Modification of Fine-Grained Powder to Facilitate a Moving Reaction Bed for Thermochemical Energy Storage

Abstract

Dispatchable power generation is one important advantage of concentrated solar power (CSP) plants, if high-performance thermal energy storages are included. Thermochemical energy storages can make a decisive contribution because of their low material cost, high energy densities and heat transformation possibility. For an appropriate temperature range (~500°C) the reversible gas-solid reaction of calcium oxide with water vapor to calcium hydroxide is investigated: CaO(s) + H2O(g) ⇌ Ca(OH)2 + ΔHR In order to release a constant power level over a long period of time (night cycle), it is necessary to separate the power from the capacity of the storage unit. For this purpose, the gravity-induced flow of the reaction material through small reactor geometry is highly promising. However, due to its cohesive characteristic, the material tends to agglomerate during cycling and shows poor flow behavior leading to plugging within the reactor. Approaches of the bulk industries have demonstrated improvements of flowability of organic materials by adding nanoparticles to bulk material in order to decrease the Van-der-Waals forces. However, this enhancement is not established for high temperatures, reacting conditions and inorganic materials. In this contribution, the approach to optimize the flow behavior of thermochemical storage material and the prevention of agglomeration by addition of nanomaterial is presented. Furthermore, miscellaneous advantages of the gravity-induced moving bed reactor are given.