Thermal Parameter Calculation using Meteo Data (Ambient Temperature)

[Hossam]

The meteonorm 8.1 database has hourly values of ambient temperature. 
Does PVsyst calculate the Cell temperature using the ambient temperature value at the specific time during the simulation or it uses the monthly average for all days?
I mean does it calculate the cell temperature only during daylight or it merges all heat transfer throughout the year, day and night.

[Michele Oliosi]

Dear Hossam, the cell temperature is calculated with the ambient temperature at each specific hour.

[Hossam]

Does it include the ambient temperatures at night in the simulation of thermal losses?

[Michele Oliosi]

By thermal losses we only account the losses due to the loss of efficiency when the module heats up during the day.
Unless you are concerned with infinitesimal variations of temperature, since the thermal inertia of modules is about 10 minutes, you don't need to merge the heat transfer throughout the year, day and night to simulate in hourly steps. Considering the heat transfer within the hour is enough.

[Hossam]

This means the losses are only calculated using the hourly temperature values only in the presence of irradiance or throught the day (24 hours)?

[Michele Oliosi]

Only in the presence of irradiance. By definition there will be no thermal losses at night.

[Hossam]

This means PVsyst recognizes the time where there is no irradiance and then does not calculate the thermal losses unless the irradiance presence is provided in the hourly values table. Is this right?

Secondly, How can I export the meteonorm 8.1 data used in my simulation as I need to edit only the ambient temperature.

Thank you

[Hossam]

On 4/4/2023 at 11:59 AM, Hossam said:

This means PVsyst recognizes the time where there is no irradiance and then does not calculate the thermal losses unless the irradiance presence is provided in the hourly values table. Is this right?

Secondly, How can I export the meteonorm 8.1 data used in my simulation as I need to edit only the ambient temperature.

Thank you

@Michele Oliosi

[dtarin]

Export the 8760 and create a custom weather file then reimport.

[Hossam]

Can you explain what is the 8760 ?
Please attach media. 
Thank you so much.

[Michele Oliosi]

it's the colloquial name for a hourly output file (8760 hours in a year)
see https://www.pvsyst.com/help/output_file.htm

[Hossam]

On 4/4/2023 at 11:59 AM, Hossam said:

This means PVsyst recognizes the time where there is no irradiance and then does not calculate the thermal losses unless the irradiance presence is provided in the hourly values table. Is this right?

Secondly, How can I export the meteonorm 8.1 data used in my simulation as I need to edit only the ambient temperature.

Thank you

@Michele Oliosi Please tell me the answer of the first question. 
Thanks in avance.

[Hossam]

On 4/6/2023 at 11:22 AM, Michele Oliosi said:

it's the colloquial name for a hourly output file (8760 hours in a year)
see https://www.pvsyst.com/help/output_file.htm

If I export the excel file using only the meteo data then If I import it again, it will be recognized as a new meteo file in PVsyst?
Thanks in advance

[Michele Oliosi]

On 4/4/2023 at 11:59 AM, Hossam said:

This means PVsyst recognizes the time where there is no irradiance and then does not calculate the thermal losses unless the irradiance presence is provided in the hourly values table. Is this right?

Indeed that is correct.