Addition Of Phase Change Materials Research Articles

Metal Hydride Storage Systems: Approaches to Improve Their Performances

AbstractMetal hydrides provide a safe and efficient way to store hydrogen. However, current metal hydride storage systems, i.e., hydrides incorporated within a storage tank, are far from efficient. Depending on the design, (dis)charging rates may be very long. However, this can be significantly improved by implementing strategies tackling the issue of heat management at the level of: i) the metal hydride bed, and ii) the overall storage system design. This review summarises recent progress in tackling heat management of hydride systems. In this respect, modeling has emerged as a powerful tool. In particular, simulation results show that the compaction of hydride powders with binders and the use of metal foams are both effective in lifting the poor thermal conductivity of hydride beds. For tank designs, cylindrical shapes remain the preferred choice because of the flexibility and ease of supplementing heat management with fins and tubular heat exchangers. The addition of phase change materials to the hydride tank can lead to further heat storage, but any add‐on to simple hydride tanks can only lead to cumbersome systems. It is still a fine art to tune the thermal conductivity of hydride beds while selecting a suitable metal hydride alloy composition.

Thermal characteristics of cementitious building materials with carbon and PCM for improved heat storage performance

The thermal properties of cementitious building materials were analyzed by integrating phase change materials (PCMs) and carbon materials to improve their heat storage performance. Four types of carbon materials, namely activated carbon (AC), carbon nanotubes (CNT), exfoliated graphite nanoplatelets (xGnPs), and graphene, were dispersed in PCMs and impregnated into artificial lightweight aggregates via vacuum impregnation to create cement building materials. Various parameters including compressive strength, differential scanning calorimetry (DSC), hydration heat, thermal conductivity, and dynamic heat transfer were evaluated According to the results, the thermal conductivity of PCM was significantly improved by incorporating carbon materials, and the specimen with CNT showed a result of 0.8386 W/m∙K, which is about 20 % higher than that of the specimen without carbon materials. Although the compressive strength decreased with the addition of PCMs, it remained above 20 MPa, thereby ensuring structural integrity. In the dynamic heat transfer test, the carbon/PCM specimen maintained a higher temperature during heat dissipation. It showed a high peak temperature and a time delay of about 2.5 hours during free cooling. The results showed that integrating PCMs and carbon materials into cementitious building materials could effectively improve their thermal performance, potentially saving building energy.

Thermophysical properties and energy-saving efficiency of phase change microcapsule foamed cement composite insulation materials

The addition of phase change materials (PCMs) to building envelopes can improve building thermal stability and reduce energy consumption. In this study, phase change paraffin microcapsules are combined with foamed cement to create composite thermal insulation materials with varying mass ratios of microcapsules. A heat transfer characterization experimental platform was established to investigate the heat transfer laws. The incorporation of phase change microcapsules (MPCMs) into foamed cement resulted in a reduction in thermal conductivity. The thermal conductivity of the test blocks exhibited a linear relationship with the mass ratio of MPCMs, with an average thermal conductivity of 0.053 W/(m-K) observed for 20 % MPCMs. The impact of foamed cement containing MPCMs on building energy consumption was analyzed in five different climate zones in China using EnergyPlus. The results show that energy savings are more significant in cities with higher heating demand. In non-cold regions, energy savings are highest when the phase change temperature is close to the local annual average temperature. The optimal energy saving program is evaluated by energy consumption simulation. The results show that it achieves the highest energy savings in Harbin, which saves a total of 1074,007 kWh. Additionally, it has the highest energy saving rate in Beijing, with a rate of 14.66 %.

Thermal and mechanical performance assessment of composite (CPCM) for energy storage

Phase change materials (PCMs) face obstacles in being widely used due to issues with heat transfer and maintaining their shape. In this research, instead of using binders, the Hexadecane (H) is melted in such a way that the capillary forces of the molten wax allow it to be impregnated into the low-density polyethylene (P) molecules and bind it together as a composite. It was found that the hot melt extrusion (HME) combines the two materials at the micro-scale, forming a phase change composite (CPCM) with various geometries that possesses superior latent heat and shape stability during phase transition. The structure can incorporate a higher percentage of PCM (60 %) using this method, which also results in lower costs. According to the thermal analysis, (H60P40) provides great thermal stability and can store a lot of energy per unit of weight. It has a high capacity of storing latent heat at 129.56 J/g and can also prevent Hexadecane leakage. Based on the mechanical properties results, hexadecane acts like plasticizer thus the addition of PCM decreases Young's modulus, stress in break, and stress at yield. This trend is observed as the PCM content increases. The high values of elongation at break also indicates the strong plasticizing properties of PCM. Based on the obtained results, the CPCMs as a potential candidate for an application in buildings for thermal regulation, reducing energy consumption, and reducing indoor temperature swing.

