Phase Change Materials Content Research Articles

Performance evaluation and optimization of compact tube-fin latent heat storage system in phase change nanoemulsion discharge mode

The low thermal conductivity of phase change materials (PCMs) and the reduced heat transfer temperature difference along a tube both limit the thermal performance of latent heat thermal energy storage (LHTES). Herein, a compact tube-fin LHTES system based on phase change nanoemulsions was developed and the heat transfer process of nanoemulsion and PCM was numerically investigated. The effects of the heat transfer structure of the heat exchanger and the thermophysical parameters of the heat transfer fluid (HTF) on the cold energy discharge performance of the system were quantified. The optimized model reduced the discharge time by 24.4 % in nanoemulsion mode relative to water. Heat transfer improvement on the PCM side could be achieved by decreasing the fin spacing and tube spacing and by increasing the fin thickness. Such improvement reinforced the heat transfer enhancement of the nanoemulsion. The heat transfer mechanism was explained by the temperature distributions of the HTF and PCM along the tube. The phase-change thermostatic properties of the nanoemulsion and PCM contributed to the formation of dual-phase-change coupled heat transfer (i.e., the heat transfer process when the fluid inside the tube and the PCM filled outside the tube undergo a simultaneous phase change) within the LHTES, increasing the heat transfer temperature difference and the magnitude of the driving force. Increasing the phase change temperature difference accelerated the onset of dual-phase-change heat transfer, while increasing the PCM content prolonged the process. Briefly, this study provided operational and design assistance for LHTES systems in nanoemulsion mode with the intention to accelerate heat transfer rates.

A comprehensive experimental characterization of cement mortar containing sodium sulfate dehydrate/calcium chloride hexahydrate/graphite shape-stable PCM for enhanced thermal regulation in buildings

The current research on integrating phase change materials (PCMs) into building envelopes is driven by the need to optimize thermal performance while preserving material properties. Integrating PCM into cement mortar faces challenges in balancing heat storage capacity and material strength. Using higher PCM content may compromise strength, but smaller content may limit heat storage capacity. To overcome these hurdles, integrating high-conductive SSPCM at lower percentages can enhance thermal performance without compromising material integrity. Yet, research in this domain is lacking. This study investigates integrating a shape-stable PCM into plaster to ascertain the ideal PCM content while maintaining vital characteristics. Experimental analysis of five composites, with PCM percentages ranging from 3% to 10%, showed that all met physical property criteria except the 10% PCM composite. Despite a slight decrease in mechanical strength, it remained within acceptable standards for mortar materials. The composites exhibited improved thermal conductivity, specific heat capacity, thermal diffusivity, and heat storage capacity significantly with increasing PCM content. This study convincingly demonstrates the feasibility of maintaining thermal effectiveness even with low PCM content, offering crucial insights for developing energy-efficient building designs and promoting sustainable practices in the construction industry.

Re-Designing Cellulosic Core-Shell Composite Fibers for Advanced Photothermal and Thermal-Regulating Performance.

Flexible fibers and textiles featuring photothermal conversion and storage capacities are ideal platforms for solar-energy utilization and wearable thermal management. Other than using fossil-fuel-based synthetic fibers, re-designing natural fibers with nanotechnology is a sustainable but challenging option. Herein, advanced core-shell structure fibers based on plant-based nanocelluloses are obtained using a facile co-axial wet-spinning process, which has superior photothermal and thermal-regulating performances. Besides serving as the continuous matrix, nanocelluloses also have two other important roles: dispersing agent when exfoliating molybdenum disulfide (MoS2), and stabilizer for phase change materials (PCM) in the form of Pickering emulsion. Consequently, the shell layer contains well-oriented nanocelluloses and MoS2, and the core layer contains a high content of PCM in a leak-proof encapsulated manner. Such a hierarchical cellulosic supportive structure leads to high mechanical strength (139MPa), favorable flexibility, and large latent heat (92.0Jg-1), surpassing most previous studies. Furthermore, the corresponding woven cloth demonstrates satisfactory thermal-regulating performance, high solar-thermal conversion and storage efficiency (78.4-84.3%), and excellent long-term performance. In all, this work paves a new way to build advanced structures by assembling nanoparticles and polymers for functional composite fibers in advanced solar-energy-related applications.

