Phase Change Systems Research Articles

Molecular dynamics simulation and experimental verification of a biphasic solvent for CO2 capture

In the context of solvent-based carbon capture, researchers and industries are often interested in improvements in the efficiency of CO2 capture along with the reduction in the required energy. This study employs molecular dynamics (MD) simulation based on a reax force field and experimental investigation to study the effects and main mechanisms of a mutual amine absorbent including diethylenetriamine (DETA) and diethylethanolamine (DEEA), accompanied by NMP and water co-solvents, on the performance of CO2 capture in a phase change system. The implementation of time-dependent partial radial distribution functions (TD-PRDF, gαβrtm) and coordination number (CN) analyses revealed the significant formation of C-N bonds between carbon (C) derived from CO2 and nitrogen (N) within the solution. The direct relationship between changes in DETA molar ratios and CO2 loading, coupled with examining the catalytic role of DEEA in facilitating CO2 removal through protonation, has been thoroughly studied with MD. The experimental methodology was followed to validate the MD results. The optimum composition, DETA: DEEA: NMP with a molar ratio of 3:2.5:1, as determined through MD simulations exhibitsgαβr|tm = 9.848, CN=0.403 at tm= 1 ns. The stable C-N absorption bond length is calculated to be between 1.7 and 1.77 Å. Experimental results confirm a CO2 loading capacity of 0.93 mol/mol for this composition.

Bridging Innovations of Phase Change Heat Transfer to Electrochemical Gas Evolution Reactions.

Bubbles play a ubiquitous role in electrochemical gas evolution reactions. However, a mechanistic understanding of how bubbles affect the energy efficiency of electrochemical processes remains limited to date, impeding effective approaches to further boost the performance of gas evolution systems. From a perspective of the analogy between heat and mass transfer, bubbles in electrochemical gas evolution reactions exhibit highly similar dynamic behaviors to them in the liquid-vapor phase change. Recent developments of liquid-vapor phase change systems have substantially advanced the fundamental knowledge of bubbles, leading to unprecedented enhancement of heat transfer performance. In this Review, we aim to elucidate a promising opportunity of understanding bubble dynamics in electrochemical gas evolution reactions through a lens of phase change heat transfer. We first provide a background about key parallels between electrochemical gas evolution reactions and phase change heat transfer. Then, we discuss bubble dynamics in gas evolution systems across multiple length scales, with an emphasis on exciting research problems inspired by new insights gained from liquid-vapor phase change systems. Lastly, we review advances in engineered surfaces for manipulating bubbles to enhance heat and mass transfer, providing an outlook on the design of high-performance gas evolving electrodes.

Highly efficient direct air capture using solid–liquid phase separation in aqueous diamine solution as sorbent

Abstract To reduce climate change, absorbing CO2 directly from the air (DAC) with high-efficient CO2 absorption, low-cost, and environmentally friendly system has been attracted much attention for several decades. In this work, a series of aqueous diamine solutions was examined for 400 ppm CO2 absorption at ambient temperature. The absorbents exhibited CO2 absorption with molar ratio of 1 molCO2/molamine, and aqueous isophorone diamine (IPDA) in particular showed >99% CO2 removal even under a 500 mL min−1 flow of 400 ppm CO2–N2 with the contact rate of 13,761.5 h−1 between CO2 and IPDA aqueous solution and the CO2 absorption rate of 4.46 mmol/L min. A precipitate of carbamic acid of IPDA was formed by reaction with CO2, and the CO2 removal efficiency was enhanced by increasing the solution viscosity by the formation of this precipitate. The CO2 was absorbed in aqueous IPDA solution as carbamic acid of IPDA and bicarbonate/carbonate species, and the absorbed CO2 could desorb by heating under O2-containing gas flow, which indicates our system is applicable to the CO2 condensation for a plant growth. This work provides fundamental information to establishing a solid–liquid phase change system with a high-efficient and environmentally friendly DAC system using aqueous solvent.

