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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 efficient utilization of renewable energy sources should rely on the exploitation of a mix of thermal and electric energy rather than relying on a single energy source. One way to apply this shared generation concept to space heating/cooling and refrigeration in both residential and industrial sector is through hybrid sorption-compression chillers. However, the experience on these systems is still limited and therefore their design and optimization require some efforts. Starting from the experimental experience on the testing of different hybrid cascade chillers, and integrating the measurement with a dynamic model, some considerations on the sizing, design and optimization of hybrid thermal-electric chillers are reported. In particular, design conditions of pre-commercial or commercial systems are evaluated and optimization at different levels is proposed, i.e. on the core components (through the proper design of relative capacities of the units in the cascade and through proper selection of the refrigerant), on the auxiliaries, to reduce their electricity consumption, and on the overall management of the hybrid chiller. Results demonstrated that the higher is the operating temperature lift between evaporator and condenser the higher are the achievable energy savings of a cascade chiller.

A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of this paper is to identify some key aspects to be considered when scaling up the module from lab-scale to full-scale using different performance indicators calculated in both charge and discharge. Different normalization methods were applied to allow an appropriate comparison of the results at both scales. As a result of the scaling up, the theoretical energy storage capacity increases by 52% and 145%, the average charging power increases by 21% and 94%, while the average discharging power decreases by 16% but increases by 36% when mass and volume normalization methods are used, respectively. When normalization by the surface area of heat transfer is used, all of the above performance indicators decrease, especially the average discharging power, which decreases by 49%. Moreover, energy performance in charge and discharge decreases by 17% and 15%, respectively. However, efficiencies related to charging, discharging, and round-trip processes are practically not affected by the scaling up. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 768824 (HYBUILD). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018-102431-T). This work is partially supported by ICREA under the ICREA Academia programme.

In the present paper, the numerical modeling of an innovative latent thermal energy storage unit, suitable for direct integration into the condenser or evaporator of a heat pump is presented. The Modelica language, in the Dymola environment, and TIL libraries were used for the development of a modular model, which is easily re-usable and adaptable to different configurations. Validation of the model was carried out using experimental data under different operating modes and it was subsequently used for the optimization of a design for charging and discharge. In particular, since the storage unit is made up of parallel channels for the heat transfer fluid, refrigerant, and phase change material, their number and distribution were changed to evaluate the effect on heat transfer performance.

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 importance of Thermal Energy Storage (TES) inside efficient and renewables-driven systems is growing. While different technologies from traditional sensible TES are entering the market or moving towards commercialisation, a common basis for fair comparison and evaluation of these systems is lacking. Aim of the present paper is the definition of a set of KPIs that can be used for the comparative analysis of different TES. A review of methodologies used for the definition of KPIs in different sectors was realised and a novel methodology, based on the comparative assessment of literature analysis and evaluation of technology roadmaps was proposed. According to this methodology, the technical, socio-economic and environmental constraints defined by researchers and policy makers were identified and translated into KPIs. The set of parameters suggested was then applied to different cases studies within the same application, namely covering heating demand in residential buildings. The different technologies were compared and the results evaluated: a significant non-uniformity in the data available and the way they are presented was found, mainly linked to the different level of maturity of the technologies investigated. This strongly confirmed the need for a shared framework of data definition and reduction. Nonetheless, it was possible to calculate the majority of parameters and derive some general trends, thus proving the effective usefulness of the KPIs defined. (C) 2019 Elsevier B.V. All rights reserved.

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.