Effect of blending of medium-temperature phase change material on the bitumen storage heat

This study aims to investigate the feasibility of using D-Mannitol as a phase-change material (PCM) to increase the energy storage capacity and improve the thermomechanical characteristics of the modified bitumen. D-mannitol (Dm) was incorporated into Bitumen (Bm) using a high-speed shearing method. The results showed that the integration of PCM enhanced the physical characteristics of the basic bitumen, with the modified bitumen having a melting point close to that of D-mannitol (Tm = 164 °C). The D-mannitol was found to crystallize during cooling, indicating that it can store or release heat in the latent form. The specific heat capacity of the modified bitumen was proven to increase gradually as the PCM content (2, 4, and 8 wt%) increased. The maximum temperature regulation effect of the modified bitumen was observed when the PCM content reached 8 wt%, resulting in a temperature reduction of up to 9 °C. This study provides a basis for the utilization of D-Mannitol as a form of energy storage in bitumen-based pavement applications.

Study on the Performance of Phase-Change Self-Regulating Permeable Asphalt Pavement

Under low-temperature conditions in winter, asphalt pavement is prone to cracking, icing and other distresses, which affect its safety and comfort. Therefore, by incorporating phase-change materials into asphalt and conducting relevant performance studies, the aim is to alleviate low-temperature distress and regulate road surface temperature and expand the application of phase-change materials in asphalt pavement. We mixed the selected phase-change materials with different dosages into the matrix asphalt to prepare phase-change temperature-regulating asphalt and tested the four basic indicators: road performance, latent heat characteristics, temperature-regulating performance, and rheological properties of phase-change asphalt and its mixture. The research results indicate that with the increase in phase-change material content, the penetration, softening point, ductility, and dynamic viscosity of phase-change high-viscosity asphalt gradually increase. Under the constant temperature test conditions of −2.5 °C and −5 °C, the surface icing speed of asphalt binder specimens mixed with phase-change materials is slower than that of specimens without phase-change materials. Adding phase-change materials can improve the high-temperature and low-temperature PG grading of high-viscosity asphalt, effectively improving its high-temperature rutting resistance and low-temperature cracking performance. According to the temperature regulation test results, phase-change temperature-regulating asphalt has a certain regulating effect on temperature under low-temperature conditions, which can slow down the cooling rate of asphalt, reduce the thermal conductivity of permeable asphalt mixture by more than 50%, increase the temperature regulation rate by more than 30%, and improve the ice-melting and snow-melting ability by more than 20%. Phase-change materials have almost no effect on the porosity of permeable asphalt mixtures and can effectively improve the water stability, low-temperature crack resistance, and antiflying performance of permeable asphalt mixtures. Their Marshall stability and rutting stability decrease, but still meet the requirements of the specifications. Applying phase-change materials to permeable asphalt pavement can automatically adjust the temperature of the pavement, reduce the cooling rate of the asphalt pavement during cooling, alleviate the problem of snow and ice accumulation on the asphalt pavement in winter, and thereby improve the performance of permeable asphalt pavement against freeze–thaw cycles.

The impact of different fin configurations and design parameters on the performance of a finned PCM heat sink

This work builds on our recent research on finned phase change material (PCM) heat sinks, where we proposed a novel Gallium based PCM heat sink concept that counter-intuitively incorporated fins detached from the hot sink base instead of being fully attached to it. The detached and fully attached fin configurations studied utilized the same overall fin size and material resources. The attached fin approach offered less outer fin surface area exposed to the ambient surroundings and less PCM capacity compared with the detached fin approach. However, the attached fin approach facilitated a more direct path for the heat dissipation into the ambient surroundings via the fin body. As an extension of the previous work, the present work explores finned heat sinks that combine the advantages of the above two approaches. First, we present results for two limiting baseline cases of the two finning categories: attached fins with lower outer fin surface area and less PCM and detached fins with a larger exposed fin area and more PCM. Next, we study a heat sink case with attached fins tall enough to have a total outer fin surface area equivalent to the outer surface area of the detached fins case but with less PCM content. Subsequently, we consider cases of fully attached fins with the same total outer fin area and the same total PCM capacity as the detached fins baseline case. Here, we achieve the same PCM content in the sink while still having fully attached fins simply by increasing the overall heat sink size to accommodate additional PCM. This is done in two ways: (1) by expanding the heat sink size in the horizontal direction (i.e., increasing the heat sink width) at constant heat sink height, and (2) by expanding the heat sink height at constant heat sink width. In this work, we propose the best way to utilize the resources in terms of used PCM and used fin content in the heat sink space to achieve the ultimate goal of attaining lowest peak temperatures.

