Review of Solar Pond Performance With PCM and NePCM

Abstract

The Salt gradient solar pond (SGSP), or only solar pond (SP), is a system that utilizes a renewable solar energy source to store thermal energy in a brine. The use of phase change materials (PCMs) and nano-enhanced PCMs (NePCMs) to improve SGSPs performance has received limited attention in previous review articles. The current review organizes the available research into two primary groups to address this gap: SGSPs with PCMs and SGSPs with NePCMs. It also aims to uncover the challenges and areas where further investigation is needed and suggest future research paths to improve the efficiency and effectiveness of solar thermal energy technologies. The classical PCMs, especially paraffin wax, have high latent heat but low thermal conductivity, which has drawbacks to their effectiveness. The NePCM involves using nanoparticles like copper oxide (CuO) and aluminum oxide (Al2O3) to augment the heat transmission and thermal conductivity of PCMs substantially. The outcomes of different studies revealed that integration of SP with PCM enhances the SP's thermal and salinity stability, improves the average exergy and thermal efficiencies, decreases the heat loss from the SP, extends the operation duration, and results in more uniformity and less fluctuation in temperature compared to the SP without the PCM system. Using a PCM of a high melting temperature enhances SP stability and smoother SP peak temperatures. Meanwhile, lower melting PCM results in a more stable temperature during heat extraction. In addition, dispersion nanostructures with the PCM augment the thermal features, extend the operation period of the SP, and increase the stored energy within the SP and the thermal efficiency (up to 87.58 %). In addition, adding nanoparticles increased the average maximum temperature by 3.5 %-37.7 % depending on the nanoparticles' loading and type, PCM kind, and other geometrical parameters and weather conditions. In addition, attention should be paid to balancing the thermal enhancement effect and the adverse effect of increasing nanoparticles' viscosity and agglomeration possibility, especially at a relatively large concentration. Moreover, the affecting controlled parameters, the challenges faced by utilizing PCM and NePCM in SP applications, and suggestions for future studies are also discussed.