CALCPARAMS_PVSYST

This function converts PVsyst reference module parameters into the operating-condition coefficients required by the single-diode equation. It accounts for irradiance, cell temperature, the PVsyst diode-factor model, and the irradiance dependence of shunt resistance.

The thermal-voltage term returned by the model is based on the diode factor, cells in series, and cell temperature:

nN_sV_{th} = \gamma N_s \frac{k_B T_c}{q}

The five outputs are returned in the order photocurrent, saturation current, series resistance, shunt resistance, and nN_sV_{th}. These values are typically used as inputs to singlediode, max_power_point, or related IV-curve calculations.

Excel Usage

=CALCPARAMS_PVSYST(effective_irradiance, temp_cell, alpha_sc, gamma_ref, mu_gamma, I_L_ref, I_o_ref, R_sh_ref, R_sh_zero, R_s, cells_in_series, R_sh_exp, eg_ref, irrad_ref, temp_ref)

• effective_irradiance (float, required): Irradiance converted to photocurrent (W/m^2).
• temp_cell (float, required): Average cell temperature (C).
• alpha_sc (float, required): Short-circuit current temp coefficient (A/C).
• gamma_ref (float, required): Diode ideality factor (unitless).
• mu_gamma (float, required): Temp coefficient for ideality factor (1/K).
• I_L_ref (float, required): Light-generated current at reference (A).
• I_o_ref (float, required): Diode saturation current at reference (A).
• R_sh_ref (float, required): Shunt resistance at reference (ohms).
• R_sh_zero (float, required): Shunt resistance at zero irradiance (ohms).
• R_s (float, required): Series resistance at reference (ohms).
• cells_in_series (int, required): Number of cells in series.
• R_sh_exp (float, optional, default: 5.5): Exponent for shunt resistance.
• eg_ref (float, optional, default: 1.121): Energy bandgap at reference temperature (eV).
• irrad_ref (float, optional, default: 1000): Reference irradiance (W/m^2).
• temp_ref (float, optional, default: 25): Reference cell temperature (C).

Returns (list[list]): 2D list containing [[photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth]], or an error string.

Example 1: PVsyst parameter calculation at standard conditions

Inputs:

effective_irradiance	temp_cell	alpha_sc	gamma_ref	mu_gamma	I_L_ref	I_o_ref	R_sh_ref	R_sh_zero	R_s	cells_in_series	R_sh_exp	eg_ref	irrad_ref	temp_ref
1000	25	0.005	1.1	0.001	6	1e-9	400	1000	0.3	60	5.5	1.121	1000	25

Excel formula:

=CALCPARAMS_PVSYST(1000, 25, 0.005, 1.1, 0.001, 6, 1e-9, 400, 1000, 0.3, 60, 5.5, 1.121, 1000, 25)

Expected output:

Result
6	1e-9	0.3	400	1.69571

Example 2: Default optional PVsyst constants

Inputs:

effective_irradiance	temp_cell	alpha_sc	gamma_ref	mu_gamma	I_L_ref	I_o_ref	R_sh_ref	R_sh_zero	R_s	cells_in_series
1000	25	0.005	1.1	0.001	6	1e-9	400	1000	0.3	60

Excel formula:

=CALCPARAMS_PVSYST(1000, 25, 0.005, 1.1, 0.001, 6, 1e-9, 400, 1000, 0.3, 60)

Expected output:

Result
6	1e-9	0.3	400	1.69571

Example 3: Warm cell with reduced irradiance

Inputs:

effective_irradiance	temp_cell	alpha_sc	gamma_ref	mu_gamma	I_L_ref	I_o_ref	R_sh_ref	R_sh_zero	R_s	cells_in_series	R_sh_exp	eg_ref	irrad_ref	temp_ref
750	45	0.005	1.1	0.001	6	1e-9	400	1000	0.3	60	5.5	1.121	1000	25

Excel formula:

=CALCPARAMS_PVSYST(750, 45, 0.005, 1.1, 0.001, 6, 1e-9, 400, 1000, 0.3, 60, 5.5, 1.121, 1000, 25)

Expected output:

Result
4.575	1.40654e-8	0.3	407.276	1.84236

Example 4: Cool cell at elevated irradiance

Inputs:

effective_irradiance	temp_cell	alpha_sc	gamma_ref	mu_gamma	I_L_ref	I_o_ref	R_sh_ref	R_sh_zero	R_s	cells_in_series	R_sh_exp	eg_ref	irrad_ref	temp_ref
1100	15	0.005	1.1	0.001	6	1e-9	400	1000	0.3	60	5.5	1.121	1000	25

