Recent Advancements in Materials and Systems for Thermal Energy Storage by Andrea Frazzica & Luisa F. Cabeza

Author:Andrea Frazzica & Luisa F. Cabeza
Language: eng
Format: epub
ISBN: 9783319966403
Publisher: Springer International Publishing

2 Thermochemical Characterization of TCM Reactor at Laboratory Scale

TCM has to be evaluated by a packed bed reactor at laboratory scale in terms of energy density, thermal power and durability. Gas–solid reaction system is one of major choices for TCM. Powder state of TCM is not suitable for a practical reactor because powder state induces material scattering, bed material sintering and channelling and gas diffusion resistance increase, bed thermal conductivity decrease, and finally packed bed thermal performance degradation. Then, some shaped bulk materials of TCM in such as pellet, tablet and block figures are used in a bed reactor [13]. The bulk material reactor bed is expected to have high material density, high reaction gas diffusivity and high thermal conductivity for achieving high-performance TCM reactor with high energy density and high thermal power. Practical reactor requires high thermal power TCM to enhance the performance of the reactor and reduce its cost. Material durability of bulk TCM is a key performance for practical application where many reaction cycles are performed. Material analysis of the bulk TCM during cycle operation is required previously for TCM reactor evaluation. In general, TCM has intrinsic property of volume change during gas–solid reaction, which could affect contact thermal resistance between the material and heat exchanger. Thus, mechanical properties (e.g. stress distribution which affect sintering and breakage of pelletized bulk TCM) in bed reactor should be also investigated.

Experimental of TCM bed reactors in laboratory scale is important to have practical information of a design of a thermochemical TES system. Numerical analysis of the bed reactor by introducing a numerical model is useful for validation of thermal storage/output processes in the bed, and establishment of efficient thermochemical energy storage system with shorter period and lower cost development. To establish a numerical model, we have to consider coupled governing equations of heat transfer, mass transport and chemical reaction. Based on the numerical analysis we can calculate TES performances (e.g. reaction rate per unit volume or mass of the reactor) of an up-scaled TCM reactor. A proper numerical model also contributes to extract a limiting step during thermal storage/output process and the model could be used to estimate required transport properties of TCM as well as reactor design for an application.

An experimental study of thermochemical characterization of a TCM for CaO/Ca(OH)2/H2O reaction system (Eq. 8.4) at laboratory-scale packed bed reactor is shown in Fig. 8.3 as an experimental example.

Fig. 8.3Schematic diagram of a laboratory-scale reactor for thermochemical energy storage

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