Optimal Phase Change Material Research Articles

PCM as an energy flexibility asset: How design and operation can be optimized for heating in residential buildings?

In cold climates, residential buildings are often well-insulated to reduce heating costs but may lead to overheating. Incorporating Phase Change Material (PCM) into building envelope can serve as an effective measure to mitigate overheating and reduce cooling costs. However, the inappropriate incorporation of PCM in well-insulated building envelope might negatively affect the heating energy flexibility. Therefore, this paper explores the effectiveness of PCM in reducing heating costs by optimizing the PCM design and heating operation. The main objectives are to (i) quantify the performance of PCM in terms of overheating and cost savings, aligned with the recently introduced Time-of-Use (ToU) tariff and Spot pricing, (ii) identify the optimal design of PCM-incorporated building envelope, and (iii) apply a smart control with resetting temperature setpoints in-line with EN-ISO 52120-1 Standard. A multi-stage optimization process has been designed. It first identifies the optimal properties (i.e., melting temperature), position, and thickness of PCM. Secondly, it optimizes the profile of temperature setpoints, considering the seasonal thermal behavior of PCM. Co-simulation platform between IDA ICE 5.0 and Python 3.8 optimization engine is created for the heating control optimization. Results showed that PCM is more effective when incorporated into the interiors of external walls rather than in roofs. The optimal PCM design for Nordic buildings, featuring 75 mm-thick PCM with a melting temperature of 21 °C positioned within walls’ interior, has a varied impact on monthly energy savings across seasons, with a negative effect in spring and a significant positive effect in autumn. After the multi-stage optimization, the optimal scenario enables to achieve a maximum annual cost savings of 6.5 % with ToU tariff and 21.0 % with Spot pricing, while also eliminating overheating.

Simulation study of a novel phase change cooling garment for electricians in a high-temperature environment

To mitigate the effects of heat stress on electricians during outdoor activities such as inspection, circuit repair, and daily maintenance in high-temperature environments, a novel design for a portable, efficient, and ergonomic phase change cooling garment is presented. First, the optimal phase change material is selected considering economic and environmental factors. Then, based on the heat balance equation of the human body and Fourier's law, the required phase change material mass and the optimal thickness of the retarded heat-absorbing layer are obtained and verified by numerical simulations and experiments. The results indicate that in a high-temperature environment of 38 °C for 2 h, electricians require 2.39 kg of phase change material. To meet the protective duration requirements of electricians' daily tasks, the optimal thickness of the phase change material is 8 mm, and the optimal thickness of the slow-release heat absorption layer is 3 mm. The results of this study have significant implications for the safety and protection of electricians in high-temperature environments. It aims to provide theoretical guidance for the design and innovation of personal cooling garments for electricians.

A novel design of lithium-polymer pouch battery pack with passive thermal management for electric vehicles

This study investigates the thermal characteristics of a lithium polymer pouch battery thermal management system using phase change material (PCM) during the discharge. The research provides a detailed discussion of various factors influencing the system. The novelty aspect of this study involves evaluating thermal changes in the battery at 40 °C through hot soaking experiments comparing with both PCM-integrated modules and without PCM modules. The study further aims to identify the optimal PCM for both normal and high ambient conditions. Thermal parameters, including maximum temperature Tmax, average temperature Taverage and thermal gradient ΔT were evaluated at 25 °C and hot soaking performance at 40 °C temperature during discharge was analysed. Simulation were conducted to compare module behavior, especially at high-temperature conditions. Furthermore, a thorough examination of PCM melting and solid-phase transitions at high temperatures were performed that significantly impact the cooling performance of the PCM system. Our findings reveal that expanded graphite PCMs offers effective thermal performance with observed improvement of 27 %. Therefore, we recommend employing EG26 and EG28 PCMs for real-world application electric vehicle battery pack systems.

