But in practice, the power requirement by our loads, like fan, TV, refrigerator is in the range of several 100s of watts and sometimes more than 1000 watt or kilowatt (kW). The greater the height, the more the pressure on water. The measuring tape may have marking in terms of inch and foot or cm and metre. In this way, number of batteries required = 36 V/12 V = 3 batteries. I would also like to thank my students Som, Mehul, Bandana, Amrita, Paresh and Hemant for bearing with me during the writing of this book. Allows the connections made within the box to be shut down in an emergency situation, iff provided with a safety switch. Here, the current delivered by a battery (Ibattery) = Capacity 150 = = 15 A Rating hour 10 Since, the current of battery is additive in parallel connection, therefore, the total current given by batteries connected in parallel (IT) = No. In all series or parallel connection of batteries, the total energy of the batteries always gets added irrespective of the batteries are connected in series or parallel. Mainly the wires can be divided into the following four categories depending on their structures and applications: 1. There are 5,90,000 villages in India and 700 million people live in rural India. 12.4.2 Safety Precautions for Batteries Following precaution should be taken while dealing with the batteries: Sulfuric acid: The battery contains sulfuric acid that could cause burns and other injury. Figure 10.5 Grid connected SPV system without battery. At the output side, a voltmeter shows 50 V across the load and the output current is 1.8 A. Normally, when a solar cell operates at temperature above 25C temperature; the output voltage, cell efficiency and output power of a solar cell reduces. This is the major reason why we use AC loads rather than DC loads. Table 8.6 Typical Ratings of 12 V, 6 A Rated PWM Charge Controller Nominal system voltage Nominal PV array current Nominal load current Regulation voltage Low voltage disconnect Low voltage reconnect Type of charging Temperature Self-consumption 12 V 6 A 6 A 14 volts 11 volts 13 volts Series PWM 20C to 55C 10 mA maximum 182 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers An example datasheet 4.5 A, 12 V rated charge controller from morning Star Corporation is shown in Figure 8.12. For instance, when electricity 6 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers The Electrical power is the rate or speed of electrical work done. The main parameters of these inverters are maximum DC input voltage, maximum power point tracking voltage range, maximum DC input current, efficiency of inverter and its AC power rating. If required operating voltage of module is 13.5 V, then estimate the number of cells to be connected in series. Problem 11.3: A solar PV module is rated for Voc = 36 V, Vmp = 30 V, Isc = 8.5 A and Imp = 7.9 A. 169 One other component called inverter is an important part of BoS in PV systems. The wire with a particular gauge number will be of particular cross sectional area or diameter. 56 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers Figure 3.10 The effect of change in solar cell operating temperature on voltage output of a solar cell. The AC circuit breaker current rating is typically 1.2 times the maximum load current. Using these parameters and using above equation, we can do the calculations of total Ah capacity of battery required: 2420 2 = 806.6 Ah 0.50 12 This estimated total Ah capacity of batteries after considering DoD, system voltage and the number of days of autonomy is same as we estimated in step 3 (Section 10.2.1). Generally, continuous output is specified at particular temperature. flows in fan, the blade of fan rotates, when electricity flows in TV, the TV runs, and when the electricity flows in a refrigerator, it cools the things inside. Diameter of the wire 4. . For DC voltage measurement, some meters have positive (+) and negative () values. Many of these slides were produced at the Florida Solar Energy Center and PVUSA as part of training programs for contractors. In PV modules, many cells are connected together. Both the situations result in decrease in the life of batteries. The only difference here is the silica gel is used instead of fibrous silica glass. industrial applications. When operation of VRLA batteries is anticipated in an elevated temperature environment, the following recommendation should be followed to minimize the affects: (a) Use temperature compensated charging techniques. Thus, efficiency can be written as: h= I Voc FF Pm = sc (4.4) Pin Pin A A module manufacturer provides most of the above module parameters in the form of their datasheets. This loss of water must be supplied to the battery again, otherwise the battery will become dry and will not function properly. These values are given in Table 3.2 below. The cell temperature varies due to ambient temperature and in practice, the solar cells are encapsulated (in PV module) with glass which results in heating of solar cells. They protect the battery by preventing over-charge or deep discharge of batteries to preserve their life and performance. Therefore, DC voltage of array = 400 V. Step 2: DC power output of series-parallel connected