Increasing the energy efficiency of residential and non-residential buildings is a crucial point towards the development of the sustainable cities of the future. To reach such a goal, the commonly employed intervention measures (for instance, on facades and glass) are not sufficient and efforts in reaching a fully renewable energy generation are mandatory. In this context, this paper discusses the applicability of a system with solar and biomass as the main energy sources in different climates for heating, cooling, domestic hot water and electricity generation in office buildings. The energy system includes solar thermal collectors with thermoelectric generators, a biomass boiler, a reversible heat pump/organic Rankine cycle and an adsorption chiller. The results showed that the system can operate with a share of renewables higher than 70% for all energy needs, with up to 80% of the overall energy demand supplied only by solar and biomass sources even in the northern locations. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 814945 (SolBio-Rev)

The buildings sector is one of the least sustainable activities in the world, accounting for around 40% of the total global energy demand. With the aim to reduce the environmental impact of this sector, the use of renewable energy sources coupled with energy storage systems in buildings has been investigated in recent years. Innovative solutions for cooling, heating, and domestic hot water in buildings can contribute to the buildings' decarbonization by achieving a reduction of building electrical consumption needed to keep comfortable conditions. However, the environmental impact of a new system is not only related to its electrical consumption from the grid, but also to the environmental load produced in the manufacturing and disposal stages of system components. This study investigates the environmental impact of an innovative system proposed for residential buildings in Mediterranean climate through a life cycle assessment. The results show that, due to the complexity of the system, the manufacturing and disposal stages have a high environmental impact, which is not compensated by the reduction of the impact during the operational stage. A parametric study was also performed to investigate the effect of the design of the storage system on the overall system impact. This project received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 768824 (HYBUILD). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018-102431-T). 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.

This paper introduces a first order incremental sigma-delta modulator for a 2-stage ADC and targets the use in image sensors. We applied a “Digitally Implemented Feed-Forward” (DIFF) technique and refined it with an assumption that the input signal is constant during the conversion. The modulator is fabricated in a test chip with extended counting SAR ADC. Experimental results show a linearity of |DNL| < 1 with 12-bit output code, which indicates that our design achieves 12-bit linearity without code error.

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.

In this study, the definition of a new methodology for a preliminary evaluation of the working boundary conditions under which a seasonal thermal energy storage (STES) system operates is described. The approach starts by considering the building features as well as the reference heating system in terms of solar thermal collectors’ technology, ambient heat sinks/source, and space heating distribution systems employed. Furthermore, it is based on a deep climatic analysis of the place where the STES needs to be installed, to identify both winter and summer operating conditions. In particular, the STES energy density is evaluated considering different space heating demands covered by the STES (ranging from 10% up to 60%). The obtained results demonstrate that this approach allows for the careful estimation of the achievable STES density, which is varies significantly both with the space heating coverage guaranteed by the STES as well as with the ambient heat source/sink that is employed in the system. This confirms the need for careful preliminary analysis to avoid the overestimation of the STES material volume. The proposed approach was then applied for different climatic conditions (e.g., Germany and Sweden) and the volume of one of the most attractive composite sorbent materials reported in the literature, i.e., multi-wall carbon nanotubes (MWCNT)-LiCl, using water as the working fluid, needed for covering the variable space heating demand in a Nearly Zero Energy Building (NZEB) was calculated. In the case of Swedish buildings, it ranges from about 3.5 m3 when 10% of the space heating demand is provided by the STES, up to 11.1 m3 when 30% of the space heating demand is provided by the STES.

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.

The decarbonization of the building sector cannot preclude from the vast diffusion of renewable-sourced polygeneration systems for covering both heating and cooling demand. In this context, this study shows the potentialities of a system based on solar thermal collectors, a biomass boiler and an innovative reversible hybrid heat pump/ORC concept for addressing heating, cooling and domestic hot water demand of residential buildings. The potential is investigated in three cities (Madrid, Berlin and Helsinki), representative of the different European climates. The share of renewables in different seasons and building typologies is presented and the possibility of obtaining a 100% renewable system when the solution proposed is installed in new and renovated buildings is discussed. The results show that in standard multi-family houses, up to 70% of heating demand and 100% of cooling demand can be covered by the system in warmer climates and up to 60% share of renewables can be reached in Northern climates. Moreover, the flexible configuration of the system shows the potential for the application in the future energy system of the EU. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 814945 (SolBio-Rev). The authors at the University of Lleida 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.

