into electricity. Chapter 11: Grid-connected Solar PV Power Systems 261 Grid-connected inverters are available with and without transformer isolation at the output. How is current generated by it and what hydro energy, etc.) Step 1Estimate annual energy usage: In this step, the estimation of energy consumption by the load is done. The extent of degradation of AC power or the quality of AC power is measured using the term Total Harmonic Distorsion (THD). The solar PV modules are rated for solar radiation intensity of 1000 W/m2 or 1 kW/m2 (Standard Test Condition or STC). Grid-connected system for small power applications and for large power applications are little different from each other. Multi-core Single-strand wire is also called solid-core wire. Therefore, this design is acceptable and can be implemented. Remove the old battery stand if damaged. For instance, in order to design 1 MWp plant, instead of using one 1000 kVA inverter, one can also use two inverters of 500 kVA capacity. The capacity of the inverter depends on the total wattage of the load and inverter efficiency. The AC voltage protection devices are typically rated for 400 V AC for 230 V single phase circuits and 600 V AC for 415 V three phases circuits. This value should be equal to output power capacity of the inverter. Similarly, current flows due to the flow of electrons as shown in Figure 1.1. In many cases, DC load may not be connected in the system. 298 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers 12.5.9 Installation of DC and AC Power Distribution Boxes 12.5.10 Installation of Inverter Array support structure should have equipotential bonding and grounding arrangements for safe conduction of capacitive discharge currents to ground. The meter leads are connected correctly then it will read the positive value for voltage and if the leads are placed on wrong wires then the meter will read negative value. Manufacturer says that its depth of discharge is 60%. 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. Figure 10.13 shows the connection of PV modules, and Figure 10.14 shows the complete system. What is the efficiency of the converter? One good place to identify the difference between these two terms is our own house. Therefore, DC current of array = DC voltage of array 400 Step 3: DC current of series-parallel connected solar PV array = DC current of individual series-connected string Number of strings connected in parallel. When we multiply 1 W with 1,000,000 we get 1,000,000 W. Since 1,000,000 represent 1 Million or 1 Mega, in brief, the power is called 1 MW (see Table 1.1). The probe works as a link between the multimeter and points in electrical circuit where electrical quantities are to be measured. Estimate the module level losses that can occur in this power plant. As we know, Li-ion battery has a high charging efficiency. A converter can be represented by a block diagram as shown in Figure 8.1. So, the total voltage of parallel connected batteries remains the same but the capacity increases. 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). Modules with shrouded (touchproof) MC4 connectors are preferred as they are electrically safe to install and convenient to isolate from the string. If the balance is made between consumption of biomass energy (plants energy) and growth of biomass then biomass energy can also be considered renewable energy. Have final inspections completed by the concerned authority and the utility if required. Voc = 0.7 V Vm = 0.6 V FF = 68% First we write formula for Fill Factor of a solar cell given by expression below Fill Factor (FF) = where, Isc = Im = Voc = Vm = FF = I m Vm I sc Voc Short circuit current (A) Current at maximum power point (A) Open circuit voltage (V) Voltage at maximum power point (V) Fill Factor (%) We know, FF = 68% First, we convert Fill Factor (FF) from per cent to decimal by dividing it by 100. Figure 1.16 Figure illustrating the negative sign when probes are reversed while measurement current. Single-core 4. In case of contact with sulfuric acid, flush immediately and thoroughly with water and go to hospital for a treatment. The idea of the connecting PV system to the grid is to use the grid as energy storage medium so that the use of battery can be avoided as much as possible. Length of wire. Solar Photovoltaic Project Development has no graphics and smaller font text, and is intended more as a text for teachers both to support the technical training manual making it easy to relate student and teacher materials, and to discuss wider issues relating to project development for solar photovoltaic systems. With the safety margin, the Current = . Normally, DC systems operate at either of these voltage levels and allowed potential drops are also in the range of 23% and copper wire is used to reduce energy loss. Deep cycle batteries can be deeply discharged allowing to use most of its capacity (i.e., ~50% of its capacity). These fuels cannot be produced as fast as they are being consumed. But the use of DC appliances is not very common. Chapter 1: Basics of Electricity 15 Figure 1.10 Arrangement for measurement of voltage using a voltmeter. Thus, first the loads and their requirements (power, hours of operation, energy requirement, etc.) What is the difference in both cases? Since during charge-discharge cycle no water is lost, no refilling of water is required for sealed or VRLA batteries. Use predrilled mounting holes. The earliest inhabitants on the earth burned wood in their campfires for heat and since then it has been a source of energy for meeting human needs. The PV module generates direct current power or DC power (see next Section) and the battery also stores energy which is available in the form of DC power. If PV module operates at any other combination of current and voltage under STC, we will not get the maximum possible output power from the PV module as shown in Table 4.2. It indicates the square-ness of I-V curve. Chapter 9:Wires 193 The choice of wire, i.e., to choose single-stranded or multi-stranded depends on several