The hydration and dehydration of the TCM material take place in a reactor. This may be a separate reactor or the reactor may be integrated in the storage, as shown in the systems presented in Fig. 1.

If the TCM material is a solid, nowadays integrated reactors are used. This has the advantage that it is not necessary to transport the solid material. However, for large storages such as seasonal storage, this also has disadvantages such as a larger sensible heat loss, especially if the storage is not compartimented since then the whole reactor content has to be heated up before dehydration occurs. Also the required heat exchange area is much larger than for a separate reactor. In a separate reactor, it is possible to heat up only the required amount of TCM, thereby making the charging process much more efficient. Similar benefits occur on discharging the material. Also, the heat- and vapour transfer can be optimised within a separate reactor by stirring of the material.