PROJECT TOPIC ON INSTALLATION OF INVERTER IN A LABORATORY

Industrial Chemist, Science Laboratory Technologist, Trader, Education Consultant, Tutor à BasamTrade and Services
20 Oct 2017
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PROJECT TOPIC ON INSTALLATION OF INVERTER IN A LABORATORY

• 1. 1 CHAPTER ONE 1.0 INTRODUCTION INVERTER Within the last decade, there has been major advancement in power electronics. Power has moved along with these developments with such as digital signals processors being used to control power systems. An inverter is basically a converter that converts DC – AC power. Inverter circuit can be very complex so the objective of this project work is to present details on the inner workings of inverter and also to install (Mohan et al., 1989). A voltage Source Inverter (VSI) is one that takes in a fixed voltage from a device, such as a DC power supply, and converts it to a variable frequency AC supply. Voltage Source Inverter is divided into three general categories, Pulse-Width Modulated (PWM) inverters, Square Wave Inverters, single phase inverter with voltage cancellation. Pulse-Width Inverter takes in a constant DC voltage. Diode rectifier is used to rectify the line voltage and the inverter must control the magnitude and the frequency of the output voltages. To do this, the inverter uses pulse-width modulation using its switches. There are different methods for doing the pulse-width modulation in an inverter in order to shape the output AC voltages to be very close to sine wave (MHC, 2000). This different methods will be discussed further with a sinusoidal – PWM. Square wave inverters have their input connected to a controlled DC voltage in other to control the magnitude of the output AC voltage. The inverter only controls the frequency of the output where the input voltage controlled the magnitudes. The inverter only controls the frequency of the output where the input voltage controls the magnitude. The output AC voltage has a waveform similar to a square wave which is
• 2. 2 where the inverter got its name. Lastly, single phase inverters with voltage cancellation, take in a constant DC source and output a square – wave like Ac voltage. They can control both the frequency and the magnitude of the output but do not use PWM and therefore have a square – wave like output. These inverters have combined characteristics of the previous two inverters (Bird et al., 1993). 1.1 BACKGROUND OF THE STUDY In Nigeria, there is inconsistence supply of electricity by the power supplying company to the consumers. Hence the use of additional electric power source such as electric power generators and most recently the use of semiconductor power devices such as the bipolar transistor, Thyristors and particularly MOSFET to generate electric power in conjunction with a DC battery is needed (Omitola et al., 2014). Due to the erratic power supply in the country, which is becoming unbearable each day with its effect on the laboratory business and energy, solar cell powered inverter can be substitute in the laboratory because of the need for constant power supply (Coker and Ogungi, 2013). The inverter makes use of an energy source such as photovoltaic to be domestically and industrially relevant for use, as in sort goes a long way to reduce the levels of greenhouse gases in the atmosphere and alleviate this global warming on process. The photovoltaic power generation is reliable. It involves no moving parts and the operation and maintenance costs are very low (Coker and Ogungi, 2013). 1.2 AIM OF THE STUDY The aim of this work is to install an inverter to function with an array of photovoltaic (PV) cells and battery to supply constant electricity in our laboratory.
• 3. 3 1.3 SPECIFIC OBJECTIVE OF THE STUDY The following are the main objective of this project. 1. To check the problem of the unstable power supply. 2. To purchase an inverter. 3. To dismantle the inverter and have a study on the major electronic components. 4. To check for the working principle of the inverter. 5. To re-couple the inverter and testing it with the batteries. 6. To install the inverter for the electric power supply in the laboratory. 1.4 STATEMENT OF THE PROBLEM The major problem encountered was how to know an original inverter product, as many products are found in the market. The work also sought to determine the extent to which an inverter can be used in the construction of solar power generator. 1.5 SCOPE OF THE STUDY The scope of this project is typically based on the specific objectives which are; checking the problem of the unstable power supply in the laboratory, purchasing an inverter, studying the major electronic component found in the inverter circuits, re- coupling the inverter and testing it with the batteries and finally installing the inverter for the electric power supply to the laboratory. 1.6 LIMITATION OF THE PROJECT An attempt to use it to drive more than recommended load may or will reduce the life span of the inverter thereby causing harm to some major electronic component in it and if the DC is not well charged up to the desired input voltage there may be fluctuation at the output voltage.
