Modelling Of an Encapsulated Molten Salt Thermal Storage System

摘要

Thermal storage is both a strong advantage for solar thermal power plants and a component with high improvement potential. The research institute solar energy and new energies (IRESEN) is currently developing a pilot solar power plant using an Organic Rankine cycle in the framework of the recently launched "GREEN ENERGY PARK" research platform, this plant shall operate at relatively low temperatures in comparison with large scale commercial plants, and then shall require a well suited storage system in order to improve economic efficiency and enable night time production. A study based on the cost and storage capacity has led to the choice of two systems: sensible heat storage in a rock (quartzite) packed bed and latent heat storage on encapsulated molten salt. A model has subsequently been developed in order to enable the assessment of both systems' performances and in particular for the encapsulated salt solution for which a hexagonal close packing with spherical capsules was selected taking inspiration from hexagonal crystal structures. This model calculates the heat exchange between the heat transfer fluid HTF and the storage medium by computing the dimensionless numbers and HTF flow on each horizontal plane following flow direction and for a whole discharge duration. The results enable to tell whether the output of the encapsulated salt system is high enough to justify its cost. It also allows choosing the best design, sizing and the best configuration to optimize the systems' output to the maximum.