Building Temperature Regulation Research Articles

Bilateral passive thermal management for dynamical temperature regulation

Space heating and cooling of buildings account for ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document} 30% of energy consumed globally. As a result, efforts to reduce the carbon footprint associated with building temperature regulation are crucial to achieving sustainability goals. Passive radiative cooling and sun heating are two promising innovations that can help reduce the energy consumption associated with building temperature regulation. However, these methods are constrained by factors such as climate zones and seasonal changes. In this work, we demonstrate numerically that bilateral photonic metamaterials enabled by vanadium dioxide (VO2) nanoparticles embedded into polyethylene nanogratings can achieve dynamically modulate solar absorptance at one side in winter and achieve radiative cooling on another side. In cold weather, the solar absorptance of this metastructure can change from 0.93 to 0.2 at a critical temperature when VO2 changes from a metallic to an insulating state. This metastructure consists of broadband transparent polyethylene (PE) gratings on the reflective silver (Ag) gratings with the same period and filling ratio. These gratings are deposited on top of the Polydimethylsiloxane (PDMS) thin film. The VO2 nanoparticles enable dynamic solar absorptance modulation for winter space heating, while the PDMS with strong infrared emittance derived from molecular vibrations over the atmospheric window for summer radiative cooling. Temperature response simulations validate that this bilateral design achieves   6 °C subambient temperature drop at noontime in the summer and stabilizes its temperature around 22 °C during the daytime in the winter. This passive dynamical thermal regulation technique can be deployed for energy-saving targets of buildings, vehicles, and greenhouses in areas with large temperature fluctuations.

Carbonated balsa-based shape-stable phase change materials with photothermal conversion and application in greenhouse

Greenhouse enables to promote plant yield through creating optimal environment. Efficient solar energy conversion and storage is a promising strategy to address energy shortage issue of greenhouse in winter. This paper prepares form-stable composite phase change materials (PCMs) to store solar energy efficiently. Lightweight and porous balsa wood subjected to high-temperature carbonization is designed to simultaneously solve the liquid leakage, enhance the thermal conductivity, and improve the photothermal conversion and thermal energy storage of PCM. OP44E and SEBS are utilized as PCM and thickener, followed by vacuum impregnation into the carbonized balsa wood (CW). Results indicate that carbon content of CW increases with the augment of carbonization temperature. Shaping effects of CW and SEBS endow composite PCMs to have highest adsorption rate of 92.7 wt% with enthalpy over 190 J/g. Composite PCMs reveal reliable thermal properties and thermal stability below 100 °C. Composite PCMs have photothermal conversion larger than 88 % under a xenon lamp radiation. Temperature of PCMs on the shallow layer is higher owing to its photothermal conversion capacity. Greenhouse test indicates that CW/OP44E/SEBS greenhouse gains higher PCM temperature of 71.5 °C at 70 min, compared to 40.3 °C in empty and OP44E/SEBS cases. CW/OP44E/SEBS greenhouse maintaining indoor temperature over 20 °C lasts 15.3 min longer than empty and OP44E/SEBS greenhouses. In addition, form-stable composite PCMs featured with excellent thermal stability and photothermal conversion are capable of maintaining stable indoor temperature of greenhouse, indicating potential in the field of agricultural building temperature regulation.

Thermal storage process of phase change materials under high humidity and laminar natural convection condition: Prediction model and sensitivity analysis

The application of phase change materials (PCMs) in renewable energy storage and building temperature regulation is considered an effective method to reduce the use of fossil fuels and carbon emissions. However, issues concerning the utilization of PCMs in high-humidity environments remain to be addressed to fill the gap in real-world applications. This paper establishes a simplified novel two-zone model, comprehensively considering the natural convection on the surface of the PCP in high-humidity environments, as well as the formation, movement, and evaporation of water films on the surface. Subsequently, numerical solutions and experimental validation are conducted, and the influence of high-humidity environments on the heat and moisture transfer is elucidated. The results indicate that a high-humidity environment can significantly suppress the sensible heat transfer with a ratio range of latent heat to sensible heat typically around 1–4. Furthermore, the increase in the height of PCP leads to an increase in the proportion of sensible heat transfer. On the contrary, increasing the thermal conductivity of the PCM can amplify the latent heat transfer. The results can help further study the thermal storage and the dehumidification potential of phase change units in application on a large scale under high humidity conditions.

Evaluation of phase change material-graphene nanocomposite for thermal regulation enhancement in buildings

The growth of high-efficiency phase change material (PCM) nanocomposites with good heat conduction and substantial thermal capacity was of vital significance for practical matters in the sustainable utilization of energy. A novel leakage-proof n-heptadecane-graphene nanocomposite was prepared by a direct impregnation procedure from n-heptadacne as a PCM and nanographene as a skeleton. The creation of shape-stabilized nanocomposite was checked with X-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) spectroscopy. The scanning electron microscopy (SEM) analysis illustrated that the n-heptadecane and graphene had favourable compatibility and there was no phase separation and graphene accumulation. Thermal analysis showed that the shape-stabilized nanocomposite not only had a good phase transition enthalpy (101.7 J/g) and n-heptadecane content (45.6 %) but also possessed appropriate thermal stability. The heat conduction of the obtained mesoporous nanocomposite was up to 1.527 W/mK, with a growth of 808 % compared to pure n-heptadecane. Furthermore, the optimized nanocomposite held auspicious thermal reliability, being exposed to 400 thermal cycles. Moreover, the thermoregulation tests demonstrated that the gypsum boards containing optimized nanocomposite showed a slow heat release rate and improved the building temperature profile over only the gypsum board. By virtue of the combination of n-heptadecane and thermal conductive nanographene, the obtained engineered nanocomposite might be regarded as a smart material for energy-conserving and temperature regulation in buildings.

Chitosan incorporation for improving the dimensional stability of PLA aerogel encapsulated phase change materials

Chitosan (CH) was utilized to improve the shape stability and load resistance of Polylactic acid (PLA) aerogel encapsulated PCM during phase change. Specifically, PLA aerogel with high porosity (>90 %) was prepared first, and then soaked in ethanol and subsequently CH solution, to functionalize PLA aerogel. The aerogel is used to encapsulate paraffin to obtain a shape-stable bio-based PCM. We conduct a comprehensive analysis of its anti-leakage, shape stability, and phase transition properties. The results showed that the CH-modified PCM kept a high latent heat (169.5 J/g), maintained excellent anti-leakage performance, had stronger resistance to deformation in molten state, and improved anti-leakage performance under load. Combining the convenience and environmental protection of material preparation and modification, and the excellent performance of final PCM, this material is expected to be practically applied in building temperature regulation and solar energy capture.

