The TESS consists of a Latent Heat Thermal Energy Storage LH-TES and a Sensible Heat Thermal Energy Storage SH-TES to minimize entropy production during charging and discharging. Since different refrigerants are considered for the High Temperature Heat Pump HT-HP and the Organic Rankine Cycle, a specific heat exchanger must be designed for LH-TES. Therefore, several simulations and a thermodynamic analysis as well as various simulations of the whole LH-TES unit have been carried out.
For the SH-TES, a two tank configuration was chosen, which considers a hot and a cold tank with pressurized water. During charging and discharging the water will be shifted between the tanks for sub cooling (HT-HP) or rather for preheating (ORC) of the refrigerant in the appropriate circuit. Currently, both components of the TESS are in the tendering process. Please see our deliverable for the detailed design of the high temperature TES laboratory prototype here.