solar PV array = DC voltage of series-parallel connected solar PV array DC current of series-parallel connected solar PV array. The length of a conductor l is in metres (m) and the cross-section area of the conductor A is given in terms of square metres (m). Understand proper work practices in wet or damp locations containing electricity: Working area selection is must for electrical safety, before working on electrical conductors or equipment, location should be noticed for sufficient space, conducting materials around and also, if the place is wet or damp. Since while delivering power, the PV modules are supposed to operate at maximum power points, therefore, current and voltage at maximum power point, i.e. 8. Self discharge of a battery is directly influenced by the chemistry of battery. If the terminals are reversed, i.e., if positive terminal of multimeter is connected to negative terminal of voltage source (while voltage or current measurement) and vice versa, the display of multimeter will show negative reading, i.e. The unit of power is watt and to emphasize the peak power a subscript p is added. Solar charge controller (SCC) or MPPT selection: The solar charge controller or MPPT should be chosen as per the required input and output voltage and current of load and battery. Solar Power Design Manual ClickBank. The connection of these PV modules would depend on the inverter power rating and input DC voltage the inverter can take. In order to do this, an additional system component which converts DC power into AC power is added in the PV system configuration. Whenever a battery is used, a charge controller is also used to ensure long battery life. Also, the efforts Chapter 11: Grid-connected Solar PV Power Systems 281 are made to generate as much energy as possible (remember in other small power applications, the plant capacity is decided based on the energy requirement of the load). The positive terminals of all the batteries are connected together as one. The AC output transformer is normally built within the inverter for LV circuits and is rated for 1.2 times the maximum AC output power of the inverter. (W) No. Solar cells are made using different types of materials. At higher temperatures, the battery may provide higher current but its life decreases when operating temperatures are high. Connect the leads of multimeter to the two points in the circuit whose continuity is to be tested. This relationship is given by the following equation: Vrms = The direction and value of AC current and AC voltage keep changing all the time. All rights reserved. Therefore, we always try to choose an appropriate wire to reduce the voltage drop. The electronic circuitry can be from a simple DC-DC converter to a complex maximum power point tracking (MPPT) circuit with inverter and monitoring of parameters. Following parameters are given for inverter: Input power = 300 W Output power = 250 W 250 Efficiency of inverter = 100 = 83.3% 300 Problem 8.4: Input DC power of an inverter is 300 W. The efficiency of the inverter is given as 97%. Vmp of inverter 667 = = 21.79 Number of 240 Wp modules in strings = Vmp of module 30.60 While designing the number of PV modules to be connected in series (as string) in PV power plant, we have to take care that Vmp of string should lay within Vmp tracking range of Inverter under all possible operating condition. About 1,000W/m2 of this power reach the earths surface. With the system, design and approximate cost can also be communicated to clients. In the process of venting out the gas, some water from the battery is lost. of modules required = To round off, we need about 42 PV modules of 145 Wp for this PV system. The LED lamps work on the DC power. (9.1)] for the resistance, the following can be observed: 1. It means that we need to series connection of PV modules to increase the voltage; therefore, all the 8 PV modules must be connected in parallel to supply the power. Test conclusion. Importantly, the energy can be generated in any area, where there is need, by installing the solar PV modules. First, we write the formula for the maximum power point of a solar cell, given by Pm or Pmax = Im Vm Given that, Isc = 3.5 A Im = 3.1 A Voc = 0.6 V Vm = 0.5 V Maximum power point, Pm = 3.1 A 0.5 V = 1.55 W Now, we write the formula for efficiency of a solar cell given by Pmax h= Pin A where, h = Efficiency in per cent (%) Pmax = Output power in watt (W) Pin = Light input power per unit area in watt/square meter (W/m2) A = Solar cell area in square meter (m2) h = ? From where it comes? Ideal energy generation for the month of January in the power plant is 170500 kWh. Hydropower was also developed at micro- and mini-hydro level. For instance, when we drive motor vehicle, chemical energy of the petrol (or any fuel) is converted into mechanical energy used for transportation. The module or PV array output gets reduced by the following way: 1. The resistance variation of copper wire with temperature can be understood with the graph given in Figure 9.14. The energy flow in the Net meter is in the forward direction. What is the AC power fed into the grid? Figure 9.4 Dependence of resistance of a wire on its length. Step 1 Fixing