Improving thermal storage of energy screw pile groups with phase change materials

To achieve affordable housing in a carbon-neutral society, new buildings require a dual-purpose approach that comprises efficient construction and a green energy supply. Energy screw piles [1, 7] meet this demand as they combine the agility of screw pile drilling with the capability of extracting clean shallow geothermal energy. Moreover, the screw piles can be filled with phase change materials (PCM) to provide latent thermal storage. Studies regarding the use of PCMs as borehole backfill in a ground source heat pump system (GSHP) conclude that PCM implementation can improve GSHP performance. However, most commercially available PCMs have low thermal conductivities (λ) which undermine heat exchange rates [5, 10]. Besides, using PCMs as a composition of a concrete energy pile can reduce the pile structural performance since PCMs usually have a low mechanical capacity [2, 8]. The authors recently introduced PCM-sand mixtures as a core in the central hollow part of an energy screw pile, which does not impact the pile structural capacity [6]. The mixtures with a higher PCM content benefit the pile heat exchange through its latent heat, but only when the PCM does not reduce the mixture’s λ. To overcome this problem, this work tests a new underground heat exchange system where instead of mixing the PCM in the energy screw pile filling material, regular screw piles (i.e., without the heat exchange tubes) are filled with pure PCM, acting as thermal storage piles. A numerical model built via COMSOL [4] is used to evaluate how this combination of screw piles performs thermally when supplying/rejecting heat for a GSHP system operating for a whole year.
 This work uses a validated numerical model [3, 9] to simulate a grid of evenly distributed screw piles, where Energy Piles (EP) and Thermal Storage Piles (TSP) are positioned interspersed, evenly spaced 0.7 m apart. Inside the EPs, an U-loop pipe is inserted in the pile steel case and the remaining is filled with grout. In contrast, the steel case of the TSPs is filled with only PCM [11]. All other material properties and the screw pile geometry are based on [1]. The thermal load is based on the design of a building located in Melbourne, Australia (Figure 1(a)). The model considers the hourly operation of a GSHP for one year, calculating the GSHP Coefficient of performance (COP) at every time step and adjusting the ground thermal load. For comparison, two simulations (one where the TSPs are filled with PCM and a reference where they are filled with only air) are undertaken. Besides the energy stored, the COPs of both cases are compared as a relative increase/decrease percentage (COPchange = (COPPCM / COPReference) – 1).
 Figure 1(b) presents the energy stored by the PCM and its corresponding percentage in a solid state over the simulation. As the EPs reject heat underground due to GSHP summer operation for cooling, the TSPs temperature rise and store sensible heat, until they reach their phase change temperature (Tpc), when the PCM melts to store significantly more heat energy in a shorter time window due to latent heat. Conversely, the PCM solidifies when EPs extract more heat than reject due to GSHP winter operation (heating) for a certain period. The PCM melts again on the following summer, restarting the whole process. The peak energy stored in the TSPs is 190.3 MJ/m3. Even though the thermal load varies hourly, the PCM phase change process happens without immediate responses to the load variation. Figure 1(c) presents the resulting change in the hourly COP considering cooling (CCOP) and heating (HCOP) from implementing PCM in the TSPs, compared to the reference scenario (empty TSPs). The extra heat stored by the PCM lowers the circulating fluid temperature while the latent heat is engaged (months 2 to 7 and 12), which results in a higher CCOP and a lower HCOP. By plotting a monthly average of the COPchange (grey markers), it is clear that the impact of the PCM on the COP is positive when cooling is dominant and slightly negative when heating becomes dominant while the latent heat is engaged. When the PCM is implemented in the EP [6, 10], the heat exchanged by the EP drops once the phase change process is over due to the low λ of the PCM, but by positioning it outside the EP the higher CCOP is sustained even after the phase change ends. However, lowering the fluid temperature increases CCOP while lowering HCOP at the same time, which can harm thermal performance if not designed properly. The results underlie the thermal storage potential available not only in screw piles, but also in any hollow pile foundation, by simply implementing PCM in the hollow case.

Biomass-Based Shape-Stabilized Composite Phase-Change Materials with High Solar-Thermal Conversion Efficiency for Thermal Energy Storage.

