Storage system for distributed-energy generation using liquid air combined with liquefied natural gas

Abstract

This study proposed a storage-generation system for a distributed-energy generation using liquid air combined with liquefied natural gas (LNG). The system comprised three main sites: the renewable-electricity sources (RESs), liquid-air energy storage (LAES), and natural-gas combustion. The low-priced off-peak electricity generated by the RESs was supplied to the LAES. The supplied electricity and previously stored cold energies liquefied the air. At the on-peak time, the liquid air and LNG were pressurized, re-gasified, and burnt immediately after mixing to generate the high-priced electricity while their cold energy was stored in thermal media. The proposed system was evaluated in terms of the thermodynamic, environmental, and economic performances. Its round-trip and storage efficiencies were 64.2% and 73.4%, respectively. The exergy efficiency of the storage-site, the generation-site, and the system was 70.2%, 75.1%, and 62.1%, respectively. The levelized cost of energy (LCOE) ranged from 142.5 to 190.0 $/MWh depending on the sizes and the storage time. The proposed system was compared to the diabatic compressed air-energy storage (CAES) systems and the adiabatic LAES system. The sensitivity analyses compared the systems for the fixed power output and storage time, and for the option to use natural gas. The proposed system showed better storage and round-trip efficiencies than those of comparison systems. Its LCOE was competitive with those of the compared systems except for the under-ground CAES system. The proposed system was an economic and viable option considering the geographical limitations and the environment impacts of the CAES system.