Optimization of Na2SO4•10H2O composites for cold storage by D-optimal mixture design

This study delved into the creation of a composite phase-change material (PCM), named SBNSC, for potential application in cold storage air-conditioning systems (8–16°C). The composite PCM was formulated using sodium sulfate decahydrate (Na2SO4·10H2O) as the primary PCM, borax as a nucleating agent, ammonium chloride (NH4Cl) as a temperature control additive, sodium hexametaphosphate as a crystal modifier and carboxymethylcellulose as a thickening agent. The D-optimal mixture design was employed to optimize the composition, and this resulted in the identification of an optimal formulation characterized by the most desirable properties. The thermal properties were evaluated using differential scanning calorimetry and revealed a phase-change temperature of 15.40°C. X-ray diffraction analysis confirmed the crystalline nature of the composite PCM. After 100 cooling and heating cycles, the crystallization temperature was 9.50°C, the melting temperature was 15.50°C and the supercooling degree was 0.70°C. The enthalpy values showed an 11.22% decrease, indicating reliable thermal performance. The study concluded that the optimal formulation (SBNSC) exhibits commendable thermophysical properties, demonstrating its potential for effective application in phase-change cold storage air-conditioning systems.

Thermodynamic and Exergoeconomic Analysis of a Novel Compressed Carbon Dioxide Phase-Change Energy Storage System

As an advanced energy storage technology, the compressed CO2 energy storage system (CCES) has been widely studied for its advantages of high efficiency and low investment cost. However, the current literature has been mainly focused on the TC-CCES and SC-CCES, which operate in high-pressure conditions, increasing investment costs and bringing operation risks. Meanwhile, some studies based on the phase-change CO2 energy storage system also have had the disadvantages of low efficiency and the extra necessity of heat or cooling sources. To overcome the above problems, this paper proposes an innovative compressed CO2 phase-change energy storage system. During the energy charge process, molten salt and water are used to store heat with a smaller temperature difference in heat exchangers, and high-pressure CO2 is reserved in liquid form. During the energy discharge process, throttle expansion is applied to realize the evaporation at room temperature, and CO2 absorbs the reserved heat to improve the power capacity in the turbine and the system energy storage efficiency. The thermodynamic and exergoeconomic studies are performed firstly by using MATLAB. Then, the parametric study based on energy storage efficiency, system unit product cost, and exergy destruction is analyzed. The results show that energy storage efficiency can be improved by lifting liquid CO2 pressure as well as compressor and turbine isentropic efficiencies, and CO2 evaporation pressure has the optimal pressure point. The system unit product cost can be reduced by decreasing liquid CO2 pressure and compressor isentropic efficiency, while CO2 evaporation pressure and turbine isentropic efficiency both have optimal points. Finally, the optimization of two performances is performed by NSGA-II, and they can reach 75.30% and 41.17 $/GJ, respectively. Moreover, the optimal energy storage efficiency is obviously higher than that of other energy storage technologies, indicating the great advantage of the proposed system. This study provides an innovative research method for a new type of large-scale energy storage system.

Sustainability assessment of solar drying systems: a comparative life-cycle analysis of phase-change material-based vs. cylindrical solar dryers

Abstract Solar drying systems are becoming a popular alternative to traditional energy-based drying systems for agricultural products due to their effectiveness and reduced fuel consumption. Although the efficiency of solar drying systems has been thoroughly investigated, their sustainability has not been studied enough. This study aims to fill that gap by conducting a life-cycle assessment of two new solar drying systems built in Udaipur, Rajasthan, India. The environmental implications of an innovative cylindrical solar-assisted drying system and a phase-change material-based solar drying system were evaluated using cradle-to-gate life-cycle analysis. The study uses the ReCiPe 2016 endpoints (H) technique to calculate various aspects such as midpoint, endpoint, single score, normalization result, and network diagram for phase-change material-based solar drying and cylindrical solar-assisted drying. Results show that phase-change material-based solar drying has an average of 40% more impact on the environment than cylindrical solar-assisted drying, with a high impact found in human non-carcinogenic toxicity, mainly due to the production of phase-change materials. However, cylindrical solar-assisted drying system crossover phase-change material based solar drying in terms of its impact on human carcinogenic toxicity and fossil resource scarcity. The contribution to global warming of phase-change material-based solar drying is 13.7% more than that of cylindrical solar-assisted drying. The endpoint characterization indicates that phase-change material-based solar drying exceeds in terms of human health (40%) and ecosystem (37.04%), whereas cylindrical solar-assisted drying surpasses phase-change material-based solar drying in terms of impacts on resources, at 14%. The early drying in phase-change material-based solar drying makes up for its higher impact than that in cylindrical solar-assisted drying, which takes 3 hours longer to dry. This study offers guidance and methods for making the best choice of solar-powered dryers.