Energy efficient thermochromic smart windows based on polymers and metal oxides

AbstractThermochromic energy efficient windows dynamically regulate building energy exchange by changing their optical transmittance. Recently, thermochromic materials with different chromic mechanisms are developed to fulfill smart window demands. Advanced fabrication technologies for smart windows also lead to building energy efficiency optimization. In this Perspective, representative mechanisms and performances of promising thermochromic systems, including vanadium dioxide, hydrogels, perovskites, ionic liquids, and liquid crystals, are discussed. Furthermore, the emerging technology of radiative cooling is emphasized for future building energy saving. Building temperature regulation and energy saving based on smart windows will make great impacts on the global low carbon economy.

An introduction to the chalk aquifers of northern Europe

AbstractWe briefly outline the progressive development of approaches to both the characterization and simulation of the hydrogeology of northern European chalk aquifers, which were some of the first in the world to be studied. The volume's scope includes work on water resources and quality, chalk streams and wetland ecosystems, chalks as heat reservoirs for building temperature regulation, sources of groundwater flood risk and impacts of engineering on the subsurface, and diffuse and point-source pollution affecting these aquifers. It excludes hydrocarbon-related studies and those focused on offshore chalk sequences. We briefly outline the current state of knowledge of hydrogeological processes, characterization, assessment and modelling, and the increasingly recognized importance of karst features. The latter were little discussed 20 years ago and are still often neglected. There follows a brief quantitative analysis of publication topics relating to chalk hydrogeology in the scientific literature over the past three decades, which highlights key trends including both the purposes of studies and the methods employed. We present a summary of the topics and contributions within this volume, and conclude by identifying the key issues that need to be addressed in order to ensure the sustainability of our chalk aquifers for the future.

Research on the coordinated control of large permanent magnet direct drive fan and air conditioner based on finite element method

In recent years China has committed to energy saving and emission reduction. Chinese Government has proposed a strategic policy of carbon neutrality. In the context of energy shortage, the development of sustainable cities and green buildings is a major trend. An important part of energy consumption in cities is the energy consumed by temperature regulation in buildings, and reducing this part of energy consumption can be of great help to the development of sustainable cities. In this paper, our team propose a scheme for temperature regulation with large permanent magnet direct drive fans system and air conditioners. Compare the conventional room temperature regulation scheme which only uses air conditioners with the new room temperature regulation scheme which uses the large permanent magnet direct drive fan and air conditioners by simulating the indoor temperature regulation process. The results of simulation show that the new scheme’s temperature regulation effects are more uniform than the conventional scheme. The new scheme can reach the target Comfort Index of Human Body faster than the conventional scheme, and the energy consumption can be reduced by more than 8%. The paper concludes that the new room temperature control solution is more energy efficient, reduces carbon emissions and helps to achieve the carbon neutrality target.

Stress‐gradient framework for green roofs: Applications for urban agriculture and other ecosystem services

Abstract Green roofs are promoted to contribute to more resilient cities by enhancing urban ecosystem services and food systems. Extensive, low‐maintenance green roofs experience frequent environmental stresses, which reduce plant survival and growth. Stress‐tolerant plants are therefore used to sustain well‐established services, such as building temperature regulation. However, transitioning extensive green roofs to provide other key urban services, such as food production, involves less tolerant plant species. Although facilitation exerted by stress‐tolerant species (nurses) has been proposed to improve the performance of stress‐intolerant species (protégés) in extensive green roofs, the conditions under which facilitation could occur are not well understood. Therefore, a comprehensive framework is needed that integrates current knowledge on how the performance of protégé species is affected by nurse plants across stress conditions. We present a framework for green roof research that results in a linear model that integrates (i) modern trait–environment theory and (ii) facilitation ecology in a refined stress‐gradient hypothesis (SGH) originally developed following study of other stressful environments. The model makes testable predictions on how phenotypic traits mediate the performance response of protégé species to nurse plants along stress gradients in extensive green roofs. This is not only useful for the analysis of eco‐physiological performance measures directly linked with multifunctionality and ecosystem services, but also demographic or ‘vital’ rates that drive species persistence and plant community maintenance. We discuss a range of applications related to key agricultural and ecological questions arising from contemporary extensive green roof research, such as enhancing conditions for crop production, weed management, plant invasions and biodiversity conservation. We also provide guidelines for the generation of appropriate data and for fitting this model using readily available statistical procedures. Our framework will allow researchers to assess under which environmental conditions nurse–protégé interactions are feasible. We expect the findings from such research to help develop strategies and guidelines for managing environmental conditions that optimize protégé performances that ultimately affect the delivery of ecosystem services in constructed urban green spaces.

Printable Thermochromic Hydrogel-Based Smart Window for All-Weather Building Temperature Regulation in Diverse Climates.

Thermochromic smart windows are widely developed to modulate building energy exchange to save building energy consumption. However, most smart windows have fixed working temperatures, moderate energy-saving efficiency, and are not suitable for diverse (cold and hot) climates. Here smart windows with strong temperature modulation over a broad range of hydrogels with adjustable transition temperatures for all-weather building temperature regulation in different climates are reported. Thermochromic poly(N-isopropylacrylamide-co-N, N-dimethylacrylamide) hydrogels, with lower critical transition temperatures ranging from 32.5 to 43.5°C, are developed for smart windows with solar modulation up to 88.84% and intrinsic transmittance up to 91.30% over full spectrum without energy input. Simulated indoor investigations are performed in different cities from 23 °N to 39 °N from winter to summer. The results indicate that smart windows have a strong solar modulation in summer to reduce indoor temperature up to 7.3°C and efficient heat conservation in winter to save energy up to 4.30Jm-3 , in comparison to glass windows. Smart windows with grid patterns and Chinese kirigami are fabricated by using 3D printing of the hydrogels to achieve both solar modulation and light incidence. The strategy offers an innovative path for thermochromic smart windows for low carbon economy.

Event‐triggered distributed model predictive control scheme for temperature regulation in multi‐zone air conditioning systems with improved indoor thermal preference indicator

SummaryDriven by the increasing needs in multi‐zone buildings for reducing the air conditioning (A/C) system related energy consumption and increasing the occupants' thermal comfort, an event‐triggered distributed model predictive control (DMPC) scheme for building temperature regulation with improved indoor thermal preference indicator is proposed. To this end, a temperature‐energy model of the A/C system in a zone which considers multiple types of heat transfer, and the system model of the multi‐zone A/C system are derived first. On this basis, an improved indoor thermal preference indicator that trades off the A/C systems related energy consumption with the aggregate thermal comfort of the occupants is proposed for the multi‐zone A/C system, then the optimal indoor temperature set‐points for each zone are determined by using the distributed consensus algorithm. It is followed by an event‐triggered DMPC scheme by adjusting the A/C systems to arrive at the optimal indoor temperature set‐points for all the zones with lower communication and computation load. The performance and effectiveness of the proposed methods are demonstrated through a case study on an actual multi‐zone A/C system.

