In master’s thesis an analysis of improving the thermal energy storage in sensible storage tank with integration of modules with phase change materials is presented. A series of measurements has been carried out under variable conditions, followed by a validation of simulation model that was performed with a software package TRNSYS. In mentioned software package a comparison between sensible heat storage with and without built-in modules with a phase change material was made at different shares of filling material and temperatures of heat storage. It has been found out that with the implementation of phase change materials in the sensible heat storage the density of saved energy is increased. Consequently, the heat storage can provide desired outlet temperature of water for a longer period of time. It was also concluded that higher filling percentage of a phase change material is more efficient and their usage is more appropriate in narrow temperature ranges of storing thermal energy.