Phase Change Material Candidate Research Articles

Development of a phase change material for vaccine transport without dry ice

AbstractCertain vaccines that have been developed against COVID‐19 require a storage temperature between around −60 and −70°C. It is challenging for logistics to assure these temperature limits. However, the use of dry ice has to be viewed critically for safety and environmental reasons. Additionally, its use is heavily regulated in air cargo. To preserve the cooling chain during transport and to increase the energy efficiency, special transport containers with an incorporated phase‐change material (PCM) can be used. In the first step, PCM candidates were investigated via differential scanning calorimetry (DSC) and in an ultra‐low freezer with a minimal temperature of −85°C. None of the candidates crystallised reliably without nucleating agents. After the initial tests, the eutectic LiBr·5H2O + H2O with a suitable nucleating agent was identified as favourite PCM. Thermal cycling stability tests showed that this PCM crystallises reliably above −80°C and possesses a melting plateau at −67°C. Further tests in vacuum‐insulated transport boxes of the company va‐Q‐tec show that, depending on the box type, the internal temperature stays below −60°C for over 48 h.

Selection and thermophysical assessment of phase change materials (PCMs) for space cooling applications in buildings

Phase change materials are gaining more attention in building comfort applications because of their latent heat thermal energy storage (TES) capacity. Identifying the best PCM candidate is a pivotal factor that significantly impacts the thermal performance of a building. This study delves into assessing prospective PCM candidates for potential utilization in cooling systems within buildings in hot subtropical climates. Extending the application of multicriteria decision-making (MCDM) methodologies, this research scrutinizes various commercial PCMs by conducting an exhaustive analysis of pertinent literature in the context of this specific application objective. Thermophysical properties are integrated into the MCDM framework to identify the most fitting candidates with optimal properties and attributes. The properties and attributes of PCMs are subjected to scoring and weighting through the AHP based on their significance in the given application context. TOPSIS and VIKOR techniques select the suitable PCM from the identified PCMs. The results showed that latent heat receives the highest weightage, amounting to 50.2%, due to its paramount importance. Furthermore, OM37 emerged as a promising choice for building space cooling, considering the prescreened temperature range of 30 °C–40 °C and for the specific location under consideration. Following PCM selection, thorough characterization was performed to evaluate the suitability of the chosen PCM for integration within building envelopes. The thermal conductivity of OM37 was determined to be 0.20 W/mK, while the morphology by a Field Emission Scanning Electron Microscope (Fe-SEM) intricate porous structure. Furthermore, a differential scanning calorimeter (DSC) suggests melting and solidification temperatures of 40 °C and 34 °C with a total enthalpy of 197.04 j/g, and a Thermogravimetry Differential Thermal Analysis (TG/DTA) showed a substantial weight loss of approximately 98.9% at around 247.3 °C. The presented experimental test results agree with the literature data and other researchers’ results.

Modeling and analysis of PCM‐encapsulated solar thermal energy storage system for space heating

AbstractIn this study, a phase change material (PCM)‐encapsulated packed‐bed thermal energy storage (PB‐TES) system is intended for Day‐round space heating in the winter. Solar concentric collectors act for day‐time heating and TES charging, while the stored energy can be used at night and intermediate time for space heating. A region‐wise techno‐economic analysis of PCM candidates is made to compare the costs and sizes of solar collectors and PB‐TES. A spherical capsule filled with sodium nitrite (NaNO2) and sodium nitrate (NaNO3) is numerically investigated during the PCM charging at constant thermal input. After complete liquefication, the charging time for NaNO2 and NaNO3 capsules is 3280 and 4300 s, respectively, holding the maximum stored energy of 733.4 KJ/kg at 285°C and 687.27 kJ/kg at 310.12°C, respectively. In addition, the stored exergy is obtained 238.78 and 234.74 kJ/kg for NaNO2 and NaNO3, respectively; however, the average exergetic effectiveness for NaNO2 and NaNO3 are 0.54 and 0.46. Despite the lower energy storage capacity (kJ/kg) of NaNO3, the PB‐TES volume is less with NaNO3 than with NaNO2 due to higher density. However, the average cost ($/tonne) of NaNO3 PCM is 50% higher than NaNO2. Subsequently, the thermal efficiency of the proposed system is estimated at 27.68% and 26.94% during day and night‐time operations.

