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Paraffin is considered the ideal candidate for latent heat storage material. However, there is a significant problem related to the mushy region that disrupts the heat transfer process and tends to have a high supercooling degree. High-density polyethylene (HDPE) promotes a stable phase transition for the paraffin during the melting/freezing process. Therefore, the present study evaluates the effect of adding HDPE at a different ratio to form composite paraffin to evaluate the supercooling degree of the composite. Four samples are prepared for the evaluation: pure paraffin and composite paraffin/HDPE at HDPE ratios of 5 wt%, 10 wt% and 15 wt%. The static charging/discharging test is performed to estimate the melting/freezing temperature of the sample. Compared to pure paraffin, there is a significant change in the composite's melting/freezing temperature, which implies the effect of HDPE on the sample. The lowest melting temperature occurs at composite with 5 wt% HDPE with a temperature of 58.4 °C. The lowest freezing temperature and supercooling degree are obtained by the sample with 15 wt% HDPE at 68.6 °C and 9.5 °C, respectively. Further observation by using a scanning electron microscope and Fourier transform infrared is discussed in detail within the article. [ABSTRACT FROM AUTHOR]

The effectivity of concentrated solar power (CSP) system to produce solar thermal energy is highly dependent on its reflector's durability. However, since the CSP system is located outdoor, the reflector tends to degrade over time. Thus, it is important to assess the durability of the reflector to understand the soiling effect under a specific environmental condition. The study aims to evaluate the degradation of reflector material in a tropical environment. Solid-state and sheet-based reflectors are tested by environmental exposure for 1080 hours at an elevation of 38 meters after sea level. The mass of the reflector is weighted every 72 hours to observe the mass loss rate during exposure. Sheet-based mirror has the highest mass loss rate of 14.42 mg/day and 23.13 mg/day. Also, it has a higher corrosion rate than solid state mirror, which has a corrosion rate of 0.248 and 1.019 mpy. The article discusses the corrosion mechanism and surface observation using a light microscope in more detail. New material development and improvement on the anti-soiling effect for the reflector can be developed by understanding the degradation and corrosion mechanism of tropical climates. [ABSTRACT FROM AUTHOR]