Non-Saturated 3E (Energy, Exergy, and Economic) Analysis of Carnot Battery Systems Based on Organic Rankine Cycle

Abstract

Artificial activities, environmental factors, and industrial production lead to periodic fluctuations in electricity consumption, necessitating peak-shaving measures to ensure efficient and stable operation of the power grid. The Carnot battery system represents an effective solution due to its high efficiency and convenience. In this paper, we propose a novel Carnot battery system based on a dual-function unit and establish thermodynamic and economic models. This paper proposed a simple reversible heat pump-organic Rankine cycle Carnot battery system, where a compression and expansion dual-function unit was developed to simplify the system and reduce investment costs. Subsequently, considering the unsaturated operating conditions that occur during practical operation, a comprehensive performance analysis of the system is conducted by varying pressure and temperature parameters. Afterward, an exergy analysis is performed on the proposed system to determine the exergy losses of its components for subsequent optimization. The results indicate that pressure drop has a detrimental effect on the system. When the pressure drop is 15 kPa, the system achieves a power-to-power ratio (P2P), levelized cost of storage (LCOS), and exergy efficiency of 27.57%, 0.66 $/kW∙h, and 62.8%. However, this also leads to increased exergy losses in the evaporator, resulting in decreased exergy efficiency. The evaporator exhibits the highest exergy loss, with a maximum loss of 21.16 kW among all components. Undercharging mode, the condenser shows the lowest exergy efficiency of 64.43%.