The development of renewable energy sources (RES) to achieve the UN Sustainable Development Goals of a 100% RES-based energy system has driven a lot of research on batteries for electric vehicles and stationary applications, to further support the RES penetration. Batteries are strongly linked to the thermal conditions at which they operate, therefore the study and adequate implementation of a correct thermal management of batteries is essential for their better deployment and use. But this is a relatively new research topic with growing interest in recent years. This paper presents a bibliometric analysis of battery thermal management systems to understand the trends, assess the state-of-the-art, and identify research gaps. Results show that most research is carried out in lithium-ion batteries, and that the thermal managements systems studied are air cooling, liquid cooling, and phase change materials as passive systems or in combination with air and liquid cooling ones. The biggest research gaps are the lack of studies on other battery types and a clear comparison among these kinds of thermal management systems. This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31 - MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) (RED2018-102431-T). The authors at the University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group GREiA (2017 SGR 1537). GREiA is a 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.

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.

Hot potable water preparation in ships requires lots of energy from the power plant; this is particularly true in modern cruise ships with a high demand of potable water for people, restaurants, spa and pools. Usually the required amount of hot water is instantly produced using a number of different energy sources available on board. However, the use of direct heaters on peak demand conditions increases fuel consumption and greenhouse gas emissions. This is especially important in the case of ship in port configuration, due to the reduced number of active engines and therefore the reduced amount of waste heat from the cooling line usually employed for this task. This paper investigates possible solutions to size a hot water thermal storage in order to compensate the mismatch between heat generation during cruise and heat required during ship in port configuration. The performances of different solutions are compared using dynamic thermal simulations of the ship’s hot water distribution system with different regimes and time dependent heat requirements. Moreover it will be introduced the use of PCM materials with the aim to further improve system’s performance.

In the present work, two different types of heat exchangers are experimentally compared, namely a fin-and-tubes custom made HEX and a commercial asymmetric plate heat exchanger, for the application with phase change materials. In particular, the two devices were tested in a specifically designed testing rig located at CNR-ITAE and suitable for the characterization of thermal energy storages. The testing bench allows simulating a heat source up to 100°C (e.g. solar thermal collectors, low-grade waste heat) and to set the desired discharge temperature in the range 20°C-80°C. The phase change material with which the exchangers were filled, is a commercial paraffin (Plus ICE A82), having a nominal melting temperature of 82°C. The experimental results on charge and discharge tests, realized with the same protocol, were used for a comparison of the systems, through the identification of suitable performance figures and Key Performance Indicators, such as material-to-metal ratio, heat storage density, maximum and average power achievable and effectiveness of the system. The results show that, for the tested material, characterised by a very low thermal conductivity (i.e. about 0.2 W/mK), the selected plate heat exchanger allows a better exploitation of the heat stored inside the material, letting at the same time to reach a power output in the range 1-10 kW.

The aim of this paper is to study the equilibrium and dynamics of water adsorption on a commercial silica gel Siogel. This adsorbent has recently been suggested and tested for adsorptive transformation and storage of low temperature heat. The original data on the water vapour equilibrium and dynamics are compared with those earlier reported for the Fuji silica RD. This database can be used for theoretical analysis, mathematical modeling and evaluation of adsorptive cycles based on the working pair “water – Siogel” and driven by heat from renewable heat sources.

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.

Hybrid sorption-compression systems are gaining interest for heating/cooling/ refrigeration purposes in different applications, since they allow exploiting the benefits of both technologies and a better utilization of renewable sources. However, design of such components is still difficult, due to the intrinsic complexity of the systems and the lack of reliable models. In particular, the combination of adsorption-compression cascade unit has not been widely explored yet and there are no simulations or sizing tools reported in the literature. In this context, the present paper describes a model of a hybrid adsorption-compression system, realised in Modelica language using the commercial software Dymola. The models of the main components of the sorption and vapour compression unit are described in details and their validation presented. In addition, the integrated model is used for proving the feasibility of the system under dynamic realistic conditions and an example of the technical sizing that the model is able to accomplish is given.