Integrating multiple energy storage in 1D–2D bridged array carbon‐based phase change materials

AbstractIn response to global energy scarcity, frontiers in multifunctional composite phase change materials (PCMs) with photo‐/electro‐/magnetothermal triggers show great potential in multiple energy utilization. However, most available composite PCM candidates are inadequate for multiple energy storage applications simultaneously. Herein, a green synthetic route is proposed to develop bimetallic zeolitic imidazolate framework (ZIF)‐derived 1D–2D bridged array carbon‐based composite PCMs for simultaneous photo‐/electro‐/magnetothermal energy storage applications. As graphitization‐induced catalyst, Co nanoparticles greatly boost the formation of ZIF‐derived 1D–2D bridged array carbon framework with high graphitization and low interface electrical/thermal resistance. Benefiting from the broadband intense photon capture, fast photon/electron/phonon transport, and surface plasma resonance effect of Co nanoparticles, the resulting composite PCMs integrate advanced photo‐, electro‐, and magnetothermal storage functions. Furthermore, composite PCMs also exhibit long‐lasting shape stability, structural stability, thermal storage stability, and photo‐/electro‐/magnetothermal storage stability after undergoing multiple heating–cooling cycles. This study is promising to accelerate the major breakthroughs of advanced multifunctional carbon‐based composite PCMs toward multiple energy utilization.

Molecularly elongated phase change materials for mid-temperature solar-thermal energy storage and electric conversion

The utilization of phase change materials (PCMs) offers state-of-the-art thermal energy storage (TES) developments to overcome the intermittency issues associated with renewable energy sources. Despite the tremendous potential of renewable energy storage at intermediate temperature (100–200 °C), the PCM options for this temperature range are limited, and most available PCM candidates are inadequate for practical applications. Herein, we present a molecular elongation design strategy to develop a series of intermediate-temperature PCMs from naturally occurring fatty materials. By increasing chain length and imparting functional moieties in the molecular backbone, we fine-tune the intermolecular interactions in resulting PCMs to achieve more than two folds higher transition temperature compared with their monomeric analogs. Through a systematic structural analysis, we also probe the fundamental basis at the molecular level for the high TES capacity (up to 228 J g−1) that lies behind the excellent performance of our developed PCMs. Further, by compositing developed PCMs with photo-absorber scaffold, intermediate-temperature solar-thermal energy storage is demonstrated for dispatchable power generation. The prototype experimental results speculate that PCM integrated solar-thermoelectric generators could be an intriguing alternative to battery-coupled photovoltaic systems.

Continuous Dual-Scale Interpenetrating Network Carbon Foam-Stearic Acid Composite as a Shape-Stabilized Phase Change Material with a Desirable Synergistic Effect.

For enhancing the heat storage and encapsulation performances of organic phase change materials (PCMs), a carbon foam (CF) with a continuous dual-scale pore structure (DCF) was developed. Employing the as-prepared DCF as a stearic acid (SA) support, a novel shape-stabilized SA-CF composite PCM with a continuous dual-scale interpenetrating network structure was achieved through the impregnation of SA into the DCF. DCF-900, prepared at an activation temperature of 900 °C, possesses a high loading capacity of 89.54 wt % for melted SA without leakage. The resulting SA/DCF-900 composite with a continuous dual-scale interpenetrating network structure exhibits excellent comprehensive performances with a good synergistic effect. The composite presents a thermal conductivity of 1.298 W/m·K and an encouraging compressive strength of 9.03 MPa, which increase by 2.25-fold and 3.56-fold compared with those of DCF-900, respectively. Furthermore, its melting and freezing enthalpies reach 192.8 and 192.7 J/g with a storage efficiency of about 100%, respectively; meanwhile, it displays excellent thermal cycle stability and reversibility after 600 thermal cycles with a high melting/freezing enthalpy retention rate of up to 96%. More importantly, its light-to-thermal conversion efficiency reaches 91.8% under a light intensity of 100 mW/cm2. Consequently, the SA/DCF-900 composite is a promising candidate for high-performance PCMs.

