Suitable Phase Change Material Research Articles

Enhancing energy efficiency of PCM wall in winter with novel PCM-DLCB coupling design

In order to enhance the thermal performance of the phase change material (PCM) wall during winter, a novel PCM and double-layer capillary bundles (PCM-DLCB) coupling wall is proposed. The PCM-DLCB wall utilizes the capillary bundle near the outer surface to capture solar energy during sunny winter days. The heat is then transferred to the capillary bundle near the inner surface through a circulating pump, promoting the melting of the PCM. Optimization and long-term operation comparison research were conducted using numerical simulation to investigate the potential of the PCM-DLCB wall to improve energy efficiency during winter. Five structural parameters, including the type of PCM, the position of the capillary bundle, the position and thickness of the PCM layer, the spacing of the capillary bundles, and the flow velocity in the capillary bundle, were selected as variables for structural and operation optimization. The optimization target was the accumulated heat gain from the inner surface of the wall. The research results indicate that: (1) The most suitable PCM is RT-18HC; (2) Placing the PCM layer between the double-layer capillary bundle yields better results compared to other arrangements; (3) Optimal energy saving is achieved when the outer capillary bundle is positioned 6 mm away from the outer surface and the inner capillary bundle is positioned 8 mm away from the inner surface; (4) The optimal thickness of the PCM layer is 10 mm; (5) The optimal flow velocity in the capillary bundle is approximately 0.04 m/s. Furthermore, long-term operation results based on a typical hot summer and cold winter climate zone reveal that the optimized PCM-DLCB wall provides a 7.80 % increase in indoor heat gain compared to an ordinary PCM wall during winter, and an 18.4 % increase compared to a wall without PCM.

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

Optimization of temperature distribution in building envelopes of Ahmedabad region using nano-encapsulated phase change material

The incorporation of Phase Change Materials (PCM) into the building envelopes helps to increase indoor thermal comfort while lowering energy usage. The selection of PCM is directly related to its performance and might be viewed as an optimization challenge. The manuscript highlights the optimization of temperature distribution in building envelopes (walls and roofs) of Ahmedabad by choosing the suitable PCM and Nano-particle. Three different PCMs (RT31, RT 35, and RT42) and Nano-particles (Al2O3, CuO, and ZnO) with different concentrations (12 %, 16 %, and 20 %) are considered for the optimization. The PCMs are encapsulated into the building layer thickness to examine their characteristics like effective thermal conductivity, concentration, melting point, etc. These parameters are evaluated in a room that measures 5 m x 4 m x 3.5 m (L x W x H). The design-builder software (Version 7.0.2.006) is used to carry out the steady-state numerical simulations for this building envelope. The results suggest that the integration of PCM reduces the building's overall energy consumption by 7.92 kWh/m2 per year. The optimal design is proposed by establishing a temperature difference (ΔT) in building envelopes and utilizing a hybrid optimization technique (a combination of Artificial neural network (ANN) and Genetic algorithm (GA)). This temperature difference of the building envelope is confirmed to be dependent on their PCM melting point, effective thermal conductivity, concentration (in%), and PCM layer thickness. Hybrid optimization is found to be the most stable strategy for predicting temperature dilation and energy storage in building envelopes. Thus this paper gives a systematic understanding of the selection of PCM and Nano-particles and identifies the suitable PCM layer thickness for encapsulation.

