Configuration mapping of thermally integrated pumped thermal energy storage system

Abstract

The thermally integrated pumped thermal energy storage possesses the advantages of not being limited by geographical locations and small installation footprint as compared to other large-scale physical energy storage technologies. To promote the power-to-power efficiency of the thermally integrated PTES system, twenty-five kinds of pumped thermal energy storage systems are proposed and evaluated based on thermodynamics and economics. Since the power-to-power efficiency varies much with different system configurations and operating conditions, this paper focuses on developing a kind of configuration selection maps with different thermal storage methods, which can be employed as an effective and rapid decision-supporting tool for a general design of the thermally integrated pumped thermal energy storage system. Furthermore, the energy storage density and the levelized cost of storage of the mapping selected pumped thermal energy storage systems are also investigated. The results indicate that the energy storage density of the PTES with sensible thermal storage is usually lower than 5 kWh/m3, and increases up to 27.7 kWh/m3 when utilizes erythritol as the latent thermal storage material. Whereas the levelized cost of storage is more sensitive to the system configuration than the thermal storage methods, and ranges from 0.35 $/kWh to 0.55 $/kWh under different conditions. In terms of these performance indicators, the PTES system with latent thermal storage employing the double-stage heat pump cycle with flash tank or economizer as charging process and the single stage organic Rankine cycle with waste heat heater as discharging process would be an excellent option.