Experimental study on the thermal protection enhancement of novel phase change material integrated structural firefighting gloves under high-heat exposures

Phase change material (PCM) has been widely studied for efficient thermal management. This work is the first holistic experimental research on the temperature control performance of PCM-integrated firefighters' gloves. The results showed that the thermal protection time could be extended by 2-5 times in the direct contact to hot object tests and around 1.5 times under the radiant/convective heat source tests when embedding a 1-mm-thick PCM layer in gloves. The PCM of melting point 68 °C showed the best thermal protection performance in all test conditions since it had the most efficient phase change function during the heating process. Considering the PCM location effect, the PCM with lower melting point (68 °C) showed better performance when located close to external environment (heat source) and the PCM with higher melting point (108 °C and 151 °C) showed better performance when located close to hand. The optimum PCM thickness would be in the range of 0.5-1.0 mm for both thermal protection improvement and hand dexterity purposes. In addition, the time for continuous temperature rises on the hand surface at post-heat exposure was longer when embedding PCM in firefighters’ gloves due to the stored latent heat in PCM.

Thermal performance of an active casing pipe macro-encapsulated PCM wall for space cooling and heating of residential building in hot summer and cold winter region in China

Phase change material (PCM) wall is expected to match the building type and its climate region effectively. In order to meet the space cooling and heating of residential buildings in hot summer and cold winter regions in China, a new active casing pipe macro-encapsulated PCM wall is proposed, in which the cold storage and heat storage PCMs are sealed between the inner pipe and outer pipe with no leakage. To obtain the optimal structure parameters and better thermal performance of the PCM wall, the mathematical model of the PCM wall is established and validated by experiment, and the effects of PCM filling pattern, structural parameter of casing pipe, water temperature in inner pipe and indoor setting temperature are simulated and analyzed. The results show that the optimal PCM filling pattern is to fill the cold storage PCM and heat storage PCM in the gap between the inner pipe and outer pipe separately; the optimal PCM filling thickness is 13 mm; the optimal structural parameters are inner pipe diameter of 20 mm and casing pipe centre spacing of 61 mm. The water temperature in the inner pipe and PCM energy storage/release time reasonably match the indoor setting temperature. Under the optimal operating conditions, the average PCM wall surface temperatures of 20.5 and 26.8 ℃ and the PCM wall surface heat fluxes of 45.9 and 57.2 W/m2 can be obtained in summer and winter conditions, respectively. The research provides an optimized casing pipe macro-encapsulated PCM wall system that can reliably and efficiently meet both the space heating and cooling demands of residential buildings in hot summer and cold winter regions in China.

A Numerical Study to Improve the Efficiency of Solar Collector used for water heating using Phase Change Material

Solar water heaters are an effective technology for harnessing renewable solar energy to provide hot water for households and businesses. However, their efficiency can be impacted by factors like intermittent sunshine, heat losses, and low radiation intensity. The aim of this study is to increase the efficiency of solar water heaters through the use of phase change materials (PCMs). PCMs have the ability to store latent heat during phase change, releasing it later when needed. This study uses numerical simulations to analyze the effect of integrating different PCMs into a flat plate solar collector design. The findings could then be validated experimentally and applied to improve the real-world performance of solar water heating systems. The PCMs are placed inside the collector to absorb heat during the day and release it after sunset to continue heating the water. The research seeks to determine the optimal PCM properties, structure, and placement within the collector to maximize heat storage and transfer. The efficiency and performance of the solar collector system with different PCM configurations have been compared to those of a conventional collector without PCM. The outcomes uncover that the use of suitable PCMs can significantly improve the efficiency and heat output of the solar collector, especially during periods of low radiation and after sunset. The optimal PCM configuration maintains higher water temperatures for longer, allowing solar water heating to continue into the evening. The results may provide valuable insights for using PCMs to boost the efficiency of solar thermal technologies

Design and optimization of a hybrid cooling configuration combining PCM and liquid cooling for Li-ion battery using data-based response surface approximation model

