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Sorption devices are important tools for the efficient utilization of fuels and waste heat. Amid a tremendous diversity of cycles and applications, all sorption systems have an equilibrium vapor pressure that depends on the sorbent temperature and composition. The vapor pressure properties of working fluids are reported in the literature in a variety of ways, which impedes wide-ranging cross comparisons or screening studies for novel applications. This work compiles equilibrium vapor pressure properties for 123 liquid absorbents with 31 absorbates and 139 solid adsorbents with 16 adsorbates. The adsorption pairs are represented with six functional forms. Most of the absorption pairs are represented with 10 functional forms, plus several that are represented with custom empirical equations. Because the functional forms used in the literature vary widely, in this work each functional form was generalized. This paper is designed to facilitate comparisons of working fluid properties for screening studies, provide a quick reference to existing research, and present a framework for standardizing the reportage of vapor pressure equilibrium data for existing and future working pairs.

The lack of robust and low-cost sorbent materials still represents a formidable technological barrier for long-term storage of (renewable) thermal energy and more generally for Adsorptive Heat Transformations—AHT. In this work, we introduce a novel approach for synthesizing cement-based composite sorbent materials. In fact, considering the number of available hygrosopic salts that can be accommodated into a cementitious matrix—whose morphological properties can be also fine-tuned—the new proposed in situ synthesis paves the way to the generation of an entire new class of possible sorbents for AHT. Here, solely focusing on magnesium sulfate in a class G cement matrix, we show preliminary morphological, mechanical and calorimetric characterization of sub-optimal material samples. Our analysis enables us to theoretically estimate one of the most important figures of merit for the considered applications, namely the energy density which was found to range within 0.088–0.2 GJ/m3 (for the best tested sample) under reasonable operating conditions for space heating applications and temperate climate. The above estimates are found to be lower than other composite materials in the literature. Nonetheless, although no special material optimization has been implemented, our samples already compare favourably with most of the known materials in terms of specific cost of stored energy. Finally, an interesting aspect is found in the ageing tests under water sorption-desorption cycling, where a negligible variation in the adsorption capability is demonstrated after over one-hundred cycles.

The present paper reports about the experimental characterization of a recently developed composite sorbent of water, LiCl/vermiculite, for thermal energy storage applications. The sorption ability as well as the thermal storage capacity (TSC) of the material itself were tested in a dedicated TG/DSC apparatus, under two relevant boundary conditions, namely, seasonal (SS) and daily (DS) storage applications. The dynamic behavior of the composite sorbent was tested by means of a G-LTJ apparatus in flat-plate adsorber configuration, under both SS and DS working conditions. Finally, preliminary tests on a lab-scale TES configuration were performed and reported. The main outcomes confirm that the composite is promising for TES applications, reaching the TSC up to 2.15 kJ/g under SS conditions. The stability of the composite was proven for 14 consecutive sorption/desorption cycles under conditions similar to those at real SS and DS cycles. The kinetic adsorption tests confirmed a slowdown of the sorption dynamics when passing from 1.7–2.0 mm to 2.36–2.80 mm of the grain size. Furthermore, the adsorption kinetic under SS mode is faster than of DS one. The preliminary testing in the lab-scale TES at SS cycle allowed getting TSC up to 1.25 kJ/g with a specific power up to 2.1 kW/kg.

The present work aims at the thermodynamic analysis of different working pairs in adsorption heat transformers (AdHT) for low-temperature waste heat upgrade in industrial processes. Two different AdHT configurations have been simulated, namely with and without heat recovery between the adsorbent beds. Ten working pairs, employing different adsorbent materials and four different refrigerants, have been compared at varying working boundary conditions. The effects of heat recovery and the presence of a temperature gradient for heat transfer between sinks/sources and the AdHT components have been analyzed. The achieved results demonstrate the possibility of increasing the overall performance when internal heat recovery is implemented. They also highlight the relevant role played by the existing temperature gradient between heat transfer fluids and components, that strongly affect the real operating cycle of the AdHT and thus its expected performance. Both extremely low, i.e., 40–50 °C, and low (i.e., 80 °C) waste heat source temperatures were investigated at variable ambient temperatures, evaluating the achievable COP and specific energy. The main results demonstrate that optimal performance can be achieved when 40–50 K of temperature difference between waste heat source and ambient temperature are guaranteed. Furthermore, composite sorbents demonstrated to be the most promising adsorbent materials for this application, given their high sorption capacity compared to pure adsorbents, which is reflected in much higher achievable specific energy.

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.

This chapter focuses on the experimental characterization techniques commonly employed to get a deep understanding of the thermal energy storage (TES) materials properties. In particular, experimental methodologies available to characterize thermophysical parameters qualifying both thermodynamic and dynamic performance of TES materials are discussed, trying to highlight pros and cons. The analysis is performed for the three TES categories, sensible, latent and thermochemical, representing a contribution toward the proper selection of experimental techniques at material level.