Thermally Active Medium-Density Fiberboard (MDF) with the Addition of Phase Change Materials for Furniture and Interior Design.

No matter where we reside, the issue of greenhouse gas emissions impacts us all. Their influence has a disastrous effect on the earth's climate, producing global warming and many other irreversible environmental impacts, even though it is occasionally invisible to the independent eye. Phase change materials (PCMs) can store and release heat when it is abundant during the day (e.g., from solar radiation), for use at night, or on chilly days when buildings need to be heated. As a consequence, buildings use less energy to heat and cool, which lowers greenhouse gas emissions. Consequently, research on thermally active medium-density fiberboard (MDF) with PCMs is presented in this work. MDF is useful for interior design and furniture manufacturing. The boards were created using pine (Pinus sylvestris L.) and spruce (Picea abies L.) fibers, urea-formaldehyde resin, and PCM powder, with a phase transition temperature of 22 °C, a density of 785 kg m-3, a latent heat capacity of 160 kJ kg-1, a volumetric heat capacity of 126 MJ m-3, a specific heat capacity of 2.2 kJ kgK-1, a thermal conductivity of 0.18 W mK-1, and a maximum operating temperature of 200 °C. Before resination, the wood fibers were divided into two outer layers (16%) and an interior layer (68% by weight). Throughout the resination process, the PCM particles were solely integrated into the inner layer fibers. The mats were created by hand. A hydraulic press (AKE, Mariannelund, Sweden) was used to press the boards, and its operating parameters were 180 °C, 20 s/mm of nominal thickness, and 2.5 MPa for the maximum unit pressing pressure. Five variants of MDF with a PCM additive were developed: 0%, 5%, 10%, 30%, and 50%. According to the study, scores at the MOR, MOE, IB, and screw withdrawal resistance (SWR) tests decreased when PCM content was added, for example, MOE from 3176 to 1057 N mm-2, MOR from 41.2 to 11.5 N mm-2, and IB from 0.78 to 0.27 N mm-2. However, the results of the thickness swelling and water absorption tests indicate that the PCM particles do not exhibit a substantial capacity to absorb water, retaining the dimensional stability of the MDF boards. The thickness swelling positively decreased with the PCM content increase from 15.1 to 7.38% after 24 h of soaking. The panel's thermal characteristics improved with the increasing PCM concentration, according to the data. The density profiles of all the variations under consideration had a somewhat U-shaped appearance; however, the version with a 50% PCM content had a flatter form and no obvious layer compaction on the panel surface. Therefore, certain mechanical and physical characteristics of the manufactured panels can be enhanced by a well-chosen PCM addition.

Influence of microwave curing on the early performance of heat-stored LC3 composites

Limestone calcined clay cement (LC3), as a new green cementitious material, has a wide range of functional applications in cement-based composite materials. Heat-stored LC3 effectively achieve energy-saving and carbon reduction in buildings. However, the addition of phase change material (PCM) particles leads to a significant decrease in strength, which imposes higher requirements on early performance. To address this issue, this study adopts microwave curing technology to rapidly enhance the early performance of heat-stored LC3, with a specific focus on the influence of microwave curing on the early mechanical properties, hydration products, and microstructure of heat-stored LC3. The results showed that microwave curing at a power of 320 W for 5 min increased the 3-day compressive strength of heat-stored LC3 by 87.3 %, without adversely affecting the later-stage strength, thus compensating for the deficiency in early strength. Microstructure and pore structure analysis revealed that the enhancement of early strength by microwave curing was mainly attributed to the promotion of early hydration of clinker and the activation of pozzolanic reaction occurred calcined clay. The additional formation of C-(A)-S-H gel reduced the matrix porosity, improved overall integrity, and enhanced the microstructure. Additionally, the temperature regulation capability of heat-stored LC3 was verified, ensuring its auxiliary temperature regulation function while maintaining reliable mechanical properties and excellent early strength.

