Use Case 6: Key Results

The RESTORE solution proposed and adapted to the Use-Case VI was comprehensively described. The deliverable has presented the design, simulation, and performance assessment of the Use Case 6 TCES storage configuration developed by POLIMI and SIMTECH within the RESTORE project. The TCES system is based on the hydration/dehydration cycle of CuSO₄, which is charged using waste heat from the POLIMI Leonardo campus Combined Heat and Power plant. The discharging phase enables the combined production of electricity and thermal power for district heating through an ORC module.

The design of the system is carried out in the most critical scenario where the heat pump is dimensioned to absorb the entire rejected heat from the CHP plant (equal to 1791 kW), thus ensuring the system is properly sized to manage the full thermal surplus. The system configuration includes a continuously stirred tank reactor for charging and discharging the thermochemical material, coiled tubes heat exchangers for coupling with both the HP condenser (charging) and ORC evaporator (discharging), a vapor compression heat pump for the charging phase, an ORC module for electricity generation during discharging, and dedicated pumps and control valves to circulate the fluids and ensure stable operation across the daily cycle.

The heat pump designed for this use case employs Novec649 as working fluid and achieves a COP of 5.5, providing over 2 MW of heat to drive the charging reaction. The chemical conversion of the TCM features a 95% efficiency and it results in a mass reduction of approximately 19%, corresponding to the release of hydration water. In the discharging phase, the ORC module supplies 1.4 MW of thermal energy to the district heating network, while also generating around 154 kW of net electricity.

Overall, the results demonstrate that the TCES system can effectively valorize otherwise unused low-grade heat, providing flexible thermal and electrical outputs. The modularity and compactness of the daily storage solution, requiring a storage volume of only about 31 m³, make it particularly suitable for an urban context like the POLIMI Leonardo campus energy grid.