Thermally radiative bioconvective nanofluid flow on a wavy cylinder with buongiorno model: A sensitivity analysis using response surface methodology

The significant impact of nanotechnology has turned the ordinary into the excellent in the ever-changing environment of science and technology. Recent times have seen a dramatic transformation as advances in science and technology continue to push us into the domain of nanoscale innovation. Fluid flow over a range of geometries is involved in the physical processes of heat and mass transfer subject to the constraints. These phase change systems are also converted into the latest technology by improving the thermal conductivity of the fluids through the mixing of nanoparticles in the ordinary base fluid. This approach makes things finer and quicker from the perspective of efficiency and structure. It has many applications in various domains especially in nano-medicines, chemotherapy, microprocessors, refrigeration, and biotechnology. In this work, nanofluid flow through a wavy cylinder is considered in the existence of thermal radiation, activation energy, and motile microorganisms. The physical model is computationally solved by developing a system of PDE's (partial differential equations) and then transformed into ODE's (ordinary differential equations) by the smooth implementation of similarity variables. The resultant ODE's numerically treated by the bvp4c built package of MATLAB and get the required results. These results are discussed and graphically visualized in the analysis section. For the validation of results, the statistical approach is implemented on the acquired results and shows the fitted model, contour plots, surface plots, residual plots, and streamlines of the involved parameters and their impacts on the model. The impact of involving physical quantities on flow velocity, thermal, concentration, and microorganism's density profiles also discussed. From the results, it is noted that the velocity profile increases by increasing the counts of mixed convection. Thermal distribution enhanced due to boosting the values of thermophoresis and Brownian motion. The concentration of nanoparticles increased by increasing the magnetic field strength. The larger values of peclet number minimize the density of microorganisms. Skin friction coefficient is increased by around 28% and mass transport going to be increased by 36% due to the existence of microorganisms. The analysis of variance shows that our model is significant and the fitted summary also shows the fitness of model.

Optimization and characterization of fatty acids based ternary eutectic phase change system

Phase change materials (PCMs) in the pavement can mitigate the urban heat island effect and regulate pavement temperature. In this work, thirteen ternary eutectic PCMs (TEPCMs) were developed by melt-blending pure components, including adipic acid (ADA), sebacic acid (SEA), butyramide (BU), stearic acid (SA), palmitic acid (PA), myristic acid (MA), lauric acid (LA), and methyl stearate (MS). The eutectic phase diagrams were created using the Schrader equation to identify the eutectic points for these TEPCMs. Several tests were performed to assess their phase-change behaviors, chemical structure, crystallization performance, crystalline structure, and thermal stability. The results demonstrated that the lowest eutectic points of 20 TEPCMs were accurately derived from phase diagrams. Theoretical enthalpies of these TEPCMs ranged from 169.69 J/g to 221.73 J/g, with the lowest estimated eutectic point between 28.5 °C and 85.57 °C. While the measured enthalpies of TEPCMs were lower than their theoretical values. For instance, the enthalpy disparities of AD/SE/MA, BU/SA/MA, and BU/PA/MA were 35.12 J/g, 34.29 J/g, and 28.89 J/g, respectively. The phase-change temperatures of developed TEPCMs ranged from 25.62 °C to 63.84 °C, while the enthalpy values ranged from 152.44 J/g to 231.52 J/g. Furthermore, developed TEPCMs exhibited outstanding chemical stability and stable crystal structure, surpassing those of the individual components, thereby displaying lower phase-change temperatures. Consequently, targeting the high-temperature conditions during asphalt pavement construction, specific TEPCMs were recommended for temperature regulation in asphalt pavements, such as AD/SE/SA, AD/SE/PA, AD/SE/MA, SA/PA/MA, SA/PA/LA, SA/PA/MS, SA/MA/LA, and SA/MA/MS, which are suitable for all types of asphalt pavements.

