Module Temperature

Two models for estimating module temperature are supported by PlantPredict and selectable by the user in the Simulation Settings: the Sandia method and the static heat-balance model.

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: at establishes the upper limit for module temperature at low wind speeds and high solar irradiance, bt establishes the rate at which module temperature drops as wind speed increases.

Soiling Figure 14

Figure 34. Empirical Module Temperature Coefficients




Sandia Module Temperature Inputs


Sandia Module Temperature Outputs


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

Sandia Module Temperature Algo86
2.) Compute the cell temperature. This temperature difference is typically 2 to 3 °C for flat-plate modules in an open-rack mount at a reference irradiance GRef of 1000 W/m2.

Sandia Module Temperature Algo87


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, αT is the absorption coefficient of solar irradiation, and ηm is the PV efficiency (related to the Module area), i.e. the removed energy from the module.



Heat Balance Temperature Outputs


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

Heat Balance Temperature Algo88

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 kc and a factor proportional to the wind velocity kv. These factors depend on the mounting mode of the modules (sheds, roofing, facade, etc.).


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

Heat Balance Temperature Algo89


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