## 2 Materials and Methods  
### The Experimental Facility  
In the frame of the present paper, an experimental device able to reproduce performances of an adsorption storage system has been developed as well as a methodology for testing the process under long-term conditions. The adsorption experimental plant works on 4 different temperature levels:  
* Desorption heat is supplied by the heat source at temperature \(T_{des}\). Due to normative constraint, the maximum value of heat supply cannot overcome 90 \({}^{\circ}\)C.
* Condensation heat is released to the environment at a temperature \(T_{cond}\). The condensation source can be set in a large range of 5-30 \({}^{\circ}\)C for experimental purposes. * Adsorption heat is supplied to the final user at the temperature \(T_{ads}\) in a large range of 5-30 \({}^{\circ}\)C.
* Evaporation heat is provided from a low temperature heat source in a range of 20-40 \({}^{\circ}\)C.  
The experimental test rig has been designed taking into account the requirement of versatility (for testing different heat exchanger configurations or different plant configurations) and automatic control (for long-term test and data acquisition). In order to validate the mathematical model of adsorption/desorption, a small-scale reactor has been designed and constructed. The concept idea of the novel configuration, so called \"all-in-one\", is an embedded solution for both the heat exchanger module and phase changer module. This configuration involves a unique vacuum case with a considerable simplification of mechanical architecture and cost decrease. In Figures 1 and 2, cross-sections of the experimental reactor are reported. Figure 1: Midplane cross-section of reactor “all-in-one” configuration. The reactor is composed by:  
* Heat storage module (zeolite bed) with a total volume of 200 L, including a U-shaped heat exchanger with a finned tube (rectangular fin with 25 mm spacing). The lateral faces are realised with a metallic mesh able to retain zeolite 13X-grains, allowing vapour flow through the lateral faces. The zeolite bed is heated (during the desorption phase) and cooled (adsorption phase) by the thermal fluid (i.e., hot water) flowing into the finned tube. * Phase changing module placed at the bottom (water pool) and on two lateral faces (cold plates) with a tube coil which is cooled (during the condensation/desorption phase) and heated (during the evaporation/adsorption phase) through thermal fluid flowing into the coil tube. Stainless-steel is used for all the metallic construction. The whole reactor has a removable mechanical system (with a bolt flange and vacuum sealing) in order to test different heat exchanger configurations or different evaporator/condenser technical designs. In Figure 3, the views of the zeolite bed and vacuum case are shown. The whole reactor external casing has been insulated with a mineral insulation roll 50 mm thick with a thermal conductivity at ambient temperature equal to 0.039 W/(m K). The pad is faced on one side with aluminium kraft paper and on the other side with a glass mat. The overall estimated thermal losses are about 3.85 W/K and can be considered negligible in the modelling and experimental activities, discussed below. The reactor has been instrumented with the following items:  
* 2 piezoelectric pressure sensors for vacuum chamber with an accuracy equal to 1.25 mbara. * 2 PT100 class A sensors for HTF Heat Exchanger temperature with accuracy at 0 and 100 \({}^{\circ}\)C, equal to \(\pm 0.15\)\({}^{\circ}\)C and \(\pm 0.35\)\({}^{\circ}\)C, respectively. Figure 3: Views of heat exchanger and vacuum chamber. Figure 2: Lateral cross-section of reactor “all-in-one” configuration. 2 PT100 class A sensors for HFT Evaporator/Condenser temperature, with accuracy at 0 and 100 \({}^{\circ}\)C, equal to \(\pm\)0.15 \({}^{\circ}\)C and \(\pm\)0.35 \({}^{\circ}\)C, respectively. 1 visual pressure indicator for vacuum chamber. 4 thermocouples, type K, for temperature bed acquisition with accuracy equal to \(\pm\)1.1 \({}^{\circ}\)C (as shown in Figure 4).