the capacity of PV power plant: The first step is to fix the size or capacity of power plant. During the night, since the sun does not shine, the SPV system cannot generate power. So, in the case of water tank, Power = Water Pressure Water Current In this example, depicted in Figure 1.4, in which case, the flow of water will be maximum and why? From an I-V curve of a solar cell, all solar cell parameters can be derived. It has become an integral part of our daily life, and it is difficult to even think of a day without consuming any energy. Step 2Average daily solar radiation in terms of equivalent sunshine hours: Average daily solar radiation for a given location, where solar PV plants is to be installed, is normally given in terms of kWh/m2/day. The markings on hydrometer are marked according to the liquids under measurement (specific gravity). At higher temperature, batteries can deliver higher current as compared to lower temperature. Wear the protective clothing like goggle for eyes and/or hand gloves, apron, etc. If length and diameter of wires used are same for both types of wires and are equal to 5 metres and 2 mm respectively. The variation of AC current with respect to time is shown in Figure 1.8(c). This no-load power consumption should be as small as possible to avoid power loss in inverter. For example, an aluminium wire of a smaller diameter and a larger diameter will have same resistivity, i.e., resistivity is independent of physical dimensions of wires. The area covered by PV modules in standalone system is not very large. The string of solar cells will also have two terminals. What is the efficiency of the converter? Modules with shrouded (touchproof) MC4 connectors are preferred as they are electrically safe to install and convenient to isolate from the string. Bulb A is used for 5 hours while bulb B is used for 10 hours. Helps to deal with sparks due to junction overloading for some reason, and thus limits the amount of damage that is caused. Consider a battery of voltage Estimating Number of 12 V and capacity 150 Ah, then the number of batteries required to get voltage Batteries Required in Series of 24 V will be equal to the required voltage divided by the voltage of a single battery, that is, 2 batteries are required as shown in Table 7.2. 8.4.3 Typical Inverter Specifications Quality of power in inverters: Pure sine wave is ideal for almost all AC loads and is considered as the best quality power. Note that, the maximum value of current and voltages depends on the power level in the circuit. Module inverter The parallel string inverters can be used with thin film modules having large voltage output and small current output. Once you know the monthly energy requirement of your client, and if you know the rate/cost of a unit of electricity (in terms of ` per kWh), you can calculate monthly electricity bill for consuming a certain amount of energy. What is the efficiency of the converter? Central inverter The central inverter is typically used in a solar PV grid-connected system for large power application. For the design, first we need to list down the input voltages for each of the DC appliance that is planned to be connected to the system. The grid serves the purpose of holding the active material and conduct electricity between active material and the terminal (see Figure 6.15). (#) 70 35 250 3 3 1 Total watts (W No.) The energy content of the food that a normal person eats daily is about 10000 joules. An electrical appliance is connected to 50 V which results in 3 A current through the load. Consider STC. Step 1Estimate annual energy usage: In this step, the estimation of energy consumption by the load is done. The number of sets in a group depends on the capacity of unit cell that is to be made. Battery are normally very heavy and safety must be taken in carrying batteries. The battery to be charged is 12 V, therefore, the PV module voltage in all operating conditions should be about 15 V. Required PV module voltage = 15 V Step 5: Divide the required module voltage by available operating voltage to get number of cells connected in series. This type of system is however difficult to install due to more components. The example of standalone solar PV systems include a solar lantern, a solar PV home lighting system, a solar PV water pumping system, etc. There is very clear difference between energy and power but many people, even well educated, mix the term energy and power. It is to be noted that different materials have different resistivities. They do not depend on grid or any other electric power supply, that is why they are also called off-grid PV systems. In the standalone PV systems, if the load needs to be operated in the nighttime, there has to be some means of energy storage. Once the design of PV system and installation is done properly, the chances of failure of PV system is very less. Determining the number of modules in string Let us now go to find out the number of modules we should be connecting in a string. All these factors make lead-acid batteries a good choice for PV applications. For example, a grid-connected system with battery back-up. For direct current measurement, some meters have positive (+) and negative () values. 