Sustainable Building Operation Using Simulation - Low Energy Cooling for Sustainable Buildings - page 244

Table 6.8 Two-diode parameters extracted from measured I - V curves

Parameter Simulated values

Photocurrent coefficient c 0 /V − 1 0.1613

Temperature coefficient photocurrent c T /V − 1 K − 1 0.000 411 51

Shockley diode current parameter c s /Am − 2 17 139

Recombination diode current parameter c r /Am − 2 1.713

Series resistance r s / m 2 0.000 371 3

Shunt resistance r p / m 2 0.048 05

The two-diode equation was then used to calculate standard test conditions (STC)
for the module and the results were compared with the data sheet information from the
manufacturers. The reduction of MPP power from the 90.7W manufacturers' infor-
mation to 77.2W from the online simulation correspond to the 15% power reduction
mentioned above (see Table 6.9).
Using these STC values calculated by the two-diode model as the new data sheet
information, the one-diode model parameters were again extracted (see Table 6.10).
They are much more consistent than the original data, where the shunt resistance was
negative and the photocurrent temperature coefficient was far too small.
The two-diode curve fitted to three measured I - V curves is shown in Figure 6.43.
The two-diode curve under STC conditions and the derived one-diode curve at STC
show very similar behaviour.

Table 6.9 STC conditions calculated with two-diode model versus manufacturers data
Parameter

Manufacturers' data Simulated values

Open-circuit voltage / V 43.0 42.36

Short-circuit current / A 2.8 2.89

MPP voltage / V 33.6 30.41

MPP current / A 2.7 2.54

MPP power / W 90.7 77.2

Temperature coefficient voltage / VK − 1

− 0.156 − 0.151

Temperature coefficient current/AK − 1 0.000 93 0.004 04

Table 6.10 One-diode parameters based on the original manufacturers' data and on the simulated STC
curve
Parameter Values from Simulated

and coefficients manufacturers' data values

Photocurrent coefficient c 0 /V − 1 0.2240 0.1557

Temp. coeff. photocurrent c T /V − 1 K − 1 7 . 44 × 10 − 6

0.000 394

Shockley diode current c s /Am − 2 14 066 16 689

Diode factor α 1.04 1.0232

Series resistance r s / m 2 0.000 24 59 0.000 361 9

Shunt resistance r p / m 2

− 0.1134 0.048 87