parameters. Junction Box Figure 9.23 A typical solar PV junction box. Fraunhofer-Institute fur Solar Energiessysteme (FhG-ISE), Photovoltaic Systems, March, 1995 2. Decentralized electricity generation: Since solar radiation energy is available everywhere, the solar PV electricity can be generated everywhere in decentralized manner in small quantities as per the need, unlike the coal based power plant where electricity can be generated only in centralized manner in large quantities. For a given PV module dimensions, the higher the Pm, the better is the PV module. Two 10 W lights = ____ W A 30 W fan = ____ W Nominal system voltage Nominal PV array current Rating of charge controller Total load = ____ Four 15 W lights = ____ W Two 25 W fans = ____ W Total load = ____ 8.7 Maximum Power Point Tracking (MPPT) Power delivered by a module depends on the load connected to the module. Ensure control room is available indoors to house inverter as well as DC and AC distribution boxes. Wire size calculation using In this section, we have used the method of manual calculation to estimate the wire sizes for a particular situation in solar PV system. 12.3.4 Troubleshooting of PV System Components Troubleshooting is a logical and systematic search for the source of a problem or faults so that it can be solved. This relationship between voltage, current and resistance was given by the scientist named Georg Simon Ohm. From the above expression, if we know the energy supplied by the battery to the inverter and efficiency of the battery, then we can estimate the input energy that Chapter 10: Solar PV System Design and Integration 237 must be supplied to the battery bank (see Figure 10.12). Step 4: Determine the PV The SPV module must supply enough energy to the battery, so that battery can modules size (their number, supply enough energy to the inverter, in order to supply enough energy to the load as per the need. The solar PV power is given the first priority for use, second priority is given to the battery and the grid is given the last priority. Around the world, large amount of electricity is generated using this method. It is given that cell efficiency is 16% and cell area is A = 100 cm2. There is a huge shortage of energy supply. PV modules together with other components that are put connected with PV modules to supply reliable energy to appliances is referred collectively as solar PV system. Using that I-V data, fill in estimate and fill in the parameters of solar cell given in Table 3.3 below. If we need to increase electricity, we need to buy another diesel generator or set up another coal based power plant. Disconnect the circuit and verify if it is open by using a multimeter. This is decided by considering the allowable Vmp and Vmax at the input of inverter and Vmp and Voc of the PV modules selected for installation. The PV panel is designed for small (1 cm) gaps between modules when assembled. An example of the sum of voltage in series connected batteries is given in Table 7.1. First, we should observe the discharging cycle, means the voltage at the time when discharge starts and at end when discharge is over and measure the duration of discharge and discharge current. In the case of single-core two ways, the wire size is the diameter of single core of any one wire. Assume that grid is available full time and no battery storage is required. In Chapter 4, we see the effect of different materials used for solar cells. The battery output current and its capacity depends on the temperature. One advantage of DC electricity generated from the PV modules is that the batteries store and supply electricity in the form of DC electricity. As the diameter of the pipe increases the amount of water that can flow through it also increases as shown in Figure 1.3. Therefore, it is not possible to choose a load such that the operating point is always at maximum power point or close to Point Tracking? Most of the loads around us use AC power for their operation. As a standard, the relationship between gauge number and wire diameter is given for ambient temperature of 20C. Historically wind energy is used for sailing ships. Table 4.2 Measured Current-voltage Data Points of a PV Module Corresponding to Figure 4.6 S. No. An example of mounting structure is shown in Figure 12.5. In this case, let us design the power plant for 1 MWp capacity. It is discussed earlier that every wire has a resistance due to which whenever any current flows through it, a certain voltage drop occurs in wires. The inverter systems (with PV modules) used in India is an example of these types of systems. In case if our chosen system voltage is 24 volt, then we need to connect two batteries together in series to get 24 volt. These should be within specified limits. A = 100 cm2 = 100 104 m2 Now, we solve for light input power = 1000 W/m2 Above equation can be written as: Pmax = h Pin A We put the respective terms values and we get, 16 1000 100 10 -4 = 1.6 W Pmax = 100 Similarly, we calculate output power for other efficiencies in table form as shown in Table 3.8. For instance, when we drive motor vehicle, chemical energy of the petrol (or any fuel) is converted into mechanical energy used for transportation. Therefore, modules without shrouded connectors should be covered with lightproof material during installation. If roof mounted, verify that the roof is capable of handling additional weight of PV system. Thus, total module losses are = 13.5% + 1.5% + 1.5% + 1.2% + 2.5% = 20.2%. 12.2.3 Hybrid Solar PV System These types of system have more than one power supply. Do not disconnect module connectors under load. For solar PV system applications, copper wires are commonly used. An example of summary sheet of 1 MWp power plant is given in Figure 11.25. 4. Which bulb will consume more energy? In order to find out the number of PV modules we need to divide the total PV module power required by the single PV module power available in the market: Total estimated module power Power of single module 540 = 7.2 8 PV modules Total number of PV modules = 75 Total number of PV modules = The number of modules estimated to 7.2, which is rounded to next higher number of 8. 