To alleviate the increasing energy crisis and achieve energy saving and consumption reduction in building materials, preparing shape-stabilized phase-change materials using bio-porous carbon materials from renewable organic waste to building envelope materials is an effective strategy. In this work, pine cone porous biomass carbon (PCC) was prepared via a chemical activation method using renewable biomaterial pine cone as a precursor and potassium hydroxide (KOH) as an activator. Polyethylene glycol (PEG) and octadecane (OD) were loaded into PCC using the vacuum impregnation method to prepare polyethylene glycol/pine cone porous biomass carbon (PEG/PCC) and octadecane/pine cone porous biomass carbon (OD/PCC) shape-stabilized phase-change materials. PCCs with a high specific surface area and pore volume were obtained by adjusting the calcination temperature and amount of KOH, which was shown as a caterpillar-like and block morphology. The shape-stabilized PEG/PCC and OD/PCC composites showed high phase-change enthalpies of 144.3 J/g and 162.3 J/g, and the solar-thermal energy conversion efficiencies of the PEG/PCC and OD/PCC reached 79.9% and 84.8%, respectively. The effects of the contents of PEG/PCC and OD/PCC on the temperature-controlling capability of rigid polyurethane foam composites were further investigated. The results showed that the temperature-regulating and temperature-controlling capabilities of the energy-storing rigid polyurethane foam composites were gradually enhanced with an increase in the phase-change material content, and there was a significant thermostatic plateau in energy absorption at 25 °C and energy release at 10 °C, which decreased the energy consumption.

Impact of gypsum mortars functionalized with phase change materials in buildings

The construction industry needs to adopt raw materials with less environmental impact and functional raw materials. The utilization of phase change materials (PCM) in interior mortars allows the energy efficiency of buildings improvement, based on solar energy, a renewable and clean energy source. On the other hand, the selection of mortars based in binders whose production emits lower carbon dioxide emissions than cement, like gypsum, can be a promising solution in help to minimize carbon dioxide (CO2) emissions and the energy consumption for raw materials production. The main objective of this work was the development and characterization of gypsum-based mortars functionalized with PCM. Four distinct mortars were developed with different contents of pure and non-encapsulated PCM (0 %, 5 %, 10 % and 20 %). The different mortars were tested from a physical and mechanical point of view. The thermal performance of the mortars according to the summer and spring seasons of the north part of Portugal and an economic analysis of the application of these mortars in a typical Portuguese building were also carried out.The results obtained allow to observe that the incorporation of 20 % PCM leads to a decrease in the water absorption by capillarity, water absorption by immersion, flexural and compressive strengths of about 65 %, 30 %, 47 % and 59 %, respectively. However, its applicability has not been compromised. The thermal performance of the PCM mortars was improved, based in the temperature range and heating and cooling needs decrease. Regarding to the summer season it was observed a maximum temperature decrease of 2.3 °C, a minimum temperature increase of 2.6 °C and a decrease of cooling and heating needs of 13 % and 21 %, respectively. Concerning to the spring season it was verified a maximum temperature decrease of 2.7 °C, a minimum temperature increase of 1.9 °C and a decrease of cooling and heating needs of 100 % and 16 %, respectively. The cost analysis revealed savings in electricity costs for buildings climatization of around 17 % during the summer season and around 59 % during the spring season.

Effects of Phase Change Materials on the Freeze–Thaw Performance of Expansive Soil

Freeze–thaw cycles can deteriorate the expansive soil performance. Phase change materials (PCMs) absorb and store heavy latent heat from the environment, which can be utilized to mitigate freeze–thaw deteriorations in expansive soil. In this study, an environmentally friendly paraffin-based PCM was selected, which included two different forms: liquid (pPCM) and microcapsules (mPCM). The volume change, mechanical properties, thermal properties, and microstructure of the improved soil were studied. These results showed that PCMs can release considerable thermal energy during phase transitions, which improves the thermal stability of the soil. The pPCM enhanced the plasticity of soil and prevented brittle failure; mPCM reduced the damage to the soil microstructure caused by freeze–thaw cycles. Macroscopically, it weakened the swell–shrink behavior and limited the degradation of the resilient modulus, unconfined compressive strength, and failure strain of expansive soil. The optimal PCM content was determined based on the mechanical and thermal properties of the improved soil. This study provides a new idea for the engineering treatment of expansive soil in cold regions.

