers, 2 SDP30Kw inverters, 800 AGM (BAT412350080) storage batteries from our system model, we can charge up to 27 electrical vehicles at once with an average full charging time of up to 6.2 hours. All these are achieved due to the fact that we use the SAE J1772 standard charging. Additionally general power sockets provide 230V power output in case more energy is needed. This energy is obtained from the general AC power grid and the average charging time 15.1 hours with this alternative charging method. Also, this method of charging consumes 2.5kW power in average. Since the solar energy generation and charging occurs during the day, thus using photovoltaic to charge electric cars means most of the electric vehicle charging will have to take place during working hours, which will have significant impact on reducing carbon emissions during the day which is the main humane concern. With this piece of work we do hope it serves as a starting point for other research work in this area.

Reference

[1] “Solar energy,” Wikipedia, the free encyclopedia. 03-May-2016. [2] “Summary of Population Statistics 1960-2015,” Statistiska Centralbyrån. [Online]. Available: http://www.scb.se/en_/Finding- statistics/Statistics-by-subject-area/Population/Population- composition/Population-statistics/Aktuell-Pong/25795/Yearly- statistics--The-whole-country/26040/. [Accessed: 14-May-2016]. [3] “Vehicle statistics.” [Online]. Available: http://www.trafa.se/en/road- traffic/vehicle-statistics/. [Accessed: 14-May-2016]. [4] “Climate: Karlskrona - Climate graph, Temperature graph, Climate table - Climate-Data.org.” [Online]. Available: http://en.climate- data.org/location/6274/. [Accessed: 14-May-2016]. [5] V. Masson, M. Bonhomme, J.-L. Salagnac, X. Briottet, and A. Lemonsu, “Solar panels reduce both global warming and urban heat island,” Atmospheric Sci., vol. 2, p. 14, 2014. [6] “A Vision for a Climate-Friendly Future | Center for Climate and Energy Solutions.” [Online]. Available: http://www.c2es.org/newsroom/speeches/vision-climate-friendly- future. [Accessed: 14-May-2016]. [7] “IEA - Key World Energy Statistics 2013,” Statista. [Online]. Available: http://www.statista.com/study/17714/global-energy- statistics/. [Accessed: 16-May-2016]. [8] V. Masson, M. Bonhomme, J.-L. Salagnac, X. Briottet, and A. Lemonsu, “Solar panels reduce both global warming and urban heat island,” Atmospheric Sci., vol. 2, p. 14, 2014. [9] “Solar Energy Creates Green Jobs Nationwide for a Strong Economy.” [Online]. Available: http://www.brightsourceenergy.com/jobs-creation- economy#.VzbHt_l97IV. [Accessed: 14-May-2016]. [10] Q. Liu, “Electric car with solar and wind energy may change the environment and economy: A tool for utilizing the renewable energy resource,” Earths Future, vol. 2, no. 1, pp. 7–13, Jan. 2014. [11] M. Z. Jacobson and M. A. Delucchi, “Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials,” Energy Policy, vol. 39, no. 3, pp. 1154–1169, Mar. 2011.

