Parametric analysis of a hybrid liquid air and thermochemical energy storage system

S. Wu, C. Zhou, E. Doroodchi, B. Moghtaderi
The University of Newcastle,
Australia

Keywords: energy storage, thermochemical energy storage, liquid air energy storage, metal oxide, renewable energy

Summary:

As a utility-scale energy storage technology, the hybrid liquid air and thermochemical energy storage system has been shown to be superior to both the standalone liquid air and standalone thermochemical energy storage systems in multiple aspects, such as round-trip efficiency, energy storage density, and environmental impact. In the current work, a parametric analysis of the hybrid system is performed to identify the most influential operating parameters for the new technology. The results are then used for the optimization of the system. Specifically, the examined operating parameters include operating pressures, reactor temperatures, reactivity of metal oxide, compressors configuration, ambient temperature, and inter-cooling temperature. The storage performance of the hybrid storage system is studied in a thermodynamic model developed using Aspen Plus v10. According to the results, the discharge pressure of the liquid air storage tank is found to be the most critical factor for achieving a high energy storage density. An increase of 40 bar of the discharging pressure, for instance, leads to an increase of 20% of the energy storage density from 32.9 kWh/m3 to 39.5 kWh/m3. The oxidation reactor temperature, on the other hand, is found to be a dominant factor affecting the round-trip efficiency and can boost the efficiency from 45.5% to 48.1% as the oxidation reactor temperature increases from 775°C to 900°C. A decrease of the reactivity of metal oxide by 50% leads to a sizable drop of oxygen production from about 220 kg/MWh to 170 kg/MWh. The minimum levelised cost of electricity is found to be achieved at a discharging pressure of 70 bar, an oxidation reactor temperature of 900°C, a 7-stage compressor, a reactivity of metal oxide of 100%, and an intercooling temperature of 20°C.