Thermodynamic Performance Analysis of Medium and Deep Geothermal Energy Coaxial Tube Heat Exchanger Energy Storage and Power Generation System

This study presents a solution to address the efficiency and stability issues in geothermal energy power generation technology. A medium and deep geothermal energy coaxial tube heat exchanger energy storage and power generation system is proposed that integrates coaxial tube heat extraction technology with compressed air energy storage technology. By developing a thermodynamic model of the system, the evolution of key parameters and thermodynamic performance under typical operating conditions is analyzed, and the dynamic mechanism of geothermal recovery and extraction under different operating characteristics is examined. The results show that the operation of energy storage and generation system is divided into two phases: unstable cycle and stable cycle phase. In the unstable cycle phase, the heat extraction amount and expander output -work increase -with the number of cycles, -while the heat compensation amount and the system efficiency exhibit the opposite trend. Once a balance is reached bet-ween heat extraction, heat compensation and geothermal consumption reach equilibrium, the system enters a stable cycle from the 8th cycle onwards. In this phase, the system parameters remain constant regardless of the number of cycles, and the output of a single cycle is measured at 47 956. 7 kWh, -with a system efficiency as high as 63. 5%. To increase the geothermal recovery temperature, the compressor pressure ratio and the flow rate of -water for heat compensation can be adjusted. When the compressor pressure ratio is increased from 6 to 7 , the geotechnical temperature at a depth of 1 300 m and a radius of 0. 116 m is increased by 4. 3 °C , and flow rate of -water for heat compensation is increased from 4. 5 to 6 m*Vh, the temperature at the same site is increased by 6. 4 °C. This study provides a promising approach to improve the efficiency and stability of geothermal energy generation. © 2024 Xi'an Jiaotong University. All rights reserved.