In this study, the development and comparative characterization of different composite sorbents for thermal energy storage applications is reported. Two different applications were targeted, namely, low-temperature space heating (SH) and domestic hot water (DHW) provision. From a literature analysis, the most promising hygroscopic salts were selected for these conditions, being LiCl for SH and LiBr for DHW. Furthermore, two mesoporous silica gel matrixes and a macroporous vermiculite were acquired to prepare the composites. A complete characterization was performed by investigating the porous structure of the composites before and after impregnation, through N₂ physisorption, as well as checking the phase composition of the composites at different temperatures through X-ray powder diffraction (XRD) analysis. Furthermore, sorption equilibrium curves were measured in water vapor atmosphere to evaluate the adsorption capacity of the samples and a detailed calorimetric analysis was carried out to evaluate the reaction evolution under real operating conditions as well as the sorption heat of each sample. The results demonstrated a slower reaction kinetic in the vermiculite-based composites, due to the larger size of salt grains embedded in the pores, while promising volumetric storage densities of 0.7 GJ/m³ and 0.4 GJ/m³ in silica gel-based composites were achieved for SH and DHW applications, respectively.

Adsorption heat transformation (AHT) is energy and environment saving technology that allows the effective utilization of renewable and waste heat with low-temperature potential. For the enhancement of AHT efficiency, properties of the working pair “adsorbent–adsorbate” have to be intelligently adapted to the operating conditions of the specific AHT cycle. In this work, the applicability of ATH technology in the Russian Federation (RF) was analyzed. For various geographic zones of the RF, the proper AHT application (cooling, heating, heat amplification, or storage) was selected depending on the zone climatic conditions. Data on the adsorption equilibrium for more than 40 “adsorbent–adsorbate” pairs collected from the literature were analyzed to select the most suitable pairs for the particular application/zone. Recommendations on AHT applications and the proper working pairs for the considered RF climatic zones are made.

In this work, four radiators with different core geometries were tested using a wind tunnel. The values of the global heat transfer coefficient (UA = 5 ÷ 65 W/K) were measured depending on the flow of air and water. The obtained UA values correlate well with the data of sorption experiments described in the literature. The found correlations between the Nusselt and Reynolds numbers made it possible to propose an algorithm for ranging commercial air radiators for the use in adsorption heat transformers. It is shown that the use of a wind tunnel can serve as an effective tool for express assessment of the prospects of using air radiators for adsorption heat conversion without destroying radiators or their direct testing in a complex adsorption installation requiring vacuum maintenance.

SAPO-34 nanocrystals with sizes of 50–150 nm were obtained via steam-assisted crystallization (SAC) for 5 h at 200 °C from two types of aluminum precursors—aluminum isopropoxide and boehmite. A reaction mixture composition with a small amount of organic template tetraehylammonium hydroxide (TEAOH) was used with the molar ratio TEAOH/Al₂O₃ = 1/1. The alumina precursor type and duration of the SAC (5 and 24 h) on the crystal size, texture, and acid properties were investigated. The SAPO-34 nanocrystals that we obtained possess a large micropore volume of 0.22–0.24 cm³/g and a specific surface area of 651–695 m²/g. When the crystallization was prolonged for up to 24 h, a SAPO-18 structure appeared, but the micropore and mesopore volumes changed insignificantly. Using boehmite as the aluminum precursor led to higher mesoporosity of the material but a little bit lower acidity when compared with the samples prepared from aluminum isopropoxide. In addition, the method proposed was used for preparing a SAPO-34-coated aluminum adsorber heat exchanger. Thus, the synthesis method proposed is affordable and effective to prepare SAPO-34 highly crystalline nanoparticles, with no need for post-synthetic procedures as the mother liquor separation from nanocrystals.

The different adsorption applications require the development of sorbents with predetermined properties. One of the ways for fine tuning the adsorption properties of the material is using a binary salt system as an active sorbing component. The aim of this work is to conduct a precision investigation of thermodynamic data on the sorption equilibrium of composite sorbents “(CaCl₂ + CaBr₂) confined to the silica gel pores” with water vapour. The isotherms and isosteres (at an uptake of N = 1.5 and 3.6 mole/mole) of water sorption on the composites were measured. It was shown that at a fixed temperature, the composites based on solid solutions of CaCl₂ in CaBr₂ form complexes with water at a pressure that is dependent on the CaCl₂/CaBr₂ molar ratio. The isosteric enthalpy and entropy of water sorption (ΔH = −48 ± 3 kJ/mol ΔS = −108 ± 2 J/(mol·K)) at N = 3.6 mole/mole were midway between the same parameters for composites on the base of the pure salts CaCl₂ and CaBr₂. The novelty of this work is in the design of sorbents optimized for air conditioning in hot climates and air drying cycles. It was shown that the use of the binary CaCl₂ + CaBr₂ system confined to the silica pores can be an effective tool for designing innovative materials with predetermined properties.

Adsorption energy storage is a promising resource-saving technology that allows the rational use of alternative heat sources. One of the most important parts of the adsorption heat accumulator is the adsorber heat exchanger. The parameters of heat transfer in this unit determine how fast heat from an alternative energy source, such as the Sun, will be stored. For the design of adsorption heat accumulators, plate fin heat exchangers are mainly used. In this paper, the procedure for the estimation of the global heat transfer coefficient for the adsorber heat exchanger depending on its geometry is considered. The heat transfer coefficient for a LiCl/SiO₂ sorbent flat layer under conditions of heat storage stage was measured. Based on these data, the global heat transfer coefficients for a number of industrial heat exchangers were theoretically estimated and experimentally measured for the adsorption cycle of daily heat storage. It was shown that theoretically obtained values are in good agreement with the values of the global heat transfer coefficients measured experimentally. Thus, the considered technique makes it possible to determine the most promising geometry of the plate fin heat exchanger for a given adsorption heat storage cycle without complicated experiments.