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Composite thermochemical energy storage (TCES) represents an exciting field of thermal energy storage which could address the issue of seasonal variance in renewable energy supply. However, there are open questions about their performance and the root cause of some observed phenomena. Some researchers have observed the breakdown of particles in their production phase, and in their use. This study seeks to investigate the underlying cause of this breakdown. SEM and EDX analysis have been conducted on MgCl2 impregnated 13X zeolite composites of differing diameters, as well as LiX zeolite. This was done in order to study the level of impregnation of salt into the zeolitematrix, as well as the effect this impregnation process has on themorphology of the zeolite. Analysis was conducted using ImageJ software to study the effect of the impregnation process on the diameter of the particles. It has been found that a by weight impregnation concentration of magnesium chloride of 11.90% for the LiX zeolite, and 7.59% and 5.26% for the large diameter 13X zeolite and the small diameter 13X zeolite respectively has been achieved. It has been found that the impregnation process significantly affects themorphology of 13X zeolite particles, causing large fissures to form, and eventually resulting in the previously found breakdown of these particles. It has been verified that a primary factor influencing the breakdown of the 13X zeolite particles is the efflorescence and sub-fluorescence phenomena, which leads to a build-up of crystals in the zeolite pores. It has also been found that prolonged impregnation times and the use of high concentration salt solutions in the soaking process can induce significant crystal growth which also leads to the breakdown of these particles. Results demonstrate that LiX zeolite is the optimum host matrix choice in these conditions. These results will allow for the design of more resilient composite TCES particles. [ABSTRACT FROM AUTHOR]

• Smaller/lighter materials which dominate retrofit are poorly characterised in datasets. • Materials are poorly named, described, or are absent in LCA datasets. • LCA for retrofit may not yield reliable information for design decisions. • Embodied energy coefficients may be more reliable than embodied carbon ones. • Reporting only carbon could lead to externalisation of impacts, not avoidance. Low energy domestic retrofit consumes materials, such as insulation, membranes and glazing, with smaller quantities of structural timber, steel or concrete, which have associated embodied impacts from resource extraction, manufacture and end-of-life treatments. In retrofit design, coefficients for material embodied impacts vary widely between sources and can lead to different results in a life cycle energy or carbon analysis, and perhaps different material choices in retrofit implementation. This paper considers how and why results differ between sources, and whether such data is suitable for making climate-beneficial design decisions. Embodied energy and carbon coefficients for 18 key retrofit materials were obtained from two widely used LCA databases and their similarity was quantified. The data collected illustrates that 70% embodied energy and embodied carbon data is within 20%, but that 30% of data was more than 20% different. Consistency of product naming and the absence in the datasets of key retrofit materials are factors identified contributing to variation, and present real constraints in practice. Furthermore, this exercise showed that embodied impacts for the types of materials most prominent in retrofits are less-well characterised than other major construction materials, and presents another layer of uncertainty. The data showed embodied energy was more consistent between sources than embodied carbon. This raises doubts about the predominant use of embodied carbon over energy for such analyses and establishes that a focus on embodied carbon over embodied energy has less power to reduce greenhouse gas emissions than considering both metrics together. It is concluded that obtaining such data with confidence is challenging and requires expertise in LCA, and is therefore unlikely to be accessible to most retrofit designers. Datasets need to be more complete and offer higher confidence to ensure delivery of high quality and meaningful results for climate-beneficial design decisions. [ABSTRACT FROM AUTHOR]