Charge Assessment for Nitrate-Based Salt as a Phase Change Material for a Medium-Temperature Latent Storage Tank

Abstract The present study assesses the heat characteristic of the nitrate-salt mixture as a phase change material (PCM) for a medium-temperature latent storage system (LSS). Two binary and ternary mixtures are evaluated, which demonstrate different thermal behaviour. The highest melting and latent heat capacity is obtained by KNO3(0.4)/NaNO3(0.6) at 223.8 °C and 161.5 J/g. However, it has a higher supercooling degree with a partial phase transition between 217.6 °C and 251.5 °C, making it unfeasible for a medium-temperature LSS tank. The ternary mixture (TM) with NaNO2(0.4)/KNO2(0.53)/NaNO3(0.7) demonstrates a stable phase transition with minimum partial phase transition (22.1 °C) and suitable heat of fusion (98.1 J/g). Further evaluation through static thermal profiling demonstrates that the TM has a notable performance during solid-sensible charge with a charge level indicator (CLI) around 45.3 %–49.1 %. The TM can be charged up to 85.7 % until the end stage of the phase transition. It promotes a better storage capacity with suitable performance since the system can be charged effectively at a suitable temperature range (< 160 °C) for various applications. The micrograph observation indicates some dispersed particles and local agglomeration, which makes phase stabilization as an advantageous method to promote a stable phase change process. The TM can be considered a suitable PCM for a medium-temperature LSS tank that allows for a better solar thermal renewable system operation.

Optimization study on thermal performance of a novel dynamic phase change material wall

A new concept of dynamic phase change material (PCM) wall structure in building envelope is proposed to enhance the passive solar energy utilization, in which PCM wall position could be exchanged with insulation layer. The thermal performance of phase change materials in buildings is related to many factors. To ensure that the novel dynamic PCM wall structure could reach its full potential, the thermal performance of the structure was numerically simulated and optimized based on different climatic conditions, room sizes and the position of PCM layer in the wall. The results indicated that the suitable PCM was different when using the novel dynamic PCM wall in different climates. Among the four cities of Harbin, Tianjin, Jinan and Guangzhou, northern cities, like Tianjin, were more suitable for using PCM A16 than southern cities. In terms of room size design, when the volume of the room remained identical, the room size design formed a certain correlation with the indoor temperature. In addition, results showed that the location of the novel PCM wall system in the wall would cause a great difference in indoor temperature, which was related to heat dissipation at different locations.

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.

Enhanced performance of photovoltaic thermal module and solar thermal flat plate collector connected in series through integration with phase change materials: A comparative study

The decline in photovoltaic cell efficiency due to temperature elevation, coupled with solar energy's inherent intermittency, presents challenges for solar systems, including photovoltaic panels and solar thermal (ST) collectors. The integration of phase change materials (PCMs) emerges as a promising solution to enhance thermal energy storage and regulation, thereby improving system performance and sustainability. This study investigates the performance of series-connected photovoltaic thermal (PVT) and ST systems with integrated PCMs from energy and exergy viewpoints, utilizing a 3D transient numerical simulation. The proposed system's performance is compared with that lacking a PCM across various heat transfer fluid mass flow rates. Suitable PCM selection based on melting temperature is explored, along with PCM layer thickness and nanoparticle augmentation. The research highlights that PCM integration effectively regulates PV cell temperature, enhancing electrical power and exergy rate. While increasing the mass flow rate improves thermal and electrical power, it reduces the thermal exergy rate. Comparing different PCMs (RT28 HC, RT35 HC, and RT44 HC), the RT28 HC PCM provides the lowest temperature of PV cells and the best electrical performance during the day. Moreover, increasing PCM layer thickness results in lowering PV cell and outlet temperatures and storing more heat. Nanoparticles added to PCMs lead to a marginal improvement in energy and exergy, especially for the system with RT28 HC. This analysis emphasizes PCM integration's role in enhancing solar thermal system performance, highlighting the importance of considering the PCM's melting temperature for effective thermal energy management.

