Effects of pump power on performance analysis of photovoltaic thermal system using CNT nanofluid

摘要

In this study, a numerical simulation has been accomplished to investigate the performance of a photovoltaic thermal system (PVT) with respect to the energy consumption of fluid circulating. Three dimensional numerical models of the PVT system were conducted in ANSYS Fluent software using water-CNT nanofluid as working fluid. Three configurations of heat collectors were modeled to select the more efficient design for collecting the heat of the PV module. By applying the duct channel heat collector, the effects of CNT concentration and nanofluid flow rate on the electrical and thermal efficiency of PVT system were studied. With flow rate of 50 L/h of 0.1 v/v% CNT-nanofluid, the electrical efficiency of PVT system increased 11% in comparison to PV system at ambient temperature of 40 degrees C. According to the inconsistency of thermophysical properties of nanofluid, a sensitivity analysis was conducted to indicate the impact intensity of nanofluid thermal conductivity. It indicated that the application of a 15 W pump in PVT system decreased the electrical efficiency from around 13.9% to 12.9%. A coefficient of cooling efficiency (CCE) is introduced to compare the extra gain electrical energy with the energy consumption of the pumping system. By increasing the thermal conductivity of nanofluid, the CCE increased from 0.985 for 25 W pump to 1.015 for 20 W pump. Two practical methods were suggested and investigated with transient simulation to decrease the energy consumption of the pumping process up to 50%.