Exergy and energy analysis of wavy tubes photovoltaic-thermal systems using microencapsulated PCM nano-slurry coolant fluid

To develop a more efficient water-cooled photovoltaic-thermal system, energy and exergy analysis of a photovoltaic-thermal system with wavy tubes are investigated numerically using different coolant fluids. A comparison between the straight tube and wavy tubes is conducted for various wavelengths and wave amplitudes. The geometrical parameters of the wavy tubes as well as the velocity of the coolant fluid are examined. Besides, the consequences of coolant fluid including water, Ag/water nanofluid, microencapsulated phase change material slurry, and also a new type of cooling fluid called microencapsulated phase change material nano-slurry are studied. The results show that the electrical, thermal, and exergy efficiencies of the photovoltaic-thermal module enhance by using the wavy tubes compared with the corresponding straight tubes. By declining wavelength in a constant wavelength/amplitude, the heat absorbed by the heat transfer fluid raises. For the best configuration, the primary and exergy efficiencies of the module increase by 6.06% and 4.25%, respectively, for the wavy tubes system compared with those for the straight unit. Furthermore, in both configurations, by increasing the inlet velocity, the overall performance of the photovoltaic-thermal module increases due to a higher heat transfer rate. The results also reveal that among different types of cooling fluids, the microencapsulated phase change material nano-slurry has higher performance in terms of both energy and exergy efficiencies due to having higher thermal conductivity and heat capacity. By employing the wavy tube and the novel proposed coolant fluid, the primary and exergy efficiencies increase in comparison with a typical photovoltaic-thermal module.