Thermal regulation and performance assessment of a hybrid photovoltaic/thermal system using different combinations of nano-enhanced phase change materials

Combining hybrid photovoltaic/thermal (PV/T) and photovoltaic/phase change material (PV/PCM) systems in a so called hybrid PV/T/PCM system is a potential solution for the high temperature gradients and unsatisfactory thermal regulation in conventional PV/T systems. Several combinations of different PCMs and different types of nanomaterials at different loadings are employed in this study to overcome the increased PV-temperature levels in the presence of a PCM and improve both the cooling and the thermal regulation of hybrid systems. A finite difference numerical model was developed and validated to evaluate the average PV panel temperature, the temperature gain across the cooling fluid, the thermal and electrical efficiencies, and the temperature distribution along the PV panel for the hybrid PV/T/nano-enhanced PCM system. The effects of the solar concentration and the operation season (summer or winter) were also assessed. Four types of PCMs and four nanoparticle materials were used at high loadings of 10 wt %, 20 wt %, and 30 wt %. When paraffin wax RT35 is used as the PCM, although the temperature increasing magnitude along the panel decreases from 41% to 12%, PV-temperature levels increase compared to the conventional PV/T system (65 °C with RT35 compared to 47.5 °C without a PCM). Increasing the loading of nanoparticles in a PCM provides better cooling and improved overall performance. Among the nanomaterials, Multi-walled carbon nanotube is the best to obtain better cooling (52 °C for RT35/MWCNT at a loading of nanoparticles of 10 wt %) and higher overall performance. Also, the addition of nanoparticles is more effective at higher solar concentrations. The CaCl₂.6H₂O PCM provides better performance and relatively lower temperature levels, while the RT35 provides better thermal regulation of the PV panel, but at relatively higher temperature levels. No previous work has been conducted to study the effect of different combinations from the nano-enhanced PCMs on the performance and thermal regulation of the new hybrid PV/T/nanoPCM systems. In addition, the study is the first to assess their effect at high loadings of the nanomaterials and under different solar concentrations in summer and winter.