Effective thermal management is crucial for safe operation of electric vehicles. This study proposes a novel hybrid cooling system that using phase change material (PCM) and liquid cooling to address issues such as leakage, non-uniform temperatures under high discharge rates. A comprehensive 3D model was developed to analyze the influence of geometric parameters on the cooling system. Response surface approximation modeling was used to optimize the layout parameters of the PCM. The results show that the hybrid cooling outperforms other methods, maintaining the cell temperature with 35 ℃ and the temperature difference within 4 ℃. The thickness of the PCM is a significant factor, as it increases heat storage capacity and reduces temperature; however, exceeding a certain threshold leads to increased thermal resistance. A non-uniform PCM layout can reduce the temperature difference by 26 %. An optimal PCM thickness of 2.5 mm to 3 mm ensures that the maximum temperature remains below 32.5 ℃, with a temperature difference within 2 ℃. The lowest temperature difference is achieved with a vertical layout height of 70 mm and a horizontal layout thickness of 3 mm. These findings are valuable for enhancing the thermal management of lithium-ion battery.

Preparation, characterisation and property modification of a calcium chloride hexahydrate phase change material slurry with additives for thermal energy transportation

Efficient thermal energy distribution and rational energy management are effective solutions to address the significant and fast-ascending energy consumption in building heating, ventilation, and air conditioning (HVAC). Phase change material (PCM) slurries with excellent thermal energy transportation and storage characteristics have been recognised as promising secondary refrigerants to simultaneously facilitate efficient heat/cold transport and effective thermal energy storage in air conditioning systems. Among various PCM slurries, salt hydrate PCM slurries have attracted increasing attention in recent years due to their many inherent advantages. This paper presented the preparation, characterisation, and property modification of a CaCl2·6H2O slurry based on a methodology proposed for optimal salt hydrate PCM slurry development. Theoretical modelling was first carried out to assess the availability of salt hydrate PCM slurries based on the phase diagram and solid fraction, followed by a series of property measurements to reveal the mechanisms and address the problems behind the phase transition, crystal particle morphology, stability and rheologic characteristics, using nucleating agents, surfactants and stabilisers. It was found that the salt hydrate PCM slurry developed provides a unit volume enthalpy twice that of water over the phase change temperature range of 5°C, together with acceptable fluidity. The results also showed that the PCM particle size can be well controlled, and the slurry can be stabilised, with the assistance of surfactants and stabilisers. Compared to other types of PCM slurries, the proposed salt hydrate PCM slurry has the advantages of being cost-effectiveness, easy preparation, adjustable phase change temperature, etc., which is promising to facilitate energy saving and rationalisation in building HVAC.

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In high-energy-demand regions, such as the Arctic, the building sector is focused on reducing the carbon footprint and mitigating environmental impact. To achieve this, phase change materials (PCMs) are being investigated for thermal energy storage due to their high latent heat of fusion. However, their limited applications arise from poor thermal conductivity. In addressing this issue, the research delves into the preparation and characterization of nano-PCMs. These materials, synthesized in a laboratory setting, exhibit enhanced thermal performance compared to pure PCMs, attributed to the incorporation of nanoparticles in the material composition. Therefore, in the study, three paraffins with different melting temperatures (10, 15 and 18 °C) are modified by incorporating titanium oxide at various concentrations (0.05, 0.1, 0.2 and 0.5 mass%). Thermal conductivity and latent heat capacity measurements were undertaken using a thermal conductivity measuring apparatus and differential scanning calorimetry, respectively. The aim was to evaluate the enhanced performance of the modified PCMs in comparison with pure PCMs and to assess their suitability for cold climate regions. Results showed that nanoparticle incorporation increased thermal conductivity by up to 37%, albeit with a slight reduction in latent heat capacity of up to 12%. Among the samples, RT18 exhibited the most significant improvement in thermal conductivity, while RT10 experienced a minor decrease in enthalpy values. Ultimately, RT10 was identified as the optimal PCM option for cold climates, as its phase change temperature range aligns with the outdoor temperatures in the Arctic.

