Computational analysis of heat transfer in a fluidised bed thermochemical energy storage reactor

With the rise in necessity for eliminating fossil fuel use, the application of renewable energy technology has become essential. However, the primary concern with regards to renewable energy dependence is its intermittency and reliance on uncontrollable weather conditions; this introduces the international importance of energy storage technologies. An energy storage technology of interest is thermochemical energy storage (TCES) due to its unique capability to store energy with near-zero losses, making it potentially capable for inter-seasonal storage. The primary aim of this research is to observe the effects of various boundary conditions on a simulated fluidised bed TCES reactor, which will ultimately allow for the development of an experimental rig based on this model. The application of existing research findings and material characterisation techniques has allowed for the proposition of a design concept for a novel fluidised bed TCES system. The fluidised bed TCES reactor has been modelled using computational fluid dynamics software ANSYS Fluent, with the effects on model performance of inlet velocity, fluidised bed particle diameter and inlet temperature being evaluated. The model consists of a cylindrical reactor containing calcium oxide particles; these undertake an exothermic hydration reaction to form calcium hydroxide when steam-saturated air is used to fluidise the bed. A helical pipe is also inside the reactor and is used as a working heat exchanger, with liquid water being used as a heat transfer fluid. The simulation concluded that increasing fluidised bed particle diameter would not be beneficial for further development due to the prolonged calcium oxide depletion time this causes; increasing the inlet temperature of the steam-saturated air proved advantageous due to an increased rate of reaction. However, insufficient conclusion could not be drawn on the ideal heat transfer fluid inlet velocity and therefore requires further investigation.