Performance of zeolite- and PCM-based cascade hybrid heat accumulator with cast thermal conductivity enhancers

The study tackles the issue of facilitating heat transfer in a newly designed versatile thermal energy storage (TES) unit that uses waste or renewable energy. The novel hybrid heat storage unit, consisting of a phase change material (paraffin) and zeolite (4A) deposits to be used for short-term or long-term storage, was constructed and characterised. Cast aluminium heat transfer enhancers were designed, manufactured by 3D printing with in-vestment casting and then applied in order to shorten the charging time and to equalise the temperature dis-tribution in the accumulator. This approach ensured both the exceptional flexibility of the process and the easy optimisation of the heat transporting surfaces' shape and weight, resulting in improved thermal behaviour without severely limiting the volume of the storage medium. Honeycomb-based perforated inserts were chosen as the most effective heat transfer geometries for both deposits. The performance of the hybrid heat storage unit was evaluated during an analysis of cyclic work's. The theoretical values of heat efficiency and energy storage capacity were calculated as 65.7% and 2.63 kWh, respectively (2.29 kWh for the zeolite chamber and 0.34 kWh for the PCM one). Future work may deal with adjusting the connection between chambers (e.g. limiting heat losses).