Research Progress on the Phase Change Materials for Cold Thermal Energy Storage

Thermal energy storage based on phase change materials (PCMs) can improve the efficiency of energy utilization by eliminating the mismatch between energy supply and demand. It has become a hot research topic in recent years, especially for cold thermal energy storage (CTES), such as free cooling of buildings, food transportation, electronic cooling, telecommunications cooling, etc. This paper summarizes the latest research progress of the PCMs-based CTES. Firstly, the classification of PCMs for low temperature storage is introduced; the thermal physical properties (e.g., phase change temperature (PCT) and latent heat) of suitable PCM candidates (−97 to 30 °C) for CTES are summarized as well. Secondly, the techniques proposed to enhance the thermal properties of PCMs are presented, including the addition of nanomaterials, the microencapsulation and the shape stabilization. Finally, several representative applications (−97 to 65 °C) of PCMs in different CTES systems are discussed. The present review provides a comprehensive summary, systematical analysis, and comparison for the PCMs-based CTES systems, which can be helpful for the future development in this field.

Selection of phase change material suitable for building heating applications based on qualitative decision matrix

• QDM is applied to identify the best PCM candidate for building heating applications. • Related literature studies are extensively reviewed and analysed. • Tm, Hf, k, compatibility, flammability and cost of PCMs are considered. • Various scenarios are discussed, including and excluding the PCM cost. • RT28HC and PureTemp23 are the best candidates, with and without the cost, respectively. Phase change materials (PCMs) are successful thermal energy storage mediums in many thermal systems, including buildings. Identifying the best PCM candidate is a critical incorporation parameter that influences building thermal performance. This paper discusses the selection of potential PCM candidates that could be applied for building heating applications in cold locations. A qualitative decision matrix (QDM) is applied for several commercial PCMs after an extensive analysis of relevant literature studies. The melting temperature, heat of fusion, thermal conductivity, compatibility, flammability and cost of each PCM are considered in the QDM to find the most suitable candidates with the best effective properties and features. PCM properties/features are assigned with scores and weights in the QDM based on their importance for the application. Three scenarios are investigated in this work, including and excluding the PCM cost with varying and equal weights. Results showed that RT28HC had the highest score in all scenarios, followed by SavE®HS29 in the first scenario (when the cost is included) and PureTemp 32 in the second scenario without considering the cost. The methodology and results presented in this work are believed to be as efficient as logical for future studies compared with the traditional methods that rely on investigating the PCM thermo-physical properties.

Review and characterisation of high-temperature phase change material candidates between 500 C and 700°C

Latent heat thermal energy storage, by using phase change materials (PCMs), is considered as a promising technology that can be integrated into concentrated solar power (CSP) applications to mitigate the load and electricity supply. Multiple PCMs connected in series has attracted considerable research attention as this configuration has the potential to improve the thermal performance compared to single PCM storage. However, this technology has not yet been deployed in commercial CSP plants. One of the major restrictions is the lack of reliable thermophysical property data for high temperature PCMs. This study gives a broad review of the experimentally verified PCMs with melting temperatures from approximately 500 °C–700 °C, applicable to CSP systems. A further twelve PCM candidates, containing low-cost sodium and/or potassium salts, were identified in this study and their thermophysical properties were experimentally evaluated. It was found that nine of the new candidates can be used as PCMs.