Confined Vertical Foaming Induces Graphite Crystal Orientation: Exceptional Isotropy of Thermal Conductivity and Anti-Leakage Properties for Phase Change Systems

Phase Change Materials (PCMs) are increasingly recognized for their pivotal role in thermal regulation but hindered by low thermal conductivity (TC) and leakage issues. Efforts to improve their thermal performance...

Mitigation of freeze-thaw damage to open-graded friction courses in seasonal climate areas via a binary phase change system

For the road performance deterioration of the open-graded friction courses (OGFCs) due to the scenarios of rainfall, snowfall, rapid temperature change, large temperature difference, and freeze-thaw cycle in seasonal climate areas, it will be necessary to utilize new techniques for improving the temperature regulation capability and freeze-thaw damage resistance of OGFC mixtures. A combined technique of mixing simultaneously two microencapsulated phase change materials (MPCMs) with different phase change temperature ranges and proportions has a special attractiveness for asphalt pavement. Successful application of a binary phase change system concept to improving asphalt pavement temperature regulation still has many problems, such as environmental conditions, coating MPCMs with Portland cement, mixing contents and proportions of different MPCMs, and factors affecting the temperature regulation capability and improving the freeze-thaw damage resistance of OGFCs. Composite MPCMs (CMPCMs) were prepared by two MPCMs of P46 and P5 coated by cement, in which P46 and P5 use paraffin and n-tetradecane respectively as the core material and SiO2 as the shell. The heating, cooling, freeze-thaw, and uniaxial compression tests on CMPCM-OGFC specimens were performed, to evaluate the temperature regulation capability of OGFC mixtures with different contents and proportions and the dependences of compressive strength, strength loss rate, and strain of OGFC mixtures on freeze-thaw cycle. The results reveal that the OGFC mixtures with different CP46 contents have a cooling effect due to the phase change heat absorption in a higher temperature range during the rising temperature and with different CP5 contents have a warming effect due to the phase change heat release in a lower temperature range during the cooling temperature. After mixing simultaneously CP46 and CP5 in different proportions, the temperature regulation capability of mixtures with a 3% content has a great improvement due to triggering respectively two types of phase change effects in a higher temperature range for CP46 and in a lower temperature range for CP5. Adopting this binary phase change system as mixing CP46 and CP5 can reduce the rising/cooling temperature rates in the freeze-thaw process and mitigate the damage of OGFC mixtures due to the high-temperature thawing and low-temperature frost heave effects.

Enhancing paraffin wax crystallization and investigating thermo-physical properties of ethylene-propylene-diene monomer/paraffin wax/silica phase change system: The influence of silica nanoparticles

Nowadays, phase change systems play a crucial role in thermal energy storage applications. However, key challenges persist in these systems, namely achieving a higher phase change enthalpy while minimizing leakage of the phase change materials (PCMs). This study focuses on investigating the thermo-physical properties of a phase change composite comprising Paraffin Wax (PW) and silica nanoparticles. The objective is to enhance the thermal efficiency of an ethylene-propylene-diene monomer (EPDM) rubber/PW PCM/silica composite by utilizing silica nanoparticles as nucleating agents to promote the crystallinity of PW PCM. The results demonstrate that the incorporation of 0.4 wt% silica nanoparticles maximizes the crystallinity of PW PCM, coinciding with the threshold for particle aggregation within the PW PCM matrix. Furthermore, a lower crosslink density in the rubber matrix facilitates a higher loading of PW PCM (197 %) and mitigates leakage (1.36 %). Thermo-physical analysis of the composite materials reveals that the presence of silica nanoparticles significantly reduces the melting kinetics and enhances the crystallinity of PW PCM. Moreover, the inclusion of silica nanoparticles elevates the energy storage capacity of the EPDM/PW PCM/silica composite by augmenting the heat capacity and substantially reducing the melting and freezing kinetics of PW PCM.

