Given the 1-diode model parameters defined for the module under STC conditions (25 °C, 1000 W/m²), compute the temperature and irradiance-corrected parameters at the actual module temperature T_m and the available solar energy G_T,Eff. The default temperature correction of all 1-diode parameters is linear. If a non-linear temperature correction of the diode ideality factor is desired, the then a set of additional parameters (polynomial coefficients) is available to affect this correction.

This non-linear response is illustrated in Figure 36 for a family of I(V) curves with a module temperature range of 8 °C to 75 °C. This data was measured in the laboratory using the module temperature control system and a Spire long-pulse solar simulator.

Figure 36. Non-Linear Module Power Temperature Response using a Third-Order Polynomial Correction to the Diode Ideality Factor γ

 

 

Inputs

Outputs

Algorithm

1.) Given the effective available insolation G_T,Eff and module temperature T_m, find the corrected 1-diode shunt and series resistance.

 

2.) If the linear correction to the diode ideality factor is desired, or all non-linear coefficients a_y,b_y,c_y,d_y = 0, then correct it for the module temperature as follows:

3.) If the non-linear correction to the diode ideality factor is desired, then correct it for the module temperature as follows:

4.) Correct the saturation current for temperature. Note that this correction includes the previously temperature-corrected diode ideality factor.

*  In the above equation aγ is referring to the y1 non-linear temperature coefficient in PlantPredict and bγ is referring to y2, cγ is referring to y3 and dγ is referring to y45.) Find the short-circuit current under the ambient conditions.

6.) Even when a module is biased in short-circuit condition, a voltage drop occurs across R_s. As a result, the junction still experiences a voltage bias and there are currents flowing through both the recombination path and through R_sh when the terminal voltage of the device is zero, i.e. the recombination term does not go to zero in the short circuit condition. Therefore the photocurrent, I_ph must be greater than I_sc in order to supply parasitic currents as well as the external current which has the rated I_SC,ref value. Find the actual I_ph as follows:

The temperature dependence on voltage is also computed, but not used elsewhere in the simulation. Note that μΙ_sc ≅ α_Iph, given in 1/°C.

 

Reference

Schwieger, M., Michalksi, S., Non-Linearity of Temperature Coefficients, Equivalent Cell Temperature and Temperature Behaviour of Different PV-Module Technologies. TÜV Rheinland Energie und Umwelt, Cologne, Germany. Proceedings from the 28th EU PVSEC.