# pvlib.pvarray.huld#

Power (DC) using the Huld model.

The Huld model 1 is used by PVGIS and is given by

\begin{align}\begin{aligned}P_{dc} &= G' ( P_{dc0} + k_1 \log(G') + k_2 \log^2 (G') + k_3 T' + k_4 T' \log(G') + k_5 T' \log^2 (G') + k_6 T'^2)\\G' &= \frac{G_{poa eff}}{1000}\\T' &= T_{mod} - 25^{\circ}C\end{aligned}\end{align}
Parameters
• effective_irradiance (numeric) – The irradiance that is converted to photocurrent. [$$W/m^2$$]

• temp_mod (numeric) – Module back-surface temperature. [C]

• pdc0 (numeric) – Power of the modules at reference conditions 1000 $$W/m^2$$ and $$25^{\circ}C$$. [W]

• k (tuple, optional) – Empirical coefficients used in the power model. Length 6. If k is not provided, cell_type must be specified.

• cell_type (str, optional) – If provided, must be one of 'cSi', 'CIS', or 'CdTe'. Used to look up default values for k if k is not specified.

Returns

pdc (numeric) – DC power. [W]

Raises

ValueError – If neither k nor cell_type are specified.

Notes

The equation for $$P_{dc}$$ is from 1. The expression used in PVGIS documentation differs by factoring $$P_{dc0}$$ out of the polynomial:

$P_{dc} = G' P_{dc0} (1 + k'_1 \log(G') + k'_2 \log^2 (G') + k'_3 T' + k'_4 T' \log(G') + k'_5 T' \log^2 (G') + k'_6 T'^2)$

PVGIS documentation shows a table of default parameters $$k'$$ for different cell types. The parameters $$k'$$ differ from the parameters $$k$$ for huld() by the factor pdc0, that is,

$k = P_{dc0} k'$

With default values for $$k$$, at very low irradiance, i.e., $$G' < 20 W/m^2$$, $$P_{dc}$$ may be negative due to the terms involving $$\log(G')$$.

huld() is a component of the PV performance model implemented in PVGIS. Among other components, the full PVGIS model includes:

The PVGIS API (see pvlib.iotools.get_pvgis_hourly()) returns broadband plane-of-array irradiance (poa_global) and DC power (P). poa_global is irradiance before applying the IAM and spectral adjustments. In contrast the effective_irradiance for huld() should have the IAM and spectral adjustments. Users comparing output of huld() to PVGIS’ P values should expect differences unless effective_irradiance is computed in the same way as done by PVGIS.

References

1(1,2)

T. Huld, G. Friesen, A. Skoczek, R. Kenny, T. Sample, M. Field, E. Dunlop. A power-rating model for crystalline silicon PV modules. Solar Energy Materials and Solar Cells 95, (2011), pp. 3359-3369. DOI: 10.1016/j.solmat.2011.07.026.