Numerical simulation of the anti-freezing performance of a phase change clay core-wall with loose covering

Clay core-wall of rockfill dam may endure short-term freezing or freeze–thaw cycles owing to negative temperature conditions during winter construction in cold regions, resulting in the degradation of the clay compaction, frost swelling, and cracking performance. The most commonly used insulation cover measures interfere with the continuous construction of clay core-walls, which may shorten the effective time available for construction and delay the dam construction progress. To address this problem, we proposed using the upper layer of the loose-covering clay and the latent heat of phase change materials (PCMs) to control the core-wall temperature. We implemented a numerical model for simulating the anti-freezing performance of the PCM mixed clay (PCM-clay) with loose covering. First, a heat transfer model was established using the finite element software COMSOL, and the effectiveness of the model was verified by comparing it with indoor temperature control test results. Subsequently, numerical models including different construction conditions were established, and the temperature control effect was analyzed under different loose-covering thicknesses, initial soil temperatures, and PCM contents. The results showed that at the design ambient temperature and a 2% PCM content, an effective construction time availability of two consecutive days was maintained under a 20-cm-thick loose covering. In contrast, under the same temperature conditions, but for a 4% PCM content, the effective construction time available under a 5-cm-thick loose covering was 43.1 h. Thus, the use of PCM-clay combined with the upper layer loose covering for temperature control proved feasible and effective. Additionally, by increasing the thickness of the loose covering and the initial temperature of the PCM-clay, the PCM content can be reduced. This provides a theoretical basis and a potential technical solution to maximize the time available for construction and accelerate the construction progress of core-wall rockfill dams.

Shape memory behavior of novel Ethylene Propylene Diene Monomer (EPDM)/paraffin foams

Ethylene Propylene Diene Monomer (EPDM) rubber foams are widely employed for thermal and acoustic insulation in building construction. However, their installation in confined spaces is often complicated, and the capability of EPDM foams to exhibit shape memory behavior could be a desirable property. In the literature, several works have demonstrated that blending elastomeric matrices with paraffin, a well-known Phase Change Material (PCM), could be an interesting method to obtain shape memory polymers with a tunable switching temperature. In this work, EPDM foams filled with paraffin wax, having a melting temperature of 70°C, were produced and characterized from a microstructural and thermo-mechanical point of view. By melt compounding and hot pressing, samples were produced, and the PCM content in the foams was varied between 0 and 60 wt% (with respect to the EPDM matrix). The results of the shape memory tests evidenced the crucial role played by the PCM in providing excellent shape fixability for the expanded rubber. Even a limited amount of paraffin (i.e., 20 wt%) was able to raise the strain fixity parameter to a value higher than 80%, and it reached 100% when the paraffin content was increased to 60 wt%. On the other hand, an increased PCM fraction caused a slower recovery process. Consequently, a compromise between a fast recovery and optimum shape fixability should be accepted. These results are promising for the development of novel thermal and acoustic EPDM insulating foams easier to be installed.

Dynamic Simulations on Enhanced Heat Recovery Using Heat Exchange PCM Fluid for Solar Collector

Facing the goal of carbon neutrality, energy supply chains should be more low-carbon and flexible. A solar chemical heat pump (SCHP) is a potential system for achieving this goal. Our previous studies developed a silicone-oil-based phase-change material (PCM) mixture as a PCM fluid for enhancing heat recovery above 373 K in the solar collector (SC) of the SCHP. The PCM fluid was previously tested to confirm its dispersity and flow properties. The present study proposed a 3D computational fluid dynamics model to simulate the closed circulation loop between the SC and reactor using the PCM fluid. The recovered heat in the SC was studied using several flow rates, as well as the PCM weight fraction of the PCM fluid. Furthermore, the net transportable energy is considered to evaluate the ratio of recovered heat and relative circulation power. As a result, it was verified that the recovered heat of the SC in the experiment and simulation is consistent. The total recovered heat is improved using the PCM fluid. A lower flow rate can enhance the PCM melting mass and the recovered heat although sensible heat amount increases with the flow rate. The best flow rate was 1 L/min when the SC area is 1 m2. Furthermore, the higher PCM content has higher latent heat. On the other hand, the lower content PCM can increase the temperature difference between the SC inlet and outlet because of the lower PCM heat capacity. For the 1 L/min flow rate, 2 wt% PCM fluid has shorter heat-storing time and larger net transportable energy than 0 wt% PCM fluid (426 kJ←403 kJ) for the SCHP unit.