The modeling of sorption systems for thermal energy storage can involve different levels, that is, from powdery level (modeling of material) up to system level and make use of a continuum or lumped (noncontinuum) approach. Different levels of detail and different scales of the problem require the implementation and solutions of diverse sets of equations and solution methodologies. In this chapter, the model at reactor and system level is discussed, with specific focus on the equilibrium description of working pairs and the solution of heat and mass transfer problems in continuum or lumped reactor systems, as well as the black-box models employed when the integration of a thermal energy storage in a more complex energy system is required. Finally, some examples of applications are discussed to show the potentialities of the different methodologies.

Sorption thermal energy storage (STES) systems exploit reversible sorption and desorption processes to store thermal energy as potential energy between a sorbate (e.g., water, ammonia, alcohols) and a sorbent (e.g., salt solutions, salt hydrates, solid sorbents). This technology belongs to the wider family of thermo-chemical reactions and is specifically suited for low and medium charging temperatures (i.e., below 200°C). In this chapter, the working principle of different STES configurations is discussed. Furthermore, experimental methodologies to evaluate the expected efficiency of the working pairs are described. Finally, some examples of lab-scale reactors recently developed and tested are described to present the current state of the technology development.

Evaporation of water at sub-atmospheric pressures, close to its triple point, is gaining attention for the wide range of engineering applications. However, the mechanism and boiling regimes are still not completely clear and a correlation between operating conditions, geometric features of the evaporator and achievable heat transfer is still missing. In this context, the present paper aims at the study of a fin-and-tube heat exchanger working as an evaporator in the pressure range of 1–7kPa. The experimental study analyses the effect of the main operating parameters (temperature of the heat transfer fluid, superheat, inclination of the heat exchanger) and attempts to find correlations suitable for the engineering design of evaporator under the investigated conditions. The results allowed the identification of the main factors influencing the heat transfer, i.e. the temperature of the heat transfer fluid and, secondarily, the logarithmic mean temperature difference, as well as the derivation of expressions that correlate the evaporation power and the heat transfer coefficients with operating conditions.

The thermal masses of components influence the performance of many adsorption heat pump systems. However, typically when experimental adsorption systems are reported, data on thermal mass are missing or incomplete. This work provides original measurements of the thermal masses for experimental sorption heat exchanger hardware. Much of this hardware was previously reported in the literature, but without detailed thermal mass data. The data reported in this work are the first values reported in the literature to thoroughly account for all thermal masses, including heat transfer fluid. The impact of thermal mass on system performance is also discussed, with detailed calculation left for future work. The degree to which heat transfer fluid contributes to overall effective thermal mass is also discussed, with detailed calculation left for future work. This work provides a framework for future reporting of experimental thermal masses. The utilization of this framework will enrich the data available for model validation and provide a more thorough accounting of adsorption heat pumps.

In this study, the development and characterization of composite sorbents based on commercial mesoporous silica gels and LiCI for seasonal thermal energy storage (STES) applications is described. The reported activity aims at validating the operation of sorption STES in various cold climatic zones in Europe. Accordingly, the reference boundary conditions were identified by means of a climatic analysis in two climatic zones, namely, Central and Northern Europe. The acquired mesoporous silica gels were characterized, to evaluate the textural properties, i.e. specific pore volume and pore size, needed to define the optimal salt solution compositions to maximize the amount of salt embedded. The synthesized samples were firstly investigated using scanning electron microscopy and nitrogen physisorption that demonstrate the presence of a small quantity of salt over the external surface rather than inside the pores. A hydrothermal treatment, based on slow adsorption followed by a slow desorption step, was defined to solve this issue. Finally, starting from the measured equilibrium isobars, the expected STES density at material level was evaluated, obtaining values as high as 1080 J/g under cold Northern European climatic condition, corresponding to 650 MJ/m(3). (C) 2020 The Authors. Published by Elsevier Ltd.

This article evaluates the hydrothermal and mechanical stability of an adsorbent composite foam based on zeolite silicone for application in adsorption heat pump. The adsorption properties of the fresh composite adsorbents and their morphological features were already presented in previous papers. In the present work, hydrothermal aging of composite foams, at varying SAPO-34 zeolite contents and under real operating conditions, was carried out in order to verify the stability of the synthetized material. This improvement of knowledge is a key point for the industrial application. This evaluation was successfully performed by means of adsorption measurements and compression test on aged samples, up to 1500 aging cycles. The adsorption properties of composite foams are effective and stable up to the maximum number of cycles of the aging process. Instead, from the mechanical point of view, composite foams with high content of zeolite, aged at long cycles, evidenced a slight stiffening that stimulates mechanical brittle behavior. The composite foam with 67% zeolite filler represents a threshold value beyond which the action of the hydrothermal aging implies a significant loss of flexibility and mechanical integrity, which limits its applicability under typical conditions.