Post-processing of phase change material in a zero-change commercial silicon photonic process.

Integration of phase change material (PCM) with photonic integrated circuits can transform large-scale photonic systems by providing non-volatile control over phase and amplitude. The next generation of commercial silicon photonic processes can benefit from the addition of PCM to enable ultra-low power, highly reconfigurable, and compact photonic integrated circuits for large-scale applications. Despite all the advantages of PCM-based photonics, today's commercial foundries do not provide them in their silicon photonic processes yet. We demonstrate the first-ever electrically programmable PCM device that is monolithically post-processed in a commercial foundry silicon photonics process using a few fabrication steps and coarse-resolution photolithography. These devices achieved 1.4 dB/μm of amplitude switching contrast using a thin layer of 12.5 nm GeSbTe in this work. We have also characterized the reconfiguration speed as well as repeatability of these devices over 20,000 switching cycles. Our solution enables non-volatile photonic VLSI systems that can be fabricated at low cost and high reliability in a commercial foundry process, paving the way for the development of non-volatile programmable photonic integrated circuits for a variety of emerging applications.

Study on phase change materials integration in concrete: Form-stable PCM and direct addition

As the economy continues to develop, building energy consumption rises, necessitating sustainable solutions. Concrete, a pivotal building material, assumes a vital role in this context. To address the challenge of escalating energy consumption and environmental impact, this study studied the integration of phase change materials (PCMs) into concrete by two methods. Recycled aggregates serve as form-stable mediums for PCM absorption, while direct addition methods incorporate 7.5 % and 15 % free liquid PCM by volume of river sand. Six concrete mixtures underwent comprehensive evaluation encompassing workability, density, water absorption by immersion, compressive strength, flexural strength, chloride ion penetration, freeze-thaw cycling tests, and carbonation. The results reveal a decrease in concrete density and mechanical properties with increasing PCM content. Nevertheless, notable enhancements in chloride ion penetration resistance, reaching up to 18.5 % with free PCM incorporation, and zero carbonation depth were observed. These results underscore the potential of PCM-concrete composites in harmonizing energy efficiency and structural integrity, offering a sustainable alternative to fossil fuel-based air conditioning systems and with great potential from the point of view of the durability of the structures.

CEMENT COMPOSITES WITH THE ADDITION OF PHASE-CHANGE MATERIALS AS INNOVATIVE CONSTRUCTION MATERIALS FOR MAINTAINING A PLEASANT LIVING ENVIRONMENT

The aim of this work was to investigate the possibility of the addition of phase-change material (PCM) to mortar mixtures and its effect on the material’s mechanical and thermal properties. This work included the preparation of mortar mixtures with two different water-to-cement (w/c) ratios as well as various PCM volume-fraction additions. The main objectives were to determine the effect of the w/c ratio as well as the PCM addition on the mechanical properties of the mortars after (3, 7, and 28) d of curing. Additionally, we examined the microstructure of the prepared mortar composites and evaluated their thermal behaviour. Microstructural analysis revealed the uniform distribution of PCM microcapsules throughout the mortar matrix, which contributes to the efficient storage and release of thermal energy. Thermal properties were analysed by repeated heating and cooling cycles of the mortar composites. The repeatability of the cyclic testing results showed a reversible melting and solidification phase change of the PCM and indicated the potential use of such composites as an energy-efficient building material. The study highlighted the potential incorporation of the PCM into mortar mixtures to improve their thermal properties while maintaining the mechanical integrity. The research findings provide valuable insight into the development of sustainable building materials with greater energy efficiency and structural reliability.

Thermal management techniques for enhancing hydrogen adsorption and desorption in metal hydride reactors: a short recent review

This manuscript presents a short recent review of various techniques used for thermal management enhancement in metal hydride reactors, emphasizing their effect on hydrogen adsorption and desorption. Mainly, the article highlights 4 techniques: The incorporation of various fin types, the integration of heat exchangers within the metal hydride reactor, the addition of heat transfer enhancing material into the MH bed, and the addition of phase change material (PCM). The analysis presented provides brief insightful information about the state of Metal hydride reactors now, laying the groundwork for future studies and advancements in this area.