Development of BaSO4@n-eicosane phase-change microcapsules with high corrosion resistance for thermal regulation application in architectural coatings

Microencapsulated phase change materials (PCMs) are a promising candidate to provide huge opportunities for energy-saving buildings; however, the most usually used shell materials for encapsulation of PCMs, such as CaCO3 and SiO2, have poor corrosion resistance, resulting in a limitation in their practical applications in the architectural field. Focusing on an effective solution to this issue, we have developed a new type of microencapsulated PCM with n-eicosane as a core and BaSO4 as an inorganic shell through emulsion-templated controllable precipitation. The resultant BaSO4@n-eicosane microcapsules exhibit an ellipsoidal morphology and a well-defined core-shell microstructure, together with a satisfactory latent heat capacity of over 100 J/g. The BaSO4 shell contributes high thermal conduction, rapid heat transfer, high acid and alkali resistance, and outstanding thermal cycling stability to the fabricated microcapsules. This can meet the requirement of long-term use in thermal self-regulatory architectural coatings. The developed composite coatings containing the BaSO4@n-eicosane microcapsules exhibit efficient temperature regulation performance along with high hardness, good scratch resistance, and high corrosion resistance. Based on an investigation into the practical application of the composite coatings, the developed composite coatings can be used for the house roof coating to reduce the indoor temperature effectively, indicating good application potential for comfort temperature regulation in energy-saving buildings. This study offers a new approach to develop multifunctional architectural coatings for sustainability.

Economic model predictive control of integrated energy systems: A multi-time-scale framework

An integrated energy system (IES) that comprises diverse operating units typically exhibits time-scale multiplicity in its dynamics, which makes the application of predictive control schemes to such an IES challenging. In this work, a multi-time-scale framework for subsystem decomposition and the corresponding economic model predictive control (EMPC) design is proposed to explicitly address the time-scale-multiplicity and optimal control of IESs. Specifically, a stand-alone IES is considered. According to the time-scale multiplicity, the IES is decomposed into three reduced-order subsystems with slow, medium, and fast dynamics. A composite EMPC (CEMPC) designed based on the subsystems is proposed to dynamically coordinate the operations of the operating units, aiming at meeting customers’ electricity and cooling demands while reducing fuel consumption. In the design of the CEMPC, a zone tracking objective for the building temperature regulation is adopted to maintain thermal comfort, reduce operating costs, and achieve more control degrees of freedom for satisfying the electricity demands. The proposed CEMPC is composed of a short-term distributed EMPC and a long-term EMPC. The short-term distributed EMPC consists of three local EMPCs corresponding to the slow, medium and fast dynamics of the IES. The long-term EMPC optimizes the operations of the IES taking into account long-term forecasts for external conditions. These EMPCs communicate to cooperate in decision-making. Extensive simulations are carried out to evaluate the performance of the proposed CEMPC framework compared with a hierarchical real-time optimization (HRTO) framework. The simulation results show that the proposed CEMPC framework can increase the system’s overall performance by about 5% if set-point tracking is used and by about 30% if zone tracking is incorporated. The proposed CEMPC framework is also much more computationally efficient and reduces the computation time by over 65%. The proposed CEMPC framework fully leverages the capability of each operating unit to provide superior electricity load tracking and economic performance while maintaining customers’ thermal comfort. Our studies also indicate that the proposed zone tracking approach to building temperature significantly enhances the operational flexibility of IESs in satisfying customized requirements.

Thermal analysis of building benefits from PCM and heat recovery- installing PCM to boost energy consumption reduction

Considering the total final consumption as a criterion, the buildings' energy consumption share reaches more than 30%. To reduce it in buildings located in the Middle East, the addition of PCM, economizer, and heat recovery can be helpful. Using numerical methods and applying energy balance to the building, the energy in the building temperature regulation section (TRS) and mechanical air supply system (MASS) was investigated. PCMs of Pure Temp 23, Pure Temp 25, Pure Temp 27, and Pure Temp 29 were integrated into the building under two scenarios. In the first scenario, the temperature inside the building was constant at 23, 24 and 25 °C. Pure Temp 29 which undergoes phase change at 29 °C, when added to the building, less energy was consumed by 17.39 kWh/m2 at 23 °C, 17 kWh/m2 at 24 °C and 16.92 kWh/m2 at setpoint of 25 °C. For next scenario (inside temperature varied between 23 and 25 °C), Pure Temp 29 was also the best by recording the energy saving of 15.52 kWh/m2. To drop energy in the MASS section, an economizer was installed and owing to its activation, lower energy was consumed by 1.92 kWh/m2. Finally, heat recovery was added to the MASS section, and it was observed that this device, with a reduction of 2.77 kWh/m2, can be useful for this part of the building. Owing to installing PV cells on roof, annual electricity generation was 150 kWh per square meter.

Development, characterization and modification of mannitol-water based nanocomposite phase change materials for cold storage

Under the background of low carbon, phase change energy storage technology has been developed rapidly, which is widely used in solar energy utilization, industrial heat recovery, building temperature regulation, and cold chain logistics. In the fields of cold chain logistics, low-temperature phase change materials(PCMs) below 0 °C have great application space. However, the application of PCM in practice is still limited by high undercooling, low thermal conductivity, low cold storage efficiency and poor stability. In this paper, mannitol aqueous solution, which mannitol can reduce the undercooling degree, an organic-inorganic composite PCM, was used as the main energy storage. After adding MgCl2 as cooling agent, a base solution of salt with phase change temperature of −6 °C and latent heat of 240.1 J/g was prepared. In order to improve the thermal conductivity and cold storage efficiency, nano-copper oxide (Nano CuO) and covalently modified hydroxylated multi-walled carbon nanotubes (MWCNT-OH) were added as thermal conductivity enhancers to prepare nano-composite phase change materials (NCPCMs). In order to obtain good dispersion effect in base solution, sodium dodecyl benzene sulfonate (SDBS), polyacrylamide (PAM) and Guar gum (GG) were used as dispersants. The effects of different dispersants on the dispersion of nanoparticles under phase transition behavior were investigated. The results showed that the anionic dispersant SDBS had poor dispersion effect in salt solution, while the polymer dispersant was better than PAM and GG. The thermal properties and cycle stability of NPCMs were also explored and the result show that the phase change system of mannitol/MgCl2@MWCNT-OH/PAM had the best thermal performance, which has the thermal conductivity of 0.685 W/(m K), increased by 18.16 %, and the cold storage time was reduced by 57.3 %. Without supercooling, the NCPCM has high melting enthalpy, high thermal conductivity and good thermal stability, which has a broad development prospect in the field of cold chain.

