The phase change eutectic compound, KNO3/NaNO3 (50/50mol%) (phase change material (PCM)), which is used as the thermal energy storage material in the solar thermal power plant, was quasi-encapsulated into the SiC-honeycomb (SCH) for suppressing the natural convection occurring at the liquid state of PCM. The performance of the SCH as the material suppressing natural convection of PCM was investigated experimentally. PCM with three kinds of mixing ratios of SCH of 10%, 20%, and 30%, was prepared and packed in their respective stainless can with oil-flowing pipe in the center, which is called thermal energy storage unit (TESU). Three units were linked together and stacked vertically by the connector at the inlet/outlet oil pipe. The time variation of temperature at the fixed positions inside the TESU in charging/discharging process and temperature gradient in the radial direction inside TESU when PCM was liquid state were investigated. It is concluded that the natural convection is suppressed by mixing the SCH with PCM up to around 30% in weight, because the PCM is quasi-encapsulated into cell holes and porous structures of SCHs. And thus, the heat transfer of the PCM+30%SCH composite is controlled mainly by its thermal conduction, which is also supported through comparison of simulation result with experimental one. And so, we conclude that SCH has a function as the quasi-encapsulating material for suppressing the natural convection of PCM. Copyright (c) 2015 John Wiley & Sons, Ltd.