The dissolution behaviour of poly(styrene-co-acrylonitrile) (SAN) was examined across a broad temperature range to identify the governing thermodynamic and kinetic factors. Two high-boiling solvents with contrasting affinities for SAN, namely diethyl succinate (DS, RED = 0.69) and triethyl citrate (TC, RED = 1.37), were selected to study dissolution below and above the SAN glass transition temperature (T-g approximate to 105 degrees C). Isothermal mixing calorimetry (30-150 degrees C) showed complete SAN dissolution in DS above 45 degrees C, with exothermic dissolution enthalpies decreasing from 20 J g(-)(1) at 45 degrees C to 6 J g(-)(1) at 120 degrees C, the latter reflecting polymer-solvent interactions once the glassy-rubbery transition no longer contributes. In TC, SAN did not dissolve at 30 degrees C and was only partially dissolved up to 80 degrees C; complete dissolution occurred only above T-g, with an enthalpy of similar to 6 J g(-)(1) at 120 degrees C. ATR-FTIR monitoring revealed strong effects of solvent quality and temperature on induction time. SAN chains appeared in solution after 480 s in DS but after similar to 5000 s in TC at 45 degrees C, evidencing significant segmental-relaxation limitation in TC. Above T-g, induction times sharply decreased to 120 s in DS and 360 s in TC at 120 degrees C. Isoconversional kinetic analysis showed that dissolution in DS above T-g is diffusion-controlled, with low activation energies (6-15 kJ mol(-)(1)). Below T-g, SAN dissolution transitions from segmental-relaxation-controlled (increasing to 41 kJ mol(-)(1)) to diffusion-controlled at higher conversion. Dissolution in TC below T-g exhibited even stronger relaxation control, with E-a reaching 116 kJ mol(-)(1) .

Dissolution/precipitation recycling is an environmentally friendly solution that could be potentially implemented for ABS recycling. In this paper, a set of useful calorimetric, spectroscopic, and rheological techniques and methods are presented to monitor in-situ the dissolution of the ABS matrix: poly(styrene-acrylonitrile) (SAN). In line with the Hansen solubility parameters, methyl ethyl ketone (MEK) has been selected to be a suitable solvent for SAN dissolution. Thermodynamic and kinetic aspects of the dissolution process were investigated by using calorimetry and in-situ ATR-FTIR spectroscopy. Through an isoconversional method, the effective activation energy and the main steps involved in the dissolution process were determined. A rheological characterization of the solution SAN-MEK was also performed to provide further information on the rheological behavior.

Salt hydrates are promising candidates for long-term thermochemical heat storage (TCHS) in the building environment. In such storage systems, the surplus of energy will be exploited in an endothermic reaction to dehydrate the salt hydrates. Once it is demanded, the stored energy will be released through an exothermic reaction by hydrating the salt, which results in an increase in the mass and temperature of salt particles as well as changes in the species of material. In order to construct an improved storage system, it is very important to deeply understand the details of the heat and mass transfer processes in the packed beds of salt hydrates. Poor heat (in the closed systems) and mass transfer (in open systems) can be the bottleneck in this technology. The main objective of this work is to investigate how heat transfer will be affected by applied pressure, particle size, and packing arrangement through calculating/measuring the effective thermal conductivity of the packed beds of salt hydrates. This is achieved by applying and developing a CFD-DEM model and by experimental measurements in a vacuum oven. Comparisons are carried out for the numerical results at low and high ambient pressures with the experimental measurements, which show a very good agreement. The obtained results show the effect of natural convection in the packed bed when the higher vapor pressure is applied.

The performance of solar-thermal conversion systems can be improved by incorporation of encapsulated phase change materials. In this study, for the first time, CrodathermTM 60 as a phase change material (PCM) was successfully encapsulated within polyurea as the shell supporting material. While preparing the slurry samples, graphite nanoplatelet (GNP) sheets were also incorporated to enhance the thermal and photothermal properties of the prepared materials. The morphology and chemical properties of these capsules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrum, respectively. The results show the spherical-like and core-shell structure of capsules with an average diameter size of 3.34 μm. No chemical interaction was observed between the core and the supporting materials. The thermal characteristics of the microencapsulated PCMs (MEPCMs), analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), indicate that the prepared samples with 0.1 weight percentage of GNP possess the latent heat of 95.5 J/g at the phase transition temperature of about 64 °C. Analyzing the rheological properties of the prepared slurry with 16 wt % of MEPCMs proves that the prepared material meet the requirements given by the heat transfer applications. The thermal storage capacity, good thermal stability, and improved photothermal performance of the prepared material make it a potential candidate for using in direct absorption solar thermal applications.

In our labs and pilot sites, a novel heat battery for dwellings and offices is being developed. Based on a thermochemical sorption reaction, space heating, cooling and generation of domestic hot water will eventually be demonstrated in an existing dwelling by using solar or waste heat in the CREATE project. Developments of the active materials, of the reactor and components, and of the system were mainly performed in the MERITS project, and results are briefly described. Upon wide-spread use, the technology of compact thermal storage can be the game changer in the transformation of our existing building stock towards near-zero energy buildings.

Long-term and compact storage of solar energy is crucial for the eventual transition to a 100% renewable energy economy. For this, thermochemical materials provide a promising solution. The compactness of a long-term storage system is determined by the thermochemical reaction, operating conditions, and system implementation with the necessary additional system components. Within the MERITS project a thermochemical storage (TCS) system is being demonstrated using evacuated, closed TCS modules containing Na2S as active material. The present modules are expected to reach a heat storage density of 0.18GJ/m3. In this paper, we discuss the different factors leading to this storage density, and argue that by further optimization of the selected reaction and architecture, the result may be improved to approximately 1GJ/m3, which would be a practical value for seasonal heat storage in buildings.