Simulation Study of a Novel Solar Air-Source Heat Pump Heating System Based on Phase-Change Heat Storage

A traditional solar air-source heat pump heating system cannot effectively utilize solar energy, and it consumes large amounts of energy when operating during cold nights. Accordingly, a conventional heating system has been improved by phase-change heating to form a new phase-change thermal storage solar air-source heat pump heating system. Based on the TRNSYS simulation platform, a heating simulation study of the improved phase-change heating system was carried out in Xi’an City. The results show that the addition of phase-change thermal storage technology allows the heating system to make better use of solar energy, and the efficiency of the solar collector is increased by 5.9%; the presence of the phase-change material effectively reduces the rate of temperature drop inside the water tank, making the water supply temperature more stable; during the whole heating period, the improved phase-change heating system saved 484.91 kWh of operating energy, showing a very good energy-saving effect.

Evaluation of Biogas and Solar Energy Coupling on Phase-Change Energy-Storage Heating Systems: Optimization of Supply and Demand Coordination

Biogas heating plays a crucial role in the transition to clean energy and the mitigation of agricultural pollution. To address the issue of low biogas production during winter, the implementation of a multi-energy complementary system has become essential for ensuring heating stability. To guarantee the economy, stability, and energy-saving operation of the heating system, this study proposes coupling biogas and solar energy with a phase-change energy-storage heating system. The mathematical model of the heating system was developed, taking an office building in Xilin Hot, Inner Mongolia (43.96000° N, 116.03000° E) as a case study. Additionally, the Sparrow Search Algorithm (SSA) was employed to determine equipment selection and optimize the dynamic operation strategy, considering the minimum cost and the balance between the supply and demand of the building load. The operating economy was evaluated using metrics such as payback period, load ratio, and daily rate of return. The results demonstrate that the multi-energy complementary heating system, with a balanced supply and demand, yields significant economic benefits compared to the central heating system, with a payback period of 4.15 years and a daily return rate of 32.97% under the most unfavorable working conditions. Moreover, the development of a daily optimization strategy holds practical engineering significance, and the optimal scheduling of the multi-energy complementary system, with a balance of supply and demand, is realized.

Numerical Simulation and Optimization of a Phase-Change Energy Storage Box in a Modular Mobile Thermal Energy Supply System

Featuring phase-change energy storage, a mobile thermal energy supply system (M-TES) demonstrates remarkable waste heat transfer capabilities across various spatial scales and temporal durations, thereby effectively optimizing the localized energy distribution structure—a pivotal contribution to the attainment of objectives such as “carbon peak” and “carbon neutral”. To heighten the efficiency of energy transfer for mobile heating, this research introduces the innovative concept of modular storage and transportation. This concept is brought to life through the development of a meticulously designed modular mobile phase-change energy storage compartment system. Employing computational fluid dynamics (CFD), an in-depth exploration into the performance of the modular M-TES container and the adapted phase-change material (PCM) is conducted. By implementing fin arrangements on the inner wall of the heat storage module, a remarkable upsurge in the liquid phase-transition rate of the phase-change material is achieved in comparison to the design lacking fins—this improvement approximating around 30%. However, it is essential to acknowledge that the augmentation in heat transfer gradually recedes with the proliferation of fins or an escalation in their height. Moreover, the integration of expanded graphite into erythritol emerges as profoundly effective in amplifying the thermal conductivity of the PCM. Notably, with the addition of a 15.2% volume fraction of expanded graphite to erythritol, the duration of heat storage experiences a drastic reduction to nearly 10% of its original duration, thereby signifying a momentous advancement in thermal performance.