Roles of phase change materials on the morphological, physical, rheological and temperature regulating performances of high-viscosity modified asphalt

The composite of phase change material (PCM) and high-viscosity modified asphalt (HVMA) is expected as a new material regulating the temperature of high-performance pavements, thereby ameliorating the urban heat island effect. This study focused on evaluating the roles of two kinds of PCMs, i.e. paraffin/expanded graphite/high-density polyethylene composite material (PHDP) and polyethylene glycol (PEG), on a series of performances of HVMA. Fluorescence microscopy observations, physical rheological properties tests and indoor temperature regulating tests were conducted to determine the morphological, physical, rheological and temperature regulating performances of PHDP/HVMA or PEG/HVMA composites with various PCM contents prepared by fusion blending. Fluorescence microscopy test results revealed that the PHDP and PEG could be uniformly distributed in HVMA, but their distribution size and morphology were obviously different. Physical test results showed an increase in the penetration values of both PHDP/HVMA and PEG/HVMA compared to the HVMA without PCM. Their softening points did not change significantly with increasing PCM content due to the presence of a high-content of polymeric spatial reticulation. Ductility test reflected that the low-temperature properties of PHDP/HVMA were improved. However, the ductility of PEG/HVMA was much reduced due to the presence of large size PEG particles especially at 15 % PEG content. Rheological results from the recovery percent and non-recoverable creep compliance at 64 °C confirmed that the PHDP/HVMA and PEG/HVMA had excellent high-temperature rutting resistance regardless of PCM contents. Notably, the phase angle results reflected that the PHDP/HVMA was more viscous at 5–30 °C and more elastic at 30–60 °C. By contrast, PEG/HVMA was more elastic at the whole temperature range of 5–60 °C. Lastly but not least, compared to HVMA without PCM, the temperature regulating effect was 4 °C during heating of PHDP/HVMA containing 4 % PHDP and PEG/HVMA containing 15 % PEG, and their delay time were 456 s and 1240 s, respectively.

High thermal inertia mortars: New method to incorporate phase change materials (PCMs) while enhancing strength and thermal design models

This study proposes and tests a new method to incorporate Phase Change Materials (PCMs) into construction materials to increase building envelopes' thermal inertia without causing a decrease in the material's compressive strength. Mortars with three water-to-cement ratios (0.45, 0.55, 0.65) and, therefore, different porosity were used in this study as base materials. Following our novel procedure, PCM was incorporated into the pore structure of hardened samples through immersion into heated PCM in a liquid state and vacuum application for three different vacuum periods (15 min, 1 h, and 4 h). Final porosity, absorbed PCM volume, thermal conductivity, thermal effusivity, and compressive strength were determined. An increase in all studied properties was observed. The maximum enhancement was observed in samples with 0.65 w/c and 4 h of vacuum, which corresponded with the samples with the highest PCM incorporated (7.01 % of PCM by sample volume). This maximum increase was 17.86 % in thermal conductivity, 24.68 % in thermal effusivity, and 22.59 % in compressive strength. Besides, estimation models for the thermal properties and compressive strength were developed, showing high accuracy (errors lower than 10 %). These estimation models were combined to create a target-by-design system that determines the initial porosity and PCM content required to obtain a desired combination of compressive strength and thermal conductivity or effusivity. The thermal conductivity and effusivity of the solid part of the mortar (excluding the air) were obtained based on these models. These values can be very useful as an input for simulating the thermal behavior of cementitious composites using computational models.

Effect of latent heat storage on thermal comfort and energy consumption in lightweight earth-based housings

Embedding PCMs in building materials has attracted great interest due to their ability to store thermal energy. Storage of heat and cold is an efficient way to save energy. Considering a lightweight earth-based material, mixture of soil with a high straw content, the present work aims to improve its thermal properties by using phase change materials (PCM). In this investigation, a laboratory experimental campaign and subsequent numerical analysis were carried out to examine the impact of incorporating PCM within the lightweight earth-based material. Materials' hygro-thermal properties (thermal conductivity, specific heat capacity and water vapor permeability), determined experimentally in laboratory, have been considered to calculate energy consumption and occupant's comfort in a typical single-family housing. Experimental results showed an improvement of the lightweight earth-based material thermal conductivity and specific heat capacity, as well as a slight reduction in its water vapor permeability depending on the PCM content. These modifications in the lightweight earth-based material properties lead to predict an improvement of occupants' thermal comfort and a reduction of energy consumption in buildings that will be made with such a material. Finally, this study underlined the existence of an optimal phase change temperature regarding climate in which the building evolves.