57 58 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers Figure 4.1 A single solar cell. Due to the cable losses, the PV array will have to produce more power. 2. As mentioned earlier that the wires of some standard diameter are manufactured. It is given that the terminal voltage of an individual cell under operating condition is 0.75 volt. Solution Step 1 Prepare AC load chart: S. No. A solar cell converts sunlight into electricity directly, without any intermediate conversion steps. Maximum Isc of the PV array should also be within acceptable limit to the inverter. The generated heat results in increase in temperature of wire and its insulation. Thus, all the objects which have ability to work are said to possess energy and by doing work the objects transfer energy. 234 Solar Photovoltaic Technology and Systems: A Manual for Technicians, Trainers and Engineers Table 10.12 System Specification Energy (Wh) Wattage (VA) Voltage (V) Maximum current (A) 2420 400 12 34 Step 3: Determining the The battery sizing should be done after the inverter (DC-AC) sizing for AC and batteries size (their number, DC loads after the selection of DC-DC converter. The Normal Operating Cell Temperature (NOCT) is defined as module cell temperature under STC of 25C. Therefore, it is recommended to store batteries at lower temperatures in order to reduce self discharge. The discovery of internal combustion engine (used in motor cycle and cars) resulted in the use of energy of the petroleum products (petrol, diesel, natural gas) to fulfill our energy requirements. 2. Surge capability of inverter: For accurate surge estimation, we need to know the surge of all individual loads. Current in the PV system can also be higher due to higher solar insolation than the Standard Test Condition (STC), or additional reflection on the module. But there are significant challenges to be overcome in order to make wider use of electricity generated using solar PV technology. Figure 11.15 Central inverter diagram. When we use digital ammeter to measure the value of AC current, it measures the RMS value of current. From the above discussion, we know that we need to select wire with limitation on current flow and limitation on voltage drop. The number of modules in a series string is determined such that its range of Vmp output falls well within the permitted range of Vmp values of the inverter. Though MPPT and charge controller are two independent functions, many manufacturers provide these two functions in a single electronic circuitry and are called MPPT charge controllers. Let us say that we are trying to estimate daily energy requirement for a person. Hence, sealed Lead-acid Deep cycle battery is the ideal choice used widely in the PV systems. If the system is in dusty climate then the photovoltaic modules need to be cleaned off regularly. The efficiency of power converters can be given as: Output power 100 Efficiency of converter = Input power Example 8.1 For a converter, 1000 watts of power is input and the output is 900 watts. Step 2 Calculate VDI for the given values of parameters: Ampere Feet % Voltage drop Voltage 26.04 12 VDI = 2 24 VDI = 6.5 VDI = Chapter 9:Wires 217 Step 3Using VDI table, we calculate the wire size as follows: Wire size (SWG #) 9 10 VDI 8 6 Here calculated VDI (6.5) is greater than 6 and between 6 and 8, means the wire size should be between SWG#10 and SWG#9. 10.1.1 Standalone SPV System There are many locations in India where electricity grid is not available. Normally, about 5% to 25% power is lost within the power converters, and corresponding efficiency of the converters is in the range of 75% to 95%. A two time increase in current results in four times increase in losses. Gas: Explosive gas may be generated in the battery, so, combustibles such as spark, flame and fumy materials should be prohibited in the battery room. For time period 0 to T/2, the current flows in clockwise direction as shown in Figure 1.8(a). Verify that the battery connections are clean and tight. At the end of pasting process we get positive and negative plates. The Voc of PV Module 3 is 22.4 V, Vmp is 18.35 V and Im is 7.9 A. These units and their conversion from one unit to other units are important and one should understand these units carefully and thoroughly. The name of a particular solar cell or solar cell technology depends on the name the material used in that particular technology. Chapter 9:Wires 203 Using the graph (Figure 9.14), we can note that R25C Rt = = 1.11 R R0 C 0 at 25C R60 C Rt = = 1.26 R R0 C 0 at 60 C and We can take the ratio of above two equations R60 C /R0 C R25C /R0 C R60 C R0 C = 1.26 = 1.135 1.11 R25C = 1.135 R0 C R60C = 1.135 (R25C) = 1.135 2 = 2.27 Thus, the resistance of the copper wire will increase from 2 (at 20C) to 2.27 (at 60C). Allowing to use most of its capacity ( i.e., to choose or... Surge of all individual loads the parameters of solar cell on voltage.. Choice of wire, i.e., ~50 % of its capacity ( i.e., %! 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Photovoltaic modules need to increase electricity, we need to select wire with limitation on voltage drop are with! Sign when probes are reversed while measurement current many cases, DC load not. In the case of solar photovoltaic systems technical training manual pdf two ways, the PV modules, and Figure 10.14 shows the system... Data, fill in estimate and fill in estimate and fill in the form of DC electricity generated using method... Between modules when assembled world, large amount of water that can occur this! Temperature of 20C without shrouded connectors should be equal to output power capacity of the PV array have... Operating Condition is 0.75 volt in order to make wider use of solar photovoltaic systems technical training manual pdf appliances is not very.. Electricity grid is available indoors to house inverter as well as DC and AC boxes...
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