Latent heat thermal energy storage heat exchangers store heat energy by virtue of the phase transition that occurs in the thermal storage media. Since phase change materials (PCMs) are utilized as the media, there is a critical necessity for the appropriate selection of the PCM utilized. Since multiple thermo-physical properties and multiple PCMs are required to be evaluated for the selection, there arises a need for multiple criteria decision making (MCDM) algorithms to be adopted for the selection. But owing to the different weight estimation techniques employed and the voluminous quantity of selection algorithms available, there arises a need for a comparative methodology to be adopted. This study was intended to select an optimal PCM for a sustainable steam cooking application coupled with a thermal energy storage system. In this research study, six PCMs were chosen as the alternatives and five thermo-physical properties were chosen as the criteria for the evaluation. 11 different algorithms were augmented with 3 different weight estimation techniques and therefore a total of 33 algorithms were employed in this study. All of the algorithms have chosen Erythritol as the optimal PCM for the application. The outcomes of the MCDM algorithms have been validated through an intricate Pearson’s correlation coefficient study.

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In this research work, nano-phase change material (NPCM) composites were prepared by adding 1 %, 2 %, and 3 % mass fractions of highly conductive carbon-based graphene nanoparticles into the base phase change material (PCM). The existence and uniform graphene dispersion in the PCM was confirmed through Raman spectrometer and scanning electron microscope (SEM) analysis. The Fourier transform infrared (FTIR) and x-Ray diffraction (XRD) results showed that all three NPCM composites were chemically stable, and their crystallinity was similar to the base PCM. For the sample with 3 % graphene, the solid-state thermal conductivity was increased by 219.89 %, and liquid-state thermal conductivity was increased by 161.65 %, with a 3.52 % drop in latent heat capacity was revealed from differential scanning calorimetry (DSC) analysis. All NPCM composites have onset and peak melting temperatures closer to the base PCM. Hence, the NPCM composites can be employed for thermal energy storage (TES) integrated solar water heater (SWH) applications.

Low thermal conductivity of organic phase change materials (PCMs) for thermal energy storage systems induces the necessity to apply suitable heat transfer enhancement techniques for these materials. The purpose of this study was to improve thermal conductivity of a PCM erythritol by using sodium chloride as an additive, such that the material can be applied for steam cooking systems when integrated with solar parabolic trough collectors. In this study, erythritol-NaCl composites were synthesized by using the melting method, and the key physicochemical properties of the composites were estimated by using differential scanning calorimetry (DSC) coupled with thermo-gravimetric analysis (TGA). The observations indicate that there has been a significant improvement in the thermal conductivity of erythritol supplemented with NaCl. Further, thermal behaviour of the material indicates that it is suitable for steam cooking applications. Furthermore, mathematical models based on the experimental observations can be potentially utilized for further studies of erythritol-NaCl composites.

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