pvlib.temperature.ross

pvlib.temperature.ross(poa_global, temp_air, noct=None, k=None)

Calculate cell temperature using the Ross model.

The Ross model [1] assumes the difference between cell temperature and ambient temperature is proportional to the plane of array irradiance, and assumes wind speed of 1 m/s. The model implicitly assumes steady or slowly changing irradiance conditions.

Parameters:

• poa_global (numeric) – Total incident irradiance. [W/m⁻²]

• temp_air (numeric) – Ambient dry bulb temperature. [C]

• noct (numeric, optional) – Nominal operating cell temperature [C], determined at conditions of 800 W/m⁻² irradiance, 20 C ambient air temperature and 1 m/s wind. If noct is not provided, k is required.

• k (numeric, optional) – Ross coefficient [Km²W⁻¹], which is an alternative to employing NOCT in Ross’s equation. If k is not provided, noct is required.

Returns:

cell_temperature (numeric) – Cell temperature. [C]

Notes

The Ross model for cell temperature \(T_{C}\) is given in [1] as

\[T_{C} = T_{a} + \frac{NOCT - 20}{80} S = T_{a} + k × S\]

where \(S\) is the plane of array irradiance in mWcm⁻². This function expects irradiance in Wm⁻².

Representative values for k are provided in [2], covering different types of mounting and degrees of back ventialtion. The naming designations, however, are adapted from [3] to enhance clarity and usability.

Mounting	\(k\)
Sloped roof, well ventilated	0.02
Free-standing system	0.0208
Flat roof, well ventilated	0.026
Sloped roof, poorly ventilated	0.0342
Facade integrated, semi-ventilated	0.0455
Facade integrated, poorly ventilated	0.0538
Sloped roof, non-ventilated	0.0563

It is also worth noting that the semi-ventilated facade case refers to partly transparent compound glass insulation modules, while the non- ventilated case corresponds to opaque, insulated PV-cladding elements. However, the emphasis in [3] appears to be on ventilation conditions rather than module construction.

References

[1] (1,2)

Ross, R. G. Jr., (1981). “Design Techniques for Flat-Plate Photovoltaic Arrays”. 15th IEEE Photovoltaic Specialist Conference, Orlando, FL.

[2]

E. Skoplaki and J. A. Palyvos, “Operating temperature of photovoltaic modules: A survey of pertinent correlations,” Renewable Energy, vol. 34, no. 1, pp. 23–29, Jan. 2009, DOI: 10.1016/j.renene.2008.04.009

[3] (1,2)

T. Nordmann and L. Clavadetscher, “Understanding temperature effects on PV system performance,” Proceedings of 3rd World Conference on Photovoltaic Energy Conversion, May 2003.