• 4. 4 1.7 SIGNIFICANCE OF THE STUDY A DC/AC inverter is one of the most efficient mobile power sources. Like in science laboratories, the inverter will be the ‘’heart’’ of power supply as it will serve as a back-up power source.
• 5. 5 CHAPTER TWO 2.0 LITERATURE REVIEW 2.1 CLASIFICATION OF AN INVERTER The solar inverters are electrical devices meant to perform the operation of converting DC from array or battery to single or three phase AC signals. For photovoltaic solar systems, the inverters are incorporated with some inbuilt devices. This includes; i. Automatic switch off if the array output is too high or too low. ii. Automatic restart. iii. Protecting scheme to take care of short circuit and overloading. Generally, the inverter to be used that would produce the quality output must have the following features; i. Overload protection. ii. Miniature Circuit Breaker trip indicator (MCB). iii. Low-battery protection iv. Constant and trickle charging system. v. Load status indicator. (Adejumobi et al., 2011). An inverter is an electrical device that is widely used to convert the DC supply to AC supply, an inverter are used in applications such as adjustable-speed AC motor drives, Uninterrupted Power Supply (UPS)and most domestic appliances instrument and devices. Most of the energy renewable supply are in form of DC, as a solution, the inverter as a converter that will convert the energy to AC form, beside that the inverter was the solution for electrical energy problems that occur at remote areas, most remote area around the
• 6. 6 earth used the renewable energy to solve the energy problem. A solar energy system was the most alternative energy used at remote area, most of the renewable energy is in form of DC (Direct Current), in order to convert the DC from the battery and solar panels to standard main AC (Alternating Current) and inverter is needed (Zairina, 2010). Figure 2.1 Block diagram of types of inverter (Zairina, 2010). 2.2 TYPES OF INVERTER Inverter is mainly designed base on three methods or types. 1. Voltage Source Inverter (VSI) 2. Current Source Inverter (CSI) 3. Resonant Inverter (High Frequency Sine-Wave Inverter) Inverter can be classified Single Phase Three Phase Three types of inverter 1. Voltage SourceInverter (VSI). 2. Current SourceInverter (CSI). 3. Resonant Inverter.
• 7. 7 2.2.1 VOLTAGE SOURCE INVERTER (VSI) This type of inverter is fed by a DC source of small internal impedance. Looking from an AC side, the terminal voltage remains almost constant irrespective of the load current drawn. Depending on the circuit configuration, the voltage source may be classified as half bridge and full bridge inverter. VSI may further be classified as; 1. Pulse-Width Modulated (PWM) inverters 2. Square-Wave Inverter Pulse-Width Modulated (PWM) Inverter:- In PWM inverter, the output has one or more pulses in each half cycles varying the width of these pulses. The output voltage may be controlled. The magnitude of input DC voltage is essentially constant in this type of inverter (Zairina, 2010). In electronic power converters and motors, PWM is used extensively as a means of powering Alternating Current (AC) devices with an available Direct Current source or for advanced DC/AC conversion. The pattern through which the duty cycle of a PWM signals varies and can be created through simple analogue components, a digital microcontroller, or specific PWM integrated circuits (Rosdan, 2009). 2.2.1.1 ADVANTAGES OF PWM Using pulse width modulation has several advantagesover analog control. I. The entire control circuit can be digital, eliminating the need for digital-to-analog converters. II. Using digital control lines will reduce the susceptibility of your circuit to interference.
