Energy integration of LNG cold energy power generation and liquefied air energy storage: Process design, optimization and analysis

Liquefied natural gas (LNG) has a large amount of cold energy, and recovering LNG cold energy can not only reduce dependence on traditional energy and promote sustainable energy development but also reduce pollutant emissions, and liquified air energy storage (LAES) is an advanced energy storage technology, but its electrical round trip efficiency (ERTE) is low due to the lack of sufficient cold energy. Thus, to improve the efficiency and benefit of LNG cold energy utilization and the ERTE of LAES, an integrated power generation system combining organic Rankine cycle (ORC) with LAES driven by LNG cold energy (denoted as LNG-ORC-LAES) is proposed in this paper. The system operates in two modes, utilizing LNG cold energy at peak and off-peak times. The system is optimized under different peak electricity price scenarios by using multi-objective optimizations to achieve better performance. The LINMAP (Linear Programming Technique for Multidimensional Analysis of Preference) and TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) methods can dimensionless the optimization results and calculate the distance between each point on the optimal Pareto surfaces and the ideal point, so the two decision methods are used to screen the optimization results. The exergy efficiency and specific net output power of existing similar systems are similar to 70.31 % and similar to 94.75 kJ/kgLNG, but they can achieve 72.26 % and 124.43 kJ/kgLNG respectively after multi-objective optimization in the proposed system, and the high net present value (NPV) is obtained, the optimized system exhibits superior performance than other similar systems. The energy and exergy analysis demonstrate that the LNG cold energy utilization ratio can reach 81.96 % under optimal working conditions, the LNG cold exergy can be fully utilized by LAES. The results show that the proposed system has industrial and economic feasibility, which provides a design concept with practical significance for energy development.