Investigation of the Ca(NO3)2-NaNO3 mixture for latent heat storage

In this paper, calcium nitrate and sodium nitrate are mixed in different molar ratios to form a cheap phase change material. The result shows that these binary mixtures all have exothermic peaks at around 220 °C, and the observed enthalpy increases with the NaNO3 ratio. Further study indicates that although Ca(NO3)2 and NaNO3 are mixed in different proportions, the mixture always first melts in the eutectic composition. Different Ca(NO3)2 and NaNO3 ratio will lead to different amount of eutectic production, thereby resulting in different observed enthalpy. The sample with Ca(NO3)2 and NaNO3 molar ratio of 3:7 shows the best heat storage performance. Specific heat capacity, compatibility and thermal conductivity are also measured in the paper. The cost of the 3:7 mixture is only about half of solar salt, but they have a similar latent heat storage capacity. Overall, this mixture shows a good application advantage.