Comprehensive energy, exergy, and economic analysis of the scenario of supplementing pumped thermal energy storage (PTES) with a concentrated photovoltaic thermal system

Abstract

The pumped thermal energy storage (PTES), which is designed to store electricity more cheaply, is one of the issues that have been discussed in recent years. In the PTES system, electrical energy is stored as hot water employing a heat pump, and when needed, it is converted back into electrical energy by using a heat engine. As a result of supporting the PTES system with a heat source, the performance coefficient of the heat pump is increased, thereby increasing the round-trip efficiency of the system. These systems are called thermally integrated PTES (TI-PTES). The novelty in this study was the thermal integration method applied to the PTES system. In the thermal integration scenarios were given in the literature, solar collectors, geothermal sources, district heating, and industrial waste gas were used as heat sources. In the presented study, the part of photovoltaic modules in the system where the electricity to be stored was produced, was designed as a photovoltaic thermal system (CPV/T), and the hot water obtained from the CPV/T units was used to support the PTES system thermally. The proposed PTES system (TI(CPV/T)-PTES) was extensively evaluated in terms of thermodynamics and economics, and thermodynamic analyzes were carried out for different values of the design parameters of the CPV/T and PTES system. Depending on the change in parameter values, the electricity storage capacity of the system changed between 0.85 MW and 9.1 MW, and the round-trip efficiency changed between 48% and 81%. As a result of thermo-economic calculations, the lowest levelized cost of storage (LCOS) for the TI(CPV/T)-PTES system was obtained as 0.278 $kWh(-1). The results of the thermo-economic analysis revealed that lower LCOS values can be obtained in regions with higher solar radiation values. In addition, the TI(CPV/T)-PTES system was compared with other energy storage systems economically and a lower LCOS value was obtained for certain parameter values compared to Li-ion and VRF battery technologies.