Mathematical model of the solar combined cycle power plant using phase change materials in thermal energy storage system (Thermodynamic analysis)

This research presents a novel mathematical framework for optimizing solar combined cycle power plants, with a particular emphasis on the exergy analysis of various superheating heat exchanger configurations used in thermal energy storage. The importance of phase change materials (PCMs) in improving the thermodynamic efficiency of solar combined cycle power plants is emphasized in this study. The investigation includes three configurations, two with a single PCM and one with two PCMs. The use of PCMs is intended to increase storage density, reduce volume, and maintain consistent temperatures, thereby favoring latent energy storage. The model developed evaluates exergy efficiency and output temperature profiles during the charging and discharging processes. The results show that the single PCM configuration has an impressive charging efficiency of 93.12 %, reaching an output temperature of 371 °C in 8 h. The two PCM configurations, on the other hand, achieve even higher efficiency at 94.89 % during charging, with an output temperature of 367 °C over a slightly longer 10-hour period. This comparison emphasizes the benefits of using two PCMs, demonstrating increased exergy efficiency and a marginal increase in output temperature over a single PCM setup. Furthermore, a comparison of the outcomes resulting from the use of a single type of PCM in exchangers reveals that the disparity in PCM melting temperatures causes only minor variations in the system's efficiency. The findings emphasize the significance of optimal PCM utilization for efficient solar energy retention, particularly during periods of low radiation.

Hybrid (Optimal) Selection Model for Phase Change Materials Used in the Cold Energy Storage of Air Conditioning Systems

The latent heat storage of phase change materials (PCMs) can be used in refrigeration and air conditioning systems. Storing cool energy during the nighttime (off-peak hours) and releasing the cool energy during the daytime (on-peak hours) to reduce the number of starts of the chiller and pumps is a practical approach for achieving energy saving and carbon reduction. Therefore, selecting PCMs is vital for improving energy efficiency and preventing future energy shortages. However, selecting PCMs is complicated by their unique characteristics and types. The purpose of this study was to establish a PCM selection model by combining the Delphi, analytic hierarchy process (AHP), and VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) methods to select the optimal PCM type applied in cold storage. A numerical example was used to verify the model’s usability, confirming that A9 is the optimal PCM for the cold storage of an air conditioning system. This three-stage PCM selection model combining the Delphi, AHP, and VIKOR approaches provides a more suitable selection model and considers the selection method of material criteria. Moreover, it can solve the problem of difficult PCM selection. Simultaneously, it considers mechanisms to incorporate a company’s primary considerations into material selection for real-world applications. These results can facilitate material evaluation and selection during system design and material qualification, helping companies achieve the goals of energy saving, carbon reduction, and sustainable management in the future.

Preferred method and performance evaluation of heterogeneous composite phase change material (CPCM) wallboard in different seasons

The application of phase change materials (PCMs) in building envelopes has been developed in past decades and many strategies have been adopted to improve the heat resistance and capacity performance. However, rare studies focused on optimizing these characteristics of PCM wallboard in different seasons and providing preferred method for selecting the optimal PCMs. This study constructed a heterogeneous wall acting in different seasons and developed a pre-screening method of PCMs based on the analytic hierarchy process. CA-HD/EG with higher thermal conductivity (2.16 W/(m·K)) and lower melting point (25.4 °C) acted as the inner layer, and paraffin/porous silica with lower thermal conductivity (0.37 W/(m·K)) and higher melting point (29.3 °C) acted as the outer layer. Two experimental boxes were built to compare the thermal performance of CPCM and gypsum wallboard. The decrement factor in winter increased by 6.7 %, and the heat storage coefficient in summer increased by 0.97. The thermal comfort duration in winter was extended by 17.9 %, and the thermal load leveling in summer was reduced by 11.5 %. The heating/cooling water supply duration was shortened by 2.5 h, resulting in an energy-saving rate of 13.3 %. Consequently, the CPCM wallboard maintained a better indoor thermal environment with a lower energy consumption.