• 8. 8 III. Finally, motors may be able to operate at lower speeds if you control them with PWM. When you use an analog current to control a motor, it will not produce significant torque at low speeds. IV. The output voltage control can be obtained without any additional components. V. With this method, lower order harmonics can be eliminated or minimized Along with its output voltage control. VI. As higher order harmonics can be filtered easily the higher order harmonics can be minimized (Bhabani et al., 2009). Square-Wave inverter produces a square wave AC voltage of constant magnitude. The output voltage of this type of inverter can only be varied by controlling the input DC voltage. There are three circuit topologies of VSI I. Full bridge inverter. II. Half bridge inverter. III. Push pulls inverter. (Zarina, 2010) 2.2.2 CURRENT SOURCE INVERTER (CSI) Current Source Inverter, this type of inverter is fed by current from DC source with high internal impedance (using current limiting chokes or inductors in series with a DC source). Therefore, supply current does not change quickly. The load current is varied by controlling the input DC voltage of the current source inverter. CSI is used in very high power AC drives. The input to the inverter is a current source, which is usually obtained by a large inductor in series with the voltage source at the input. The peak current source
• 9. 9 rating of the switches is equal to the DC current source and is lower compared to the VSI. The disadvantages of CSI discovered are; I. Slower dynamic response II. Filters are required at the output to suppress the voltage spike. III. Less popular compared to VSI. (Zairina, 2010) 2.2.3 RESONANT INVERTER Resonant Inverter suitable for high frequency operation has numerous applications, including as radio frequency power amplifier, induction heating and plasma generation. The new design also realizes small passive components, fast dynamic response, and a high degree of design flexibility. This characteristic makes the resonant inverter advantageous in applications requiring very high frequency operation at fixed frequency and duty ratio (Rivas et al., 2007). 2.3 VOLTAGE SOURCE INVERTER TYPE Voltage Source Inverter is classified into two types; there are single phase inverter and three phase inverter. The two types of inverter can be divided into several types depending on the output wave form of the inverter. Based on that fact there are three types of inverter, first type of inverter was a square wave inverter, this type of inverter produce is inefficient and is hard on many types of equipment. Second type of inverter was a modified sine wave inverter; this is probably the most popular and economical type of power inverter. It produces an AC waveform somewhere between a square wave and a pure sine wave. Modified sine wave inverters, sometimes called quasi-sine wave inverters are not real expensive and work well in all but most demanding application and even most computers work well with a modified sine wave inverter. However, there are exceptions,
• 10. 10 some appliances that use timers may not work quite right with a modified sine wave inverter. And since more and more consumer products are using speed controls and timers, this type of inverter will not be suitable for use. The third type of inverter was the true sine wave inverter. A true sine wave power inverter produces the closest to a pure sine wave of all power inverters and in many cases produces cleaner power than the utility company itself (Zairina, 2010). It will run practically on any type of AC equipment and is also the most expensive. Many true sine wave power inverters are computer controlled and will automatically turn on and off. Figure 2.3.1 Block diagram of Voltage Inverter type (Zairina, 2010) Voltage SourceInverter type Square-Wave Inverter Modified Sine Wave Inverter Pure-Sine Wave Inverter
• 11. 11 Figure 2.3.2 Graph of voltage against time (www.intechopen.com, 2015) 2.4 PRESENT LEVEL OF RESEARCH AND DEVELOPMENT In Nigeria not much research and development have been carried out on photovoltaic or solar thermal energy and associated devices. These devices are yet to become common household commodities in Nigeria. Their uses are only scantly seen in Universities and research centers. Hence availability in Nigeria market of made in Nigeria brand name solar energy PV generating equipment and accessory is still a dream. This shows that Nigeria has a lot of journey to go in the area of solar energy research, development and device production (Akinboro et al.,2010). 2.5 THE BASIC OF SOLAR POWER SYSTEM A typical solar power device is comprised of solar panel or photovoltaic panels, a charge controller, a power inverter having a meter or monitoring system which is capable
• 12. 12 of monitoring voltages and system condition and the electrical distribution system (Ezugwu, 2012). Figure 2.5 Block diagram of system components (Ezugwu, 2012). 2.6 LACK OF AWARENESS Awareness of existence of solar energy as a source of power supply is still very low in Nigeria. Those that are aware of it thought solar energy can only power few watt of lightning. They are not aware of the fact that solar PV is in modular form and can be connected in series and parallel to achieve the desired power output. Solar thermal can produce heat by combining temperature and mass (water or hydrogen and so on) running into Kilowatt or Megawatt to run turbine that can generate equal amount of electric power as the existing conventional power supply. It has also been observed that Charge controller Battery Inverter AC Loads DC Loads Module
• 13. 13 solar energy awareness is very low in Nigeria. To many Nigerians on the street solar, PV application seems more of science fiction than reality (Okafor and Joel, 2010). 2.7 TECHNOLOGY OF EQUIPMENT AND FABRICATION Presently, neither the technology of equipment nor its fabrication is on ground in Nigeria, which means that virtually all the solar equipment in the Nigerian market that is of commercial value are foreign. These make spare parts repair, and sometimes servicing of broken down solar equipment very difficult. It also create time lag between breakdown period and repairs, and in some cases repair of equipment are never possible. In the case of inverter, which is at present widely used in solar hybrid energy supply; whenever it breaks down, it is always referred back to the manufacturers’ repair laboratory. Most of the available equipment in Nigeria in the area of P.V are imported into the country by unqualified personals or vendors; the result of this is that equipment which are technically suitable to Nigerian nation could not be distinguished or certified by them when importation is carried out (Akinboro et al.,2010). 2.8 COMPONENT FAILURE Component failure occurs when a fully installed operational device such as street light or home device becomes un-operational shortly after installation. Since the process of solar energy is very new in this part of the world, users get turned off; especially if it does perform up to the years of guarantee which the equipment is rated With experience, equipment and component failure occur mostly with such ones that does not carry manufacturers address, hence guarantee (Akinboro et al.,2010).
