This thesis deals with the final construction and the starting operations of a newly built test facility for heat storage at high temperatures. As storage medium for the thermal energy storage (TES) sand is used, from which the name of the described system, sandTES, can be derived. When storing the thermal energy from the heat transfer medium Therminol VP-1 is transferred to steel tubes, passed on to the fluidized powdery storage medium. In reverse order, the heat transfer occurs when unloading the heat. The pilot plant is designed for 200 kWth. In the course of this thesis, the piping of the thermal oil plant with the individual pilot plants was designed and built. A compressed air system for the entire plant, as well as the sensor system for the sandTES-plant was designed and constructed. Furthermore, the necessary valve positions of the air piping and re-cooling have been developed and constructed and an overpressure safety protection for a recuperator has been constructed. The present work includes both a technical description of the plant with all its components as well as a documentation of the completed activities.