This paper presents the experimental characterisation of three zeotype materials, namely, AlPO-18, FAPO-34 and SAPO-34, suitable for adsorption heat transformation applications, employing water as refrigerant. Morphological and thermo-physical analyses were performed on each sample. In particular, the adsorption capacity of each material was evaluated by measuring a complete set of water vapour adsorption/desorption isotherms, in order to investigate the hysteresis effect. The obtained equilibrium data were fitted by means of Dubinin-Astakhov equation, both for adsorption and desorption branches. Finally, a thermodynamic analysis of the achievable performance of these three working pairs was performed under three main operating conditions, namely, thermal energy storage, air conditioning and heat pumping. The achieved results confirmed the potentiality of these adsorbents, showing promising cooling and thermal COP, up to 0.80 and 1.60 respectively, and heat storage capacities both for daily and seasonal operation.

The present paper presents the development of a thermal energy storage system for application with non-concentrating solar plants using phase change materials (PCMs). The outcomes of an experimental analysis on commercial and non-commercial PCMs suitable for the desired temperature range is presented, with main focus on to the enthalpy and the cycle stability of the materials. Particularly, a first evaluation of possible degradation mechanisms in hydrated salts was investigated by means of Nuclear Magnetic Resonance (NMR) spectroscopy. The best performing materials have been implemented in a numerical model, based on the enthalpy method, used for the design of a thermal storage system. The configuration of the system, starting from a simple shell-and-tube layout, has been optimised by inserting asymmetric fin-and-tubes and the results with two selected materials have been compared. The analysis has shown that the most promising materials are the commercial ones belonging to the classes of paraffinic materials and hydrated salts and that, with the designed configuration, it is possible to store up to 200 kJ/m3 and get a peak power during discharge of about 1.5 kW.

This paper reports about the combined experimental and numerical investigation of a novel small size multi-generation system, for electric (i.e.

Solar cooling technology is an attractive way to use solar thermal energy to produce cooling for buildings. The employment of taphase change materials (PCMs) as heat storage medium, to increase the range of utilization of solar thermal energy, thus improving the overall system performance, is considered very attractive. Nevertheless, in order to allow the development of latent heat storage prototypes for such an application, it is mandatory to verify the thermo-physical performance as well as the long-term stability of the available materials. To this aim, in the present paper, the most attractive commercial PCM as well as neat chemical compounds operating in the temperature range between 80 °C and 100 °C, perfectly suitable for non-concentrating solar cooling systems, have been identified and completely characterized. In particular, several cycles have been performed on each material, to verify possible instabilities in their behavior. Most of the neat materials have confirmed to be promising for this application, thanks to their really high melting enthalpy, up to 255 J/g as showed for Aluminum Ammonium Sulfate Dodecahydrate. Nevertheless, all these materials are still not stable, showing high supercooling, allotropic phase transition, incongruent melting and even absence of re-crystallization, which makes necessary an intense work to bring them to a reliability level sufficient for real application. On the contrary, the commercial PCMs, even if mostly characterized by lower melting enthalpy, ranging between 120 and 150 J/g, confirmed their stability, which makes them ready for practical applications.

This paper reports about the first experimental activity on a composite material for thermal energy storage, based on a SrBr2·6H2O filled silicone foam. The morphological and thermal features of the composite with different salt content (i.e. between 40 wt.% and 70 wt.%) were investigated. The dehydration behavior was studied by thermo-gravimetric analysis. Furthermore, scanning electron and 3D optical microscopy were used to compare the cellular microstructure of the composite foams. The synthesized foams are characterized by a wellinterconnected cellular structure with a three-dimensional porous network. This, together with the high permeability to water vapor of the matrix favors water vapor diffusion and allows the reaction of all the salt embedded in the matrix. The main advantages of the composite material were analyzed and compared to other composites in literature. Since the production process, especially for higher salt content, seemed not sufficiently effective, causing a reduced foaming ration and lower ability to incorporate the salt hydrate, possible improvements were proposed and discussed. This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31). Dr. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia program.

In the present chapter, an introduction about the concept of sorption TES technology is reported. The closed and open configurations are discussed and an overview on the ongoing research and development activities for materials, components and systems is given.

In this paper, composites based on a standard mortar and two commercial microencapsulated phase change materials (PCMs) with nominal melting point of 23 degrees C and 26 degrees C in different percentage were produced and characterized. To this aim, an innovative experimental setup, able to contemporarily test two different samples subjected to the same temperature profile was designed and realized. The experimental results were then used to validate a numerical model, implemented in COMSOL Multiphysics. Finally, a parametric analysis was carried out to define optimized melting temperature for the PCM for Mediterranean application, aiming at reducing the overall energy consumption as well as to improve the comfort conditions inside buildings both during winter and summer. The results demonstrated that an optimal melting temperature of 27 degrees C is achieved under Sicilian climatic condition. Furthermore, adding 15 wt% of optimized PCM allows to improve the comfort conditions of about 15% compared to standard solutions based on pure cement mortars.