[12] P. Kelly-Detwiler, “Electric Cars and the Power Grid: How Are They Coming Together?,” Forbes. [Online]. Available: http://www.forbes.com/sites/peterdetwiler/2013/01/28/electric-cars- and-the-power-grid-how-are-they-coming-together/. [Accessed: 14- May-2016]. [13] P. S. G. A. Putrus, “Impact of electric vehicles on power distribution networks,” 5th IEEE Veh. Power Propuls. Conf. VPPC 3909, pp. 827– 831, 2009. [14] “Design of Microcontroller Based Static VAR Compensator.” [Online]. Available: http://www.ijser.org/paper/Design-of- Microcontroller-Based-Static-VAR-Compensator.html. [Accessed: 14-May-2016]. [15] W. Zhang, W. Ge, M. Huang, J. Jiang, W. Zhang, W. Ge, M. Huang, and J. Jiang, “Optimal Day-Time Charging Strategies for Electric Vehicles considering Photovoltaic Power System and Distribution Grid Constraints, Optimal Day-Time Charging Strategies for Electric Vehicles considering Photovoltaic Power System and Distribution Grid Constraints,” Math. Probl. Eng. Math. Probl. Eng., vol. 2015, 2015, p. e765362, Mar. 2015. [16] Z. Salam, M. J. B. A. Aziz, and K. P. Yee, “A critical review of electric vehicle charging using solar photovoltaic,” Int. J. Energy Res., vol. 40, no. 4, pp. 439–461, Mar. 2016. [17] S. C. B. Kramer, “A Review of Plug-in Vehicles and Vehicle-to-Grid Capability,” Proc. - 34th Annu. Conf. IEEE Ind. Electron. Soc. IECON 2008, pp. 2278–2283, 2008. [18] “An Overview of the SWEBOK Guide - SEBoK.” [Online]. Available: http://sebokwiki.org/wiki/An_Overview_of_the_SWEBOK_Guide#So ftware_Design. [Accessed: 14-May-2016]. [19] “Part 2: Solar Energy Reaching The Earth’s Surface | ITACA.” . [20] “7(f) Atmospheric Effects on Incoming Solar Radiation.” [Online]. Available: http://www.physicalgeography.net/fundamentals/7f.html. [Accessed: 14-May-2016]. [21] “Solar energy,” Wikipedia, the free encyclopedia. 03-May-2016. [22] Smil, Vaclav and V. Smil, Energy at the Crossroads: Global Perspectives and Uncertainties. [[MIT Press]], 2003. [23] Smil, Vaclav and V. Smil, Energy at the Crossroads. Organisation for Economic Co-operation and Development, 2006.

[24] “Solar Basics | Intro to Solar Panels and Solar Energy | Yingli Solar.” [Online]. Available: http://www.yinglisolar.com/en/solar-basics/. [Accessed: 16-May-2016]. [25] “Power Characteristics of a Solar Panel.” [Online]. Available: http://www.wholesalesolar.com/solar-information/solar-panel- efficiency. [Accessed: 14-May-2016]. [26] “The Effect of Temperature on Photovoltaic Cell Efficiency.” [Online]. Available: http://www.civilica.com/EnPaper-- ETEC01_021.html. [Accessed: 14-May-2016]. [27] M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D. Dunlop, “Solar cell efficiency tables (version 43),” Prog. Photovolt. Res. Appl., vol. 22, no. 1, pp. 1–9, Jan. 2014. [28] N. I. Mrs Jaya, “PIC BASED SOLAR CHARGING CONTROLLER FOR BATTERY.” [29] M. D. Hussein Ibrahim, “Wind-Diesel hybrid system: energy storage system selection method,” 2012. [30] N. M. L. Tan, T. Abe, and H. Akagi, “Design and Performance of a Bidirectional Isolated DC #x2013;DC Converter for a Battery Energy Storage System,” IEEE Trans. Power Electron., vol. 27, no. 3, pp. 1237–1248, Mar. 2012. [31] C. B. Manufacturing, “GHS Safety Data Sheets | Crown Battery.” [Online]. Available: http://www.crownbattery.com/material-safety- data-sheets. [Accessed: 16-May-2016]. [32] “Batteries in a Portable World | A Handbook on Rechargeable Batteries for Non-engineers.” [Online]. Available: http://www.buchmann.ca/buchmann/. [Accessed: 16-May-2016]. [33] “INVESTIGATION DES DIVERSES OPTIONS DE STOCKAGE D ÉNERGIE FACE À L INTÉGRATION DES PARCS ÉOLIENS DANS LES RÉSEAUX.” [Online]. Available: http://docplayer.fr/5129219-Investigation-des-diverses-options-de- stockage-d-energie-face-a-l-integration-des-parcs-eoliens-dans-les- reseaux.html. [Accessed: 16-May-2016]. [34] “Stockage d’énergie et énergies renouvelables | Saft.” [Online]. Available: http://www.saftbatteries.com/fr/solutions-du- marche/stockage-denergie-et-energies-renouvelables. [Accessed: 16- May-2016]. [35] “Photovoltaic Systems Engineering, Third Edition,” CRC Press, 26- Feb-2010. [Online]. Available:

