Solar modules are usually tested in a laboratory under specific conditions, which are termed standard testing conditions. Standard Test Conditions (STC) are used across the industry to measure the performance of PV modules. These conditions include a cell temperature of 25° C, an irradiance of 1000 W/m², and an air mass of 1.5 (AM1.5) spectrums. This refers to the sunlight’s strength and color when it falls on a clear day on a surface tilted at 37° facing the sun, which is at a 41.81° angle above the horizon. Many manufacturers use STC-based performance measurements in their flash tests.
Crystalline silicon and thin-film PV modules are tested under standard test conditions (STC) to fairly and objectively compare their electrical performance. This evaluation ensures reliable and meaningful assessments of different solar PV modules.
Indoor and Outdoor STCs
The test conditions commonly used by manufacturers are usually based on laboratory or indoor assembly line settings. These conditions, however, differ from the realistic conditions that solar panels experience when installed on roofs or mounting frames.
Outdoor measurements of photovoltaic (PV) panels and modules (or arrays) are conducted outdoors, considering the prevailing irradiance and temperature at the time of measurement. It’s important for designers and homeowners to have reliable information to help them choose the right panel or module for their needs.
Output of PV Modules under Standard Test Conditions (STC)
The output of a photovoltaic (PV) panel under standard test conditions is commonly known as peak watts or Wp and is determined by multiplying the current by the voltage. The Maximum Power Point (MPP) is a significant location on the I-V curve of a PV panel. It marks the peak efficiency and highest output power that the panel can achieve.
Most solar panel installations consistently operate at their maximum capacity. The power output rating of a PV panel is usually the DC rating labeled by the manufacturer. It can be found on the back of the panel, along with other STC values like current, voltage, and wattage. For example, 100 WDC.
Moreover, the Nominal Operating Conditions (NOC) of a PV panel is a standardized set of reference conditions that accurately replicate its performance under real outdoor conditions for measurement purposes.
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