SAPO-34 – a silicoaluminophosphate microporous material – has recently attracted a great attention in the field of sorption thermal storage, since it is characterized by good water adsorption behavior (i.e. type V adsorption isotherms) and low regeneration temperature (i.e. 80 °C, for instance available by standard solar thermal energy collectors). However, the nanoscale mechanisms of water transport and adsorption in the microporous framework of SAPO-34 cannot be fully unveiled by experiments alone. In this work, water adsorption onto SAPO-34 is for the first time studied by means of an atomistic model built upon experimental evidence. First, Monte Carlo simulations are employed to set up a convenient atomistic model of water/SAPO-34 interactions, and numerical adsorption isotherms are validated against experimental measures. Second, the validated model is used to study the water diffusion through SAPO-34 by molecular dynamics simulations, and to visualize preferential adsorption sites with atomistic detail. Such atomistic model validated against experiments may ease the investigation and in silico discovery of silicoaluminophosphates for thermal storage applications with tailored adsorption characteristics.

This paper assesses the mechanical stability and dehydration behaviour of a new composite material constituted by magnesium sulphate hepta-hydrate, used as filler at vary contents, and a porous silicone, used as matrix in order to evaluate its applicability in sorption thermal energy storage field. This new composite was developed to avoid the typical issues of salt hydrates such as swelling, agglomeration and corrosion issues occurring during hydration/dehydration process. A preliminary physical-mechanical characterization, by means of morphological and calorimetric analysis, was carried out to investigate the main properties of the composite foams. The morphological characterization showed that the foam pores were homogenously distributed and well interconnected to each other. Thermogravimetric dehydration tests, have demonstrated that the tested samples are able to exchange efficiently water. Static compression tests evidenced a high compression stability of the material, indicating a high flexibility of the cellular silicone structure. Furthermore, cyclic compression test was performed to evaluate the progressive loss of salt at increasing number of the cycles. After 50 cycles, a reduction of salt hydrate up to 13% was observed. This behaviour, that is potentially a critical factor in these composite structures, was studied for showing that the loss of the salt does not compromise considerably the sorption storage performance of the filled silicone foams. Eventually, the assessment of thermo-gravimetric characteristics and mechanical stability was performed on the MgSO4·7H2O silicone composite foam. The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme.

In this paper, the experimental characterization of a latent heat storage prototype working in the range of 70–90 °C and characterized by an innovative configuration is presented. The storage consists of a Phase Change Material (PCM), namely a commercial paraffin, embedded in an asymmetric plate heat exchanger. The testing campaign was aimed at defining the effect of operating conditions (flow rate of the heat transfer fluid, charge and discharge temperatures), in terms of energy stored, power supplied to the user and storage efficiency. The results showed that the energy density stored is between 116 and 198 kJ kg−1, whereas power output during discharge varies between 4 and 10 kW. Subsequently, an analysis on part load operation was carried out, which evidenced that properly managing the storage, limiting the discharging to 80% of its maximum storage capacity, allows saving around 50% of time, thus increasing the power density. A thermal network model was proposed to study the contributions of the heat exchanger and phase change material to the overall heat transfer, demonstrating that the phase change material is limiting the heat transfer only when it is in the solid state. Finally, the storage was compared to another prototype developed by the authors employing the same material and a different heat exchanger (a fin-and-tube heat exchanger) according to different structural, energy and dynamic performance indicators. The results highlighted that the present system is especially suitable for applications with a high power demand from the user.

The present chapter deals with the main experimental characterizations available to measure the performance of sorbent working pairs used in sorption TES. The experimental methods for the evaluation of equilibrium sorption curves and the models for the sorption equilibrium description are introduced. Furthermore, theoretical and experimental approaches for the heat of sorption evaluation are defined and some examples, reported in the literature, about the thermal storage capacity evaluation of different working pairs are reported.

Recently, a new composite “LiCl inside Multi-Wall Carbon NanoTubes” (LiCl/MWCNT) has been suggested as water sorbent for Adsorption Thermal Energy Storage (ATES), because it has a large thermal storage capacity of 1.7 kJ/g for a daily heat storage cycle. This work addresses the results of the study of water sorption dynamics on the novel composite loaded into representative small scale fragments of a common finned flat-tube HEx. The study consists of four parts: (1) shaping the LiCl/MWCNT composite as grains using polyvinyl alcohol (PVA) as a binder; (2) analysis of sorption equilibrium for the pair “LiCl/ MWCNT/PVA – water”; (3) measuring the thermal storage capacity of the granulated LiCl/ MWCNT/PVA composite; (4) investigation of water sorption dynamics on the LiCl/MWCNT/PVA under typical conditions of the daily storage cycle. It is shown that the thermal storage capacity of the LiCl/MWCNT/PVA composite equals 1.5–1.6 kJ/g. The specific power reaches 4.2 and 9.8 kW/kg of the heat release and thermal storage stages, respectively. The results obtained show that the working pair “LiCl/MWCNT/PVA – water” appears to be advantageous for ATES.

