Nitrate salts have better thermal stability, low vapour pressure and non-toxic nature compared to synthetic heat transfer oil like Therminol VP-1®. Solar salt, a mixture of 60% NaNO ₃ -40% KNO ₃ by weight, is finding increased application as a Heat Transfer Fluid (HTF) and Thermal Energy Storage (TES) material in Concentrated Solar Power (CSP) plant. In this research work, two novel salt mixtures are prepared and tested for their melting point, short and long duration thermal stability. The formulation 1 is a ternary salt comprising of 44% KNO ₃ -32% Ca(NO ₃ ) ₂ -24% NaNO ₃ , referred to as Base Salt. Formulation 2 is a quinary mixture of 90% Base salt-5% NaCl-5% KCl, referred to as Base-Chloride. Solar salt, a third formulation, is also tested and compared alongside the novel mixtures. The experiments conclude that the melting point of solar salt is 223°C, Base salt is 135.8°C and Base-Chloride is 142.2°C. When heated at 5°C/min, the decomposition (3% mass loss) of solar salt is observed at 631°C, Base salt at 585°C and Base-Chloride at 589°C. Considering long duration stability, all the three mixtures remain stable till 400°C, when heated at constant temperature for 24 hours. The novel mixtures have significantly lower melting points, thus providing wider operating temperature range compared to solar salt for both heat transfer and energy storage application. Moreover, it is observed that addition of chloride salt as an impurity to a nitrate mixture does not change its operating range significantly.

Resorption systems (RES) utilize the difference in ammonia equilibrium between two distinct salts to produce useful heating/cooling. The salt with comparatively lower ammonia affinity is used as a Low-Temperature Salt (LTS), while the other is used as a High-Temperature Salt (HTS), in a two-reactor system. In this work, BaCl₂, MgCl₂, NaBr, NH₄Cl and SrCl₂ are paired with 18 different HTSs, and each pair is studied and thermodynamically mapped for high/low operating temperatures, pressures, COP and energy output. NH₄Cl and NaBr are found to be promising LTSs, while SrBr₂ and MnSO₄ are found to be more suited as HTSs. The resulting four combinations can be used for residential heating in the United Kingdom. The thermodynamic cycle evaluations suggest that the COP range lies between 1.10 and 1.50. In addition, more than 4140 J g_NH3⁻¹ of heat energy can be delivered using these pairs for residential heating at 50 °C.