Thermo Physical Properties Based Parametric Analysis To Help PCM Selection

Thermo Physical Properties Based Parametric Analysis To Help PCM Selection

Parametric study of an active-passive system for cooling application in buildings improved with free cooling for enhanced solidification

The present study introduces an active-passive system (APS) with phase change material (PCM) integrated into the substructure of the internal walls and ceiling for cooling. To ensure sufficient cooling effect of the system during the daytime cycle, the system must solidify completely during the nighttime cycle and operation costs comparable to the ones of conventional cooling systems. An air gap was formed between the primary wall and ceiling and the PCM substructure and ventilated with the cool outdoor air during the nighttime cycle. A parametric study was performed using ANSYS Fluent followed by the energy performance and operation cost analysis. Different inlet air temperature scenarios (15–20 °C) were tested (suitable PCM thermal characteristics). The required solidification-time of PCM was determined. The model is validated against the experimental tests. The results show that with the current configuration, the PCM plates can be sufficiently solidified at supply air temperatures of 17 °C and below. If the system is ventilated with inlet air temperatures above 17 °C, additional cooling options must be considered. The study also determines the energy performance of the system under the chosen conditions and compares its feasibility to the conventional cooling systems (energy efficiency class A+++ and G air-conditioning device).

Evaluating the impacts of fin structures and fin counts on photovoltaic panels integrated with phase change material

Metal fins synergized with phase change materials (PCMs) provide good thermal management for photovoltaic (PV) panels, and the performances largely depend on the shapes and counts of the fins, and the layouts of the cavity. This work first compares the thermal behaviors of one fractal fin or one straight fin in the cavity with height H (mm)-width W (mm) of 80-75, 100-60, 120-50, 150-40, and 200-30, respectively. The results show that one fractal fin can accelerate the PCM melting and further lower the PV temperature by 2 °C than one straight fin. Moreover, a more desirable cavity with the dimension of 120-50 is clarified by comparing the PV panels average efficiency during 0∼180 min versus the energy input. Next, comparisons of the fin counts N = 1, 2, 3, and 4 reveal that raising the fin count N to 2 reduces the PV panel temperature by 2.3 °C, and the fin counts cause most of the difference. Ultimately, a suitable PCM thickness of 40 mm is selected by considering the PV panel temperature along with the weight and cost of the systems. This study aims to promote the development of finned PV panels integrated with PCMs.

Simulation of photothermal building and thermal comfort analysis of PMV

Nowadays, with the development of technology and the improvement of human economic level, the energy consumption of buildings is gradually increasing. China is very rich in solar energy resources and the development of solar buildings can save a lot of energy by taking advantage of solar energy resources. The Trombe Wall to be studied in this paper are passive solar buildings. Trombe Wall can achieve good indoor natural ventilation and can meet the requirements of human thermal comfort. However, solar energy is unstable and intermittent, which can easily lead to excessive fluctuations in indoor temperature, so the use of suitable phase change or energy storage materials is also a very important measure. In this paper the mathematical model corresponding to Trombe Wall is specifically investigated and simulations are carried out using COMSOL Multiphysics software to verify the thermal characteristics of Trombe Wall at different temperatures in a given room and the natural ventilation effect they achieve. The simulations are followed by a PMV thermal comfort analysis of the room. The analysis is carried out for four scenarios: “Summer - day”, “Summer - night”, “Winter - day” and “Winter - night”, thus enabling the analysis of Trombe Wall at different temperatures.

Melting and solidification analysis of paraffin phase change material in a circular space, molecular dynamics simulation

The increasing use of renewable energy sources has led to more studies in the field of eliminating the weaknesses of these sources. The use of energy storage systems is one of these things that increase the sustainability of renewable resources and reduce the share of fossil fuel resources in daily energy consumption. One of the most important things in heat storage systems is the use of suitable phase change materials (PCM). In this research, the behavior of paraffin, as a well-known PCM, is investigated on a molecular scale. For this purpose, an annular space has been selected as a nanochannel and the behavior of this material inside it has been investigated in different states. First, the thermal performance of this PCM is investigated. Then, the effect of its temperature on index parameters such as viscosity, heat flux, thermal conductivity, charge time, discharge time, and phase change time are evaluated. The research results show that increasing initial temperature (from 300 K to 350 K) improves the performance of PCM (the duration of charging and discharging are increased from 1.78 and 2.15 ns to 1.41 and 2.24 ns, respectively.). In addition, increasing the speed of the material also reduces the charging and discharging time to 1.65 and 2.09 ns, respectively. Increasing the diameter ratios also changes the indicator times to 2.18 and 2.03 ns, respectively.

