Effect of Elastomeric Coating on the Properties and Performance of Myristic Acid (MA) Phase Change Material (PCM) Used for Photovoltaic Cooling

Abstract

Nitrile butadiene rubber (NBR) latex exhibits excellent tensile properties, chemical resistance, and thermal stability in applications such as gloves and safety shoes due to vulcanization. In this research work, attempts have been made to manipulate the vulcanization to produce thin and compact elastomeric NBR coating on myristic acid (MA) phase change material (PCM) to produce shape-stabilized PCM. The proposal for the use of latex-based elastomeric coating for PCM has been rarely considered in the literature due to a lack of understanding of the crosslink of elastomers. Thus, in this research, the effects of sulfur formulation on the coating performance of NBR on the PCM in terms of latent heat and thermal stability were determined. Leakage analysis indicates that the MA pellet coated with 0.5 phr of sulfur-cured NBR layer (MA/NBR-0.5) successfully eliminates the leakage issue. A tensile analysis revealed that a durable PCM coating layer must possess a combination of the following criteria: high tensile strength, ductility, and flexibility. Fourier transform infrared analysis (FTIR) and electron microscopy images showed the formation of thin, compact, and continuous NBR coating when 0.5 phr of sulfur was used. The further increment of sulfur loading between 1.0 and 1.5 phr causes the formation of defects on the coating layers, while non-vulcanized NBR layers seem to be very weak to withstand the phase-change process. The recorded latent heat values of melting and freezing of MA/NBR-0.5 are 142.30 ± 1.38 and 139.47 ± 1.23 J/g, respectively. The latent heat of the shape-stabilized MA/NBR-0.5 PCM is reduced by 32.24% from the pure MA latent heat density. This reduction is significantly lower than the reported latent heat reduction in shape-stabilized PCMs in other works. The thermal cycle test highlights the durability of the coated PCMs by withstanding up to 1000 thermal cycles (2.7 years) with less than 2% changes in latent heat value. Cooling performance test on photovoltaic (PV) module shows that the fabricated shape-stabilized PCM could reduce the temperature of the PV module up to 17 °C and increase the voltage generation by 7.92%. Actual performance analysis of shape-stabilized PCMs on the cooling of the PV module has been rarely reported and could be considered a strength of this work.