Study on the Interaction of Polymeric Chemical Additives with Phase Change Materials in Air Lime Renders.

The interaction of microencapsulated phase change materials (PCMs) with polymeric chemical additives in an air lime binding matrix was studied. These polymer-based additives included an adhesion booster (derived from starch) and a superplasticizer (polycarboxylate ether). Two different PCMs with melting points of 18 °C and 24 °C were assayed. The microcapsules were composed of melamine, with paraffin-based PCM cores. Measurements of zeta potential, particle size distribution, adsorption isotherms, and viscosity analyses were performed to comprehend the behavior of the polymer-based additives within the air lime matrix and their compatibility with PCMs. Zeta potential experiments pointed to the absence of a strong interaction between the lime particles and the microcapsules of PCMs. At the alkaline pH of the lime mortar, the negative charge resulting from the deprotonation of the melamine shell of the microcapsules was shielded by cations, yielding high positive zeta potential values and stable dispersions of lime with PCMs. The polycarboxylate ether demonstrated the ability to counteract the increase in mixing water demand caused by the PCM addition in the lime matrix. The dispersing action of the superplasticizer on the lime particles was seen to exert a collateral dispersion of the PCMs. Conversely, despite the positive values of zeta potential, the addition of the starch-based additive resulted in the formation of large PCM-lime clumps. Air lime renders incorporating 5, 10, and 20% PCMs by weight with various dosages of these chemical additives were experimented with until the optimal formulation for the specific application of the mortars as renderings was achieved. This fine-tuned formulation effectively tackled issues commonly associated with the addition of PCMs to mortars, such as poor adhesion, crack formation, and reduced fluidity.

Possibility of Using a Geopolymer Containing Phase Change Materials as a Sprayed Insulating Coating - Preliminary Results

Geopolymers have been known for decades and classified as inorganic polymers, characterized by high resistance to high temperatures. They can be successfully used for the thermal insulation of buildings, especially in the foamed form. The addition of phase change materials (PCMs) in such materials may also increase the heat capacity of the materials, therefore, using them for building cladding can increase the thermal comfort of the building and prevent it from overheating. This study tests the addition of PCMs to geopolymers by spraying and presents the results. Additionally, the study includes preliminary experience concerning the technology of applying these materials, along with selected test results that assess the properties of the produced coatings. The results indicate that the addition of PCMs in the amount of 15% can increase the heat capacity of geopolymer materials by about 150-180%, and the foamed geopolymer coatings produced have a thermal conductivity in the range of 0.07-0.09 W/mK.

Faz Değişim Malzemesi Olarak Parafinin Bir Batarya Termal Yönetim Sisteminin Soğutma Performansı Üzerindeki Etkisinin Deneysel Olarak İncelenmesi

Internal combustion engines (ICEs) are largely dependent on fossil fuels, and both the risk of depletion of fossil fuels and the harmful exhaust emissions emitted by ICEs have led researchers to become interested in electric vehicles (EVs). As the EV industry develops day by day, battery thermal management systems (BTMS) have become indispensable in solving the high-temperature problem of batteries, which are the most important component of EVs. The cost and reliability of electric vehicles are affected by parameters such as the life cycle, capacity, charging time, durability, and warranty cost of the battery pack used. The heat produced in the battery pack is removed by gas or liquid cooling in active cooling, and by phase change materials (PCM) in passive cooling. The high energy storage density of PCMs and the fact that there is no need for fan or pump power in cooling using PCMs are some of the reasons why PCMs are preferred for BTMSs. In this study, a battery pack consisting of 18 lithium-ion batteries, 6 in series and 3 in parallel, was first charged and discharged without any cooling system and then with the addition of PCM at a current strength of 1C, and the effect of the BTMS was examined. It has been observed that the BTMS has a positive effect of approximately 8% for charging experiments and 23% for discharge experiments in terms of the maximum temperature value in the battery pack.