Temperature-sensitive and self-healing shape-stable phase change materials containing temperature adjustable ionic liquid for improving the recycling stability and the applicability in cold energy storage

Advanced shape-stable phase change materials (SSPCMs) with environment self-adaptation are becoming more meaningful in regulating temperature in diverse applications. In this manuscript, a series of self-healing SSPCMs containing ionic liquids were fabricated by temperature-responsive polymers (PNIPAM) through the free radical polymerization method. 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) ionic liquid was selected as the cooling agent and PCM. 2-ureido-4[1H]-pyrimidinone (UPy) and chitosan oligosaccharide (COS) were chosen as modifiers. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to determine the chemical structure. The surface morphology of SSPCMs was observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). A rotational rheometer and electronic universal testing machine were used to assess the self-healing effectiveness and mechanical properties of SSPCMs. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the thermal characteristics and thermal reliabilities of self-healing SSPCMs. The results indicate that the self-healing efficiency of SSPCM is 91.04 % within 5 min, and compressive strength is improved by 65.7 % by the ionic liquid. The SSPCMs perform thermo-sensitive properties, which allow SSPCMs to maintain a stable shape in response to temperature change and reduce PCMs leakage. Furthermore, the SSPCMs can quickly and effectively recover their mechanical properties after damage thanks to the excellent self-healing properties. Meanwhile, the SSPCMs have a longer lifespan for improving recycling efficiency and are more environmentally friendly. The developed SSPCMs with recycle stability have a high energy density (251.5 J/g) and adjustable phase change temperature properties. The developed SSPCMs can be made to fit various temperature applications by changing the concentration of ionic liquids in the phase change system. Overall, the SSPCMs show promising potential for cold energy storage and thermal management.

Effects of Geometric Parameters and Heat-Transfer Fluid Injection Direction on Enhanced Phase-Change Energy Storage in Vertical Shell-and-Tube System

Internationally, energy-storage technologies have facilitated the large-scale utilization of renewable energy, reducing reliance on conventional power generation and enhancing energy efficiency. In the pursuit of strengthening the efficiency of phase-change energy-storage systems, the focus lies on further enhancing the efficiency of vertical shell-and-tube energy-storage systems. This study investigates the influence of two different heat-transfer fluid (HTF) injection directions on the melting of phase-change materials (PCM) in a vertical shell-and-tube latent heat storage (LHS) system. The melting behavior of PCM is analyzed under both pure conduction and natural convection conditions. The research findings reveal that during the initial melting stage, both HTF injection methods primarily rely on thermal conduction, resulting in no significant changes in PCM melting. However, in the later stages of natural convection, bottom HTF injection exhibits superior heat-transfer efficiency compared to top injection. Under a constant volume of phase-change material, both pipe length and pipe thickness affect the PCM melting process. As the pipe length increases within the range of 1.6 m to 0.2 m, the PCM melting time also increases. The results show that the melting time of the PCM is reduced by almost 15,000 s when the tube length H exceeds 800 mm, regardless of whether the heat-transfer fluid is injected at the top or bottom. In this paper, we also obtained results that the three composites containing 10% expanded graphite save 5.3%, 10.2%, and 14.3% of melting time, respectively, compared to pure paraffin when H = 200 mm and top injection are considered. For bottom injection, the three composites saved 7.7%, 12.5%, and 17.2% of melting time, respectively. This further emphasizes the more significant effect of priming in improving melting time.

Performance analysis of the phase-change heat-storage tank based on numerical simulation

Phase-change heat storage system contributes to the smooth operations of building energy supply and demand. In this paper, the numerical model of the heat-storage tank with phase change material blocks is established. The charge and discharge process of the heat-storage tank is analyzed with the numerical model. The performances of the heat-storage tank with and without phase change material blocks are compared by experiment and numerical simulation. The effects of structural parameters of phase change material blocks on the heat storage and release rate are comprehensively discussed, including the number and size of phase change material blocks. The results indicate that under the experimental conditions, the charge capacity and duration of the tank with phase change material blocks are extended by 7.43% and 8.3% respectively under the condition of replacing 6.75% volume of hot water with phase change material. The thermal stratification phenomenon in the heat-storage tank without phase change material blocks is more obvious. For certain volume of the phase change material, the performance analysis of three cases with different amount and size of phase change material blocks is investigated. The results show that the phase change material blocks with number and size of 24 and 0.45 m × 0.1 m × 0.1 m reduces the charge and discharge duration by 2.47% and 3.78% compared with those of 12 and 0.9 m × 0.1 m × 0.1 m.

