CEC six-parameter, this module

Method

The circuit and its temperature laws are those of the representative-module option (1 to 4): the one-diode model of De Soto, Klein and Beckman with Dobos's adjustment of the short-circuit temperature coefficient, the model of the California Energy Commission's module database. Here the parameters are this module's own: a_ref, I_L,ref, I_0,ref, R_s, R_sh,ref, Adjust and α_sc of its CEC database entry. They are used as the database gives them, not scaled to the nameplate, so the power at standard conditions is the circuit's own maximum, which can differ from the datasheet by a few tenths of a percent; the nameplate still sets the array's nominal energy. No power below 1 W/m². Where the parameters come from: the module record's CEC block, which every module of the CEC library carries. A module without it, such as one read from a PAN file, cannot use this option: the fit of the six parameters from datasheet values (Dobos 2012) is not built.

The math

1. Light current
2. Saturation current
3. Ideality and shunt resistance
4. Circuit

$$I_L = \frac{G}{1000}\left[I_{L,ref} + \alpha_{sc}\left(1 - \frac{\text{Adj}}{100}\right)(T - T_{ref})\right] \tag{1}$$ $$I_0 = I_{0,ref}\left(\frac{T}{T_{ref}}\right)^3 \exp\!\left[\frac{1}{k_B}\left(\frac{1.12}{T_{ref}} - \frac{E_g}{T}\right)\right],\qquad E_g = 1.12\,\big(1 - 0.0002677\,(T - T_{ref})\big) \tag{2}$$ $$a_T = a_{ref}\,\frac{T}{T_{ref}},\qquad R_{sh} = R_{sh,ref}\,\frac{1000}{G} \tag{3}$$ $$I_m = I_L - I_0\left[\exp\!\left(\frac{V_m + I_m R_s}{a_T}\right) - 1\right] - \frac{V_m + I_m R_s}{R_{sh}} \tag{4}$$

where

Symbol	Meaning	Unit
$I_L$	the light current	A
$G$	the effective irradiance	W/m²
$I_{L,ref}$	the light current at reference conditions	A
$\alpha_{sc}$	the temperature coefficient of the short-circuit current	A/°C
$\text{Adj}$	the adjustment of that coefficient	%
$T$	the cell temperature	K
$T_{ref}$	the reference temperature	K
$I_0$	the diode saturation current	A
$I_{0,ref}$	the saturation current at reference conditions	A
$k_B$	Boltzmann's constant	eV/K
$E_g$	the bandgap: 1.12 eV at 25 °C, the silicon value, used for both representative modules	eV
$a_T$	the modified ideality factor	V
$a_{ref}$	the modified ideality factor at reference conditions	V
$R_{sh}$	the shunt resistance	Ω
$R_{sh,ref}$	the shunt resistance at reference conditions	Ω
$I_m$	the module current	A
$V_m$	the module voltage	V
$R_s$	the series resistance	Ω

References

1. De Soto, Klein & Beckman 2006, Improvement and validation of a model for photovoltaic array performance, Solar Energy 80(1) 78–88
2. Dobos 2012, An improved coefficient calculator for the California Energy Commission 6 parameter photovoltaic module model, Journal of Solar Energy Engineering 134(2) 021011
3. Gilman, DiOrio, Freeman, Janzou, Dobos & Ryberg 2018, SAM Photovoltaic Model Technical Reference Update, NREL/TP-6A20-67399
4. NREL SAM Simulation Core (SSC) source code, release 2026.7.3, github.com/NatLabRockies/ssc: shared/lib_cec6par.cpp, cec6par_module_t; ssc/cmod_pvwattsv8.cpp, the module parameters of each module type

API

options.module_model = cec (module.model = cec), module.cec

Symbols follow the symbol registry.