A computational study into the charging of an agitated fluidised bed thermochemical energy storage system

Waste heat of medium to high temperatures (150-500C) is often dissipated directly to the atmosphere or used in low-temperature applications. However, much of this waste heat could be used in industrial, process and renewable energy applications. Sensible and phase change materials storage are generally, not suitable for these temperature ranges, but thermochemical energy storage (TCES) can store and release this heat at high temperatures, sufficient to drive industrial and process applications. TCES stores the energy in the form of chemical bonds, which are released with exothermal reactions. This enables heat to be stored without degradation until a reaction is activated and so can store the energy over long periods, allowing short-term and long-term storage. An agitated fluidised bed thermochemical reactor is being developed to optimise the system and create an efficient and effective storage system. To gain a better understanding of the interaction between the fluidised bed, agitation and thermochemical reaction, computational fluid dynamics (CFD) simulations were developed. The process involved the integration of a multiphase gas-solid fluidisation model, a heterogeneous reaction model and a sliding mesh model. Key findings included successfully simulating water vapour dehydration, the change in volume fractions of the products and reactants as the simulations progressed and enabling us to gain an insight into the hydrodynamics of agitation, chemical reaction and fluidisation.