Water evaporation inspired biomass-based PCM from daisy stem and paraffin for building temperature regulation

The addition of phase change materials (PCMs) to building wall can effectively regulate building temperature. However, the preparation of inexpensive, easily available, and environmentally friendly composite PCMs with high enthalpy is still a great challenge. Herein, inspired by water transportation and capillary evaporation of natural plants, we selected the widely distributed and economically available wild daisy stem as the raw material for the first time to prepare form-stable composite PCMs for building temperature regulation. A hierarchical porous skeleton material was prepared by high temperature carbonization and chemical modification of wild daisy stem, and then it was impregnated with paraffin to obtain a composite PCM. The results show that the chemical modification using ethanol creates a richer pore structure and increases the PCM loading amounts. The obtained composite PCM was thermally, chemically and cyclically stable with the phase change enthalpy and phase change temperature of 213.6 J/g and 40.1 °C, respectively. Finally, the composite was applied to the temperature regulation of buildings, the center temperature of the phase change model was 5.1 °C lower than that of the ordinary house, indicating the building with the addition of the as-prepared PCM to the walls had significant thermal buffering effect under a simulated light compared to ordinary building with rapid temperature change. Thus, the excellent storage capacity of this composite material gives it great potential for application in building temperature regulation.

Size-tunable CaCO3@n-eicosane phase-change microcapsules for thermal energy storage

Phase-change materials can store and release tremendous amounts of latent heat energy in a single storage unit, and they have become a promising candidate for building comfort temperature regulation with a significant energy-saving effect. In this study, we developed a novel type of size-tunable phase-change microcapsules for high-efficient thermal management and temperature regulation in buildings. The phase-change microcapsules were based on an n-eicosane core and a CaCO3 shell and fabricated using an emulsion-templated self-assembly interfacial precipitation method. Their sizes were controlled through regulating the surfactant concentration, resulting in a desired capsule size as well as a well-defined core-shell microstructure and a regular spherical morphology. When the mass ratio of sodium dodecyl sulfate to sulfobetaine varied from 3/2 to 1/1 in the mixed surfactant system, the resultant phase-change microcapsules exhibited a tunable diameter from 740 nm to 1.54 µm together with a significant increase in latent-heat capacity from 100 to 131.5 J/g. The application investigation of the obtained microcapsules in building thermal regulation was performed through incorporating microcapsule samples into cement, employing the resultant cement composites as building envelopes for a model house. The cement composites presented a good ability to regulate the indoor temperature of the model house thanks to the thermal energy storage and latent heat release of the phase-change microcapsules. The model house coated with the cement composites on the roof exhibited a maximum indoor temperature of 47 °C after subjected to the simulated sunlight radiation for 4 h, leading to a decrease in indoor temperature by 5 °C compared to the model house with pure cement. With a rational combination of the phase-change microcapsules and cement, this study provides a promising approach to passive and efficient comfort temperature regulation for green energy-saving building applications.

Indoor temperature regulation and energy consumption inside a working office in building system using a predictive functional control

ABSTRACT This paper presents a novel control approach for indoor temperature regulation in tertiary buildings, based on predictive functional control. The main control objective is to reduce the energy consumption while ensuring the desired thermal comfort of the occupants. The novelty of this approach may perform in the presence of disturbances such occupancy profile, electrical equipment, indoor temperature, surrounding temperatures and weather data. Predictive functional control algorithm consists in using a dynamic model of the process inside the controller in real time in order to anticipate the future behavior of the system. The proposed method is successfully illustrated using an example of temperature control of a working office which is implemented in the SIMBAD toolbox (SIMulator of Buildings and Devices) integrated into the Matlab/Simulink environment. The proposed control compromises a class of control algorithms that utilizes an online process model to optimize the future response of a plant. The efficiency of the proposed control has been validated using good performance indexes for various scenarios. Simulation results revealed a good level of comfort is ensured with a minimum energy (3.2015 kWh), temperature regulation with a very low error, a high level of comfort is generated in the office room during working hours. Thus, demonstrating the validity and effectiveness of this control strategy.

