Analysis of an energy storage system using reversible calcium hydroxide in fluidised-bed reactors

Abstract

• Conceptual study of new CSP-TCES layouts based on calcium hydroxide reaction. • Single fluidised bed reactor designs simplify plant integration and reduce costs. • Design and operation challenges with different requirements in charge and discharge. • Novel insights for reactor design and thermal integration of the systems. • Competitive round-trip efficiency values of 68% and LCOE values of 67–83 $/MWhe. The widespread use of renewable energy requires the support of high-capacity energy storage systems. This work proposes a thermochemical energy storage system for concentrated solar power plants based on the reversible hydration/dehydration process of the calcium hydroxide. It is a single fluidised bed reactor concept with alternating dehydration-hydration processes, charging and discharging alternating reactions, with superheated steam as fluidising agent. The system has been modelled using Aspen Plus™, including equilibrium data and hydrodynamic performance of the reactor. The model has been used to evaluate the effect of different parameters of the reactor, such as geometry, average particle size, or inlet streams conditions, on the performance of the reactor and the system. The thermal integration of the system was optimised using pinch analysis. For the proposed layouts, round-trip efficiencies values of 68 % are obtained. The economic analyses show specific investment costs between 4170 $/kWe and 3250 $/kWe for plants in the range of 31 MW to 45 MW, which are competitive with those expected for plants with storage of molten salts in this power range. LCOE values between 67 $/MWh and 83 $/MWh were obtained. The analyses show how these values highly depend on the fresh material replacement requirements related to the deactivation of the material and operational strategies. The results show the interest in further developments of this concept for concentrated solar power plants.