Heat storage system and method for the charging and discharging thereof

A thermal storage system, comprising:

• a phase change storage material with a thermal expansion below 20% wherein said phase change storage material is located within a casing;
• a heat exchanger via which a heat-transfer fluid circulates;
• and
• a drum;
• wherein:
• said heat exchanger comprises heat exchanger tubes that penetrate the storage material with which they are in continuous contact;
• the heat exchanger tubes are connected at their lower part with at least one lower chamber via lower sub-chambers which include a series of injectors where the heat-transfer fluid is inserted in gas form to the lower part of the heat exchanger;
• in the upper part, the heat exchanger tubes connect with at least one upper chamber via upper sub-chambers;
• the upper chamber is, in turn, connected to the drum located outside of the casing and above the upper chamber;
• and
• extending from the drum is an extraction pipe for heat-transfer fluid in gas form, an entry or exit pipe for heat-transfer fluid in liquid form, and one or more recirculation downpipes via which the heat-transfer fluid in liquid form circulates, the one or more recirculation downpipes being located outside of the drum and connecting the drum to the lower chamber, enabling the natural circulation of the heat-transfer fluid within the system.