Design and selection of suitable sustainable phase change materials for latent heat thermal energy storage system using data-driven machine learning models

Design and selection of suitable sustainable phase change materials for latent heat thermal energy storage system using data-driven machine learning models

The impact of thermal aging on the degradation of technical parameter of a dynamic latent thermal storage system

A dynamic latent thermal storage (DLTS) system operates at elevated working temperatures to maximize the operation of the thermal system. It potentially deteriorates the phase change material (PCM) after specific cycles due to thermal aging. The present work assesses the impact of thermal aging of wax-based PCM (paraffin and beeswax) toward the technical parameter of a DLTS system. After thermal aging treatment, the charge and discharge performance for both PCM are degraded. The discharge rate of beeswax (BW) decreases by 23.2%, reducing the effective power rate and storage efficiency by more than 50%. The aged paraffin wax (PW) also experiences performance degradation, where the discharge and power rates decrease around 14.7% and 18.7%, respectively. However, the aged PW maintains sufficient efficiency (67.2%) compared to BW (41.1%), implying that the aging effect can vary for different PCM. Surface observation for the aged PCM demonstrates a fracture profile and microvoids which are probably affected by thermal stress that leads to physical deformation at the molecular level. The decomposition curve is also changed for the aged PCM, making thermal stability an important parameter in choosing a suitable PCM for long-term operation. The study demonstrates the urgency to consider suitable PCM and adjustment on the operation protocol of the DLTS system after a certain cycle operation to minimize the degradation of performance parameters of the thermal system.

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.

Modelling and optimization of phase change materials (PCM)-based passive cooling of solar PV panels in multi climate conditions

To address the increasing energy demand, replacing conventional energy systems with non-conventional resources like solar power generation is crucial. Photovoltaic (PV) panels play a significant role in harnessing solar energy and converting it into electrical power. However, the solar cells’ temperature dramatically influences the panel’s performance, particularly in hot climates. In this study, a detailed mathematical model is developed and conducted simulations using three different phase change materials (PCMs)—RT21, RT35, and RT44—integrated with PV panels in various climate conditions worldwide during the summer season. An optimization model is also created using MATLAB and a genetic algorithm to identify the most suitable PCM for specific climate zones. The findings revealed that incorporating PCM resulted in a surface temperature reduction of PV panels, leading to a 6% increase in efficiency and a 16% boost in electrical output. Specifically, when using a PCM with a melting point of 21°C, the maximum cell temperature during summer operation decreased from 65°C to 38°C. Similar temperature reductions were observed when using PCMs with melting points of 35°C and 44°C. Current analysis demonstrates that the correct selection of a phase change material can decrease panel temperature by approximately 39% in June. Furthermore, PCM with a melting point of 21°C exhibited the best outcomes in terms of maximum electrical performance, efficiency, and PV cell temperature reduction.

Experimental investigation in the selection of phase change materials based on thermal stratification effect in thermal energy storage system

AbstractThis study aims to evaluate the effects of thermal stratification on thermal energy storage (TES) systems during the charging process and choose suitable phase change materials (PCMs) for various layers. The research revealed that fiberglass insulation of 60 mm thick significantly decreased natural convection losses and increased the TES system's potential for energy recovery. For constant heat load, the charging time increased with increasing HTF inlet temperature, but remained constant for the first TES layer at a specified flow rate, resulting in increased storage capacity with minimal heat loss to the surroundings. The solar collector efficiency was shown to be dependent on solar radiation and collector efficiency, with peak efficiency seen at specified periods. The lowest melting point of PCMs at each layer 68°C, 62.7°C, 57°C, and 50°C was chosen based on temperature graphs. For comparing stratification behavior, the “MIX” number versus non‐dimensional charging time plot was effective. Additional experiments are needed to assess the selected PCMs' charging and discharging properties.