Numerical analyses of energy screw pile filled with phase change materials

Embedding heat exchangers into a screw pile can form a cost-effective energy pile with a fast installation capability. However, better solutions to handle thermal waves and thermal interferences among energy piles are still required. This work aims to solve the issues by proposing a novel concept of an energy screw pile filled with mixtures of phase change materials (PCM) such as paraffin and “solid” grouting. Numerical simulations are conducted to investigate the utilisation of PCM energy screw piles on reducing fluid and ground temperatures, considering different constituents in PCM-solid mixtures, moisture conditions, phase change temperatures Tpc and operation schemes. Results demonstrate that a mixture with higher effective thermal conductivity λeff slows down the PCM phase transition and results in a lower fluid temperature feeding the ground source heat pump (GSHP). Dry mixtures with higher PCM content benefit the fluid temperature reduction, while a lower PCM content in a wet mixture is also satisfactory. Higher specific heat capacity allows pile back-filling to absorb more heat and reduce the thermal radius of influence, while over-enhancing its λeff might worsen thermal interference. The selection of the PCM phase change temperature Tpc should comply with the GSHP system operation scheme and the project aim.

Effects of paraffin additives, as phase change materials, on the behavior of a traditional lime mortar

This study refers to the inclusion of phase change materials (PCMs) in porous building materials as an alternative means of improving their thermal behavior, assessing the changes caused in their physical–mechanical and durability properties. Specifically, an organic paraffin wax was selected for direct incorporation into lime mortars using different concentrations by weight. The results show that PCMs improve the thermal properties of the mortar while reducing its accessible porosity. This increases the mortars’ resistance to water and soluble salts. However, excessive PCM content causes stresses within the mortar that can jeopardize its structure.

Low temperature energy storage by bio-originated calcium alginate-octyl laurate microcapsules

Octyl laurate phase change material (PCM) was microencapsulated by calcium alginate for eco-friendly low temperature energy storage. The PCM microcapsules were prepared by repeated interfacial coacervation followed by crosslinking method. In order to enhance the antibacterial properties of the as prepared capsules, the calcium alginate shell was functionalized by Ag nanoparticles. Calcium alginate-octyl laurate microcapsules possessed high latent heat of fusion values (130.8 and 128.6 J g−1 on melting and cooling, respectively) which did not significantly change when Ag nanoparticles were entrapped in the shell (127.5 and 125.2 J g−1 for melting and freezing enthalpy changes). Based on these values 71.0 and 69.0% maximal PCM content in the microcapsules were determined by the differential scanning calorimetry method. Both of the Ag-loaded and unloaded calcium alginate-octyl laurate PCM capsules maintained the high heat storing capacity after 250 warming and cooling cycles, which proved they did not suffer from leakage after the accelerated thermal test.

Regulating asphalt pavement temperature using microencapsulated phase change materials (PCMs)

The use of phase change materials (PCMs) to regulate pavement temperatures has been previously studied, with the most successful studies using porous aggregates to stabilize the PCMs. However, this technique can lead to issues with PCM leakage and low PCM content. A less studied method is the use of PCM microcapsules, which also presents challenges since most microcapsules are not strong nor stable enough to survive the high temperatures and compressive forces experienced during asphalt mixture production and placement. This work presents a study of the properties of a new commercial microcapsule type with robust walls and high thermal stability, that are expected to overcome the aforementioned issues. Results from differential scanning calorimetry and thermogravimetric analysis confirmed the microcapsules exhibited high latent heats (200 J/g) and are thermally stable below 400 °C. Additionally, approximately 90% of the capsules remained unbroken after being milled at 140 °C for 20 min, suggesting they are capable of withstanding the mixing and compaction stages of asphalt pavement construction. When PCM microcapsules were added to HMA, thermal cycling experiments showed that specimens containing 10 and 20 vol% PCM exhibited temperature lags of 5 to 10 °C from the control mixture, as they approached the PCM melting/freezing temperature. These results confirm the ability of microencapsulated PCMs to regulate asphalt pavement temperature. However, results from measurements conducted at 40 °C and 1 Hz showed a 75% reduction of the dynamic modulus in specimens containing PCM microcapsules, which could indicate that the addition of these materials also affect asphalt mixture stiffness.