Porous materials in building energy technologies—a review of the applications, modelling and experiments

Improving energy efficiency in buildings is central to achieving the goals set by Paris agreement in 2015, as it reduces the energy consumption and consequently the emission of greenhouse gases without jeopardising human comfort. The literature includes a large number of articles on energy performance of the residential and commercial buildings. Many researchers have examined porous materials as affordable and promising means of improving the energy efficiency of buildings. Further, some of the natural media involved in building energy technologies are porous. However, currently, there is no review article exclusively focused on the porous media pertinent to the building energy technologies. Accordingly, this article performs a review of literature on the applications, modelling and experimental studies about the materials containing macro, micro, and nano-porous media and their advantages and limitations in different building energy technologies. These include roof cooling, ground-source heat pumps and heat exchangers, insulations, and thermal energy storage systems. The progress made and the remaining challenges in each technology are discussed and some conclusions and suggestions are made for the future research

Geometrical modelling and numerical analysis of thermal behaviour of textile structures

The thermal properties of fabric are an important factor in the understanding of the thermo-physiological comfort of clothing. The principal aim of this research was to develop novel numerical methods, Graphical User Interface (GUI) plug-ins and experimental setup to evaluate the effective thermal conductivity and thermal resistance of different textile structures which has significant impact on the thermal comfort of clothing. The numerical methods also include the analysis of the effect of fibre orientation, thermal anisotropy of fibre, temperature dependent thermal conductivity and fibre volume fraction on the effective thermal conductivity and thermal resistance of textile fabrics. The research covers the development of geometrical models of woven, knitted, nonwoven and the composites fabric structures, evaluation of their thermal properties by using finite element method, creation of user friendly plug-ins and the extended application tools. Micro and mesoscopic scale modelling approaches were used to investigate the effective thermal conductivity and thermal resistance of textile structures. Various techniques, including scanning electron microscopy, x-ray microtomography and experimental method have been adopted to obtain the actual 3D dimensional parameters of the fabrics for finite element analysis. Research revealed that, the thermal anisotropy of fibres, fibres material orientation and temperature dependent thermal conductivity of fibre have significant impact on the effective thermal conductivity of fabrics because experimental and simulated results were highly correlated with the consideration of above mentioned factors. In addition a unique technique has been developed in modelling fabric coated by microencapsulated phase change material for temperature stable textile and clothing system. User friendly GUI plug-ins have been developed to generate both microscopic and mesoscopic scale models for finite element analysis. The plug-ins were developed by using Abaqus/CAE as a platform. The GUI Plug-ins enable automatic model generation and property analysis of knitted fabrics and composites. Apart from finite element analysis of various fabric structures, an experimental device has been developed for testing thermal conductivity of fabrics which is capable of testing small sample size within very short period of time. The device was validated by commercial available apparatus for testing of fabric thermal conductivity

Gypsum plasterboards enhanced with phase change materials: a fire safety assessment using experimental and computational techniques

Phase Change Materials (PCM) can be used for thermal energy storage, aiming to enhance building energy efficiency. Recently, gypsum plasterboards with incorporated paraffin-based PCM blends have become commercially available. In the high temperature environment developed during a fire, the paraffins, which exhibit relatively low boiling points, may evaporate and, escaping through the gypsum plasterboard's porous structure, emerge to the fire region, where they may ignite, thus adversely affecting the fire resistance characteristics of the building. Aiming to assess the fire safety behaviour of such building materials, an extensive experimental and computational analysis is performed. The fire behaviour and the main thermo-physical physical properties of PCM-enhanced gypsum plasterboards are investigated, using a variety of standard tests and devices (Scanning Electron Microscopy, Thermo Gravimetric Analysis, Cone Calorimeter). The obtained results are used to develop a dedicated numerical model, which is implemented in a CFD code. CFD simulations are validated using measurements obtained in a cone calorimeter. In addition, the CFD code is used to simulate an ISO 9705 room exposed to fire conditions, demonstrating that PCM addition may indeed adversely affect the fire safety of a gypsum plasterboard clad building

An exploration on the performance of using phase change humidity control material wallboards in office buildings

In this study, a composite double-layer wallboard with shape-stabilized phase change humidity control materials (PCHCM) has been proposed for building usage. This novel PCHCM can absorb/release both heat and moisture to moderate indoor hygrothermal environment. Based on a numerical analysis in an office building in Wuhan (30.52°N, 114.32°E), China, the effects of PCHCM on both building energy consumption and indoor hygrothermal environment has been investigated. Firstly, a simulation model has been developed for the building integrated with PCHCM wallboards in EnergyPlus, combining both heat and moisture transfer finite solution algorithms. After a validation of the model, both heat and moisture transfer characteristics of the proposed composite wallboards were simulated, and its effects on indoor temperature, humidity and building energy consumption were analyzed. The simulation results showed that this novel PCHCM wallboard can effectively improve indoor hygrothermal environment, with reduced energy consumption by about 8.3% in summer and 24.9% in winter, comparing to the actually used materials in the case study building

Experimental and numerical studies of thermoregulating textiles incorporated with phase change materials

