A novel phase change heat storage for solar heating is proposed, where the phase change capsules (PCC) are piled up on the different sieve beds to form several porous heat storage layers, and the buoyancy force in solar chimney is utilized to drive the heating airflow in the system. Local thermal nonequilibrium (LTNE) is considered to be in the porous beds, so the heat transfer and flow in the porous thermal storage layer are analyzed based on the double energy equations and Brinkman-Forchheimer extended Darcy model, and the k-epsilon turbulent model combined with the above equations are also employed to study the effects of materials, porosity and particle size of PCC in the porous thermal storage as well as the characteristics of flow channel on the efficient of thermal storage. The simulations accord with the published experimental results. About 7%-25% higher thermal storage time occurs in the layer of PCC than that of Tuff and Basalt. The porosity and particle size in the porous layer have an impact on the thermal storage, and the better performance of thermal storage can be achieved at the optimized ratio of the width of flow channel to bed thickness in the system. (C) 2020 Elsevier Ltd. All rights reserved.