• 14. 14 CHAPTER THREE 3.0 MATERIALS AND METHOD 3.1 COMPONENTS OF AN INVERTER. The inverter as an electronic device which can convert low voltage from a DC source to high voltage, it has a lot of electronic components which are connected in an appropriate manner in other to work effectively. Some of the equipment as studied are listed below. 1) 2 Resistors 470 ohms ¼ Watt 2) 3 Resistors 22 ohms 1 Watt 3) 1 Variable resistor 10K 4) 1 Capacitor 1µF 5) 1 Capacitor 220 µF 6) 1 Zener diode 8.2V 7) 1 IC CD4067UB 8) 1 IC 7809 9) 1 Transformer 12+ 12/240 (500W) 10) 2 Transformer D313 11) 12 Power Transistors TIP35C 12) 2 Heat sinks to fitted over the power transistors 13) Wiring wires used in the connections. There is only one variable resistance in this circuit diagram which is used to adjust frequency of 240 AC output current.
• 15. 15 3.2 PARTS EXPLANATION FOR DC/AC INVERTER 1) Inverter IC for oscillator: - This logic inverter is used to make about 40 Hz to 70 Hz square wave. 2) Regulator IC for the voltage creating of +5V: - This IC is used to make stable +5V from 12V. 3) IC socket: - This socket is used to mount 4069UB. It is ok even if IC is mounted directly on the printed board. 4) Transistor for FET drive (2SC1815): - This is the transistor to drive the MOSFET with the square wave signal by 4069UB. The output oscillator is converted into the 0V to 12V to control the FET with this transistor. 5) Variable resistor for the frequency adjustment: - This is the variable resistor to adjust an oscillation frequency. 6) Capacitor for oscillator 7) Resistors. 8) Multilayer ceramic capacitor for power bypass: - This capacitor is used to pour the high frequency component of the power into a ground. 9) Electrolytic capacitor for power bypass: - This capacitor is used to pour the low frequency component of the power into the ground. 10) Transformer: - It is used to step up the voltage. 11) Power MOSFET. 12) Heat sink. A FET is used in the ON condition or the OFF condition. The electricity consumption of the FET is small.
• 16. 16 13. Fuse: - Fuse is put to protect when the excessive input current flows. When the oscillator stops, the switching of the input current stops and there is a big electric flows on the secondary side of transformer. 3.3 STAGES IN INVERTER WORKING PRINCIPLES. The inverters to be used in the installation consist of different stages coupled to perform a specific purpose of DC/AC conversion. The stages involved in the construction of the inverter include; i. Sourcing stage ii. Regulatory stage iii. Oscillating stage iv. Driving stage v. Transformation stage vi. Output stage vii. Change-over stage viii. Battery charging stage 3.3.1 SOURCING STAGE This stage consists mainly of direct current (DC) battery and in this case is from solar panels. The battery provides 24V direct current (DC) supply to the inverter system. 3.3.2 REGULATORY STAGE The regulatory stage consists of an IC voltage regulator. This is three pin 9V IC voltage regulators. It is a simple precision regulator that regulates the supplied voltage
• 17. 17 down to 9V from the battery. The regulated voltage is then used by the oscillator to come on. 3.3.3 OSCILLATING STAGE The oscillating stage is the heart of the inverter design. An oscillator is essentially an electronic circuit design to produce an alternating current signal of known frequency and waveform. The inverter system needs to generate signals at a frequency of 50 Hz. As a result, there has to be a kind of oscillator circuit for this to be achieved. Here, a Pulse-Width Modulation (PWM) regulator controller IC is used for the oscillator circuit. It is a common IC which has an internal RC (Regulator Controller) which could be made to oscillate to frequencies in excess of 1Mz depending on external component used. The IC contains various sections such as ERROR AMPLIFIER, SHUTDOWN, +5V REGULATOR, COMPENSATION and all of these are used to control the inverter. The advantage of using the PWM regulator/controller IC is that it gives a low harmonic content in a frequency which is suitable for the induction load. The PWM IC was 9V regulated supply voltage and generate signal at the frequency of 50 Hz which is sent to the driver for the amplification through the pin 11 and 14 of IC. 3.3.4 DRIVING STAGE The driving stage is required to drive the current derived from the output of the oscillator to the amplifier. The stage consists of Metallic Oxide Semiconductor Field- Effect Transistor (MOSFET) which has high impedance. The transistor used are both PNP and NPN transistor which are connected in a push-pull arrangement.