The IEA joint Task 42 / Annex 29 is aimed at developing compact thermal energy storage materials and systems. In Working Group B, experts are working on the development of compact thermal energy storage applications, in the areas cooling, domestic heating and hot water and industry. The majority of application projects were in the field of room heating and domestic hot water. In this article, an overview is given of a large number of applications. The storage technologies used in the applications are latent heat storage, open and closed solid sorption, liquid sorption and salt hydrates and composites thereof. On a broad front, a lot of progress was made in the development of components and systems, providing knowledge and experience regarding the design, numerical modeling, building, testing and economical assessing of components and storage systems. Most important findings are that the interaction of storage materials with the materials of components can be deciding for the technical feasibility, that a number of components, like reactor, heat exchangers and evaporators are less understood than initially thought and need more development, that the inclusion of storage materials in systems generate new challenges like the occurrence of non-condensable gases and thermo-mechanical effects and that standardized and simplified system approaches are needed.

Bottlenecks for realizing a commercial system for thermochemical heat storage (TCS) with hygroscopic salts are the chemical, physical and mechanical stability of the salt under operation conditions. Hence, improved knowledge of thermochemical materials (TCMs) is critical to spur progress in TCS system development. Sodium sulfide hydrates (Na2S.nH2O, n=0-9) are highly interesting as TCMs because they exhibit a high energy density under operation conditions and are potentially readily available and affordable. Preparation methods for well-defined nonahydrate and pentahydrate crystals of Na2S were developed and the resulting samples were subjected to cycling experiments under conditions representative for TCS. Before and after cycling, crystal samples were taken and characterized using techniques like SEM/TEM, XRD. Mechanical strength was evaluated using a salt bed stability test. Based on the extensive characterization of sodium sulfide hydrate salts, a method has been proposed to improve the stability of the salt by blending it with cellulose. First trials on these composites yielded promising results with respect to improved material stability.

A 3 kWh thermochemical heat storage (TCS) module was built as part of an all-in house system implementation focusing on space heating application at a temperature level of 40°C and a temperature lift of 20K. It has been tested and measurements showed a maximum water circuit temperature span (released by adsorption) of 20 – 51K which is by all means suitable for space heating.

Solar energy is capable of supplying enough energy to answer the total demand of energy in dwellings. However, because of the discrepancy between energy supply and energy demand, an efficient way of storing thermal energy is crucial. Thermochemical storage of heat in salt hydrates provides an efficient and compact way of storing solar energy. The properties of the salt hydrates determine the storage capacity, operating conditions and cost of the thermochemical storage system. In this paper an overview of the properties of the most promising candidates for thermochemical storage for our purposes is given.

Thermochemical materials (TCMs) are a promising solution for seasonal heat storage, providing the possibility to store excess solar energy from the warm season for later use during the cold season, and with that all year long sustainable energy. With our fixed bed, vacuum reactors using zeolite as TCM, we recently demonstrated long-term heat storage with satisfactory output power. For domestic application, however, it will be necessary to considerably increase storage density and to reduce system costs. In this paper, we discuss issues on system, component and material levels for realizing a commercially attractive system. We first discuss a modular, fixed bed concept with a hot water storage. We show that with proper dimensioning of TCM modules and hot water storage, one can obtain a system where daily storage and on-demand heat delivery can be arranged by the hot water storage, while demands on output power, power control and material stability during operation are relaxed as much as possible. We also discuss atmospheric and central reactor concepts, which may provide lower-cost TCS systems. An important issue on component level is the implementation of a low temperature source providing evaporation heat in winter. We discuss several options, including the application of solar collectors in winter. Heat storage density can be increased by an order of magnitude by applying hydration reactions of hygroscopic salts, but this introduces physical and chemical stability issues during repeated cycles of hydration and dehydration. We discuss several of these stability issues as well as possible stabilization in a composite TCM, which should also provide sufficient vapor and heat transport.

At this moment, the global energy consumption in buildings is around 40% of the total energy consumption in developed countries. Thermal energy storage (TES) is presented as one way to address this energy-related problem proposing an alternative to reduce the gap between energy supply and energy demand. One way to store energy is using thermochemical materials (TCM). These types of materials allow accumulating energy through a chemical process at low temperature, almost without heat losses. In addition, it is a stable way to perform the heat storage and TCM can be implemented for seasonal storage or/and long term storage. This study compares the cyclability, from the thermophysical point of view, CaCl2 which follows a chemical reaction and zeolite which follows a sorption process to be used as TCM for seasonal/long term storage. The main results show that the chemical reaction TCM is more energy-efficient than the sorption TCM. The CaCl2 calculated energy density is 1.47 GJ/m(3), being the best option to be considered to be used as TCM, even though the dehydration process of the zeolite is simpler and it occurs at higher temperatures its calculated energy density is only 0.2 GJ/m(3). (C) 2014 Elsevier Ltd. All rights reserved.

Thermochemical materials (TCM) are proposed for thermal energy storage as one of the future options to achieve lower energy consumption in buildings and other industrial applications, as well as to store energy from solar energy. In this study, the thermophysical properties of two TCM, CaCl2 and zeolite, are determined with TGA and DSC and samples are cycled 4 times with TGA. Results show that the material with the highest energy density is the salt, CaCl2. Moreover, both materials under study present noble cyclability.

Since January 2009, experts from the fields of material development and system integration are working together in the joint Task42/Annex24 to develop better materials for the compact storage of heat and to design, build and test systems in which these novel materials are being applied. In the Task, over 50 organisations from 17 countries all over the world collaborated, in national and international projects. These activities resulted in a varied collection of results, from new compact storage materials, through better testing and characterisation methods, to numerical methods to predict the performance of novel materials, of components and systems. This article introduces some of the developments in the Task.