NABCEP Technical Sales Practice Exam

Delta T in the context of string sizing refers to the temperature difference between the operating temperature of a solar cell (or module) and the standard test condition (STC) temperature, which is typically set at 25 degrees Celsius. To calculate Delta T, you would indeed subtract the STC temperature from the actual cell temperature.

For example, if the cell temperature is measured at 40 degrees Celsius, you would calculate Delta T by taking 40 - 25, resulting in a Delta T of 15 degrees Celsius.

This calculation is critical in various applications, including understanding how temperature impacts the performance and efficiency of solar panels. The performance characteristics of solar modules, such as voltage output and efficiency, can degrade as temperatures rise above the standard test condition, thus making this calculation vital for accurate system design and performance assessment.