Novel Wide-Working-Temperature NaNO₃-KNO₃-Na₂SO₄ Molten Salt for Solar Thermal Energy Storage

Area of Science:

• Materials Science
• Chemical Engineering
• Renewable Energy

Background:

• Traditional solar salts for thermal energy storage (TES) have limitations in their operational temperature range and specific heat capacity.
• These limitations hinder the efficiency and applicability of solar power generation systems.

Purpose of the Study:

• To design and prepare a novel ternary eutectic salt (TMS) for enhanced TES applications.
• To comprehensively evaluate the thermo-physical properties of the synthesized TMS and compare them with commercial solar salt.
• To investigate the molecular-level mechanisms behind the improved properties using molecular dynamics simulations.

Main Methods:

• Preparation and characterization of a novel ternary eutectic salt (NaNO₃-KNO₃-Na₂SO₄).
• Determination of key thermo-physical properties: melting point, decomposition temperature, fusion enthalpy, density, viscosity, specific heat capacity, and volumetric thermal energy storage capacity (E_TES).
• Comparative analysis with commercial solar salt using experimental data and molecular dynamic (MD) simulations.
• Structural analysis using XRD, FTIR, Raman spectra, and SEM.

Main Results:

• The novel TMS exhibited a lower melting point and a significantly higher decomposition temperature than commercial solar salt, resulting in a wider use temperature range (45.43 °C wider).
• TMS demonstrated a 9.03% higher average specific heat capacity (1.69 J·K⁻¹·g⁻¹) and higher density and E_TES compared to solar salt.
• MD simulations revealed that stronger Na-SO₄ cation-anion interactions in TMS contribute to its higher specific heat capacity.
• Thermal stability analysis showed comparable weight loss at high temperatures, indicating suitability for solar power applications.

Conclusions:

• The novel ternary eutectic salt (TMS) is a promising alternative to commercial solar salt for thermal energy storage.
• Its enhanced thermo-physical properties, including a wider operational temperature range and higher specific heat capacity, improve TES efficiency.
• MD simulations provide molecular-level insights into the superior performance of TMS, supporting its potential for advanced solar power generation systems.