https://www.crcpress.com/Photovoltaic-Systems-Engineering-Third- Edition/Messenger-Abtahi/p/book/9781439802922. [Accessed: 16- May-2016]. [36] S. Kalaiselvam and R. Parameshwaran, “Chapter 2 - Energy Storage,” in Thermal Energy Storage Technologies for Sustainability, Boston: Academic Press, 2014, pp. 21–56. [37] “2012_innostock-ibrahim_inno-s-14.pdf.” . [38] “Wikipedia:Cleanup Taskforce/String inverter.,” Wikipedia, the free encyclopedia. . [39] “Solar micro-inverter,” Wikipedia, the free encyclopedia. 01-May- 2016. [40] “Power optimizer,” Wikipedia, the free encyclopedia. 05-May-2016. [41] “Car Pollution Facts.” [Online]. Available: http://evsroll.com/Car_pollution_facts.html. [Accessed: 16-May- 2016]. [42] M. A. Lange, S. J. Cohen, and P. Kuhry, “Integrated global change impact studies in the Arctic: the role of the stakeholders,” Polar Res., vol. 18, no. 2, pp. 389–396, Dec. 1999. [43] “This Month in Physics History.” [Online]. Available: http://www.aps.org/publications/apsnews/200904/physicshistory.cfm. [Accessed: 16-May-2016]. [44] “Which Solar Panel Type is Best? Mono-, Polycrystalline or Thin Film?,” Energy Informative. . [45] “Monocrystalline silicon,” Wikipedia, the free encyclopedia. 25-Apr- 2016. [46] “Which Solar Panel Type is Best? Mono-, Polycrystalline or Thin Film?,” Energy Informative. . [47] “Thin-film solar cell,” Wikipedia, the free encyclopedia. 14-May- 2016. [48] mzentgraad, “Fraunhofer ISE publishes ‘Photovoltaics Report’ — Fraunhofer ISE.” [Online]. Available: https://www.ise.fraunhofer.de/en/news/news-archive/news- 2012/fraunhofer-ise-publishes-photovoltaics-report. [Accessed: 16- May-2016]. [49] “On the trail of toxic substances - Solar Energy - Renewables International.” [Online]. Available: http://www.renewablesinternational.net/on-the-trail-of-toxic- substances/150/452/83682/. [Accessed: 16-May-2016].

[50] “Cost Performance of Thin Film and Crystalline Photovoltaic Cells – A Comparative Study - Inpressco.” . [51] “Ultrathin, Dye-sensitized Solar Cells Called Most Efficient To Date,” ScienceDaily. [Online]. Available: https://www.sciencedaily.com/releases/2006/09/060918201621.htm. [Accessed: 16-May-2016]. [52] “Multi-junction solar cell,” Wikipedia, the free encyclopedia. 30-Apr- 2016. [53] “Emerging Photovoltaic Technology - Energy Harvesting | DigiKey.” [Online]. Available: http://www.digikey.com/us/en/techzone/energy- harvesting/resources/articles/emerging-photovoltaic-technology.html. [Accessed: 16-May-2016]. [54] M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D. Dunlop, “Solar cell efficiency tables (version 44),” Prog. Photovolt. Res. Appl., vol. 22, no. 7, pp. 701–710, Jul. 2014. [55] “1SolTech 1STH-350-WH (350W) Solar Panel.” [Online]. Available: http://www.solardesigntool.com/components/module-panel- solar/1SolTech/2493/1STH-350-WH/specification-data-sheet.html. [Accessed: 04-May-2016]. [56] “17.8% Efficiency 250w Solar Panel For Pv System - Buy 250w Solar Panel,Panel Solar,Solar Cell Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product- detail/17-8-efficiency-250w-solar-panel_60411307367.html. [Accessed: 11-May-2016]. [57] “Evergreen ES-A-210 Black Frame Solar Panel Wholesale Discount.” [Online]. Available: http://www.solarelectricsupply.com/evergreen- 210-watt-solar-panel-es-a-series-for-home-grid-tie-solar-systems-553. [Accessed: 11-May-2016]. [58] “High Efficiency Amorphous Silicon Thin Film Solar Cells/solar Panels For Sale - Buy 15kw Solar Panel (get Sun Powe Take All Home Load),Monocrystalline Photovoltaic Cell Solar Panels 250 Watt For Solar Lighting System,Hanergy Apartment/villas Grid-connected Home Solar Systems 3 Kw Flagship Series Solar Panels Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/high-efficiency-amorphous-silicon- thin-film_60185516726.html. [Accessed: 17-May-2016]. [59] “High Efficiency Amorphous Silicon Thin Film Solar Cells/solar Panels For Sale - Buy 15kw Solar Panel (get Sun Powe Take All