• 18. 18 The MOSFET is driven by the signal output of the driving stage thus controlling the voltage at the gate of the MOSFETs which result in the MOSFETs channel being alternatively switch ON and OFF. That is, when one second MOSFET channel switches ON, the first MOSFET channel switches OFF. The switching action of the MOSFET channel which is a crucial process in the outlet section is done repeatedly 50 turns per second, that is, at frequency of 50 Hz. 3.3.5 TRANSFORMATION STAGE Here, a step-up transformer is used. It is a type of transformer used for increasing voltage to a circuit. The step up transformer consist of two coils called the primary and secondary coils, wound round a soft iron core that is made of this type of transformer is however greater than the number of turns of the primary coil. The alternating current which entered into each end of the primary winding induced an alternating current at 50 Hz in the secondary winding of the transformer and the alternating voltage is stepped up by the transformer causing it to become 240V. The output voltage of the secondary winding is transferred to the socket outlet of the output of the inverter system. 3.3.6 OUTPUT STAGE In this stage, the AC voltage produced by the inverter reaches output socket outlet. The voltage at this point is found to be 240V alternating current is kept constant by the action of the Pulse Width Modulation (PWM) of the IC. Also, the expected load is connected through this socket outlet so as to power it.
• 19. 19 3.3.7 CHANGE-OVER STAGE The change over stage takes the center stage when the alternating current main power supply is off, then the yellow LED indicator comes on indicating that the inverter has started to operate on the battery mode and when the alternating current supply returns, the green LED indicator is on, then inverter automatically switches to the alternating current main supply mode and the battery charging process started. In this process, a three single pole relay is used for this stage such that it automatically switches from AC mains to battery mode when it returns and stops drawing voltage from the battery hence, the AC mains supply at the inverter system is directly sent to the inverter output socket. 3.3.8 BATTERY CHARGING STAGE The stage comprises of the transformation stage using a step down transformer and a rectifying stage. The step down transformer used, steps the main supply from its initial 240V to 24V when the inverter is on main supply mode while the rectifier converts the voltage into DC voltage. Thus, the battery is charged. 3.4 PROTECTION CIRCUIT The other protection circuits used in the inverter system include. i. Low battery shutdown circuit ii. Overload protection circuit iii. Trickling charging. Low battery shutdown circuit: The inverter gets its voltage and current from the battery. When the battery become discharge usually at 20V which is below a set voltage. The inverter should switch off. However, if the inverter continues to draw from the discharged battery, the battery will get damaged. A low battery cut off circuit is used to switch off the
• 20. 20 inverter regarding this situation, by stopping the oscillating section. This sends shutdown pin 10 of the PWM controller IC. 3.5 BLOCK DIAGRAM OF AN INVERTER. Below is the block diagram of an inverter showing sections (stages) in an inverter? Figure 3.5 Basic block diagram of an inverter.
