Array losses

[inyss]

   Hello pvsyst community !

Thank you for giving me explication about thermal behavior , what is said by pvsyst help :    

Quote

 

Thermal behavior of the PV array. The standard test conditions are specified for a cell temperature of 25°C, but the modules are usually working at much higher temperatures. The thermal loss is calculated following the one-diode model. For crystalline silicon cells, the loss is about  -0.4 %/°C at MPP. For fixed voltage operating conditions, the temperature mainly affects the I/V curve voltage, and effective losses are strongly dependent on the array overvoltage with respect to the operating voltage.

 The parameters available to the user (thermal loss factor) involve the cell temperature determination with respect to given external conditions.

 

what I don't have understood is how thermall loss factor has an effect on loss due to temperature calculation  ! 

 

[André Mermoud]

During the simulation, there are two steps:

- Define the array (cell) temperature during the simulation, according to the external conditions (Ambient temperature and Irradiance, possibly wind velocity)

- Use this temperature as input for the one-diode model.

For the temperature of the array, there is a model described in the help  "Project design > Array and system losses > Array Thermal losses". This is based on a parameter U (heat loss coefficient) or Uc ans Uv when wind velocity is involved.

For the one diode model, increasing the cell temperature will diminish the voltage and the power (about -0.35%/°C for crystalline modules).