Home Load),Monocrystalline Photovoltaic Cell Solar Panels 250 Watt For Solar Lighting System,Hanergy Apartment/villas Grid-connected Home Solar Systems 3 Kw Flagship Series Solar Panels Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/high-efficiency-amorphous-silicon- thin-film_60185516726.html. [Accessed: 17-May-2016]. [60] “DM 77W CdTe Solar Module, 12v CdTe Solar Panels.” [Online]. Available: http://www.dmsolar.com/solar-module- 111.html?fb_xd_fragment. [Accessed: 17-May-2016]. [61] “Dye Solar Cell(tuv,Iec,Rohs,Ce,Mcs) - Buy Dye Solar Cell,Dye Sensitized Solar Cell,Pv Solar Cell Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product- detail/dye-solar-cell-TUV-IEC-ROHS_1401807338.html. [Accessed: 17-May-2016]. [62] “Oem/odm Dye Solar Cell - Buy Dye Solar Cell,Durable Use Diy Solar Energy,Easy Carrying Folding Solar Panel 300w Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/OEM-ODM-dye-solar- cell_60380337072.html. [Accessed: 19-May-2016]. [63] “NASA Surface meteorology and Solar Energy - Available Tables.” [Online]. Available: https://eosweb.larc.nasa.gov/cgi- bin/sse/grid.cgi?&num=196147&lat=56.16&submit=Submit&hgt=100 [email protected]&p=grid_id&p= swv_dwn&p=T10M&step=2&lon=15.58. [Accessed: 29-Apr-2016]. [64] “solar charge controller SC4060 30A/ 40A/ 50A/ 60A /80A 48V, product picture - Makepolo.” [Online]. Available: http://solargloble.en.makepolo.com/products/solar-charge-controller- SC4060--30A-p62535786/img.html. [Accessed: 21-May-2016]. [65] “ENF Ltd.” [Online]. Available: /pv/panel-datasheet/Thin-film/835. [Accessed: 11-May-2016]. [66] “Solar Panel Charge Controller 15Amp 20Amp 12V/24V KT1215 KT1220, View Solar Panel Charge Controller, Coretek Product Details from Guangzhou Coretek Electronic Co., Ltd. on Alibaba.com.” [Online]. Available: https://mppt.en.alibaba.com/product/60143127554- 800872270/Solar_Panel_Charge_Controller_15Amp_20Amp_12V_24 V_KT1215_KT1220.html. [Accessed: 21-May-2016].