• 21. 21 3.6 THE COMPLETE DIAGRAM OF AN INVERTER SYSTEM Figure 3.6 Complete Diagram of an Inverter System 3.7 INSTALLATION OF THE INVERTER The step by step approach taking in the construction of this project started with the purchase of inverter, solar panels and battery. The inverter which is the case study was critically studied with keen interest on the power rating; it was then re-coupled back for proper installations with the rest of electronic devices mentioned above. The tools and instrument used include. i. Copper stripping knife
• 22. 22 ii. Cutter iii. Razor blade iv. Pliers v. Digital multi-meter To conform to the requirement of this project, enquiry was done on the type and model of each electronic component that must be connected together to work and function accurately in powering the laboratory. In other to achieve accuracy in the installation, some necessary adjustments were made to some of the devices used.
• 23. 23 CHAPTER FOUR 4.0 ANALYSIS, TESTING, DISCUSSION AND RESULT 4.1 LOAD EVALUATION AND POWER CONSUMPTION Based on the table below i. The AC systems were entered in their appropriate table. ii. The electrical appliances to power were listed. iii. The number of hours per week for each item was specified. iv. The operating watt of each load was recorded v. The operating wattage and the number of hour per week were multiplied out to determine the watt hour per week. There was need to determine the size of the load that were powered. The unit of measurement used was watt-Hour because it was applicable to both AC and DC circuits. The table below shows the average weekly watt hours, the highest AC load in watts, the total AC connected wattage at a time in a week, the total watt-hour per week. These had allowed for easy determination of how many modules that were needed to produce the power required and how many batteries that were also needed to store the power. The table below was an analysis of energy usage for a representative of the Laboratory. The loads were itemized for its individual run time per week then summed the watt hour of all the units for a total weekly watt hour figure. The chart below helps for
• 24. 24 clear understanding of where the power had gone to and it also gave an idea of how to reduce the loads in the most effective manner when required. Table 4.1 Load Evaluation and Power consumption S/N Appliances Load (Watts per unit) Quantity Load(Watts) total Weekly hours of actual utilization Weekly Watts- Hours 1 Bulb 40W 10 400W 15 6,000 2 Soldering iron 60W 5 300W 8 2,400 3 Fan 15W 8 120W 10 1,200 4 Autoclave 140W 1 140W 2 280 5 Computer 80W 1 80W 4 320 6 Water bath 60W 1 60W 6 360 7 Electric Blower 40W 3 120W 2 240 Total 435W 1220 47 10,800Wh Total weekly Watts-hours = 11,800Wh 4.2 CHOICE OF COMPONENTS FOR SOLAR ENERGY POWER SUPPLY FOR 1000 WATT LOAD The choice of 1000W is a sample case and this can be extended to any required capacity. To achieve a solar power capacity of 1000watts the capacities of Solar panel, Charging Controller, bank of battery and Inverter are determined. The values cannot be picked abstractly and hence, their ratings and specification have to be determined through
• 25. 25 calculations in other for the system to perform to required specifications. For this design 12 hours was assumed for the duration of the operation and the calculations is done as indicated below: 4.2.1 SOLAR PANEL Total load = 1000W Period of operation or duration = 12 Hours Then, Total Watt-Hour = 1000×12= 12000w-hr The period of the solar panel exposed to the sun = 8 Hours (Averagely between 9am and 3pm) Therefore solar panel wattage = 12000Wh 8Wh =1,500𝑊. Hence solar panel of 1,500W will be needed for this design. If solar panel of 150W is to be use the number of panels to arrange in parallel to achieve 1,500 Watt will be: No of panel = 1500W 150W =10 This shows 10 of 150 Watt solar panel will be required for this design 4.2.2 CHARGING CONTROLLERS For this design of 1000W solar power supply P=IV Where I is the expected charging current and V is the voltage of the battery and = 12 V P is the power supply rating= 1000W Hence I = P v = 1000 12 =83.3𝐴𝑚𝑝𝑠. Since the value 83.3 A Charging controllers is not readily available in the market then 1000A charging controller will be used.