Sorption thermal energy storage (STES) technology, belonging to the wider class of thermochemical TES, represents a promising alternative to common sensible and latent TESs, especially for applications at low-medium temperature (i.e. below 130 °C). The interest towards this technology is confirmed by the huge amount of research and development activities ongoing, represented by scientific publications as well as funded projects and international working groups. In such a context, the present paper reports about the most recent activities in the STES field. Particularly, it focuses on the analysis of innovative sorbent materials currently under development, comprising liquid absorption, physical adsorption, chemical reactions in pure salts and composite sorbents. Analysis of critical issues like achievable storage density, stability and corrosiveness were reported for each sorbent material. Furthermore, prototypes recently developed for each of the sorbent classes above reported were presented, highlighting the achievable performance, with particular attention towards the TES density attained under typical working conditions for heat and cold storage applications, both with open and closed TES systems. Finally, the most recent international activities focusing on the further development of STES, to help achieving higher Technology Readiness Level (TRL) were reported. These mainly comprise funded R&D projects and international working groups supported by intergovernmental organizations and research and innovations alliances.

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.

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.

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 need for innovative heating and cooling systems to decarbonize the building sector is widely recognized. It is especially important to increase the share of renewables at building level by maximizing self-consumption and reducing the primary energy demand. Accordingly, in the present paper, the results on a wide experimental campaign on a hybrid system are discussed. The system included a sorption module working as the topping cycle in a cascade configuration with a DC-driven vapor compression heat pump. A three-fluids heat exchanger with a phase change material (PCM), i.e., RT4 with nominal melting temperature of 4 °C, was installed on the evaporator side of the heat pump, for simultaneous operation as thermal storage and heat pumping purposes. The heat pump was connected to a DC-bus that included PV connection and electricity storage (batteries). Results showed that the energy efficiency of the heat pump in cascade operation was double compared to compression-only configuration and that, when simultaneously charging and discharging the latent storage in cascade configuration, no penalization in terms of efficiency compared to the compression-only configuration was measured. The self-sufficiency of the system was evaluated for three reference weeks in summer conditions of Athens climate and it was found that up to 100% of the electricity needed to drive the system could be self-produced for a modest cooling demand and up to 67% for the warmer conditions with high cooling demand. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 768824 (HYBUILD). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investi-gación (AEI) (RED2018-102431-T). 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.

The energy demand of industries accounts for about 30–35% of world yearly energy consumption, a relevant percentage is due to the need of heating and cooling demand. Solar heating and cooling technologies can be integrated in industrial processes to reduce the fossil fuels consumption as well as the related greenhouse gas emissions. This paper reports the experimental analysis of a novel hybrid sorption-compression chiller for cooling and refrigeration purposes in cascade layout, which uses silica gel/water for the sorption cycle and a low Global Warming Potential (GWP) refrigerant, i.e. propylene for the compression cycle. The experimental results highlighted the flexibility of the system in terms of performances and operating conditions, these were compared to the theoretical performances and it was found out that electricity energy savings from 15% to 25% can be achieved when using the hybrid system over a compression one with the same cooling capacity. The results were converted in performance maps and processed in a statistical model, in order to get a simplified expression for determining the overall performances of the hybrid system through variables that could be measured by a final user, such as the operating temperatures. Optimization strategies were identified for a further enhancement of the performance of the chiller, i.e. the reduction of the electricity consumption, by controlling the intermediate temperature (evaporation temperature of the sorption chiller) through sorption cycle management and the use of variable speed of the pumps in all the circuits to reduce the parasitic consumption especially at low part loads.

