Diabatic Liquid Air Energy Storage Systems

Abstract Long-Duration Energy Storage (LDES) can align the large and accelerating deployment of variable renewable wind and solar generation resources with the needs of Load Serving Entities (LSE) to reliably meet demand for low-carbon power. Using turbomachinery and heat transfer equipment, Liquid Air Energy Storage (LAES) can provide energy at scales comparable or larger than Pumped Storage Hydro. There are two general approaches to LAES discharge: adiabatic and diabatic. In either approach the stored liquid air is pressurized, heated, and then expanded through turbomachinery to deliver useful work. Adiabatic approaches typically capture and store heat of compression during charging for use during discharging. High pressure ratio is favored during expansion and typically results in the discharge of cold air, which is used to cool a cold storage medium for use during a subsequent charging phase. The adiabatic efficiency improvements come at the expense of additional capital expense for the hot and cold storage, in addition to the cryogenic storage, and operational constraints due to the need to match the available hot stored energy during discharging and cold stored energy during charging. The diabatic LAES approach uses exhaust heat from a fired turbine to regasify pressurized liquid air, which after expansion is exhausted to atmosphere at near-ambient temperature. The diabatic approach dispenses with hot and cold storage, which simplifies the design and operation of the cryogenic equipment. Importantly, the diabatic approach reduces the specific discharge air consumption, which in turn reduces the size and capital cost of the cryogenic charging system. This paper compares several approaches to diabatic LAES discharge. The Liquid Air Combined Cycle (LACC), described previously by the authors, is comprised of a gas turbine generator, an air turbine generator, and an Organic Rankine Cycle (ORC), which rejects heat absorbed from the gas turbine exhaust gas to regasify the liquid air. In Liquid Air Power & Storage (LAPS), the compressor section of the gas turbine is removed, and regasified air is introduced to a combustor at about the same pressure and temperature as the gas turbine. Various LAPS arrangements are presented and compared based on power output, efficiency, specific discharge air consumption.