Advanced 3D-printed phase change materials

3D printing strategies provide flexible solutions for complex and programmable thermal management and versatile material integration. 3D-printed composite phase change materials (PCMs) can overcome shape limitations and optimize structures to construct complex object designs for effective thermal management. Recently in Matter, Emily B. Pentzer et al. creatively proposed a facile strategy to print PCM-filled inks with excellent thermal regulation capacity via direct ink writing (DIW) technology without requiring prior encapsulation of PCMs. This 3D printing approach with a simplified manufacturing process and reduced costs facilitates the production of composite PCMs with complex geometries for retrofitting current buildings containing thermal energy storage materials. 3D printing strategies provide flexible solutions for complex and programmable thermal management and versatile material integration. 3D-printed composite phase change materials (PCMs) can overcome shape limitations and optimize structures to construct complex object designs for effective thermal management. Recently in Matter, Emily B. Pentzer et al. creatively proposed a facile strategy to print PCM-filled inks with excellent thermal regulation capacity via direct ink writing (DIW) technology without requiring prior encapsulation of PCMs. This 3D printing approach with a simplified manufacturing process and reduced costs facilitates the production of composite PCMs with complex geometries for retrofitting current buildings containing thermal energy storage materials. Main textHeating, ventilation, and air conditioning (HVAC) systems are the most commonly used method of temperature regulation in residential and commercial buildings. However, the continuing problems of HVAC systems have led to research on alternative materials and technologies. 3D printing as an additive manufacturing technology is capable of manufacturing multi-scale, multi-material, and multi-functional three-dimensional structures with ultra-high precision and ultra-high flexibility. This technology is expected to facilitate the integration of nanoencapsulated phase change materials (PCMs) for advanced multi-functional conceptual devices. The most popular nanoencapsulated composite PCMs are usually composed of nanoporous supporting materials and PCMs, thus guaranteeing their shape stability, leak-proof capability, and customizable thermal/electrical conductivity.1Chen X. Tang Z. Liu P. Gao H. Chang Y. Wang G. Smart utilization of multifunctional metal oxides in phase change materials.Matter. 2020; 3: 708-741Abstract Full Text Full Text PDF Scopus (48) Google Scholar,2Chen X. Gao H. Tang Z. Dong W. Li A. Wang G. Optimization strategies of composite phase change materials for thermal energy storage, transfer, conversion and utilization.Energy Environ. Sci. 2020; 13: 4498-4535Crossref Google Scholar Recently, nanoporous composite PCMs and related devices have been developing toward intelligence, multi-functionality, flexibility, and refinement. Specifically, composite PCMs with freely designed shapes and structures are definitely smarter in thermal energy management, wearable devices, and shape memory materials. However, the production of flexible lumped composite PCMs is still a big challenge because traditional manufacturing techniques are usually limited to post-impregnation strategies.3Aftab W. Huang X. Wu W. Liang Z. Mahmood A. Zou R. Nanoconfined phase change materials for thermal energy applications.Energy Environ. Sci. 2018; 11: 1392-1424Crossref Google Scholar,4Shchukina E.M. Graham M. Zheng Z. Shchukin D.G. Nanoencapsulation of phase change materials for advanced thermal energy storage systems.Chem. Soc. Rev. 2018; 47: 4156-4175Crossref PubMed Google Scholar Attractively, 3D printing strategies offer flexible solutions for complex and programmable composite PCMs. Different from traditional manufacturing methods, 3D printing can produce shape-changing composite PCMs without leakage, which is an important step toward the application of flexible devices.Direct ink writing (DIW) technology has widespread application prospects in 3D printing. Actually, designing viscoelastic inks with shear-thinning behavior is critical during the extrusion-based printing process.5Ma J. Ma T. Cheng J. Zhang J. 3D printable, recyclable and adjustable comb/bottlebrush phase change polysiloxane networks toward sustainable thermal energy storage.Energy Storage Mater. 2021; 39: 294-304Crossref Scopus (23) Google Scholar If the viscosity, surface tension, shear yield stress, shear elasticity, and loss modulus of the ink can be adjusted appropriately, direct printing of nanoencapsulated PCMs will be possible. Currently, numerous concentrated nanomaterial dispersions, such as graphene oxide and MXene, have been developed for DIW due to their extraordinary high viscoelasticity.6Zhang Y. Zhu G. Dong B. Wang F. Tang J. Stadler F.J. Yang G. Hong S. Xing F. Interfacial jamming reinforced Pickering emulgel for arbitrary architected nanocomposite with connected nanomaterial matrix.Nat. Commun. 2021; 12: 111Crossref Scopus (16) Google Scholar If PCMs are incorporated into the printable matrix (such as graphene oxide and MXene), the corresponding 3D-printed composite PCMs will shine in photothermal energy conversion and storage. More interestingly, the thermal performance of composite PCMs can be improved by optimizing the combination of nanomaterials and optimizing the printing geometry. For example, octadecane/graphene phase change microlattices with a bean pod structure can facilitate light propagation throughout the phase change microlattices, thus realizing the rapid collection and transfer of solar thermal energy.7Yang Z. Jia S. Niu Y. Lv X. Fu H. Zhang Y. Liu D. Wang B. Li Q. Bean-pod-inspired 3D-printed phase change microlattices for solar-thermal energy harvesting and storage.Small. 2021; 17: e2101093Crossref Scopus (18) Google ScholarAdvanced building materials and infrastructure are benefiting from 3D printing technology. This technology provides a platform for facilitating the integration of nanoencapsulated PCMs in advanced phase change building materials. Advanced thermal management based on PCMs for passive control of building heating and cooling can reduce energy losses, which is of great strategic importance.8Song M. Niu F. Mao N. Hu Y. Deng S. Review on building energy performance improvement using phase change materials.Energy Build. 2018; 158: 776-793Crossref Scopus (231) Google Scholar Recently in Matter, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar creatively proposed a facile DIW technique to produce and print PCM-filled inks with excellent thermal regulation capacity that utilized spherical PCM particles as a viscosity modifier in a photocurable, leak-proof resin matrix. PCM beads were prepared by being emulsified at high temperature, dispersed in commercially available acrylate resins, printed, and cured with UV light. As shown in Figure 1A, the purposes of PCM beads were modifying ink rheology and imparting thermal management function. Photopolymerization realized the elastic sealing of PCMs without the use of shell materials. Based on this design concept, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar successfully printed inks (up to 63% PCMs) with excellent thermal regulation capacity and virtually no leakage during multiple melting and solidifying cycles. In addition, versatile PCMs with different phase transition temperatures (eicosane, paraffin, and hexatriacontane) can be simultaneously integrated into the resin and printed without compromising integrity. The rheological properties of the ink are critical in 3D printing. Specifically, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar conducted a preliminary evaluation of viscosity and yield stress of inks with different PCM loading levels for printability. Incorporating PCM beads into the resin imparted shear-thinning behavior, i.e., viscosity decreases with increasing shear rate. Generally, the increase filler concentration enhanced the viscosity, but had little influence on the magnitude of the shear-thinning behavior, indicating that inks can be formulated to attain optimal thixotropic behavior for DIW printing because the materials were sheared during the extrusion process. Increasing the loading level of PCM beads can strengthen the yield stress, which improves the ink’s ability to maintain its shape after extrusion. However, indiscriminately increasing the loading level of PCMs will cause the granular ink to fail to form a uniform paste. Therefore, an upper limit of the loading level of PCMs exists for printable compositions.As is well known, solid-liquid PCMs suffer from loss of integrity and volume change limitations during melting. The traditional solution is the microencapsulation of PCMs. Such rigid PCM microcapsules can be integrated into building materials to produce monolithic structures.10Zhu N. Li S. Hu P. Wei S. Deng R. Lei F. A review on applications of shape-stabilized phase change materials embedded in building enclosure in recent ten years.Sustain. Cities Soc. 2018; 43: 251-264Crossref Scopus (70) Google Scholar However, the shell materials have a negative impact on