Characterization of Thermophysical Properties of Molten Salts Used in CSP Plants Using the dT-History
Abstract
Accurate thermophysical characterization of molten salts is essential for the efficient design of thermal energy storage (TES) systems in concentrated solar power (CSP) plants. Differential scanning calorimetry (DSC), the standard method, uses millimeter-sized samples that may not be representative of the behavior of bulk material. This work presents a complete experimental protocol for the implementation of the dT-History method, a low-cost calorimetry technique based on the RC circuit analogy, to characterize a 130 g sample of solar salt (60% NaNO₃, 40% KNO₃). The methodology includes systematic calibration of the calorimeter components, followed by sample analysis. The results generated the specific heat curve cp as a function of temperature, successfully identifying the solid-solid (~105 °C) and solid-liquid (~220 °C) phase transitions. Although the results are qualitatively similar to the DSC data in the literature, a quantitative discrepancy in the transition temperatures was observed. It is concluded that the dT-History method is a validated and robust alternative, and it is postulated that the discrepancies observed are due to the use of a more representative sample size, capturing dT/dt thermal dynamics that DSC omits.
Keywords
Thermal Energy Storage (TES), Concentrated Solar Power (CSP), Molten Salts, dT-History Method, Calorimetry, Specific Heat, Solar Salt