Efficient energy generation and thermal storage in a photovoltaic thermal system partially covered by solar cells and integrated with organic phase change materials

To address the limitations of conventional photovoltaic thermal systems (i.e., low thermal power, thermal exergy, and heat transfer fluid outlet temperature), this study proposes a photovoltaic thermal system with a solar thermal collector enhancer (PVT-STE), incorporating phase change materials for simultaneous electricity and thermal power generation and thermal energy storage. The system consists of a water based solar collector with a partially covered absorber plate utilizing photovoltaic cells, while each component is equipped with a thermal storage enclosure filled with phase change materials. The primary objectives of this research encompass the evaluation of the proposed system's performance and the identification of appropriate phase change materials for each component. To gain comprehensive insight into the effects of employing and selecting appropriate phase change materials, the study investigates various configurations under both hot and cold weather conditions of Shanghai, China. Water serves as the heat transfer fluid under real-world operational conditions. The numerical results indicate that, for the given conditions, optimal phase change material selection entails using higher melting temperatures (e.g., RT42) in the STE component and lower melting temperatures (e.g., RT31) in the PVT component. Employing the optimal phase change materials for each component, the system can store 3234 and 1802 kJ/m2 of thermal energy during the charging process in July and November, respectively. Moreover, the proposed system generates almost 1.8 and 2 times more thermal energy per square meter in July and November, respectively, compared to a standalone photovoltaic thermal system coupled with a phase change material.

Exploring the temperature-dependent thermal stability of nano-enhanced phase change materials: An experimental study using eicosane as the base material

Recently, studying phase change materials (PCMs) has brought many researchers' attention to be applied in thermal energy storage and battery thermal management (BTM) applications. Nano-materials have been used recently to improve the advantages of the PCM which makes them suitable materials to be used in thermal management systems. Moreover, the selection of the nanomaterials and the proper concentration of nano-particles in PCM affects the thermophysical characteristics of PCM. According to the fact that PCM requires to be thermally stable, the principal aim of this study is to analyze the thermal stability of PCMs composites by loading different mass fractions of CuO nano-particles. In order to add nano-particles to the eicosane-based PCM, a two-step method has been used. The thermal stability of the Nano-enhanced phase change materials (NePCM) has been measured by using the thermogravimetric analyzer. Results demonstrated that 0.5 wt% is the best value of additive nano-particle which showed a remarkable increment in thermal stability. Therefore, all the presented results indicate the importance of selecting an optimal PCM nano-composite for various applications including NePCM-based thermal energy storage and BTM systems. The brand and model of the device used in this study are Hitachi and STA7000 respectively.

Advancements in Phase Change Materials in Asphalt Pavements for Mitigation of Urban Heat Island Effect: Bibliometric Analysis and Systematic Review.

This research presents a dual-pronged bibliometric and systematic review of the integration of phase change materials (PCM) in asphalt pavements to counteract the urban heat island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably, Chang'an University in China has emerged as a leading contributor. The systematic review addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM leakage prevention in asphalt, and effects on mechanical properties. The findings identify polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCM due to their wide phase-change temperature range and significant enthalpy during phase transitions. While including PCM can modify asphalt's mechanical attributes, such mixtures typically stay within performance norms. This review emphasises the potential of PCM in urban heat management and the need for further research to achieve optimal thermal and mechanical balance.

Novel indicators to evaluate PCM performance under different ventilation strategies by considering the impact of climate change

Due to climate change, the cooling energy demand in the building sector is projected to increase significantly. According to International Energy Agency, for a sustainable future, energy-efficient technology should be implemented in buildings. The potential of Phase change materials (PCM) for reducing building energy consumption has been widely acknowledged by researchers. However, the selection of appropriate PCM and its latent heat exploitation is crucial when PCM is integrated into the building envelope. This research evaluates the implementation of PCM for building cooling energy savings (CES) with climate change in thirty-nine cities located in 13 different zones of the future Koppen-Geiger climate map. Novel performance indicators, energy charging, and discharging coefficients are presented, to evaluate the PCM performance based on the exact latent heat exploitation. A range of PCMs (PCM 18–32) were assessed by coupling PCM with free night ventilation and changeover ventilation using the hybrid downscaled weather files for 2095. The results showed that the optimum PCM varied from PCM27 to PCM30 resulting in substantial CES (1214 kWh-7240 kWh) in all zones except Cfb, Dfa, and Dfb under the indoor HVAC controlled conditions. In natural ventilation conditions, combining PCM with free night ventilation increased CES up to 2490 kWh compared to night ventilation alone, while combining PCM with changeover ventilation, reduced energy consumption by up to 2772 kWh compared to changeover ventilation alone. Overall, free night ventilation with PCM improved the CES by up to a maximum of 35% while changeover ventilation in combination with PCM further increased the CES by up to 96% and appeared to be the best strategy for maximizing the CES in all climate zones.