Adsorption heat pumps and chillers provide sustainable heating and cooling by transforming waste or solar heat. To increase the efficiency of adsorption heat pumps and chillers, new adsorber designs are constantly proposed. However, evaluating the efficiency of new adsorber designs is a time- and money consuming task. To reduce time and costs, we combine two methods in this work: First, the kinetic performance is evaluated experimentally using the Large Temperature Jump method for a representative adsorber part. Second, a dynamic model for the adsorber is developed and validated. The validated adsorber model is used in a dynamic model of a complete adsorption heat pump cycle. Our approach allows for a sound analysis of novel adsorber designs by determination of the efficiency indicators specific cooling power (SCP) and coefficient of performance (COP) based on a representative adsorber part. We studied a representative adsorber part made from an extruded aluminum tube heat exchanger filled with silica gel 123. We determined SCP and COP as function of adsorption and desorption times and found a maximum SCP 268 W kg(-1) with a corresponding COP of 0.51 for a desorption time of 125 s and an adsorption time of 200 s. (C) 2015 Elsevier Ltd. All rights reserved.

This paper reports an experimental study aimed to elucidate the effect of non-adsorbable gases (air and hydrogen) on dynamics of isobaric adsorption stage of an adsorptive chiller (AC) cycle. This is the first study performed on real small scale adsorbers, based on commercial heat exchangers (HExs) filled with loose grains of the adsorbent AQSOA (TM)-FAM-Z02. The adsorption dynamics was studied by a gravimetric large temperature jump method under conditions of typical AC cycle. Three notable observations are described in the paper: (1) at any gas pressure P-gas, the experimental uptake curves are exponential; (2) the adsorption rate is extremely sensitive to traces of residual air and depends on the HEx geometry and the nature of residual gas; (3) the effect of hydrogen is less dramatic as compared with air. The minimal amount of residual air necessary to form the blocking air-rich layer is evaluated by developing a one-dimensional stationary model of the vapour adsorption in the presence of gas. This amount is found to be highly sensitive to the total vapour pressure and the HEx mass transfer surface area. Practical recommendations on avoiding/dumping the effect of residual gas are made. (C) 2016 Elsevier Ltd. All rights reserved.

Salt hydrates, such as MgSO4·7H2O, are considered attractive materials for thermal energy storage, thanks to their high theoretical storage density. However, pure salt hydrates present some challenges in real application due to agglomeration, corrosion and swelling problems during hydration/dehydration cycles. In order to overcome these limitations, a composite material based on silicone vapor-permeable foam filled with the salt hydrate is here presented. For its characterization, a real-time in situ environmental scanning electron microscopy (ESEM) investigation was carried out in controlled temperature and humidity conditions. The specific set-up was proposed as an innovative method in order to evaluate the morphological evolution of the composite material during the hydrating and dehydrating stages of the salt. The results evidenced an effective micro-thermal stability of the material. Furthermore, dehydration thermogravimetric/differential scanning calorimetric (TG/DSC) analysis confirmed the improved reactivity of the realized composite foam compared to pure MgSO4·7H2O. This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31). This work was partially supported by ICREA under the ICREA Academia program.

Analysis of the Ad-HEx dynamic behaviour is of pivotal importance in development of advanced adsorber concepts, enabling reduction of weight and volume of the real adsorption heat pump/chiller unit, as well as its energy density enhancement.

In Chap. 2, the two main methods to study the sorption dynamics for AHT cycles were widely described: (i) the Large Pressure Jump (LPJ) method, in which adsorption is initiated by a jump of pressure over the sample, is the most adequate for pressure-driven AHT cycles; (ii) the Large Temperature Jump (LTJ) method, in which adsorption is enabled by a temperature swing of a heat exchanger wall that is in contact with the adsorbent under an almost isobaric ad/desorption stage, is the proper choice for temperature-driven AHT cycles (see Chaps. 1 and 2). In this chapter, the main factors affecting the sorption dynamics will be highlighted for temperature-driven AHT cycles by the analysis of results achieved by the two versions (namely V-LTJ and G-LTJ) of the LTJ method.

This paper presents the dynamic modelling of a hybrid cascade chiller for solar cooling in industrial applications driven by Fresnel solar thermal collectors. The chillercomprises an adsorption module, which is directly connected to the bottoming vapor compression chiller. This cascade configuration allows enhancing theoverallelectric COP, since the adsorption module is operated to dissipate the heat rejected by the vaporcompression chiller, thus reducing the condensation temperature quite below the ambient temperature. The model was implemented in Dymola/Modelica, allowing describingheat and mass transfer phenomena insideeach component. The complete model was then validated against experimental data obtained on a cascade chiller prototype at the CNR ITAE lab. Finally, a reference daily simulation was performed to evaluate the ability of the developed chiller in providing cooling energy to a typical industrial application.

