pvlib.ivtools.sdm.fit_cec_sam(celltype, v_mp, i_mp, v_oc, i_sc, alpha_sc, beta_voc, gamma_pmp, cells_in_series, temp_ref=25)[source]#

Estimates parameters for the CEC single diode model (SDM) using the SAM SDK.

  • celltype (str) – Value is one of ‘monoSi’, ‘multiSi’, ‘polySi’, ‘cis’, ‘cigs’, ‘cdte’, ‘amorphous’

  • v_mp (float) – Voltage at maximum power point [V]

  • i_mp (float) – Current at maximum power point [A]

  • v_oc (float) – Open circuit voltage [V]

  • i_sc (float) – Short circuit current [A]

  • alpha_sc (float) – Temperature coefficient of short circuit current [A/C]

  • beta_voc (float) – Temperature coefficient of open circuit voltage [V/C]

  • gamma_pmp (float) – Temperature coefficient of power at maximum power point [%/C]

  • cells_in_series (int) – Number of cells in series

  • temp_ref (float, default 25) – Reference temperature condition [C]


  • I_L_ref (float) – The light-generated current (or photocurrent) at reference conditions [A]

  • I_o_ref (float) – The dark or diode reverse saturation current at reference conditions [A]

  • R_s (float) – The series resistance at reference conditions, in ohms.

  • R_sh_ref (float) – The shunt resistance at reference conditions, in ohms.

  • a_ref (float) – The product of the usual diode ideality factor n (unitless), number of cells in series Ns, and cell thermal voltage at reference conditions [V]

  • Adjust (float) – The adjustment to the temperature coefficient for short circuit current, in percent.



The CEC model and estimation method are described in 1. Inputs v_mp, i_mp, v_oc and i_sc are assumed to be from a single IV curve at constant irradiance and cell temperature. Irradiance is not explicitly used by the fitting procedure. The irradiance level at which the input IV curve is determined and the specified cell temperature temp_ref are the reference conditions for the output parameters I_L_ref, I_o_ref, R_s, R_sh_ref, a_ref and Adjust.



A. Dobos, “An Improved Coefficient Calculator for the California Energy Commission 6 Parameter Photovoltaic Module Model”, Journal of Solar Energy Engineering, vol 134, 2012. DOI: 10.1115/1.4005759