Assessment of the Thermal Properties of Aromatic Esters as Novel Phase Change Materials

In the quest for a decarbonized energy system, the development of highly efficient technologies that allow the integration of renewables is of the utmost importance. Latent Heat Storage systems with Phase Change Materials (PCM) can contribute to solving the issue of the mismatch between demand and supply brought forward by renewable energies. Despite possessing promising thermal properties, organic PCMs and esters in particular have rarely been investigated. In the present study, eight commercial aromatic esters are assessed as possible PCM candidates. To do so, their thermal properties, such as phase change temperature, enthalpy of fusion, density, and thermal conductivity, alongside sustainability and toxicity issues, are considered. The aromatic esters are found to possess phase change temperatures between −16 ∘C and 190 ∘C and maximum enthalpies of fusion of 160 J/g. This, alongside densities above 1 g/mL, makes them interesting candidates for high-temperature applications, where, typically, salts and ceramics or metals dominate as PCMs.

Thermal performance of a PCM firefighting suit considering transient periods of fire exposure, post – fire exposure and resting phases

Firefighting scenarios may be characterized by various transient periods (i.e. phases), which consist of diverse environmental conditions. Firefighters usually encounter fire exposure, post fire exposure and resting phases. Development of new and improved protective clothing must be able to provide protection throughout all these phases, as burnouts may still occur after fire exposure due to accumulation of heat in the garment. The incorporation of phase change materials (PCMs) in firefighting garments has been shown to minimize the potential of heat hazards only during fire exposure. Thus to get more knowledge on their thermal performance, in the present study, the effect of PCM incorporation in post fire and resting phases were also numerically studied. The numerical code was validated for all phases. Five potential PCM candidates were considered. Exposure phases were characterized by high- medium and low- heat flux intensities (84, 12 and 5 kW∙m−2) with variable exposure times whilst post –exposure and resting phases where characterized by different wind speeds (i.e. ambient convective coefficients). Optimal PCM masses, times to second and third – degree burns as well as PCM suit cooling times were calculated to reflect thermal protective performance in each respective phase. The data generated allows for PCM short-listing from a set of potential PCM candidates along with its geometrical parameters, considering a wide range of characteristics of the various phases that consist a typical firefighting scenario.

Determination of optimal compositions and properties for phase change materials in a solar electric generating station

Thermal Energy Storage (TES) systems coupled to thermodynamic power cycles capable of generating electrical work are becoming strategic technologies of the future. The efficiency of TES fluids is a function of several thermodynamic and physical properties such as their heat capacity, latent enthalpy of melting and thermal conductivity. The stored thermal energy in these materials can be delivered to heat transfer fluids either by sensible heat or latent heat interactions. Challenges in the design of TES-based technologies are linked to the thermal stability and corrosivity of the selected heat storage fluid that needs to be encapsulated in metallic tubes/containers as well as the heat transfer efficiency. Latent heat storage materials, also known as Phase Change Materials (PCMs) offer high specific heat storage capacity and can operate at a constant temperature if their chemistry is adjusted so that they represent minima on liquidus surfaces. Working at a constant and minimal temperature is highly desirable from an engineering perspective as it limits corrosion degradation and temperature cycling stresses experienced by the container materials. Up to now, the identification of optimal PCMs has been mostly done via experimental trial-and-error based on limited amounts of thermodynamic data. Being able to theoretically identify PCM candidates and fine-tune their thermo-physical behavior would drastically improve their design. We present here an efficient tool specifically developed for the design of PCMs. This tool was used to identify 30 PCM candidates found in high-order anhydrous chloride-based salt systems that can operate at a temperature of 390±10∘ C.

