Solar PV Theory.pdf

# When the e i curve of a pv module seriesconnected pv

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When the E-I curve of a PV module (series–connected PV cells) is used to calculate the value of resistors R P and R S , the calculated values correspond to the total parallel resistance and total series resistance of the PV module. The total parallel resistance and total series resistance are distributed over the cells in the PV module. The total parallel resistance is simply divided by the number of cells in the PV module to obtain the mean value of the parallel resistance R P of each cell. Similarly, the total series resistance is simply divided by the number of cells in the PV module to obtain the mean value of the series resistance R S of each cell. Figure 33 of this discussion shows the calculations of the values of resistors R P and R S made with the E-I curve of a 36-cell PV module implemented with the Lab-Volt Monocrystalline Silicon Solar Panel. Figure 37 shows a 36-cell PV module at night represented using the actual equivalent diagram of the PV cell (see Figure 47). This representation reveals that at night time current flows in the PV module through the series combination of R P and R S in each PV cell, thereby discharging the battery. The value of the discharge current I DISCH. can be calculated using the battery open-circuit voltage E OC and the total parallel resistance R P and total series resistance R S of the PV module ( I DISCH. = E OC / ( R P + R S ). Note that the discharge current is usually small with respect to the battery capacity. Evaluation of resistor R P Evaluation of resistor R S Voltage (V) Voltage (V) 0 E 0.6 E OC E OC 0.6 Current (A) I SC I Δ I @ voltage E ݈ܵ݋݌݁ ൌ ߂ܫ ܧ 1 ܴ Current (A) I SC I Δ E @ current I ݈ܵ݋݌݁ ൌ ߂ܧ ܫ ൌ ܴ

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Storing Energy from Solar Panels into Batteries Discussion Solar Power 2 7 Figure 37 . At night, current flows in the PV module through R P and R S in each PV cell, thereby slowly discharging the battery. Blocking diode Although the battery discharge current at night is usually low, it is common practice to add a diode (blocking diode) in series with the PV module to avoid battery discharge at night (see Figure 38 ). When the PV module is illuminated, the diode is forward biased and charge current flows into the battery. At night, the PV module stops producing current and the battery voltage applies a reverse bias to the diode. The blocking diode prevents current flow thereby avoiding the battery discharge. PV module at night R S R P 36 PV cells Battery discharge current I DISCH. 12 V lead- acid battery
Storing Energy from Solar Panels into Batteries Procedure Outline 2 8 Solar Power During day Figure 38 . A diode is added in series to avoid battery discharge at night. PV module (36 cells) At night PV module (36 cells) Diode is forward biased Diode is reverse biased 12 V lead- acid battery 12 V lead- acic battery I = 0 I
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• One '14
• Photovoltaics, Solar cell, PV cell, Photovoltaic module, pv module

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