the thermal energy storage density. In this work, 3D printing technology harnesses the advantages of DIW and eliminates the inherent issues of current microencapsulation techniques (fluid leakage upon volume change) for facilitating the incorporation of PCMs into building materials, thus simplifying the manufacturing process. A limited temperature regulation range is another challenge of single PCMs. Since the ink formulation is not dependent on the chemical properties of PCMs, multiple PCMs can be simultaneously integrated into a single ink, allowing for a wider operating temperature window and promoting its thermal management capability. Ultimately, the authors 3D printed hollow house models with PCM-filled ink serving as effective thermal buffers in the melting temperature range of PCMs. Compared with houses without PCMs, 3D-printed PCM-based houses mitigated temperature fluctuations with a 10% lower temperature during heating and a 40% higher temperature during cooling (Figure 1B). This method does not require microencapsulation of PCMs before they are integrated into the composite materials, thereby using off-the-shelf structural materials to achieve effective passive thermal management and reducing the manufacturing costs.Generally, this study shows how to use 3D printing technology to encapsulate PCMs for thermal management of building materials. The excellent adaptability of DIW makes this strategy compatible with a wide range of photopolymer matrices and PCMs without prior microencapsulation of PCMs. 3D printing technology is capable of adjusting the loading levels of different PCMs particles to achieve the desired thermal management capability. However, the energy storage density of composite PCMs used for residential thermal regulation in this study needs to be further improved to boost the thermal regulation capability. Selecting appropriate PCMs is the key to the development of high-performance phase change building materials. Priority should be given to PCMs with suitable phase change temperature to reach the appropriate ambient temperature for human comfort, and to PCMs with larger latent heat to store or release more heat during the phase change process. Enhanced thermal conductivity, excellent reversibility, and small amounts of expansion and contraction should also be considered. In addition, the preparation process of phase change building materials should also be simplified. Future efforts should aim to balance the mechanical properties, thermal energy storage density, and practical engineering applications of phase change building materials, thus enabling design of advanced thermal management systems that satisfy commercial technical requirements. In conclusion, 3D printing technology offers the ability to produce objects with complex geometries, and it allows the integration of thermal energy storage materials into existing buildings. It is noteworthy that there are fewer reported applications of 3D printing for reliable and efficient thermal energy storage. Therefore, it is highly desirable to explore and implement a suitable combination of PCM encapsulation technology and 3D printing technology to simultaneously satisfy requirements for efficient thermal energy storage, scalable manufacturing, and leak-proof capability. Main textHeating, ventilation, and air conditioning (HVAC) systems are the most commonly used method of temperature regulation in residential and commercial buildings. However, the continuing problems of HVAC systems have led to research on alternative materials and technologies. 3D printing as an additive manufacturing technology is capable of manufacturing multi-scale, multi-material, and multi-functional three-dimensional structures with ultra-high precision and ultra-high flexibility. This technology is expected to facilitate the integration of nanoencapsulated phase change materials (PCMs) for advanced multi-functional conceptual devices. The most popular nanoencapsulated composite PCMs are usually composed of nanoporous supporting materials and PCMs, thus guaranteeing their shape stability, leak-proof capability, and customizable thermal/electrical conductivity.1Chen X. Tang Z. Liu P. Gao H. Chang Y. Wang G. Smart utilization of multifunctional metal oxides in phase change materials.Matter. 2020; 3: 708-741Abstract Full Text Full Text PDF Scopus (48) Google Scholar,2Chen X. Gao H. Tang Z. Dong W. Li A. Wang G. Optimization strategies of composite phase change materials for thermal energy storage, transfer, conversion and utilization.Energy Environ. Sci. 2020; 13: 4498-4535Crossref Google Scholar Recently, nanoporous composite PCMs and related devices have been developing toward intelligence, multi-functionality, flexibility, and refinement. Specifically, composite PCMs with freely designed shapes and structures are definitely smarter in thermal energy management, wearable devices, and shape memory materials. However, the production of flexible lumped composite PCMs is still a big challenge because traditional manufacturing techniques are usually limited to post-impregnation strategies.3Aftab W. Huang X. Wu W. Liang Z. Mahmood A. Zou R. Nanoconfined phase change materials for thermal energy applications.Energy Environ. Sci. 2018; 11: 1392-1424Crossref Google Scholar,4Shchukina E.M. Graham M. Zheng Z. Shchukin D.G. Nanoencapsulation of phase change materials for advanced thermal energy storage systems.Chem. Soc. Rev. 2018; 47: 4156-4175Crossref PubMed Google Scholar Attractively, 3D printing strategies offer flexible solutions for complex and programmable composite PCMs. Different from traditional manufacturing methods, 3D printing can produce shape-changing composite PCMs without leakage, which is an important step toward the application of flexible devices.Direct ink writing (DIW) technology has widespread application prospects in 3D printing. Actually, designing viscoelastic inks with shear-thinning behavior is critical during the extrusion-based printing process.5Ma J. Ma T. Cheng J. Zhang J. 3D printable, recyclable and adjustable comb/bottlebrush phase change polysiloxane networks toward sustainable thermal energy storage.Energy Storage Mater. 2021; 39: 294-304Crossref Scopus (23) Google Scholar If the viscosity, surface tension, shear yield stress, shear elasticity, and loss modulus of the ink can be adjusted appropriately, direct printing of nanoencapsulated PCMs will be possible. Currently, numerous concentrated nanomaterial dispersions, such as graphene oxide and MXene, have been developed for DIW due to their extraordinary high viscoelasticity.6Zhang Y. Zhu G. Dong B. Wang F. Tang J. Stadler F.J. Yang G. Hong S. Xing F. Interfacial jamming reinforced Pickering emulgel for arbitrary architected nanocomposite with connected nanomaterial matrix.Nat. Commun. 2021; 12: 111Crossref Scopus (16) Google Scholar If PCMs are incorporated into the printable matrix (such as graphene oxide and MXene), the corresponding 3D-printed composite PCMs will shine in photothermal energy conversion and storage. More interestingly, the thermal performance of composite PCMs can be improved by optimizing the combination of nanomaterials and optimizing the printing geometry. For example, octadecane/graphene phase change microlattices with a bean pod structure can facilitate light propagation throughout the phase change microlattices, thus realizing the rapid collection and transfer of solar thermal energy.7Yang Z. Jia S. Niu Y. Lv X. Fu H. Zhang Y. Liu D. Wang B. Li Q. Bean-pod-inspired 3D-printed phase change microlattices for solar-thermal energy harvesting and storage.Small. 2021; 17: e2101093Crossref Scopus (18) Google ScholarAdvanced building materials and infrastructure are benefiting from 3D printing technology. This technology provides a platform for facilitating the integration of nanoencapsulated PCMs in advanced phase change building materials. Advanced thermal management based on PCMs for passive control of building heating and cooling can reduce energy losses, which is of great strategic importance.8Song M. Niu F. Mao N. Hu Y. Deng S. Review on building energy performance improvement using phase change materials.Energy Build. 