Ta.day = the daytime average ambient temperature for the month that the sizing is being undertaken. Since the modules are used for battery charging, the current at the charging voltage at the effective cell temperature should be used in calculations. For a 12V battery, a charging voltage of 14V is appropriate. If curves are unavailable to determine the current at effective cell temperature, the Normal Operating Cell temperature (NOCT) provided by the manufacturers can be used. Therefore the derated module output current is calculated as follows: The Current of the module at 14V and effective cell temperature (or NOCT current) multiplied by derating due to manufacturer’s tolerance multiplied by derating due to dirt I (NOCT) x fman x fdirt If a module has a 3% (0.03) manufacturer’s tolerance, the module’s current is derated by multiplying by 0.97 (1-0.03). If a module has a 5% (0.05) loss due to dirt, the module’s current is derated by multiplying by 0.95 (1-0.05). 4. Number of Modules required in the Array Determine the number of modules in series: to do this, divide the system voltage by the nominal operating voltage of each module. To determine the number of strings in parallel, the PV array output current required (in A) is divided by the output of each module (in A). Then round up to the next whole number. To determine the number of strings in parallel, the PV array output current required (in A) is divided by the output of each module (in A). Then round up to the next whole number. 5 CONTROLLERS: Standard Switched Controller PV controllers on the market range from simple switched units that only prevent the overcharge (and discharge) of connected batteries to microprocessor based units that incorporate many additional features such as: PWM and equalisation charge modes DC Load control Voltage and current metering Amp-hour logging Generator start/stop control Unless the controller is a model that is current limited, these should be sized so that they are capable of carrying 125% of the array’s short circuit current and withstanding the
Ta.day = the daytime average ambient temperature for the month that the sizing is being undertaken. Since the modules are used for battery charging, the current at the charging voltage at the effective cell temperature should be used in calculations. For a 12V battery, a charging voltage of 14V is appropriate. If curves are unavailable to determine the current at effective cell temperature, the Normal Operating Cell temperature (NOCT) provided by the manufacturers can be used. Therefore the derated module output current is calculated as follows: The Current of the module at 14V and effective cell temperature (or NOCT current) multiplied by derating due to manufacturer’s tolerance multiplied by derating due to dirt I (NOCT) x fman x fdirt If a module has a 3% (0.03) manufacturer’s tolerance, the module’s current is derated by multiplying by 0.97 (1-0.03). If a module has a 5% (0.05) loss due to dirt, the module’s current is derated by multiplying by 0.95 (1-0.05). 4. Number of Modules required in the Array Determine the number of modules in series: to do this, divide the system voltage by the nominal operating voltage of each module. To determine the number of strings in parallel, the PV array output current required (in A) is divided by the output of each module (in A). Then round up to the next whole number. To determine the number of strings in parallel, the PV array output current required (in A) is divided by the output of each module (in A). Then round up to the next whole number. 5 CONTROLLERS: Standard Switched Controller PV controllers on the market range from simple switched units that only prevent the overcharge (and discharge) of connected batteries to microprocessor based units that incorporate many additional features such as: PWM and equalisation charge modes DC Load control Voltage and current metering Amp-hour logging Generator start/stop control Unless the controller is a model that is current limited, these should be sized so that they are capable of carrying 125% of the array’s short circuit current and withstanding the