Thermal decomposition kinetic of salt hydrates for heat storage systems Armand Fopah Lele a , Frédéric Kuznik b,c , Holger U. Rammelberg a , Thomas Schmidt a,⇑ , Wolfgang K.L. Ruck a a Leuphana University of Lüneburg, Institute for Sustainable and Environmental Chemistry, Building 13, Scharnhorststraße 1, 21335 Lüneburg, Germany b National Institute of Applied Sciences – Lyon, CNRS – CETHIL UMR5008, 69621 Villeurbanne Cedex, France c University of Lyon, 69361 Lyon Cedex 07, France highlights  Charging of closed thermochemical energy storage concept was studied numerically.  Pressure effect in kinetic modelling for thermochemical energy storage is presented.  A partial differential equations system was developed and applied.  Prediction of charging process in a thermochemical heat storage process is provided. article info Article history: Received 28 January 2014 Received in revised form 4 February 2015 Accepted 5 February 2015 Keywords: Reaction kinetics Thermal decomposition Salt-hydrates Thermochemical heat storage Numerical modelling abstract Thermal energy or heat storage systems using chemical reactions to store and release energy operate in charging and discharging phases. The charging phase in this work is a dehydration process with constant heating rate decomposing salt hydrates as chemical components resulting in the obtention of a less hydrated or anhydrous form and, at the same time, storing the released heat (energy storage). Latest research on thermal decomposition of several salt-hydrates concerned experimental and numerical investigations (Huang et al., 2010; Sugimoto et al., 2007). A mathematical model of heat and mass trans- fer in a fixed-bed reactor for heat storage is proposed on the basis of a set of partial differential equations (PDEs) controlling the balances of mass, conversion, and energy in the bed and the reactor. These PDEs are numerically solved by means of the finite element method using Comsol Multiphysics 4.3a. The objective of this paper is to describe an adaptive modelling approach and establish a correct set of PDEs describing the physical system and appropriate parameters for simulating the thermal decomposition process. Thus it could help in the design of thermal energy storage system. The recommendations the International Confederation for Thermal Analysis and Calorimetry (Vyazovkin et al., 2011) on kinetic behaviour were used to explain transport phenomena and reactions mechanism in gas and solid phases. The generalized Prout–Tompkins equation was therefore adopted with some modifications based on thermal analysis experiments and literature. The experimental data from the TGA–DSC measurements are then used to validate the kinetic model. This latter result after validation is used in the Comsol model to simulate the lab-scale reactor in charging mode (thermal decomposition). Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, most industrialized countries place great impor- tance on energy efficiency issues, such as CO 2 emissions, electricity peak demand and residential heat demand. For example, in Germany micro cogeneration, also called micro-CHP, is becoming popular, uses about 90% of the input energy to produce both elec- tricity and heat. However, the operation of the micro-CHP also produces heat loss estimated between 9% and 13% [4] released to the environment. This waste heat is left unused because it is rela- tively low grade. It can be retrieved for efficiency purpose using thermal energy storage systems (TESS). However, TESS not only allows the waste heat to be re-used, but also upgraded by means of chemical heat pump [5–8]. Thermochemical heat storage can be of different types: physisorption on adsorbing materials, such as zeolites, absorption in hygroscopic solutions, like a NaOH solu- tion and adsorption in salts, such as salt hydrates or molten salts. Salt hydrates were selected because their high energy density and low cost make them advantageous, their main disadvantage http://dx.doi.org/10.1016/j.apenergy.2015.02.011 0306-2619/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +49 4131 677 2951; fax: +49 4131 677 2822. E-mail addresses: osterland@leuphana.de, thomas.osterland@gmx.de (T. Schmidt). Applied Energy 154 (2015) 447–458 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy