Nano-material based composite phase change materials and nanofluid for solar thermal energy storage applications: Featuring numerical and experimental approaches

Continuously raising the photovoltaic thermal (PVT) module's cell temperature reduces the system's electrical efficiency, reducing its effectiveness. Therefore, one of the ways to maintain the desired efficiency is to install a hybrid PVT system with the incorporation of Phase Change Material (PCM). The utilization of PCM has been identified as a promising method of storing thermal energy in a thermal energy storage (TES) system. However, the effective usage of PCM is restricted due to their low thermal conductivity attribute that prevents their efficient applications in the practical world. The dispersion of nanoparticles into the base-fluid (nanofluid) and PCM has been regarded as a promising method for improving the thermal conductivity of PCMs and thus reducing thermal energy charging and discharging duration. This work aims to critically and fully investigate the research on nanoparticle incorporation in PCMs and the preparation of nanofluids for the improvement in thermophysical properties for both. Some studies showed that the increment reached over 1000 % and carbon-based nano- particles triumphed over the performance of metal-based nanoparticles. The usage of graphite-based nano- particles with 7.5 % and 10 % by weight increased the thermal conductivity by around 620 % and 1100 % respectively. The review also considers the environmental impact of using nanofluid and NEPCM, reducing the CO2 2 emission by around 448 kg/m2.yr 2 .yr with the utilization of carbon-based nanofluid (CNT/water) in the hybrid PVT system. This review also provides in-depth information about the perspective benefits, environmental impacts, and challenges of implementing nanotechnology as nanofluid and NEPCM, and it highlights the significance of continuing research and development in this area to push forward the solar energy conservation and conversion process to be uplifted.