• 26. 26 4.2.3 BATTERY CAPACITY Given that the total load P = 1000W and Operational period = 12 Hours Watt/hour capacity = 12,000 W/h To make the chosen battery to last long it is assumed that only a quarter (¼) of the battery capacity will be made used of so that it will not be over discharged therefore hence the required battery capacity will be 12, 000 × 4 = 48,000 W/h Now the choice of battery hour depends on A-H rating of the storage battery. For example, for 200AH, 12V battery the number of batteries that will be needed is 48000 200 = 240 batteries. Also for a 1500AH, 12V batteries the number of batteries that will be needed is 48000 1500 = 32 batteries. Hence, for this design and to avoid too much weight and occupying unnecessary space, 15000AH 12V battery should be used, Therefore the total number of storage battery required for 1000W solar power supply system = 32 Batteries. 4.2.4 BATTERIES AND BATTERIES SIZES OF THE SOLAR SYSTEM As mentioned above, the batteries in use for solar systems are the storage batteries, otherwise deep cycle motive type. Various storage is available for use in photovoltaic power system, the batteries are meant to provide backups and when the radiance is low especially in the night hours and cloudy weather. The battery to be used: i. Must be able to withstand several charge and discharge cycle ii. Must be low self-discharge rate iii. Must be able to operate with the specified limits. The battery capacities are dependent on several factors which includes age and temperature.
• 27. 27 Batteries are rated in Ampere-Hour (AH) and the sizing depends on the required energy consumption. If the average value of the battery is known, and the average energy consumption per hour is determined. The battery capacity is determined by the equations 2a and 2b 𝐵𝐶 = 2∗f∗W V (battery ) (2𝑎) Where: 𝐵𝐶 = 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑓 = 𝐹𝑎𝑐𝑡𝑜𝑟 𝑓𝑜𝑟 𝑟𝑒𝑠𝑒𝑟𝑣𝑒 𝑊 = 𝐷𝑎𝑖𝑙𝑦 𝑒𝑛𝑒𝑟𝑔𝑦 𝑉 ( 𝑏𝑎𝑡𝑡𝑒𝑟𝑦) = 𝑆𝑦𝑠𝑡𝑒𝑚 𝐷𝐶 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 The AH rating of the battery is calculated as: Daily energy Consumption (KW) Battery rating in (Amp−Hr) at a specified voltage (2𝑏) 4.2.5 INVERTER Since the total load is 1000W it is advisable to size the required inverter to be 1500W as designed for solar panel ratings. Hence 1500W pure sign wave inverter is recommended in other to prolong the lifespan of the inverter. 4.3 PROCUREMENT During the process of procuring all the materials used for this project, taking the right decision for the battery, inverter, solar panel and the charge controller was totally based on the result of their individual evaluations. The materials; solar panel, inverter, batteries and the charge controllers where all ordered. 4.4 DETERMINATION OF INSTALLATION SITE
• 28. 28 Solar system cannot be installed at any kind of position because of the nature of the Natural need, the system requires for it to function properly. The choice of installation site must first of all be sorted out and determined to avoid error in the angle at which the modules are suppose to be mounted so that the solar panels can tap enough solar rays for a longer time because the sun is not at a fixed position for it change position with time. 4.4.1 MOUNTING OPTIONS The PV was mounted on a roof. The PV system produced 5 to 10 watts per square foot area. This was based on a variety of different technologies and the varying efficiencies of different PV products. 4.4.2 ROOF MOUNT Often the most convenient and appropriate place to put up the PV array is on the roof of the building. The PV array was mounted above and parallel to the roof surface with a stand-off, several inches for cooling purposes. The 1000 watts PV system needed about 40 square feet of unobstructed area to site the system. Consideration had to be given for access to the system. This access to mounting had added space up to 2% of needed area to the mounting area used. As the PV system was properly mounted, it was labour intensive. Particular attention was paid to the roof structure and the weather sealing of roof penetrations. It was typical to have two support brackets for the 1000 watts of solar panel modules. During the installation, support brackets were mounted for holding the solar panel.
• 29. 29 4.5 INSTALLATION PROCEDURE Basic steps that were followed while installing the PV system i. It was ensured that the roof area for installation was capable of handling the system area or size. ii. It was ensured that there were no roof penetrations that needed roofing industry approved sealing methods. iii. The PV system was installed according to the manufacturer specifications, using installation requirements such as the right wire gauge, nuts and bolts from the manufacturers’ specification. iv. The PV system was properly grounded with the system parts to reduce the threat of shock hazard induced surges. v. It was ensured that the right wire with the right polarity was observed while connecting the solar panel to the charge controller. vi. It was ensured that the design met local utility interconnection requirement. vii. It was finally inspected for completion by the HOD of the department.