Reversible thermochromic microcapsules with SiO2 shell for indicating temperature and thermoregulation

In this study, we successfully designed and synthesized a series of thermochromic phase change microcapsules with different core-shell ratios. Reversible thermochromic phase-change material systems (TC-PCMs) with excellent color-change performance were prepared as the core materials by selecting the components of the three-component thermochromic compound, and then the SiO2 shell was assembled on the interface of TC-PCMs droplets in oil-water emulsion by interfacial polymerization. The microstructure and chemical composition of the resulting microcapsules were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). SEM images showed that these microcapsules have spherical shape and well-defined core-shell structure. According to differential scanning calorimeter (DSC) and thermogravimetric analysis (TG) tests, these bifunctional microcapsules exhibited excellent heat storage and release properties, high heat storage capacity and good thermal stability. The melting and solidifying enthalpies of microPCMs were 181.3 J/g and 174.5 J/g, respectively. In addition, the resulting microcapsules have good thermochromic reversibility with a color transition temperature of 52 °C. The thermal conductivity of TC-PCMs was enhanced by 132.4 % after loading SiO2 shells. Furthermore, these microcapsules exceeded the target temperature and successfully achieved the thermochromic function. The bifunctional microcapsules developed in this study have great potential for application in textiles, smart material coatings, luminescent thermal sensors and anti-counterfeiting.

Numerical Study of a High-Temperature Latent Heat Thermal Energy Storage Device with AlSi12 Alloy

This paper explores the potential of thermal storage as an energy storage technology with cost advantages. The study uses numerical simulations to investigate the impact of adding porous material to the HTF side during solidification to improve the heat transfer effect of TES using AlSi12 alloy as the phase-change material. The research also examines the effects of adding porous dielectric materials and increasing air velocity on the discharge temperature, discharge power, and discharge time of high-temperature phase-change energy storage systems. The study found that the temperature difference of the PCM (increased), solidification time (reduced more than 85%), the outlet temperature of the air, and heat discharge power of the LHS did not vary significantly across different porous materials (copper foam, nickel foam, and silicon carbide foam) added to the HTF tube. These findings offer important information for the design of high-temperature phase-change energy storage devices and can guide future developments in this field.

A novel multi-level predictive management strategy to optimize phase-change energy storage and building-integrated renewable technologies operation under dynamic tariffs

In the evolving energy sector, where buildings are recognized as dynamic components of energy networks and smart grids, the implementation of new regulations and guidelines is crucial to optimize the interaction between buildings and the grid. The imperative to reduce building energy consumption facilitates the promotion of new technologies that rely on renewable energy generation and innovative materials. As technology has progressed, the multitude of energy vectors involved has made controlling energy systems increasingly challenging. This poses a barrier to the widespread adoption and implementation of cutting-edge technologies. In this framework, this paper explores an energy-efficient solution using an integrated photovoltaic/thermal collector and an active phase-change material storage system. The study optimizes the integration of technologies through a resistance capacitance model, assessing the impact on thermal comfort, energy savings and costs. A novel cascade methodology, combining particle swarm optimization search with model predictive control, is designed to select the optimal mode of operation for the proposed technologies. The economic feasibility of the proposed system is analyzed across different tariff structures, whereas the interaction with the grid is evaluated using energy flexibility key performance indicators. The energy and economic performance, as well as the flexibility of the system are assessed through a proof-of-concept conducted in an office building scenario. The results demonstrate an increase in energy efficiency, with savings ranging from 9% to 28% compared to a suitable baseline scenario, and a significant energy shift from on-peak to off-peak periods, potentially accounting for up to 46% of the total building load. This energy flexibility enables the grid to receive reduced demand during morning hours.