After the heat has been released to the storage tank, the medium returns cooled through the external collection line to the heat source, where it is heated up again and then returns to the storage modules.
During the discharge process, the discharge pipe system transfers heat to the heat transfer fluid, which it previously absorbed from the sand and the melting cores. Completely different pipelines are used here than for loading.
The mutual penetration of the piping systems ensures a homogeneous distribution of the heat in the module. There is no "heat front" propagating inside.
Most mineral bulk materials are poor conductors of heat. However, the special arrangement of the internals ensures that every point inside the module is close to a metallic element and the heat only has to travel very short distances everywhere.
In the example shown, the pipes are designed in such a way that the innermost area is heated first during loading. When discharging, the heat is first absorbed from the outer areas of the heat storage mass and finally flows through the hot, inner area. In this way, the heat dissipation to the outer wall is reduced.
As a result, the modules are flown through during charging and discharging, depending on the situation and requirements, individually (alternating to one another), one after the other (serial), simultaneously (parallel) or a combination of these.
The heat transfer when flowing through a module results in the gas leaving a module with a temperature change compared to entering. If modules are connected in series, a cascade-like temperature change can be implemented across all modules involved. Mixed temperatures can also be achieved by parallel connection.