In the present work, adsorption performances of an innovative composite adsorber, based on SAPO-34-silicone composite macro-cellular foams, are reported. The choice of a foamed structure was assessed to improve the water vapor access towards the embedded zeolite keeping good adsorption heat pump dynamic performance. Depending on zeolite amount used as filler, zeolite/silicone foams evidenced a soft and open cell configuration (low zeolite content) or rigid and closed one (high zeolite content). Morphological analysis evidenced that the cellular structure of the foam is homogeneous and well distributed along the foam cross section. Adsorption tests showed that the adsorbent foamed samples have very effective adsorption capabilities indicating that the porous structure of the filled pure zeolite was not obstructed. SAPO-34 filler contributed actively, with an efficiency above 90%, to the adsorption performances of the composite foam. Starting from experimental equilibrium data, a simple thermodynamic analysis based on energy balances was carried out for air conditioning application. Results of the analysis demonstrated that foam technology can guarantee cooling COP up to 7% higher than that estimated for the typical adsorber solution based on loose adsorbent grains inside an aluminum finned-flat tube heat exchanger, which is very promising for practical application in adsorption heat pumps.

Imaging in the infrared wavelength range has been fundamental in scientific, military and surveillance applications. Currently, it is a crucial enabler of new industries such as autonomous mobility (for obstacle detection), augmented reality (for eye tracking) and biometrics. Ubiquitous deployment of infrared cameras (on a scale similar to visible cameras) is however prevented by high manufacturing cost and low resolution related to the need of using image sensors based on flip-chip hybridization. One way to enable monolithic integration is by replacing expensive, small-scale III-V-based detector chips with narrow bandgap thin-films compatible with 8- and 12-inch full-wafer processing. This work describes a CMOS-compatible pixel stack based on lead sulfide quantum dots (PbS QD) with tunable absorption peak. Photodiode with a 150-nm thick absorber in an inverted architecture shows dark current of 10(-6) A/cm(2) at 2 V reverse bias and EQE above 20% at 1440 nm wavelength. Optical modeling for top illumination architecture can improve the contact transparency to 70%. Additional cooling (193 K) can improve the sensitivity to 60 dB. This stack can be integrated on a CMOS ROIC, enabling order-of-magnitude cost reduction for infrared sensors.

The aim of the present paper is the experimental characterization of adsorbent materials suitable for practical applications in adsorption refrigeration systems, employing ethanol as refrigerant. Different commercial activated carbons as well as a properly synthesized porous composite, composed of LiBr inside a silica gel host matrix, have been tested. A complete thermo-physical characterization, comprising nitrogen physi-sorption, specific heat and thermo-gravimetric equilibrium curves of ethanol adsorption over the sorbents, has been carried out. The equilibrium data have been fitted by means of the Dubinin – Astakhov equation. On the basis of the experimental data, a thermodynamic evaluation of the achievable performance of each adsorbent pair has been estimated by calculating the maximum COP (Coefficient of Performance) under typical working boundary conditions for refrigeration and air conditioning applications. The innovative composite material shows the highest thermodynamic performances of 0.64–0.72 for both tested working conditions. Nevertheless, the best carbonaceous material reaches COP value comparable with the synthesized composite. The results have demonstrated the potential of the chosen adsorbents for utilization in adsorption cooling systems.

This paper presents a novel experimental protocol for the evaluation of the thermodynamic performance of working pairs for application in adsorption heat pumps and chillers. The proposed approach is based on the experimental measurements of the main thermo-physical parameters of adsorbent pairs, by means of a DSC/TG apparatus modified to work under saturated vapour conditions, able to measure the ads-/desorption isobars and heat flux as well as the adsorbent specific heat under real boundary conditions. Such kind of activity allows to characterize the thermodynamic performance of an adsorbent pair allowing the estimation of the thermal Coefficient Of Performance (COP) both for heating and cooling applications, only relying on experimental values. The experimental uncertainty of the method has been estimated to be around 2%, for the COP evaluation. In order to validate the proposed procedure, a first test campaign has been carried out on the commercial adsorbent material, AQSOA-Z02, produced by MPI (Mitsubishi Plastics Inc.), while water was used as refrigerant. The proposed experimental methodology will be applied on several other adsorbent materials, either already on the market or still under investigation, in order to get an easy and reliable method to compare thermodynamic performance of adsorptive working pairs.

Aim of this work is to present the results of the testing of a small scale hybrid sensible/latent storage system (nominal volume 48.6 dm3), consisting of water in which macro-encapsulated phase change materials (PCMs) are added. Two different PCMs were macro-encapsulated, a commercial paraffin and a hydrate salts mixture prepared in the CNR ITAE lab, and loaded inside the tank in order to be tested. Different volume ratios between the PCM and the water were tested. The tests were conducted simulating different domestic hot water draw-off profiles. The resulting data showed an appreciable increase of heat storage capacity per unit of volume, even for limited fractions of PCM employed, reaching up to 10% of heat storage increasing by 1.3 dm3 of hydrate salts mixture added. Finally, the experimental results were used to test a numerical method of a PCM enhanced tank for dynamic plant simulations in ESP-r environment.