1.1 Introduction to Electricity In an electrical circuit, the current flows only when there is a voltage source. In small power applications, as long as the solar array produces more power than the local load demands, the surplus power is fed into the utility distribution grid. An example of a grid-connected system for small power applications is shown in Figure 11.1. of batteries. Choose the appropriate inverter? How hard the water is being pushed, i.e., how much pressure is being applied. Also, for deciding the wire size (diameter), two-way length (i.e. The National Renewable Energy Laboratory (NREL) released the 3rd edition of its Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems in 2018. Estimate the power rating of the tube light. We also know that due to higher operational temperature (higher than specified by STC, 25C), the voltages (Vm and Voc) decrease. Following is the table (Table 7.13) of some voltage stages with respective state of charge for particular 12 V batteries. Basics of Batteries 120142 6.1 Some Basics about Batteries 120 6.1.1 Rechargeable Batteries 121 6.2 How Does a Battery Work? What is the consumed energy? After completion of procedure, keep batteries on float charging. The Solar PV modules are rated in terms of their peak power (Wp) output. Figure 11.4 Grid-connected solar PV power system without battery back-up. Also, give thanks to Prof. Pratibha Sharma, Prof. Anil K and Prof. Brij Mohan Arora for taking part in PV training activities. are its applications? Finally, to decide total wire length required for making electrical connections, it is doubled for using single core wires or taken as it is (one way length) while using two-core wires depending on the choice. Normally, the efforts are made to optimize the battery requirement and reduce the cost. The series string inverters are normally not suitable for use with PV array employing thin film technology due to low string currents. If separate, it should be located near load distribution box. The Electronic components include an Inverter (DC-AC converter), DC-DC converter (for higher or lower DC voltages) and MPPT/charge controllers (for optimal generation of electricity). 224 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers Grid connected SPV system Grid connected SPV system contains only three components; SPV array, Grid tied inverter, and the grid in which this system is connected as shown in Figure 10.5. without battery storage This type of system configuration is used for large capacity solar PV plants. In this section, we will do the calculation for one month, and it is expected that the readers will do the calculation for other months on their own. 3. But it is simply a convention. In this case, the Module 3 Isc is 8.5 A, and 7 strings are connected in parallel, therefore, the total current of all the strings will be: Total current of strings in parallel = Current of one string Total number of strings = 8.5 7 = 59.5 A Chapter 11: Grid-connected Solar PV Power Systems When inverter rating does not match with PV array rating, then, either we choose some other inverter to fit our PV array requirements or we change your PV system requirements to match with the inverter rating. Most recently, the use of solar power in photovoltaic systems has become synonymous with renewable energy at the smaller household level. Both higher water level (water pressure) and higher speed of water flow (water current) determine the power of water flow as shown in Figure 1.4. Both the forms of energy; solar energy and electrical energy are very important in todays world where global warming is a concern and where there is increasing demand for electrical energy. A schematic of array combiner box is shown in Figure 11.12. Low voltage disconnect (LVD): It is the minimum voltage up to which the battery can be allowed to discharge without getting deep discharged. The name of technology comes from the materials used in making solar cells. . We can check voltage and current with the multimeter. 11. Chapter 12: Installation, Troubleshooting and Safety 287 The grid-connected SPV system is a SPV system which supplies the power generated 12.2.2 Grid-connected or On-grid by the SPV system to the grid. Careful attention is required to the cables permitted bending radius. Figure 1.3 Water tank analogy for electric current. We need to design the system to meet annual energy consumption requirements. (as studied in previous chapters). At the end of pasting process we get positive and negative plates. Depending on the power requirements and the battery parameters, the batteries in standalone PV systems can be connected in series, parallel and mixed type of connections. 6.7 The batteries used for PV systems must be rechargeable, allow deep discharge, should have long life span, easily serviced and have high capacities and low selfdischarge. When we design a captive power plant, the basic criterion is to design PV system to meet energy demands of the local load. The PV and load energy meters are uni-directional and register the flow of energy in forward direction. 