Energy and exergy analyses of combined thermochemical and sensible thermal energy storage systems for building heating applications

In this study, energy and exergy analyses are conducted to model novel integrated systems, combining thermochemical and sensible thermal energy storage (TES) systems, for building heating applications, and their performance is assessed for three various dead state temperatures of 8 °C, 9 °C and 10 °C. The present overall system consists of a floor heating system (FHS), System-A and System-B. The FHS is accommodated in the building floor and supported with a floor heating unit (FHU), a pump and an energy receiver unit (ERU). The System-A includes a thermochemical TES (TTES), a solar collector, a heat exchanger, a pump and a hot well of aquifer TES (ATES). Also, the components of System-B are a cold well of ATES and a HP unit. The system is designed to have the aquifer and thermochemical TES systems supplying the necessary heating for buildings. The FHS in the building can be operated with System-A (the TTES and hot well of ATES) and the System-B (the cold well of ATES and HP) to provide the same heating load in a more efficient manner. The maximum exergy efficiency is calculated for the hot well of ATES to be 88.78% at 8 °C dead state temperature, while the minimum one is obtained for the charging process of TTES as 21.69% among the TES systems considered. If all the system components are considered, the FHU has the highest exergy efficiency as 98.08% at a dead state temperature of 8 °C. Among the TES systems, the exergy efficiencies for the aquifer TES (ranging between 56.38% and 88.78%) are generally higher than the corresponding thermochemical TES efficiencies (ranging from 46.71% to 84.80%). Thus, the results show that the aquifer TES system is exergetically more efficient than the thermochemical TES system.

► Proposing a novel integrated system for building heating applications.
► Analyzing energy and exergy aspects of these systems.
► Evaluating energy and exergy efficiencies for performance assessment.
► Conducting parametric studies on the variations of efficiencies and irreversibilities.