Numerical Study of a High Temperature Latent Heat Storage (200-300 0 C) Using Eutectic Nitrate Salt of Sodium Nitrate and Potassium Nitrate

Abstract

In this study, a small scale direct solar thermal energy storage unit for a parabolic dish system with a secondary reflector is designed and developed. The main advantage of thermal energy storage is that thermal energy is available also during times when there is little or no sun shine. In addition, no heat transport fluid is needed in this system. A well insulated heat storage should keep the heat for about 24 hours. KNO3 and NaNO3 in 60:40 percent ratio (mol %) is used as latent heat storage material (PCM). This type of salt is also used in large scale solar power plants producing electricity. Effects of the heat flux and the number of fins on the latent heat storage charging process were numerically simulated using COMSOL Multiphysics. During phase change (melting) of the PCM, large amount of energy in the form of latent heat of fusion is needed. The phase change heat transfer was implemented using the effective heat capacity method.