With the aim of contributing to achieving the decarbonization of the energy sector, the environmental impact of an innovative system to produce heating and domestic hot water for heating demand-dominated climates is assessed is evaluated. The evaluation is conducted using the life cycle assessment (LCA) methodology and the ReCiPe and IPCC GWP indicators for the manufacturing and operation stages, and comparing the system to a reference one. Results show that the innovative system has a lower overall impact than the reference one. Moreover, a parametric study to evaluate the impact of the refrigerant is carried out, showing that the impact of the overall systems is not affected if the amount of refrigerant or the impact of refrigerant is increased. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 768824 (HYBUILD). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31–MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades–Agencia Estatal de Investigación (AEI) (RED2018-102431-T). 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 the present paper design, realization and testing of a novel small scale adsorption refrigerator prototype based on activated carbon/ethanol working pair is described. Firstly, experimental activity has been carried out for identification of the best performing activated carbon available on the market, through the evaluation of the achievable thermodynamic performance both under air conditioning and refrigeration conditions. Once identified the best performing activated carbon, the design of the adsorber was developed by experimental dynamic performance analysis, carried out by means of the Gravimetric-Large Temperature Jump (G-LTJ) apparatus available at CNR ITAE lab. Finally, the whole 0.5 kW refrigerator prototype was designed and built. First experimental results both under reference air conditioning and refrigeration cycles have been reported, to check the achievable performance. High Specific Cooling Powers (SCPs), 95 W/kg and 50 W/kg, for air conditioning and refrigeration respectively, were obtained, while the COP ranged between 0.09 and 0.11, thus showing an improvement of the current state of the art.

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.

The integration of sorption systems on-board fishing vessels has been explored in the last decade, but the limitations in power density and temperature levels achievable have hindered their application. In the present paper, the integration of hybrid sorption–compression systems was evaluated. Different shipping vessels and routes in seas and oceans were considered in the analysis, with engine powers from 190 kW to 500 kW. The feasibility of series and cascade configurations was studied and the possible benefits, in terms of fuel and CO2 savings, were evaluated. The analysis, which also considered the payload due to the extra fuel needed to transport the equipment for refrigeration, showed that up to 75% savings can be obtained, with CO2 emissions avoided up to 20 t/y., peer-reviewed

Thermal energy storage (TES) is a key technology to enhance the efficiency of energy systems as well as to increase the share of renewable energies. In this context, the present paper reports a literature review of the recent advancement in the field of adsorption TES systems. After an initial introduction concerning different heat storage technologies, the working principle of the adsorption TES is explained and compared to other technologies. Subsequently, promising features and critical issues at a material, component and system level are deeply analyzed and the ongoing activities to make this technology ready for marketing are introduced.

At present, the majority of thermodynamic cycles of heat engines are high-temperature cycles that are realized by internal combustion engines, steam and gas turbines, etc. (Cengel, Boles in Thermodynamics: an engineering approach, 4th edn. McGray-Hill Inc., New York, 2002). Traditional heat engine cycles are mainly based on burning of organic fuel that may result in dramatic increase of CO2 emissions and global warming. The world community has realized the gravity of these problems and taken initiatives to alleviate or reverse this situation. Fulfilment of these initiatives requires, first of all, the replacement of fossil fuels with renewable energy sources (e.g. the sun, wind, ambient heat, natural water basins, soil, air). These new heat sources have significantly lower temperature potential than that achieved by burning of fossil fuels which opens a niche for applying adsorption technologies for heat transformation and storage (Pons et al in Int J Refrig 22:5–17, 1999).

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.

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%.

In the present work, an experimental study on a lab-scale adsorption refrigerator, based on activated carbon/ethanol working pair is reported. An extensive testing campaign has been carried out at the CNR ITAE laboratory, with multiple aims. First, the performance has been evaluated in terms of both COP and Specific Cooling Power (SCP), under different boundary conditions, including both air conditioning and refrigeration applications. Attractive SCPs, up to 180 W/kg and 70 W/kg for air conditioning and refrigeration, respectively, were measured. Under the same conditions, COP between 0.17 and 0.08 were obtained. In addition, different management strategies, namely, heat recovery between adsorbers and re-allocation of phase durations, were evaluated to identify their influence on the system. Both strategies confirmed the possibility of increasing COP and SCP up to 40% and 25%, respectively. Moreover, a design analysis based on the experimental results has been carried out, to suggest possible improvements of the system. The obtained results demonstrated the possibility of employing a non-toxic refrigerant like ethanol reaching performance comparable with other harmful refrigerants like ammonia and methanol.

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.