Annual Thermal Management of the Photovoltaic Module to Enhance Electrical Power and Efficiency Using Heat Batteries

Several studies state that phase change material (PCM) improves the electrical power and efficiency of the photovoltaic (PV) module. To find the suitable PCM for tropical climatic conditions, multi-PCMs are examined simultaneously with melting temperatures of 31 °C, 35 °C, 37 °C, and 42 °C. In this study, PCM containers are integrated behind the PV module with a thickness of 50 mm. The performance of the multi PV-PCMs is monitored year-round and compared with PV-noPCM. The experimental results show that the selected four PCMs performed the cooling process autonomously in all the climates, such as PCM with a melting temperature of 37 °C and 42 °C enhanced the higher cooling rate in summer, and the same PCMs failed to achieve a higher cooling rate in winter. The lowest temperature drop was noted for pre-monsoon and monsoon seasons due to the low irradiance. On the other hand, the highest temperature drop of 16.33 °C is observed for pre-summer (March) and 15.7 °C, and 17.14 °C for summer (April) as compared to PV-noPCM. The results of the present investigation highlight the requirement for choosing the proper PCM melting temperature based on optimal year-round performance. Further, it is recommended that a single PCM melting temperature for cooling the PV modules year-round in tropical climates is inappropriate, and instead, a cascaded structure with different PCM melting temperatures is recommended.

Exergoeconomic and exergoenvironmental based multi-criteria optimization of a new geothermal district heating system integrated with thermal energy storage driven heat pump

In this study, a new geothermal district heating system, which includes a heat pump (HP) system driven by thermal energy storage (TES) unit, was optimized throughout the multi-criteria decision making analysis named efficiency analysis technique with output satisficing (EATWOS). In this regard, the objective functions were chosen as exergoeconomic and exergoenvironmental indicators varying with the handled designs. 111 different designs formed considering different working parameters and fluids in this aim. Three environment-friendly refrigerants according to their thermal behaviour (wet, dry, and isentropic types) and suitable phase change materials (PCM) according to the design conditions were evaluated. The designed system was evaluated by energy, exergy, exergoeconomic, and exergoenvironmental tools to determine the objective functions. As conclusion, Case 108 with the refrigerant of R1234ze and PCM of RT70HC was determined as the best design. The sustainability index, exergoeconomic factor, exergoenvironmental factor, relative cost, and relative exergoenvironmental impact of this optimal case were determined as 1.24, 0.002583%, 0.0540%, 460.85%, and 649.50%, respectively. For this case, the energy and exergy efficiencies of the system were determined as 74.56% and 19.17%, respectively. In comparison to conventional system, a decrease of 38.86% in relative exergoeconomic cost (r) and a decrease of 19.21% in the relative exergoenvironmental impact (rb) were achieved.

Effect of Phase Change Materials on the Optical Path of LEDs for Opto-Thermal Enhancement

A novel concept based on the encapsulation of transparent phase change materials (PCMs) into the optical packaging structure of light-emitting diodes (LEDs) is presented in this article. The concept was initiated by challenges of thermal management of photoluminescent particles in high-power optical systems. LEDs, white LEDs (WLEDs), and porous/network-based photoluminescent matrices can achieve improved thermal networks by embedding PCMs. In this article, paraffin is selected as a suitable PCM encapsulant, and aside from thermal perspectives, an unexpected optical benefit with melted paraffin after surface wetting of the chip was observed. Immersing an LED chip in a melted paraffin pool showed up to an 8% increase in light extraction efficiency and a 1.5% increase in power conversion efficiency (PCE). An accurate dynamic opto-electro-thermal monitoring of studied devices was used to support the proof of concept. This viable method can be integrated into current industrial packaging processes.