In future energy systems, storage will have a primary role, allowing smaller generation units. What is more for non-intermittent renewable energy sources such as solar and wind, storage is strictly necessary. The cost of electrical batteries is still very high, so one of the preferred storage technologies is the thermal one. In fact, thermal energy is used both as it is and as a source to be convert it into other forms. Thermal energy storage can increase the efficiency of industrial plants by exploiting waste heat and the efficiency co-generation plants by making the generation independent from the demand curve. Among thermal energy storage phase change materials(PCM) represent an opportunity thanks to their large latent heat that can reduce the size of storages.