Preparation and thermal property characterization of NaCl–Na2CO3–Na2SO4 eutectic salt mixed with carbon nanomaterials for heat storage

Coupling with supercritical power cycle can improve the thermal efficiency of the concentrated solar system. Design the suitable thermal storage medium is critical to the new coupling system. A new ternary eutectic salt with low cost was developed composed of NaCl, Na2CO3, and Na2SO4 based on the calculation method of phase diagram, meeting the requirements of solar energy storage over 873 K. The eutectic point and composition of the designed salt were predicted to be 900 K and 50 mol% NaCl-35 mol% Na2CO3-15 mol% Na2SO4. The designed salt shows high specific heat capacity and phase-change enthalpy, and low cost, which indicates it has good thermal storage capacity. Composite phase change materials with multi-walled carbon nanotubes and graphene nanosheets which can enhance the thermal conductivity and heat capacity of designed salt were prepared. The effects of preparation methods on the thermophysical properties of the composite phase change materials were analyzed.