Experimental Investigation of Specific Heat Capacity of Ternary Nitrate Salt Mixtures for Thermal Energy Storage System in Concentrated Solar Power System

Abstract

Concentrated solar power (CSP) systems require efficient thermal energy storage (TES) materials to address the intermittent nature of solar radiation. This study investigates the specific heat capacity (C_p) of novel ternary nitrate salt mixtures composed of potassium nitrate (KNO₃), lithium nitrate (LiNO₃), and magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O) for TES applications. Seven compositions were prepared and characterized using differential scanning calorimetry (DSC) over a temperature range of 30°C to 400°C. The results reveal that the specific heat capacity of all mixtures increases with temperature, ranging from 0.5845 J/g-K to 0.9987 J/g-K at 375 K, with the 40% KNO₃, 30% LiNO₃, and 30% Mg(NO₃)₂·6H₂O mixture exhibiting the highest C_p value of 0.9987 J/g-K. This enhancement is attributed to increased ionic mobility and thermal vibration at elevated temperatures. All mixtures exceed the minimum C_p threshold of 0.5 J/g-K required for TES applications, demonstrating their suitability for CSP systems. The findings highlight the potential of these ternary nitrate mixtures to improve energy storage efficiency, reduce operational costs, and support the broader adoption of CSP technologies. This study contributes to the development of advanced molten salt mixtures for next-generation TES systems, offering a pathway toward more sustainable and efficient renewable energy solutions.