Design and Optimization of Non-Supercitical CO2 Thermal Power Cycle for “P2H2P” Energy Storage System

Most of the current research and development of CO2 cycles for power to heat - heat to power (P2H2P) energy storage systems are focused on the application of supercritical CO2 cycles, this work is different. The work is focused on alternative way of application of CO2 power cycle with standard (non-supercritical) cycle and modified industrial turboexpander as main working machine. In this paper is described power storage system with thermal energy accumulator for energy storage and non-supercritical CO2 power cycle for backward production of electricity. Briefly the design of thermal accumulator, option of acummulation media (molten salts or liquid metals) and its parameters is described. Especifically is discussed an option of accumulation temperature, which is key parameter for further design of following cycle. The main part of paper is focused on non-supercritical CO2 power cycle . There are discussed  possible configurations of cycle, design aspects of main parts of cycle and  possibilities of efficiency improvement as regenaration, intercooling and preheating. The option of main parameters and their limits for eficiency improvement of cycle is discussed. Finally are discussed an advantages and disadvantages of this CO2 cycle and its comparation with supercritical CO2 cycle and Rankine steam cycle as a cycle for backward production of electricity.