2018; 158: 776-793Crossref Scopus (231) Google Scholar Recently in Matter, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar creatively proposed a facile DIW technique to produce and print PCM-filled inks with excellent thermal regulation capacity that utilized spherical PCM particles as a viscosity modifier in a photocurable, leak-proof resin matrix. PCM beads were prepared by being emulsified at high temperature, dispersed in commercially available acrylate resins, printed, and cured with UV light. As shown in Figure 1A, the purposes of PCM beads were modifying ink rheology and imparting thermal management function. Photopolymerization realized the elastic sealing of PCMs without the use of shell materials. Based on this design concept, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar successfully printed inks (up to 63% PCMs) with excellent thermal regulation capacity and virtually no leakage during multiple melting and solidifying cycles. In addition, versatile PCMs with different phase transition temperatures (eicosane, paraffin, and hexatriacontane) can be simultaneously integrated into the resin and printed without compromising integrity. The rheological properties of the ink are critical in 3D printing. Specifically, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar conducted a preliminary evaluation of viscosity and yield stress of inks with different PCM loading levels for printability. Incorporating PCM beads into the resin imparted shear-thinning behavior, i.e., viscosity decreases with increasing shear rate. Generally, the increase filler concentration enhanced the viscosity, but had little influence on the magnitude of the shear-thinning behavior, indicating that inks can be formulated to attain optimal thixotropic behavior for DIW printing because the materials were sheared during the extrusion process. Increasing the loading level of PCM beads can strengthen the yield stress, which improves the ink’s ability to maintain its shape after extrusion. However, indiscriminately increasing the loading level of PCMs will cause the granular ink to fail to form a uniform paste. Therefore, an upper limit of the loading level of PCMs exists for printable compositions.As is well known, solid-liquid PCMs suffer from loss of integrity and volume change limitations during melting. The traditional solution is the microencapsulation of PCMs. Such rigid PCM microcapsules can be integrated into building materials to produce monolithic structures.10Zhu N. Li S. Hu P. Wei S. Deng R. Lei F. A review on applications of shape-stabilized phase change materials embedded in building enclosure in recent ten years.Sustain. Cities Soc. 2018; 43: 251-264Crossref Scopus (70) Google Scholar However, the shell materials have a negative impact on the thermal energy storage density. In this work, 3D printing technology harnesses the advantages of DIW and eliminates the inherent issues of current microencapsulation techniques (fluid leakage upon volume change) for facilitating the incorporation of PCMs into building materials, thus simplifying the manufacturing process. A limited temperature regulation range is another challenge of single PCMs. Since the ink formulation is not dependent on the chemical properties of PCMs, multiple PCMs can be simultaneously integrated into a single ink, allowing for a wider operating temperature window and promoting its thermal management capability. Ultimately, the authors 3D printed hollow house models with PCM-filled ink serving as effective thermal buffers in the melting temperature range of PCMs. Compared with houses without PCMs, 3D-printed PCM-based houses mitigated temperature fluctuations with a 10% lower temperature during heating and a 40% higher temperature during cooling (Figure 1B). This method does not require microencapsulation of PCMs before they are integrated into the composite materials, thereby using off-the-shelf structural materials to achieve effective passive thermal management and reducing the manufacturing costs.Generally, this study shows how to use 3D printing technology to encapsulate PCMs for thermal management of building materials. The excellent adaptability of DIW makes this strategy compatible with a wide range of photopolymer matrices and PCMs without prior microencapsulation of PCMs. 3D printing technology is capable of adjusting the loading levels of different PCMs particles to achieve the desired thermal management capability. However, the energy storage density of composite PCMs used for residential thermal regulation in this study needs to be further improved to boost the thermal regulation capability. Selecting appropriate PCMs is the key to the development of high-performance phase change building materials. Priority should be given to PCMs with suitable phase change temperature to reach the appropriate ambient temperature for human comfort, and to PCMs with larger latent heat to store or release more heat during the phase change process. Enhanced thermal conductivity, excellent reversibility, and small amounts of expansion and contraction should also be considered. In addition, the preparation process of phase change building materials should also be simplified. Future efforts should aim to balance the mechanical properties, thermal energy storage density, and practical engineering applications of phase change building materials, thus enabling design of advanced thermal management systems that satisfy commercial technical requirements. In conclusion, 3D printing technology offers the ability to produce objects with complex geometries, and it allows the integration of thermal energy storage materials into existing buildings. It is noteworthy that there are fewer reported applications of 3D printing for reliable and efficient thermal energy storage. Therefore, it is highly desirable to explore and implement a suitable combination of PCM encapsulation technology and 3D printing technology to simultaneously satisfy requirements for efficient thermal energy storage, scalable manufacturing, and leak-proof capability. Heating, ventilation, and air conditioning (HVAC) systems are the most commonly used method of temperature regulation in residential and commercial buildings. However, the continuing problems of HVAC systems have led to research on alternative materials and technologies. 3D printing as an additive manufacturing technology is capable of manufacturing multi-scale, multi-material, and multi-functional three-dimensional structures with ultra-high precision and ultra-high flexibility. This technology is expected to facilitate the integration of nanoencapsulated phase change materials (PCMs) for advanced multi-functional conceptual devices. The most popular nanoencapsulated composite PCMs are usually composed of nanoporous supporting materials and PCMs, thus guaranteeing their shape stability, leak-proof capability, and customizable thermal/electrical conductivity.1Chen X. Tang Z. Liu P. Gao H. Chang Y. Wang G. Smart utilization of multifunctional metal oxides in phase change materials.Matter. 2020; 3: 708-741Abstract Full Text Full Text PDF Scopus (48) Google Scholar,2Chen X. Gao H. Tang Z. Dong W. Li A. Wang G. Optimization strategies of composite phase change materials for thermal energy storage, transfer, conversion and utilization.Energy Environ. Sci. 2020; 13: 4498-4535Crossref Google Scholar Recently, nanoporous composite PCMs and related devices have been developing toward intelligence, multi-functionality, flexibility, and refinement. Specifically, composite PCMs with freely designed shapes and structures are definitely smarter in thermal energy management, wearable devices, and shape memory materials. However, the production of flexible lumped composite PCMs is still a big challenge because traditional manufacturing techniques are usually limited to post-impregnation strategies.3Aftab W. Huang X. Wu W. Liang Z. Mahmood A. Zou R. Nanoconfined phase change materials for thermal energy applications.Energy Environ. Sci. 2018; 11: 1392-1424Crossref Google Scholar,4Shchukina E.M. Graham M. Zheng Z. Shchukin D.G. Nanoencapsulation of phase change materials for advanced thermal energy storage systems.Chem. Soc. Rev. 2018; 47: 4156-4175Crossref PubMed Google Scholar Attractively, 3D printing strategies offer flexible solutions for complex and programmable composite PCMs. Different from traditional manufacturing methods, 3D printing can produce shape-changing composite PCMs without leakage, which is an important step toward the application of flexible devices. Direct ink writing (DIW) technology has widespread application prospects in 3D printing. Actually, designing viscoelastic inks with shear-thinning behavior is critical during the extrusion-based printing process.5Ma J. Ma T. Cheng J. Zhang J. 3D printable, recyclable and adjustable comb/bottlebrush phase change polysiloxane networks toward sustainable thermal energy storage.Energy Storage Mater. 2021; 39: 294-304Crossref Scopus (23) Google Scholar If the viscosity, surface tension, shear yield stress, shear elasticity, and loss modulus of the ink can be adjusted appropriately, direct printing of nanoencapsulated PCMs will be possible. Currently, numerous concentrated nanomaterial dispersions, such as graphene oxide and MXene, have been developed for DIW due to their extraordinary high viscoelasticity.6Zhang Y. Zhu G. Dong B. Wang F. Tang J. Stadler F.J. Yang G. Hong S. Xing F. Interfacial jamming reinforced Pickering emulgel for arbitrary architected nanocomposite with connected nanomaterial matrix.Nat. Commun. 2021; 12: 111Crossref Scopus (16) Google Scholar If PCMs are incorporated into the printable matrix (such as graphene oxide and MXene), the corresponding 3D-printed composite PCMs will shine in photothermal energy conversion and storage. More interestingly, the thermal performance of composite PCMs can be improved by optimizing the combination of nanomaterials and optimizing the printing geometry. For example, octadecane/graphene phase change microlattices with a bean pod structure can facilitate light propagation throughout the phase change microlattices, thus realizing the rapid collection and transfer of solar thermal energy.7Yang Z. Jia S. Niu Y. Lv X. Fu H. Zhang Y. Liu D. Wang B. Li Q. Bean-pod-inspired 3D-printed phase change microlattices for solar-thermal energy harvesting and storage.Small. 