Layer combination design and effect evaluation of phase change cooling asphalt pavement

Asphalt mixture is a temperature sensitive material. With the change of external environment temperature, asphalt pavement is prone to temperature-related diseases. Adding phase change material (PCM) to asphalt pavement to adjust pavement temperature is one of the effective methods at present. At present, there are many types of research on PCMs, but the research on PCMs added to the pavement structure is very scarce. In this paper, through the temperature test of rutting plate specimens with different layer combinations, the cooling effect of pavement structure combinations with PCMs added to different layers (upper layer, middle layer, and bottom layer) in pavement structure under different illumination times are discussed. Through the self-designed environmental simulation box, the real-time monitoring of the temperature of different layers in the pavement structure is realized. The cooling effect between different layers in different phase change pavement structure combinations is analyzed, and compared with each layer of ordinary pavement structure, and the best addition method is obtained for phase change materials, which provides a certain reference for the construction and specific application of PCM asphalt pavement, and made important contributions to the development of asphalt cooling pavement. The results show that the PCM can effectively reduce the temperature of each layer of the pavement structure. Under different illumination durations, the cooling effect of the samples with PCM in the upper layer was the worst. The samples with phase change material in the middle layer had the best cooling effect in the upper and middle layers of the pavement. The addition of phase change material to both the upper and middle layers had the most obvious cooling effect on the lower layer of the pavement. Therefore, combined with the comprehensive consideration of economy and cooling effect, the comprehensive cooling effect of adding PCMs to the middle surface layer is the best. It is recommended to add phase change materials to the middle surface layer during asphalt cooling pavement construction.

PCM microcapsules applicable foam to improve the properties of thermal insulation and energy storage for cement-based material

In the field of material science, foaming agents common are commonly used for enhancing the thermal insulation and phase change materials (PCM) for heat storage. However, PCM tends to agglomerate in the cement slurry with the directly addition, presenting an obstacle to effective dispersion. Moreover, the addition of PCM leads to rapid defoaming. To overcome this issue, a novel nanoparticle-stabilized foam was designed in this study to create a three-component system that enhances the interaction of viscosity modifiers, surfactants, and foam stabilizers. The effect of cement density on thermal insulation was evaluated by analyzing thermal conductivity and heat transfer performance tests, as well as exploring the mechanical properties of the cement-based materials. Scanning electron microscope (SEM) images show that the foam designed in this study remarkably promotes the dispersion of PCM microcapsules, indicating the bridging interactions of foam in the cement paste. The result shows that the thermal conductivity of foam cement with 15 vol% PCM microcapsules drops from 0.11 W/m·k to 0.07 W/m·k compared to that without PCM addition, with a dry density around 600kg/m3. Furthermore, the specimens with the addition of PCM achieve the endothermic and exothermic peaks under experimental images. This discovery is of great significance to heat absorption ability of low-density concrete, where the addition of PCM leads to a slower foam bursting under the nanoparticle-reinforced foam system. The dispersion and connectivity of foams, as well as the physical characteristics of PCM, provide new perspectives for coexistence in a relatively stable system in this way.

Incorporating phase change materials in geothermal energy piles for thermal energy storage

