**4.1. Irradiance**

Increase in irradiance cause the module temperature to escalate as more heat reaches the surface. Khanjari et al. [2] investigated environmental parameters that affect the efficiency of a PV/T system cooled by nanofluids (*A l* <sup>2</sup> *O*<sup>3</sup> /*water*) via CFD simulation. As the absorbed solar radiation increased from 200 W/m<sup>2</sup> *k* to 800 W/m<sup>2</sup> *k* the electrical efficiency of system decreased from 11.41% to 10.12% for pure water and 11.4% to 10.23% for alumina nanofluid whereas, thermal efficiency increased from 65–79% for pure water and 76–91% for alumina nanofluid. As the absorber plate temperature increased from 291 K to 324 K the electrical efficiency decreased from 11.1% to 9.4% for water and 11.2% to 9.5% for alumina nanofluid whereas, the thermal efficiency did not change with increasing inlet temperature of fluid after reaching a primary value. Similarly, the system efficiency was found to escalate with decreasing irradiation i.e. the maximum overall efficiency of the system was found to increase from 78.60% to 80.58% and 73.58% to 75.93% for 1 wt% and 3 wt% respectively, when the irradiation value decreased from 1100 *<sup>W</sup>*⁄*m*<sup>2</sup> to 600 *<sup>W</sup>*⁄*m*<sup>2</sup> [37]. Effect of irradiance found by Al-Waeli et al. [38] has been presented in **Table 2**.
