Optimal design and operation of a hybrid renewable micro-grid with decoupled LAES

Climate changes and energy crisis have drawn considerable attention across the world, which called upon the urgency for new energy provision and carbon emission reduction globally. Hybrid renewable energy system (HRES) integrated with LAES is a good option to achieve the de-carbonization of energy sector. This study focuses on exploring the value of LAES in a hybrid renewable micro-grid, in which the decoupled off-design LAES energy storage model was developed and inserted into the system MILP framework, which is applicable for discussing the optimal E/P ratio of LAES, digging the value streams out and optimally sizing the different system components and LAES units separately to achieve good economics and environment benefits. The simulation results indicated three important aspects. Firstly, for a specific micro-grid equipped with LAES, there exist the optimal charge/discharge E/P ratio of LAES, corresponding to the optimal sizes of liquefaction unit, power recovery unit and storage tank when providing different services. Secondly, if wind penetration reaches about 50%, LAES annual benefits can reach about 90% of its annual investment cost when six explicit value streams are stacked, including the time shifting, renewable firming, peak shaving, flexibility and reserve value, as well as the waste heat utilization, which is totally 8.2% higher than that of battery storage at the same investment cost. Thirdly, compared with the LAES cost reduction and large electricity price difference, more renewable penetration is the major driving force to increase the value and attractiveness of LAES, the optimal charge/discharge E/P ratio and storage tank size is 27/14 h and 608 t when there is 75% of wind power, resulting in about 60% of carbon emission reduction on 2016 level for a micro-grid.