In this study, the thermodynamic analysis of several adsorption working pairs for adsorption heat storage applications at domestic level is presented. The selected working pairs employ different working fluids (i.e. water, ethanol, ammonia, methanol) and different adsorbent materials such as classical zeolites, silica gels, alumino-phosphates, composite sorbents and activated carbons. The simulations have been performed taking into account desorption temperatures in the range between 80 °C and 120 °C, compatible with non-concentrating solar thermal collectors, under seasonal heat storage working conditions. The composite sorbent MWCNT-LiCl with both water and methanol as working fluid showed the highest heat storage density under practical working boundary conditions. Among the standard adsorbents, the zeotype AQSOA Z02 showed promising achievable heat storage densities. Classical working pairs, such as zeolite 13X/water, commonly employed for heat storage applications, are not suitable for this working range. Finally, also the influence of the metal to sorbent mass ratio, due to the heat exchanger, was investigated, demonstrating that it can reduce the achievable amount of heat released to the user up to 30%.

The enhancement of the efficiency of adsorption heat pumps depends on the adsorption capacity of the adsorbent materials as well as on heat transfer efficiency between the adsorbent material in contact with the heat exchanger and the heat transfer fluid. The heat transfer efficiency can be improved by coating the heat exchangers with a thin layer of adsorbent material consolidated by means of a proper binder. In the present paper, three innovative silane-based adsorbent coating compositions, employing a commercial SAPO 34 as adsorbent material, are presented. Their physico-chemical and the mechanical features have been deeply studied, demonstrating promising characteristics which make them as an attractive solution to enhance achievable power density of adsorption machines.

The paper presents the realization and experimental characterization of a lab-scale latent heat storage, specifically developed for solar cooling applications. The latent heat storage is based on a compact fin-and-tube stainless steel heat exchanger (HEX) and a commercial paraffin blend, having a nominal melting temperature of 82 °C, suitable for solar cooling plants employing non-concentrating solar collectors technology. The realised heat storage has been experimentally characterised in lab, by means of a test rig able to simulate the working boundary conditions of a solar cooling plant. Charging and discharging tests have been performed both simulating a completed charge phase followed by a complete discharge phase, to analyse system efficiency and achievable energy storage density. Furthermore, dynamic tests, simulating short consecutive charge/discharge phases (with incomplete phase change), have been accomplished, to analyse the heat transfer efficiency inside the reactor. Main results confirmed that the heat storage density increases of about 50%, compared to sensible water storages. Satisfactory discharge efficiency, ranging between 45% and 60% has been obtained under analysed working conditions. Average discharging power between 0.7 and 1.2 kW has been measured, which confirms the necessity to further optimize the HEX efficiency as well as the thermal conductivity of the employed PCM.

Methanol, and more recently ethanol, have been deeply employed as adsorbate phase (refrigerant) in adsorption chiller and heat pump applications (e.g. refrigerator adsorption ice maker). The use of anhydrous alcohols however can cause several problems related to the corrosiveness of such molecules towards light alloys (from titanium to aluminium). The problem was already highlighted in bio-fuel technology where bio-ethanol was considered as a promise alternative to fossil hydrocarbons. Water content was observed as one of the main factors influencing corrosion rate. In the present works several accelerated corrosion tests on 6061 Aluminium alloy have been carried out in autoclave in a temperature range from 110 to 135 °C with different ethanol to aluminium mass ratio. Highly exothermic reactions related to aluminium oxidation, coupled to hydrogen evolution, have been recorded. The main drawback of hydrogen evolution is the formation of a stagnant layer over the heat exchangers surface, which can limit the ethanol vapour diffusion, thus reducing adsorption/condensation rate.

Aim of this work is the dynamic simulation of the operation of a small-scale multi-generation system, based on a Solid Oxide Fuel Cell (SOFC) micro-cogenerator (μCHP) coupled to an adsorption chiller, to provide electric and cooling energy to a telecommunication shelter. The dynamic simulation model has been implemented in TRNSYS environment. The μCHP has nominal electric power of 2.5 kW and its thermal output is used to drive a thermally driven adsorption chiller, with nominal cooling power of 10 kW. The performance of both components were experimentally validated under controlled lab conditions. The developed model allowed to optimize the system configuration and to perform an energy and environmental analysis. This analysis demonstrated the possibility of achieving global energy efficiency up to 63% with a CO2 reduction proportional to the electric and cooling load of the telecommunication shelter.

In this study, the most promising working pairs are evaluated for utilization in thermal driven adsorptive heat pumping, air conditioning and refrigeration applications employing water, ethanol and methanol as refrigerant. With this aim, a comparative study was carried out for different currently available (silica gels, zeolites, aluminophosphates, activated carbons) and recently developed materials (composite adsorbents). A simple mathematical model was developed in order to evaluate the performance of various working pairs for different sorption cycles. Among the considered adsorbents, the Mitsubishi product AQSOA-FAM-Z02, the composite adsorbents LiBr-silica and CaCl2-silica appeared the best water adsorbents for air conditioning and heat pumping purpose, providing heating/cooling COP up to 1.62/0.71 and heating/cooling enthalpy up to 1080/570 kJ kg-1. Also the LiCl-silica/methanol working pair showed high performance for air conditioning cycles, especially in terms of cooling enthalpy (Qev = 640 kJ kg-1). The composite LiBr-silica showed to be the most promising methanol and ethanol sorbent for refrigeration purpose, permitting cooling COP in the range 0.53-0.59 and cooling enthalpy in the range 180-360 kJ kg-1. The noticeable influence of the metal-to-adsorbent mass ratio on the sorption cycle performance was also demonstrated, showing that utilization of compact finned tube aluminum heat exchanger types (typical mmet/mads = 0.9-1.6) allows a 15-30% cooling COP higher than a traditional stainless steel tube-and-shell exchanger (mmet/mads = 2.4-3.1). Additionally, some brief dynamic considerations are done for most interesting working pairs.