Phase Change Materials for Nonvolatile, Solid‐State Reflective Displays: From New Structural Design Rules to Enhanced Color‐Changing Performance

AbstractWith the arrival of omnimedia era, there has been an increasing demand for energy‐saving, colorful, and portable displays. Traditional display technologies, such as electrophoresis and electronic ink display suffer from low color switching speed and poor color richness. Due to their high performances, phase change materials (PCMs)‐based nonvolatile, solid‐state reflective display coatings have become the most promising materials for new portable display technology. Existing researches mainly focus on improving the color‐changing performance of coatings by optimizing film structural parameters, but ignore improving the performance by designing new PCMs. Here, this study reveals the color‐changing mechanisms of display coatings through a combination of experiments, first‐principles calculations, spectral fitting, and optical simulation. It is found that reducing the vacancy concentrations of PCMs can increase the color‐changing performance of coatings owing to the increase in p–p coupling strength. Based on previous reports and the new insights into p–p coupling strength, this study proposes three structural design principles of ideal PCMs (low ionicity, a limited degree of hybridization, and high p–p coupling strength) and predicts new PCM candidates for display applications. This study opens a broad avenue for developing nonvolatile display technologies and material selection.

A lauric acid-hybridized bentonite composite phase-changing material for thermal energy storage.

In this study, a form-stable composite phase-changing material (PCM) was synthesised by a vacuum impregnation method. Natural Na-bentonite and lauric acid (LA) were used as the supporting material and PCM, respectively. In addition, flake graphite (FG) was used for enhancing the thermal conductivity of the form-stable composite PCM, besides for blocking the leakage of the PCM. Notably, with the addition of FG, the period of melting and freezing of the composite PCM decreased to a certain extend. Meanwhile, the heat-transfer characteristic of the composite increased. Moreover, the as-prepared form-stable composite PCM showed good thermal reliability after 200 cycles of thermal-cold treatment and has the potential to be used in thermal energy storage systems.

Acetamide for latent heat storage: Thermal stability and metal corrosivity with varying thermal cycles

Thermal stability and corrosion behavior of acetamide are studied using standard protocol in order to understand its feasibility as phase change material (PCM) for latent heat storage system. Maximum thermal stable temperature (110 °C) of acetamide as estimated by thermogravimetric analysis (TGA) indicates its prospect for several thermal storage applications including solar drying system. Differential scanning calorimetry (DSC) is used to evaluate the onset melting temperatures (107.62 °C), peak melting temperature (112.84 °C) and latent heat of fusion (210.21 J/g) of fresh acetamide as well as samples undergoing repeated heating and cooling (thermal cycles). Samples are collected and analysed at 100th thermal cycle interval up to 1000 thermal cycles to estimate relative percentage difference (RPD) of onset, peak melting temperatures and latent heat of fusion to understand the thermal stability of the selected PCM. Overall, RPD values are found within acceptable limit. Compatibility of acetamide with four metal surfaces (stainless steel, mild steel, aluminum and copper) are tested as a prospective container material through a series of standard corrosion resistance tests. The corrosion results suggest stainless steel and aluminum to be compatible with acetamide. Results indicated acetamide as a potential PCM candidate for mid-range (80–120 °C) temperature thermal energy storage application.

A molecular dynamics study of the effects of crystalline structure transition on the thermal conductivity of pentaerythritol as a solid-solid phase change material

A typical polyol that experiences solid-solid phase transitions, pentaerythritol (PE) has been proposed as a promising phase change material candidate for latent heat storage pertinent to the temperature range for industrial waste heat recovery. Upon increasing the temperature to over the solid-solid phase transition point (∼459 K), body-centered tetragonal crystalline structure of PE (α phase) is transformed into orientationally disordered face-centered cubic crystalline structure (γ phase). The thermal conductivity of PE at both α and γ phases is of great practical interest. In this work, the in situ X-ray diffraction and Fourier transformer infrared spectroscopy were used to characterize the crystalline structure transition of PE, in combination with the differential scanning calorimetry results. Molecular dynamics simulations were performed to elucidate the relationship between the thermal conductivity variation of PE and its crystalline structures at the atomic level. It was found that after the α-to-γ phase transition, the rearrangement and rotation of the OH···O bonds lead to indeterminate positions of the O and H atoms in the γ phase. The destruction and weakening of the hydrogen bonds can be the major change in the crystalline structures, leading to the reduction of the thermal conductivity of PE by a half after the α-to-γ phase transition.