Excel formula:

=CALCPARAMS_PVSYST(1100, 15, 0.005, 1.1, 0.001, 6, 1e-9, 400, 1000, 0.3, 60, 5.5, 1.121, 1000, 25)

Expected output:

Result
6.545	2.25033e-10	0.3	398.958	1.62394

Python Code

Show Code

from pvlib.pvsystem import calcparams_pvsyst as result_func

def calcparams_pvsyst(effective_irradiance, temp_cell, alpha_sc, gamma_ref, mu_gamma, I_L_ref, I_o_ref, R_sh_ref, R_sh_zero, R_s, cells_in_series, R_sh_exp=5.5, eg_ref=1.121, irrad_ref=1000, temp_ref=25):
    """
    Calculate five single-diode parameter values using the PVsyst v6 model.

    See: https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.pvsystem.calcparams_pvsyst.html

    This example function is provided as-is without any representation of accuracy.

    Args:
        effective_irradiance (float): Irradiance converted to photocurrent (W/m^2).
        temp_cell (float): Average cell temperature (C).
        alpha_sc (float): Short-circuit current temp coefficient (A/C).
        gamma_ref (float): Diode ideality factor (unitless).
        mu_gamma (float): Temp coefficient for ideality factor (1/K).
        I_L_ref (float): Light-generated current at reference (A).
        I_o_ref (float): Diode saturation current at reference (A).
        R_sh_ref (float): Shunt resistance at reference (ohms).
        R_sh_zero (float): Shunt resistance at zero irradiance (ohms).
        R_s (float): Series resistance at reference (ohms).
        cells_in_series (int): Number of cells in series.
        R_sh_exp (float, optional): Exponent for shunt resistance. Default is 5.5.
        eg_ref (float, optional): Energy bandgap at reference temperature (eV). Default is 1.121.
        irrad_ref (float, optional): Reference irradiance (W/m^2). Default is 1000.
        temp_ref (float, optional): Reference cell temperature (C). Default is 25.

    Returns:
        list[list]: 2D list containing [[photocurrent, saturation_current, resistance_series, resistance_shunt, nNsVth]], or an error string.
    """
    try:
        irrad = float(effective_irradiance)
        tc = float(temp_cell)
        asc = float(alpha_sc)
        gr = float(gamma_ref)
        mg = float(mu_gamma)
        ilr = float(I_L_ref)
        ior = float(I_o_ref)
        rshr = float(R_sh_ref)
        rs_v = float(R_s)
        nc = int(cells_in_series)

        rsh0 = float(R_sh_zero) if R_sh_zero is not None else 1000.0
        rexp = float(R_sh_exp) if R_sh_exp is not None else 5.5
        eg = float(eg_ref) if eg_ref is not None else 1.121
        ir = float(irrad_ref) if irrad_ref is not None else 1000.0
        tr = float(temp_ref) if temp_ref is not None else 25.0

        res = result_func(
            effective_irradiance=irrad,
            temp_cell=tc,
            alpha_sc=asc,
            gamma_ref=gr,
            mu_gamma=mg,
            I_L_ref=ilr,
            I_o_ref=ior,
            R_sh_ref=rshr,
            R_sh_0=rsh0,
            R_s=rs_v,
            cells_in_series=nc,
            R_sh_exp=rexp,
            EgRef=eg,
            irrad_ref=ir,
            temp_ref=tr
        )

        return [[float(v) for v in res]]
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

effective_irradiance *

Irradiance converted to photocurrent (W/m^2).

temp_cell *

Average cell temperature (C).

alpha_sc *

Short-circuit current temp coefficient (A/C).

gamma_ref *

Diode ideality factor (unitless).

mu_gamma *

Temp coefficient for ideality factor (1/K).

I_L_ref *

Light-generated current at reference (A).

I_o_ref *

Diode saturation current at reference (A).

R_sh_ref *

Shunt resistance at reference (ohms).

R_sh_zero *

Shunt resistance at zero irradiance (ohms).

R_s *

Series resistance at reference (ohms).

cells_in_series *

Number of cells in series.

R_sh_exp

Exponent for shunt resistance.

eg_ref

Energy bandgap at reference temperature (eV).

irrad_ref

Reference irradiance (W/m^2).

temp_ref

Reference cell temperature (C).