Question about TEMPERATURE MODEL PARAMETERS

[Robson Passos]

I was checking the parameters of the temperature model, and I verified that there are these options:

pvlib.temperature.TEMPERATURE_MODEL_PARAMETERS['sapm']

{'open_rack_glass_glass': {'a': -3.47, 'b': -0.0594, 'deltaT': 3}, 

 'close_mount_glass_glass': {'a': -2.98, 'b': -0.0471, 'deltaT': 1}, 

 'open_rack_glass_polymer': {'a': -3.56, 'b': -0.075, 'deltaT': 3},   'insulated_back_glass_polymer': {'a': -2.81, 'b': -0.0455, 'deltaT': 0}}

The most suitable parameters for installing the system on residential roofs would be "close_mount_glass_glass"? I couldn't find a more detailed description of it.

Thank you very much in advance,
Robson

[Anton Driesse]

Unfortunately, I think you've hit upon a weak spot in the modelling chain.  🙁

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[Mark Mikofski]

There are more options in the the original Sandia array performance model documentation: https://www.osti.gov/servlets/purl/919131

Another option is to use the pvsyst cell temperature model (https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.temperature.pvsyst_cell.html#pvlib.temperature.pvsyst_cell) with recommended coefficients of 15.0 and 0
(https://www.pvsyst.com/help/index.html?temperbehaviour.htm) although there have been different recommendations, see Ben Bourne's talk at 2019 PVPMC meeting in Albuquerque, NM. See section 2 on PV Module Charcterization (https://pvpmc.sandia.gov/resources-and-events/events/2019-12th-pv-performance-modeling-and-monitoring-workshop/): 
Deriving Thermal Response Coefficients for PVSyst (677 downloads)

[cwh...@sandia.gov]

To elaborate a bit: the "insulated back" coefficients were determined for a module with a sheet of insulating foam taped onto the back. The intent was to eliminate any temperature difference between the rear-mounted temperature sensor and the cells. I don't think those coefficients are relevant for a close-mounted rooftop module, unless the mounting effectively eliminates any convective heat transfer behind the module.

Cheers,

Cliff