2021; 17: e2101093Crossref Scopus (18) Google Scholar Advanced building materials and infrastructure are benefiting from 3D printing technology. This technology provides a platform for facilitating the integration of nanoencapsulated PCMs in advanced phase change building materials. Advanced thermal management based on PCMs for passive control of building heating and cooling can reduce energy losses, which is of great strategic importance.8Song M. Niu F. Mao N. Hu Y. Deng S. Review on building energy performance improvement using phase change materials.Energy Build. 2018; 158: 776-793Crossref Scopus (231) Google Scholar Recently in Matter, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar creatively proposed a facile DIW technique to produce and print PCM-filled inks with excellent thermal regulation capacity that utilized spherical PCM particles as a viscosity modifier in a photocurable, leak-proof resin matrix. PCM beads were prepared by being emulsified at high temperature, dispersed in commercially available acrylate resins, printed, and cured with UV light. As shown in Figure 1A, the purposes of PCM beads were modifying ink rheology and imparting thermal management function. Photopolymerization realized the elastic sealing of PCMs without the use of shell materials. Based on this design concept, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar successfully printed inks (up to 63% PCMs) with excellent thermal regulation capacity and virtually no leakage during multiple melting and solidifying cycles. In addition, versatile PCMs with different phase transition temperatures (eicosane, paraffin, and hexatriacontane) can be simultaneously integrated into the resin and printed without compromising integrity. The rheological properties of the ink are critical in 3D printing. Specifically, Emily B. Pentzer et al.9Wei P. Cipriani C.E. Pentzer E.B. Thermal energy regulation with 3D printed polymer-phase change material composites.Matter. 2021; 4: 1975-1989Abstract Full Text Full Text PDF Scopus (19) Google Scholar conducted a preliminary evaluation of viscosity and yield stress of inks with different PCM loading levels for printability. Incorporating PCM beads into the resin imparted shear-thinning behavior, i.e., viscosity decreases with increasing shear rate. Generally, the increase filler concentration enhanced the viscosity, but had little influence on the magnitude of the shear-thinning behavior, indicating that inks can be formulated to attain optimal thixotropic behavior for DIW printing because the materials were sheared during the extrusion process. Increasing the loading level of PCM beads can strengthen the yield stress, which improves the ink’s ability to maintain its shape after extrusion. However, indiscriminately increasing the loading level of PCMs will cause the granular ink to fail to form a uniform paste. Therefore, an upper limit of the loading level of PCMs exists for printable compositions. As is well known, solid-liquid PCMs suffer from loss of integrity and volume change limitations during melting. The traditional solution is the microencapsulation of PCMs. Such rigid PCM microcapsules can be integrated into building materials to produce monolithic structures.10Zhu N. Li S. Hu P. Wei S. Deng R. Lei F. A review on applications of shape-stabilized phase change materials embedded in building enclosure in recent ten years.Sustain. Cities Soc. 2018; 43: 251-264Crossref Scopus (70) Google Scholar However, the shell materials have a negative impact on the thermal energy storage density. In this work, 3D printing technology harnesses the advantages of DIW and eliminates the inherent issues of current microencapsulation techniques (fluid leakage upon volume change) for facilitating the incorporation of PCMs into building materials, thus simplifying the manufacturing process. A limited temperature regulation range is another challenge of single PCMs. Since the ink formulation is not dependent on the chemical properties of PCMs, multiple PCMs can be simultaneously integrated into a single ink, allowing for a wider operating temperature window and promoting its thermal management capability. Ultimately, the authors 3D printed hollow house models with PCM-filled ink serving as effective thermal buffers in the melting temperature range of PCMs. Compared with houses without PCMs, 3D-printed PCM-based houses mitigated temperature fluctuations with a 10% lower temperature during heating and a 40% higher temperature during cooling (Figure 1B). This method does not require microencapsulation of PCMs before they are integrated into the composite materials, thereby using off-the-shelf structural materials to achieve effective passive thermal management and reducing the manufacturing costs. Generally, this study shows how to use 3D printing technology to encapsulate PCMs for thermal management of building materials. The excellent adaptability of DIW makes this strategy compatible with a wide range of photopolymer matrices and PCMs without prior microencapsulation of PCMs. 3D printing technology is capable of adjusting the loading levels of different PCMs particles to achieve the desired thermal management capability. However, the energy storage density of composite PCMs used for residential thermal regulation in this study needs to be further improved to boost the thermal regulation capability. Selecting appropriate PCMs is the key to the development of high-performance phase change building materials. Priority should be given to PCMs with suitable phase change temperature to reach the appropriate ambient temperature for human comfort, and to PCMs with larger latent heat to store or release more heat during the phase change process. Enhanced thermal conductivity, excellent reversibility, and small amounts of expansion and contraction should also be considered. In addition, the preparation process of phase change building materials should also be simplified. Future efforts should aim to balance the mechanical properties, thermal energy storage density, and practical engineering applications of phase change building materials, thus enabling design of advanced thermal management systems that satisfy commercial technical requirements. In conclusion, 3D printing technology offers the ability to produce objects with complex geometries, and it allows the integration of thermal energy storage materials into existing buildings. It is noteworthy that there are fewer reported applications of 3D printing for reliable and efficient thermal energy storage. Therefore, it is highly desirable to explore and implement a suitable combination of PCM encapsulation technology and 3D printing technology to simultaneously satisfy requirements for efficient thermal energy storage, scalable manufacturing, and leak-proof capability. The authors acknowledge funding from the National Natural Science Foundation of China (No. 51902025 ), Fundamental Research Funds for the Central Universities (No. 2019NTST29 ), and the China Postdoctoral Science Foundation (No. 2020T130060 and 2019M660520 ). Thermal energy regulation with 3D printed polymer-phase change material compositesWei et al.MatterApril 12, 2021In BriefIn the US, 20% of energy is consumed in the active thermal management of buildings. This work offers a solution by incorporating phase change materials (PCMs), which absorb and release heat at key temperatures, into 3D printable materials. 3D printing can reproduce complex architectural features, and the PCM-containing structures produced can minimize the energy used for thermal management of buildings. This work provides the potential to easily retrofit existing buildings and reduce the energy consumed in their thermal management. Full-Text PDF Open Archive

Study on the distributed model predictive control for multi-zone buildings in personalized heating

To meet demands of smart heating development, the novel dynamic regulation methods of heating systems need to be pursued. This paper presents a model predictive control (MPC) approach for room temperature regulation in multi-zone buildings. Among them, a) For heating systems with nonlinearity and large time delay, a hybrid optimization algorithm consisting of the improved particle swarm optimization (IPSO) algorithm and Newton-Raphson (NR) method in online optimization of MPC for a single zone building is proposed. Compared with the quadratic programming method, it can identify successfully the optimal control vector. b) A distributed MPC approach is presented for multi-zone buildings existing hydraulic coupling. Firstly, Nash-optimization acts on searching the global equilibrium point in the distributed structure, then the hybrid optimization algorithm works in the online optimization of these local MPCs. Compared with the decentralized MPC, the control performance is improved through co-operating and communicating between subsystems via network to share information related to their future behavior. Besides, the global performance index in the distributed MPC is redefined as the weighted sum of energy consumption and thermal comfort, which provides the possibility to eliminate quickly the most unfavorable thermodynamic loop in heating systems and reduce energy consumption.