Development of media for dynamic latent heat storage for the low-temperature range. Part 1: Thermal analyses of selected salt hydrate systems

Phase change temperatures and phase change enthalpies of seventeen salt hydrates, three double salts, and four eutectics were measured thermodynamically and the results reported herein. Good results were obtained, especially for congruently melting salt hydrates. Incongruently melting salt hydrates appear less suitable for heat storage applications. The influence of the second phase - water, acid and hydroxide - to the latent heat is described. From these results, basic values of the working temperatures and storage capabilities of various storage media compositions may be derived

Morphological and Structural Evaluation of Hydration/Dehydration Stages of MgSO4 Filled Composite Silicone Foam for Thermal Energy Storage Applications

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

Identification of best available thermal energy storage compounds for low-to-moderate temperature storage applications in buildings

Award-winning paper at III International Congress and V National on Sustainable Construction and Eco-Efficient Solutions (CICSE) March 2017Over the last 40 years different thermal energy storage materials have been investigated with the aim of enhancing energy efficiency in buildings, improving systems performance, and increasing the share of renewable energies. However, the main requirements for their efficient implementation are not fully met by most of them. This paper develops a comparative review of thermophysical properties of materials reported in the literature. The results show that the highest volumetric storage capacities for the best available sensible, latent and thermochemical storage materials are 250 MJ/m3, 514 MJ/m3 and 2000 MJ/m3, respectively, corresponding to water, barium hydroxide octahydrate, and magnesium chloride hexahydrate. A group of salt hydrates and inorganic eutectics have been identified as the most promising for the development of competitive thermal storage materials for cooling, heating and comfort applications in the short-term. In the long-term, thermochemical storage materials seem promising. However, additional research efforts are required.Identificación de los mejores compuestos disponibles de almacenamiento de energía térmica para aplicaciones de baja a moderada temperatura en edificación. En los últimos 40 años se han investigado diferentes materiales de almacenamiento térmico con el objetivo de mejorar la eficiencia energética en los edificios, mejorar el rendimiento de sistemas y aumentar el uso de renovables. Sin embargo, la mayoría no cumple los principales requisitos para su eficiente implementación. Este artículo desarrolla una revisión de las propiedades termofísicas de los materiales existentes en la literatura. Los resultados muestran que las mayores capacidades de almacenamiento volumétrico para los mejores materiales de almacenamiento sensible, latente y termoquímico son 250 MJ/m3, 514 MJ/m3 y 2000 MJ/m3, respectivamente, correspondientes a agua, hidróxido de bario octahidratado y cloruro de magnesio hexahidratado. Un conjunto de sales hidratadas y eutécticos han sido identificados como los más prometedores para el desarrollo de materiales competitivos para aplicaciones de enfriamiento, calefacción y confort a corto plazo. A largo plazo, el almacenamiento termoquímico parece prometedor. Sin embargo, investigación adicional es requerida.Fondo Europeo de Desarrollo Regional SOE1/P3/P0429EUMinisterio de Educación, Cultura y Deportes FPU14/06583Ministerio de Economía y Competitividad BES-2015-0703149Ministerio de Economía y Competitividad CTQ2014-52763-C2-2-RMinisterio de Economía y Competitividad CTQ2017- 83602-C2-2

Polyvinyl Alcohol-salt Hydrate Mixtures as Passive Thermal Energy Storage Systems

AbstractInorganic salt hydrates are promising candidates as latent heat storage materials entailing, for example, a high thermal energy storage density and cheap price [1,2] in spite that they have many handicaps. For almost all applications, Phase change materials (PCMs) have to be encapsulated, that is, they have to be hermetically sealed within barrier containments, preferably within small microcapsules. Encapsulation improves heat transfer, cycling stability, and material compatibility with the environment. However, no attempt has been completely successful to microencapsulate salt hydrates so far due to the high surface polarities of these substances, edge alignment effects, their tendency to alter their water content [3]. This work is aimed to encapsulate some commonly used salt hydrates; sodium sulphate decahydrate (Na2SO4.10H2O) and calcium chloride hexahydrate (CaCl2.6H2O) in a hydrophilic polymer; polyvinyl alcohol (PVA) stably for passive thermal energy storage systems. So that an economically beneficial application mean will be validated

Increasing thermal mass in lightweight dwellings using phase change materials – a literature review

The number of houses of lightweight timber or steel frame construction being built over recent years has increased significantly. These buildings have low thermal mass and may be subject to large temperature fluctuations and particular overheating during the summer and this problem is set to get worse with the changing climate. Researchers have been investigating the use of PCMs (phase change materials) for improving thermal mass in lightweight buildings and found them to be effective. However, until recently, various problems have prevented products from entering the commercial market. In the last few years microencapsulated paraffin PCMs have been developed that are easy to use and building products are now available to buy containing these materials. Although there is significant academic research relating to PCMs for thermal buffering in lightweight buildings, there is a lack of field trials and case studies of PCMs in buildings in use. There is also a lack of information and guidance for designers and building owners. Recommendations are made for further research to discover the viability of uptake for PCM wallboard technology and the provision of information about the benefits of the products to the public and industry professionals

Accelerating the hydration reaction of potassium carbonate using organic dopants

Potassium carbonate has recently been identified as a promising candidate for thermochemical energy storage. However, as for many salt hydrates, the reaction kinetics is limited, and moreover, the hydration transition is kinetically hindered due to a metastable zone, involving limited mobility. This work aims to improve mobility by using organic potassium dopants, it shows that doping with potassium-formate and -acetate, can accelerate the hydration reaction. It has been shown that these dopants can enhance the hydration rate by two mechanisms i.e. introducing mobility due to adsorption of more water or introducing more surface area, where water adsorption can occur. This work opens up new possibilities for organic dopants to enhance the performance of salt hydrates.</p

PHYSICOCHEMICAL PROBLEMS CONNECTED WITH PHASE CHANGE MATERIALS

The physicochemical problems and some results of the investigation of latent heat storage materials, first of all salt hydrates such as sodium sulphate decahydrate, calcium chloride hexahydrate disodium hydrogen phosphate dodecahydrate and sodium acetate trihydrate are briefly reviewed