Calibration of Irradiance Sensor by Independent Accredited Organization

Solar irradiance measurement is a cornerstone of the Performance Ratio (PR) measurement of a PV plant. The solar irradiance for “Performance Ratio” is nowadays measured with referance cell irradiance sensor (PV Pyranometer). That is why the irradiance sensor to be used in the PV plant must be calibrated according to the latest version of IEC 61724-1 and it must comply with certain classifications according to the latest version of IEC 61724-1, also. Irradiance sensor classifications according to the IEC 61724-1 standard are given in the table below.

Sensor Type	Class A High Accuracy	Class B Medium Accuracy	Class C Basic Accuracy
Referance Cell Irradiance Sensor (PV Pyranometer)	Uncertainty ≤ 3 % from 100 W/m2 to 1500 W/m2	Uncertainty ≤ 8 % from 100 W/m2 to 1500 W/m2	Any

Table 1 – Irradiance sensor classifications according to the IEC 61724-1

SEVEN irradiance sensor is a Class A (High Accuracy) irradiance sensor according to the IEC 61724-1 standard has been verified by the calibration performed in Germany by an independent accredited organization “Calibration and Test Center (CalTeC) Solar Cells Institut für Solarenergieforschung GmbH”. The uncertainty of the irradiance sensor is determined as a function of the temperature of the photovoltaic cell at an irradiance of 1000 W/m² using a Class A+AA+ sun simulator. The calibrated SEVEN irradiance sensor is given in the figure below. This sensor provides wires that allow a Virr voltage measurement relative to the incident radiation. In addition, the sensor provides wiring for the internal cell temperature sensor. A high accuracy Class A PT1000 sensor is used to measure the internal cell temperature.

Figure 1 – The irradiance sensor calibrated in Germany

According to the temperature‐dependent measurement results of the SEVEN irradiance sensor under standard test conditions (1000 W/m2, AM1.5G reference spectrum and 25 °C), the uncertainty was calculated as 2.4%. This value fulfill the “Uncertainty ≤ 3%, from 100 W/m2 to 1500 W/m2″, which a Class A (High Accuracy) irradiance sensor must comply with in the IEC 61724-1 standard. Temperature‐dependent measurement data are printed in Table 2. These results are plotted in Figure 2.

Table 2 – Uncertainty of the examined irradiance sensor

Figure 2 – Graphical representation of the data of the uncertainty of the examined irradiance sensor

You can find the SEVEN irradiance sensor calibration certificate given by an independent accredited organization (CalTeC ISFH) click here.