Performance analysis of Carnot battery and its coupled seawater desalination system based on Kalina cycle discharge process

Large scale renewable energy power supply needs auxiliary support of energy storage technology. To discover the potential of Kalina cycle as the power cycle in the Carnot Battery energy storage system, this study presents and compares two systems: the Kalina-Carnot System (KCDS) and the Kalina-Carnot–MED Synergistic Discharge and Desalination System (KCMED-SDDS). The KCDS incorporates a heat pump cycle, a Kalina-based power generation process, and a sensible heat-based thermal energy storage unit to achieve electricity–heat–electricity conversion. This research utilizes the 5E evaluation framework—comprising energy, exergy, economic, environmental, and energy level analyses—to comprehensively assess the system's performance, while optimal operating parameters are identified via sensitivity analysis and multi-objective optimization. The optimized KCDS achieves a round-trip efficiency of 72.65 %, a volumetric energy density of 2.99 kWh/m3, a levelized cost of storage of 0.34$/kWh, and a payback period for KCMED-SDDS of 2.86 years. Its exergy efficiency is 53.37 %, and its environmental sustainability index is 0.18. The energy level analysis reveals that the heat pump cycle has an energy level difference of 0.6442, the Kalina cycle 0.5040, and the system after coupling 0.5948. Multi-dimensional evaluation methods, including energy level analysis, are employed to comprehensively assess the proposed system and identify the optimal solution via multi-objective optimization. The KCDS demonstrates broad adaptability, requiring no specific terrain, while the KCMED-SDDS is tailored for coastal or island regions due to its integration with multi-effect distillation. This approach offers a novel pathway for optimizing the RCB system.