Module Temperature

Sandia Module Temperature

This routine empirically computes the module temperature from the air temperature, the wind speed, and the in-plane irradiation. This model uses two empirically-determined coefficients: a_t establishes the upper limit for module temperature at low wind speeds and high solar irradiance, b_t establishes the rate at which module temperature drops as wind speed increases.

Figure 34. Empirical Module Temperature Coefficients

Inputs

Outputs

1.) Compute the module temperature as a function of the available insolation, wind speed, and air temperature:

Reference

King, D. L., Kratochvil, J.A., Boyson, W.L., Photovoltaic Array Performance Model, Report SAND2004-3535, Sandia National Laboratories, Albuquerque, NM, September 1997.

Heat Balance Temperature Model

The thermal behavior of the field, which strongly influences the electrical performances, is determined by a thermal balance between the ambient temperature and the cell’s temperature, which is elevated by incident irradiation. In this simple model, α_T is the absorption coefficient of solar irradiation, and η_m is the PV efficiency (related to the Module area), i.e. the removed energy from the module.

Inputs

Outputs

Algorithm

1.) Compute the module temperature as a function of the available insolation, wind speed, and air temperature:

The usual value of the absorption coefficient α is 0.9. The PV efficiency is taken from the Module File.

The thermal behavior is characterized by a thermal loss factor designated here by k, which can be split into a constant component k_c and a factor proportional to the wind velocity k_v. These factors depend on the mounting mode of the modules (sheds, roofing, facade, etc.).

2.) Convert the cell temperature to a module surface temperature.

Reference

Mermoud, A., Conception et dimensionnement de systèmes photovoltaïques : Introduction des modules PV en couches minces dans le Logiciel PVsyst. Université de Genève, 2005.