Introduction
 Geothermal energy piles (GEPs) are foundation elements that are installed in the ground to support the weight of the building to a competent strata. Energy loops are installed into the piles to allow heat rejection or extraction via the circulation of fluid through the loops. In winter, low-grade heat is extracted from the ground (source) and transferred to the building (sink) to achieve space heating. Conversely, in summer, heat is removed from the building and rejected into the ground to achieve space cooling. The system relies on the temperature gradient between the ground and the ambient air temperature; where in winter, the ground temperature is higher than the air temperature, while in summer, the opposite is true. Thus, the system can sustainably and continuously supply the heating and/or cooling demand of a building once the temperature gradient between the ambient air and the ground is maintained. To improve the sustainability and performance of the system, the heat energy rejected into the ground can be stored and used at a later time when space heating is required [1]. Energy storage substances such as phase change materials (PCMs) can be incorporated into energy piles to store the heat that is rejected into the ground to improve the performance of the GEP system [2]. PCMs are materials that stores or releases heat energy during phase transition. Many researchers including [3,4] have reported using PCMs in buildings to improve thermal comfort and minimise the energy demand during heating and cooling periods, however, not much work has been done with regard to incorporating them into pile foundations to improve the performance of GEP systems.
 Thus, this study carried out a laboratory experiment to investigate the effect of the addition salt hydrate PCM on the energy performance of geothermal energy piles.
 Laboratory test and procedure
 In this study, lab-scaled models of energy piles were constructed, with and without PCM. The piles are characterised by a length and a diameter of 300 mm and 100 mm, respectively. In order to add PCM into the piles, the PCM was encased and sealed in a PVC tube with an inner and an outer diameter of 6mm and 8mm, respectively. The same size of PVC tube was used for the energy loops. The energy loop (U-shape), and the encased PCM incorporated tubes are attached together and placed in the mould prior to concreting, for the pile model with PCM (see Figure 1a). Whereas only the energy loop was installed in the control sample.
 In the test setup, a layer of sand (220mm thick) was placed and compacted in an insulated wooden box (520mm × 520mm × 520mm). Afterwards, the pile was then installed at the center of the box and then filled with sand, in layers and compacted. An insulation sheet was used to cover the top of the box to prevent heat loss and the ambient air temperature influencing the tests’ results. Water at a temperature of 32°C, was circulated through the pile continuously for a duration of 4 days (96 hours). Instrumentations were installed in the pile and soil to monitor and record the changes in temperature during the tests (see Figure 1b).
 Results and discussion
 Figure 1c shows the results comparing the average energy rejected, and stored, in the ground for the piles with and without PCM. The maximum heat energy stored at the beginning of the test was found to be about 460W and 360W for the control and PCM piles. However, at the end of the tests, the energy stored was 230W and 430W for the control and PCM pile, with an average energy stored as shown in Table 1. The addition of salt hydrate PCM absorbs the heat rejected into the pile, consequently improving its thermal performance by about 22% in comparison to the control pile. Similarly, the magnitude of temperature developed in the pile and surrounding soil were observed to be lower in the pile with PCM. This can ultimately reduce the induced stresses and strains induced in a pile due to heat energy extraction or rejection.
 
 Conclusion
 This paper investigated the feasibility of using salt hydrate PCM in energy piles for heat storage. It was found that the energy rejected in a pile with PCM increases by up to 22% compared to a non-PCM pile.

Effect on the Thermal Properties of Building Mortars with Microencapsulated Phase Change Materials for Radiant Floors

The use of slag silicate cement mortar as a thermal mass layer for radiant floor heating systems holds significant potential for active thermal energy storage systems in buildings. The main objective of this article is to experimentally test the thermal performance of slag silicate cement mortar thermal storage blocks after the addition of phase change materials. The present study focuses on investigating the thermal performance of thermal storage blocks made of slag silicate cement mortar that incorporates a microencapsulated phase change material (mPCM). The mPCM consists of particles of paraffin-coated resin, which are uniformly distributed in the mortar. The analysis revealed that the introduction of mPCM particles into the mortar decreases the bulk density by approximately 9.4% for every 5% increase in mPCM particles ranging from 0% to 20%. The results obtained utilizing the Hot Disk characterization method demonstrate that the mPCM particles significantly affect the thermal properties of the mortar. Particularly, the thermal conductivity and thermal diffusion coefficient of the SSC30 mortar with a 17.31 wt.% mass of mPCM particles decreased by 59% and 69%, respectively. The results of this study provide a basis for the application of RFHS end-use thermal storage layers.

Performance assessment of capric acid-ethyl alcohol/expanded vermiculite phase change material incorporated cement mortar for thermal insulation in buildings