Corrosion Assessment of Myo-Inositol Sugar Alcohol as a Phase Change Material in Storage Systems Connected to Fresnel Solar Plants.

Thermal energy storage systems work in conjunction with solar technologies with the aim of increasing their dispatchability and competitiveness in the energy market. Among others, latent heat thermal energy storage systems have become an appealing research subject and many efforts have therefore been invested in selecting the best phase change material (PCM) to fit the final application. In this study, an extended corrosion characterization was performed for two PCM candidates, solar salt (40 wt.% KNO3/60 wt.% NaNO3) and myo-inositol (C6H12O6), to be applied in Fresnel solar plants. Corrosion rates were determined in aluminium, stainless steel (AISI 304), carbon steel (AISI 1090), and copper by gravimetric tests, gauging the weight loss after 2000 h of immersion at 250 °C. The corrosion products were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The corrosion tests carried out with myo-inositol did not show accurate enough results to draw conclusions regarding corrosion on the metals. However, it was observed that this sugar alcohol strongly sticks to the metal specimens, making myo-inositol extremely difficult to manage as an energy storage material. Therefore, the present paper discourages the use of myo-inositol as a PCM beyond its corrosion rate.

Study on Thermal Properties of Bio-PCM Candidates in Comparison with Propylene Glycol and Salt Based PCM for sub-Zero Energy Storage Applications

Phase Change Materials (PCMs) provide a greater density of energy storage with a smaller temperature difference between storing and releasing heat compared to sensible heat storage methods. This paper reports results of study on bio-PCM made of vegetable oil ester and water mixtures. T-history thermal analysis method was implemented in determining thermal properties of the bio-PCM candidates. Comparison analysis was also performed in order to evaluate how favorable the investigated bio-PCM compared with conventional salt based PCM and propylene glycol. The study results showed that with right amount vegetable oil ester, the bio-PCMs can reduce freezing point and reduce or even eliminate super-cooling of water. On the other hand, salt based PCMs and propylene glycol showed high super-cooling and lower latent heat storage. This study has shown that the investigated water based bio-PCMs are strong PCM candidates for sub-zero energy storage applications.

Development of Corn-Oil Ester and Water Mixture Phase Change Materials for Food Refrigeration Applications

This research aims to investigate development of corn-oil ester and water mixtures as novel solid-liquid phase change material candidates for chilled and frozen food refrigeration applications. Thermal properties of both water and its mixture with corn-oil ester were tested by DSC and T-history methods. The results showed that corn oil could mix well in water solutions. Phase transition temperatures of the mixtures were lower than those of individual water. Corn-oil ester in the mixtures was acted as a nucleate agent and it was able to lower freezing point and to trigger ice nucleation in water which could diminish super-cooling. Addition of corn oil ester by 5% to 35% in water solutions could decrease freezing temperature from 0°C down to respectively -3.5°C to -28°C. The PCM candidates were also found to have excellent thermal properties that could fulfill requirements of thermal energy storage systems for food refrigeration applications.

Operation of a Latching, Low-Loss, Wideband Microwave Phase-Change Switch Below 1 K

We report on the design, fabrication, and demonstration of the operation of a latching (nonvolatile) low-loss microwave switch at 4.2 K and 40 mK using the phase-change material germanium telluride (GeTe) as the switching element. The single-pole double-throw (SPDT) series–shunt switch has a single RF input and two selectable RF outputs. An insertion loss of less than 1 dB from DC to 10 GHz was demonstrated, with virtually identical performance across 5000 switching cycles at 40 mK. We have also characterized the resistance of the GeTe thin-film material used in the fabrication of the SPDT switch from room temperature down to 11 mK. While bulk GeTe is known to become superconducting below 1 K, these GeTe films showed no detectable superconducting transition, resulting in a switch with finite on-state DC resistance. Given the wide range of phase-change material candidates reported in the literature and prior evidence of superconductivity, this demonstration paves the way for future development of a near-ideal switch which could have zero on-state DC resistance at cryogenic temperatures.