Increasing the operational aspect of heat storage system (HSS) contributes to significant positive influence on thermal system. As one fast-developing storage technology, modification of the material HSS (MHSS) has become crucial, specifically for organicbased MHSS. The drawbacks of poor phase transformation during energy intake and release (charging/discharging) of MHSS make undesirable performance for heat exchange and effective operation. To solve the problem, this work proposes modification of pure octadecanoic acid (POA) as MHSS by forming polymeric-embedded OA (PEOA). Evaluation is taken for the heating/cooling cycle operation of the HSS, showing positive contribution of the proposed method. The PEOA reduces the preheating duration by 14.8%, meaning the charging ratio can be improved effectively for the HSS. The effective energy ratio for PEOA is obtained with maximum value of 83.9%, which is higher than the POA with 74.8%. It is accounted for the application of PEOA since it allows a suitable solidification process on the heat release, making the maximum total heat loss drop to 17.9%. The profile observation using microscope electron demonstrates the stable formation of PEOA as a direct result of the presence of polymer structure of the composite. The result demonstrates the improvement in the operation of HSS unit, which is linked to the stabilized material, achieving a favorable energy ratio that potentially promotes better operation and control of HSS unit. Moreover, a consecutive discharge cycle for the heat storage tank (HST) using PEOA also brings positive outcomes and improves the heat discharge stage. [ABSTRACT FROM AUTHOR]