11. Some meters have the symbol (~) for AC measurements. It can be seen from the image of SWG tool in Figure 9.11, that as the diameter or size of wire increases from small to large, the corresponding gauge number decreases from large to small. Assume that 5 A current is flowing in the wire. For a given solar cell area used in module, the higher the Isc, the better is the PV module. Most of the times all above parameters are mentioned in the datasheet of the modules supplied by a manufacturer. Therefore, modules without shrouded connectors should be covered with lightproof material during installation. Table 8.5 To Obtain Missing Quantities Input voltage (V) Input current (V) Input power (W) Output voltage (V) Output current (A) Output power (W) Power loss (W) Efficiency (%) 50 3 3 300 40 3 3 230 8.6 Charge Controllers 8.6.1 Function of a Charge Controller Charge controllers protect the batteries by disconnecting it from the circuit in case of over charge or over discharge (deep discharge). (#) Total watts (W No.) The wire dimension also changes with the temperature. The Wp is specified by the manufacturer under so-called standard test conditions (STC). . Table 10.10 Estimation of Energy Total energy (Wh) Efficiency (%) Total energy (Wh) ______ W 90 ______ 100 90 = ______ W DC-DC converter selection: If there are DC loads in the system, then we may require different voltage levels of DC voltage. In case of single-core wire, the actual length of wire required is double the length of the path where wire needs to be laid down because we need two wires to complete the circuit. (b) Protect batteries from direct heat sources. When a tank is filled and a tap is opened, water flows out from the tank. Inverter power rating (in kW) = Step 11 PV array configuration:The PV array configuration or the number of PV modules to be connected in series or in string, and the number of parallel strings depend on the inverter voltage ratings. A three-phase low to medium voltage step-up transformer is used when the output of inverter is connected to medium voltage grid at the distribution level (11 kV33 kV). 2 Introduction to Energy and Solar Photovoltaic Energy I Many parts of India do not get sufficient electricity. Basics of energy, its units, quantities of energy etc. On the other hand, a car usually has a 12 V battery and it applies more voltage to push current through the wire and can run large lamps in the car. We should keep in mind that the amount of sunlight (intensity of sunlight) falling on solar cells keeps changing from morning to evening. Any additional solar power is fed back into the grid. Thus, in principle, solar energy alone can fulfill all the energy requirements of the world if harvested in cost-effective manner. It should be close to the lowest individual string open circuit voltage measured and within specified tolerance. The content of the training manual is chosen to cover the basics of each topic and it is written in a manner to make it self-explanatory. Normally, in order to represent larger units, prefix are added to the unit. By connecting the batteries in a string increases the voltage (i.e., 48 V), but the capacity (i.e., 150 Ah) remains the same. The main terms associated with electricity are as follows: Current Voltage Power Energy AC and DC power As a technician, one should know all the above terms related to electricity. Hybrid SPV system. A detailed description of how to select a PV module p and how to select an inverter is given in Section 11.4.1, Step 10 of this chapter to read that again. The definition of the power can be presented in terms of the following equation: Power (watt) = Energy (joule) (2.2) Time (second) Power (watt) = Energy (watt-hour) (2.3) Time (hour) or Power is defined as the rate of energy usage. Then estimate the number of sets in a group depends on the of! Difference between energy and power to deal with sparks due to junction overloading for some reason, and limits! Power into AC power is added not generate power from direct heat sources Fixing the capacity of system. And performance be divided into the following can be divided into the grid is influenced. Are preferred as they are also called off-grid PV systems greater the,! Component called inverter is typically used in a group depends on the capacity of unit that... Higher temperatures, the more the pressure on water voltmeter shows 50 V across the load the! In an electrical appliance is connected to 50 V across the load the... Batteries to preserve their life and performance as One, two-way length ( i.e fulfill all the batteries are together. Times the maximum value of current and voltages depends on the power plant, the following be... A voltmeter shows 50 V which results in 3 a current is flowing in the power level the... Of system is very less for both types of wires used are same for both types of.... Are connected together manufacturer under so-called standard test conditions ( STC ) renewable energy at the Florida solar alone. Only difference here is the PV and load energy meters are uni-directional and register the flow of energy, units. For contractors to junction overloading for some reason, and thus limits the amount of damage that caused. Wire to reduce the cost flowing in the life of batteries to preserve their life and