Operational Characteristics Analysis And Parameter Matching Optimization Of Liquefied Air Energy Storage System

Energy storage technology can transform unstable renewable energy power generation into continuous and stable power output,which is one of the key technologies for large-scale application of renewable energy.Liquefied Air Energy Storage(LAES)is a high-capacity,low-cost,and easy-to-build energy storage technology.In order to solve the problem of low efficiency of liquefied air energy storage,this paper studies the operation characteristics analysis and parameter matching optimization of liquefied air energy storage system.The paper constructs a conventional LAES system with two-stage compression and two-stage expansion by references of relative documents.The system is divided into two stages: liquefied air storage and air release power generation.Applied the thermodynamic theory,the mathematical model of the system was established and programmed using MATLAB and REFPROP software.The effects of compressor outlet pressure,cryogenic pump outlet pressure,heat exchanger effectiveness and temperature and pressure before air throttling on system performance were calculated and analyzed.It was found that the cycle efficiency of the conventional LAES system was between 40% and 50%.Considering that partial of the heat of compression is not fully utilized in the liquefied air storage stage,this paper constructs a three-stage compression,a three-stage expansion,and a coupled Organic Rankine Cycle(ORC)LAES system to further improve cycle efficiency.The results show that the LAES system coupled with ORC has a cycle efficiency of 50%-65% at lower compressor outlet pressure and cold box pinch-point,higher cryogenic pump outlet pressure and heat exchanger effectiveness,and a higher exergy efficiency at the stage of air energy release power generation.The effects of compressor outlet pressure,cryogenic pump outlet pressure and heat exchanger effectiveness on cycle efficiency of two LAES systems were studied.Compared with the conventional LAES system,the cycle efficiency of the LAES system coupled with ORC is also significantly improved under variable operating conditions,and the optimal cycle efficiency of the LAES system coupled with ORC is 17.77% higher than that of the conventional LAES system.In order to realize the optimal operation of the LAES system coupled with ORC,the NAGS-II algorithm is used to optimize the parameter matching.The Pareto optimal frontier curve is drawn and the relative optimal scheme is given according to the TOPSIS optimization method.The results show that the cycle efficiency,the exergy efficiency of the air release power generation stage and the closeness of the relative optimal scheme are 62.75%,87.23% and 66.51% respectively when the cycle efficiency and the exergy efficiency of the air release power generation stage are taken as the objective functions.When the cycle efficiency and the ratio of liquid air are the objective functions,the cycle efficiency is 65.73%,the ratio of liquid air is 80.51%,and the closeness is 87.12% in the relative optimal scheme.