Numerical and experimental studies of a novel compact sandwich-type plate reactor for thermochemical energy storage

In this work, a novel compact sandwich-type plate reactor (CSPR) for thermochemical energy storage (TCES) with Ca(OH)₂/CaO is proposed, where the essential unit is symmetrically comprised of steam channel in the center, orderly sandwiched by metal gauzes, reaction cavities, plates and heat transfer channels at both sides. Firstly, the flow-heat-reaction multi-field coupled modelling is conducted to comparatively investigate the flat, baffled and dimpled plates, where the dimpled plate (DP) stands out. Then, the entire CSPR comprised of three essential units with DPs is modelled to numerically predict its comprehensive performance and characteristics. Afterwards, the prototype of CSPR is manufactured based on the above numerical studies and experimentally evaluated on our exothermic and endothermic cycling performance test bench with loading of 1.667 kg of Ca(OH)₂ pellets. The experimental data confirm that the charging stage takes 330 min with the final conversion up to 97.74 %, while the discharging stage takes 200 min with the maximal heat transfer fluid (HTF) output temperature reaching 385 ℃ and the duration for the HTF output temperature above 350 ℃ lasting for 130 min. Based on energy balance analysis, the energy storage efficiency for charging stage is 74.92 % and the round-trip energy efficiency for cycle is 60.24 % (including 2 h of buffering period) without heat recovery of product steam. Technically, these efficiencies can be respectively promoted to be 76.35 % and 71.59 % with heat recovery. The numerical simulation and experimental data are found to be mutually verified. We hope this work can provide a novel insight of reactor design for development of TCES technology.