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
Summary of Losses in Hybrid PV System ( Valid for a.c bus and d.c. bus ) Table 2 Summary of Losses in a.c Hybrid System Case 1: PV charges battery with standard controller & battery supplies AC loads Case 2: PV charges battery via MPPT controller & battery supplies AC loads Case 3: PV is connected to Grid connect Inverter and charges batteries via interactive & batteries supply load Case 4: Generator charges battery & battery supplies AC loads- Current from inverter is specified Case 5: Generator supplies AC loads directly Case 6: PV connected to grid connect inverter and supplies AC loads directly 1) Battery columbic efficiency losses when charging (typ~10%) 1) Cable losses between the PV array to MPPT (typ <1%) 1) Cables losses between the PV array to grid connect inverter (typ <1%) 1) Battery columbic efficiency losses when charging (typ~10%) Wh of the loads is supplied directly by generator 1) Cables losses between the PV array to grid connect inverter (typ <1%) 2) AC interactive inverter efficiency losses (typ~7-12%) 2) MPPT efficiency losses (typ~4-5%) 2) Grid connect inverter efficiency losses (typ~4-5%) 2) AC interactive inverter efficiency losses 2) Grid connect inverter efficiency losses 3) Cable losses between MPPT and battery (typ <1%) 3) Cable losses between grid connect inverter and interactive inverter and battery (typ <1%)
4) Battery efficiency losses when discharging (typ~20%) 4) AC interactive inverter efficiency losses (typ~7-12%) acting as charger 5) Cable losses between battery and AC interactive inverter (typ <1%) 5) Cable losses between AC interactive inverter and battery (typ <1%) 6) AC interactive inverter efficiency losses 6) Battery efficiency losses (typ~20%) 7) Cable losses between battery and AC interactive inverter (typ <1%) 8) AC interactive inverter efficiency losses (typ~7-12%) hour
Annex 4: Tilt and Orientation diagram for 1°N. NW (315) 320 325 330 335 340 345 350 355 N (0) 5 10 15 20 25 30 35 40 NE (45) %LOSS 90 5% 310 80 50 10% 305 70 55 15% 300 60 60 20% 295 50 65 25% 290 40 70 30% 285 30 75 35% 280 20 80 40% 275 10 85 45% W (270) 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 90 E (90) 50% 265 10 95 55% 260 20 100 60% 255 30 105 250 40 110 245 50 115 240 60 120 235 70 125 230 80 130 90 SW (225) 220 215 210 205 200 195 190 185 S (180) 175 170 165 160 155 150 145 140 SE (135)
The Peak Sun hrs (PSH) for the site is displayed in following table: PSH for site with optimal array tilt Month (kWh/m²) Jan 5.07 Feb 5.49 Mar 5.28 Apr 5.15 May 5.15 June 5.10 July 4.99 Aug 4.81 Sep 4.66 Oct 4.78 Nov 4.53 Dec 4.41 Avg 4.95 The selected module for the system will have the following specifications (Used for AC Bus system): Rated Power (Pmax)¹ 175W Warranted minimum power 170W Voltage at Pmax (Vmp) 35.4V Current at Pmax (Imp) 4.9A Short circuit current (Isc) 5.5A Open circuit voltage (Voc) 44.5V Temperature coefficient of Isc (0.065±0.015)%/ºC Temperature coefficient of Voc (160±20)mV/ºC Temperature coefficient of Pmax (0.5±0.05)%/ºC NOCT² 47±2ºC Maximum series fuse rating 15A Maximum system voltage 600V