Effects of Nanofluids on the Performance of a PCM-Based Thermal Energy Storage System

To study the thermal effects of using nanofluid as a heat transfer fluid (HTF) in a thermocline-type packed-bed energy storage tank filled with spherical phase-changing material (PCM) capsules, an in-house Fortran code is developed and validated using existing experimental and numerical data. The current assessment study shows that use of a nanofluid as HTF is able to accelerate the charging and discharging periods, hence positively affecting the thermal storage efficiency. For instance, using a nanofluid with a 5% nanoparticle concentration as HFT would reduce the charging/discharging period by about 20%. Hence, the current findings reveal that the use of a nanofluid as HTF should be considered for future design of thermocline-type packed-bed energy storage tanks of commercial size. The fact that the nanoparticles' concentration is directly affecting the heat transfer rate can be used as an adjustable parameter during the design and optimization stages of the thermal storage.