Abstract
This study presents the energy storage potential of nitrate salts for specific applications in energy systems that use renewable resources. For this, the thermal, chemical, and morphological characterization of 11 samples of nitrate salts as phase change materials (PCM) was conducted. Specifically, sodium nitrate (NaNO3), sodium nitrite (NaNO2), and potassium nitrate (KNO3) were considered as base materials; and various binary and ternary mixtures were evaluated. For the evaluation of the materials, differential Fourier transform infrared spectroscopy (FTIR), scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to identify the temperature and enthalpy of phase change, thermal stability, microstructure, and the identification of functional groups were applied. Among the relevant results, sodium nitrite presented the highest phase change enthalpy of 220.7 J/g, and the mixture of 50% NaNO3 and 50% NaNO2 presented an enthalpy of 185.6 J/g with a phase change start and end temperature of 228.4 and 238.6 °C, respectively. This result indicates that sodium nitrite mixtures allow the thermal storage capacity of PCMs to increase. In conclusion, these materials are suitable for medium and high-temperature thermal energy storage systems due to their thermal and chemical stability, and high thermal storage capacity.
Highlights
Efficient energy storage systems have emerged because of the interest in reducing the greenhouse gas (GHG) emissions caused by the increasing energy demand [1]
Fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), and Scanning Electron Microscopy (SEM) analyses of the samples were conducted to obtain conclusive data about the workability of the nitrate salts as phase change materials (PCM) and avoid errors associated with the experimental setup
Through the FTIR analysis, it is possible to identify the functional groups of the molecules that make up the analyzed material, meaning that the composition of the sample ould be known
Summary
Efficient energy storage systems have emerged because of the interest in reducing the greenhouse gas (GHG) emissions caused by the increasing energy demand [1]. The article of Talebizadehsardari et al, Consecutive charging and discharging of a PCM-based plate heat exchanger with zigzag configuration [23], studied the remarkable energy savings, isothermal nature of the operation and low costs, energy storage with a plate type heat exchanger with zigzag configuration In this way, SiO2/Al2O3 nanoparticles added to Solar Salt can increase the heat of fusion by 7.4% and the specific heat by 52.1% in the solid phase and 18.6% in the liquid phase [19]. It was established that inert atmosphere is required above 300 ◦C with nitrogen as an inert gas [70,71] In this context, this research work determines the thermo-physical properties of nitrate salts (NaNO3, NaNO2, and KNO3) and their binary and ternary combinations due to the discrepancy and errors associated with different experimental setups conducted in different studies. Nitrates as PMC were characterized through Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to establish their feasibility as PCMs for renewable energy storage applications
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