Phase change materials (PCMs) provide thermal management solution to textiles for the protection of wearer from extreme weather conditions. PCMs are the substances which can store or release a large amount of energy in the form of latent heat at certain melting temperature. This research reports practical and theoretical studies of textiles containing PCMs. Mono and multifilament filaments incorporated with microencapsulated phase change material (MPCM) have been developed through melt spinning process. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) have been performed for the characterisation of MPCM polypropylene filaments. The parameters for optimum fibre processing and their effect on mechanical properties of filaments with respect to the amount of MPCM have also been studied. A plain woven fabric has been constructed using the developed MPCM multifilament yarn. The heat transfer property of the multifilament yarn and fabric has been investigated using finite element method. The time dependent thermoregulating effect of yarn and fabric incorporated with MPCM has also been predicted according to the validated models. The synthesis of Nanocapsules containing mixture of paraffins and Glauber’s salt as PCM and its characterisation using DSC and SEM has also been carried out. Polypropylene monofilament incorporated with the nanoencapsulated paraffins was developed and its properties have been compared to its MPCM counterpart. Furthermore the developed nanocapsules were applied on a cotton fabric via a pad-dry-cure process and the resultant fabric was evaluated using DSC and SEM in comparison with MPCM treated fabric. The research work described in this thesis has established a better understanding of use of phase change materials in textiles, the evaluation and application. It is anticipated that this research will broaden the understanding and potential use of encapsulated phase change materials in textiles especially in the field of active smart textiles

Development and Evaluation of Phase Change Material-Enhanced Earthbag Buildings for Thermally Comfortable and Sustainable Temporary Housing in Nigeria: Numerical and Experimental Approach

Many developing countries face an increasing demand for affordable and sustainable housing, particularly for refugees and displaced communities that require temporary housing. However, there is a lack of research on the thermal comfort of such housing, which poses risks to vulnerable occupants, especially children. Existing studies on the thermal performance of shelters have predominantly focused on cold environments, neglecting hot climates, leaving this area of research underdeveloped. Earthbag buildings are promising options because of their low cost, sustainability, and ease of construction. However, indoor thermal comfort is often inadequate. This research aims to address this issue by developing and integrating phase change materials (PCM) into earthbag building to create a more comfortable living environment. The study began by fabricating earthbag blocks containing varying amounts of paraffin wax encapsulated in expanded perlite and graphite which was formed as PCM composite, to investigate the microstructural properties of the embedded PCM composite in soil, followed by testing the block thermal characteristics. Subsequently, an experimental analysis was conducted to understand the thermal properties of a wall embedded with optimum earthbag blocks. Two PCMs, namely A31 paraffin wax and Inertek26 powder microencapsulated, were incorporated into reduced-scale earthbag walls to create two distinct wall types: Wall-2_WA31 (a wall with A31 paraffin wax), and Wall-3_WInk26 (a wall with microencapsulated inertek26 powder). The performances of these PCM-integrated earthbag walls and Wall-1_baseline (a wall without PCM), were then monitored in an environmental chamber. To complement the experimental findings, a numerical model was developed using the EnergyPlus numerical simulation engine, employing the conduction finite difference (CondFD) approach and validated with experimental data. Through parametric analysis, the study identified the most effective PCM and the PCM supporting materials. Finally, a case study was presented, demonstrating the successful implementation of the optimum PCM-integrated earthbag walls (PCM-E wall) in a temporary housing unit in Maiduguri, Nigeria. This case study aimed to investigate the practical application and effectiveness of PCM-E wall in achieving optimal thermal comfort of temporary housing. The study revealed that the PCM and PCM composites exhibited favourable thermal stability, based on the Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) tests. The Scanning Electron Microscope (SEM) results suggest that the PCM was evenly dispersed within the pores of the expanded perlite (EP) material at a 50% EP to PCM weight ratio. Moreover, the thermal performance results of the PCM-integrated earthbag blocks demonstrate that integrating PCM into earthbag block significantly moderates inner surface block wall temperatures by 1.2 to 4.1°C compared to the reference block. The integration of PCM into earthbag walls demonstrated remarkable improvements in thermal performance. Notably, the thermal conductivity of the earthbag walls significantly decreased with PCM incorporation, with Wall-3_WInk26 having achieved the lowest thermal conductivity at 0.43 W/mK. PCM-enhanced walls exhibited stable inner wall temperatures, with maximum reductions of 2.4°C compared to the baseline, and a substantial reduction in heat flux by up to 63.76%. The time lag in reaching the peak inner wall temperature increased by 3-5 hours, enhancing thermal comfort. The study identified an optimal PCM transition temperature of 31°C. Furthermore, PCM integration outperformed insulation alone, and increasing PCM and insulation layer thickness optimized thermal performance. A numerical model validated these findings, supporting the conclusion that PCMs enhanced thermal mass, reduced temperature fluctuations, and improved energy efficiency in earthbag construction. When combined with night ventilation strategies, PCM walls eliminated the need for air conditioning and maintained indoor temperatures within the comfort range of 23-32°C. In the long term, PCM-enhanced earthbag walls demonstrated significant thermal comfort improvements, with 94% comfort hours over the summer period. This research offered a promising solution for affordable, energy-efficient housing in hot climates using local earthen materials and passive cooling techniques

A review of performance enhancement of PCM based latent heat storage system within the context of materials, thermal stability and compatibility

Phase change materials (PCM) with their high thermal storage density at almost isothermal conditions and their availability at wide range of phase transitions promote an effective mode of storing thermal energy. Literature survey evidently shows that paraffins and salt hydrates provide better thermal performance at competitive cost. However, the efficient utilization of latent heat storage is limited by low thermal conductivity, phase segregation, subcooling and container material compatibility with PCMs. This review paper is focused on classification of various PCMs, long term thermal stability of paraffins and salt hydrates; their compatibility with different container materials and thermal performance enhancement techniques adopted by various researchers such as influence of container shape, employment of fins and high conductivity additives, multi-PCM approach and PCM encapsulation on phase transition rates and thermal energy storage density. The conclusions obtained from critical assessment of research work carried out on latent heat storage will encourage using reliable PCM with compatible container material and an efficient geometric configuration to achieve maximum thermal utilization of PCM