Helical geometry is widely used in heat transfer systems due to the high heat transfer surface and the creation of swirling flow. Grooving the spiral channel can lead to the strengthening of these effects and improve the channel performance. In the present study, the energy and exergy performance of a nanofluid-based photovoltaic thermal unit equipped with a grooved helical microchannel heat sink is investigated experimentally. For this purpose, a plain helical microchannel heat sink, a parallel grooved helical microchannel heat sink and a staggered grooved helical microchannel heat sink are designed and fabricated. The employed nanofluid is the aqueous suspension of Fe3O4 nanoadditives. The experiments were performed at different values of flow rates (20–80 kg/h) and nanoadditive concentrations (0.0–2.0 %). The highest thermal energy/exergy, electrical energy, and their corresponding efficiencies have been recorded at the mass flow rate of 80 kg/h and nanoadditive concentration of 2.0 %. It is seen that the overall energy efficiency of the staggered unit is 17.05 % and it is 6.96 % higher than the plain and parallel unit. Further, the staggered unit demonstrated the highest exergy efficiency (14.67 %) compared to other studied photovoltaic/thermal units.
