Analysis of 5E (energy, exergy, energy level, exergoeconomics, and exergetic sustainability) for a transcritical CO₂ energy storage system integrated with ORC and solar energy

Facing growing energy demand and worsening environmental problems, the intermittency of renewable energy hinders its large-scale application, boosting the need for grid peak regulation and efficient energy distribution. This paper proposes an energy storage system integrating a transcritical carbon dioxide cycle, an Organic Rankine Cycle (ORC), and solar energy, and analyzes its thermodynamics, exergy, exergoeconomics, energy level, and exergy sustainability.Results show that Compressor 1's inlet temperature and pressure have a relatively obvious positive impact on the system's exergy efficiency and unit exergy cost: exergy efficiency increases by 4.02 %, while unit exergy cost decreases by 4.21 %. Exergoeconomic analysis reveals that expanders, high- and low-pressure gas storage tanks mainly incur equipment investment costs, whereas heat exchangers, cold and thermal storage units mainly cost from unavoidable exergy destruction during operation. Energy level and level difference calculations under standard conditions clarify energy flow and driving force magnitude. Additionally, higher ambient temperature benefits exergy environmental sustainability.Multi-objective optimization (maximizing storage efficiency, minimizing total product unit cost) yields an optimal Pareto frontier point: 78.92 % storage efficiency and 65.802 $/GJ total product unit cost.