[67] “12v/24v Hanfong Sr50 Solar Regulator Pwm Solar Charge Controller - Buy China Solar Charge Controller,Solar Charge Controller Mppt,Price Solar Charge Controller Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product- detail/12v-24v-Hanfong-SR50-Solar-regulator_60325078560.html. [Accessed: 21-May-2016]. [68] “WELLSEE WS-C2430 25A 12/24V solar battery charge controller_charge regulator_Products_Physical therapy,health product,therapeutic apparatus,Electro Acupuncture,Medical Supplies are best selling on our website!” [Online]. Available: http://www.e- bluelight.com/goods-45-WELLSEE+WS- C2430+25A+1224V+solar+battery+charge+controller.html. [Accessed: 21-May-2016]. [69] “SDC240V-100A--Yueqing Sandi Electric Co.,Ltd.” [Online]. Available: http://www.lgis.cc/?en%2Fen_products%2FProduct119%2F506.html. [Accessed: 22-May-2016]. [70] “Aliexpress.com: Comprar Ecnomical I P eSMART 12V / 24 V / 48V 40A MPPT solar charge controller 48 V 40A PV regulador 40A regulador del cargador de batería de controler cargador fiable proveedores en Shenzhen I-Panda New Energy Technology & Science Co., Ltd.,” aliexpress.com. [Online]. Available: //es.aliexpress.com/store/product/Ecnomical-I-P-eSMART-12V-24V- 48V-40A-MPPT-solar-charge-controller-48V-40A-PV- regulator/610114_2031529273.html?src=ibdm_d03p0558e02r02. [Accessed: 21-May-2016]. [71] “Aliexpress.com: Comprar Itracer IT6415ND 60A MPPT regulador de carga Solar RS232 RS485 con protocolo Modbus CAN Bus 12 V 24 V 36 V 48 V trabajo auto de controlar la hipertensión fiable proveedores en Ningbo Cinco Electronics Technology Co., Ltd,” aliexpress.com. [Online]. Available: //es.aliexpress.com/store/product/iTracer-IT6415ND-60A-MPPT- Solar-Charge-Controller-RS232-RS485-with-Modbus-protocol-CAN- Bus-12V- 24V/911465_32479738914.html?src=ibdm_d03p0558e02r02. [Accessed: 21-May-2016]. [72] “Tracer-4210A MPPT Solar Charge Controller 40A--Inverter & Charger Controller -Shanghai Tingen Electric Co.,ltd.” [Online].

Available: http://www.shtepower.com/index.php?_m=mod_product&_a=view&p _id=333. [Accessed: 21-May-2016]. [73] “SDC240V-100A--Yueqing Sandi Electric Co.,Ltd.” [Online]. Available: http://www.lgis.cc/?en/en_products/Product119/506.html. [Accessed: 19-May-2016]. [74] M. D. Hussein Ibrahim, “Wind-Diesel hybrid system: energy storage system selection method,” 2012. [75] “Lithium battery 12.8V 60Ah 0.75kwh CB BAT512600500.” [Online]. Available: http://www.cclcomponents.com/product.asp?ID=3745. [Accessed: 17- May-2016]. [76] “Lead acid batteries for home solar energy storage - Solar Choice.” [Online]. Available: http://www.solarchoice.net.au/blog/lead-acid- batteries-for-home-solar-energy-storage. [Accessed: 25-Apr-2016]. [77] “AGM(BAT412201080) - Google Search.” [Online]. Available: https://www.google.se/search?q=AGM(BAT412201080)&biw=625& bih=573&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiN4tamzOP MAhUhD5oKHRy6AEMQ_AUIBigB#imgrc=ocDfK4Papz9bDM%3 A. [Accessed: 18-May-2016]. [78] “Advantages & Limitations of the Lithium-ion Battery - Battery University.” [Online]. Available: http://www.batteryuniversity.com/learn/article/is_lithium_ion_the_ide al_battery. [Accessed: 18-May-2016]. [79] K. Zipp, “What is the best type of battery for solar storage?,” Solar Power World. [Online]. Available: http://www.solarpowerworldonline.com/2015/08/what-is-the-best- type-of-battery-for-solar-storage/. [Accessed: 18-May-2016]. [80] “T105-RE, Trojan 6V 225 AH Premium Line Flooded Battery,” The Solar Supermarket. [Online]. Available: http://www.thesolarsupermarket.com/proddetail.php?prod=T105-RE. [Accessed: 17-May-2016]. [81] “Lithium battery 12.8V 60Ah 0.75kwh CB BAT512600500.” [Online]. Available: http://www.cclcomponents.com/product.asp?ID=3745. [Accessed: 17- May-2016].