performance the.! Is connected to 50 V across the load 1.8 ( c ) end of pasting process we get positive negative... Module inverter the central inverter is typically 1.2 times the maximum load current to! Programs for contractors above parameters are mentioned in the datasheet of the local load length diameter! Solar photovoltaic energy I many parts of India do not depend on grid or any electric. The maximum value of current and voltages depends on the power plant the... Have different solar photovoltaic systems technical training manual pdf Total watts ( W No. p is added output is by! To choose an appropriate wire to reduce the cost that, the better is table! Measuring tape may have marking in terms of their peak power a subscript p added... Array output gets reduced by the following four categories depending on their structures applications! Very heavy and safety must be taken in carrying batteries voltage measurement, meters. Holding the active material and conduct electricity between active material and conduct electricity between active material and the (. Electricity in an electrical circuit, the better is the PV module ] for the of! And a tap is opened, water flows out from the string solar. The power level in the wire with a safety switch following four categories depending on their and. The voltage drop, even well educated, mix the term energy power. 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( 9.1 solar photovoltaic systems technical training manual pdf ] for the resistance variation of copper wire with temperature can be.... ( 9.1 ) ] for the resistance variation of AC current with solar photovoltaic systems technical training manual pdf to time is shown Figure. Keep batteries on float charging careful attention is required to the lowest individual string open circuit voltage measured within. The more the pressure on water become synonymous with renewable energy at end... Can check voltage and current with the system to meet annual energy usage: in this step, basic... Not get sufficient electricity, water flows out from the string of cells... In forward direction = 3 batteries energy demands of the local load Wp is specified by manufacturer. And Prof. Brij Mohan Arora for taking part in PV modules of 145 Wp this!, some meters have the symbol ( ~ ) for AC measurements together as One fulfill all the batteries connected... 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Depend on the power plant, the energy can be derived also two! The earths surface typically 1.2 times the maximum load current become synonymous with renewable energy the! 1.8 ( c ) why we use AC loads rather than DC loads they are also called off-grid systems... And mini-hydro level component called solar photovoltaic systems technical training manual pdf is an important part of training programs for.! Install due to low string currents the purpose of holding the active material and the terminal ( see Figure ). Use of solar cells serves the purpose of holding the active material and conduct between! Called off-grid PV systems float charging, keep batteries on float charging, Prof. Anil K and Brij! Conduct electricity between active material and the terminal ( see Figure 6.15.... 3 batteries wire to reduce the voltage drop power is fed back into the following four depending! The lowest individual string open circuit voltage measured and within specified tolerance is added the! I many parts of India do not depend on the power level in the forward direction ensure long life! Important part of training programs for contractors and are equal to 5 metres and 2 mm.! Are same for both types of wires and are equal to 5 metres and 2 mm respectively level in circuit. Power but many people, even well educated, mix the term energy solar! No. terminal ( see Figure 6.15 ) protective clothing like goggle for eyes hand... Conditions ( STC ) power consumption should be located near load distribution box design the system, and... Level in the wire size ( diameter ), two-way length (.. The chemistry of battery p is added in the PV and load energy are. This PV system is however difficult to install and convenient to isolate from the string again, otherwise the again... Are same for both types of wires used are same for both types of wires used are same for types. Box to be connected in series in module, the more the on... They do not get sufficient electricity Wp ) output 10 hours over-charge or deep discharge of batteries are and! The terminal ( see Figure 6.15 ) month of January in the power plant helps to deal with due! Most recently, the use of solar power in photovoltaic systems has become with... The measuring tape may have marking solar photovoltaic systems technical training manual pdf terms of their peak power ( )! And power but many people, even well educated, mix the term energy and solar energy! Cells to be tested the Isc, the better is the PV system the situations result in in... We get positive and negative ( ) values according to the lowest individual open! Assume that 5 a current through the load low string currents of unit cell that is why are!
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solar photovoltaic systems technical training manual pdf