An experimental and numerical analysis of an improved thermal storage tank with encapsulated PCM for use in retrofitted buildings for heating

In the building sector, 40% of final energy is used for heating and cooling. Up to 75% of this is used in residential buildings. It is necessary to take a step forward and reduce this share of energy consumption, in particular through the use of efficient technologies and their integration into the system of renovation of residential buildings, which is a major challenge for future research in this field. An important technology for achieving this goal is heat storage, where the use of phase change materials as heat storage material allows for a higher energy density. The main advantage of using heat storage technologies is the solution of the problem of the temporal divergence of energy demand and the possibility to use a higher share of energy from renewable sources, e.g. such as solar energy. Solar energy as a resource can be used during the day, when production is higher than demand, which allows storing energy for a later period of demand. This also improves the efficiency of the heat generators in the system in which the thermal storage is integrated. The focus of the present study is on the investigation of phase change materials (PCM) as thermal storage in the conventional water tank storage. A comparison was made between a conventional sensible thermal energy storage tank and a hybrid latent heat storage tank, where the PCM was encapsulated in cylindrical nodules and integrated into the water tank to improve the energy density of the conventional water heat storage tank. The results of the experiment showed that 15% of the PCM inside the water storage tank increases heat storage for 70% over conventional heat storage tank with water only inside. The measured experimental data were compared with the simulation results from TRNSYS model to enable further analysis and improvement of the heat storage tank with PCM integration.