Dynamic study on the solar-driven methanol steam reforming process in novel heat-storage parabolic trough solar receiver-reactors

The heat-storage strategy is effective to reduce the impact of essential solar radiation fluctuations on solar-driven thermochemical hydrogen production systems. However, synergy strategies and regulation methods for heat-storage processes and endothermic reaction processes are still needed. In this paper, novel heat-storage structures of different encapsulated phase change material (EPCM) and catalyst multi-zone filling methods are proposed, to improve dynamic performance of parabolic trough solar receiver-reactors (PTSRRs) with methanol steam reforming reactions. A three-dimensional dynamic model was developed for the corresponding optical-thermal-chemical and heat-storage mixing process, with realistic porosity distributions of both catalyst particle and EPCM capsule packed bed zones. After validation, this model was applied to investigate the corresponding synergy and regulation between endothermic reaction zones and heat storage zones under different fluctuating solar conditions. Comprehensive comparisons were made on impacts of EPCM capsule size, material and cascading method on dynamic performance of PTSRRs. Under the optimal strategy from comparisons, the delay response time is increased by 3.4 times under the step disappeared solar radiation fluctuation, while the relative vibration amplitude of the methanol conversion rate is reduced by 68 % under the periodic solar radiation fluctuation. It could provide guidance for similar solar-driven thermochemical systems under fluctuating solar radiations.