Nominal Operating Cell Temperature

Nominal Operating Cell Temperature

The presence of an air gap between a photo voltaic (PV) module and roof facilitates ventilation cooling under the device and consequently reduces cell temperature and improves its performance. In case of rack-mounted PV installation, the Nominal Operating Cell Temperature (NOCT) method could be effectively used to predict the temperature of the module for various environmental conditions. Temperature and heat flux measurements for each panel, and environmental parameters were recorded. Two temperature prediction models, NOCT model and SNL (Sandia National Laboratory) model were used to predict Roof top temperature and energy efficiency so that their suitability for Roof top could be evaluated. SNL model takes into account also the wind speed.

If  a total of 168 PV modules are mounted above the roof of the building. They are elevated by 0.3 m to allow for cooling through natural ventilation and are grouped into 22 arrays of different orientation and tilt due to the curved shape of the roof. All PV modules are poly crystalline modules of 305W rated power. The size of each PV module is 1.658 m and 0.834 m, resulting in a PV module area of 1.38 𝑚2 and an active cell area of 1.22𝑚2. The nominal operating cell temperature(NOCT) of the PV module is given as 47.5 degree Celsius , which results in an efficiency value at NOCT of 12.3%, assuming a typical temperature coefficient for poly crystalline cells of 0.45%.