A novel cryogenic air separation unit with energy storage: Recovering waste heat and reusing storage media

Abstract

The combination of the air separation unit and cryogenic energy storage enhances system efficiency; however, there are still significant irreversible losses in the energy conversion process and high investment costs. This paper explored the potential for deep integration of these two process and proposed a novel air separation with liquid nitrogen energy storage process recovering waste heat and reusing storage media process. The proposed process improved the liquefaction and power generation processes and recovered the compression heat for air purification processes. Taking an actual plant as a research case, the integrated system was simulated using Aspen Plus software. The round-trip efficiency, exergy efficiency, and power generation of the proposed process are 0.537, 0.722, and 10.52 MWh respectively, which are 6.2 %, 20.9 %, and 68.3 % higher than those of conventional process. By reusing storage nitrogen and recovering compression heat, the proposed process reduces the initial investment cost by half while achieving a dynamic payback period of 6 years with a levelized cost of electricity at $82.8/MWh. Furthermore, it is worth noting that media reuse operations have a greater impact on economy when off-peak electricity cost is low; whereas utilization of compression heat has a greater impact when off-peak electricity cost is high.