In this paper, an innovative adsorptive chiller based on 3 hybrid adsorbers is presented as well as results of the first testing campaign performed under real HVAC operating conditions. The prototype presents two main innovative features aimed to achieve high values of cooling power density: (i) a new architecture, with 3 adsorbers connected to a single evaporator and condenser, that allows to perform an advanced machine’s management strategy employing unbalanced durations of the isobaric ads-/desorption steps, (ii) hybrid adsorbers realized embedding microporous Silica Gel loose grains into aluminium finned flat tube heat exchangers previously coated with the Mitsubishi AQSOA FAM Z02 sorbent. Water was selected as refrigerant while up to now the machine operates without any mass/heat recovery. A first testing campaign has been carried out at ITAE labs by a test bench specifically developed for thermally driven chillers. Influence of the cycle time as well as the temperature difference between condenser (T M ) and evaporator (T L ) on the overall performance were highlighted. The experimental measurements showed that the chiller is able to deliver an average cooling power (ACP) ranging between 3.4 and 4.4 kW, a volumetric cooling power (VCP) of 7.25–9.36 kW/m 3 , with a COP of 0.3–0.35 at T H = 90 °C, T L ∼ 15–18 °C and T M ∼ 25–28 °C.

Development of advanced heating systems, able to reduce the energy consumption of buildings is still an open issue. Different technologies, either already at commercial level or in a pre-commercial phase, are available. Among them, heat pumps and fuel cells represent good options, thanks to their high efficiency and flexibility of operation. The present paper analyses one of the possible ways to integrate a heat pump with a micro-Combined Heat and Power (CHP) based on Solid Oxide Fuel Cell (SOFC) technology, in order to increase the overall efficiency of the building heating system. Three different heat pumping technologies (namely vapour compression, absorption and adsorption) have been employed. Starting from performance data of commercial appliances (vapour compression and absorption heat pumps) and from performance experimentally measured at the CNR ITAE for appliances at prototyping level (adsorption heat pump and SOFC), a numerical model has been developed in TRNSYS. Simulations performed demonstrated that the overall yearly efficiency can be improved up to 30%, exploiting the heat released by the micro CHP to reduce the heat produced by the heat pump.

Hydrothermal aging of zeolites is an irreversible change of adsorbent surface characteristics due to repeated cyclic adsorption and desorption of water resulting in, among others, reduced adsorption capacity and kinetics of adsorption.

As described in Chap. 1, one of the major adsorber heat exchanger design requirements is the reduction of the ratio between the heat capacity of the adsorber heat exchanger material as well as its heat transfer medium’s holdup and the heat capacity of the applied adsorbent. This results in enhancing the coefficient of performance of the adsorption heat pump and increases the obtainable specific heating or cooling power.

In this work, adsorbent coatings on aluminum surfaces were prepared by dip-coating method starting from a water suspension of SAPO-34 zeolite and a silane-based binder. Silane-zeolite coatings morphology and surface coverage grade were evaluated by scanning electron microscopy. Adhesive and mechanical properties were evaluated by peel, pull-off, impact and micro-hardness tests, confirming the good interaction between metal substrate, binder and zeolite. Adsorption equilibrium and kinetics of water vapour adsorption on the adsorbent coating were studied in the range T = 30–150 °C and pH2O = 11 mbar using a CAHN 2000 thermo-balance. It was found that, in the investigated conditions, the organic binder doesn't affect the water adsorption capacity and adsorption kinetics of the original SAPO-34 zeolite. Subsequently, the zeolite coating was applied on a finned flat-tubes aluminum heat exchanger realizing a full-scale AdHEx with an uniform adsorbent coating 0.1 mm thick and a metal/adsorbent mass ratio = 6. The cooling capacity of the realized coated AdHEx was measured by a lab-scale adsorption chiller under realistic operating conditions for air conditioning applications. The coated AdHEx produced up to 675 W/kgads specific cooling power with a cycle time of 5 min. Adsorption stability of the coated adsorber subjected to 600 sorption cycles was successfully verified.

An adsorbent material consolidated in form of coating could present poor mechanical stability if a proper binder and/or an optimized binder content are not adopted in the coating formulation. Mechanical stability of the adsorbent coating may be affected by different typologies of mechanical stresses during its lifetime (vibrations, impacts, etc.). For this reason, a single mechanical test is not sufficient to prove completely the overall mechanical stability of the coated layer.