Thermo-economic assessment of a thermally integrated pumped thermal energy storage (TI-PTES) system combined with an absorption refrigeration cycle driven by low-grade heat source

Abstract

The pumped thermal energy storage system (PTES), which offers cheaper storage of electrical energy, has been a widely discussed issue in the literature recently. Unlike the literature studies, in this study, an absorption refrigeration cycle (ARC) was integrated into the PTES system assisted by waste heat and it was aimed to increase power generation by operating the ORC at lower condenser evaporation pressures. Thermodynamic analyses were carried out for the parameters of evaporation temperature of the heat pump evaporator, storage temperature, cooling water temperature, operating mass flow rate of ARC, compressor, and turbine efficiency. Also, the addition of ARC to the system was evaluated in terms of thermo-economics. For different parameter values, with the proposed thermally integrated PTES system, an increase of 15.3% to 41.5% was achieved in the electrical energy supplied to the grid during the discharge process, and the round-trip efficiency of the system reached 142%. Although the addition of ARC to the system caused an increase in the total investment cost, it reduced the levelized cost of storage (LCOS) to 0.242 $/kWh. The results revealed that the proposed system has a high potential to be applied to PTES technology if there is sufficient waste heat energy.