Due to global warming, the construction sector is looking for newer materials that can be incorporated into buildings to improve occupant thermal comfort while reducing energy consumption. The ability of construction materials to store thermal energy can be enhanced by incorporating phase change materials (PCM). A PCM is a substance that releases and absorbs energy at phase transition temperatures to offer useful heating or cooling. The addition of PCM in construction materials for thermal insulation has been proven beneficial by many researchers. The current study explores the feasibility of the incorporation of an organic PCM composite, which is developed by impregnating expanded vermiculite (EV) with capric acid (CA) using ethyl alcohol (EA) under vacuum conditions in cement mortar. Cement mortar mixes with EV, CA-EA/EV based PCMs, and PCMs with partially added nano silica and coir fiber combinations (PSC) were prepared by replacing fine aggregate in varied weights. Initially, the study on the primary characteristics of the developed PCM was introduced based on mechanical behavior, microstructure observations, and thermal effects. To estimate the field exposure capacity, PCM composite mortar boards were developed and tested for their physical and mechanical characteristics. Based on the findings of these tests, it was concluded that the presence of PCM improves the thermal characteristics of the mortar boards and the addition of nano silica and coir fiber enhances the physical and mechanical strength of the mortar boards. With regard to the characterization of the mortar, there was an increase in flexural strength by 8.06 % and a decrease in chloride diffusivity by 10.24 %, in water absorption by 17 %, the capillary water absorption coefficient by 8.56 % and the ultrasonic pulse velocity by 18.48 % relative to the control sample after addition of PSC into the mortar. Apart from the strength and durability studies, differential scanning calorimetry (DSC), energy-dispersive X-ray spectroscopy (EDS), thermogravimetry analysis (TGA) and scanning electron microscopy (SEM) tests were also carried out to characterize the thermal, chemical and morphological effects of the developed cementitious composite boards. As per the SEM and EDS test results, the fine aggregate replaced with 5 % of PCM in addition to nano silica and coir fiber (PSC-5 %) possesses better compatibility with the mortar by effectively penetrating through the pores. The DSC test results showed the melting and freezing point of PSC-5 % integrated mortar as 32.47 °C and 20.91 °C, respectively. A thermal conductivity value of 0.129 W/m·K also demonstrated the efficiency of PSC-5 % mortar board for maintaining better thermal comfort in buildings. The TGA assessment reported that the proposed PCM composite cement mortar board has excellent thermal durability.

Experimental and numerical investigation of the thermal inertia of sugar-beet-pulp/starch based bricks enhanced with phase change materials

Due to environmental concerns, bio-based materials are being increasingly investigated and used in buildings. In general, the density of these materials, and thus their thermal inertia, is low. Thermal inertia can be beneficial for reducing the energy use of buildings by damping indoor temperature fluctuations or by reducing and delaying incoming (solar) heat through the façade.This study explores the thermal inertia of regular-sized bricks made of a sugar-beet-pulp/starch mixture (BP/S), and with 17 circular holes inside. The holes were filled either with the BP/S mixture, with air, with a stabilised phase change material (PCM) gel or with a salt-hydrate based PCM. The brick was insulated on all sides but one. Two series of experimental measurements were performed: 1.) a heating film placed at the back (insulated) side of the brick heated the brick until steady-state conditions were reached; 2.) the heated brick was then passively cooled down to ambient temperature by cutting the power to the heating film. Numerical simulations of these experimental measurements were also modelled using the COMSOL Multiphysics® software. In addition, simulations were run to study the thermal inertia of a full brick wall made out of 1 layer and of 4 layers of the BP/S brick with and without PCM, exposed to a combination of a sinusoidal outdoor air temperature fluctuation with an imposed radiation flux on the outdoor surface, representing summer conditions.The results show that the brick in which the holes were filled with phase change material had a slower temperature response and thus higher thermal inertia than the bricks in which the holes were filled with BP/S or with air. The salt-hydrate based PCM with the higher latent heat of fusion led to the slowest temperature response and highest thermal inertia. Furthermore, the calculated simulations could accurately reproduce the experimental measurements. Applying PCM in thick walls (40 cm) made of BP/S bricks however hardly affects the temperature amplitude damping and time delay of the complete wall. The addition of PCM therefore is only effective for thinner walls (10 cm).

Addition of granular phase change materials (PCMs) and graphene to a cement-based mortar to improve its thermal performances

The addition of phase change materials (PCMs) into building materials represents a valid strategy towards the improvement of their thermal performance and therefore of the indoor comfort. However, when paraffin PCMs are used, the thermal conductivity of the mixture inevitably decreases due to the PCM low thermal conductivity. The research here presented focused on the addition of granular paraffin PCM into a cement-based mortar to improve its thermal storage capacity, and of hydrophobic graphene to counterbalance the reduction in thermal conductivity. Experimental tests at laboratory scale and numerical simulations were carried out to compare the behavior of two equivalent radiant floor samples in terms of temperatures and heat fluxes. Lower temperature fluctuations and delayed minimum temperatures were observed in the mortar with PCM and graphene, if compared to the Reference one. Eventually, in order to investigate the possibility of using the new mortar in case of building refurbishment, a floor with the enhanced mortar lowered 1 cm was simulated and then compared to the reference one. Results showed that the surface of the lowered floor reached the same maximum temperature with the system on and up to 3 K higher with the system off.