Experimental study of discharge performance of pumped thermal energy storage system based on organic Rankine cycle

Pumped thermal energy storage system based on organic Rankine cycle operates at temperatures below 150 °C and can utilize heat sources under 100 °C to improve efficiency, demonstrating significant potential for widespread applications. To analyze the dynamic operation of the system, a 1.5 kW scale experimental platform was developed, incorporating a thermal energy storage system that utilizes both sensible and latent heat storage materials. This study investigates the heat transfer capacity of thermal storage materials, the variations in operating parameters and comprehensive performance of the system during the discharge process. The discharge process was experimentally tested under different conditions, including sensible thermal storage material temperatures, organic Rankine cycle working fluid flow rates and condensation temperatures. Based on the primary heat source transition of organic Rankine cycle, the discharge process can be divided into sensible thermal storage material dominant stage, transition stage and latent thermal storage material dominant stage. The generator power decreases gradually at sensible thermal storage material dominant stage and transition stage, but drops sharply at latent thermal storage material dominant stage, primarily due to the degradation of thermal energy storage system. The experimental results confirm the practical feasibility of the theoretical concept of pumped thermal energy storage system, highlighting the importance of balancing thermal storage system temperature and organic Rankine cycle operating conditions to maximize the comprehensive performance of the system. These findings provide valuable insights and guidance for the design and optimal operation of pumped thermal energy storage system during the discharge process.