Processing Key I-V Points
The “Key I-V Points” input option provides an alternative to “basic datasheet” parameters as input for the module file generating algorithm. This is a pre-processing step to the core module file generator. This input format is modeled after the IEC-61853-1 test standard, defined by the International Electrotechnical Commission (IEC) as: “requirements for evaluating PV module performance in terms of power (watts) rating over a range of irradiances and temperatures…a second purpose is to provide a full set of characterization parameters for the module under various values of irradiance and temperature”. See the “Inputs” below for more information.
*Important Note: These inputs are intended to be provided for multiple temperature/irradiance conditions (, ).Each set of inputs is represented by a row in the Key I-V Points user interface. The minimum required input is data at STC.
Key IV Points Algorithm
- The only required row of inputs is for STC conditions. The provided values for maximum power, voltage at maximum power, current at maximum power, short-circuit current, and open-circuit voltage are assumed to be the final “Electrical Characteristics at STC” of the module.
- If data is provided at multiple temperatures, temperature coefficients will be calculated for Pmp, Voc, and Isc. This is done by performing a linear regression where the x-values are temperature, and the y-values are the respective electrical characteristic at each temperature (and G = 1000 W/m2). The resulting temperature coefficients are calculated in units [%] by dividing the slope of the linear fit by the respective electrical characteristic at STC.
- For each temperature, if data is provided at multiple irradiances, relative efficiency at each irradiance is calculated from each as in step 4 of the documentation for “Effective Irradiance Response (EIR) Calculation”.