Energy, Exergy, Economic, Exergoeconomic, and Exergoenvironmental (5E) Analyses and Optimization of a Novel Three‐Stage Cascade System Based on Liquefied Natural Gas Cold Energy

Abstract

Energy conservation and emission reduction are inevitable strategies for alleviating energy shortages and environmental pollution, which can be achieved by improving the energy utilization efficiency and using cleaner energy. Waste heat recovery (WHR) is an effective strategy to improve the energy utilization efficiency of a system. [1] A common WHR approach involves the addition of a bottoming cycle, [2] such as the Rankine (RC), flash, Kalina (KC), Stirling, and Brayton cycles, with each bottoming cycle exhibiting a different WHR potential for various temperature ranges. In this regard, waste heat is typically categorized into low-(<230 °C), medium-(230-650 °C), and high-temperature residual heat (>650 °C). [3] Varma et al. [4] performed a comparative study of the performance of the organic Rankine cycle (ORC), organic flash cycle (OFC), and KC for recovering low-grade waste heat and found that the OFC, ORC, and KC with a specific temperature and solution concentration exhibited the highest power generation, efficiency, and power output among the investigated cycles, respectively. Zhang et al. [5] compared the steam Rankine cycle (SRC), ORC, and steam-organic Rankine cycle (S-ORC) and concluded that the ORC exhibited optimal thermodynamic performance at residual heat temperatures of 150-210 °C, whereas the S-ORC demonstrated superior performance at 210-350 °C. Liu et al. [6] compared the thermodynamic performance of the supercritical CO 2 Brayton cycle (S-CO 2 ) and SRC at high temperatures and found that the performance of S-CO 2 was superior to that of the SRC. Moreover, the performance parameters of the equipment were analyzed from the perspective of energy conservation. The aforementioned scholars compared the performance of the ORC, OFC, KC, SRC, S-ORC, and S-CO 2 cycles for recovering waste heat of different grades. These studies highlight the suitability of the S-CO 2 and ORC for high-temperature and low-grade WHR, respectively.China has prioritized the achievement of carbon peak and carbon neutrality to mitigate the severe problem of climate change as an environmental protection strategy and as an important basis for national economic competitiveness in the future. Therefore, the use of CO 2 as a working fluid must be reassessed. CO 2 has recently been shown to exhibit tremendous potential as