Photothermal properties and photothermal conversion performance of nano-enhanced paraffin as a phase change thermal energy storage material.

The paraffin incorporation in device of glass envelope allows the thermal regulation, increasing the thermal comfort and energy efficiency of buildings. Addition of nanoparticles has an advanced application prospect in the field of solar energy collection and storage capacity of glass envelope systems filled with paraffin. The present study conducts an experimental and numerical investigation in order to study photothermal properties of the paraffin incorporated ZnO or CuO nanoparticles. An experimental and theoretical model is also established to analyze the effect of nanoparticles on the thermophysical and optical properties of nano-enhanced paraffin. The results show that due to the presence of the nanoparticles, the transmittance of nano-enhanced paraffin decreases. On the other hand, temperature increment results in a small rise in the transmittance of nano-enhanced paraffin. The results also indicate that the utilized nanoparticles exhibit a higher attenuation to light, and the scattering effect cannot be avoided, where the maximum scattering proportion is 6.3%. Improvements of 5.87 and 13.12% in thermal conductivity of nano-enhanced paraffin at the volume fraction of 5 × 10−4 vol% are obtained using ZnO and CuO nanoparticles, respectively. The evaluation of the photothermal performance based on the temperature variations shows that the CuO/paraffin can absorb more solar energy. The optimum photothermal performance can be satisfied by the nanoparticle volume fraction ranging from 5 × 10−4 to 1.5 × 10−3 vol%. • Photothermal properties of the paraffin incorporating ZnO or CuO nanoparticles were investigated. • Effects of temperature and volume fraction on photothermal properties were studied. • Optimum nanofluid concentration for glazed structure was determined. • Optimum range of nanoparticle concentration was 5 × 10−4 ~ 1.5 × 10−3 vol%. [ABSTRACT FROM AUTHOR]