## 1 Introduction  
Energy storage is regarded a key task for the transition from fossil to renewable sources of energy with fluctuating availability. With more than 50%, heat is the major part of end energy consumption [1]. To avoid losses of conversion from one type of energy to another (e.g., power to heat), energy is best stored in the form of its production or consumption. Within the different heat-storage options, namely sensible, latent and thermochemical, the latter is the most promising as it features high storage densities and the possiblity to store energy without losses. Different materials have been found to be suitable for thermochemical heat storage in material screenings [2, 3, 4]. Several material groups span a large range from low level to high temperature applications, therein carbonates [5], hydrates [6], oxides [7] and hydroxides. Within those, the group of hydroxides is environmentally friendly [8], cheap [9], and covers a wide range of reaction temperatures. Several applications are envisaged, such as domestic heating [10], enhancement of CHP plants [11] or concentrated solar-power plants [12]. So far, however, no technology is commercially available. Their development requires further research. This work puts a focus on the reaction system CaO/Ca(OH)\({}_{2}\) that is described by the following reaction equation:  
\[CaO_{(s)}+H_{2}O_{(g)}\rightleftharpoons Ca(OH)_{2,(s)}+\Delta H_{R}. \tag{1}\]  
This reaction system has already been studied on different scales. Small-scale studies of a few grams of solid material addressed the cycling stability [13] and material parameters [8]. Furthermore, the reaction enthalpy and thermodynamic equilibrium was investigated. The reaction enthalpy lies within the range of \(\Delta H_{R}=~{}94.6\) kJ/mol [14] to \(\Delta H_{R}=109\) kJ/mol [15]. For water vapor pressures between \(1\times 10^{3}\) to \(3\times 10^{6}\) Pa, applications between 550 K and 1000 K are feasible [8; 14]. Studies on the reaction mechanisms deliver contradicting results: for example, [PERSON] et al. [16] identified a shrinking core model, whereas [PERSON] et al. [17] found a pseudo-homogeneous model. Reference [18] assumes that the reaction kinetics depend strongly on the reaction conditions for pressure and temperature. This allows to conclude that the resulting reaction kinetics are thus subject to uncertainty. [PERSON] et al. [19] and [PERSON] et al. [20] however state that at high pressure ranges, the reaction rate is only limited by heat transfer. They apply the reaction kinetics of Reference [21] which is based on theoretical considerations and does not obey a specific reaction mechanism. [PERSON] et al. [22] presented another way of representing the reaction rate based on information about the propagation of the reaction front for a different reaction system. However, it is beyond the scope and aim of this study to introduce completely new reaction kinetics for the reaction system CaO/Ca(OH)\({}_{2}\). Instead, we build upon the findings of Reference [20] and apply the reaction kinetics of Reference [21]. The reaction system CaO/Ca(OH)\({}_{2}\) has been studied on larger scales in fixed-bed reactors. [PERSON] et al. [23] present a directly heated fixed-bed reactor at the laboratory scale, containing 60 g of reactive powder. [PERSON] et al. [24] presented a reactor with an indirect heating concept on a kW-scale. Additionally, [PERSON] et al. [16] and [PERSON] et al. [9] present concepts for fluidized bed reactors. To enhance the understanding of such laboratory experiments, they often come along with modeling [25]. Modeling is used for theoretical analysis, identification of mechanisms, and optimization. For quantitatively reliable predictions, mathematical models need to be validated. While suitable experimental data for model validation is sparse and often subject to uncertainties, several models have been presented for fixed-bed thermochemical heat-storage reactors without proof of validation. [PERSON] et al. [26] study the influence of particle sizes, [PERSON] et al.