Preliminary assessment of waste heat recovery solution (ORC) to enhance the performance of Liquid Air Energy Storage system

Liquid Air Energy Storage (LAES) is a novel energy storage system that stocks up energy by means of air liquefaction and recovers the cryogenic energy when required. The performance of LAES is actually limited both by the inefficiencies of liquefaction and discharge section leading to lower value of round trip efficiency compared to other energy storage solutions. This work investigates the thermodynamic feasibility of an integrated energy system consisting of a LAES system and Organic Rankine Cycle (ORC) in order to recover the waste heat released by the compression phase. To further improve the round trip efficiency of LAES, different integrated LAES-ORC system configurations have been modelled by means of the numerical software EES-Engineering Equation Solver v.10, which allows to compute the thermo-physical properties of the working fluids throughout the whole cycles. The LAES-ORC integrated systems are compared in terms of different performance indices such electric power output, round trip efficiency of stand-alone and integrated systems and recover efficiency of ORC. Moreover, since the potential benefits of waste heat recovery by means of ORC introduces a new capital and operative cost, an economic analysis has been carried out in order to determine the impact of ORC introduction in LAES economy. The results show that a tight integration between LAES and ORC allows to significantly improve the round efficiency (up to 20%) and reduce the pay-back period of stand-alone LAES as high as 6 %