Techno-economic analysis of a new thermal storage operation strategy for a solar aided liquid air energy storage system

Abstract

The SA-LAES system is an economical and efficient energy storage solution that combines solar energy with LAES. However, the inherent instability of solar energy can result in uncertainty regarding heat storage, thereby compromising the stability of the energy storage system. The development of more economical, efficient, and stable strategies for the SA-LAES system represents a challenging task. The present study puts forward a novel thermal storage operation scheme (Strategy 2) for SA-LAES systems integrated with electric heating during valley periods, thereby achieving long-term stable operation of the energy storage system via the alternating utilization of two full molten salt tanks and one empty molten salt tank. Theoretical and case studies are conducted based on thermodynamic and economical technical indicators, and detailed comparisons are made with the traditional strategy (Strategy 1) of only changing the solar multiple and capacity. The results show the exergy destruction of Strategy 1 mainly occurs in air turbines under off-design operating conditions. The exergy destruction of Strategy 2 is mainly in the electric heater part. The single-day analysis found that the new strategy has a more significant advantage in terms of exergy efficiency than Strategy 1 when the direct normal irradiance (DNI) is below 650 W/m2. In the case study, the levelized cost of energy (LCOE) values for Nanning, Beijing, and Hami regions in Strategy 2 are 0.118 $/kWh, 0.077 $/kWh, and 0.062 $/kWh, respectively. The LCOE values of Strategy 2 are decreased by 10.97 %, 27.49 %, and 3.40 % compared to Strategy 1, respectively. The payback periods for investments in the Beijing and Hami regions have decreased by 67.63 % and 16.41 %, respectively. The research presented in this article provides an economical, efficient, and stable operating strategy for thermal storage in the SA-LAES system.