[82] M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D. Dunlop, “Solar cell efficiency tables (version 46),” Prog. Photovolt. Res. Appl., vol. 23, no. 7, pp. 805–812, Jul. 2015. [83] “CellCube flow battery system from GILDEMEISTER energy solutions.” [Online]. Available: http://energy.gildemeister.com/en/store/cellcube-fb-10-20- 30#Overview. [Accessed: 10-May-2016]. [84] “UPS Premium DSP0.9 Hybrid 10-500kVA (3/3) & 10-30kVA (3/1),” visionups. [Online]. Available: https://visionups.com/en/solar- product/11-ups-premium-dsp09-hybrid-10-500kva-33-10-30kva- 31.html. [Accessed: 17-May-2016]. [85] “String Inverters vs. Microinverters vs. Power Optimizers | EnergySage.” [Online]. Available: https://www.energysage.com/solar/101/string-inverters- microinverters-power-optimizers. [Accessed: 19-Apr-2016]. [86] “350w 600w 1000w 1500w Solar Hybrid Controller Inverter For Solar System - Buy Solar Micro Inverter 600w,Inverter Price 1000w,Hybrid Solar Inverter 350w Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/350w-600w- 1000w-1500w-solar-hybrid_60098608945.html. [Accessed: 17-May- 2016]. [87] “350w 600w 1000w 1500w Solar Hybrid Controller Inverter For Solar System - Buy Solar Micro Inverter 600w,Inverter Price 1000w,Hybrid Solar Inverter 350w Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/350w-600w- 1000w-1500w-solar-hybrid_60098608945.html. [Accessed: 17-May- 2016]. [88] “Power Inverter Pure Sine Wave Three Phase Solar Inverter With Battery Charger - Buy Solar Three Phase Inverter,Power Pure Sine Wave Inverter,Inverter With Battery Charger Product on Alibaba.com,” www.alibaba.com. [Online]. Available: //www.alibaba.com/product-detail/Power-inverter-pure-sine-wave- three_60267642266.html. [Accessed: 19-May-2016]. [89] “Power Inverter Pure Sine Wave Three Phase Solar Inverter With Battery Charger - Buy Solar Three Phase Inverter,Power Pure Sine Wave Inverter,Inverter With Battery Charger Product on Alibaba.com,” www.alibaba.com. [Online]. Available:

//www.alibaba.com/product-detail/Power-inverter-pure-sine-wave- three_60267642266.html. [Accessed: 19-May-2016]. [90] “BMW i3,” Wikipedia, the free encyclopedia. 12-Apr-2016. [91] “BMW i3 : Range & charging.” [Online]. Available: http://www.bmw.com/com/en/newvehicles/i/i3/2015/showroom/range _charging.html. [Accessed: 26-Apr-2016]. [92] “2016 Spark EV: Electric Vehicle | Chevrolet.” [Online]. Available: http://www.chevrolet.com/spark-ev-electric-vehicle.html. [Accessed: 19-Apr-2016]. [93] “Chevrolet Spark,” Wikipedia, the free encyclopedia. 19-Apr-2016. [94] “Chevrolet Spark EV,” PluginCars.com, 24-Jan-2014. [Online]. Available: http://www.plugincars.com/chevrolet-spark-ev. [Accessed: 26-Apr-2016]. [95] J. 2013 and B. K. A. WILSON, “Chevrolet Spark EV - Car and Driver.” [Online]. Available: http://www.caranddriver.com/chevrolet/spark-ev. [Accessed: 26-Apr- 2016]. [96] “Nissan Leaf,” Wikipedia, the free encyclopedia. 15-Apr-2016. [97] “Toyota Prius Plug-in Hybrid,” Wikipedia, the free encyclopedia. 20- Apr-2016. [98] “2016 FIAT 500e - All Electric Car with Zero Emissions.” [Online]. Available: http://www.fiatusa.com/en/500e/. [Accessed: 26-Apr- 2016]. [99] “Fiat 500 (2007),” Wikipedia, the free encyclopedia. 24-Apr-2016. [100] “Fiat 500e,” PluginCars.com, 23-Jan-2014. [Online]. Available: http://www.plugincars.com/fiat-500e. [Accessed: 26-Apr-2016]. [101] “2016 Focus Electric | View Focus Electric Highlights | Ford.com.” [Online]. Available: http://www.ford.com/cars/focus/trim/electric/. [Accessed: 25-Apr-2016]. [102] “Ford Focus Electric,” Wikipedia, the free encyclopedia. 24-Apr- 2016. [103] KIA, “Electric Car 3 Charge Levels | Kia Soul EV | Kia Cars.” [Online]. Available: http://www.kia.com/us/en/content/ev- faqs_2016/charging/three-charge-levels. [Accessed: 26-Apr-2016]. [104] “Kia Soul EV,” Wikipedia, the free encyclopedia. 05-Mar-2016. [105] “B-Class Electric Drive | Mercedes-Benz,” Mercedes-Benz USA. [Online]. Available:

http://www.mbusa.com/mercedes/vehicles/class/class-B/bodystyle- EDV. [Accessed: 25-Apr-2016]. [106] “Mercedes B-Class Electric Drive,” PluginCars.com, 15-Feb-2014. [Online]. Available: http://www.plugincars.com/mercedes-b-class-e- cell. [Accessed: 25-Apr-2016]. [107] “2016 Mitsubishi i-MiEV Trims.” [Online]. Available: http://www.mitsubishicars.com/imiev/trims. [Accessed: 26-Apr- 2016]. [108] “Mitsubishi i-MiEV,” Wikipedia, the free encyclopedia. 31-Mar- 2016. [109] “Renault Fluence Z.E.,” Wikipedia, the free encyclopedia. 04-Mar- 2016. [110] “Renault Fluence Z.E. - Charging Systems,” e-Station Store. [Online]. Available: http://www.e-station-store.com/en/28-renault- fluence-ze. [Accessed: 26-Apr-2016]. [111] “How to Charge your Tesla Model S at Home,” Drive & Dream, 02- Mar-2014. . [112] “Model S | Tesla Motors.” [Online]. Available: https://www.teslamotors.com/models. [Accessed: 18-Apr-2016]. [113] “Tesla Model S,” Wikipedia, the free encyclopedia. 18-Apr-2016. [114] “Using public EV charging stations with your Tesla Model S,” TESLARATI.com, 06-May-2014. . [115] “e-Golf Brochures & price list : Volkswagen UK.” [Online]. Available: http://www.volkswagen.co.uk/new/e-golf-vii/which- model/brochures. [Accessed: 25-Apr-2016]. [116] “e-golf-vii pricing & specifications : Volkswagen UK.” [Online]. Available: http://www.volkswagen.co.uk/new/e-golf-vii/which-model- compare/details/1770#!#overview. [Accessed: 25-Apr-2016]. [117] “A Simple Guide to DC Fast Charging,” FleetCarma, 04-Feb-2016. . [118] “Nominal power (photovoltaic),” Wikipedia, the free encyclopedia. 06-Aug-2015. [119] “SAE J1772,” Wikipedia, the free encyclopedia. 31-Mar-2016. [120] “32A Level 2 EVSE HCS-40 | ClipperCreek.” [Online]. Available: http://store.clippercreek.com/hcs-40-hcs-40p-ev-charging-station. [Accessed: 19-May-2016]. [121] “IEC - World Plugs: Plug Type F.” [Online]. Available: http://www.iec.ch/worldplugs/typeF.htm. [Accessed: 20-Apr-2016].

[122] “AC power plugs and sockets,” Wikipedia, the free encyclopedia. 13- Apr-2016.