A Review of Recent Improvements, Developments, Effects, and Challenges on Using Phase-Change Materials in Concrete for Thermal Energy Storage and Release

Most concrete employs organic phase change materials (PCMs), although there are different types available for more specialised use. Organic PCMs are the material of choice for concrete due to their greater heat of fusion and lower cost in comparison to other PCMs. Phase transition materials are an example of latent heat storage materials (LHSMs) that may store or release thermal energy at certain temperatures. A phase transition occurs when a solid material changes from a solid state to a liquid state and back again when heat is added or removed. It is common knowledge that adding anything to concrete, including PCMs, will affect its performance. The goal of this review is to detail the ways in which PCMs affect certain concrete features. This overview also looks into the current challenges connected with employing PCMs in concrete. The review demonstrates a number of important findings along with the possible benefits that may pave the way for more research and broader applications of PCMs in construction. More importantly, it has been elucidated that the optimum PCM integrated percentage of 40% has doubled the quantity of thermal energy stored and released in concrete. Compared to conventional concrete, the macro-encapsulated PCMs showed thermal dependability, chemical compatibility, and thermal stability due to delaying temperature peaks. Furthermore, the maximum indoor temperature decreases by 1.85 °C and 3.76 °C in the test room due to the addition of 15% and 30% PCM composite, respectively. Last but not least, incorporating microencapsulated PCM has shown a positive effect on preventing freeze-thaw damage to concrete roads.

Thermal performance analysis of concentric-tube latent heat storage systems integrated with varying energy source under various charging strategies

This study presents a comprehensive assessment of the performance of a vertical concentric tube thermal storage system. The system is charged using constant and variable solar energy sources similar to real-world conditions. The initial part of the work focuses on identifying the suitable optimal phase change material for maximizing energy storage. It later evaluates the impact of using a variable energy source compared to a constant source for charging the system. A performance assessment of the system is carried out for two approximated constant energy source cases (constant time-averaged and constant peak fluid temperatures) and an actual variable energy source (unsteady fluid temperature). The findings indicate that constant time-averaged and peak charging temperatures can lead to under-prediction by up to 25.65 % and over-prediction by up to 32.72 % in the energy storage compared to the actual case considering variable charging temperature. Two charging strategies are proposed and compared with the established cascade methodology, revealing the potential for improving thermal energy storage. The dynamic charging strategy shows promising results with potential energy storage gains of up to 55.57 %. This study emphasizes the importance of considering the variable charging source and highlights effective strategies for enhancing energy storage in the thermal storage systems.

An optimisation study of PCM triple glazing for temperate climatic conditions – Dynamic analysis of thermal performance

PCM-windows can play an important role in the protection of buildings against overheating but also as systems for effective storage of solar energy. The presented study indicated the optimal solution for the triple-glazed window where one cavity is fullfilled with phase change material (PCM) in temperate climatic conditions characteristic for Poland. Regarding different thicknesses, positions, and temperatures of phase change material, the a recommended solution was determined using the simulation technique. The computational model was developed, numerically verified, and experimentally validated. The entire meteorological year analyses were done for the climatic conditions of Central Europe, considering windows exposed to facing the South. The optimal solution was determined using two methods - the Weighted Sum method and the Fuzzy Sets method. Both point out a variant with a PCM layer located in the inner cavity and the average melting temperature of PCM equal to 25 °C. However, different criteria and sets of linguistic variables in fuzzy sets determined different optimal PCM thicknesses ranging from 5 to 20 mm.

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

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